Combustion in spark ignition engines can occur via homogeneous or heterogeneous mixtures. In a homogeneous mixture, combustion occurs in three stages: an initial delay period, a flame propagation period where pressure rises rapidly, and a final quenching period. Factors that influence the flame speed include turbulence, fuel-air ratio, temperature/pressure, compression ratio, engine output, and engine speed. Abnormal combustion in the form of knock or surface ignition can damage the engine and cause noise. Knock occurs when end gases autoignite, while surface ignition initiates at hot spots. Various engine variables like temperature, compression ratio, and spark timing can affect knocking.
5.2 combustion and combustion chamber for si enginesFasilMelese
The document discusses combustion and combustion chambers in spark ignition engines. It describes the conditions needed for combustion, the different types of fuel-air mixtures, and the stages of combustion in a homogeneous mixture. The three stages of actual engine combustion are the delay period, flame propagation, and wall quenching. Factors that influence flame speed like turbulence, fuel-air ratio, temperature and pressure are also summarized. Abnormal combustion phenomena of knock and surface ignition are described along with causes of end gas combustion and the effects of various engine variables on knocking.
The document discusses combustion in compression ignition (CI) engines. It describes the four stages of combustion in CI engines: (1) ignition delay period, (2) uncontrolled combustion, (3) controlled combustion, and (4) after burning. It explains that the ignition delay period allows fuel to accumulate, causing uncontrolled combustion and a steep pressure rise when ignition occurs. Controlled combustion then follows, where combustion is matched to the fuel injection rate.
The document discusses combustion in internal combustion engines. It covers:
1) The normal combustion process in spark ignition engines including the 3 stages of combustion and factors affecting flame speed.
2) The combustion process in compression ignition engines including the 4 stages and factors affecting the ignition delay period.
3) Abnormal combustion phenomena like knock and types of abnormal combustion in diesel engines.
A century and nearly two decades later there has been immense progress in the field of IC engines, though many phenomenon taking place are still to be understood physically. This blog aims at comprehension of some of the astonishing research that has been done in this field restricting our interest to combustion with some amusing facts.
This document discusses combustion and fuel characteristics in internal combustion engines. It covers topics such as combustion process terms like normal combustion and abnormal combustion. It also discusses spark knock, surface ignition, ignition delay, combustion requirements, air-fuel ratios, ignition timing, and advance timing. The goal is to understand the combustion process in spark ignition and compression ignition engines as well as the phenomenon of knocking.
The combustion process in a compression ignition (CI) engine occurs differently than in a spark ignition engine. In a CI engine, the air-fuel mixture is not homogeneous since the liquid fuel remains in particle form. Combustion takes place simultaneously at many points as the liquid fuel is evaporated, mixed with air, and raised to its ignition temperature. There are four stages of combustion in a CI engine: 1) an ignition delay period as the fuel is injected and begins to chemically react, 2) a premixed burning phase of maximum heat release, 3) a mixing-controlled combustion phase where fuel burns as it is injected, and 4) a tail/afterburning region where remaining unburned fuel continues burning into the
In a compression ignition (C.I.) engine, combustion occurs due to the high temperatures achieved during compression stroke. A minimum compression ratio of 12 is required, with typical ratios between 14-17. During the intake stroke, air is drawn into the cylinder. In the compression stroke, the rising piston compresses the air and increases its temperature. Near top of compression, fuel is injected and ignites instantly due to the hot air. As fuel burns, hot gas expands and drives the piston down. On the exhaust stroke, burned gases are pushed out. Combustion occurs in three stages - ignition delay period, rapid uncontrolled combustion, and controlled combustion. Abnormal combustion like diesel knock can occur if ignition delay is too long.
The document summarizes the combustion process in internal combustion engines. It discusses four stages of combustion: 1) ignition delay period, where fuel is transformed into vapor and mixed with air before ignition; 2) uncontrolled combustion, where accumulated fuel burns rapidly once ignition begins; 3) controlled combustion, where the combustion rate matches the fuel injection rate; and 4) after burning of residual fuel. Factors like injection timing and fuel properties affect the ignition delay period. The combustion chamber design must provide efficient fuel-air mixing and heat distribution to achieve smooth combustion.
5.2 combustion and combustion chamber for si enginesFasilMelese
The document discusses combustion and combustion chambers in spark ignition engines. It describes the conditions needed for combustion, the different types of fuel-air mixtures, and the stages of combustion in a homogeneous mixture. The three stages of actual engine combustion are the delay period, flame propagation, and wall quenching. Factors that influence flame speed like turbulence, fuel-air ratio, temperature and pressure are also summarized. Abnormal combustion phenomena of knock and surface ignition are described along with causes of end gas combustion and the effects of various engine variables on knocking.
The document discusses combustion in compression ignition (CI) engines. It describes the four stages of combustion in CI engines: (1) ignition delay period, (2) uncontrolled combustion, (3) controlled combustion, and (4) after burning. It explains that the ignition delay period allows fuel to accumulate, causing uncontrolled combustion and a steep pressure rise when ignition occurs. Controlled combustion then follows, where combustion is matched to the fuel injection rate.
The document discusses combustion in internal combustion engines. It covers:
1) The normal combustion process in spark ignition engines including the 3 stages of combustion and factors affecting flame speed.
2) The combustion process in compression ignition engines including the 4 stages and factors affecting the ignition delay period.
3) Abnormal combustion phenomena like knock and types of abnormal combustion in diesel engines.
A century and nearly two decades later there has been immense progress in the field of IC engines, though many phenomenon taking place are still to be understood physically. This blog aims at comprehension of some of the astonishing research that has been done in this field restricting our interest to combustion with some amusing facts.
This document discusses combustion and fuel characteristics in internal combustion engines. It covers topics such as combustion process terms like normal combustion and abnormal combustion. It also discusses spark knock, surface ignition, ignition delay, combustion requirements, air-fuel ratios, ignition timing, and advance timing. The goal is to understand the combustion process in spark ignition and compression ignition engines as well as the phenomenon of knocking.
The combustion process in a compression ignition (CI) engine occurs differently than in a spark ignition engine. In a CI engine, the air-fuel mixture is not homogeneous since the liquid fuel remains in particle form. Combustion takes place simultaneously at many points as the liquid fuel is evaporated, mixed with air, and raised to its ignition temperature. There are four stages of combustion in a CI engine: 1) an ignition delay period as the fuel is injected and begins to chemically react, 2) a premixed burning phase of maximum heat release, 3) a mixing-controlled combustion phase where fuel burns as it is injected, and 4) a tail/afterburning region where remaining unburned fuel continues burning into the
In a compression ignition (C.I.) engine, combustion occurs due to the high temperatures achieved during compression stroke. A minimum compression ratio of 12 is required, with typical ratios between 14-17. During the intake stroke, air is drawn into the cylinder. In the compression stroke, the rising piston compresses the air and increases its temperature. Near top of compression, fuel is injected and ignites instantly due to the hot air. As fuel burns, hot gas expands and drives the piston down. On the exhaust stroke, burned gases are pushed out. Combustion occurs in three stages - ignition delay period, rapid uncontrolled combustion, and controlled combustion. Abnormal combustion like diesel knock can occur if ignition delay is too long.
The document summarizes the combustion process in internal combustion engines. It discusses four stages of combustion: 1) ignition delay period, where fuel is transformed into vapor and mixed with air before ignition; 2) uncontrolled combustion, where accumulated fuel burns rapidly once ignition begins; 3) controlled combustion, where the combustion rate matches the fuel injection rate; and 4) after burning of residual fuel. Factors like injection timing and fuel properties affect the ignition delay period. The combustion chamber design must provide efficient fuel-air mixing and heat distribution to achieve smooth combustion.
The document discusses fuel injection and spray formation in diesel engines. It examines the effects of injection pressure on engine performance and emissions. The results of an experiment showed that brake thermal efficiency peaked at an injection pressure of 200 bars, while brake specific fuel consumption was lowest. CO and smoke emissions decreased with higher injection pressure, while UHC first decreased and then increased as pressure became too high. Optimal injection pressure was found to be 200 bars for a 20% biodiesel blend. Cavitation in the fuel injector nozzle enhances spray atomization and improves combustion. Nozzle geometry and injection conditions can affect cavitation.
The document provides information on combustion in compression ignition (CI) engines. It discusses various topics such as:
1. The stages of combustion in CI engines including ignition delay period, uncontrolled combustion, controlled combustion, and afterburning. Ignition delay depends on factors like temperature, fuel quality, and compression ratio.
2. Diesel knock (detonation) which produces a clanking sound from rapid combustion. It can be controlled by using better fuel, controlling fuel supply rate, and increasing swirl.
3. Different types of combustion chambers in CI engines including direct injection, indirect injection, pre-combustion chamber, swirl chamber, and air-cell chamber.
4. F
Combustion in an SI engine occurs in three stages:
1. The ignition lag stage is the delay between the spark and noticeable pressure rise from combustion. This allows the fuel-air mixture to heat up to its self-ignition temperature.
2. In the flame propagation stage, the flame front travels across the combustion chamber, releasing energy and increasing pressure.
3. The afterburning stage finishes combusting any remaining unburnt fuel-air mixture after the flame front passes.
Combustion in diesel engines occurs in three phases: 1) the ignition delay phase, 2) the premixed combustion phase, and 3) the mixing-controlled combustion phase. The ignition delay phase determines the rate of pressure rise and peak pressure/temperature, affecting noise and NOx emissions. Premixed combustion involves fuel-air mixtures at the stoichiometric ratio, producing high pressure/temperature rises and NOx. Mixing-controlled combustion depends on fuel-air mixing rates, with combustion along rich, stoichiometric, and lean paths. Heat release rate diagrams show an initial high rate corresponding to the premixed phase, followed by a gradually decreasing rate in the main release period.
The document discusses combustion in diesel engines. It describes the four stages of combustion: ignition delay period, rapid combustion period, controlled combustion period, and after-burning period. It explains factors that affect the ignition delay period such as compression ratio, engine speed, fuel quality, and intake conditions. The document also discusses knock in diesel engines and different combustion chamber designs for diesel engines, including direct injection and indirect injection types.
1. Combustion involves the rapid chemical combination of fuel and oxygen, resulting in heat release. It requires a combustible mixture, an ignition source, and flame propagation.
2. In spark ignition (SI) engines, a carburetor supplies an air-fuel mixture and a spark plug ignites it. Combustion in SI engines occurs in three stages: ignition lag, flame propagation, and afterburning.
3. Factors like air-fuel ratio, compression ratio, load, turbulence, and engine speed affect the flame propagation rate in SI engines. Higher propagation speeds improve efficiency and fuel economy.
The document discusses combustion in spark-ignition (SI) engines. It defines combustion as a chemical reaction in which fuel combines with oxygen, liberating heat energy. In an SI engine, fuel and air are mixed and inducted into the cylinder where combustion is initiated by a spark at the spark plug near the end of the compression stroke. There are three stages of combustion: ignition lag, flame propagation, and after burning. Abnormal combustion phenomena like pre-ignition and knocking can occur if conditions are not suitable. Factors like turbulence, fuel-air ratio, temperature and pressure, compression ratio, and engine variables affect the flame speed and combustion process.
Detonation occurs when the combustion process moves too quickly in an engine cylinder, causing abnormally high pressure and temperatures. This happens if fuel ignites before the scheduled ignition of the spark plug. Detonation can damage engine components and is caused by factors like improper ignition timing, a lean air-fuel mixture, low octane fuel, and high exhaust back pressure. Engines can be protected from detonation by using higher octane fuel, retarding the ignition timing, cooling the air charge, and ensuring a proper fuel supply. Pre-ignition is a related issue where the fuel ignites prematurely due to hot spots in the combustion chamber rather than the spark plug.
This document outlines the syllabus for an advanced internal combustion engines course. The course is divided into 5 units that cover topics such as: carburetion and combustion in spark ignition engines; compression ignition engines; engine exhaust emission control; alternate fuels; and recent engine technologies. Unit 1 discusses the air-fuel ratio requirements for spark ignition engines, carburetor design and operation, combustion stages, knock factors, and thermodynamic analysis of the combustion process.
The document discusses the design requirements of combustion chambers in spark ignition engines. It states that good combustion chambers aim to provide high power output, efficiency, smooth operation and low emissions. Key design considerations include high compression ratios, turbulence, compact size, and valve and spark plug placement. Historically, T-head, L-head, and I-head (overhead valve) designs have been used, with overhead valve becoming prevalent for its performance at high compression ratios. Modern combustion chamber designs include bath tub and wedge types within cylinder heads.
This document discusses spark ignition engines. It covers air-fuel ratio requirements, the stages of combustion including normal and abnormal combustion, factors that affect knocking, and combustion chambers. Knocking occurs when pockets of the air-fuel mixture explode outside of the normal combustion front, disrupting the precise ignition timing. Factors that influence knocking include density, time, and fuel composition. The design of the combustion chamber aims to provide smooth engine operation and high power output through efficient combustion.
The document summarizes combustion in compression ignition (CI) engines. It describes how combustion occurs simultaneously in many spots in a non-homogeneous fuel-air mixture, controlled by fuel injection timing. The four stages of CI engine combustion are ignition delay, premixed combustion, mixing-controlled combustion, and late combustion. Factors like injection timing and fuel quality can affect the ignition delay period. Knock may occur if ignition delay is too long. The document provides diagrams to illustrate CI engine combustion processes and types.
This document discusses combustion in internal combustion engines. It begins by defining combustion as the rapid chemical combination of fuel and oxygen that releases energy in the form of heat. It then describes the different types of combustion that can occur, including complete and incomplete combustion. The document focuses on the combustion processes in spark-ignition (SI) engines and compression-ignition (CI) engines. For SI engines, it describes the typical three stages of combustion: ignition lag, flame propagation, and afterburning. For CI engines, it outlines the four phases of combustion: ignition delay period, uncontrolled combustion, controlled combustion, and afterburning. Key factors that influence combustion in each engine type are also summarized.
The combustion chamber burns a mixture of air and fuel inside jet engines, maintaining stable combustion over a wide range of operating conditions while minimizing pressure loss and distributing the heated exhaust gases uniformly to the turbine. Different combustion chamber designs are used depending on requirements, employing features like recirculation zones, cooling air, and multiple fuel injectors to efficiently combust the air-fuel mixture under varying operating conditions.
Ci engine combustion by Akhileshwar NiralaAkhilesh Roy
In a compression ignition (CI) engine, fuel is directly injected into the cylinder and spontaneously ignites when mixed with hot, compressed air. Combustion occurs in four stages: ignition delay, premixed combustion, mixing-controlled combustion, and late combustion. There are two main types of CI engines - direct injection engines which inject fuel directly into the chamber, and indirect injection engines which inject fuel into a prechamber before entering the main chamber. Factors like injection timing and quantity, intake conditions, and fuel properties can affect the ignition delay period.
This presentation was prepared by Mechanical Engineering professor Dr. Shahid Imran during their lecture with final year in their Internal Combustion Engine program offered at University of Engineering and Technology Lahore.
This document discusses various types of fuel injection systems for spark ignition and compression ignition engines. It describes the different stages of combustion in diesel engines including ignition delay, rapid combustion, mixing controlled combustion, and late combustion. It also discusses factors that affect combustion like temperature, pressure, composition, and design of the combustion chamber. The document outlines different types of diesel fuel injection systems including mechanical and electronic systems. It describes the purpose and workings of fuel injection pumps, nozzles, and catalytic converters.
Fundamentals of Compression Ignition EngineAnand Kumar
This document provides an overview of fundamentals of compression ignition engines. It begins with classifications of engines based on physical state of mixture and ignition type. It then discusses engine components, the diesel cycle, combustion processes, abnormal combustion, and developments to improve emissions such as common rail direct injection and exhaust gas recirculation. The goal is to introduce key concepts regarding compression ignition engines including working, thermodynamics and developments to control emissions.
The document discusses the stages of combustion in a compression ignition (diesel) engine. It describes four stages: 1) ignition delay period, where fuel is injected and mixes with air before igniting; 2) rapid uncontrolled combustion, where ignition occurs rapidly across the cylinder; 3) mixing-controlled combustion phase, where combustion is controlled by fuel injection rate and mixing; 4) late combustion or afterburning phase, where any remaining fuel continues burning slowly through the expansion stroke. The document explains the physical and chemical processes that occur during each stage.
The document provides explanations of various components of internal combustion engines including connecting rods, crankshafts, piston rings, glow plugs and camshafts. It also lists differences between SI and CI engines and discusses factors that affect engine performance such as compression ratio, thermal efficiency, valve timing and residual gas fraction.
The document discusses combustion in spark-ignition (SI) engines. It defines combustion as a chemical reaction in which fuel combines with oxygen, liberating heat energy. In an SI engine, fuel and air are mixed and inducted into the cylinder where combustion is initiated by a spark at the spark plug near the end of the compression stroke. The combustion process occurs in three stages: ignition lag, flame propagation, and after burning. Abnormal combustion phenomena like pre-ignition and knocking can occur if conditions are not suitable. Factors like turbulence, fuel-air ratio, temperature and pressure, compression ratio, and engine speed and size can affect the flame speed and combustion characteristics in the engine.
Combustion in a SI engine involves three stages:
1. Flame development stage where the spark ignites the fuel-air mixture and a flame nucleus forms.
2. Flame propagation stage where the flame spreads through the combustion chamber. The flame propagation speed affects combustion efficiency.
3. Flame termination stage where combustion continues after peak pressure is reached if a rich fuel mixture is supplied.
The document discusses fuel injection and spray formation in diesel engines. It examines the effects of injection pressure on engine performance and emissions. The results of an experiment showed that brake thermal efficiency peaked at an injection pressure of 200 bars, while brake specific fuel consumption was lowest. CO and smoke emissions decreased with higher injection pressure, while UHC first decreased and then increased as pressure became too high. Optimal injection pressure was found to be 200 bars for a 20% biodiesel blend. Cavitation in the fuel injector nozzle enhances spray atomization and improves combustion. Nozzle geometry and injection conditions can affect cavitation.
The document provides information on combustion in compression ignition (CI) engines. It discusses various topics such as:
1. The stages of combustion in CI engines including ignition delay period, uncontrolled combustion, controlled combustion, and afterburning. Ignition delay depends on factors like temperature, fuel quality, and compression ratio.
2. Diesel knock (detonation) which produces a clanking sound from rapid combustion. It can be controlled by using better fuel, controlling fuel supply rate, and increasing swirl.
3. Different types of combustion chambers in CI engines including direct injection, indirect injection, pre-combustion chamber, swirl chamber, and air-cell chamber.
4. F
Combustion in an SI engine occurs in three stages:
1. The ignition lag stage is the delay between the spark and noticeable pressure rise from combustion. This allows the fuel-air mixture to heat up to its self-ignition temperature.
2. In the flame propagation stage, the flame front travels across the combustion chamber, releasing energy and increasing pressure.
3. The afterburning stage finishes combusting any remaining unburnt fuel-air mixture after the flame front passes.
Combustion in diesel engines occurs in three phases: 1) the ignition delay phase, 2) the premixed combustion phase, and 3) the mixing-controlled combustion phase. The ignition delay phase determines the rate of pressure rise and peak pressure/temperature, affecting noise and NOx emissions. Premixed combustion involves fuel-air mixtures at the stoichiometric ratio, producing high pressure/temperature rises and NOx. Mixing-controlled combustion depends on fuel-air mixing rates, with combustion along rich, stoichiometric, and lean paths. Heat release rate diagrams show an initial high rate corresponding to the premixed phase, followed by a gradually decreasing rate in the main release period.
The document discusses combustion in diesel engines. It describes the four stages of combustion: ignition delay period, rapid combustion period, controlled combustion period, and after-burning period. It explains factors that affect the ignition delay period such as compression ratio, engine speed, fuel quality, and intake conditions. The document also discusses knock in diesel engines and different combustion chamber designs for diesel engines, including direct injection and indirect injection types.
1. Combustion involves the rapid chemical combination of fuel and oxygen, resulting in heat release. It requires a combustible mixture, an ignition source, and flame propagation.
2. In spark ignition (SI) engines, a carburetor supplies an air-fuel mixture and a spark plug ignites it. Combustion in SI engines occurs in three stages: ignition lag, flame propagation, and afterburning.
3. Factors like air-fuel ratio, compression ratio, load, turbulence, and engine speed affect the flame propagation rate in SI engines. Higher propagation speeds improve efficiency and fuel economy.
The document discusses combustion in spark-ignition (SI) engines. It defines combustion as a chemical reaction in which fuel combines with oxygen, liberating heat energy. In an SI engine, fuel and air are mixed and inducted into the cylinder where combustion is initiated by a spark at the spark plug near the end of the compression stroke. There are three stages of combustion: ignition lag, flame propagation, and after burning. Abnormal combustion phenomena like pre-ignition and knocking can occur if conditions are not suitable. Factors like turbulence, fuel-air ratio, temperature and pressure, compression ratio, and engine variables affect the flame speed and combustion process.
Detonation occurs when the combustion process moves too quickly in an engine cylinder, causing abnormally high pressure and temperatures. This happens if fuel ignites before the scheduled ignition of the spark plug. Detonation can damage engine components and is caused by factors like improper ignition timing, a lean air-fuel mixture, low octane fuel, and high exhaust back pressure. Engines can be protected from detonation by using higher octane fuel, retarding the ignition timing, cooling the air charge, and ensuring a proper fuel supply. Pre-ignition is a related issue where the fuel ignites prematurely due to hot spots in the combustion chamber rather than the spark plug.
This document outlines the syllabus for an advanced internal combustion engines course. The course is divided into 5 units that cover topics such as: carburetion and combustion in spark ignition engines; compression ignition engines; engine exhaust emission control; alternate fuels; and recent engine technologies. Unit 1 discusses the air-fuel ratio requirements for spark ignition engines, carburetor design and operation, combustion stages, knock factors, and thermodynamic analysis of the combustion process.
The document discusses the design requirements of combustion chambers in spark ignition engines. It states that good combustion chambers aim to provide high power output, efficiency, smooth operation and low emissions. Key design considerations include high compression ratios, turbulence, compact size, and valve and spark plug placement. Historically, T-head, L-head, and I-head (overhead valve) designs have been used, with overhead valve becoming prevalent for its performance at high compression ratios. Modern combustion chamber designs include bath tub and wedge types within cylinder heads.
This document discusses spark ignition engines. It covers air-fuel ratio requirements, the stages of combustion including normal and abnormal combustion, factors that affect knocking, and combustion chambers. Knocking occurs when pockets of the air-fuel mixture explode outside of the normal combustion front, disrupting the precise ignition timing. Factors that influence knocking include density, time, and fuel composition. The design of the combustion chamber aims to provide smooth engine operation and high power output through efficient combustion.
The document summarizes combustion in compression ignition (CI) engines. It describes how combustion occurs simultaneously in many spots in a non-homogeneous fuel-air mixture, controlled by fuel injection timing. The four stages of CI engine combustion are ignition delay, premixed combustion, mixing-controlled combustion, and late combustion. Factors like injection timing and fuel quality can affect the ignition delay period. Knock may occur if ignition delay is too long. The document provides diagrams to illustrate CI engine combustion processes and types.
This document discusses combustion in internal combustion engines. It begins by defining combustion as the rapid chemical combination of fuel and oxygen that releases energy in the form of heat. It then describes the different types of combustion that can occur, including complete and incomplete combustion. The document focuses on the combustion processes in spark-ignition (SI) engines and compression-ignition (CI) engines. For SI engines, it describes the typical three stages of combustion: ignition lag, flame propagation, and afterburning. For CI engines, it outlines the four phases of combustion: ignition delay period, uncontrolled combustion, controlled combustion, and afterburning. Key factors that influence combustion in each engine type are also summarized.
The combustion chamber burns a mixture of air and fuel inside jet engines, maintaining stable combustion over a wide range of operating conditions while minimizing pressure loss and distributing the heated exhaust gases uniformly to the turbine. Different combustion chamber designs are used depending on requirements, employing features like recirculation zones, cooling air, and multiple fuel injectors to efficiently combust the air-fuel mixture under varying operating conditions.
Ci engine combustion by Akhileshwar NiralaAkhilesh Roy
In a compression ignition (CI) engine, fuel is directly injected into the cylinder and spontaneously ignites when mixed with hot, compressed air. Combustion occurs in four stages: ignition delay, premixed combustion, mixing-controlled combustion, and late combustion. There are two main types of CI engines - direct injection engines which inject fuel directly into the chamber, and indirect injection engines which inject fuel into a prechamber before entering the main chamber. Factors like injection timing and quantity, intake conditions, and fuel properties can affect the ignition delay period.
This presentation was prepared by Mechanical Engineering professor Dr. Shahid Imran during their lecture with final year in their Internal Combustion Engine program offered at University of Engineering and Technology Lahore.
This document discusses various types of fuel injection systems for spark ignition and compression ignition engines. It describes the different stages of combustion in diesel engines including ignition delay, rapid combustion, mixing controlled combustion, and late combustion. It also discusses factors that affect combustion like temperature, pressure, composition, and design of the combustion chamber. The document outlines different types of diesel fuel injection systems including mechanical and electronic systems. It describes the purpose and workings of fuel injection pumps, nozzles, and catalytic converters.
Fundamentals of Compression Ignition EngineAnand Kumar
This document provides an overview of fundamentals of compression ignition engines. It begins with classifications of engines based on physical state of mixture and ignition type. It then discusses engine components, the diesel cycle, combustion processes, abnormal combustion, and developments to improve emissions such as common rail direct injection and exhaust gas recirculation. The goal is to introduce key concepts regarding compression ignition engines including working, thermodynamics and developments to control emissions.
The document discusses the stages of combustion in a compression ignition (diesel) engine. It describes four stages: 1) ignition delay period, where fuel is injected and mixes with air before igniting; 2) rapid uncontrolled combustion, where ignition occurs rapidly across the cylinder; 3) mixing-controlled combustion phase, where combustion is controlled by fuel injection rate and mixing; 4) late combustion or afterburning phase, where any remaining fuel continues burning slowly through the expansion stroke. The document explains the physical and chemical processes that occur during each stage.
The document provides explanations of various components of internal combustion engines including connecting rods, crankshafts, piston rings, glow plugs and camshafts. It also lists differences between SI and CI engines and discusses factors that affect engine performance such as compression ratio, thermal efficiency, valve timing and residual gas fraction.
The document discusses combustion in spark-ignition (SI) engines. It defines combustion as a chemical reaction in which fuel combines with oxygen, liberating heat energy. In an SI engine, fuel and air are mixed and inducted into the cylinder where combustion is initiated by a spark at the spark plug near the end of the compression stroke. The combustion process occurs in three stages: ignition lag, flame propagation, and after burning. Abnormal combustion phenomena like pre-ignition and knocking can occur if conditions are not suitable. Factors like turbulence, fuel-air ratio, temperature and pressure, compression ratio, and engine speed and size can affect the flame speed and combustion characteristics in the engine.
Combustion in a SI engine involves three stages:
1. Flame development stage where the spark ignites the fuel-air mixture and a flame nucleus forms.
2. Flame propagation stage where the flame spreads through the combustion chamber. The flame propagation speed affects combustion efficiency.
3. Flame termination stage where combustion continues after peak pressure is reached if a rich fuel mixture is supplied.
This document outlines the topics covered in 5 units of a course on advanced internal combustion engines. Unit I covers spark ignition engines, including air-fuel ratio requirements, stages of combustion, factors affecting knock, and fuel injection systems. Unit II discusses compression ignition engines and combustion analysis. Unit III addresses emission formation and control. Unit IV covers alternate fuels for engines. Unit V presents recent trends, including new engine types and technologies.
The combustion process in internal combustion engines occurs differently than in the Otto and Diesel cycles. Spark ignition engines typically have premixed flames while compression ignition engines have diffusion flames with some premixed combustion. The fuel-air mixture in both must be close to stoichiometric for reliable ignition and combustion. Combustion involves complex chemical reactions between the fuel and oxidant that produce heat and light. Important characteristics of fuels used in each type of engine include energy density, stability, toxicity, and compatibility with engine components. Combustion in both engines occurs in stages defined by physical and chemical processes.
Valve Timing & Combustion Phases in Internal Combustion EnginesHassan Raza
Two-stroke and four-stroke engines have different valve timing strategies. Combustion in engines occurs in distinct phases - ignition lag, flame propagation, and after burning in SI engines, and ignition delay, premixed combustion, controlled combustion, and after burning in CI engines. Factors like fuel type, engine speed, load, and air-fuel ratio affect the timing and progression of combustion.
This document discusses hot surface ignition of combustible fuels. It begins with an introduction explaining how fuel leakage onto hot surfaces can cause aviation and industrial fires. It then provides background on key concepts like auto ignition temperature (AIT), thermal ignition, and hot surface ignition temperature (HSIT). The mechanism of ignition involves both boiling modes (nucleate, transition, and film boiling) and ignition modes (hood fires, gutter fires, and airborne fires). Experimental techniques like the ASTM E659 standard and factors affecting HSIT are also reviewed. Overall, the document aims to build understanding of the process and conditions governing hot surface ignition, which occurs at higher temperatures than AIT due to heat and vapor losses.
The document discusses factors that affect flame speed in internal combustion engines, including turbulence, engine speed, compression ratio, inlet temperature and pressure, and fuel-air ratio. It also covers abnormal combustion such as knocking, factors influencing knocking like density, time, and fuel composition, combustion chamber designs and their effects on flame speed and knocking, and definitions of octane number and types of knocking. The optimal combustion chamber design has a central spark plug location, minimum heat transfer, low octane requirement, and high turbulence for fast, consistent combustion.
This document discusses combustion in spark ignition (SI) engines. It defines combustion as the rapid chemical combination of a substance with oxygen, involving heat and light production. The key stages of combustion in an SI engine are discussed as ignition lag, flame propagation, and after burning. Factors that affect flame speed like turbulence, fuel-air ratio, temperature and pressure are also covered. Abnormal combustion phenomena like pre-ignition and knocking are described along with their effects. Turbulence is explained as important for preparing the air-fuel mixture and distributing the flame front uniformly in the combustion chamber. Questions asked during the presentation related to using different fuels, increasing pressure ratio, the role of flame speed and turbulence, spark plug positioning, and
Combustion behaviour in Internal Combustion engines.pptAyisha586983
1. Combustion in a CI engine occurs in four stages: ignition delay, premixed combustion, mixing-controlled combustion, and late combustion.
2. During ignition delay, injected fuel atomizes, vaporizes, and mixes with air. Premixed combustion then occurs rapidly.
3. Mixing-controlled combustion makes up 70-80% of heat release as the burning rate is controlled by fuel-air mixing. Late combustion involves residual fuel burning.
4. Key factors that affect ignition delay include injection timing and pressure, fuel properties like cetane number, and in-cylinder conditions like temperature and pressure. Short ignition delay leads to smoother operation.
The document discusses combustion in compression ignition (CI) engines. It describes how combustion occurs simultaneously in many spots in the non-homogeneous fuel-air mixture, unlike spark ignition engines where combustion is a propagating flame front. CI engines have higher compression ratios of 12-24 and fuel is injected late in the compression stroke. Combustion occurs in four stages: ignition delay, premixed combustion, mixing-controlled combustion, and late combustion. Factors like injection timing and fuel quality affect the ignition delay period. Knock can occur if the ignition delay is too long.
The document provides an overview of internal combustion engines. It discusses the basic classifications and cycles of internal combustion engines including two-stroke and four-stroke engines. It also covers the workings of spark ignition and compression ignition engines, as well as common engine components and systems such as carburetors and fuel injection systems. Key topics include the Otto, Diesel, and Carnot power cycles; combustion stages; valve timing diagrams; and scavenging, pre-ignition, detonation, lubrication, and emissions control.
APPLIED THERMODYNAMICS 18ME42 Module 01 question no 2a &2bTHANMAY JS
This document discusses an applied thermodynamics course on internal combustion engines taught by Mr. Thanmay J.S. The course aims to help students understand fundamentals, combustion processes, and performance testing of I.C. engines. Key topics covered include types of I.C. engines; combustion in spark ignition and compression ignition engines; engine fuels; and methods to analyze engine performance and efficiency. The document provides details on engine terminology, classification, combustion stages, factors affecting detonation, fuel properties, and methods for rating spark ignition and compression ignition engine fuels.
The document summarizes the key components and functioning of a gas turbine combustion chamber. It describes the combustion chamber, diffuser, liner, snout, dome, and swirler. The combustion chamber must stabilize flames in a continuous high-velocity air flow. It utilizes techniques like bluff bodies or swirl to generate recirculation zones for ignition and flame anchoring. The liner must withstand high temperatures and is cooled using film or transpiration cooling techniques.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
The document discusses the Homogeneous Charged Compression Ignition (HCCI) engine. HCCI engines combine aspects of gasoline and diesel engines by using a premixed homogeneous fuel-air mixture that is compressed to autoignition. Key parameters that affect HCCI combustion include temperature, pressure, fuel composition/octane number, equivalence ratio, exhaust gas recirculation, and compression ratio. HCCI engines offer advantages like high efficiency and very low NOx emissions compared to gasoline and diesel engines. However, controlling ignition timing over different operating conditions is a major challenge to implementing HCCI engines.
The document discusses fuel use in compression ignition (CI) and spark ignition (SI) engines. It describes two categories of CI engines: indirect-injection and direct-injection. It outlines the types of cylinders used in CI engines and provides a schematic of diesel spray and combustion chemistry. The combustion process in a CI engine is described in four stages: ignition delay, premixed combustion, mixing-controlled combustion, and late combustion. Hardware factors like injection timing and quantity that affect ignition delay time are also summarized.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
The document discusses the combustion stages in a compression ignition (CI) engine:
1. Ignition delay stage where fuel does not ignite immediately upon injection.
2. Uncontrolled combustion stage where rapid combustion occurs causing a steep pressure rise.
3. Controlled combustion stage where further pressure rise is controlled by injection rate.
4. Afterburning stage where unburnt fuel particles continue burning in the expansion stroke.
Diesel knock can occur if the ignition delay is long, allowing too much fuel to accumulate and cause an excessively rapid pressure rise when combustion begins. Methods to control knocking include using higher cetane fuel or modifying the combustion chamber design.
Similar to 5+ combustion and combustion chamber for si engines (20)
Applications of artificial Intelligence in Mechanical Engineering.pdfAtif Razi
Historically, mechanical engineering has relied heavily on human expertise and empirical methods to solve complex problems. With the introduction of computer-aided design (CAD) and finite element analysis (FEA), the field took its first steps towards digitization. These tools allowed engineers to simulate and analyze mechanical systems with greater accuracy and efficiency. However, the sheer volume of data generated by modern engineering systems and the increasing complexity of these systems have necessitated more advanced analytical tools, paving the way for AI.
AI offers the capability to process vast amounts of data, identify patterns, and make predictions with a level of speed and accuracy unattainable by traditional methods. This has profound implications for mechanical engineering, enabling more efficient design processes, predictive maintenance strategies, and optimized manufacturing operations. AI-driven tools can learn from historical data, adapt to new information, and continuously improve their performance, making them invaluable in tackling the multifaceted challenges of modern mechanical engineering.
Use PyCharm for remote debugging of WSL on a Windo cf5c162d672e4e58b4dde5d797...shadow0702a
This document serves as a comprehensive step-by-step guide on how to effectively use PyCharm for remote debugging of the Windows Subsystem for Linux (WSL) on a local Windows machine. It meticulously outlines several critical steps in the process, starting with the crucial task of enabling permissions, followed by the installation and configuration of WSL.
The guide then proceeds to explain how to set up the SSH service within the WSL environment, an integral part of the process. Alongside this, it also provides detailed instructions on how to modify the inbound rules of the Windows firewall to facilitate the process, ensuring that there are no connectivity issues that could potentially hinder the debugging process.
The document further emphasizes on the importance of checking the connection between the Windows and WSL environments, providing instructions on how to ensure that the connection is optimal and ready for remote debugging.
It also offers an in-depth guide on how to configure the WSL interpreter and files within the PyCharm environment. This is essential for ensuring that the debugging process is set up correctly and that the program can be run effectively within the WSL terminal.
Additionally, the document provides guidance on how to set up breakpoints for debugging, a fundamental aspect of the debugging process which allows the developer to stop the execution of their code at certain points and inspect their program at those stages.
Finally, the document concludes by providing a link to a reference blog. This blog offers additional information and guidance on configuring the remote Python interpreter in PyCharm, providing the reader with a well-rounded understanding of the process.
Comparative analysis between traditional aquaponics and reconstructed aquapon...bijceesjournal
The aquaponic system of planting is a method that does not require soil usage. It is a method that only needs water, fish, lava rocks (a substitute for soil), and plants. Aquaponic systems are sustainable and environmentally friendly. Its use not only helps to plant in small spaces but also helps reduce artificial chemical use and minimizes excess water use, as aquaponics consumes 90% less water than soil-based gardening. The study applied a descriptive and experimental design to assess and compare conventional and reconstructed aquaponic methods for reproducing tomatoes. The researchers created an observation checklist to determine the significant factors of the study. The study aims to determine the significant difference between traditional aquaponics and reconstructed aquaponics systems propagating tomatoes in terms of height, weight, girth, and number of fruits. The reconstructed aquaponics system’s higher growth yield results in a much more nourished crop than the traditional aquaponics system. It is superior in its number of fruits, height, weight, and girth measurement. Moreover, the reconstructed aquaponics system is proven to eliminate all the hindrances present in the traditional aquaponics system, which are overcrowding of fish, algae growth, pest problems, contaminated water, and dead fish.
Software Engineering and Project Management - Introduction, Modeling Concepts...Prakhyath Rai
Introduction, Modeling Concepts and Class Modeling: What is Object orientation? What is OO development? OO Themes; Evidence for usefulness of OO development; OO modeling history. Modeling
as Design technique: Modeling, abstraction, The Three models. Class Modeling: Object and Class Concept, Link and associations concepts, Generalization and Inheritance, A sample class model, Navigation of class models, and UML diagrams
Building the Analysis Models: Requirement Analysis, Analysis Model Approaches, Data modeling Concepts, Object Oriented Analysis, Scenario-Based Modeling, Flow-Oriented Modeling, class Based Modeling, Creating a Behavioral Model.
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
artificial intelligence and data science contents.pptxGauravCar
What is artificial intelligence? Artificial intelligence is the ability of a computer or computer-controlled robot to perform tasks that are commonly associated with the intellectual processes characteristic of humans, such as the ability to reason.
› ...
Artificial intelligence (AI) | Definitio
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
Rainfall intensity duration frequency curve statistical analysis and modeling...bijceesjournal
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Findings: Based on findings, the Gumbel approach produced the highest intensity values, whereas the other approaches produced values that were close to each other. The data indicates that 461.9 mm of rain fell during the monsoon season’s 301st week. However, it was found that the 29th week had the greatest average rainfall, 92.6 mm. With 952.6 mm on average, the monsoon season saw the highest rainfall. Calculations revealed that the yearly rainfall averaged 1171.1 mm. Using Weibull’s method, the study was subsequently expanded to examine rainfall distribution at different recurrence intervals of 2, 5, 10, and 25 years. Rainfall and recurrence interval mathematical correlations were also developed. Further regression analysis revealed that short wave irrigation, wind direction, wind speed, pressure, relative humidity, and temperature all had a substantial influence on rainfall.
Originality and value: The results of the rainfall IDF curves can provide useful information to policymakers in making appropriate decisions in managing and minimizing floods in the study area.
Design and optimization of ion propulsion dronebjmsejournal
Electric propulsion technology is widely used in many kinds of vehicles in recent years, and aircrafts are no exception. Technically, UAVs are electrically propelled but tend to produce a significant amount of noise and vibrations. Ion propulsion technology for drones is a potential solution to this problem. Ion propulsion technology is proven to be feasible in the earth’s atmosphere. The study presented in this article shows the design of EHD thrusters and power supply for ion propulsion drones along with performance optimization of high-voltage power supply for endurance in earth’s atmosphere.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
2. Introduction
Combustion is a chemical reaction in which certain elements of the fuel like
hydrogen and carbon combine with oxygen liberating heat energy and
causing an increase in temperature of the gases.
The conditions necessary for combustion are the presence of
combustible mixture (Fuel +oxidizer)
some means of initiating the process
Depending on the type of engines, process of combustion generally takes
place either in
a homogeneous or
a heterogeneous fuel vapor-air mixture
2
3. Homogeneous Mixture
In spark-ignition engines homogeneous mixture of air and fuel is formed
in the (Carburetor, PFI and DFI) then combustion is initiated at the end
of compression stroke.
Once the fuel vapor-air mixture is ignited, a flame front appears and
rapidly spreads through the mixture
The flame propagation is caused by heat transfer and diffusion of
burning fuel molecules from the combustion zone to the adjacent layers of
fresh mixture
The velocity at which the flame front moves, with respect to the unburned
mixture in a direction normal to its surface is called the normal flame
velocity
3
4. In a SI engine working with gasoline/petrol, the maximum flame
speed is obtained when Φ is between 1.1 and 1.2, i.e., when the
mixture is slightly richer than stoichiometric.
If the equivalence ratio is outside this range the flame speed drops
rapidly to a low value and ceases to propagate
Introducing turbulence and incorporating proper mixture movement
can increase flame speed in a mixtures outside the above range.
Combustion in the SI engine can be classified as Normal Combustion and
Abnormal Combustion
In a homogeneous mixture,
4
5. Stages of Combustion in SI Engine
From the theoretical pressure-crank angle diagram
a-b Compression process
b-c Combustion process
c-d Expansion process
The entire pressure rise during combustion takes place at constant
volume,
In actual engines this
does not happen. Actual
SI engine combustion
process consists of three
stages.
5
6. The 3 stages Actual engine combustion process
Point A is the point of spark initiation (say 200bTDC)
Point B is the point at which the beginning of pressure rise can be
detected (say 80 bTDC)
Point C the attainment of peak pressure.
AB-First stage (Delay
Period)
BC-Second stage (flame
Propagation)
CD -Third stage (wall
Quenching)
6
7. The First Stage (A-B) (Delay Period)
The first stage is referred to as the ignition lag or preparation
phase in which growth and development of a self propagating
nucleus of flame takes place
This process is a chemical process depending upon
both temperature and pressure,
the nature of the fuel and
the proportion of the exhaust residual gas.
the relationship between the temperature and the rate of
reaction.
7
8. Reaction rate
8
Empirical correlations have been developed for the fuel
reaction rate:
l
m
n
Inert
O
Fuel
T
R
E
A
dt
Fuel
d
]
[
]
[
]
[
exp
]
[
2
where [ ] in units of gmol/cm3
R = 1.987 cal/gmolK
E typically 20 - 40 kcal/gmol
Note typically l= 0
9. The second stage (B-C) (flame Propagation)
The second stage is a physical one and it is concerned with the spread of
the flame throughout the combustion chamber.
The starting point of the second stage is where the first measurable rise of
pressure is seen on the indicator diagram i.e., the point where the line of
combustion departs from the compression line (point B).
During the second stage the flame propagates practically at a constant
velocity.
Heat transfer to the cylinder wall is low, because only a small part of the
burning mixture comes in contact with the cylinder wall during this period.
9
10. The rate of heat-release depends largely on
the turbulence intensity and
the reaction rate which is dependent on the mixture
composition
The rate of pressure rise is proportional to the rate of heat-
release because during this stage, the combustion chamber
volume remains practically constant
The second stage (B-C) (flame Propagation)
10
11. The third stage starts at instant at which the maximum pressure is reached
on the indicator diagram (point C).
The flame velocity decreases during this stage.
The rate of combustion becomes low due to lower flame velocity and
reduced flame front surface.
The expansion stroke starts before this stage of combustion, with the piston
moving away from the top dead centre, there can be no pressure rise
during this stage.
The Third Stage c-d (Wall Quenching)
11
12. Flame Front Propagation
The two important factors which determine the rate of movement of the
flame front across the combustion chamber are:
Reaction rate: is the result of a purely chemical combustion process in
which the flame eats its way into the unburned charge
Transposition rate: is due to the physical movement of the flame front
relative to the cylinder wall and is also the result of pressure differential
between the burning gases and the unburnt gases in the combustion
chamber.
12
14. Area I-(A-B)
The flame front progresses relatively slowly due to a low
transposition rate. Comparatively small mass of charge burned
at the start.
The low reaction rate plays a dominant role resulting in a slow
advance of the flame.
The lack of turbulence reduces the reaction rate and hence the
flame speed.
14
15. As the flame front leaves the quiescent zone and proceeds into
more turbulent areas (area II) where it consumes a greater mass
of mixture, it progresses more rapidly and at a constant rate (B-C)
Area III (C-D)
The volume of unburned charge is very less towards the end of
flame travel and so the transposition rate again becomes
negligible thereby reducing the flame speed.
The reaction rate is also reduced again since the flame is entering
a zone of relatively low turbulence (C-D)
Area II (B-C)
15
16. Other Factors Influencing The Flame Speed
The most important factors which affect the flame speed are the
turbulence, the fuel-air ratio, temperature and pressure,
compression ratio, engine output and engine speed
I. Turbulence
Flame speed is quite low in non-turbulent mixtures and increases
with increasing turbulence
Design of the combustion chamber which involves the geometry
of cylinder head and piston crown increases the turbulence
during the compression stroke.
16
17. Turbulence increases the heat flow to the cylinder wall. It also
accelerates the chemical reaction by increasing the rate of contact of
burning and unburned particles.
The increase of flame speed due to turbulence
reduces the combustion duration and hence minimizes the
tendency of abnormal combustion.
However, excessive turbulence:
may extinguish the flame resulting in rough and noisy operation
of the Engine.
I. Turbulence
17
18. II. Fuel-Air Ratio
The fuel-air ratio has a very significant influence on the flame
speed
The highest flame velocities (minimum time for complete combustion)
are obtained with somewhat richer mixture (point A)
When the mixture is made leaner or
richer from point A, the flame speed
decreases
Less thermal energy is released in the
case of lean mixtures resulting in lower
flame temperature.
Very rich mixtures lead to incomplete
combustion which results again in the
release of less thermal energy
18
19. III. Temperature and Pressure
Flame speed increases with an increase in intake temperature
and pressure.
A higher initial pressure and temperature may help to form a
better homogeneous air-vapors mixture which helps in
increasing the flame speed.
This is possible because of an overall increase in the density
of the charge.
19
20. IV. Compression Ratio
A higher compression ratio increases the pressure and temperature
of the working mixture which reduce the initial preparation phase of
combustion and hence less ignition advance is needed.
Increased compression ratio reduces the clearance volume and
therefore increases the density of the cylinder gases during burning.
Increasing the density increases the peak pressure and temperature
and the total combustion duration is reduced.
Thus engines having higher compression ratios have higher flame
speeds.
20
21. V. Engine Output
With the increased throttle opening the cylinder gets filled to a higher
density. The cycle pressure increases when the engine output is increased.
When the output is decreased by throttling, the initial and final
compression pressures decrease and the dilution of the working mixture
increases.
The smooth development of self-propagating nucleus of flame becomes
unsteady and difficult.
The main disadvantages of SI engines are the poor combustion at low
loads and the necessity of mixture enrichment (Ø> between 1.2 to 1.3)
which causes wastage of fuel and discharge of unburnt hydrocarbon and
the products of incomplete combustion like carbon monoxide etc. in the
atmosphere.
21
22. VI. Engine Speed
The flame speed increases almost linearly with engine
speed since the increase in engine speed increases the
turbulence inside the cylinder.
The time required for the flame to traverse the
combustion space would be halved, if the engine speed
is doubled.
22
23. RATE OF PRESSURE RISE
The rate of pressure rise in an engine combustion chamber
exerts a considerable influence on
The peak pressure developed,
The power produced and
The smoothness with which the forces are transmitted to the
piston.
The rate of pressure rise is mainly dependent upon the rate of
combustion of mixture in the cylinder.
23
24. With lower rate of
combustion longer time is
required to complete the
combustion which
necessitates the initiation
of burning at an early
point on the compression
stroke.
RATE OF PRESSURE RISE
Curve I is for a high, curve II for the normal and curve III for
a low rate of combustion.
24
25. Higher rate of combustion results in higher rate of pressure rise
producing higher peak pressures at a point closer to TDC.
Higher peak pressures closer to TDC produce a greater force
acting through a large part of the power stroke and hence,
increase the power output of the engine.
The higher rate of pressure rise causes rough running of the
engine because of vibrations produced in the crankshaft
rotation.
RATE OF PRESSURE RISE
25
26. It also tends to promote an undesirable occurrence known as
knocking.
A compromise between these opposing factors is accomplished
by designing and operating the engine in such a manner that
approximately one-half of the maximum pressure is reached by
the time the piston reaches TDC.
This results in the peak pressure being reasonably close to the
beginning of the power stroke, yet maintaining smooth engine
operation.
RATE OF PRESSURE RISE
26
27. ABNORMAL COMBUSTION
KNOCK AND SURFACE-IGNITION
Abnormal combustion reveals itself in many ways. The two major
abnormal combustion processes which are important in practice,
are knock and surface-ignition.
These abnormal combustion phenomena are of concern because:
1) when severe, they can cause major engine damage; and
2) Even if not severe, they are regarded as an objectionable
source of noise by the engine or vehicle operator.
27
28. Description: Abnormal combustion
Knock is the name given to the noise which is transmitted through the
engine structure when essentially spontaneous ignition of a portion of the
end gas - the fuel, air, residual gas, mixture ahead of the propagating
flame occurs.
There is an extremely rapid release of most of the chemical energy in the end-gas,
causing very high local pressures and the propagation of pressure waves of
substantial amplitude across the combustion chamber.
Surface Ignition is ignition of the fuel-air mixture by a hot spot on the
combustion chamber walls such as an overheated valve or spark plug, or
glowing combustion-chamber deposit: i.e., by any means other than the
normal spark discharge.
Following surface ignition, a flame develops at each surface-ignition location and
starts to propagate across the chamber in an analogous manner to what occurs with
normal spark-ignition.
28
29. causes for end gas combustion
Heat-release due to combustion in SI engines, increases the
temperature and the pressure, of the burned part of the
mixture above those of the unburned mixture
In order to effect pressure equalization the burned part of the
mixture will expand, and compress the unburned mixture
adiabatically thereby increasing its pressure and temperature
If the temperature of the unburnt mixture exceeds the self-
ignition temperature of the fuel spontaneous ignition or auto-
ignition occurs at various pin-point locations.
29
30. The advancing flame front compresses the end charge BB'D
farthest from the spark plug, thus raising its temperature.
In spite of these factors if the temperature of the end charge had not
reached its self-ignition temperature, the charge would not auto ignite
and the flame will advance further and consume the charge BB'D.
causes for end gas combustion
30
31. However, if the end charge BB'D reaches its auto ignition temperature the
charge will auto ignite, leading to knocking combustion.
it is assumed that when flame has reached the position BB', the charge
ahead of it has reached critical auto-ignition temperature.
Knock In SI Engines
31
32. Knock in SI Engines
Pressure variation in the cylinder during knocking combustion for
normal combustion, light knock and heavy knock, respectively
32
33. Because of the auto ignition, another flame front starts traveling
in the opposite direction to the main flame front.
When the two flame fronts collide, a severe pressure pulse is
generated.
The presence or absence of knocking in combustion is often
judged from a distinctly audible sound.
A scientific method to detect the phenomenon of knocking is to
use a pressure transducer.
Knock In SI Engines
33
34. knocking is very much dependent on the properties of fuel.
If the unburned charge does not reach its auto ignition
temperature there will be no knocking.
If the ignition delay period is longer the time required for the
flame front to burn through the unburned charge will be short,
then there will be no knocking.
Hence, in order to avoid or inhibit detonation, and a high auto
ignition temperature, a long ignition delay are the desirable
qualities for SI engine fuels.
Knock In SI Engines
34
35. Effect of Engine Variables on Knock
Effect of temperature
Reduced temperature of the unburned charge reduce the
possibility of knocking by reducing the temperature of the end
charge for auto ignition.
Effect of Compression Ratio
Increase in compression ratio increases the pressure and temperature
of the gases at the end of the compression stroke, increases the
tendency for knocking.
35
36. Effect of density
Reduction in density of the charge tends to reduce knocking by
providing lower energy release.
The overall increase in the density of the charge due to higher
compression ratio increases the pre-flame reactions in the end charge
thereby increasing the knocking tendency of the engine.
Inlet Temperature of the Mixture:
Increase in the inlet temperature of the mixture makes the compression
temperature higher thereby, increasing the tendency of knocking.
Further, volumetric efficiency will be lowered. Hence, a lower inlet
temperature is always preferable to reduce knocking.
Effect of Engine Variables on Knock
36
37. Effect of Engine Variables on Knock
Mass of inducted charge
A reduction in the mass of the inducted charge into the cylinder by
throttling or reducing the amount of supercharging reduces both
temperature and density of the charge at the time of ignition .This
decreases the tendency of knocking .
Temperature of the Combustion Chamber Walls
To prevent knocking the hot spots in the combustion chamber should
be avoided.
Since, the spark plug and exhaust valve are two hottest parts in the
combustion chamber, the end gas should not be compressed against
them
37
38. Effect of Engine Variables on Knock
Retarding the Spark Timing:
Retarding the spark timing from the optimized timing, i.e., having the
spark closer to TDC, the peak pressures are reached farther down on the
power stroke and are thus of lower magnitude.
This might reduce the knocking. However, the spark timing will be
different from the MBT timing affecting the brake torque and power
output of the engine.
38
39. Power Output of the Engine
A decrease in the output of the engine decreases the temperature of
the cylinder and the combustion chamber walls and also the pressure
of the charge thereby lowering mixture and end gas temperatures.
This reduces the tendency to knock.
Turbulence
Turbulence depends on the design of the combustion chamber and
on engine speed.
Increasing turbulence increases the flame speed and reduces the
time available for the end charge to attain auto ignition conditions
thereby decreasing the tendency to knock.
Effect of Engine Variables on Knock
39
40. Effect of Engine Variables on Knock
Engine Speed
An increase in engine speed increases the turbulence of the mixture
considerably resulting in increased flame speed, and reduces the time
available for pre-flame reactions. Hence knocking tendency is
reduced at higher speeds.
Flame travel Distance
The knocking tendency is reduced by shortening the time required for
the flame front to traverse the combustion chamber.
Engine size, combustion chamber shape, and spark plug position are
the three important factors governing the flame travel distance
40
41. Effect of Engine Variables on Knock
Engine size
The flame requires a longer time to travel across the combustion
chamber of a larger engine.
Therefore, a larger engine has a greater tendency for knocking
than a smaller engine since there is more time for the end gas to
auto ignite.
Hence, an SI engine is generally limited to size of about 150 mm
bore.
Combustion Chamber Shape
Generally, the more compact the combustion chamber is, the
shorter is the flame travel and the combustion time and hence
better antiknock characteristics.
41
42. The combustion chambers are made as spherical as possible to minimize
the length of the flame travel for a given volume.
If the turbulence in the combustion chamber is high, the combustion rate is
high and consequently combustion time and knocking tendency are reduced.
Hence, the combustion chamber is shaped in such a way as to promote
turbulence.
Location of Spark Plug
In order to have a minimum flame travel, the spark plug is centrally
located in the combustion chamber, resulting in minimum knocking
tendency.
The flame travel can also be reduced by using two or more spark plugs in
case of large engines.
Effect of Engine Variables on Knock
42
43. Composition Factors
Fuel-Air Ratio:
The flame speeds are affected by fuel-air ratio. Also the flame
temperature and reaction time are different for different fuel-air
ratios.
Maximum flame speed and temperature is obtained when Φ≈1.1-
1.2.
Octane Value of the Fuel
A higher self-ignition temperature of the fuel and a low pre-flame reactivity
would reduce the tendency of knocking.
In general, Paraffin series of hydrocarbon have the maximum and aromatic
series the minimum tendency to knock. The naphthene series comes in
between the two
43
44. Combustion Chambers For SI Engines
The design of the combustion chamber for an SI engine has an important
influence on the engine performance and its knocking tendencies.
The design involves
the shape of the combustion chamber,
the location of spark plug and
the location of inlet and exhaust valves.
The important requirements of an SI engine combustion chamber are
• to provide high power output with minimum octane requirement,
• high thermal efficiency and
• smooth engine operation.
44
45. Combustion Chambers For SI Engines
I. Smooth engine operation
The aim of any engine design is to have a smooth operation and a
good economy.
These can be achieved by the following:
a. Moderate Rate of Pressure Rise
Limiting the rate of pressure rise as well as the position of the
peak pressure with respect to TDC affect smooth engine
operation.
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46. b. Reducing the Possibility of Knocking
Reduction in the possibility of knocking in an engine can be achieved
by,
Reducing the distance of the flame travel by centrally locating the
spark plug and also by avoiding pockets of stagnant charge.
Satisfactory cooling of the spark plug and of exhaust valve area
which are the source of hot spots in the majority of the combustion
chambers.
Reducing the temperature of the last portion of the charge, through
application of a high surface to volume ratio in that part where
the last portion of the charge burns.
Combustion Chambers For SI Engines
46
47. Combustion Chambers For SI Engines
II. High Power Output and Thermal Efficiency
This can be achieved by considering the following factors:
a. A high degree of turbulence is needed to achieve a high flame front
velocity.
Turbulence is induced by inlet flow configuration or squish
Squish is the rapid radial movement of the gas trapped in
between the piston and the cylinder head into the bowl or the
dome.
Squish can be induced in spark-ignition engines by having a
bowl in piston or with a dome shaped cylinder head.
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48. b. High Volumetric Efficiency
More charge during the suction stroke, results in an
increased power output.
This can be achieved by providing ample clearance around
the valve heads,
large diameter valves and straight passages with minimum
pressure drop.
c. Improved anti-knock characteristics
Improved anti-knock characteristics permits the use of a
higher compression ratio resulting in increased output and
efficiency.
Combustion Chambers For SI Engines
48
49. d. A Compact Combustion Chamber
Reduces heat loss during combustion and increases the thermal
efficiency.
Different types combustion chambers have been developed over
a period of time Some of them are shown in Fig.
T-Head Type
L-Head Type
I-Head Type or Overhead Valve
F-Head Type
Combustion Chambers For SI Engines
49
50. The T-head combustion chambers were
used in the early stage of engine
development.
Since the distance across the combustion
chamber is very long, knocking tendency is
high in this type of engines.
This configuration provides two valves on
either side of the cylinder, requiring two
camshafts. From the manufacturing point of
view, providing two camshafts is a
disadvantage.
T-Head Type:
50
51. A modification of the T-head type of
combustion chamber is the L-head type which
provides the two valves on the same side of the
cylinder and the valves are operated by a single
camshaft.
The main objectives of the Ricardo's turbulent
head design, Fig (c), axle to obtain fast flame
speed and reduced knock
L-Head Type
51
52. In which both the valves are located on the cylinder
head.
The overhead valve engine is superior to a side
valve or an L-head engine at high compression
ratios.
Some of the important characteristics of this type of
valve arrangement are:
less surface to volume ratio and therefore less heat
loss
less flame travel length and hence greater freedom
from knock
higher volumetric efficiency from larger valves or
valve lifts
I Head Type or Overhead Valve:
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53. F-Head Type:
The F-head type of valve arrangement is a compromise
between L-head and I-head types.
Combustion chambers in which one valve is in the
cylinder head and the other in the cylinder block are
known as F-head combustion chambers
Modern F-head engines have exhaust valve in the
head and inlet valve in the cylinder block.
The main disadvantage of this type is that the inlet
valve and the exhaust valve are separately actuated by
two cams mounted on to camshafts driven by the
crankshaft through gears.
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