1) Automobiles are a major source of air pollutants like CO, hydrocarbons, NOx, and lead.
2) The formation of pollutants depends on factors like the air-fuel ratio, compression, and spark timing in internal combustion engines.
3) Leaner fuel mixtures and higher compression reduce CO but increase NOx, while retarded spark timing lowers maximum combustion temperatures to reduce both CO and NOx.
An internal combustion engine is a heat engine (a device in which thermal energy is converted into mechanical
energy) in which the heat source is a combustible mixture that also serves as the working fluid. The working
fluid in turn is used either to (1) produce shaft work by pushing on a piston or turbine blade that in turn
drives a rotating shaft or (2) create a high-momentum fluid that is used directly for propulsive force.
Exhaust analysis of four stroke single cylinder diesel engine using copper ba...ijsrd.com
Exhaust emissions of much concern are Hydrocarbon (HC), Carbon Monoxide (CO) and Nitrogen Oxide (NOx) from the automotive vehicles. Catalytic converter oxidizes harmful CO and HC emission to CO2 and H2O in the exhaust system and thus the emission is controlled. There are several types of problems associated with noble metal based catalytic converter. These factors encourage for the possible application of non-noble metal based material such as copper as a catalyst, which may by proper improvements be able to show the desired activity and can also offer better durability characteristics due to its poison resistant nature. The present work is aimed at using copper as a catalyst for catalytic converter. Wire mesh copper catalytic converter is developed for a volume of 1.54 m3. The experiment is carried out on four stroke single cylinder CI engine. The optimum values of exhaust emissions found at full load are HC (126 ppm), CO (0.03 %). By using copper based catalytic converter it is found that HC is reduced by 33 % and CO by 66 % at full load.
An internal combustion engine is a heat engine (a device in which thermal energy is converted into mechanical
energy) in which the heat source is a combustible mixture that also serves as the working fluid. The working
fluid in turn is used either to (1) produce shaft work by pushing on a piston or turbine blade that in turn
drives a rotating shaft or (2) create a high-momentum fluid that is used directly for propulsive force.
Exhaust analysis of four stroke single cylinder diesel engine using copper ba...ijsrd.com
Exhaust emissions of much concern are Hydrocarbon (HC), Carbon Monoxide (CO) and Nitrogen Oxide (NOx) from the automotive vehicles. Catalytic converter oxidizes harmful CO and HC emission to CO2 and H2O in the exhaust system and thus the emission is controlled. There are several types of problems associated with noble metal based catalytic converter. These factors encourage for the possible application of non-noble metal based material such as copper as a catalyst, which may by proper improvements be able to show the desired activity and can also offer better durability characteristics due to its poison resistant nature. The present work is aimed at using copper as a catalyst for catalytic converter. Wire mesh copper catalytic converter is developed for a volume of 1.54 m3. The experiment is carried out on four stroke single cylinder CI engine. The optimum values of exhaust emissions found at full load are HC (126 ppm), CO (0.03 %). By using copper based catalytic converter it is found that HC is reduced by 33 % and CO by 66 % at full load.
Experimental investigation of the effect of hydrogen addition on combustion p...Amiya K. Sahoo
The world is presently confronted with two major issues; fossil fuel depletion and environmental degradation. Indiscriminate extraction and high consumption of fossil fuels have led to reduction in crude oil resources. The search for an alternative fuel, which promises a harmonious correlation with sustainable development, energy conservation, management, efficiency, and environmental preservation, has become highly pronounced in the present context.
One approach to reduce these problems is by blending hydrogen gas with hydrocarbon fuels used in internal combustion engines.Recently, using hydrogen or hydrogen-gasoline blends as a supplement fuel for spark ignition and compression ignition engines is one of the potential solutions for improving brake thermal efficiency, reducing fuel consumption and pollution emissions from internal combustion engines.
In this paper, advantages and disadvantages of Hydrogen-Gasoline fuels in the context of combustion engines are discussed, and combustion performances and emission characteristics are experimentally investigated at various hydrogen volume fraction and graphs are plotted.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Engine Emissions at Various Cetane Numbers with Exhaust Gas RecirculationIOSR Journals
Typical engine fuels are blends of various fuels species, i.e., multi component. Thus, the original
single component fuel vaporization model was replaced by a multi component fuel vaporization model .The
model has been extended to model diesel sprays under typical diesel conditions, including the effect of fuel
cetane number variation .Necessary modifications were carried out at the various cooling rates. Found the
performance of the diesel engine under various cooling rates at various cetane numbers, also various quantities
of exhaust gas was re circulated and found performance of the engine
Experimental investigation of the effect of hydrogen addition on combustion p...Amiya K. Sahoo
The world is presently confronted with two major issues; fossil fuel depletion and environmental degradation. Indiscriminate extraction and high consumption of fossil fuels have led to reduction in crude oil resources. The search for an alternative fuel, which promises a harmonious correlation with sustainable development, energy conservation, management, efficiency, and environmental preservation, has become highly pronounced in the present context.
One approach to reduce these problems is by blending hydrogen gas with hydrocarbon fuels used in internal combustion engines.Recently, using hydrogen or hydrogen-gasoline blends as a supplement fuel for spark ignition and compression ignition engines is one of the potential solutions for improving brake thermal efficiency, reducing fuel consumption and pollution emissions from internal combustion engines.
In this paper, advantages and disadvantages of Hydrogen-Gasoline fuels in the context of combustion engines are discussed, and combustion performances and emission characteristics are experimentally investigated at various hydrogen volume fraction and graphs are plotted.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Engine Emissions at Various Cetane Numbers with Exhaust Gas RecirculationIOSR Journals
Typical engine fuels are blends of various fuels species, i.e., multi component. Thus, the original
single component fuel vaporization model was replaced by a multi component fuel vaporization model .The
model has been extended to model diesel sprays under typical diesel conditions, including the effect of fuel
cetane number variation .Necessary modifications were carried out at the various cooling rates. Found the
performance of the diesel engine under various cooling rates at various cetane numbers, also various quantities
of exhaust gas was re circulated and found performance of the engine
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
2. IV. GASEOUS POLLUTION AND
PHOTOCHEMICAL SMOG
b. Formation
I. The Automobile Internal Combustion (Otto cycle)
Seinfeld Chapt. 3
Wark and Warner Chapt. 10
Main cause of L.A. type smog
Main source of CO, NMHC, NOx, and Pb in developing countries.
Mobile sources much stronger source than stationary sources for all
but NOx.
3. Image
INTAKE - Downward motion draws in air/fuel
mixture
COMPRESSION - For higher efficiency
POWER - Combustion initiated by spark plug
EXHAUST - Push out burned hydrocarbons
11. Exhaust is not the only source of air pollutants. In an unregulated auto:
Image
Gas tank 10%
Carburetor 10%
Crankcase* 25%
Exhaust 55%
Total 100%
Hydrocarbon Sources in an Unregulated Auto
* Called "Blowby"
12. Evaporation from gas tank and carburetor are easy to control, but essentially all
of the NOx, CO, and Pb comes from the exhaust.
Image
Recirculation System
• Engine off - vapors onto charcoal
• Engine on - intake sucks air and HC out of charcoal
• Positive crankcase ventilation
• Without controls 3% of the fuel would be lost
13. II. How to Tune a Car
Equilibrium calculation told us to burn lean and at high compression to produce
less CO. High compression also ups thermodynamic efficiency; Carnot cycle
efficiency is defined from the ratio of cold to hot temperatures:
A. Air-Fuel-Ratio
Best power at AFR of 12.5 (rich)
Best mileage at 15.5 (lean)
ARF above 17 causes misfiring
ARF below 10 causes flooding and plug fouling
ARF of about 14.5 ( = 1.0) is stoichiometric
14. •Automobiles: Otto cycle the cycle used in spark-ignition internal
combustion engines run on gasoline. Its theoretical efficiency depends on
the compression ratio r of the engine and the specific heat ratio (Cp/Cv = γ)
of the gas in the combustion chamber.
The higher the compression ratio, the higher the temperature in the
cylinder as the fuel burns and so the higher the efficiency. The
maximum compression ratio usable is limited by the need to prevent
preignition (knocking), where the fuel ignites by compression before
the spark plug fires. The specific heat ratio of the air-fuel mixture γ
~1.40. Compression ratios for gasoline powered cars range from 10:1
to 14:1 for racing engines. Alcohol powered cars have 15:1; Diesel
14:1 to 23:1.
15. B. Compression
Higher compression means higher power
•Problem - Detonation occurs when the fuel beyond the flame front initiated by
the sparkplug burns. This is also called autoignition or knocking.
•Octane rating proportional to the detonation temperature.
•Higher octane allows higher compression.
•An enormous search found lead, in the form of tetraethyl lead, Pb(C2H5)4,
inhibits detonation. More on this later.
16. C. Timing
Definition of Crank angle, advance vs. retard
Image
• Combustion takes time, about 5 ms.
• Combustion should occur at Top Dead Center (TDC), therefore
spark must precede piston.
• The higher the engine speed (RPM's) the more advanced the
spark must be. Vacuum or centrifugal advance.
• As lower octane fuel is used, the spark must be retarded. Effectively
reduces compression thus reducing power and fuel economy.
• Retarding the spark reduces the maximum and end temperatures
of combustion and thus reduces both CO and NO formation.
17. Image
D. Fuel
An octane rating of 100 means the same antiknock properties as isooctane (2,3,4-
trimethyl-pentane). Without lead in the fuel more aromatic and branched HC must
be mixed into the fuel. But these species are more reactive with respect to
photochemical O3 formation.
Fuel Lead
To produce higher octane gasoline from n-heptane (cheap gasoline) add the
following:
0.8 g Pb per gal. produces 100 octane fuel
0.4 g Pb per gal. produces 90 octane fuel
18. In the United States, lead in gasoline has been phased out altogether, but some of
the developing world still uses lead. Lead forms a solid oxide ash after
combustion, and fouls sparkplugs. To prevent the formation of ash on the plugs,
scavengers such as 1,2-dibromoethane (CH2Br-CBrH2) were added to the fuel.
These cause the burned lead to form halides such as Pb(Br) 2 which stay in the
vapor phase longer, and can act as a valve lubricant for some older cars.
Unfortunately, 1,2-dibromoethane is carcinogenic.
Where does the lead go?
•At 20 MPH 90 % of the lead goes onto the exhaust system; 10 % is expelled out
the tailpipe.
•At 70 MPH 90 % of the lead is expelled.
•Most of the lead falls as particles to the ground within 100m of roadways.
19. Lead is an insidious, cumulative poison. High serum (blood) lead has
been linked to reduced intellect, although the research is controversial.
Symptoms are hard to distinguish because they include anemia,
constipation, and abdominal pain, in short the malaise of modern man.
In California cities in 1974 the atmospheric lead concentration was
about 1.5 g/m3. The clean air background is about 0.01 g/m3.
Essentially all the lead in the air was from automobiles. By 1987 most
American cities had a lead content below 1 g/m3; the ambient air
quality standard is 1.5 g/m3 for an annual average.
20. Diesel Engines
There are no sparkplugs in a diesel engine. The fuel is injected at the
time of maximum compression (near TDC) and the heat of compression
causes combustion.
Diesel Engines have no throttle on the air.
Detonation impossible.
Low octane, "cheap," fuel may be used.
Compression must be higher (ca. 18:1 vs. 9:1 for Otto cycle).
Improved efficiency, but bigger and heavier engine block required.
Fuel mix is leaner, i.e. < 1.0.
Low CO and HC, but high NOx.
Lots of particles including soot and PAH.
21. III. Exhaust Emissions
a) Hydrocarbons
Some fuel remains unburned even after combustion; why? The
Temperature at the time of combustion is 2500 - 3000 C, but the walls of
the cylinder are around 200 C. The exhaust starts at 1000 C, but cools
quickly.
Poor mixing and absorption of HC into oil on walls creates a quench
zone.
HC are concentrated in the first and last components of the exhaust.
The NO profile is opposite.
To control HC emissions from the quench zone, the surface to volume
ratio should be kept to a minimum, but that reduces stroke and
compression.
22. b) Carbon Monoxide
CO2 CO + 1/2 O2
Keq = e(-G/RT)
The process becomes kinetically limited as expansion occurs. The
formation of CO is quick, but the removal is slower, especially at
temperatures below about 1000 K. Thus the [CO] is close to the [CO]
calculated by the above equilibrium method based on the temperature of
the exhaust gases at the end of expansion.
Image
29. Major advantages, cont.
* Diesel fuel (longer HC chains) is safer than gasoline in many applications. Although
diesel fuel will burn in open air using a wick, it will not explode and does not release a
large amount of flammable vapor. The low vapor pressure of diesel is especially
advantageous in marine applications, where the accumulation of explosive fuel-air
mixtures is a particular hazard. For the same reason, diesel engines are immune to vapor
lock.
* For any given partial load the fuel efficiency (mass burned per energy produced) of a
diesel engine remains nearly constant, as opposed to petrol and turbine engines which use
proportionally more fuel with partial power outputs.
* They generate less waste heat in cooling and exhaust.
* Diesel engines can accept super- or turbo-charging pressure without any natural limit,
constrained only by the strength of engine components. This is unlike petrol engines,
which inevitably suffer detonation at higher pressure.
* The carbon monoxide content of the exhaust is minimal.
* Biodiesel is an easily synthesized, non-petroleum-based fuel (through
transesterification) which can run directly in many diesel engines, while gasoline engines
either need adaptation to run synthetic fuels or else use them as an additive to gasoline e.g.,
ethanol added.
30. Diesel engines, Major disadvantages:
• Diesel engines are larger, heavier and more expensive than spark ignited engines.
• Tolerances on valves and rings stricter due to higher compression.
• Noise
• Greater NOx and soot generation
31. Take Home Messages for Internal Combustion Engines.
1.Generate most of the CO and NOx in N America.
2.Four stroke spark ignited engines generate a lot of CO and
substantial NOx.
3.Two-stroke spark ignited engines generate aerosols, CO,
VOC’s, but little NOx.
4.Diesel engines run hot and lean and generate NOx and soot,
but little CO.
32. The Role of Internal Combustion in gaseous
pollution and Photochemical Smog
Formation
The Automobile
Seinfeld Chapt. 3
Wark and Warner Chapt. 10
4. Exhaust Emissions
c) Nitric Oxide, NO
The formation of NO is controlled by kinetics, not thermodynamic
equilibrium. High temperatures favor the formation of NO, and as the
exhaust gases cool the NO is frozen out because the reformation of N2 and
O2 is slow. See Wark and Warner section 8.4. Our objective here is to
derive an expression for the rate at which [NO] approaches the
equilibrium concentration, [NO]eq .
33. The Zeldovich Mechanism (1946)
N2 + O2 ↔ 2NO
Derive an expression for the rate of NO formation.
Equilibrium Calculation
Keq = exp(-G /RT) = (PNO )2/(PN2 PO2)
The limit to the formation of NO is the slow rate of N2 dissociation, which
is hindered by a large positive G. Oxygen dissociates more readily.
N2 2N Go = +217.8 kcal/mole
Keq = 10-158
O2 2O Go = +110.8 kcal/mole
Keq = 10-81
34. We can represent the formation of NO as a two step process.
O + N2 ↔ NO + N (1)
N + O2 ↔ NO + O (2)
----------------------
N2 + O2 ↔ 2NO (NET)
d[NO]/dt = k1[O][N2] - k-1 [NO][N] + k2 [N][O2] - k-2 [NO][O] (I)
We will assume that N is in steady state. This is not the same as assuming it
is in thermodynamic equilibrium.
35. Yakov Borisovich Zel'dovich
Awarded the Order of Lenin (1949)
d[N]/dt = k1[O] [N2] - k-1 [NO][N] - k2[N][O2] + k-2 [NO][O]
k1[O] [N2] + k-2[NO][O]
[N]ss = --------------------------------
k-1[NO] + k2[O2]
[O] { k1[N2] + k-2[NO] }
[N]ss = --------------------------------- (II)
k-1[NO] + k2[O2]
37. In a qualitative sense, at combustion temperature Reaction 1 is fast;
Reaction 2 is fast if there is any O2 around, and Reactions -1 and -2 are
slow. So the formation of NO is much faster than the destruction. As the
temperature drops, O atoms react with each other to reform O2, preventing
Reaction -2 from removing much NO:
O + O + M O2 + M†
The superscript dagger represents translational kinetic energy.
In deriving a quantitative expression for the rate of formation of NO,
the following relations will prove useful. Remember that rate constants
are much harder to measure than thermodynamic properties, thus
thermodynamic data are generally better (more accurate) than kinetic data.
Anywhere we can substitute Keq for k, we will.
39. For a given temperature, Equation IV can be integrated to yield an
expression for the concentration of NO as a function of time, but this is a
tedious process. See Wark and Warner, p. 384. The result is:
[NO]t = [NO]eq ( 1 - (exp(-Mt))1/2 )
Where [NO]eq is the equilibrium concentration of NO and
M = 5.7E15 T -1 P1/2 exp(-58400/T) s-1
Note that M is a strong function of temperature, but not pressure. We have
assumed that Reactions 1 and 2 control, that the temperature is constant
throughout the process, and that N2 and O2 are present at a ratio of 40:1. The
actual process is very complicated because the temperature does not remain
constant.
40. CONCLUSIONS Tuning to Reduce Automotive Pollution Emissions
The kinetics of CO formation and destruction are rapid. The emission of
CO follows thermodynamic equilibrium, and is regulated by the temperature at
the end of combustion. With slow kinetics, NO is seldom in thermodynamic
equilibrium, and the emission is regulated more by the maximum combustion
temperature.
A) Air-Fuel-Mixture
AFR POWER ECONOMY CO/HC NOx
LEAN LOW HIGH LOW HIGH
RICH HIGH LOW HIGH LOW
41. B) Compression
Increases power and reduces CO, but puts structural demands on the
engine, and requires higher octane fuel to prevent knocking. Higher octane
fuel cannot be produced with lead or the catalytic converters will be poisoned.
High octane fuel without lead is more reactive with respect to photochemical
ozone formation.
C) Timing
For maximum power, combustion should take place at the point of
maximum compression, therefore the spark is usually advanced, and occurs
before top dead center. But if a low octane fuel is used with an engine that has
the spark advanced for maximum power, knocking occurs. By retarding the
spark, the octane demand of the engine is reduced. Retarding the spark also
lowers both the maximum temperature and the end temperature of combustion,
reducing both NO and CO production.
42. D) Exhaust gas Recycling
Adding exhaust, rich in relatively inert CO2, N2O and N2, to
the combustion mixture reduces the temperature enough to
help reduce NO production.