International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
INTERNATIONAL JOURNAL OF MECHANICAL EN...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) ...
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30120140501005

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 1, January (2014), pp. 44-56 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com IJMET ©IAEME A COMPREHENSIVE REVIEW ON COMBUSTION OF COMPRESSION IGNITION ENGINES USING BIODIESEL K. Vijayaraj1*, A. P. Sathiyagnanam2 1* Research Scholar, Department of Mechanical Engineering Annamalai University, Annamalai Nagar -608002 (T.N) India 2 Assistant Professor, Department of Mechanical Engineering Annamalai University, Annamalai Nagar -608002 (T.N) India ABSTRACT The world today is confronted with a twin crisis of fossil fuel depletion and environmental degradation. Rapid depletion of petroleum derived fuels has forced the researchers to find out alternative fuels for IC engines. Biodiesel is an alternative fuel for conventional diesel engines and can be used without major modification of the engines. When compared to diesel, biodiesel has a higher cetane number which results in shorter ignition delay and longer combustion duration and hence results in low particulate emissions. The combustion of CI engine is a complex process due to its combustion mechanism. The combustion characteristics of an engine are defined by parameters such as cylinder pressure, maximum rate of pressure rise, heat release, cumulative heat release, ignition delay and combustion duration. Analysis of combustion characteristics is significant because it provides the important information which in turn helps in interpreting the engine performance and exhaust emissions. This paper reviews the combustion analysis of compression ignition engines using biodiesel. It is found that the ignition delay for biodiesel seems to be less when compared to diesel. Moreover, it reveals that the heat release rate is more during the diffusion combustion for biodiesel and its blends than diesel. Similarly a marked difference is seen in the cumulative heat release rate and combustion duration. Keywords: Diesel Engine, Biodiesel, Combustion, Heat Release Rate, Cylinder Pressure, Ignition Delay and Combustion Duration. 44
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME 1. INTRODUCTION Compression ignition engines have become an indispensable part of modern life style because of their major role in transportation. The compression ignition engines are not liked by many passenger car owners due to noisy combustion and emission of black smoke with bad odour. The CI engines are more fuel efficient and consequently emit lower greenhouse gas, carbon dioxide emissions when compared to SI engines. The demand for petroleum based fuel has increased, the resources of the conventional fossil fuel are non-renewable and the remaining global ones are sufficient to meet demand up to 2030 [Kjarstad and Johnson (2009)]. Therefore there arises a need to develop alternative fuels which are cheaper, environmentally acceptable and considered to reduce the dependency on fossil fuel. Rudolf Diesel, the inventor of diesel engine, is the pioneer who used peanut oil as an alternative fuel for diesel engine at the 1900 World exhibition in Paris. In India, a lot of research activities are going on in the field of production of biodiesel, mainly from non-edible sources and subsequently testing their suitability in diesel engine either in the form of blending with conventional diesel or neat biodiesel. Biodiesel has already been commercialized in the transport sector and can be used in diesel engines with little or no modification [Graboske and McCormick (1998)]. Many reports are available on engine performance, emission and combustion evaluation with non-edible biodiesel. Most of the combustion analysis reveals lower ignition delay, early heat release though biodiesel has slightly higher viscosity and lower volatility. However, results vary considerably depending upon the type of biodiesel used, engine configuration and test conditions. 2. COMBUSTION IN CI ENGINE Most heavy duty engines are CI engines due to their high fuel efficiency and capability to burn heavier fuel. A heterogeneous fuel-air mixture is created by injection of fuel in the hot compressed air in the cylinder, which is ignited as the temperature of compressed air is higher than the self ignition temperature of the fuel. High injection pressures in the range of 200 to 2000 bar or even higher are used depending upon the engine design. To ignite the fuel and initiate combustion, the temperature of air around 800 K or more is attained by compression of air to a pressure close to 45 – 60 bar. The engines operating in this form of combustion are commonly termed as Compression Ignition engines. A common name for these engines is “Diesel engine” [Pundir (2010)]. The fuel injection consists of one or several high velocity fuel jets injected at high pressure through small orifices in the injector nozzle that can penetrate far into the combustion chamber. The fuel is injected either directly in the combustion chamber contained in a bowl in the piston crown or in a small combustion chamber contained in the cylinder head which is attached to the main chamber in the cylinder. The density of air at the time of injection is in the range of 15 to 25 kg/m3 and the liquid fuel jet leaves the nozzle at a velocity of 100 to 300 m/sec. Fuel vapours and air mix forming combustible mixture initially at some locations. The air temperature being higher than the self ignition temperature of fuel, after elapse of a short interval between the start of injection the fuel gets auto-ignited and combustion begins. The time interval between the start of injection and combustion is known as “ignition delay”. After the start of combustion, the flame spreads rapidly in the combustible mixture formed during the delay period. This phase is usually termed as “premixed combustion phase”. The combustion of the fuel injected after the start of combustion, depends how quickly it gets evaporated and mixes with air. During this period, turbulent diffusion processes govern the fuelair mixing and combustion rate. This period is termed as “diffusion combustion phase”. 45
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME Air Fuel Boost pressure, Temperature, EGR Fuel properties (CN, Density, Viscosity, etc) Inlet Port Design Swirl, turbulence Injection system Injection pressure, rate, timing, duration Combustion Chamber Design (Bowl/chamber geometry) Swirl Squish Turbulence Spray formation, Drop size distribution, Cone angle, Spray penetration, Wall jet, Fuel evaporation Fuel-Air Mixing Combustion Ignition delay, Ignition, Pre-mixed and Diffusion combustion, Heat release rate Fig. 1. Diesel Combustion Process, Key Design, Operating and Combustion Parameters The combustion in CI engine is quite different from the SI engines. The combustion in SI engine starts at one point with consequently slow rise in pressure and generated flame at the point of ignition propagates through the mixture for burning of the mixture, whereas in CI engine, the combustion takes place at a number of points simultaneously with the consequent rapid rise in pressure and number of flames generated are also many. To burn the liquid fuel is more difficult as it is to be evaporated; it is to be elevated to ignition temperature and then burn. Design combustion process, key design, operating and combustion parameters are shown in fig. (1). 46
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME 3. STAGES OF COMBUSTION IN CI ENGINE Harry Ricardo has investigated the combustion in a CI engine and divided the same into following four stages. 1. Ignition delay or delay period. 2. Uncontrolled combustion. 3. Controlled combustion. 4. After burning. Crank angle Fig.2. Four Stages of combustion process in a CI engine The fig. (2) Shows the four stages of the combustion process in a CI engine [Ramalingam (2008)]. The curved line ABCG represents compression and expansion of air charge in the engine cylinder when the engine is being motored without fuel injection. The curve is mirror symmetry with respect to TDC line. The curve ABCDEFH shows the pressure trace of an actual engine. 3.1. Delay period In actual engine, the fuel injection begins at point B during the compression stroke. The injected fuel does not ignite immediately and takes some time to ignite. Ignition sets in at point C. During the crank travel from B to C, the pressure in the combustion chamber does not rise above the compression curve. The period corresponding to the crank angle B to C is called “delay period or ignition delay”. 3.2. Uncontrolled combustion At the end of delay period i.e. at point C, the fuel starts burning. At this point, good amount of fuel would have already entered and got accumulated inside the combustion chamber. This fuel charge is surrounded by hot air. The fuel is finely divided and evaporated. Majority of the fuel burns with an explosion like effect. This instantaneous combustion is called “uncontrolled combustion “and this combustion causes a rapid pressure rise. If more fuel is present in the cylinder at the end of 47
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME delay period and undergoes rapid combustion, when ignition sets in the peak pressure attained will be greater. During this combustion, the piston is around TDC and is almost stand still. Too rapid pressure rise and severe pressure impulse at this position of the piston will result in combustion noise called “Diesel Knock”. The rate at which the uncontrolled combustion takes place depends upon the following factors: 1. The quantity of fuel in the combustion chamber at point C. This quantity depends upon the rate at which the fuel is injected during the delay period and the duration of ignition delay. 2. The condition of fuel that has got accumulated in the combustion chamber at the point C. The rate of combustion during the crank travel C to D and the resulting rate of pressure rise determine the quietness and smoothness of operation of the engine. 3.3. Controlled combustion High temperature and pressure prevail within the combustion chamber during the period C to D because of uncontrolled combustion which has taken place previously. Hence, after the point D, the fuel burns as soon as it enters the combustion chamber. After the point D, the fuel which has not yet burned during C to D and the fuel which continues to be injected burns. During the period D to E, combustion is gradual. Further, by controlling the rate of fuel injection complete control is possible over the rate of burning. Therefore, the rate of pressure rise is controllable and hence this stage is called “Controlled Combustion”. The period corresponding to the crank travel D to E is called the period of Controlled Combustion. The rate of burning during the period of controlled combustion depends on the following criteria: 1. 2. 3. 4. Rate of fuel injection during the period of controlled combustion. The fineness of atomization of the injected fuel. The uniformity of distribution of the injected fuel in the combustion chamber. The amount and distribution of the oxygen left in the combustion space for reaction of the injected fuel. At point E, the injection of fuel ends. 3.4. After burning At the last stage, i.e., between E and F, the fuel that is left in the combustion space when the fuel injection stops is burnt. This stage of combustion is called “After burning”. Increasing excess air or air motion will shorten after burning. 4. DIFFICULTY OF COMBUSTION IN CI ENGINE In SI engines, air and fuel are taken in during the suction stroke in a properly mixed and vaporized form and compressed during the compression stroke. At the end of the compression stroke, a spark is produced in the combustion chamber by an electrical device. The spark initiates combustion, since the charge is in the form of a homogeneous mixture of air and vapour; the flame spreads throughout the whole charge. There is little or no difficulty in achieving good combustion. In the case of CI engines, air alone is taken in during the suction stroke and compressed during the compression stroke to a compression ratio of 16 to 20. The temperature and pressure of the air increases and at the end of compression, fuel is injected into the combustion chamber. The hot air ignites the fuel and hence combustion takes place. 48
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME Fig. 3. Cylinder Pressure-Crank angle history and sequence of process in 4-stroke CI engine Usually, fuel is injected around 10o to 20o before TDC and terminated at about 10o after TDC.As such; the whole combustion process occupies about 30o of crank rotation around TDC. If the engine is running at 1500 rpm, then the time available for combustion will be equal to30 × 60 / 360 × 1500 i.e., 1 / 300 sec. Within this small interval of time whatever fuel that has been injected must mix thoroughly with the air, get itself vaporised and burn in the most efficient form [Ramalingam (2008)]. Hence combustion in a CI engine is a much more difficult and complicated affair when compared to the combustion in a SI engine. The Fig (3) shows the Cylinder PressureCrank angle history and sequence of processes in a CI engine. A few important differences from SI engine combustion are: 1. The combustion occurs in heterogeneous air-fuel mixture with local fuel-air ratio varying widely from nearly zero to infinity. 2. Combustion in fuel-rich pockets results in soot formation and appearance of black smoke in the exhaust, a characteristic of CI engines. 3. As the fuel is injected just before combustion begins, there is not enough time to form end gas zones containing the fuel-air mixture. The engine compression ratio is not limited by knock and thus high compression ratio can be used in CI engines improving fuel efficiency when compared to SI engines. 5. COMBUSTION ANALYSIS OF CI ENGINE The combustion of the engine is an intricate process because of the combustion mechanism. The main parameters used for analyzing the characteristics of the combustion process are cylinder pressure, ignition delay, heat release rate (HRR), combustion duration, etc., [Enweremadu and Rutto (2010)]. All these parameters are based on the variation of cylinder pressure and hence the combustion parameters can be calculated based on the cylinder pressure data. Other important combustion parameters such as combustion duration and intensity can be estimated from the heat release variation over an engine cycle. In addition, the HRR can be used for identifying the start of 49
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME combustion, indicating the ignition delay for different fuels, showing the fraction of fuel burned in the premixed mode and differences in combustion rates of fuels [Brunt, et al. (1998)]. The HRR can be computed by a simplified approach which can be derived from the first law of thermodynamics [Sudhir, et al. (2007)] as expressed in equation (1). ௗொ ௗఏ ൌ ଵ ఊିଵ ቂߛܲ ௗ௏ ௗఏ ൅ܸ ௗ௉ ௗఏ ቃ (1) where, dQ/dθ is the heat release rate across the system boundary into the system, P is the in-cylinder gas pressure, V is the in-cylinder volume, γ is the ratio of specific heat ranges from 1.3 to 1.5 for heat release analysis and θ is the crank angle. Moreover, P (dV/dθ) is the rate of work transfer done by the system due to system boundary displacement. Fig. 4. DI engine heat release rate identifying different diesel combustion phases The fig. (4) represents heat release rate versus crank angle of a diesel engine. It indicates that the combustion can be divided into three distinguishable stages [Heywood (1988)]. The first stage is premixed period where the rate of burning is very high and the combustion time is short (for only a few crank angle degrees) as well as the cylinder pressure increases rapidly. The second stage is the main heat release period corresponding to a period of gradually decreasing HRR and lasting about 30 CA degrees, namely mixing controlled period. The third stage is the late combustion period which corresponds to the tail of heat release diagram in which a small but distinguishable HRR throughout much of the expansion stroke. The fig. (5) Shows the Cylinder Pressure and heat release rate versus Crank angle of diesel engine. The pressure variation in the engine cylinder plays an important role in the analysis of the combustion characteristics, combustion noise of any fuel and the sound quality related to combustion parameters [Pruvost, et al. (2009)]. An analysis of fuel combustion characteristics is important because it provides the above important information which in turn helps in interpreting engine performance and exhaust emissions [Gogoi, et al. (2013)]. 50
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME Fig.5. Cylinder Pressure and heat release rate of diesel engine. 5.1. Cylinder pressure The cylinder pressure refers to the maximum pressure obtained in the cylinder during the end of the power stroke. It depends on the change in volume due to piston movement, temperature, ignition delay and spray envelope of the injected fuel. Normally, the cylinder pressure curve is drawn with reference to the crank angle and it shows the start and end of the combustion. Crank angle from 325 - 425 degrees are taken for the study where the rise and fall of the pressure occurs. study 5.2. Heat release rate (HRR) The concept of heat release is important to understand the combustion process of CI engine. It is defined as the rate at which the chemical energy of the fuel is released by the combustion process and it can be calculated from the cylinder pressure versus crank angle data [Heywood (1988)]. Heat release rate measures the conversion of chemical energy of fuel into the thermal energy by combustion. This directly affects the rate of pressure rise and accordingly the power produced. The heat release rate is used to identify the start of combustion, the fraction of fuel burned in the premixed mode and differences in combustion rates of fuels. 5.3. Rate of pressure rise An analysis of the rate of pressure rise is indispensable in engine study because it is possible to determine how smoothly the combustion progresses in the combustion chamber from the observation of the rate of pressure rise. It is necessary that the maximum rate of pressure rise should be as low as possible for reduced engine noise and increased engine life [Ganesan (2007)] Ganesan (2007)]. 5.4. Cumulative heat release (CHR) CHR is the integration of the NHRR results and it indicates the amount of energy spent for a given output. Cumulative heat release increases towards the later part of the combustion process for all the fuel. 51
  9. 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME 5.5 .Ignition delay Ignition delay is defined as the time period between SOI and SOC. Ignition delay is the single biggest variable to choose an injection accurately and posits a major challenge to emissions as well. Delay is primarily governed by chemical properties and the physical evaporation delay is significant when the engine is cold. Cetane Number measures how shortly after the start of injection the fuel starts to burn (auto ignites). The engine requires an increasingly higher cetane number fuel to start easily in the cold condition. A change in cetane content directly affects the ignition delay. A fuel with a high cetane number starts to burn shortly after it is injected into the cylinder; it has a short ignition delay period. Conversely, a fuel with a low cetane number resists auto ignition and has a longer ignition delay period. It is a significant parameter in determining the knocking characteristics of CI engines. 5.6. Injection timing Combustion completeness depends on correct timing. At normal engine conditions, the minimum delay occurs with the start of injection at about 10o to 15o BTDC. The increase in the delay with earlier or later injection timing occurs because the air temperature and pressure changes significantly close to TDC. If injection starts earlier, the initial air temperature and pressure are lower so the delay will increase. If injection starts later (closer to TDC), the temperature and pressure are initially slightly higher but then decreases as the delay proceeds. The most favourable conditions for ignition lie in between [Heywood (1988)]. 5.7. Combustion duration The total time taken for the complete burning of the air-fuel mixture in the CI engine is called “combustion duration”. The combustion duration on the other hand comprises the main combustion phase, in which the flame front move quickly through the combustion chamber and high percentage of the chemical energy of the fuel is released. It is governed by the chemical properties and environmental factors (pressure and temperature). 6. COMBUSTION OF BIODIESEL Both physical and chemical properties can affect combustion characteristics of biodiesel and its blends. There are two distinct phases in the combustion process of biodiesel in CI engines, the premixed and diffusion phases. During the ignition delay or the time when the fuel is being injected and before the ignition starts, the fuel and air mix form pockets of a fuel-rich premixed combustible mixture. Upon ignition, the premixed pockets rapidly react, quickly consuming all the available oxygen. The biodiesel fuel itself is oxygenated. Once all the oxygen in the premixed pockets has been consumed, the flame transitions into a diffusion mode. The premixed phase of combustion is shorter than diffusion phase. NOx emissions correlate well with the amount of fuel consumed during the premixed phase of combustion, even though there is a relatively low flame temperature due to locally fuel-rich conditions. The heat release during the premixed phase of combustion acts to preheat the reactants for the diffusion phase of combustion, increasing the flame temperature and ultimately increasing NOx emissions. It is to be noted that biodiesel has a higher boiling point range than diesel fuel, which ranges from approximately 300-350oC, whereas diesel fuel ranges from approximately 185-345oC. Because of this difference, biodiesel has been proved by a number of researchers to have a larger heat release than diesel fuel during the premixed phase of combustion, thus causing, at least in part, higher NOx emissions. Biodiesel fuel blends are more efficient during the fuel and air-mixing process, so for a biodiesel blend to have the same amount of fuel consumed during premixed combustion as the baseline diesel fuel, the biodiesel blend requires less time and thus displays a higher cetane number 52
  10. 10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME (CN). The CN of biodiesel can differ substantially depending on the composition and the age of the fuel. It is typically between 46 and 57 and can exceed to 70, if the fuel is highly oxidized. Further, increasing the CN of biodiesel by using cetane improving additives seems to be effective in reducing NOx emissions from biodiesel. Biodiesel causes an advance in the fuel injection timing because it has a higher bulk modulus than diesel fuel. Moreover, biodiesel improves combustion effectively, especially at low speed and high load and decreases most of the pollutants except NOx. Since biodiesel fuel experienced a shorter ignition delay and vaporized more slowly than diesel fuel, the combustible mixture produces a smaller combustion peak. The rate of heat release decreases with higher concentration of biodiesel. Fig (6) shows the rate of heat release for diesel, biodiesel blend (B20) and biodiesel (B100). It is vivid that B100 has the lowest rate of heat release when compared to the other two fuels. Fig. 6. The rate of heat release for biodiesel 7. EFFECT OF BIODIESEL ON THE COMBUSTION PARAMETERS A detailed experimental description of combustion evolution in a diesel engine is extremely complex because of the simultaneous formation and oxidation of air-fuel mixture [Senatore, et al. (2000)]. However, an effort has been made to study the effect of biodiesel on different parameters like maximum combustion pressure and corresponding crank angle, rate of pressure rise and its corresponding crank angle, start of fuel injection, ignition delay and most importantly the heat release rate of the engine. There is an increase in cylinder peak (or maximum) pressure with B100 compared to diesel. This is due to the difference in physical and chemical properties of the biodiesel which advances the combustion process when burns in an unmodified diesel engine [Shah, et al. (2010)]. This may be due to the shorter ignition lag of B100. The maximum rate of pressure rise (MRPR) is more in case 53
  11. 11. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME of diesel because diesel fuel has a longer ignition delay. Longer ignition delay causes an increase in the rate of pressure rise because a greater amount of fuel burns with extreme rapidity during the premixed combustion period [Murugan, et al. (2008)]. Biodiesel is less compressible than diesel, so develops faster pressure in the fuel injection system. As a result, the propagation of pressure wave is faster in biodiesel than diesel fuel even at the same nominal pump timing, resulting in earlier injection of biodiesel with higher pressure and rate [Shah, et al. (2010)]. The ignition delay (θd) is shorter in the case of biodiesel and its blends when compared to diesel fuel, is due to the difference in their cetane number. Biodiesel and its blend have a larger cetane number than that of diesel, resulting in earlier combustion [Shah, et al. (2009)]. Combustion duration for B100 is 53oCA and is minimum (46oCA) for diesel which may be due to lower diesel consumption. It has been found that the engine consumed more fuel during B100 operation and hence combustion also continued for a long period of time [Gogoi, et al. (2013)]. The different combustion characteristics such as ignition delay, ignition temperature and spray penetration of different biodiesel fuels have been reviewed in a detailed manner in the subsequent paragraph. Zhang and Van Gerpen (1996) reported the use of blends of methyl esters of soybean oil and diesel in a turbo-charged, four- cylinder, direct injection diesel engine modified with a bowl on piston and medium swirl type. They found that the blends gave a shorter ignition delay and similar combustion characteristics as diesel. Mohamed, et al. (1997) investigated the effect of the ignition delay period of jojoba methyl ester by conducting experiments in a shock tube test rig by varying the factors like equivalence ratio, ignition temperature and ignition pressure. They reported that the Ignition delay period for jojoba methyl ester was lower while the ignition temperature and ignition pressure were higher. Ali and Hanna (1997) studied the in cylinder pressure characteristics of a sixcylinder, direct injection, 306kW diesel engine using esters if methyl tallowate as fuel. Peak rate of heat release for the blend of diesel methyl tallowate was found to be lower than diesel. Yu, et al. (2002) compared the combustion characteristics of waste cooking oil with diesel in a direct injection diesel engine. Tashtoush, et al. (2003) investigated the combustion performance of ethyl esters of waste vegetable oil. Sinha and Agarwal (2005) investigated the combustion characteristics of rice bran oil in transport diesel engine. Saikishan, et al. (2007) attempted to find the cetane number based on the properties of the biodiesel by using simulation techniques. In their work, they analyzed the influence of the various fuel properties namely density, viscosity, flash and fire points on the cetane number of a biodiesel and its various blends. Szybist, et al. (2007) reported that biodiesel could alter the fuel injection and ignition processes whether neat or in blend form. CONCLUSION This comprehensive analysis on combustion of CI engine using biodiesel reveals that the maximum rate of pressure rise was less for B100 while the same was more for diesel fuel. The heat release rate was less for B100 during premixed combustion while this was more during diffusion combustion for B100 and its blends. Similarly the CHR values were higher for B100 and its blends during the period from SOC till the end of combustion but the values remained almost same with diesel towards the later part of combustion. Early pressure rise and heat release were an indication of lower ignition delay for the biodiesel. It was found that the ignition delay for B100 and its blends were less than that of diesel. Ignition delay for B100 being the lowest of them because of the oxygenated nature of the biodiesel. If the ignition delay is more, the fuel accumulation will be higher, resulting in peak pressure. This supports the results of maximum peak pressure with diesel and the lowest peak pressure in case of B100.The combustion duration of the biodiesel was more than that of diesel which may be due to higher fuel consumption. Fuel consumption was more for B100 when compared to diesel. 54
  12. 12. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] Brunt, MFJ. ; Rai, H.; Emtage, AL. (1998): The calculation of heat release energy from engine cylinder pressure data, SAE, No. 981052. Enweremadu, CC.; Rutto, HL. (2010): Combustion, emission and engine performance characteristics of used cooking oil biodiesel A Review, Renewable and sustainable Energy reviews, 14(9), pp.2863-2873. Ganesan, V. (2007). Internal Combustion Engines, 3rd ed., McGraw – Hill, New Delhi. Gogoi, T.K.; Sarma, A.K.; Misra, P.S.; Syed T.Haque. (2013): Combustion Analysis of Jatropha methyl ester and its ethanol and acetone blends in a diesel engine, International Journal of Emerging Technology and Advanced Engineering, 3, pp 51-57. Graboske, M.S.; McCormick, R.L. (1998): Prog Energy combustion science, 24, pp. 125 – 164. Heywood, J.B. (1988). Internal combustion engine fundamentals, McGraw – Hill, Newyork. Kjarstad, J.; Johnson, F. (2009): Resources and future supply of oil, Energy policy, 37, pp. 441-64. Mohamed Y Selim, Radwan, MS.; Dandoush, SK.; Kader, AMA. (1997): Ignition delay period of Jojoba diesel engine fuel, SAE, No. 972975. Murugan, S.; Ramaswamy,M.C.; Nagarajan, G.(2008):A Comparative study on the performance, emission and combustion studies of D1 Diesel engine using distilled tyre pyrolysis oil diesel blends, fuel, 87, pp.2111-2121. Pruvost, L.; Leclere, Q.; E Parizet. (2009): Diesel Engine Combustion and Mechanical NoiseSeparation using an Improved Spectrofilter Mechanical System and Signal Processing, 23 (7), pp. 2072-2087. Pundir, B.P. (2010). IC Engines: Combustion and Emissions, Narosa Publishing House Pvt.Ltd.New Delhi. Ramalingam, K.K. (2008). Internal Combustion Engines, 2nd ed., Scitech Publication pvt.Ltd. Chennai. Saikishan, S.; Vijay Manikandan Janakiraman; Jayanth Sekar; Lakshminarayana Rao, G.(2007): Prediction of cetane number of a biodiesel based on physical properties and a study of their influence on cetane number, SAE, No. 2007- 01-0077. Senatore, A.; Cardone, M.; Rocco, V.; Brati, M.V.(2000): Comparative analysis of combustion Process in D1 diesel engine fuelled with biodiesel and diesel fuel, SAE, No 2000-01- 0691. V.Narasiman, S.Jeyakumar, M.Mani and K.Rajkumar, “Impact of Combustion on Ignition Delay and Heat Release Curve of a Single Cylinder Diesel Engine using Sardine Oil as a Methyl Ester”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 150 - 157, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. Shah, A.N.; Yum-shen, GE. ; He Chao; Baluch, A.H. (2009): Effect of Biodiesel on the performance and combustion parameters of a turbocharged compression ignition engine, pak.J.Engg & Appl.Sci. 4, pp. 34-42. Sanjay Patil, “Effect of Injector Opening Pressure on Performance, Combustion and Emission Characteristics of C.I. Engine Fuelled with Palm Oil Methyl Ester”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 1, 2013, pp. 233 - 241, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. Shah, A.N.; Yunshan, G.; Chao, H. (2010): Combustion and Emission response by a heavy duty diesel engine fuelled with Biodiesel; An experimental study, MURJET, 29, pp. 195-204. 55
  13. 13. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 1, January (2014), © IAEME [19] Sinha, S.; Agarwal, AS.(2005): Combustion characteristics of Rice Bran oil derived biodiesel transportation diesel engine, SAE, No. 2005-26-354. [20] Sudhir, CV.; Sharma, NY. ; Mohanan, P. (2007): Potential of waste cooking oils as biodiesel feedstock, Emirates J Eng Res, 12(3), pp.69-75. [21] Szybist James, P.; Song Juhun; Alam Mahabubul; Boehman Andre´ L. (2007): Biodiesel combustion, emissions and emission control, Fuel Processing Technology, 88, (7), pp. 679-691. [22] Z. Ahmed, D. K. Mahanta, “Exergy Analysis of a Compression Ignition Engine”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 633 - 642, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. [23] Tashtoush Ghassan; Al-Widyan Mohamad I; Al-Shyoukh Ali, O. (2003): Combustion performance and emissions of ethyl ester of a waste vegetable oil in a water- cooled furnace”, Applied Thermal Engineering, 23, pp. 285–93. [24] Ali, Y.; Hanna, M.(1997): In-cylinder pressure characteristics of a DI heavy duty diesel engine on biodiesel fuel, SAE, No. 971683. [25] Yu, C.W.; Bari S.; Ameen, A. (2002): A comparison of combustion characteristics of waste cooling oil with diesel as fuel in a direct injection diesel engine, Proceedings of Institution of Mechanical Engineers Part D Journal of Automobile Engineering, 216, pp. 237–43. [26] Zhang, Y.; Van Gerpen, J. (1996): Combustion Analysis of Esters of Soybean Oil in a Diesel Engine, SAE, No. 960765. 56

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