Effects of the addition of ethanol and cetane number improver on the combustion and emission characteristics of a compression ignition engine

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1 Effects of the addition of ethanol and cetane number improver on the combustion and emission characteristics of a compression ignition engine Y Ren*, Z-H Huang, D-M Jiang, W Li, B Liu, and X-B Wang State Key Laboratory of Multiphase Flow in Power Engineering, Xi an Jiaotong University, Xi an, People s Republic of China The manuscript was received on 4 January 2007 and was accepted after revision for publication on 27 February DOI: / JAUTO Abstract: Combustion and emission characteristics of a direct-injection diesel engine fuelled with diesel ethanol blends were investigated. The results show that the ignition delay and the premixed combustion duration increase, while the diffusive combustion duration and the total combustion duration decrease with increase in the oxygen mass fraction in the blends. The addition of 0.2 per cent volume fraction of cetane number improver (isoamyl nitrite) could mean that the ignition delay and the premixed combustion duration of the fuel blends with 10 vol % ethanol fraction recover to those of diesel fuel. Meanwhile, with the increase in the ethanol fraction in the fuel blends, the centre of the heat release curve moves closer to the top dead centre. The brake specific fuel consumption increases, while the diesel equivalent brake specific fuel consumption decreases with increase in the ethanol fraction. The exhaust smoke concentration increases and exhaust nitrogen oxide (NO x ) concentration decreases on prolonging the fuel delivery advance angle for both diesel fuel and the blended fuels. For a specific fuel injection advance angle, the exhaust smoke concentration shows a large decrease and the exhaust NO x concentration a small decrease on ethanol addition. Keywords: combustion, emission, diesel, ethanol, oxygenated fuel blends 1 INTRODUCTION The advantages of a diesel engine compared with a gasoline engine are the fuel economy benefits and high power output; however, the high nitrogen oxides (NO x ) and smoke emissions are still considered the main obstacles for its increasing application with growing concern in environmental protection and implementation of more stringent exhaust gas regulations; therefore, further reduction in engine emissions becomes one of the major tasks in engine development. However, it is difficult to reduce NO x and smoke simultaneously in the traditional diesel engine owing to the trade-off relationship between NO x and smoke. One promising approach to solve *Corresponding author: School of Energy and Power Engineering, Institute of Internal Combustion Engines, Xi an Jiaotong University, Xi an, , People s Republic of China. renyi@mailst.xjtu.edu.cn this problem is to use the oxygenated fuels or to add oxygenate additives in diesel to provide more oxygen during combustion. In the application of pure oxygenated fuels, Fleisch et al. [1], Kapus and Ofner [2], and Sorenson and Mikkelsen [3] have studied dimethyl ether (DME) in a modified diesel engine, and their results showed that the engine could achieve ultra-low-emission prospects without fundamental change in combustion systems. Huang et al. [4] investigated the combustion and emission characteristics in a compression ignition engine with DME and found that the DME engine has a high thermal efficiency, short premixed combustion, and fast diffusion combustion duration, and their work was to realize low-noise smoke-free combustion. Kajitani et al.[5] studied the DME engine by delaying the injection timing to reduce both smoke and NO x emissions. Practically, using some oxygenate compounds in pure diesel fuel to reduce engine emissions without JAUTO516 F IMechE 2008 Proc. IMechE Vol. 222 Part D: J. Automobile Engineering

2 1078 Y Ren, Z-H Huang, D-M Jiang, W Li, B Liu, and X-B Wang modifying the engine design seems to be a more attractive approach. Huang et al. [6] tested gasoline oxygenate blends in a spark-ignited engine and obtained a satisfactory result on emission reduction [6]; these workers [7 9] also investigated the combustion and emission characteristics of diesel oxygenate blends in a compression ignition engine. Murayama et al. [10] investigated the emissions and combustion of diesel dimethyl carbonate blends with exhaust gas recirculation (EGR). Ajav et al. [11] studied diesel ethanol blends for emission reduction and Huang et al. [12] investigated the engine performance and emissions of diesel engine fuelled with diesel methanol blends. Miyamoto et al. [13] and Akasaka and Sakurai [14] also conducted research on diesel combustion improvement and emission reduction by the use of various types of oxygenated fuel blend. In addition, McCormick et al.[15] studied the exhaust emissions of a heavy-duty diesel engine operated using several diesel oxygenated blends. Ethanol is a promising biomass fuel, which can be produced from crops. Ethanol has a high oxygen content and an abundant source; thus it is regarded as a better oxygenate additive or a good alternative fuel in engines. Previous investigations revealed that the reduction in particulate emissions and toxic gas pollutants could be achieved when using diesel ethanol blends [16 18]; however, these previous studies mainly focused on the experimental results under different engine conditions (engine speed and engine load) and used a specific proportion of ethanol in blends. As the information is very important for the clarification of combustion phenomenon and application of such blends, further investigation needs to be conducted, especially on a quantitative scale. These quantitative results are expected to supply more information on engine combustion fuelled with oxygenated fuels versus oxygen mass fraction in the blends and to provide more practical measures for the improvement in combustion and reduction in emissions of engine fuelled with diesel oxygenate blends. Based on the present authors previous analysis, the objective of this study is to investigate engine combustion and emission characteristics of diesel ethanol blends with cetane number (CN) improver, extending understanding of the combustion and emission characteristics of diesel ethanol blends and providing practical guidance for engine optimization. 2 FUEL PREPARATION AND APPROACH In this study, diesel fuel is the base fuel while ethanol is used as the oxygenate additive. A CN improver was used to recover the CN of the blends as ethanol has a low CN. A small fraction of surfactant, which is composed of carbon, hydrogen, and oxygen, was used to make the blends uniform and stable. Four blends without CN improver, designated E5, E10, E15, and E20, were prepared in which the volume fractions of ethanol in the diesel ethanol blends are 5 per cent, 10 per cent, 15 per cent, and 20 per cent respectively, and those with 0.2 per cent volume fraction of CN improver (isoamyl nitrite) were designated E5A, E10A, E15A, and E20A respectively. The base fuel is diesel fuel (E0). The fuel properties are given in Table 1 and Table 2, as well as in Fig. 1. It can be seen from Fig. 1 that adding 0.2 per cent CN improver made little difference to the blended fuels. In the experiment, the above eight fuel blends and pure diesel fuel were tested in a direct-injection (DI) diesel engine. The original fuel delivery advance angle of the engine is 25u crank angle (CA) before top dead centre (BTDC), and the specifications of the test engine are listed in Table 3. The initial time of the nozzle valve lifting was measured with a needlelift-detecting apparatus. An FQD-201B smoke meter was used to measure the exhaust smoke, and the exhaust gases (NO x, carbon monoxide, and hydrocarbons) were measured with a AVL DiGas 4000 light emission tester. The cylinder pressure and emissions were recorded under various engine conditions, and combustion analysis was performed on the basis of the cylinder pressure information. Furthermore, comparisons in combustion and emissions were conducted among these blends to clarify the behaviours of engine fuelled with diesel ethanol blends. 3 RESULTS AND DISCUSSION 3.1 Combustion characteristics The heat release rate dq b /dq is calculated using the formula Table 1 Fuel properties of diesel and ethanol Base fuel Oxygenates fuel Types of fuel Diesel Ethanol Density (g/cm 3 ) Lower heating value (MJ/kg) Heat of evaporation (kj/kg) Self-ignition temperature (uc) CN 45 8 Carbon (wt %) Hydrogen (wt %) Oxygen (wt %) Proc. IMechE Vol. 222 Part D: J. Automobile Engineering JAUTO516 F IMechE 2008

3 Effects of addition of ethanol and CN improver on a compression ignition engine 1079 Fuel Ethanol in the blends (vol %) Table 2 Lower heating value (MJ/kg) Fuel properties of the diesel ethanol blended fuels Heat of evaporation (kj/kg) Carbon (wt %) Hydrogen (wt %) Oxygen (wt %) E E E5A E E10A E E15A E E20A dq b dq ~p C p dv R dq z C V V dp R dq z dq W dq ð1þ where the heat transfer rate is given as dq W dq ~h cat{t ð W Þ ð2þ where the heat transfer coefficient h c uses the Woschni heat transfer coefficient [18]. The diesel-equivalent b.s.f.c. b eq and effective thermal efficiency g et are calculated respectively from the formula ðhuþ b eq ~b blends e ð3þ ðhuþ diesel g et ~ 3:6 106 ð4þ ðhuþ diesel b eq The CA Q c of the centre of heat release curve is determined from the formula Q c ~ ÐQ e Q s ÐQ e Q s ðdq b =dqþq dq ðdq b =dqþdq ð5þ The ignition delay is defined as the time interval from the initial time of the nozzle valve lifting (i.e. the start of fuel injection) to the initial time of the rapid pressure rise (it is regarded as the start of combustion); the premixed combustion duration is the time interval from the start of combustion to the time of the first trough on the heat release rate curve; the diffusive combustion duration is the time interval from the time of the first trough on the heat release rate curve to the end of combustion; the total combustion duration is the duration from the start of combustion to the end of combustion. Figure 2 gives the heat release rate of the diesel ethanol blends. The results show that for the same engine load (b.m.e.p.), engine speed, and fuel delivery advance angle, the initial combustion phase gives changes, owing to the addition of ethanol. Moreover, the maximum rate of heat release increases with increase in the ethanol mass fraction in the blends, and this value gives a low value in the case of CN improver addition compared with the value without the CN improver. This indicated that the CN has a large influence on the maximum rate of heat release. A long ignition delay and better evaporation of ethanol increase the fraction of combustible mixture prepared during the period of ignition delay, contributing to the increase in the maximum rate of heat release. In addition, a similar curve is revealed in the early stage of combustion between fuel E0 and fuel E10A, and similar behaviours are also presented for fuel E5 and fuel E15A, and for fuel E10 and fuel E20A. This indicated that the addition of 0.2 vol % of CN Fig. 1 Mass fraction of the fuel blends Table 3 Engine specifications Bore 100 mm Stroke 115 mm Displacement 903 cm 3 Compression ratio 18 Shape of combustion chamber v shape in the bottom of the bowl in piston Rated power; speed 10.5 kw; 2000 r/min Nozzle hole diameter 0.3 mm Nozzle opening pressure 19 MPa Number of nozzle holes 4 JAUTO516 F IMechE 2008 Proc. IMechE Vol. 222 Part D: J. Automobile Engineering

4 1080 Y Ren, Z-H Huang, D-M Jiang, W Li, B Liu, and X-B Wang Fig. 2 Heat release rate of the fuel blends improver (isoamyl nitrite) in the blended fuels could mean that the ignition delay recovers to those with 10 vol % ethanol addition. Compared with fuel E0, the heat release curves of fuel E10A finished early, indicating the decrease in diffusive combustion duration, and this would be the oxygen enrichment by ethanol addition. Figure 3 illustrates the ignition delay of the blends versus the oxygen mass fraction in the blended fuels. For a specific fuel delivery advance angle, the ignition delay shows an increase with increase in the oxygen mass fraction in the blends, and adding a CN improver into the blends can mean that the ignition delay of the fuel blends recovers to those with 10 vol % less ethanol addition. The ignition delay increases on delaying the fuel delivery advance angle for both diesel fuel and diesel ethanol blends. The behaviours can be explained by the decrease in Proc. IMechE Vol. 222 Part D: J. Automobile Engineering JAUTO516 F IMechE 2008

5 Effects of addition of ethanol and CN improver on a compression ignition engine 1081 Fig. 3 Ignition delay versus oxygen mass fraction CN and the increase in the heat of evaporation of the blended fuels with ethanol addition. The premixed combustion duration and the amount Q premixed of heat release in the premixed combustion duration versus the oxygen mass fraction in the blended fuels are shown in Fig. 4; the results showed that the premixed combustion duration and the amount of heat release in the premixed combustion duration increase with the advancement of fuel delivery advance angle for both diesel fuel and the diesel ethanol blends, and this is due to the increase in ignition delay with the advancement of fuel delivery advance angle. For a specific fuel delivery advance angle, the premixed combustion duration and the amount of heat release in the premixed combustion duration increase with increase in the oxygen mass fraction in the blended fuels. Two factors are considered to cause this behaviour: one is the increase in the amount of combustible mixture prepared during the ignition delay since the addition of ethanol increases the ignition delay, and the other is that the addition of ethanol would promote the formation of a combustible mixture due to the Fig. 4 Premixed combustion duration and amount of heat release in premixed combustion duration versus oxygen mass fraction oxygen enrichment and better volatility of ethanol. The addition of a CN improver can decrease the premixed combustion duration of diesel ethanol blends; the results show that the premixed combustion duration can recover to those with 10 vol % less ethanol addition on the addition of 0.2 vol % of CN improver. This behaviour is similar to that of ignition delay for the blended fuels. This suggests that the change in the CN of the blended fuels strongly influences the ignition delay and the premixed combustion duration for diesel ethanol blends. The diffusive combustion duration and the amount Q diffusive of heat release in the diffusive combustion duration versus the oxygen mass fraction in the fuel blends are given in Fig. 5. The results reveal that the diffusive combustion duration and the amount of heat release in the diffusive combustion duration decease with increase in the oxygen mass fraction in the blended fuels, and this is regarded as diffusive combustion improvement due to oxygen enrichment by adding oxygenates. The improvement in diffusive combustion is favourable to a reduction in JAUTO516 F IMechE 2008 Proc. IMechE Vol. 222 Part D: J. Automobile Engineering

6 1082 Y Ren, Z-H Huang, D-M Jiang, W Li, B Liu, and X-B Wang Fig. 5 Diffusive combustion duration and amount of heat release in diffusive combustion duration versus oxygen mass fraction Fig. 6 Total combustion duration versus oxygen mass fraction exhaust smoke. The total combustion duration versus fuel delivery advance angle is illustrated in Fig. 6. The blended fuels presented a slight decrease with increase in the oxygen mass fraction for fuels with and without the CN improver. At the same fuel delivery advance angle, more fuel should be injected for diesel ethanol blends compared with pure diesel fuel to obtain the same engine load (b.m.e.p.) since the heat value of diesel ethanol blends is less than that of pure diesel fuel, and the value will decrease with the increase in the ethanol fraction in the blends. However, the total combustion duration shows a slight decrease with increase in the oxygen mass fraction (or ethanol mass fraction) in the blends. As explained above, the enrichment of oxygen owing to the ethanol addition is helpful to the improvement in diffusive combustion, decreasing the diffusive combustion duration, and finally contributing to the reduction in the total combustion duration. Figure 7 exhibits the CA Q c of the centre of the heat release curve versus the oxygen mass fraction in blended fuels. The figure shows the decrease in Q c with increase in the oxygen mass fraction in blended fuels. This can be explained as follows; the improvement in the diffusive combustion phase and the decrease in the total combustion duration contribute to making the heat release process closer to the top dead centre (TDC). The b.s.f.c. and the diesel equivalent b.s.f.c. b eq versus the oxygen mass fraction in the blended fuels are plotted in Fig. 8. The results show that the b.s.f.c. of blended fuels increases with increase in the oxygen mass fraction in fuel blends. However, the diesel-equivalent b.s.f.c. decreases with increase in the oxygen mass fraction in the fuel blends. With respect to the behaviour of the b.s.f.c. versus the oxygen mass fraction, two aspects should be taken into account. One aspect is that the addition of the ethanol in the blended fuels would result in the increase in the amount of fuel burned in the premixed burn phase, and the centre of heat release curve moves close to the TDC, leading to the decrease of b.s.f.c. Another aspect is the decrease in the heating value of the blended fuels with Proc. IMechE Vol. 222 Part D: J. Automobile Engineering JAUTO516 F IMechE 2008

7 Effects of addition of ethanol and CN improver on a compression ignition engine 1083 Fig. 7 CA Q c centre of the heat release curve versus oxygen mass fraction Fig. 8 B.s.f.c. and diesel-equivalent b.s.f.c. b eq increase in the ethanol fraction, in order to obtain the same b.m.e.p. and engine speed; more fuel should be injected and this increases the b.s.f.c. The comprehensive results showed the increase in the b.s.f.c. with increase in the ethanol fraction. However, the diesel-equivalent b.s.f.c. b eq would decrease with increase in the ethanol fraction owing to the improvement in combustion. The effective thermal efficiency g et is in an inverse ratio to the dieselequivalent b.s.f.c. as indicated in equation (4), and so they must reflect the same phenomenon. Therefore, the effective thermal efficiency g et versus the oxygen mass fraction in the blended fuels is given in Fig. 9, and the result shows that g et increases with increase in the ethanol fraction in the blended fuels. The NO x concentration of diesel ethanol blends versus the oxygen mass fraction of the blended fuels is illustrated in Fig. 10. The results show that the NO x concentration of the fuel blends increases with the advancement of fuel delivery advance angle, while NO x gives a slight decrease with increase in the oxygen mass fraction (ethanol mass fraction) in the blended fuels. In the early case, the increase in premixed combustion causes the increase in the NO x concentration while, in the late case, the temperature drop due to the high value of ethanol evaporation leads to the decrease in the NO x concentration. Figure 11 gives the smoke concentration and its reduction rate versus the oxygen mass fraction in the blended fuels. The smoke reduction rate is defined by the formula [K value (diesel) 2 K value (blends)]/k value (diesel). The purpose of adding the oxygenate to diesel fuel is expected to decrease the engine smoke by providing more oxygen and making it burn completely. The results clearly show that the exhaust smoke could be decreased markedly on the addition of ethanol to diesel fuel with and without the CN improver. This suggests that the oxygen-containing fuel blends can reduce the rich spray region and promote the post-flame oxidation of the formed soot. The results also reveal that the smoke concentration of the blended fuels without CN improver gives a lower value than those with a CN improver. The addition of CN improver decreases the ignition delay and the amount of fuel burned during the premixed combustion phase and increases the JAUTO516 F IMechE 2008 Proc. IMechE Vol. 222 Part D: J. Automobile Engineering

8 1084 Y Ren, Z-H Huang, D-M Jiang, W Li, B Liu, and X-B Wang Fig. 9 Effective thermal efficiency versus oxygen mass fraction amount of fuel burned during the diffusive combustion phase. This causes the increase in the engine smoke on CN improver addition. The smoke reduction rate increases with increase in the oxygen mass fraction (ethanol fraction). For the same engine speed and engine load (b.m.e.p.), engine smoke gives a high reduction rate with increase in the oxygen mass fraction in the blended fuels in the case of a small fuel delivery advance angle, and this reveals that the ethanol addition has a large influence on smoke reduction in the case of a small fuel delivery advance angle. The relationships between NO x and smoke of diesel ethanol fuel blends at various b.m.e.p. and fuel delivery advance angles are plotted in Fig. 12. Unlike the engine operating on pure diesel fuel, which has a trade-off behaviour between NO x and smoke, a flat NO x smoke trade-off curve is presented when operating on the diesel ethanol fuel blends. Simultaneous reduction in NO x and smoke could be observed with ethanol addition at high engine loads. The results also reveal that NO x Fig. 10 Exhaust NO x concentration versus oxygen mass fraction concentration shows a decrease, and smoke concentration an increase, on delaying the fuel delivery advance angle. 4 CONCLUSIONS A stabilized diesel ethanol blend was used to study the combustion characteristics and emissions of the oxygenated blends in a compression ignition engine, and the main results were summarized as follows. 1. Ignition delay increases with increase in the ethanol fraction owing to the decrease in CN of the blends. Premixed combustion duration and the amount of heat release in the premixed combustion duration increase, while the diffusive combustion duration and the amount of heat release in the diffusive combustion duration decrease with increase in the ethanol fraction in the fuel blends. 2. The addition of 0.2 vol % CN improver (isoamyl nitrite) can mean that the ignition delay and premixed combustion duration of fuel blends with 10 vol % ethanol fraction recover to those of Proc. IMechE Vol. 222 Part D: J. Automobile Engineering JAUTO516 F IMechE 2008

9 Effects of addition of ethanol and CN improver on a compression ignition engine 1085 Fig. 12 Relationship between NO x and smoke of the blended fuels diesel fuel. The CN of the blended fuels is a key influencing factor on the ignition delay and the premixed combustion duration for diesel ethanol blends. 3. The centre of the heat release curve moves close to the TDC with increase in the oxygen mass fraction in blended fuels. The diesel equivalent b.s.f.c. decreases with increase in the ethanol fraction. 4. A flat NO x smoke trade-off curve exists when operating on the diesel ethanol fuel blends. Utilization of diesel ethanol blends combined with delaying the fuel delivery advance angle can simultaneously decrease both the smoke and the NO x emissions. ACKNOWLEDGEMENTS Fig. 11 Exhaust smoke concentration and its reduction rate versus oxygen mass fraction This study was supported by the National Natural Science Fund of China ( and ) and the Doctoral Foundation of Xi an Jiaotong University. The authors acknowledge the teachers and students of Xi an Jiaotong University for their help with the experiment. The authors also express their thanks to their colleagues at Xi an Jiaotong Uni- JAUTO516 F IMechE 2008 Proc. IMechE Vol. 222 Part D: J. Automobile Engineering

10 1086 Y Ren, Z-H Huang, D-M Jiang, W Li, B Liu, and X-B Wang versity for their helpful comments and advice during the manuscript preparation. REFERENCES 1 Fleisch, T., McCarthy, C., and Basu, A. A new clean diesel technology: demonstration of ULEV emissions on a Navistar diesel engine fueled with dimethyl ether. SAE Trans., 1995, 104(4), Kapus, P. and Ofner, H. Development of fuel injection equipment and combustion system for DI diesels operated on dimethyl ether. SAE Trans., 1995, 104(4), Sorenson, S. C. and Mikkelsen, S. E. Performance and emissions of a liter direct injection diesel engine fueled with neat dimethyl ether. SAE Trans., 1995, 104(4), Huang, Z. H., Wang, H. W., and Chen, H. Y. Study on combustion characteristics of a compression ignition engine fueled with dimethyl ether. Proc. Instn Mech. Engrs, Part D: J. Automobile Engineering, 1999, 213(6), Kajitani, Z., Chen, L., and Konno, M. Engine performance and exhaust characteristics of directinjection diesel engine operated with DME. SAE Trans., 1997, 106(4), Huang, Z., Miao, H., Zhou, L., and Jiang, D. Combustion characteristics and hydrocarbon emissions of a spark ignition engine fuelled with gasoline oxygenate blends. Proc. Instn Mech. Engrs, Part D: J. Automobile Engineering, 2000, 214(3), Huang, Z. H., Lu, H. B., Jiang, D. M., Zeng, K., Liu, B., Zhang, J. Q., and Wan, X. B. Combustion behaviors of a compression-ignition engine fuelled with diesel/methanol blends under various fuel delivery advance angles. Bioresource Technol., 2004, 95(3), Huang, Z. H., Lu, H. B., Jiang, D. M., Zeng, K., Liu, B., Zhang, J. Q., and Wan, X. B. Engine performance and emissions of a compression ignition engine operating on the diesel methanol blends. Proc. Instn Mech. Engrs, Part D: J. Automobile Engineering, 2004, 217(4), Huang, Z. H., Jiang, D. M., Zeng, K., Liu, B., and Yang, Z. L. Combustion characteristics and heat release analysis of a DI compression ignition engine fueled with diesel dimethyl carbonate blends. Proc. Instn Mech. Engrs, Part D: J. Automobile Engineering, 2003, 217(7), Murayama, T., Zheng, M., and Chikahisa, T. Simultaneous reduction of smoke and NO x from a DI diesel engine with EGR and dimethyl carbonate. SAE paper , Ajav, E. A., Singh, B., and Bhattacharya, T. K. Experimental study of some performance parameters of a constant speed stationary diesel engine using ethanol diesel blend as fuel. Biomass Bioenergy, 1999, 17, Huang, Z. H., Lu, H. B., Jiang, D. M., Zeng, K., Liu, B., Zhang, J. Q., and Wang, X. B. Engine performance and emissions of a compression ignition engine operating on the diesel methanol blends. Proc. Instn Mech. Engrs, Part D: J. Automobile Engineering, 2004, 218(4), Miyamoto, N., Ogawa, H., and Obata, K. Improvements of diesel combustion and emissions by addition of oxygenated agents to diesel fuels: influence of properties of diesel fuels and kinds of oxygenated agents. JSAE Rev., 1998, 19(2), Akasaka, Y. and Sakurai, Y. Effect of oxygenated fuel on exhaust emission from DI diesel engines. Trans. JSME., Ser. B, 1996, 63(609), McCormick, R. L., Ross, J. D., and Graboski, M. S. Effect of several oxygenates on regulated emissions from heay-duty diesel engines. Environmental Sci. Technol., 1997, 31, Satgé de Caro, P., Mouloungui, Z., Vaitilingom, G., and Berge, J. Ch. Interest of combining an additive with diesel ethanol blends for use in diesel engines. Fuel, 2001, 80, He, B. Q., Shuai, S. J., Wang, J. X., and He, H. The effect of ethanol blended diesel fuels on emissions from a diesel engine. Atmos. Environ., 2003, 37, Can, O., Celikten, I., and Usta, N. Effects of ethanol addition on performance and emissions of a turbocharged indirect injection diesel engine running at different injection pressures. Energy Conversion Managmt., 2004, 45, APPENDIX Notation ATDC b.m.e.p. b.s.f.c. b e b eq BTDC dq b /dq (Hu) blends (Hu) diesel Q premixed Q diffusive TDC g et after top dead centre brake mean effective pressure (MPa) brake specific fuel consumption brake specific fuel consumption (g/ kw h) diesel equivalent brake specific fuel consumption (g/kw h) before top dead centre heat release rate with crank angle (kj/degree crank angle) lower heating value of diesel oxygenates blends (MJ/kg) lower heating value of pure diesel fuel (MJ/kg) amount of heat release during premixed combustion duration amount of heat release during diffusive combustion duration top dead centre effective thermal efficiency Proc. IMechE Vol. 222 Part D: J. Automobile Engineering JAUTO516 F IMechE 2008

11 Effects of addition of ethanol and CN improver on a compression ignition engine 1087 h fd fuel delivery advance angle (degrees crank angle before top dead centre) Q c crank angle of the centre of the heat release curve (degrees crank angle after top dead centre) JAUTO516 F IMechE 2008 Proc. IMechE Vol. 222 Part D: J. Automobile Engineering

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