Effect of EGR on the HCCI Engine Performance Using Biodiesel as a Fuel: Paper Example

1. Effect of Different Techniques on Combustion and Emissions of the HCCI Engine Using Biodiesel Fuels

1.1 Use of different fuel additives

Fuel additives are the compounds formulated to enhance the efficiency and quality of fuels. These additives act as the lubricants or the corrosion inhibitors and also increase the octane rating of the fuel. The use of these additives increases the compression ratios to improve the efficiency and power of the fuel. The fuel additives are available in various forms such as pills, liquid, and powder. According to Jimenez-Espadafor et al. (2012), fuels comprises different percentages of diesel, giving rise to B0, B30, B65 and B100, which indicates the mass percentage of the biodiesel used. The biodiesel blends used different exhibit viscosity, surface tension, density, and volatility which influences the spray development, injector dynamics, and droplets atomization affecting the liquid penetration thus the need for the additives (Leung, Wu & Leung, 2010).

Is your time best spent reading someone else’s essay? Get a 100% original essay FROM A CERTIFIED WRITER!

Save 25%

1.2 Exhaust gas recirculation (EGR)

The emission of NOx is restricted by the legislation of the various countries across the world. The NOx is a result of the combination of the oxygen gas and nitrogen gas in the combustion chambers of the engine. Reducing the NOx emission led to the adoption of the exhaust gas recirculation (Jimenez-Espadafor et al., 2012). The exhaust gas recirculation (EGR) process involves the recirculation of a controllable proportion of the exhaust from the engine into the intake air. The recirculation is achieved by the use of a valve to control the flow of the gas fuel.

1.3 Fuel injection strategies modification

According to Singh, Singh and Agarwal (2014), it is possible to attain low NOx and soot in an enhanced premixed combustion leading the emission of higher levels of hydrocarbons and carbon monoxide. The possibility is attainable when the engine cycles move to low-temperature combustions from the ultra-low carbon monoxide and hydrocarbon emissions in the high compression engines (Srihari, Thirumalini & Prashanth, 2017; Liu et al., 2017). Thus, the fuel efficiency is often compromised. Nonetheless, through the use of modifications such as single injection with heavy EGR and early multi-pulse injection of the fuel under low or medium loads of engine can greatly improve the efficiency of fuel.

1.4 Different Compression Rate

Compression ratio is vital in engines. A higher compression translates to more engine power due to its ability to extract more mechanical energy from the supplied air and fuel mixture. The higher compression ratio enables the mixture of the fuel and air to fit in a smaller area leading to evaporation and an eventual mixture of fuel droplets in the combustion chamber (He, 2016; Godino et al., 2018). The high compression engines result into greater power and require fuel of higher octane. Low octane and low-grade fuels lead to the detonation of the engine which causes severe and irreplaceable damage.

1.5 Combustion chamber geometry modification

The geometry of the combustion chambers is a key factor in the performance of an engine. The variations in the geometry even in the slightest amount may lead to an enormous change in its performance as well as its emission parameters (Jafarmadar & Nemati, 2017). The geometry modifications entail the modifications of the performance parameters, the combustion parameters, and the emission parameters (Kumar & Rehman, 2016). The slightest modifications of these parameters often lead to the sustainability of the biodiesel in the CI engines.

2. Combustion and Emission Characteristics of Biodiesel in the HCCI Engine

2.1 Effects of injection parameters on biodiesel combustion characteristics

The injection parameters such as pressure and timing have massive effects on the combustion of biodiesel. These parameters affect the combustion and emission within the cylinder more so the single cylinder common rail direct injection (CRDi) fueled using the waste cooking oil (WCO) biodiesel and the common commercial fuel (Sadaf et al., 2018). The timing injection parameter of the biodiesel is always high concerning the Indicated Specific Fuel Consumption (ISFC). Nonetheless, the peak cylinder pressure, as well as the peak heat release rate of the biodiesel, are always lower in the HCCI engines (Noh & No, 2017). The ignition delays also take longer in the various operating conditions. The use of biodiesel also results in a reduction of smoke, hydrocarbon, and carbon monoxide emissions.

2.2 Comparison of combustion pressure and heat release rate

According to Azad et al. (2016), the combustion pressure is directly proportional to the heat release rate. The biodiesel used experience different combustion stages. In these stages, the combustion starts early at the given engine loads. In lower loads, the heat releases us lower while in higher loads, the heat release is higher.

2.3 Effects of blending ratio and injection timing on the combustion characteristics

The injection timing on combustion parameters with the blend ratios of 5%, 10%, and 20% creates a negative improvement on the combustion of the engine. Achieving optimum combustion requires the injection timing to be done at 340 crank angle degree (Jiaqiang et al., 2017).

2.4 Effects of engine speed and EGR rate on the combustion characteristics

Engine speed is directly proportional to the combustion rates. On the other hand, the EGR, which is used in controlling the emission of NOx from the engines reduces the concentration of oxygen, which is a key element in combustion within the chambers thus its increase increases the combustion rates (Kozarac et al., 2014; Jamsran & Lim, 2016). Thus, directing the exhaust gases back into the combustion chambers with advanced timing in the injection of the engine increases the combustion durations.

2.5 Effect of multiple injections on the combustion characteristics

The injected sprays always exhibit different patterns depending on the strategy implemented. For multiple injections, the spray often develops faster as compared to single injections. The timing of these injections is also key for combustion as it may retard the process (Jafarmadar & Nemati, 2017).

References

Azad, A. K., Rasul, M. G., Khan, M. M. K., Sharma, S. C., & Bhuiya, M. M. K. (2016). Recent development of biodiesel combustion strategies and modelling for compression ignition engines. Renewable and Sustainable Energy Reviews, 56, 1068-1086.

Godino, J. A. V., Aguilar, F. J. J. E., & Garcia, M. T. (2018). Simulation of HCCI combustion in air-cooled off-road engines fuelled with diesel and biodiesel. Journal of the Energy Institute, 91(4), 549-562.

He, B. Q. (2016). Advances in emission characteristics of diesel engines using different biodiesel fuels. Renewable and Sustainable Energy Reviews, 60, 570-586.

Jafarmadar, S., & Nemati, P. (2017). Multidimensional modeling of the effect of exhaust gas recirculation on exergy terms in a homogenous charge compression ignition engine fueled by diesel/biodiesel. Journal of Cleaner Production, 161, 720-734.

Jamsran, N., & Lim, O. (2016). Effects of EGR and boosting on the auto-ignition characteristics of HCCI combustion fueled with natural gas. Journal of Natural Gas Science and Engineering, 35, 1015-1024.

Jimenez-Espadafor, F. J., Torres, M., Velez, J. A., Carvajal, E., & Becerra, J. A. (2012). Experimental analysis of low temperature combustion mode with diesel and biodiesel fuels: A method for reducing NOx and soot emissions. Fuel Processing Technology, 103, 57-63.

Jiaqiang, E., Pham, M., Zhao, D., Deng, Y., Le, D., Zuo, W., ... & Zhang, Z. (2017). Effect of different technologies on combustion and emissions of the diesel engine fueled with biodiesel: A review. Renewable and Sustainable Energy Reviews, 80, 620-647.

Kozarac, D., Vuilleumier, D., Saxena, S., & Dibble, R. W. (2014). Analysis of benefits of using internal exhaust gas recirculation in biogas-fueled HCCI engines. Energy conversion and management, 87, 1186-1194.

Kumar, P., & Rehman, A. (2016). Bio-diesel in homogeneous charge compression ignition (HCCI) combustion. Renewable and Sustainable Energy Reviews, 56, 536-550.

Leung, D. Y., Wu, X., & Leung, M. K. H. (2010). A review on biodiesel production using catalyzed transesterification. Applied energy, 87(4), 1083-1095.

Liu, H., Ma, X., Li, B., Chen, L., Wang, Z., & Wang, J. (2017). Combustion and emission characteristics of a direct injection diesel engine fueled with biodiesel and PODE/biodiesel fuel blends. Fuel, 209, 62-68.

Noh, H. K., & No, S. Y. (2017). Effect of bioethanol on combustion and emissions in advanced CI engines: HCCI, PPC and GCI mode-A review. Applied Energy.

Sadaf, S., Iqbal, J., Ullah, I., Bhatti, H. N., Nouren, S., Nisar, J., & Iqbal, M. (2018). Biodiesel production from waste cooking oil: An efficient technique to convert waste into biodiesel. Sustainable Cities and Society.

Singh, G., Singh, A. P., & Agarwal, A. K. (2014). Experimental investigations of combustion, performance and emission characterization of biodiesel fuelled HCCI engine using external mixture formation technique. Sustainable Energy Technologies and Assessments, 6, 116-128.

Srihari, S., Thirumalini, S., & Prashanth, K. (2017). An experimental study on the performance and emission characteristics of PCCI-DI engine fuelled with diethyl ether-biodiesel-diesel blends. Renewable Energy, 107, 440-447.