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Potential Benefits in Heavy Duty Diesel Engine Performance and Emissions from the Use of Variable Compression Ratio
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 03, 2006 by SAE International in United States
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Worldwide demand for reduction of automotive fuel consumption and carbon dioxide emissions results in the introduction of new diesel engine technologies. A promising technique for increasing the power density of reciprocating engines, improving fuel economy and curtailing engine exhaust emissions is the use of variable compression ratio (VCR) technology. Several automotive manufacturers have developed prototype vehicles equipped with VCR gasoline engines. The constructive pattern followed to alter the compression ratio varies with the manufacturer. The implementation of VCR technology offers two main advantages: the reduction of CO2 emissions due to optimal combustion efficiency in the entire range of engine operating conditions and the increase of power concentration due to high boosting of a small engine displacement (i.e., engine downsizing). However, the aforementioned benefits concern mainly spark ignition engines, where the increase of compression ratio during part-throttle operation results in a noticeable reduction of brake specific fuel consumption (bsfc) because of their thermodynamic operating cycle and the relatively low CR used. On the other hand, the application of VCR technology in heavy-duty diesel engine, if any, is extremely limited whereas is not expected to provide a similar benefit since their compression ratio is already higher than spark-ignition engines. In addition, high values of compression ratio are necessary in diesel engines to ensure proper auto-ignition of injected diesel fuel. The variation of compression ratio in heavy-duty diesel engines confronts with the excessive increase of peak combustion pressure (Pmax) mainly at high engine loads. Specifically, studies conducted in the past by the present research group dealing with the application of “internal measures” in diesel engines, revealed the possibility for reducing bsfc and NOx emissions without significant penalty on soot using advanced injection timing and high EGR rates. However, this resulted in a considerable increase of peak combustion pressure, which generates serious structural problems at high engine load. Therefore, the use of a variable compression ratio in heavy-duty diesel engines can be a promising technique to control peak combustion pressure. In this case, a high compression ratio can be maintained at part load while a lower one can be used at full load where peak firing pressure is a problem. However, it is still doubtful if the expected improvement in fuel economy will be overwhelmed by the manufacturing complexity and the subsequent cost aggravation and reliability implications, which will accompany the application of this technology in diesel engines. For this reason, in the present study, an engine simulation model is used to investigate potential benefits in specific fuel consumption of a heavy duty DI diesel engine by varying its compression ratio. Additionally, the implications on engine exhaust emissions and peak combustion pressure from the implementation of VCR technology at both part and full load conditions are examined. The main objective of the study is to identify the necessary variation of compression ratio with engine operating conditions to achieve optimum fuel consumption, avoid excessive peak combustion pressures, and assess its repercussions on engine out emissions with regard to future emission standards. This analysis will facilitate the determination of a possible “optimized” variation law of compression ratio with engine speed and load for heavy-duty diesel engines. The results of this theoretical examination in conjunction with serious technical issues accompanying the variation of compression ratio will judge the applicability of this technique in heavy-duty diesel engines.
CitationHountalas, D., Zannis, T., and Mavropoulos, G., "Potential Benefits in Heavy Duty Diesel Engine Performance and Emissions from the Use of Variable Compression Ratio," SAE Technical Paper 2006-01-0081, 2006, https://doi.org/10.4271/2006-01-0081.
- Grebe U-D. and Imarisio R., “Gasoline or diesel engine: the race is on!”, FISITA World Automotive Congress, Barcelona, Spain, Paper No F2004V097, 2004.
- Binder K. and Schwarz V. “Present and future of heavy duty engine strategies for compliance to the emission legislation”, Conf. on Thermo- and Fluid Dynamic Processes in Diesel Engines (THIESEL), Valencia, Spain, 2002.
- Hountalas D.T., Mavropoulos G.C., Zannis T.C. and Schwarz V., “Possibilities to achieve future emission limits for HD DI diesel engines using internal measures”, SAE Paper No 2005-01-0377, 2005.
- Hountalas D.T., “Controlling nitric oxide and soot in heavy duty diesel engines using internal measures”, FISITA World Automotive Congress, Barcelona, Spain, Paper No F2004V262, 2004.
- Hountalas D.T., Kouremenos D.A., Mavropoulos G.C., Binder K.B. and Schwarz V. “Multi-zone combustion modeling as a tool for DI diesel engine development - Application for the effect of injection pressure”, SAE Paper No 2004-01-0115, 2004.
- Hountalas D.T., Kouremenos D.A., Binder K.B., Raab A., and Schnabel M.H. “Using advanced injection timing and EGR to improve DI diesel engine efficiency at acceptable NO and soot levels”, SAE Paper No 2001-01-0199, 2001.
- Payri F., Benajes J., Molina S. and Riesco J.M. “Reduction of pollutant emissions in a HD diesel engine by adjustment of injection parameters, boost pressure and EGR”, SAE Paper No 2003-01-0343, 2003.
- Abou Al-Sood M.M., Abdel-Latif A.A., Abdel-Rahim Y.M. and Ibrahim A.M., “Optimum compression ratio variation of a 4-stroke, direct injection diesel engine for minimum bsfc”, SAE Paper No 1999-01-2519, 1999.
- Abou Al-Sood M.M., Abdel-Latif A.A., Abdel-Rahim Y.M. and Ibrahim A.M., “Optimum compression ratio variation of a 4-stroke, direct injection diesel engine for maximum brake power and torque and minimum soot and NOx emissions”, SAE Paper No 1999-01-2728, 1999.
- “PLN-based improved combustion for low emissions (PICE)”, GROWTH, G3RD-CT-2000-00283, 2004.
- Drangel H., Olofsson E. and Reinmann R., “The variable compression (SVC) and the combustion control (SCC) - Two ways to improve fuel economy and still comply with world-wide emission requirements”, SAE Paper No 2002-01-0996, 2002.
- Schwaderlapp M., Habermann K. and Yapici K.I., “Variable compression ratio - A design solution for fuel economy concepts”, SAE Paper No 2002-01-1103, 2002.
- Mendler C. and Gravel R., “Variable compression ratio engine”, SAE Paper No 2002-01-1940, 2002.
- Roberts M., “Benefits and challenges of variable compression ratio (VCR)”, SAE Paper No 2003-01-0398, 2003.
- Moteki K., Aoyama S., Ushijima K., Hiyoshi R., Takemura S., Fujimoto H. and Arai T., “A study of variable compression ratio system with a multi-link mechanism”, SAE Paper No 2003-01-0921, 2003.
- Rabhi V., Beroff J. and Dionnet F., “Study of a gear-based variable compression ratio engine”, SAE Paper No 2004-01-2931, 2004.
- Takahashi N., Aoyama S., Moteki K. and Hiyoshi R., “A study concerning the noise and vibration characteristics of an engine with multiple-link variable compression ratio mechanism”, SAE Paper No 2005-01-1134, 2005.
- Ladommatos N. and Balian R.A., “Combustion in a direct injection diesel engine with increased clearance volume”, Proc. Instn Mech Engrs, Vol. 204, No D01690, pp.187-197, 1990.
- Rychter T.J., Teodorczyk A., Stone C.R., Leonard H.J., Ladommatos N. and Charlton S.J., “A theoretical study of a variable compression ratio turbocharged diesel engine”, Proc Instn Mech Engrs, pp. 227-238, 1992.
- Sobotowski R.A., Porter B.C. and Pilley A.D., “The development of a novel variable compression ratio, direct injection diesel engine”, SAE Paper No 910484.
- Jung A. and Assanis D.N., “Multi-zone DI diesel spray combustion model for cycle simulation studies on engine performance and emissions”, SAE Paper No 2001-01-1246, 2001.
- Launder B.E. and Spalding D.B. Mathematical Models of Turbulence, Academic Press, London & NY, 1972.
- Annand W.J.D., “Heat transfer in the cylinders of reciprocating internal combustion engines”, Proc. Instn Mech Engrs, Vol. 177, pp. 973-990, 1963.
- Heywood J.B. Internal Combustion Engine Fundamentals, McGraw-Hill, NY, 1988.
- Dent J.C. and Derham J.A. “Air motion in a four-stroke direct injection diesel engine”, Proc. Instn Mech. Engrs, Vol. 188, pp. 269-280, 1974.
- Ramos J.I. Internal Combustion Engine Modelling, Hemisphere, New York, 1989.
- Borman G.L. and Johnson J.H. “Unsteady vaporization histories and trajectories of fuel drops injected into swirling air”, SAE Paper No. 598C, National Powerplant Meeting, Philadelphia PA, 1962.
- Kadota T., Hiroyasu H. and Oya H. “Spontaneous ignition delay of a fuel droplet in high pressure and high temperature gaseous environments”, Bulletin JSME, Vol.19, Issue 130, 1976.
- Lavoie G.A., Heywood J.B. and Keck J.C. “Experimental and theoretical study of nitric oxide formation in internal combustion engines”, Combust Sci and Technol, Vol. 1, pp. 313-326, 1970.
- Nishida K. and Hiroyasu H. “Simplified three-dimensional modelling of mixture formation and combustion in a D.I. diesel engine”, SAE Paper No 890269, 1989.