This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Thermodynamic Evaluation of Variable Valve Timing
Annotation ability available
Sector:
Event:
SAE Brasil
Language:
English
Abstract
The optimization of valve train actuation for internal combustion engines through the fixed geometry camshaft is a compromise between the required torque, the fuel consumption, idle characteristics and exhaust emissions. Some automobile manufacturers, however, have already incorporated in some models the variable valve actuation; in these systems, the duration of intake process, valve overlapping or both can be modified by the engine operation condition.
Although experimental tests are the decisive ones, their costs can be minimized if it is possible to adopt some mathematical modeling of the engine physical phenomena in order to obtain qualitative tendencies. The analysis of the engine performance modifications associated with a variable camshaft actuation can be obtained - at least as a first approximation - through thermodynamic simulation models. Then the number of necessary experimental work can be reduced.
In this work the effects of variable valve actuation on the indicated horsepower the specific fuel consumption and the volumetric efficiency are discussed, using a thermodynamic engine model. The engine speed and load effects over the residual gas fraction, over the weak-spring indicator diagram and over other performance parameters are analyzed. Thermodynamic irreversibilities in the exhaust and intake processes are also evaluated through exergetic analysis, complementary to the usual engine analysis.
Recommended Content
Authors
Citation
Gallo, W., "Thermodynamic Evaluation of Variable Valve Timing," SAE Technical Paper 921479, 1992, https://doi.org/10.4271/921479.Also In
References
- ASMUS, T.W. Valve Events - Engine Operation SAE Trans . 820749 1982 2520 2533
- GALLO, W.L.R. Exergetic Analysis of Gasoline and Ethanol Fueled Engines State University of Campinas Brasil 1990
- GALLO, W.L.R MILANEZ, L.F. Exergetic Analysis of Ethanol and Gasoline Fueled Engines SAE Technical Paper Series 920809 SAE International Congress and Exposition Detroit feb. 24-28 1992
- HOHENBERG, G. Advanced Approaches for Heat Transfer Calculations SAE Trans . 790825 1979 2788 2806
- HAYWOOD, J.B. Pollutant Formation and Control in Spark Ignition Engines Prog. in Energy Comb. Sci. 1 1976 135 164
- KASTNER, L. J. WILLIAMS, T.J. WHITE, J.B. Poppet Inlet Valve Characteristics and Their Influence on the Induction Process Proc. Instn. Mech.Engrs 178 36 955 978 1963-1964
- LAFORGIA, D. FICARELLA, A. Poppet Valve Flow Characteristics in Internal Combustion Engines ASME 12 d Annual Energy-Sources Technology Conference and Exhibition Jan. 22-25 Houston 6 1989 33 43
- NISHIWAKI, K. SHIMAMOTO, Y. MIYAKE, K. Avera ge Heat Transfer Coefficients on a Cylinder Wall in the Intake and Exhaust Processes of Motoring Test Bull.JSME 22 174 1979 1796 1809
- SHERMAN, R.H. BLUMBERG, P.N. The Influence of Induction and Exhaust Processes on Emission and Fuel Consumption in the Spark Ignited Engine SAE Trans. 770880 1977 3025 3040
- STULL, D.R. PROPHET, H. JANAF Thermochemical Tables National Standard Reference Data System National Bureau of Standards 1971