This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
A Stepped-Piston Two-Stroke Engine for High Altitude Applications
Annotation ability available
Sector:
Language:
English
Abstract
The crankcase-scavenged two-stroke-cycle engine is preferred in cases where low weight and high power output are paramount requirements. These qualities are most important in small pilotless aircraft. It was found that the main problem in the use of two-stroke cycle engines for this purpose, is a sharp decrease in the engine power with the increase in altitude. This is attributed not only to the low density of the ambient air, but also to the deterioration of the efficiency of the gas exchange process.
In order to improve the engine performance at high altitude, it is proposed here to employ a stepped-piston engine. The engine is constructed of a stepped piston and a single stepped cylinder thus forming three compartments; a power, a compression and a crankcase compartment. In this arrangement, the fresh charge is compressed in the compression compartment before it enters the crankcase compartment.
A computer program, the MICE (Modeling Internal Combustion Engines) program, was modified to consider this type of engine, and used to study the effect of various parameters on the engine performance. A geometry optimization for maximal performance was performed.
It is shown that a significant improvement in the engine performance map at high altitudes can be obtained with the stepped-piston engine. The optimized engine can function well at 5,000 ft (∼1,500 m) higher than the conventional engine, while its specific fuel consumption at low altitudes is well below the conventional one, thus increasing the aircraft mission range.
Recommended Content
Authors
Topic
Citation
Sher, E. and Zeigerson, M., "A Stepped-Piston Two-Stroke Engine for High Altitude Applications," SAE Technical Paper 940400, 1994, https://doi.org/10.4271/940400.Also In
Two-Stroke Engines: Theoretical and Experimental Investigations
Number: SP-1019; Published: 1994-03-01
Number: SP-1019; Published: 1994-03-01
References
- SAE recommended practice engine test code SAE Handbook 24.08. 1979
- Automotive Handbook Bosch 1989
- Watanabe, I. Kuroda, H. “Effect of atmospheric temperature on the power output of a two-stroke cycle crankcase compression gasoline engine” SAE 810295 1981
- Sher, E. “The effect of atmospheric conditions on the performance of an air-borne two-stroke spark ignition engine” Proc. Instn. Mech. Engrs. 198 239 251 1984
- Harari, R. Sher, E. “The effect of ambient pressure on the performance map of a two-stroke SI engine” SAE 930503 1993
- Annand, W.J.D. Roe, G.E. Gas flow in the internal combustion engine Foulis G.T. Sparkford 1974
- Annand, W.J.D. “Heat transfer in the cylinders of reciprocating internal combustion engines” Proc. Instn. Mech. Engrs. 177 973 989 1963
- Hires, S.D. Tabaczynski, R.J. Novae, J.M. “The predictions of ignition delay and combustion intervals for a homogeneous charge, spark ignition engine” SAE 780232 1978
- Metghalchi, M. Keck, J.C “Burning velocities of mixtures of air with methanol, isooctane, and indolene at high pressure and temperature” Combustion and Flame 48 191 210 1982
- Sher, E. Harari, R. “A simple and realistic model for the scavenging process in a crankcase-scavenged two-stroke cycle engine” J. of Power and Energy 205 129 137 1991
- Patton, K.J. Nitschke, R.G. Heywood, J.B. “Development and evaluation of a friction model for SI engines” SAE 890836 1989