Performance and Efficiency Evaluation and Heat Release Study of a Direct-Injection Stratified-charge Rotary Engine 870445

A computer simulation which models engine performance of Direct Injection Stratified Charge (DISC) rotary engines has been used to study the effect of variations in engine design and operating parameters on engine performance and efficiency of an experimental Outboard Marine Corporation (OMC) rotary combustion engine. Engine pressure data have been used in a heat release analysis to study the effects of heat transfer, leakage and crevice flows. Predicted engine data is compared with experimental test data over a range of engine speeds and loads. An examination of methods to improve the performance of the rotary engine using advanced heat engine concepts such as faster combustion, reduced leakage and turbocharging is also presented.

THE DIRECT-INJECTION stratified-charge (DISC) Wankel rotary engine is currently being evaluated by NASA as a future advanced powerplant for light commercial and similar applications. The Wankel rotary engine offers attractive advantages over the reciprocating engines for use in small aircraft. These advantages include higher power to weight ratio, simpler and more compact shape, fewer moving parts, lower noise levels and less vibration. In addition, using direct-injection stratified-charge operation, the rotary engine can be designed for operation with jet-fuel or multi-fuel capability (1,2)*.

The purpose of this study is to examine the combustion rate and performance loss mechanisms of an experimental Outboard Marine Corporation (OMC) DISC Wankel rotary engine. The test program was conducted using an OMC single rotor experimental engine at NASA Lewis Research Center to obtain engine performance data and to investigate the stratified-charge concept. To support these testing activities, numerical simulations were used to examine heat release and heat loss mechanisms (such as heat transfer, crevice volumes and gas leakage). These simulations were also used to investigate how DISC Wankel engine performance varies with changes in engine design and operating conditions. Experimental pressure data obtained from the OMC rotary test engine were used with the heat release rate computer model to compute the fuel burning rate and loss mechanisms. Performance predictions of the OMC engine were compared with experimental data. The performance improvements of the DISC Wankel rotary engine were also investigated.