Wankel Rotary Engine Development Status and Research Needs

摘要

This report summarizes the status of Wankel rotary engine technology, particularly as applicable to highway vehicles. The Wankel engine was invented over 25 years ago, and has undergone continual evolutionary design refinement. The engine's perceived advantages of less weight, volume, and complexity than reciprocating engines sparked keen interest, and Wankel-powered automobiles have now been in production for almost 20 years. However, in the early 1970s interest in the Wankel engine greatly subsided because of two problems with the engine at that time: poor fuel economy and high hydrocarbon emissions. The bulk of current Wankel engine development work applicable to highway vehicles is being conducted by Toyo Kogyo (TK) and Curtiss-Wright (C-W). TK has manufactured over 1.2 million rotary engines to date, and markets them in the Mazda Luce and Cosmo in Japan and the Mazda RX-7 worldwide. State-of-the-art production rotary-powered vehicles from TK now exhibit fuel economy which appears to be competitive with many equal-performance, reciprocating-engine vehicles. C-W is focusing its efforts on direct-injection, stratified-charge designs for military and aircraft applications. The company is developing a 750-hp dual-rotor engine for the US Marine Corps, and has completed a design study for a 320-hp general aviation engine. Based on typical reciprocating engines of 1975 to 1977 vintage, and with final drive ratios adjusted to give roughly equal vehicle performance, calculated Environmental Protection Agency (EPA) city fuel economy with the C-W rotary averages 25% higher than with the reciprocating engine. The highway gain is 13%. Use of diesel fuel or a middle distillate instead of gasoline allows an additional 11% gain to be projected on a per-gallon basis. In addition, further gains of 14 to 38% are projected to result from use of a smaller turbocharged version of the engine. (ERA citation 11:034239)