1993-03-01

An Experimental Approach for the Development of a Small Spark Assisted Diesel Fueled Rotary Engine 930683

A spark-assisted, direct-injected family of small rotary engines with a rotor displacement of 400cc was designed, manufactured and optimized for the use of heavy fuels, especially diesel fuel.
The development focused on the modification of an existing gasoline rotary engine to accommodate heavy fuel mixture formation and combustion. Off-the-shelf, low-cost fuel injection, and ignition systems were modified to match the peculiarities of the Wankel engine.
The performance optimization work was of an experimental nature. A multitude of factors which govern the air-fuel mixture ignition and combustion in the small, spark assisted, direct-injected rotary engines employing a single injector and an open combustion chamber were explored.
Satisfactory results were obtained for a defined speed range at various loads. Specific fuel consumption lower than 330 g/kW-hr (0.55 Ib/hp-hr) was obtained at various selected regimes with power levels between 5-12 kW and speeds between 3000-4000 RPM.
In addition to diesel fuel, good results were obtained on a variety of jet fuels.
While the single-injector, open combustion chamber arrangement developed for this application did not yet match the efficiency and operating flexibility already obtained in medium and large dual-injector, stratified-charge Wankel engines, it offers a convenient solution for small-displacement rotary engines where the space available for the combustion chamber is limited and simplicity and cost play important roles.
Future work will focus on improving the engine power density, fuel consumption and flexibility of operation in a broader range of speeds and loads.

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