Just a point of clarification -- the Wankel GMBH diesel fueled engines were
stratified charge. Stratified charge means that a non-homogeneous fuel:air
mixture exists in the combustion chamber, with a rich mixture at the point of
combustion initiation, and a gradient (or "stratification") towards a leaner
mixture away from the initial flame kernel. The idea is to create a stable
stratification that allows consistent and controlled combustion initiation
independent of fuel cetane or octane ratings. A diesel engine is almost a
stratified charge engine (because it has a non-homogeneous mixture strength),
but the true diesel relies on compression ignition to ignite a mixture that
is partially present in the chamber upon compression. If the cetane rating is
wrong, the combustion event will not progress smoothly. The rotary stratified
charge engines attempt to layer the fuel charge into an air flow pattern
defined by the rotor motion past the housing, thus maintaining stratification
throughout the combustion event. A positive ignition source (spark plug)
provides further control over the combustion process. Stratification is
accomplished by careful design of the rotor recess and injector and igniter
locations. Also, injection characteristics (pressures, rate shapes, and
injector hole patterns) play a big role.

The Curtiss Wright / John Deere / RPI engines used two injectors per rotor to
obtain better light-off and light load operation. The Wankel engine, being
smaller, was able to run well with a single injector per rotor. The
principles of operation are the same.

Getting a Mazda engine to run with this system would be difficult because: a)
the rotor combustion recess is not optimally shaped for stratified charge, b)
installation of the injectors would require extensive modifications of the
housing in an area that is critical for strength and heat transfer, c) the
combustion pressures generated by stratified charge operation are higher than
with gasoline homogeneous charge, and the engine structure might suffer as a
result. As Paul pointed out, it is a difficult development challenge.

Jon Lauter
Rotary Power Marine Corporation

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

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