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From: (ReganRanch)
Newsgroups: rec.aviation.homebuilt
Subject: Re: 2-stroke diesel, GAs future?(was 2-stroke diesel)
Date: 4 Jul 1998 17:42:30 GMT

From: (David Munday) wrote:

> (ReganRanch) wrote:
>>I hate valves, cylinder heads too. Take a look at the Junkers Jumo engine of
>>the 1930s. Diesel opposed piston aircraft engine used on scheduled flights
>>across the Atlantic. No valves, no heads, no worries, mate.
>So has anyone tried a wankel Diesel?  It would, at first glance
>anyway, seem to be better still.. The Wankel has a reputation for
>being bullet proof.  You can dial up the compression by changing the
>faces on the rotor.

Actually you can't get diesel compressions out of a Wankel because of geometric
and seal limitations. High compression ratios and high angles of oscillation go
hand in hand and high angles equal poor sealing. The highest practical
compression ratio for Mazda morphology is around 10 to 1 even though a
theoretical CR of 15:1 exists. I would invite you to read Kenichi Yamamoto's
book "Rotary Engine" and all will become clear, Grasshopper.

> You might well need more structure in the rotor
>and the housing to contain the pressure, but if we're talking "clean
>sheet" here, that's no problem.  The usual problem with the Wankel is
>the flat combustion chamber, and the problem of flame propagation
>within it.  I suppose there'd be a similar problem with injecting the
>fuel into such a space, but multiple injectors might help, just as
>multiple plugs do in the gasser.
>Has this been done?  Is there a reason why it would not likely work?

In theory a stratified charge (spark ignited direct injection) would work. The
combustion chamber moves past the injector providing good fuel distribution.
Curtiss Wright worked this problem for almost 20 years and then sold it to John
Deere. There are lots of SAE papers on the subject.

The Achilles heal of the Wankel is the corner seal. Nature abhors a square
piston. I like the Wankel. I supplied the ceramic-coated rotors that were used
in the RX-7 engine that won the 24 Hours of Daytona in '83. I just don't think
that it is the engine for the next generation aircraft. IMHO.

Brent Regan

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