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Old December 3rd 09, 06:53 AM posted to rec.aviation.piloting
Bob Nixon
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Posts: 12
Default failure of an auto engine

On Nov 28, 8:11*am, " wrote:
On Nov 27, 8:11*pm, wrote:



On Nov 26, 9:35 pm, "Morgans" wrote:


The idea that a Wankel could run well on jet fuel is an interesting one, but
one I have never seen proposed for a full sized Wankel in an airplane, or
anywhere else, for that matter. *Are there any case studies of it happening?
--
Jim in NC


I don't see that happening, either. Kerosene's flame front travels
more slowly than gasoline's, as I understand it; about half the speed
even at the high compression pressures in turbines. When a gas-eating
auto gets diesel instead of gas, it gives up real quick. Produces
little power and gets real hot. The compression ratio is far too low.


[...]

You have it all "Bassakwards"! Kerosene (Diesel-1 & jet fuel JP-4,5) &
pump Diesel #2 once heated close to their flash points have a far
faster burn/meter rate than gasoline, propane, butane, LNG or Alcohol
(either Methanol or Ethanol). These fuels are all rated for combustion
stability & rather slow burning/liter or Octane rating whereas
Kerosene & Diesel fuels are rated for unstable spontaneous combustion
or CETANE rating 40. This makes a slow, poor burning combustion
chamber as in the Mazda Wankel's at =9.0:1 CR a nice solution for
those flaming exhaust pops and such. What happens is that once up to
say 180 degree F Kerosene or JP-5 will burn very quickly and not have
such a high EGT in a non-turbocharged Wankel engine. One might surmise
that pinging will result & melt down the engine but if you go back in
time even low compression tractor engines (way back before Diesel
tractors were common place) used a system of gasoline warm-up then
switched to cheaper and more available during wartime KEROSENE without
ruining their engines under heavy loading and advanced timing.
Wankel's surely must have a good cooling system but the stock one on
the 100HP versions should be more than adequate. BTW, the reason most
uneducated in the field feel that Diesel engines burn more slowly is
than their combustion cycle is not a "one shot" affair as in a spark
ignited engine but rather either a pulse (common rail injection) or in
older Diesels the injection continues like a blow torch in a a lean
air mixture or non-stoichiometric but rather a "stratified" like a
torch effect that continues to burn far after TDC. Now if you need a
refresher in chemistry and physics or whatever then go for it but
please don't spout out fear based ideas you have for no conception
about. Thanks.

Bob Nixon..