Hello Doc, Paul and all,

Yes, developing heavy-fuel capability is a major
development effort
indeed.
Here at Mistral, it is definitely our most ambitious
development
project. I
take the opportunity to inform you all of our progress
on this front.

First, let me say that we are developing an engine to
use and to be
certified with Jet-A. If we succeed, then there are a
priori no reason
for
that engine not to work on diesel or biodiesel fuels.
However, as Doc
pointed out, these fuels are pretty much inappropriate
for aviation use
with
the exception of some special applications such as
agricultural
spraying.

You can get a rotary running on Jet-A with NO
modification. However,
at
about 25HP per rotor, you'll encounter BRUTAL
detonation. With direct
high-pressure (10,000 PSI) injection, with the
injector replacing one
of the
spark plugs, you can push this limit to approximately
50HP per rotor.
Relatively easy so far.

But to push the limit back to 100HP per rotor or more,
where you ought
to be
to have a decent aviation engine, then you have to
work VERY hard on
where
you locate the injector, under what angle and what
spray pattern you
inject
fuel. You also have to determine optimal compression
ratio and "bath
tub"
geometry. It just cannot be a trial-and-error type of
development
anymore,
but a scientifically driven one.

Mistral has partnered with the Swiss Institute of
Technology in
Lausanne
(one of the two most prominent engineering school in
Switzerland) and
its
Laboratory for Industrial Energetics to develop a
rotary engine
direct-injection and combustion simulation software
and then to apply
it on
the particular issue. It is a two-year project for
two full-time plus
two
part-time engineers.

However, we already know quite a few things.
Comparing a two-rotor
turbocharged gasoline engine (our G-230TS model) with
a two-rotor
turbocharged (it's got to be turbocharged) kerosene
engine, the
following
trade-offs apply:

The good news:
- The K-series engine will use Jet-A and its fuel
consumption will be
inferior to that of the G-series engine by ~5% in
weight (because of
the
slightly better efficiency of direct over indirect
injection and of
higher
compression ratios) and ~20% in volume (mainly because
of the higher
energy
content of Jet-A per gallon). It therefore increases
range somewhat
and
saves you quite a bit of money relative to a
100LL-burning engine.
However, mogas is still by far the cheapest fuel
available. It just has
to
become more widely available on airports, like it is
in Germany where
~60%
of airports sell mogas.

The bad news:
- The K engine will probably develop 20-30 fewer HP
than the G engine.
- The K engine will weigh 20-30lb more than the G
engine.
- It will cost more to maintain and to overhaul
because of the
expensive direct-injection system and higher-energy
ignition system.
- It will be somewhat less reliable then the G engine
because of the
additional technology and because of single-point
failure possibilities
such
as the high-pressure fuel pump which can hardly be
doubled-up.
- It will cost approximately $8,000 more.

I would be interested to know if you think such
sacrifices are worth
doing
for the economy of using Jet-A. In some countries, it
is definitely
the
case, and that�s why we are developing the K-series
engines. However,
I
have doubts that the US market would be ready for such
compromises.
I'd
love your feedback.

Fran�ois Badoux
CEO Mistral
http://www.mistral-engines.com/

francois,

i think you're right about the u.s. market. your
experimental G-190 is allready $31,500, assuming the
price of the k will at least double that in price to
cover amortization of certification and developmental
cost, plus the cost of the direct injection system and
increased matainance, i think recreational flyers in
the u.s. would be hard pressed to fly enough to make
the fuel savings pay out. now if you can build one to
put out 2000 horse power to replace the turbines on
commuter airline planes you might have some business.

Gary

2000 HP is probably out of the question but a 1000 HP turbo
four rotor might be possible.

Paul Lamar

Thanks for your opinion, Gary. Most recreational flyers don't want or need
something overly complex and costly as they fly too few hours to admortize
the upfront cost. I was actually thinking about the certified market.

Francois

Francois,
Have you investigated the new Siemens piezo fuel injectors used on the
new Audis? They have a new lightweight back up pump as well. Your
current control should be able to run them. A very slick system. Can be
used with gasoline as well.
Bill Jepson


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