>
> Paul,
>
> Thank you for providing feedback on the Hush power we have contacted
> Flowmaster to start a testing program and they further indicated they
> would
> work with us on a muffler solution for our engines. We will send
you the
> results after testing.
>
> As it relates to your question what sort of fuel burn are you
seeing at
> 5500
> to 6000 RPM in terms of gallons per hour?
>
> RotaMax Answer: This is an area where we see a potential to
misrepresent
> facts especially in the aviation industry. We burn fuel at an air
ratio of
> 13:1-13:4 at the higher RPM ranges of our engine. As you are well
aware
> fuel
> usage is based on Lbs/hp/hr IE BSFC. Below I have copied results
of engine
> testing at an engineering school who is building an LSA with our
single
> rotor engine.
>
> I also want to comment that fuel burn in aviation is a very important
> calculation with many variables, Aircraft, Prop, Wind speed, Air
Speed,
> Temperature Etc. We would caution individuals that these
calculations are
> very critical when making flight plans and can vary greatly based
on the
> stated conditions above.
>
> Our engine produces very flat torque and we believe more testing
will
> validate these tests below that show proper use of torque can and
will
> lower
> the required HP thus fuel consumption in an aircraft. We also
only run the
> engine to 6000 RPM Max as the operating range as it relates to
max thrust
> shown below is 5000 RPM Max. At the end of the day we would like
to take
> off
> at 5500 and cruise at 5000. Depending on the application take off
at 5000
> and cruise at 4500 provides very manageable engine program as it
relates
> to
> EGT, noise, cooling Etc this is a great range as the torque is flat
> throughout this range.
>
> Test results from engineering students using a 650cc normally
aspirated
> single rotor with a belt PSRU and a Kiev prop:
>
> Eric,
>
> At first glance, pitch setting #7 looks like a good choice. Of
course,
> this
> pitch setting is almost certainly too shallow for a decent cruise
speed,
> but
> there is no denying that the engine seems to like this setting -
it runs
> effortlessly at 4000 RPM, and spools up to 5000 RPM
easily. However, I
> expect that the #9 setting is probably closer to what we would
want to
> actually use. As you know, static tests are limited in
predicting actual
> performance in the air, and we won't be able to find the optimum
pitch
> setting until we can do flight tests, but these results are very
> encouraging, particularly with regard to the low fuel consumption
> results -
> I was expecting it to use more fuel at these power
settings. With the new
> fuel consumption measuring method, the numbers were not only
lower but
> much
> more consistent.
>
> Here are the latest test results:
>
> Pitch Thrust GPH Max Max
> setting 4000 4000 thrust RPM
>
> 6........ 215... 2.50... 370... 5500...
> 7........ 250... 2.42... 400... 5220...
> 8........ 255... 2.56... 380... 5060...
> 9........ 250... 2.75... 350... 4870...
> 10....... 250... 3.30... 335... 4630...
> 11....... 260... 4.00... 300... 4330...
>
> Notes:
>
> 1) The pitch setting is an arbitrary number on a protractor
provided by
> the
> manufacturer, and represents neither blade angle nor inches of pitch.
> Larger numbers mean more pitch.
> 2) Thrust 4000 is the thrust at 4000 RPMs, averaged over about a two
> minute
> period.
> 3) GPH 4000 is the average fuel consumption over the same period,
while
> holding the speed at 4000 RPM.
> 4) Max thrust is the maximum thrust possible at this pitch setting.
> 5) Max RPM is the maximum engine speed possible at this pitch
setting.
>
> I think we have learned about as much as we are going to from the
current
> setup, and I suggest that we next turn our attention to the reduction
> ratio.
> The 2.5 to 1 ratio we are currently using was an educated guess
made back
> before we had any engine or prop test data, and I am quite sure
that we
> can
> do better. I wish I could say that I have a mathematical model
that will
> predict the effect of changing the ratio, but without test data
from other
> ratios, this is not easy to do. So, I think the next step is to
cut some
> additional sprockets and run the tests again with the different
ratios.
> With more data, I believe we can draw some conclusions with regard to
> matching the optimum prop speed with the best compromise in
engine power
> and
> fuel consumption. When we designed the reduction drive, we chose
> sprockets
> with a simple semi-circular tooth profile so that we could easily CNC
> machine additional sprockets to achieve various ratios. While we
are
> capable of making sprockets here, I am under the impression that your
> machining capabilities are superior to ours, and I wonder if it
might be
> quicker and easier for you to make the new sprockets. If so, I
would be
> very happy to send some drawings and suggest some ratios to try.
>
> Again, we are very pleased with these results, and we think with some
> additional work, the combination of the RotaMax engine and the
Kiev prop
> is
> going to be an excellent power source for light sport
aircraft. With the
> bugs worked out of our test stand and a group of enthusiastic
students
> returning to campus in a few weeks, I think we are in an excellent
> position
> to work together with you to complete the work required to take this
> design
> from prototype to product.
>
> Don
>
>
>
>
> Eric Barger, President
> Phone 419-694-3000 x 222
> RotaMax Inc.
> 15152 Twp Rd 190
> Arlington, OH 45814
> Fax 419-694-1401
>
www.rotamax.net <http://www.rotamax.net>
>
>
>
> Don't put too much emphasis on static thrust. People have died
doing that
> with airplanes.
>
> The actual pitch required is higher than that required for max static
> thrust.
> The prop is always stalled up to about 60 MPH where it starts to
"bite".
> The engine RPM will start to increase around 60 MPH and on up. At
static
> the engine
> RPM is loaded down due to the stalled prop so static RPM may be
as little
> as
> 75% of max power RPM. The bottom line is max thrust at the top
speed of
> the aircraft or max thrust at the climb speed. Cruise prop verses
climb
> prop.
>
> BTW airplanes fly on HP and not torque. Drag times speed is HP.
>
> 200 pounds of drag at 200 FPS (136 MPH) is 40,000 pound foot per
second
> HP.
> One HP is 550 pound foot per second so that is 40,000/550 or 73
net thrust
> HP out
> of the prop. The engine HP required is 73/.8 or 91 HP. This is
because
> props are
> only about 80% efficient.
>
> The gear ratio you use has nothing to do with the HP except you
> can not run a prop tip above about .8 to .9 Mach. The idea is select
> a gear ratio that will allow your engine to reach its peak HP RPM
when
> the prop tips are going about .8 Mach. About 800 feet per second.
>
> My suggestion is a gear ratio of 2.5:1 so at 6000 RPM and 90 HP
the prop
> is
> turning at 2400 RPM during climb out which is about right for a
72 inch
> prop
> and an LSA airplane. You will need to cruise around 5000 RPM.
Where the
> power will be down to about 75 HP. Larger dia. prop for better
climb use
> a 2.8:1 gear ratio. If you have a short landing gear problem and
need a
> smaller
> dia prop go with a lower ratio such as 2.3:1.
>
> Consequently from the above table you cannot calculate the BSFC
or the HP
> as you don't
> know how fast the airplane would go with these RPM's and these prop
> pitches.
> My guess is your engine will have a BSFC of around .6 +/- .05 so
90 HP
> will burn roughly 54 pounds per hour or 9 gallons and hour. At 65
HP it
> will burn
> roughly 6.5 gallons per hour.
>
> The only way to determine the HP and the BSFC under static
> conditions is measure the torque. The easy way and cheap way is
to build
> a prop
> load dyno as in these dwgs. Cut the diameter of the test prop or
club down
> until
> the engine will achive 6000 RPM static. Then measure the torque.
Ignore
> the
> static thrust.
>
> HP is then (RPM x Torque)/5252. Of course you can then measure
the fuel
> burn
> directly in gallons per hour. Multiply by 6 to get pounds per hour
> and then divide by the HP to get BSFC in pounds of fuel burned
per HP per
> hour.
>
> Paul Lamar ...No rotor no motor.
Several times, you mentioned that rotaries can run on jet A1 or
other fuel
oil.
Of course it is not diesel cycle, but the normal ignition of the
mixture by
the spark plugs.
Paul can you give some clues:
- on what it take to make this conversion: injection system,
ignition system
etc..?
- on performance impact: I guess you get less horsepower at the same
RPM;
and what about torque ?
- on consumption: for same horsepower regime, difference of jet A1
burned
compared to avgas.?
I believe that a jet A1 rotary, in the 100 to 180 hp would have great
opportunities in Europe for the experimental market. Avgas is gettng too
expensive.
Mistral is planning a jet A1 engine, but i expect it to be too much
power
(over 200hp) and money and weight for the average experimental
builder in
europe.
Philippe CHENEVIER
Its been done but not in that power range yet. Don't expect as much
power or as
low a fuel burn as a true diesel. Here are some pictures of the
Wankel Gmbh spark assisted
heavy fuel engine of a few years ago. I saw this engine run at OSH
back in the late 90's.
It remains to be seen if the Mistral engine can generate more power
than 200 HP on jet A.
--
Paul Lamar ...No rotor no motor.
And, since Paul didn't mention it this time (but you asked), if you know
the horsepower at a given RPM, you can calculate the torque. It
actually probably goes the other way - dynos measure the torque over a
range of different engine speeds (RPM) and then calculate the horsepower
to be plotted.. There is no way to change the torque at a given engine
speed (RPM) without changing the horsepower at that engine speed (RPM) -
one is (by definition) dependent on the other. You increase the torque
at 5000RPM, you also increase the horsepower at 5000RPM. End of story.
Matt-
Well put Matt. Thanks. I'll try to use that in the future when the inevitable
torque question comes up again.
Paul Lamar ...No rotor no motor.
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