-----Original
Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Jim Sower
Sent: Tuesday, September 23, 2003 6:20 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Power on
a cold day was Re: [FlyRotary] Re:Some turbo thoughts from a pro ....
<...
density change is proportional to the change in absolute temp, so 10F is
about 2% ...>
True. But that 2% increase in power is ALL EXCESS THRUST (over and above
what it takes to hold exactly what you've got - say 90 kts and 1000 fpm
climb). Two hp would be 66000 #'/min which with a 2000# airplane produces
3300 fpm rate of climb - ABOVE what you started with !! Of course not
every spec of that extra power gets to the prop, but you can see how what
appears to be a modest power increase can produce results that are apparently
way out of proportion to change in power.
Just a theory .... Jim S.
Sorry; Jim. No cigar. Wouldn’t
it be wonderful. Except for drag and prop efficiency you’d be
close. Put those factors in and 2 hp will get you about 20 ft/min more
climb rate on a good day.
Al
Al Gietzen wrote:
Rusty, the rotary engine
(for what ever reason) just LOOOVVVVVEEEESSS those cooler days. I have
had fuel flow of over 20 gph on take off when OAT was 28F. That
calculates out to over 200HP, static RPM was 5800 rpm vice a nominal of 5200 on
a "normal" day. I've never said anything about it because
1. Who would believe me 2. Who would believe me? and 3. Who would
believe me? Anytime the OAT is below 65F or so my static RPM
increases about 200 rpm for ever 10F further temp drop.
Ed;
The
only problems with this is 1. I don’t believe it, 2. I don’t
believe it; and 3, I find it hard to believe J.
The
air density change is proportional to the change in absolute temp, so 10F is
about 2%. Maybe 3 hp? Gee, we don’t really need to
turbo because the adiabatic temp drop with altitude will overcome the loss of
power due to altitude J. Could there be some other effect going on here? Fuel density is
also changing. How are you measuring fuel flow.
One
problem with hp inferred from fuel burn is that we know that the rotary’s
don’t burn all that fuel to make power. Fuel is burning right on
out into the exhaust pipe, and the amount of unburned fuel varies with a lot of
other factors.
Al
--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T