Possibly, it was what I was told by a friend sometime ago, that was taking a
course in school, and one of the problems that they were working on, of course
it could of been something else, it was 10 - 15 yrs ago.
As for the aircraft, don't forget that with warm air, it is a lower density and
they would need more thrust just to maintain altitude, that in it's self, would
cause higher fuel consumption.
Greg H.
----- Original Message -----
From: Alan Petrillo
To: biofuel@yahoogroups.com
Sent: Thursday, November 06, 2003 14:34
Subject: Re: [biofuel] Microturbines vs fuel cells
Greg and April wrote:
> It is somewhat dependant on the incoming air temperature, the higher the
incoming temp, the less fuel they have to use for a given power output. In
general it is my understanding that they are better than conventional ICEs.
I could be wrong, but I don't think that is correct.
If you put a high temerature in then you get a high temperature out, and
you usually flirt with overheating the burner and power turbine. Very
often before the engine reaches its rated output.
Long range jet aircraft generally like to fly around 41,000ft altitude,
because that's where they get the best winds and temperatures aloft. If
it's too _warm_ up there then they just don't get the range.
When I was in the Army flying OH-58C's the lowest fuel burn figures I
saw were during very cold weather. Sometimes so low I had to double
check my figures to make sure I wasn't making a mistake. On really cold
days I saw burn rates as low as 135pph, and during the summer I was
lucky to see burn rates as low as 155pph, and 185pph was not uncommon
for the first hour. Performancewise, they'd pop right up during cold
weather, but we could barely drag them off the ground in hot weather.
What turbines really run on is the temperature _difference_. And
pressure difference. If you have cold, dense air coming in then they
don't have to work as hard to compress it, they don't have to work as
hard to heat it, they cool themselves more efficiently, and since it's
denser the power turbines can get more of a grip on it.
My experience is that turbine engines like their intake air as _cold_ as
they can get it.
An interesting thing is that helicopter turbine engines run in exactly
the same way as the turbogenerators for a turboelectric hybrid would.
The engine runs at a constant rpm, senses load, and adds torque to
compensate. In a helicopter the load is put in when the pilot pulls
collective pitch and demands power to keep the rotor speed up. In a
turboelectric hybrid the load is put in when the driver puts his right
foot down and feeds electric current to the motors, thus demanding power
to keep the generator speed up. Build the motors to run on 110v 400hz
and you could even use off the shelf aircraft technology on the
generation side.
AP
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