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Ed,
I
don't see any attachment. I would really like to see that
spreadsheet. Can you please forward me a copy ?
Thanks,
Steve
Brooks
Due to overwhelming
popular demand.... Ok, Ok, at least one person requested it. I have
now created a spreadsheet where you can run NA or with a turbo charger.
The HP, fuel burn and BTUs should work out pretty good and even the cooling
section. The tubo model does take into account the less dense air after
compression since that affects power. But there is NO turbo modeling
done. I used 65% efficiency for the compressor efficiency which may be a
bit on the low side, but is conservative.
The cooling section now permits you to specify a
different radiator size than the Gm cores. However, the oil cooler is
still an RX-7 oil cooler, but you can select more than one. Again this
simple cooling model is based on airflow caused by airspeed as constrained by
the surface are of the radiators you specify. It does not taken into
consideration lessening delta T due to radiator thickenss or the decreased
pressure across the radiator either. But, it gave me close to the actual
results I see when I fly - inadequate cooling during take off and intial climb
at high power settings so temps climb, but once I hit around 120 MPH and/or pull
back on power the higher airspeed and lesser power results in adequate cooling
during the cruise climb and more than adequate during cruise at alititude.
yes, I lower the density of the mass air flow at altitude to try to keep it
fairly realistic. But, thats about it.
I will remind everyone that this is not a
simulation and while I have taken a great deal of care into ensuring that the
math model for the engine section is as accurate as I can make it, its only a
model and not a simulation. That means you CAN input 20 psi boost at 1000
rpm and it will give you the HP that would create although in real life the
exhaust output at 1000 rpm would probably never come close to giving you 20 psi
boost. Soooo, its up to you to input realistic combinations. You know -
the garbage in and garbage out thing.
Also since there is not a simulated load on the
engine, it will given you what ever rpm you want (don't you wish real life were
this easy) - however, whether a real engine with a real load and real induction
and exhaust system can achieve that rpm is another question. If anyone has
a simple math model that would provide a load figure based on pitch, diameter,
number of blades that would provide the HP/torque required for two modes.
Say Acceleration (take off) and cruise (steady state) I will see if I can adapt
the program to reflect real world prop loads. Lets start with a fix pitch
prop model {:>). Any Propeller experts on the
list??
To keep Marv from getting on me about consuming too
much of the server disk space, anyone who wants a copy please send me an email
off the list. My email below.
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