OK given the RPM limits for a given HP at a lower RPM the torque MUST

BE

higher. It is mandatory. No two ways about it.  It is a law of physics

and

not just a good idea. HP = T X RPM X K  You make RPM lower and torque
MUST go up to keep HP the same. Unfortunately airplanes fly
on HP,
HP to weight ratio and not torque alone.

Paul Lamar

Paul please clarify a point on Torque and HP.
You gave the formula for calculating horsepower as
HP = T x RPM  x K

Correct me if I'm wrong.

My understanding is that the formula is:

HP = T x RPM / 5252
HP = Torque   times   RPM   divided by   5252

at an rpm of 5252 HP = Torque
Torque = HP x 5252 / RPM
so this means that  HP is a direct function of RPM

In an  "IDEAL" engine design the combustion energy  and transfer
to mechanical energy output would be a constant  over the total range
of RPM and that  would produce a torque that  is a constant for that
engine conformation.

In real life rather than a constant torque value we end up with the
typical Torque  curve. The reason that we get a curve rather than
a constant torque indicates the relative efficiency at each stage over
the RPM range is not constant.  The RPM does  not determine the
Torque what  it does is effect the factors that  determine the
volumetric, combustion and pumping efficiency of the engine.
Since each varies over the RPM range the out come is a variable Torque
curve,
but  Torque is not a function of RPM directly.

Only HP is a direct function of RPM.

The fact that  the Wenkel rotary engine has a relative flat torque curve
over the full RPM range is a testament to it's design efficiency.
Porting, intake and exhaust tuning, air / fuel management,  with
efficient boosting can  optimizes the BSFC efficiency to make the
Wankel rotary the ideal aircraft engine bar none. Lets face it the wankel
rotary was  born to fly!

Orest Sokil

I don't follow you. We were comparing two engines with the same max HP at
one HP point. I.E. max HP. One was a diesel and the other a gasoline engine.
If the RPM is 6000 in the case of the 200 max HP gasoline
engine the torque will be X. If the other engine is 200 HP at 3000 RPM
it's torque will be 2X. That is all I was trying to say.

K = 1/5252 =  0.00019

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2003 All world wide rights reserved.