Paul,
Now planning the test program for the 1990 turbo13B.
Soon I want to know how much hp the compressor is drawing and how much power
beyond that there is to spare.
The turbo tach will give us the turbine rpms but for the torque?
We can measure temp., we know the exhaust pipe diameter, but velocity is per
speculation at this point. Perhaps Mazda engineers have data on exhaust
velocity. This would help us immensely in sizing the downstream turbine.
We may have to approach this challenge from the other end so to speak. IE
guesstimate the second turbine size and attach it downstream of the
turbo/charger, then attach a transducer to it and measure its torque output.
We will know the Hp. output of the engine and the intake air speed, MAP,
temp. and size of the intake pipe so we can use some deductive reasoning
about what is happening when we load the first and/or second turbine. From
there we can play with other turbine sizes and PSRUs.
Then how to increase the Delta P? The highest mountain road nearby will
allow me to bring the test stand to 8,000 ft. Perhaps on a hot summer day
the density altitude will be 10,000. It's not FL 25 but a start:)
Doug in Japan
For background on turbo compounding read
http://www.rotaryeng.net/turbo.html
Paul Lamar
Paul,
First thing I read:) Great theories. Time to test some of them. Not to
worry though, I'll see if Hisanori knows the answer on the exhaust gas
velocity. I'm sending you a MATEX planetary gear catalog soon.
Doug in Japan
I think you should use a friction drive planetary. Paxton used a
ball friction drive planetary for 50 years on their geared up
centrifugal superchargers. I did a lot of R&D on gear mesh line
velocities and it don't look good so far. Maybe MATEX has it
figured out. The torque from the turbine is super low while
the HP is still significant because of the 100,000 RPM.
HP = Torque X RPM / 5252
This means you don't need a whole heck of a lot of friction
to transmit the minuscule torque. The other thing about friction
drive is a few torque pulses due to firing loads and rapid angular
accelerations won't hurt it. A lot of cars are now using friction
drive infinitely variable auto transmission.
Paul Lamar
Paul
I agree with the your design philosophy even though I don't completely
understand it:) How can discs have enough friction to roll but not too much
to bind? Gears are suspended and have a degree of lash designed in which
can also be their downfall in high revs environmens. Balls are one point
contacts but discs? Hmm. But this discussion is premature:) First I need
to know the dynamics of the exhaust flow.
You mentioned once weeks back that to lower the operating temperature that
the turbine encounters, move it a little downstream of where it is usually
mounted near the block. That would entail radiating heat to the cowl
environment but I wonder if the turbine will experience less exhaust
velocity as well.
Doug in Japan
You could ask the same question about a locomotive :)
Steel wheels on a steel rails pulling 1,000,000 tons.
Although the coefficeint is low (.7 as I recall) the force
holding the wheels to the rails is high. That is the reason
for the springs in the Paxton blower.
As I recall it is P X T = V
I am up at the hangar so I don't have my physics books to check.
P X T is potential energy.
As you lower the temperature the P X T or volume term will be reduced.
If you reduce the volume flow per unit time in a pipe you also reduce
the velocity. I suspect both velocity and pressure are reduced.
The WW II P47 had the turbo charger in the tail and still found
enough energy left in the exhaust to power the turbo charger so the
P47 could still get up to 40,000 feet as I recall.
Paul Lamar
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