Ernest,
A
quick check of my calculations suggest that 170 MPH should be good up to our
RPM requirements. So if your wrong we are both wrong. My figures are based on
a 44 mm PP and the inlet speed in well below that, however I note the smaller
diameter speeds get up to over 200 mph at 7,500 rpm. I can't remember how your
configured.
George ( down under)
> Ed Anderson
wrote:
>>
>> The way a turbo/super charger
works, of course, is not by increasing the >> air volume flow through
the engine but by increasing the air density. The >> 100,000 rpm
impeller accelerates the air velocity inside the compressor >> vanes and
then using the old Diffuser principal, slows this air down at >> the
compressor exit and converts the increased dynamic energy of the >>
accelerated air stream into a static pressure increase reflecting the >>
increased air density
produced.
>>
>>
> And the turbo
charger is a centrifugal pump. 8*) One of a comparatively > small diameter,
but high speed. I'm looking at a much larger diameter, > but a much slower
speed. Diameter and speed are what determines the > maximum static
pressure. How well the pump can hold that pressure is > determined by its
flow rate, which is in turn determined by the volume of > the pump. I
calculated that the air would flow at 170mph, with the intake > and exits
being 3" diameter. Not exact numbers, but the speed point is > higher than
my projected cruise speed, and the intake diameter is smaller > than the
runner I'll actually have. I have a relatively large volume > between the
flywheel and PSRU plate, being about 4" thick. All that > scribbling is at
home someplace, and I'd be hard pressed to find it. > Basically, I'm
counting on that thickness to overwhelm the engines needs > and keep the
pressure near the max static.
>
> I do admit that I'm
remiss in not applying the technical rigor to carry > out the equations to
the 4th digit. You and Al are good at that, Ed, but > I am content to run
some rough numbers. I figure the practical won't > match the theoretical
anyway. So if it looks good at first pass, build it > and then take a
measurement.
> I think this would be a good move if I can get 5 to
10 extra horses out of > it. On the other side of the equation, I'm looking
at what are the > drawbacks (other than the design/build workload, which is
supposed to be > the fun part anyway). Failure modes, other than shedding
blades, should > be benign or non-existent, as I'm not providing for any
control hardware. > If the flywheel stops turning, the intake can suck air
around the > blades...but that is a moot point, because if the flywheel
stops the > engine is about done sucking air for a while anyhow. A leak in
the intake > means that I don't get as much boost as I hoped. In that case
I'm just > another normally aspirated rotary. The worst case scenario would
be the > highly unlikely event that I get TO MUCH boost. That will prove
out easily > enough during testing, and would only require some sort of
restriction to > rectify.
>
> There may be up to
twenty Hp waiting there, and it'll only cost about 3 to > 5lbs of aluminum.
If it works, I'll have one of the coolest, most unique > engines at the
fly-in, with one of the highest Hp/weight ratios around. > If it doesn't
work, I get to wear the "I tried something that didn't work" > badge that
makes one a true Flyrotarian. ;*)
>
>
>
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