The main reason I don't want to use a combustion/turbine such as the
ones made from turbochargers.
If your using the compressor/turbine you have to go turboshaft and I've
played with one of these combustion/turbines and they are far from
reliable.
There was a fella by the name of Nye I corresponded with while he was
developing one of the first of these (back in the 90's) and they just
don't run very well nor are they reliable enough.
-------- Original Message --------
Subject: [AR] Re: Turbopump prime mover
From: Ed LeBouthillier <codemonky@xxxxxxxxxxxxx>
Date: Thu, December 03, 2015 11:43 am
To: arocket@xxxxxxxxxxxxx, arocket@xxxxxxxxxxxxx
In the beginning there will be no load at all is all I'm saying.
Yeah, but there'll still be no horsepower. That's still fine. It's definitely
a beginning.
The turbo did not have impinging nozzles
The gap around the turbine is the nozzle (it contracts but does not
expand). The point is to produce choking to raise the velocity of
the gases to the speed of sound in that gas. The scroll directs the
mass tangentially to the turbine so that it impinges at a better
angle. If they don't have enough mass flow for choking, there is
still some acceleration of the gases. Ideally, though, there will
be choking.
I really don't know the math to do this obviously and I appreciate the
help.
What are you trying to do? I haven't been following this discussion lately.
What I seem to gather is that you are trying to produce a drive system able
to produce 30 HP at 50K RPM. Is that correct?
Personally, I think you're going to need something more like a jet combustion
chamber/gas generator to produce the pressure and mass flow rate you want.
But,
you can definitely start the thing spinning with compressed air.
Look at the jet engines that people have produced using turbo turbines
and you'll see the kind of gas generators that I think you'll need:
http://www.junkyardjet.com/
There are a LOT of variables and it is boggling and there is a lot of
information and maps for turbo compressors but the amount of data for
the turbine is far less, companies keep that data a little closer to the
vest.
Yes, I know the number of variables is boggling...I agree with you. There's
a lot to understand. I don't consider myself anywhere near an expert on the
subject, but I spent a few years studying the math of turbines and turbopumps.
At best, I'm a junkyard craftsman on the subject even though I've never built
one.
But some of the math that I reviewed the other day about mdot and Ve are the
basics. You can back out from the horsepower and RPM you want to the mdot and
Ve relationship you need. That'll dictate the kind of gas generation system
you
need (by gas generation system, I'm including compressed air tanks).
You can definitely work your way up from quarter-inch fittings to test
the lubrication system. The lubrication system is going to be crucial
to sustaining operation of the thing.
It is a learning process but we need a prime mover to run any
experiments on a real pump.
That's a good place to start.
Meanwhile if we bat around the details of the flow problem we can pretty
much solve that and we can all learn a bit more about turbines.
I'll try to put a few hours in the next week but I need to know the
particulars of the system you're planning on using. Here's my take
on what I need to know:
TURBINE FINAL TARGET PARAMETERS
-------------------------------
RPM: 50K RPM
Horsepower: 30 HP
Turbine Diameter: 2 x 0.834 inch = 1.668 inches
Gas Source: ? I think it'll have to be a combustion gas generator (or a car
engine)
Gas Pressure: 60 PSI sustained
Gas mdot: ? we'll have to work this out
Attached is a spreadsheet I use for turbine design. Hopefully
you'll find it interesting and educational. It won't apply
precisely to this application, but it'll be useful nonetheless.