From: jtkare@attglobal.net
Greg wrote:
> Jim Davis wrote in message news:
>...
> > Since the subject of turbopump alternatives comes up fairly regularly
> > the following recent (and interesting) paper might be of interest:
> >
> > Knight, Andrew, "Designing and Testing a Lighter, Simpler, Less-
> > Expensive Liquid Propellant Pump", Journal of Propulsion and Power,
> > Vol. 20, No. 1, Jan-Feb, 2004.
> >
> > The pump he describes seems remarkably similar, in appearance at
> > least, to the Comprex supercharger.
>
> I have not read the paper. My university does not receive that
> journal. After reading the patent i'm not going to bother with
> inter-loans etc.
>
> I seems like a bad idea to me IMO. It is just a version of the
> piston-less pump really. He has just replaced the valves with a
> rotating slide thing..... ok so i'm not good at explaining. IMO slide
> seals are not easier than valves.. well valves have sliding seals too.
> I see no advantage in the design over piston-less pumps.
>
> While on the subject. Positive displacement pumps don't have the NPSH
> problems that dynamic pumps have. Pistons have advantages over
> piston-less. But what about other designs. Like a screw pump with a
> screw expander? That way you get the gas to do some work while
> expanding, rather than "workless" free expansion...
Not sure what you mean by workless free expansion, but...
We did look a bit at rotary positive displacement pumps (and rotary
positive-displacement motors) for Mockingbird. They tended to be
heavier than piston pumps, and there's less integration of the drive and
pump sections, but they weren't out of the question; we just didn't have
the time and resources to look at them in detail. One problem with
rotary expanders is that they tend to be hard to seal; they need tight
tolerances which are difficult to maintain over a wide temperature
range.
Jordin Kare
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