Eliminate, no. A piston pump will also have some minimum inlet pressure
- NPSH, Net Positive Suction Head, do I recall correctly? - if it is to
avoid cavitating.
As for whether a piston pump would let you do design tradeoffs to lower
NPSH and lighten tanks, good question. Not something I've ever looked
into specifically. My guess would be, yes - but I expect there are
those here with a far more reliable answer than that.
Henry
On 12/15/2016 1:03 PM, Brian Feeney wrote:
Would a piston pump reduce or eliminate the problem of cavitation one
can get with a turbine? If yes, this would lead to lower tank pressure,
lighter weight tanks - buys back some of the weight increase of the
piston vs turbopump??
Cheers
Brian Feeney
On Dec 15, 2016 2:40 PM, "Henry Vanderbilt" <hvanderbilt@xxxxxxxxxxxxxx
<mailto:hvanderbilt@xxxxxxxxxxxxxx>> wrote:
On 12/15/2016 9:15 AM, Dave McMillan wrote:
On 12/15/2016 11:01 AM, Thomas McNeill wrote:
I have been curious about different pumping mechanisms.
Instead of a
turbo pump what about positive displacement pumps, like gear
or lobe?
Has there been any attempt at using one of these types of pumps?
I have to admit to being curious why I've never heard of any
amateurs trying a variant on XCOR's piston(less) pumps -- those seem
like a much lower bar to get over than any kind of
turbomachinery. Some
subtle difficulty I'm not seeing, there?
XCOR's pumps are not pistonless; that's Flometrics you're thinking of.
As for the root question, I see no reason why developing an
electric-drive piston propellant pump should be particularly
challenging.
Off the top of my head...
- You need to pay attention to compatible piston-seal materials
(and to flow-path materials compatibility in general, of course).
- For cryos, you need to pay attention to thermal dimensional
issues, seal & lube temperatures, and flow-path conditioning.
- You need to pay attention to output pressure variations, to the
extent your motor/application may be sensitive to them.
None of those involve bleeding-edge new tech development. Just a
matter of known detail engineering. And there's this: There's a
HUGE existing parts-base out there for piston machinery components,
both in pumps for other applications (pressure-washers anyone?) and
in the small IC engine field.
I'd lean toward the explanation that people haven't looked at piston
over turbine pumps more out of established habit than for
fundamental practical reasons.
After all, if you're using a turbine for pump power, making the pump
a turbine wheel on the same shaft uses design/manufacturing
resources you'll need regardless.
Going to electric pump power, that no longer holds true. You can
now skip the (apparently) considerable investment in
high-performance turbine design/fab capabilities.
Henry
