Ah! Thank you Troy that is very useful. If you made the housing also
can you share the drawing of that as well?
-------- Original Message --------
Subject: [AR] Re: Arocket Pump Progress
From: "Troy Prideaux" <GEORDI@xxxxxxxxxxxxxxxx>
Date: Wed, July 15, 2015 8:10 pm
To: <arocket@xxxxxxxxxxxxx>
Regarding the size: attached drawing of the impeller.
Oh: I just recalled after sending that msg that it was done with a 4th axis.
Troy
Was it ever tested? How big is that one? And is Andrew still around? :)
-------- Original Message --------Burns back in early 2013. I don't have access to fancy CAM software tools
Subject: [AR] Re: Arocket Pump Progress
From: "Troy Prideaux" <GEORDI@xxxxxxxxxxxxxxxx>
Date: Wed, July 15, 2015 4:36 pm
To: <arocket@xxxxxxxxxxxxx>
I milled and turned up the components for a Barske rocket pump for Andrew
so I finished up manually writing up all the G-Code myself to cut the
impeller which was the trickiest part to make (attached). At least by doing
it that way, I got to optimise everything including cutting time,
smoothness of finish and setup. Would have been lovely to have more than 3
axes too:)
I don't know if Andrew is still on this list but he did some reallygood theoretical work (Spreadsheets, very cool innovative turbine concepts)
for turbo pumps back during that time.
On
Troy
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
forward.Behalf Of Russell Blink
Sent: Thursday, 16 July 2015 8:21 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Arocket Pump Progress
The machining on any of these small impellers is pretty easy, until it
requires swarf milling on our 5-axis machine they are all about the same.
I turn the profile, cut around the vanes then part, pretty straight
(II do have to use a fairly small endmill so the machining time is a bit
longer than you would expect for such a small part, but not horrible.
Ishould say easy for our lathe since I can do it all in one setup and if
muchneed to machine on the back side transfer to the sub-spindle is simple)
These small impellers are all inefficient ~65% would be good, pretty
regenerativewhat a Barske will do and you don't have to worry about undue
Onheating or possibly the stall point of the partial extraction curve.
Tip/face clearance is the biggest difference if you ask me.
Russ Blink
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
(youBehalf Of Peter Fairbrother
Sent: Tuesday, July 14, 2015 12:25 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Arocket Pump Progress
On 14/07/15 16:37, Monroe L. King Jr. wrote:
I agree and it was the Merlin I was looking to for inspiration.
But the split design of the SA-2 also has it's merit and it is
possible to actually get a hold of one of those to get a good look at
and take measurements from as well as perhaps some 3D scans if nothing
else. It can also be copied.
I'm willing to cut some corners here and take advantage of a known
good design if we can.
The other thing is the SA-2's propellants and pump designs are closer
to the same for our chosen propellants.
also looks to me like the SA-2 has open impellers?
If I can find/buy one to use as a reference it should cut development
in half.
Or do you think that is mot a good way to proceed?
This is our project you tell me. You are designing a turbopump Peter.
propellents? thrust? flow rate? chamber pressure? pump exit pressures
pressure,might want the fuel pump pressure to be higher than the oxidiser
turbinesas it might flow through regen channels)? preburner conditions?
Look at those turbopumps - the first thing you notice is that the
pumpingare a lot wider than the pumps. Your turbopump should look like that.
If you think about it, the turbine is pumped by gas, the pumps are
aliquids. Just from a density point of view, the turbine has to be wider
than the pumps.
The impeller design you are using is going to have terrible efficiency -
the vanes are too shallow for good efficiency, there will be too much
friction.
You would be far better off with a Barske-type impeller. And it would be
andlot easier to make, you can machine one on a manual milling machine and
lathe.
The blades are straight and parallel, and point to the center - so start
with a disk and endmill the edges of one blade pair to a depth. Repeat
therinse at say 60 degree intervals to give six vanes. Tidy up the hole in
singlemiddle, and cut away any parts which have not been removed, all to a
shaft.depth.
Place on lathe, center accurately. Adjust topslide to highly acute angle,
then machine straight blade tops. Cut edge of disk flat. Machine for
theDeburr, polish, balance the impeller.
Place casing blank on lathe. Cut the edges of the hole in the casing
straight to diameter, just a little over the impeller diameter. Machine
efficiency.base of the concave hole using the same topslide setting and angle, but
with the lathe in reverse, then machine for bearings and seals.
Attach exit pipe, cut the tapered exit hole.
Simple. If designed and made properly, should get around 40-50%
designYou will probably want to operate it at about 100,000 rpm.
There is a useful book by Lobanoff and Ross.
The main difference between the SA-2 and Merlin engine turbopumps is
that the Merlin pump has the turbine on one end, while the SA-2 tp has
the turbine in the middle. I like the Merlin arrangement - it keeps the
hot turbine as far away from the cold LOX as is practical.
The hot turbine is next to the fuel pump - doesn't matter much if a few
sparks get in between, as there is no oxidiser present. For the oxidiser
pump, a few sparks can kill .. there is fuel in there (the pump body and
impeller, if nothing else ...).
-- Peter Fairbrother
-------- Original Message --------
Subject: [AR] Re: Arocket Pump Progress
From: Peter Fairbrother <zenadsl6186@xxxxxxxxx>
Date: Tue, July 14, 2015 8:10 am
To: arocket@xxxxxxxxxxxxx
On 14/07/15 14:36, Monroe L. King Jr. wrote:
That does help some! Thank you. I do believe working from this
rightwardis
nichols.com/sites/default/files/wysiwyg/images/merlin_turbopump.jpgbetter than trying to go with a V-2 design :)
It's not bad, but if I was designing a turbopump I'd use the Merlin
engine turbopump as an example. It's a pretty good one.
http://www.barber-
The picture is pretty small, but it shows most things: at the bottom,
from left to right, there is the LOX pump with integral inducer, the
shaft with fuel pump and inducer, the turbine wheel.
It is a reaction turbine, and I think a partial admission one - a
reaction turbine has less end thrust than an impulse turbine, and in
theory only a very low pressure differential across the disk - with a
single shaft with two pumps, both with screw inducers, pumping in
opposite directions to balance end thrust.
Note that the turbine gas flows to the left, creating a leftward end
thrust on the shaft, and the LOX flows to the left, creating a
end thrust to balance both the turbine end thrust and the lesser
leftwards thrust of the fuel pump (fuel flows to the right).
For a smaller engine I would consider Barske style partial emission
pumps, or closed impellers; if nothing else, in order to make
construction easier. Perhaps tesla inducers too.
-- Peter Fairbrother
