Ok wow There's a lot going on in that post and I spent the night
looking at and for Isayev V-750 engine information.
The chosen propellants are Gasoline and Peroxide
Why? Because over history it seems to me these are the most successful
combinations with the least deaths involved it's not a performance
choice. Granted gasoline is not as ideal as some others but as Paul
Breed pointed out it is easier to get good combustion stability using
gasoline over kerosine.
LOX would be ideal if it wasn't so damn cold and has pressure issues of
it's own that can get out of control very fast. I also do not believe
it's the right choice for a first time turbopump driven amateur engine.
Pressure? On the order of 1000 psi
We do have to make compromises in order to work together :)
All I really hope to get out of this project is the first successful
amateur turbopump driven engine and I don't care if it's electric or gas
driven.
It looks to me like others want to see what electric motors will do so
it makes sense to start off the testing with electric motors.
That right there pretty much limits the size/flow rate based on
available less expensive electric motors and puts the RPM in the range
of 50k rpm
I'll try to make some sense out of the rest of that post after I've had
some sleep.
Looks like there is some good energy in that post keep it coming!
Redirect that and you'll see what you really can do. Together a real
pump will emerge.
-------- Original Message --------
Subject: [AR] Re: Arocket Pump Progress
From: Peter Fairbrother <zenadsl6186@xxxxxxxxx>
Date: Tue, July 14, 2015 10:25 am
To: arocket@xxxxxxxxxxxxx
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
(you might want the fuel pump pressure to be higher than the oxidiser
pressure, as it might flow through regen channels)? preburner conditions?
Look at those turbopumps - the first thing you notice is that the
turbines are 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
pumping liquids. 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
a lot 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
and rinse at say 60 degree intervals to give six vanes. Tidy up the hole
in the middle, and cut away any parts which have not been removed, all
to a single depth.
Place on lathe, center accurately. Adjust topslide to highly acute
angle, then machine straight blade tops. Cut edge of disk flat. Machine
for shaft. Deburr, 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
the 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%
efficiency. You 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 design is
better 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-nichols.com/sites/default/files/wysiwyg/images/merlin_turbopump.jpg
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 rightward
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
