Friday, January 23, 2009

Just checking in

Since the ring catalyst failed we are evaluating two other kinds. We are looking at traditional silver plated nickel and some metal monollytic catalysts. We have some samples of the metal monolyths we received from John Carmack and we hope to test them in a regen cooled engine capable of running in Monoprop or Biprop mode in a week or two.  I ordered the nickel screens and hope to fabricate a motor for that configuration in the next two weeks.

I’ve been working on machining the regen engine out of a large chuck of aluminum and the size is stressing the capabilities of my lathe. The Lathe is a manual lathe converted to CNC and the cross slide tool mount was not very rigid. I started more than a week ago to machine some new mounts and the speed control on the Mill motor started acting up. So I bought the Tormach speed control upgrade (stock on the new Tormachs) and Its a great upgrade. Now that is fixed, I’ve spend the last week machining new tool mounts out of large chunks of steel. they should be more rigid.  The mill is machining the last piece as I write this so I hope to get back to machining the actual motor on Saturday.  Machining Aluminum and the C145 copper is fun, Machining stainless is miserable, machining medium steel is some where in the middle, not as picky about feed rate as stainless, but still wears the tooling a lot faster than aluminum. 

On a side note I stick all the tools I use at the mill, draw bar wrench, vice wrench, chuck keys etc… to the back of the mill with some strong magnets.  With aluminum or Stainless this is not an issue, when machining  steel all the sharp chips stick to the tools making it a hazard to use them. No fun at all.



Wolfkeeper said...

Using aluminum for a regen engine can definitely work- there's multiple existence proofs. However you need to even more than normally careful with thermals.

Most aluminum engines I'm aware of are run at or below 10 bar (150 psi).

I think the big problems you tend to face are that the temperature drop across the liquid-side boundary layer pushes your aluminum liner up pretty much to its annealing point (assuming you're using an alloy, which you pretty much have to for strength reasons); and then the relatively small temperature difference due to the heat flow makes it somewhat worse.

You might be able to ease that with curtain and film cooling though, but obviously then you're trading off that inefficiency against simply reducing the chamber pressure; but in most cases it's probably a win.

You also have to worry about warpage- running the engine will tend to anneal parts of the engine, and as it naturally cold anneals over weeks between tests, it can create distortions that stop the seals working properly, or could cause the engine to crack.

If you have access to a suitable oven, periodically dissassembling and reannealing the engine after use may be highly desirable; or let it distort and remachine it to fit.

Hope my (entirely theoretical) POV helps in some way.

Paul Breed said...

Its peroxide regen cooled, so I have lots of cooling fluid availible. Peroxide makes up most of the mass flow in the engine.

It will operated just fine in monoprop mode. I then can slowly add kerosene while watching the chamber pressure and performance.

If this does not work I'll probably go to a 310 stinless casting like Armadillo did.