N2O/Ethanol bipropellant rocket engine

[Johansson]

Thanks Carl, my plan is to do the water flow tests this weekend and hopefully get a bottle of NOX filled in a couple of weeks. It would be great if I can do the test firing before the snow arrives.

Interesting theory about the pressure sensor location, I haven´t really given it much thought and with my engine design it is not very practical to fit it anywhere else but through the injector plate.

My biggest concern right now is if the air regulator flows enough to keep a steady tank pressure while they are emptying, so the next test will be an interesting one.

Cheers!
/Anders

[britishrocket]

Hi Anders,

I hope you manage to get the engine fired before the snow comes. Will be a great sight I am sure.

I don't think it makes a huge difference where the pressure sensor is sited on small engines, I just wonder if it would be a noticeable one.

I hear what you are saying with regard to the regulator. I have a pressure regulator that I bought from BOC and I used/use it in my injector experiments. I was using it to flow nitrogen gas through the annullus of my injector at 100 psi and it did struggle a bit to maintain a constant pressure.

I'm interested to see how your regulator gets on compared to mine.

Best wishes,

Carl.

[Johansson]

Especially when the regulator I use can be bought for 50 USD, I regret not buying more of them at the same time to save up on postage.

[mator]

Oct 8, 2012 7:42:15 GMT -5 britishrocket said:

I have thought a lot about where the chamber pressure sensor ought to go myself. In theory I think it should be sited a little before the convergent portion of the nozzle. At this point the reaction should be fairly complete and the pressure stable. Apparently the pressure can spike up a little as the gases enter the convergent portion.

I just have payed attention on this post. I am sure that pressure sensor must be placed nearly with injectors.
I based on Bernoulli principle: in place, where speed of liquid flow higher the pressure is lower. Do anybody knows diagram of pressure in rocket engine chamber?

Here it is. In area, where speed of flow minimal, the pressure is maximal. Maximal speed is in exit of nozzle, but pressure is minima (ideally it must = pressure of external atmosphere, for our engines it is air pressure at sea level) So, from this diagram we can se that pressure is maximal near injection plate. Also near throat temperature higher and maybe it is not so good for pressure sensor. But only maybe, I dont know which one is used by Anders)))

[Johansson]

I did the water flow test this evening and everything went well.

First I plugged the propellant lines going into the rocket engine and pressurised the system to 60 bar to see if there was any leaks. None were found so the plumbing is ok.



The thrust chamber was overhauled with new O-rings before being fitted to the test rig for the flow test, not really necessary for a water flow test but I have lots of O-rings...



The test was done to find out if the high pressure regulator could hold a steady tank pressure while running the engine, I set the tank pressure to 40 bar, opened the main throttle valve and found that the pressure was rock solid throughout the run despite the fact that the scuba tank pressure dropped to 50 bar at the end of the run.

(sorry for the jibberish language, it just feels strange to talk english to a camera...)



The regulators are sold for 50 bucks so hurry up and buy one before they are all gone, I don´t even dare thinking about how much these regulators cost when they were new...

aeroconsystems.com/cart/aerocon-specials-closeouts-one-of-a-kind/special-5-grove-tescom-apco-reducing-regulator/

Cheers!
/Anders

[britishrocket]

Hi Anders,

I gave in. I bought one.

[Johansson]

You won´t regret it.

[Johansson]

Today I put some paint on the test stand and tanks, unfortunately the "custom paint job" on the water tank is buried under two layers of zink paint but I think every woman at the race will applaud the decision.





Cheers!
/Anders

[racket]

Hi Anders

LOL........a much more respectful paint job ;-))

Cheers
John

[mator]

Das ist Fantastisch!!!!!!!
Many famous designers (A.N. Tupolev or S.P. Korolev and I sure all other...) said that if product (rocket or plane) looks good, if it is nice, it means that it can be very good by its technical characteristics)))
Have you ever seen ugly plane? )))

It will be much more nicer if oxidizer tank will be blue and fuel - red. For women you have to paint all your engine pink, and decorate it fith flowers and rhinestones "svarovski" and diamonds))))

[ernie wrenn]

Well the tanks are painted Kotex red. Now all you need is a short string attached to the end..

ernie

[britishrocket]

Hi Anders,

I am now regretting something. And that is that I didn't get one sooner. They haven't got any left!

[Johansson]

I assembled the engine this evening and it sure looks less crude now than when everything was bare metal. The colours work well together so all that is needed now is some heat discolouring and sooty fingerprints.



I didn´t paint the engine coolant jacket since I might have to rebuild it later, it has some sort of coating so it won´t rust anyway.



As the coolant I am considering using windscreen washer fluid, it won´t freeze and if I spill some at the race lake I won´t get in trouble with the safety crew. If I used glycol that would be a big problem since the lake is a drinking water reservoar...

Cheers!
/Anders

[sven]

Maybe its better using water mixed with ethanol, cause washer fluid have cleaning components inside(soap) its gonna start throw some bubbles out Racing ethanol isnt expensive and you can mix you own mixture with water.
By the way your rig looks good, have a good first start and dont forget take video

Sven

[Johansson]

Good idea Sven, any foaming inside the cooling jacket would probably cause a meltdown due to poor cooling.

I rebuilt the pressurisation system today. Again. Now I have a separate fill valve for the NOX and a one way valve that stops the NOX from getting into the methanol tank, should do the trick.



With that done I filled the coolant system with water and tested it for leaks, no leaks found and a decent flow through the engine so hopefully it will be enough to keep the aluminum thrust chamber from melting.



Next up is to build the ignition, then the engine should be ready for a test run!

Cheers!
/Anders