Pressurizing Kerosene
 

Hi, the reason i am posting this thread in this forum is because alot of you know very much about refrigerator and ac compressors.

Here is my dillema. I have built a small gas turbine engine out of automotive parts (turbo charger) and I currently use propane as a fuel because it is already in a gaseous state at stp. I now wish to move to kerosene (cheaper and more adequate for the job) but the liquid needs to be pressurised so it can be shot out of the fuel nozzles as a gassous substance.

Now i have been looking at refrigerator compressors and i know that they compress freon to form a hot liquid. Could I use it to compress kerosene?

Thank you very much for any help

That's pretty wild! Reminds me of the jet engine for RC models in South America, stalled for lack of funding, just begging to hit the market! The first implementation of those jet engines (that I know of) used a turbo unit from a motorcycle.

The compressor relies on oil for lubrication, which is matched to the refrigerant.

Do you really need that much pressure?

See the thing is I use normal propane now, but i can only get it up to 2-3 bar. That gives me about 50k rpm and a very hot exhaust temp. If i can get kerosene pressurized I can get much more rpm, which means much more air flowing through the compressor, stabler exhaust gas temp and more thrust (also more sound to impress the neighbors :))

So what you are saying is that the oil line of the compressor is mixed right with the freon? So i'd have to mix the kerosene with the oil?

Yeah, unfortunately. I don't know how well the engine would work with the oil added to the fuel. Might be good, might be bad.

It'd be pretty "far out" (outside of the intended purpose), so it'd be hard to tell what mixture of oil would save the compressor. I'd try it out with a junked compressor first, if I was you, with various mixtures, and different oils.

Do you plan to use any kind of spray or atomizing nozzle, for this kerosene?

May I ask what's the purpose of that engine?

I'm using the kerosene as a fuel big ben. The kerosene goes directly from the compressor to the fuel injectors and gets burned. It would be impossible to have to keep on mixing oil with the kerosene. Plus i wouldn't want to burn oil anwyas. Is it possible to find a compressor with a dedicated oil feed?

Nicozeg, i plan to hook up the engine to an ultralight. Or maybe a very big remote controlled helicopter or plane.

Have you thought about using a fuel pump from a fuel injected car? That should give you the pressure for kerosene. A freon compressor weighs too much for when you start the aviation activities and your will need a source of 110 AC to run it.

What are you going to use for a reduction drive for a propellor/ rotor?

A fuel pump from a car might pulse, and give some unpredictable results, but it might be worth a shot.

Thank you all for your replies.

I have abondened the fridge compressor idea because of the power usage and you have to have an oil flowing with it. Ezlid I already use an automotive oil pump to power my oil system (need continuos oil flow through the turbocharger) so I guess i could strap on an automotive fuel pump, but if i do i have to go look for .5 hp electric motor to get a nice pressure on it and thats another big pain in the arse.

Ben what are the pumps that you are talking about?

And I've been thinking that i can just can fuel tanks inside my craft and "pre pressurize" my fuel before take off. That would save me from lots of problems trying to fit everything and setting up the dc power and such.

Ezlid right now i am not sure whether to use mechanical energy or thrust. I am kinda leaning towards thrust but i am not sure. If i can figure out a nice way to set up a very stable coupling and find some small reduction gears I'll go with mechanical to power a prop.


Thank you all for your replies btw.

I was following up on EzLid's suggestion, of an automotive fuel pump. They're noisy, run on 12 volts, and "pulse" which, like I said, might end up being unpredictable in your application.

I've been toying with RC for more than ten years, and I really don't think you want to put a pump onboard, and the set of batteries that it's going to require, because of the humongous weight that it's going to add.

Is there any way that the engine could drive a pump?

Ben as of now, the engine would be too fragile to draw mechanical power from it. Right now I am looking to find pressure pumps (if they exist) so I can pre pressurize my fuel before takeoff. Anyone know anything about these?

I thought that some people are already running kerosene in their gas turbines(built from turbochargers).

In some cars on the fuel rail where the fuel line comes from the fuel pump, they have "dampener" specifically to eliminate the "pulse" from being seen by the injectors on the fuel rail. Might be useful in this application as well...maybe a small tank...

BTW, Automotive fuel pumps run 38 PSI or somewhere around there.

BTW Pt 2...got pictures?

I think we need a little more info, F18.

Are you planning on any type of throttle or just let the engine run at full speed? If no throttle, the pressurized tank should work. But as the tank pressure bleeds off the flow will be reduced and slow the engine. A regulator could be used to stabilize the flow and increase run time. In essence, over-pressurize the tank and use a flow/pressure regulator to supply a nice, steady state flow and pressure for a longer time.

Are you using a fuel injector or just an open atomization nozzle? The open nozzle gives no control, while an injector could be used for at least on/off to give a minimum of engine control.

On my auto fuel pump idea, I was thinking of a high pressure fuel injection pump. Yes, low pressure pumps for carbs do pulse, but the float and fuel bowl is the regulator, if you will. F. Inj. pumps don't have as much pulsation and aren't as noisy. I think a regulator would be helpful.

One problem with a pressurized tank is the natural bleed in pressure and you run out of pressure long before you run out of fuel. At least a pump will allow the use of a full tank of fuel.

To pressurize the tank, you could put a sharader valve (tire stem) in the tank and use one of the small 12 VDC air pumps to pump to just about any pressure you want. A bladder might be useful, too.

I asked about reduction for prop/rotar drive because I think you will be disappointed by the thrust developed. And I could very well be off-base on that.

Have fun and give your neighbors a six pack so they they don't complain too much about the noise.

Got oics?

Ok let me address some things about the questions you guys asked me.

Throttle:

The current throttle configiguration right now is extremely simple. I have a propane tank which has a valve connected to it. This valve regulates the flow of this gas pretty well. There is a gas line from the propane going to a butterfly valve (safety shut off). The gas line then goes directly to a distributer ring (just a small pipe in the flame tube shaped like a circle with with 6 smaller pipes which sever as fuel nozzles connected to it) and then out through the nozzles. The nozzles are nothing more than small openings. (Same thing like a burner on a stove). I am currently able to regulate the flow of propane from the valve on the tank with good results.

Kerosene:

Kerosene, aka jet fuel, is a much better fuel for gas turbines (turbojets,fans,props) becuase it if creates more energy than propane when mixed with high amounts of oxygen and burned. My current propane setup is not too good for any other purpose other than display, and I want to change that. The problem with kerosene is that i need to pressurize it because I can't just shoot it out of nozzles as a liquid because it will not mix well with Oxygen and it will just set my turbine on fire. If I can compress the kerosene to 10bar and send it through nozzle (I would have to buy a new fuel injection nozzle and make the opening smaller) it would disperse into small particles and easily and more efficiently mix with the oxygen.


I figured out that the only thing i really need is a fuel primer pump. Looked on ebay and what did i find? An aviation fuel pump for only 50 bux.

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2428531979


Now the only thing left to figure out is how to implement a throttle control system with the pump. I was thinking eaither get a valve between the pump and the nozzle, or just control the pump's amprage.

Sorry, no pics atm, but i will try to get some.

You need a afterburner like Nye Labs.

F16 - That pump is 61 years old and the seller doesn't even say if it works or the pressure rating. An aircraft primer pump is not high pressure, all it is used for is squirt a small amount of fuel into the cylinders to give a rich mixture to to start a cold engine. And it is 24 VDC. Take your fifty bucks and go to a junk yard and buy a 12 volt pump from almost any fuel injected car and you will be better off. You might be able use a higher current fan control type circuit to control the pump.

For throttle you could make 2 or even three valved fuel rails with a different number of nozzles, say 3 for an idle rail, 6 for mid-range and maybe 8 for full throttle. Vary speed by using any combination of the rails. The nozzles could be simply very small, like pinholes, drilled into the fuel rails. Just bouncing ideas.