what i sthe best kerozene line configuration ?

[bmaaa]

Today I am using the following order in my kerozene line :

Tank ---- Fuel pump --- Electro Valve ---- filter ----------------------- motor.

But, it seems that I don't have enough kerozene flow. So, Can I CHANGE THE ORDER OF THE SETUP to have:

tank----filter----Electro Valve-----Fuel pump-----------------turbine ?

So that the tubling from the pump to the turbine is more free, and that no pression is lost in the 2 bottle neck that are the electro-valve and the filter ?

[Marty C...]

Hi Bertrand, Check that no air is leaking into your fuel system, that 'may' be the cause of your fuel flow problem? Also consider installing a header tank or UAT as this will stop possible air interupted fuel flow directly into turbine from header also check diameter of fuel pick up line/s and that fuel lines are consistant diameter throughout system..... see if this skymaster schematic systems layout may help....

Cheers-

[bmaaa]

thanks. I will look at air leak, but there is no room available in my twinjet for any additional airtrap tank

[Kelly W]

If you're worried about the overall restriction in the system, its like a bunch of electrical resistors in series. You can reorder them as much as you like but the restriction will be the same unfortunately.

The filter position is critical for 2 reasons. 1st, you need to be aware that a fuel pump itself will create debris in the fuel system, a little more so when its new or near end of life. The filter should be placed between the pump and engine for this reason alone. Secondly, if the filter were placed before the pump, upon collecting debris and increasing its restriction it can cause cavitation in the fuel pump. That can cause all sorts of problems from the irregular fuel flow into the engine, again more reason to place it after the pump. The pump's inlet should be as close to atmospheric pressure as possible for a healthy fuel system.

The shut off valve can go before, after, or one on both sides of the pump if you wish. Having it after the pump may cause a little more heat generation in the brushes due to the fact that the motor is effectively stalling when you close the valve while running. The advantage to using the valve after the pump is the net positive pressure on the o-ring seals. They are designed to operate with internal pressure, not a net vacuum. However, placing the valve on the inlet of the pump, so long as it has a reliable seal, does have one advantage. Upon closing the valve while the valve is running, the resistance to the inlet will instantly cause the pump to cavitate and run closer to a free wheeling condition. The current draw will be minimal and the valve won't see any undue wear since its still lubricated. If your valve has barbed fittings and the hose is wire wrapped, its probably best to put it before the pump although its not really critical.

So, what I'd do in your case is:
Tank ---- Electro Valve ------ Fuel pump ---- filter ----------- motor
Keeping in mind that the all fuel lines before the pump should be the largest reasonable size that you can use, and as short as possible. Since the Twinjet is very small, you can avoid the need for a UAT (or similar tank) by making your own fuel clunk with a pleated automotive filter in the main tank.

If a leak turns out to be the gremlin, eliminate festos on the suction side of the pump if you can and wire wrap (twice around) each barb fitting. If you must use a festo style connector, make sure its cut square with a SHARP exacto knife... That should do it in most cases....

Good luck with your project, and please post a photo! I have a twinjet, although it still flying as an electric... I'd love to see how you convert yours!

Kelly


Hey Marty, Its been a while since I've seen my rendered fuel system diagrams posted on the net... I really should update those with a UAT some day. Edit: I see you've since changed it for a 2D diagram...

[Marty C...]

thanks. I will look at air leak, but there is no room available in my twinjet for any additional airtrap tank

Bertrand, Do you have any pics of your turbine installation looking forward to seeing such a small setup.... were fast approaching the possibility of installing micro turbines into many of the smaller EDF aircraft.

Cheers-

[bmaaa]

Thanks for your detailed answers

as a matter of fact, the kolibri is now tested on my twinjet, but will end-up being inside an Aeronaut's panther.

http://www.bmichels.com/Images/Twinjet_kolibri.jpg

http://www.bmichels.com/Images/200gr_MicroTurbine.jpg

http://www.bmichels.com/Images/MonTwinjet3.jpg

http://www.bmichels.com/Images/MonTwinjet4.jpg

http://www.bmichels.com/Images/Test_kolibri.jpg

[Pyolet]

Also test that the electro valve is not malfunctioning/restricted. Bypass the valve, run the engine and see if you have the same problem. I've had two fail "out of the box" in the last year. Woody.

[Kelly W]

That conversion look great! I really like the integrated fuel tank! I'm amazed how much hardware you're able to cram in the little space that's available...

How much did the overall weight increase by from the electric configuration, and how much thrust will you get from the turbine?

I should have mentioned earlier for those just entering the turbine area of the hobby, the electro valve we spoke of should always be in series with a manual shut off valve, since as Woody's just pointed out they can fail. There's no guarantee it'll fail in the open or closed position and you always want some sort of emergency shut off that doesn't include unplugging the battery.

Again, looks great! Very clean looking conversion...

Kelly

[bmaaa]

The turbine weight 200 grammes by itself. Weight increase over electric is none since the ready-to-fly plane, EMPTY, is 950 grammes. With 2 electric motors and big batteries it will not be less !

I will try to by pass the valve to test it

[ronmeister]

That twin jet looks so awesome!