Saturday, May 28, 2011

The Begining of an Evaporative Fuel System

A liquid-fueled DIY gas turbine poses one fundamental challenge. Diesel fuel (this engine's fuel), Kerosene, Jet-A, etc. all need to take the form of an atomized vapor before being burned. In commercial aircraft, this atomization is achieved via high-pressure (~1000 psi) fuel injection system, and a special injector.
Unfortunately, a 1000 psi fuel pump would cost a pretty penny which I don't have, and gobble up lots of onboard power, which I won't have.
The solution to this conundrum lies in evaporation. The fuel will dribble out of a nozzle into a "tree" of 3 small stainless steel tubes, which are heated by the combustor. The diesel or kerosene fuel vaporizes quickly upon contact with the hot metal, and the resulting vapor burns easily in the combustor.
I plan to incorporate the "evap" system into the flame tube (the tube somewhat resembling Swiss-cheese inside the combustor which allows the fuel to burn with an even supply of air). For this, I will start with a 3.84" diameter, 3 inch tall "can" with a large hole in the side. This will mount to the end plate of the combustor, feed air to the evap "tree", and support the flame tube, which will fit snugly around it.
 With much cussing and a little blood, I milled two 3.84" stainless circles on my undersized rotary table, then drilled 6 holes to the front of which nuts will be welded. This is the "bottom" of the evap can, which will fit over the 2 fuel injectors (starting and main fuel).
 Here drilling corresponding holes in the combustor end plate.
The finished ring. I also milled a full circle of the same diameter, which will be used as the top of the can.
Heres the end plate installed back on the engine. Looking a little more complex :)
And last but not least, its my pleasure to welcome the newest member of the Feathers workbench, a harbor freight belt sander :). Should get some nice use out of this piece.

Check back soon!

2 comments:

  1. nice blog and good posting
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