Distance between turbine and pipe???
06-04-2007, 01:52 PM
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Distance between turbine and pipe???
Is there a formula to no the distance on how far to move the turbine in or out of the pipe?? In what position do you lose or gain power. The reason I am asking is because I think with the set up I have, weight against thrust. I feel the jet should have more speed. I no we are all looking for more speed but I am just wondering if my engine is in the right place. Any suggestions??
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Hoss
Thanks
Hoss
06-06-2007, 03:33 PM
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RE: Distance between turbine and pipe???
Hi Hoss:
To keep the inner and outer pipe cooled properly, you have to have clearance for cold air to get sucked into the inner pipe by the venturi produced by the hot gas outflow from the tailcone.....AMT NL for example recommends 6-8mm distance between the end of the tailcone and inlet to the bell or if not using a bell, then the inlet to the pipe itself......
Personally, I have found that anything between 1/2" and 1" works fine.....
As far as power goes, not much change unless you really stuff the turbine a couple of inches into the pipe, blocking the venturi flow....then you can get very high temps, turbulence, reduced power and even shutdown of the turbine due to overtemp.....
Also check the aft end of the pipe.....to get the proper venturi effect, the rear end of the outer duct should be mounted 3/8-1/2" back in the fuselage........this is the way BVM suggests setting up their very efficient bypass and pipes....I have my Titan in the BVM bypass/pipe in my big F-86 mounted that way and it has gobs of power and it runs cool.....
Tom
To keep the inner and outer pipe cooled properly, you have to have clearance for cold air to get sucked into the inner pipe by the venturi produced by the hot gas outflow from the tailcone.....AMT NL for example recommends 6-8mm distance between the end of the tailcone and inlet to the bell or if not using a bell, then the inlet to the pipe itself......
Personally, I have found that anything between 1/2" and 1" works fine.....
As far as power goes, not much change unless you really stuff the turbine a couple of inches into the pipe, blocking the venturi flow....then you can get very high temps, turbulence, reduced power and even shutdown of the turbine due to overtemp.....
Also check the aft end of the pipe.....to get the proper venturi effect, the rear end of the outer duct should be mounted 3/8-1/2" back in the fuselage........this is the way BVM suggests setting up their very efficient bypass and pipes....I have my Titan in the BVM bypass/pipe in my big F-86 mounted that way and it has gobs of power and it runs cool.....
Tom
06-07-2007, 05:54 AM
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RE: Distance between turbine and pipe???
Hi Hoss
If the pipe is a thrust pipe then it will have minute taper front to back. On the Wren44 a spacing of 15-25mm (nearer 25mm for me) is reconded to give an extra 1/2 to 3/4 lbs of thrust on this very small turbine. So imagine the turbine is drawing air into the flow with a reduction of area an increase in thrust is the output. I only know of Orbit in Germany who also make thrust pipes but they are twin walled.
Paul
If the pipe is a thrust pipe then it will have minute taper front to back. On the Wren44 a spacing of 15-25mm (nearer 25mm for me) is reconded to give an extra 1/2 to 3/4 lbs of thrust on this very small turbine. So imagine the turbine is drawing air into the flow with a reduction of area an increase in thrust is the output. I only know of Orbit in Germany who also make thrust pipes but they are twin walled.
Paul
