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“Aerodynamic valve” for valveless pulsejet.

Posted: Fri Jul 09, 2010 4:38 am
by parabellum
Have somebody tried to incorporate one “aerodynamic valve” (it is not a real valve, before you send me to thus valved jet guys) in the intake on valveless jet with the purpose of partially force direction of airflow and raise exhaust pressure? In case of success it will open new possibilities of tuning exhaust and combustion chamber form (in order to get more thrust), without big influence on intake. I am new here and I spent a week reading valveless and valved jet topics first, before placing dumb questions, anyway maybe I missed something or do not understand some basic rules of pulsejet. Please enlighten me. :?:

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Fri Jul 09, 2010 7:50 am
by metiz
Valveless pulse-jets are all earodynamically valved. The intakes on any working valveless pj's are tuned in such a way that the let the engine run. A simple hole would not do

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Fri Jul 09, 2010 1:39 pm
by parabellum
Yes, I understand that, but every modification of existing engine can break this balance. The incorporation of aerodynamic “one way” valve (is not about a bunch of holes like you can see on this “aerodynamic valves jet patent” on internet) will open tuning opportunities for performance. What about aerodynamically calculated intake duct, which can create contra pressure in one direction? I think it is possible to force the engine to produce pressure, not only thrust. Sorry for my bad English.

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Fri Jul 09, 2010 1:56 pm
by metiz
Tesla had a system like that. it had vanes in the intake that reversed the flow back into itself. It works to some extend. Still not as good as a mechanicall valve or simply pointing the intake backwards

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Fri Jul 09, 2010 2:38 pm
by parabellum
Have somebody tried to use it? If I’m right, Tesla invented this valve for other proposes first and time after created design especially for valveless jet, but never get chance to use or try it. His valve is not perfect (because they was no today’s technologies then) but even so it has (do not know the right words) ~1:1.2 (pressure resistance ratio) for normal air at see level. Mathematically seen, by using 4 of this valves in chain it should double resistance 1 way, unfortunately I am 0 in aerodynamics.

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Mon Jul 12, 2010 9:11 am
by Bruce Simpson
Tesla's valve is too soft to be of any use in a pulsejet.

By "soft", I mean that it accepts a lot of incoming flow, even if only a little flow makes it to the outlet. This effectively reduces the combustion pressures in side the engine and so reduces efflux velocities, hence thrust.

I played around with Tesla's design for a while before realizing that it was never going to be anywhere near as good as simply redirecting the output flow and tuning the intake duct.

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Mon Jul 12, 2010 6:30 pm
by parabellum
Thank you for explanation! I really do not need thrust I’m locking for pressure in order to convert it in to torque. One unidirectional gas flow (like in valved pulsejet) will be perfect. Is there a way to use valveless pulsejet for? Maybe I should start other topic?

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Wed Jul 14, 2010 11:46 pm
by Bruce Simpson
Thrust and pressure (for a given masflow) are inextricably linked so the softness of the tesla valveless conduit would also affect the ability to drive a turbine or other means of converting pressure to torque.

Besides which, pulsejets may have many positive attributes (simplicity, low cost etc) but efficiency is not one of them so anything that further reduces that efficiency (such as a soft valving system) doesn't help at all.

Re: “Aerodynamic valve” for valveless pulsejet.

Posted: Thu Jul 15, 2010 12:49 am
by parabellum
Thanks! Now I will have more time to build e jet without spending it in one not working valve system. :D