Could a Valveless Pulse Jet Engine Eliminate the Need for Moving Parts?

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Discussion Overview

The discussion revolves around the concept of valveless pulse jet engines and their potential advantages, particularly the idea of eliminating moving parts. Participants explore various aspects of these engines, including their operation, comparisons to other jet types, and practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that valveless pulse jets could operate without moving parts, contrasting them with traditional pulse jets that have one moving part.
  • Others compare valveless pulse jets to ramjets, noting that they do not require supersonic speeds to function.
  • A participant mentions that the turbulence caused by the design of the inlet is preferable for these engines, indicating a need for further analysis.
  • There are claims that thrust is generated from both nozzles of the engine, but in unequal amounts.
  • Some participants express interest in building their own versions of these engines, sharing links to resources and plans.
  • Concerns are raised about the operational limitations of valveless pulse jets, including their power range and potential applications.
  • Participants discuss the historical context of pulse jets, particularly the V1 engine, and its need for a launching ramp, with some questioning the accuracy of previous statements regarding its operation.
  • There are mentions of the valveless pulse jet's use in modern technology, such as drones and cruise missiles, but uncertainty remains about the full understanding of this technology.
  • Some participants express skepticism about the practicality of valveless pulse jets, questioning where they could be effectively utilized.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the practicality and applications of valveless pulse jets, with multiple competing views and uncertainties expressed throughout the discussion.

Contextual Notes

Limitations include unresolved questions about the operational range of valveless pulse jets, the specifics of their combustion cycle, and the accuracy of historical claims regarding the V1 engine's operation.

Phrak
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What, not inpressive? These things actually work.
 
Check it out. These jets will run on a static platform. There are a dozen other YouTube videos by various amatures.

https://www.youtube.com/watch?v=5U-grFuXZ9U



For the combustion cycle, see Wikipedia.
 
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Brilliant! Like a ramjet but doesn't need supersonic speeds to operate - just a resonant inlet. I'm surprised the inlet doesn't face forwards. Does anyone know why?
 
I did a bit of reading into it. It seems that for these size, the turbulence caused by the bend is preferable.

Neat idea, I'd love to see some good analysis on it.
 
It appears that thrust is developed out of both nozzles, though in unequal amounts.
 
Smart!
 
  • #10
The only snag with them would be that they will only work over a small range of powers, I expect and where would you use one? (Apart from just to prove it worked)

I suppose you could always use them to send bombs or boxes of sweets to a neighbouring country LOL.

From the movie, it seems that it works from a standing start, whereas the V1 pulse jet needed to be launched in order to get it going.

Actually, you could use two such engines on either end of a long rotating arm and get a rotary motion. (mind your head!)
 
  • #11
the people at the madagascar inst have used them to power a merry go round
I was wanting to build one as a high temp source. being as O2 is completely consumed the main exhaust is pretty oxygen free. I was wanting to use it as my heat for melting aluminum cans into ingots. at 130+ db, it sure would get the neighbors attention lighting the bbq smoker pit with...lol
the plans i have are for one that builds about 2 lbs of thrust
lots of plans on the net

dr
 
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  • #12
sophiecentaur said:
The only snag with them would be that they will only work over a small range of powers, I expect and where would you use one? (Apart from just to prove it worked)

I suppose you could always use them to send bombs or boxes of sweets to a neighbouring country LOL.

From the movie, it seems that it works from a standing start, whereas the V1 pulse jet needed to be launched in order to get it going.

Actually, you could use two such engines on either end of a long rotating arm and get a rotary motion. (mind your head!)

I'm impressed by the simplicity, although 120 decibels (exaggeration) is a drawback, and the fact that they will apparently melt if run continuously.

There are a few variables that can effect the power band/fuel consumption. Changing the frequency by varying the length of the longer tube, the re-ignition tube, is one of them.
 
  • #13
sophiecentaur said:
The only snag with them would be that they will only work over a small range of powers, I expect and where would you use one? (Apart from just to prove it worked)

I suppose you could always use them to send bombs or boxes of sweets to a neighbouring country LOL.

From the movie, it seems that it works from a standing start, whereas the V1 pulse jet needed to be launched in order to get it going.

Actually, you could use two such engines on either end of a long rotating arm and get a rotary motion. (mind your head!)

V1 engines didn't need speed to work according to

http://www.youtube.com/watch?v=v8PF5DtX_Fg&NR=1

where authentic V1 engine is started. As if a since long dead mummy is awaken.

The late valveless pulse jet engines are said being used in some cruise missiles and drones.
But scientists and engineers are reputed not fully understand and master this technology.
 
  • #14
From one you tube video the V1 appears to have used a ramp and rocket assist takeoff. Can anyone confirm a rocket assist? It may be that forward airspeed effects engine tuning and thus power output. What I mean is that if the fuel is metered for cruse speed it may not have enough power for takeoff from a standing start without an inconveniently long launch ramp.
 
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  • #15
There is a detailed description of V1 technology and operating in seven parts (p1 - p7) in youtube. (Originally used as instruction for Nazi officers?)

In this video (p4) the launching technique is explained
http://www.youtube.com/watch?v=-XiRkk4zYtU&feature=related

In this video (p5) the V1 is launched
http://www.youtube.com/watch?v=Kcup3W6uy_E&NR=1

So the V1 engine is started before launching but has not thrust to accelerate
sufficiently fast without help from a pressure-driven piston in a cylinder in ramp.
 
  • #16
sophiecentaur said:
From the movie, it seems that it works from a standing start, whereas the V1 pulse jet needed to be launched in order to get it going

With no offense to anyone, I'm simply too tired right now to read all of the posts in their entirety or look at any of the links at all. I promise to do so in the next day or so.
For now, though, I can definitely state that the quoted statement is in error. The V1 used a launching ramp to eliminate a runway and the wheels to utilize it. (The Natter used essentially the same ramp, but that was a whole different bird.)
While the war was still under way, instrumentation showed that something like 85% of the fresh intake charge for the next firing cycle of a pulse jet was sucked in through the tailpipe instead of the shutter-valve box in front. It didn't take long after that to work out that the dynamics within the chamber could be tuned to provide a variety of operational responses. The valveless version is based upon (maybe not the proper technical term) a "standing" shockwave, that is formed by the combustion pressure itself, sealing off the front of the chamber.
 

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