Well, this is fortunate-- I've been working on some fiction stories where valveless pulsejets play a fairly major role, but haven't been able to find out one answer while doing research: Can they be throttled? Is it possible to increase or decrease the thrust of a pulsejet, or are they pretty much "all or nothing?" in their operating range? I hope this isn't misusing the forum, but I haven't been able to find the information elsewhere.
Thanks so much for your help!
Varying the thust in a pulsejet
Moderator: Mike Everman
-
Johansson
- Posts: 1161
- Joined: Sun Nov 21, 2004 9:42 pm
- Antipspambot question: 0
- Location: Northern Sweden
Re: Varying the thust in a pulsejet
Yes you certainly can, a badly designed engine has less throttle range than a well designed one but it is always possible to alter the thrust output. If you want to read some more about these marvelous contraptions you could start by reading Bruno Ogorelec´s well written pulse-jet history.cgray45 wrote:Well, this is fortunate-- I've been working on some fiction stories where valveless pulsejets play a fairly major role, but haven't been able to find out one answer while doing research: Can they be throttled? Is it possible to increase or decrease the thrust of a pulsejet, or are they pretty much "all or nothing?" in their operating range? I hope this isn't misusing the forum, but I haven't been able to find the information elsewhere.
Thanks so much for your help!
http://www.pulse-jets.com/download/insi ... orelec.pdf
You are welcome, as payment we demand that you post your writing here when it is finished. Just imagine a fiction story about pulse-jet engines, can it possibly get any better than that?
-
Rossco
- Posts: 589
- Joined: Fri Nov 28, 2003 12:16 pm
- Antipspambot question: 0
- Location: Australia, Brisbane
- Contact:
Re: Varying the thust in a pulsejet
A couple of notes to also consider when presenting a depiction or description of pulsejets.
They do not spool like turbines. Everyone here knows who im thinking of. "dragster" whiiir whrrrrrriiiiiiiii, "im a jet"
With increase in throttle and power a pulsejet just gets louder at basically the same frequency. They do "bite in" a bit, and the frequency can vary a little depending on how extreme the throttle percent is although the shift is more a change in timbre. Getting to know these variations is called "an easy starting engine"
(in house joke)
Have a look at some videos to get the feel for them, even better, build your own, we can help.
It is a very distinctive sound that only varies between engines subtly. Small ones scream at a much higher frequency (probably obviously) although all "useful" (presuming thrust use) sized engines will be big, monstrous in fact, have a lower frequency and higher amplitude. A historical flight engine (valved) is the Argus which pushed the German V1 flying bomb. It had a thrust from 500 to 800lbs at a frequency of around 50Hz, which must have been absolutely gut wrenching.
When near a big engine and especially around the output, the sound is felt more than heard, and is literally mind numbing and organ damaging. It is an exhausting experience operating big engines for any length of time.
If you start getting into multiple engines, you get "beat frequency". This multiplies the above effects greatly. An awesome but sickening effect.
Welcome to the forum, we're a pretty friendly bunch mostly and you are not misusing anything unless you depict a PJ spooling!
We try not to be as touchy as some other forums that will lock threads for using any word not in direct relation to the subject (grumble grumble)
Let us know a bit more of what your doing. "valveless pulsejets play a fairly major role" sounds very interesting.
Rossco
They do not spool like turbines. Everyone here knows who im thinking of. "dragster" whiiir whrrrrrriiiiiiiii, "im a jet"
With increase in throttle and power a pulsejet just gets louder at basically the same frequency. They do "bite in" a bit, and the frequency can vary a little depending on how extreme the throttle percent is although the shift is more a change in timbre. Getting to know these variations is called "an easy starting engine"
(in house joke)Have a look at some videos to get the feel for them, even better, build your own, we can help.
It is a very distinctive sound that only varies between engines subtly. Small ones scream at a much higher frequency (probably obviously) although all "useful" (presuming thrust use) sized engines will be big, monstrous in fact, have a lower frequency and higher amplitude. A historical flight engine (valved) is the Argus which pushed the German V1 flying bomb. It had a thrust from 500 to 800lbs at a frequency of around 50Hz, which must have been absolutely gut wrenching.
When near a big engine and especially around the output, the sound is felt more than heard, and is literally mind numbing and organ damaging. It is an exhausting experience operating big engines for any length of time.
If you start getting into multiple engines, you get "beat frequency". This multiplies the above effects greatly. An awesome but sickening effect.
Welcome to the forum, we're a pretty friendly bunch mostly and you are not misusing anything unless you depict a PJ spooling!
We try not to be as touchy as some other forums that will lock threads for using any word not in direct relation to the subject (grumble grumble)
Let us know a bit more of what your doing. "valveless pulsejets play a fairly major role" sounds very interesting.
Rossco
Big, fast, broke, fix it, bigger, better, faster...
[url=callto://aussierossco]
[/url]
[url=callto://aussierossco]
[/url]-
hinote
- Posts: 1241
- Joined: Sat Oct 04, 2003 1:54 am
- Antipspambot question: 0
- Location: Central California
Re: Varying the thust in a pulsejet
Based on my own experience and the similar experience of others on this forum, I can state the following:cgray45 wrote:Well, this is fortunate-- I've been working on some fiction stories where valveless pulsejets play a fairly major role, but haven't been able to find out one answer while doing research: Can they be throttled? Is it possible to increase or decrease the thrust of a pulsejet, or are they pretty much "all or nothing?" in their operating range? I hope this isn't misusing the forum, but I haven't been able to find the information elsewhere.
!
It IS possible to construct and operate a valveless pulsejet that will sustain itself while producing zero net thrust. As is true with most good designs, it can also be throttled rapidly up to max power and back down again--almost as fast as you can operate the lever.
Additionally, the fuel consumption at "zero net thrust" can be remarkably low if the correct fueling hardware is employed.
I doubt that any other forms of pure jet power can make similar statements based upon actual operation.
Bill