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Author Topic: What is a rotary pulse jet engine?  (Read 44727 times)

Offline McQueen

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Re: What is a rotary pulse jet engine?
« Reply #75 on: 22/05/2008 11:10:00 »
The CR4 engineering site were stumped, I can tell you that I had received about 400 e-mails from the forum while the subject was hot!!! Unfortunately the most positive aspect of the discussion was that they wanted me to build a working proto-type!! Well you all know how expensive that is!!! Apart from that opinions were divided. One great plus point is that they even offered to pass around the hat , so that I could build a prototype.
 

lyner

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Re: What is a rotary pulse jet engine?
« Reply #76 on: 23/05/2008 21:12:19 »
Have you actually received any money from them yet, tho'?
If you have then I must remember to include them in my list of possible investors in my perpetual motion machine design.
 

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Re: What is a rotary pulse jet engine?
« Reply #77 on: 23/05/2008 22:04:31 »
On the topic of efficiency of a reaction engine.
The Momentum formula : m1v1 = m2v2 is correct, of course; the mass of ejected gas being much less (per second) than the mass of the vehicle.. What is more relevant, however, is the actual POWER / ENERGY transfer.
The KE is mvsquared/2.
So the share of energy imparted to the vehicle is, actually, VANISHINGLY SMALL when its velocity is low; most of the energy going to the propellant gases (the 'square' factor making all the difference in this matter). As the vehicle gets faster, the share of the Energy it gets (the efficiency) goes up.
 

Offline McQueen

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What is a rotary pulse jet engine?
« Reply #78 on: 24/05/2008 06:04:28 »
Hi. Sophiecentaur,
Quote
So the share of energy imparted to the vehicle is, actually, VANISHINGLY SMALL when its velocity is low; most of the energy going to the propellant gases (the 'square' factor making all the difference in this matter). As the vehicle gets faster, the share of the Energy it gets (the efficiency) goes up.


I donít blame you for doubting my conclusions, however you might perhaps think twice about conclusions drawn by Robert Goddard, namely that not only would a rocket generate the same type of impulse power as a piston engine but that it would do so more efficiently. In drawing these conclusions Goddard had made use of the same type of experiments that I myself have been carrying out. Here is what he has to say:  ďIf, however, successive charges were fired from the same chamber, much as in  a rapid-fire gun, most of the mass of the rocket could consist of propellant, and the superiority over the ordinary rocket could thereby be increased enormously. Such reloading mechanisms are the subject of all the above patents except the first, which is chiefly concerned with the nozzle, and what I have termed a "primary and secondary" rocket principle. I have not made a working model of a reloading device, as it is the one feature of the method that is self-evidently operative.Ē  I think that you will be struck by the similarity in this idea and that of the Rotary Pulse Jet Engine.  More information on Robert Goddard including the above passage can  be found at: http://siarchives.si.edu/history/exhibits/documents/goddardsept1916.htm
Unfortunately ofcourse Goddard was never able to implement his ideas in a practical way and so didnít receive a patent for his idea, he did however go on to make his mark with liquid fuelled rockets.

 

lyner

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What is a rotary pulse jet engine?
« Reply #79 on: 25/05/2008 12:08:35 »
MQ
Goddard was a conventional engineer who was clever and very successful. None of his views needed to violate the conventions of Mechanics and Dynamics. I think there could be a problem with your interpretation of what he had to say.
btw, I can't find any reference tp pulse jets in his paper.
« Last Edit: 25/05/2008 12:35:08 by sophiecentaur »
 

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What is a rotary pulse jet engine?
« Reply #80 on: 31/05/2008 11:09:17 »
Hi SophieCentaur, I may have a surprise for you from which you won't recover!!! Especially if you stick to your present stand!
 

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What is a rotary pulse jet engine?
« Reply #81 on: 31/05/2008 11:13:34 »
Quote
The Momentum formula : m1v1 = m2v2 is correct, of course; the mass of ejected gas being much less (per second) than the mass of the vehicle.. What is more relevant, however, is the actual POWER / ENERGY transfer.
This is the veriest bullshit! And I can tell you this based on my experiments. The RPJ builds up tremendous pressure before exiting the gases, during which velocities are out of sight. In my next post I will quote from an Encyclopaedia Brittancia article!
 

lyner

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What is a rotary pulse jet engine?
« Reply #82 on: 01/06/2008 21:28:35 »
That particular bull must have been a particularly learned one. If you think that it is force and pressure that count when you are trying to transfer energy to do 'work' then you will also believe in perpetual motion machines. There is no hope for you, my friend.
 

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What is a rotary pulse jet engine?
« Reply #83 on: 02/06/2008 14:39:58 »
OK Sophiecentaur
I am sorry for the S word in the last post. But if you look at the encyclopaedia under ballistics, I think you will find that explosives just after ignition travel at something like a 100,000 km hour, so even taking your moth eaten mv formula, the RPJ would win by a wide margin!! Lets face it the piston engine is hemmed in by its short stroke and the complete end to power of its stroke therein!!!
« Last Edit: 02/06/2008 14:42:21 by McQueen »
 

lyner

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What is a rotary pulse jet engine?
« Reply #84 on: 02/06/2008 18:47:50 »
The two engines are very different, of course. But the reaction engine is, essentially a momentum transfer mechanism - the relative shares of the energy between propellant and rocket are determined by relative masses and speeds. Momentum is conserved so, for low rocket speeds, the efficiency just has to be poor. That doesn't necessarily matter but you could at least acknowledge it.
The piston engine transfers its energy as a gas moves a piston load under  pressure over its stroke.  It has several shortcomings -  theoretical and where thermodynamics meets engineering reality. It performs reasonably at relatively low revs, which is a particular advantage in that the gear ratios need not be too great. So it is not possible to compare their operation step by step. You need to look at the bottom line figures of power and efficiency of two practical, working systems.
A number of people have pointed out aspects in which your RPJ throws energy away. You have to address that, either by a demonstration or reasoned argument with proper use of terms and calculations (the more likely way in the case of your proposal).
It is best compared with a gas turbine (another high revving engine) but that has really been a non starter for ground transport (when did you last see one driving round town?).

We can have a sensible conversation (on any number of threads) as long as you use the correct terms and don't suddenly take off on expressions like "tremendous force" which, taken on its own, means nothing.

My learned bull didn't take offence, btw.
Also, Britannica is very limited in its technical content in several directions. There were a large number of 'howlers' when I last looked at the details of Television signals and coding.
« Last Edit: 02/06/2008 18:50:52 by sophiecentaur »
 

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What is a rotary pulse jet engine?
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