85% throttable pulse jet engine.
Moderator: Mike Everman
Re: 85% throttable pulse jet engine.
Do you have the name of the book on some of the copies/pages you made from it? If you go to the library again could you get the title? Was it a book something like JANE'S ALL THE WORLD'S AIRCRAFT or GUIDED MISSILES TODAY? ha
I've read somewhere that faster than the speed of sound pulsejets have been done, but only theoretically in those higher supersonic speeds such as the 1200 mph you mentioned. Also there was some mention of some pulsejet that could transition to ramjet mode. In fact, Foa said that at higher subsonic speeds, because the valves don't close all the way, the valved pulsejet becomes in effect a poorly running ramjet. Another tidbit according to Foa is that the line of demarcation between a subsonic ramjet and valveless pulsejet is blurred, that a subsonic ramjet benefits from pulsating combustion/mixing in the duct. I have a picture of a big ramjet,(not one of those helicopter tip kinds), that was designed for subsonic speed. It was in Jane's although it would seem a waste to go so slow for a ramjet.
It would be nice to see some supersonic pulsejet designs or find more information about them.
"I read all the information about the engine and made some photo copies of parts of it. That is where I got the information about the actually speed and how it was done."
Could you elaborate?
Thanks,
Mark
I've read somewhere that faster than the speed of sound pulsejets have been done, but only theoretically in those higher supersonic speeds such as the 1200 mph you mentioned. Also there was some mention of some pulsejet that could transition to ramjet mode. In fact, Foa said that at higher subsonic speeds, because the valves don't close all the way, the valved pulsejet becomes in effect a poorly running ramjet. Another tidbit according to Foa is that the line of demarcation between a subsonic ramjet and valveless pulsejet is blurred, that a subsonic ramjet benefits from pulsating combustion/mixing in the duct. I have a picture of a big ramjet,(not one of those helicopter tip kinds), that was designed for subsonic speed. It was in Jane's although it would seem a waste to go so slow for a ramjet.
It would be nice to see some supersonic pulsejet designs or find more information about them.
"I read all the information about the engine and made some photo copies of parts of it. That is where I got the information about the actually speed and how it was done."
Could you elaborate?
Thanks,
Mark
Presentation is Everything
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Re: 85% throttable pulse jet engine.
It is an old book printed in the early 1950s. It is a rather large book about 18" square, about 2" thick. The pages fold out to full size blue print drawings. It has been a few years since I have been to the library. I can not recall the exact name of the book.
Re: 85% throttable pulse jet engine.
Be nice to know the name/location of the library. Information like this can be a rare treat.
Thanks, Joe
Thanks, Joe
Re: 85% throttable pulse jet engine.
A car has a 4-cycle engine. Intake/Compression/Power/ExhaustRocket Man wrote:After 6 months of research I have determined the old style pulse jet engines are like running your car engine running wide open at 6000 RPMs.
To complete all 4 cycles, However, the crankshaft has to turn 2 times
3000 times per minute, all 4 cycles have been completed...
which is 50 times per second
To be more specific, if all 4 cycles were referred to as a single "process", this process would happen 50 times per second , in any given cylinder.
Described by Bruno Ogorolec, the pulse jet completes a "process", at a rate of over 250 times per second... which is 5 times more than the 50 times per second, of a car's engine at 6,000rpm.
So, to correctly compare a car's engine to a pulse jet - it would have to be running at 15,000 rpm?
EDIT: Watched your videos- nice engine!
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Re: 85% throttable pulse jet engine.
HPSCL wrote:A car has a 4-cycle engine. Intake/Compression/Power/ExhaustRocket Man wrote:After 6 months of research I have determined the old style pulse jet engines are like running your car engine running wide open at 6000 RPMs.
To complete all 4 cycles, However, the crankshaft has to turn 2 times
3000 times per minute, all 4 cycles have been completed...
which is 50 times per second
To be more specific, if all 4 cycles were referred to as a single "process", this process would happen 50 times per second , in any given cylinder.
Described by Bruno Ogorolec, the pulse jet completes a "process", at a rate of over 250 times per second... which is 5 times more than the 50 times per second, of a car's engine at 6,000rpm.
So, to correctly compare a car's engine to a pulse jet - it would have to be running at 15,000 rpm?
EDIT: Watched your videos- nice engine!
You missed the whole point of what I was trying to explain. Remove the carburetor from your car engine and throw it in the gargage can. Now stick a hose or pipe in the car intake and turn on the fuel and let the engine run wide open with no throttle control at all. That is how people try to run their pulse jet engine. It is just plain stupid. I am glad car engine manufactures are not still living in the stone age.
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Re: 85% throttable pulse jet engine.
Okay, I'll bite.
Your first post says, and I quote...
On elaborating a little further, we got to (with my emphasis added)...
So, what I can buy is that, by restricting the effective intake area, you can restrict the amount of air pulled in each cycle, and possibly extend the low end of the throttle range. For the rest, I don't see any significant difference at all. On the other hand, I may be being dim, in which case please feel free to enlighten me.
Your first post says, and I quote...
So far so good, right?Rocket Man wrote:... I have determined the old style pulse jet engines are like running your car engine running wide open ... it is like removing the round throttle disc from inside the car engine carburetor so the engine gets full air all the time and you attempt to throttle the engine by adjusting fuel flow only.
On elaborating a little further, we got to (with my emphasis added)...
Now, a "normal" pulsejet, throttled by merely adjusting fuel flow, will run lean at low throttle, and rich at high throttle as well. It will pull in the amount of air required to run over a large part of its throttle range. Eventually, it will reach a point at which it is too rich, as it can't pull in enough air fast enough, and won't run any further. "Push" more air through the intake, however, and it will go a bit further. Is any of this sounding familiar?Rocket Man wrote:Yes that is correct. The natural kenetic energy of the engine makes it suck in the amount of air it needs for the amount of fuel it has to burn through about 60% of its throttle range. The engine runs lean at low throttle and rich at high throttle.tufty wrote:So all you're doing is adjusting fuel flow, then?
So, what I can buy is that, by restricting the effective intake area, you can restrict the amount of air pulled in each cycle, and possibly extend the low end of the throttle range. For the rest, I don't see any significant difference at all. On the other hand, I may be being dim, in which case please feel free to enlighten me.
Re: 85% throttable pulse jet engine.
"That is how people try to run their pulse jet engine. It is just plain stupid."
These are NOT car engines. Frequency only shifts a slight amount between high throttle and low throttle. It is the amplitude that changes.
The geometry of the engine (and of course the last pulse) will determine how low&long the pressure swing will be for the intake cycle.
So here is a question to ponder:
Why is it not possible to have a correct fuel air mixture for either a high amplitude pulse or low amplitude pulse within the same engine by only varying the fuel rate?
These are NOT car engines. Frequency only shifts a slight amount between high throttle and low throttle. It is the amplitude that changes.
The geometry of the engine (and of course the last pulse) will determine how low&long the pressure swing will be for the intake cycle.
So here is a question to ponder:
Why is it not possible to have a correct fuel air mixture for either a high amplitude pulse or low amplitude pulse within the same engine by only varying the fuel rate?
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Re: 85% throttable pulse jet engine.
Pulsejets are more like diesel engines than gasoline ones.
Within limits (imposed by various factors such as total intake area, valving losses, pumping capacity, etc), they automatically respond to changes in fuel flow by drawing more (or less) air so as to maintain the stoichiometric ratio required for combustion.
If you inject more fuel, the energy of the combustion cycle is increased and therefore there is more pumping action created by the greater/faster massflow out of the tailpipe.
If you inject less fuel then the energy of the combustion cycle is decreased so less air is drawn in because the tailpipe flow has less mass and/or less velocity.
Of course the lower-limit is determined by the level at which the pumping action of the gas-flow in the tailpipe is insufficient to draw in enough air for the next combustion pulse.
The upper limit is determined by the inability of the engine to draw in sufficient fresh air to maintain a stoichiometric ratio with the amount of fuel that's been injected.
It's not rocket science.
The reason that valveless engines throttle over a much wider range than valved engines is mainly because the valved engine has higher losses in its valving system (the need to overcome the valve-tension etc) whereas the only thing a valveless engine needs to do is overcome the inertia of the gas-column in the intake tube.
Ram-effect can also adversely affect the throttling ability of a conventional valved engine because the static-head produced by the ram-effect means that too much air flows for the amount of fuel being injected so the fuel/air ratio falls below the lower limits of the stoich ratio and the fire goes out. It's interesting that some engines like the Zanin appear to have been designed to eliminate the ram-effect which should (in effect) give them better throttling but, because they're still aspirated), the claimed throttling these engines offer really doesn't work at all well.
Within limits (imposed by various factors such as total intake area, valving losses, pumping capacity, etc), they automatically respond to changes in fuel flow by drawing more (or less) air so as to maintain the stoichiometric ratio required for combustion.
If you inject more fuel, the energy of the combustion cycle is increased and therefore there is more pumping action created by the greater/faster massflow out of the tailpipe.
If you inject less fuel then the energy of the combustion cycle is decreased so less air is drawn in because the tailpipe flow has less mass and/or less velocity.
Of course the lower-limit is determined by the level at which the pumping action of the gas-flow in the tailpipe is insufficient to draw in enough air for the next combustion pulse.
The upper limit is determined by the inability of the engine to draw in sufficient fresh air to maintain a stoichiometric ratio with the amount of fuel that's been injected.
It's not rocket science.
The reason that valveless engines throttle over a much wider range than valved engines is mainly because the valved engine has higher losses in its valving system (the need to overcome the valve-tension etc) whereas the only thing a valveless engine needs to do is overcome the inertia of the gas-column in the intake tube.
Ram-effect can also adversely affect the throttling ability of a conventional valved engine because the static-head produced by the ram-effect means that too much air flows for the amount of fuel being injected so the fuel/air ratio falls below the lower limits of the stoich ratio and the fire goes out. It's interesting that some engines like the Zanin appear to have been designed to eliminate the ram-effect which should (in effect) give them better throttling but, because they're still aspirated), the claimed throttling these engines offer really doesn't work at all well.
Re: 85% throttable pulse jet engine.
Rocket Man,
When running your engines, do you pressurize your liquid kerosene and gasoline for injection, or use the veturi effect?
Also in your work do you find it better at 40% or 50% intake to exhaust ratio with the liquids?
Thanks, Joe
When running your engines, do you pressurize your liquid kerosene and gasoline for injection, or use the veturi effect?
Also in your work do you find it better at 40% or 50% intake to exhaust ratio with the liquids?
Thanks, Joe
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Re: 85% throttable pulse jet engine.
I have been experementing with 3 fuel systems just like the Germans did. I can start the engine on propane at 20% throttle. The second fuel system takes over automatically after the engine starts. The engine will suck the fuel in itself on the test stand but if in flight a pressureized fuel systems works best. The 3rd fuel system gives the engine more fuel as ram air increases.PyroJoe wrote:Rocket Man,
When running your engines, do you pressurize your liquid kerosene and gasoline for injection, or use the veturi effect?
Also in your work do you find it better at 40% or 50% intake to exhaust ratio with the liquids?
Thanks, Joe
40% or 50% intake to exhaust ratio both work. 40% allows the engine to start easier and run at a lower idle throttle of about 10 to 12% but the engine will not throttle up all the way. 50% lets the engine start at 20% idle throttle on the test stand and throttle up to 100% throttle.
100% throttle is relative it don't mean anything it basically means more thrust at 50% than 40%. With ram air and the 3rd fuel system makes the engine produces about 150% thrust.
If you read the German V1 data you will notice they made several discoveries totally by accident. At first the V1 speed was 400 mph. After some experementing the speed went up to 440 mph. Then another improvement the speed was up to 460 mph. The last improvement the speed was up to about 500 mph and the war was over.
After WWII the USA got the German V1 engine to do 900 mph in one test then 1200 mph in another test. The research data says exactly what they did to accomplish this.
I have several college research papers from several engineering students all from different universities. They all made some interesting discoveries. One discover has to do with the design and shape of the engine body this allows automatic pretection of the reed valves. Also liquid fuel rocket engine fuel burn rate date is very useful in the correct design of the engine.
A correctly designed engine can run for several hours on the test stand at 100% throttle and the reed valves show no signs of ever getting hot.
One more interesting note about pulse jet engines, they have no problem running lean but they do not like to run rich. Air intake is automatic with each measure of fuel. Once you throttle the engine up to 100% on the test stand the engine can not suck in any more air to produce more thrust so it is totally dependent on ram air to produce more thrust, unless................
Re: 85% throttable pulse jet engine.
Unless? (backfill with some percentage of oxidizers maybe?)
I am working with something in its rough stages that is showing similar result to the 40% & 50% above.
1200 mph is really moving, I wonder if that engine is still pulsing at those speeds or has switched to continuous combustion at that speed?
Many thanks, Joe
I am working with something in its rough stages that is showing similar result to the 40% & 50% above.
1200 mph is really moving, I wonder if that engine is still pulsing at those speeds or has switched to continuous combustion at that speed?
Many thanks, Joe
Re: 85% throttable pulse jet engine.
hi
i have a pulsejet but i cant starting it
when i spraying the air the fuel is come back in fuel tube
and don't starting
where is the problem
i use all kind of the fuel (kerosene,gasoline,propane,methanol.....)
what must i do?
good regards
i have a pulsejet but i cant starting it
when i spraying the air the fuel is come back in fuel tube
and don't starting
where is the problem
i use all kind of the fuel (kerosene,gasoline,propane,methanol.....)
what must i do?
good regards