Practicality of pulsejet made from turbo

  • Thread starter imperium2600
  • Start date
In summary: Without a compressor, the jet would suck in air at a very high rate, and not be able to produce enough thrust to get off the ground.The V-1 used an air drop or RATO to get going I think that you're confusing a pulse jet with a ram jet, ray. It doesn't need a running start because the combustion chamber is closed at the time of pressurization. The V-1's were launched from ramps resembling ski-jumps, and usually (AFAIK) started with a compressed air blast the same as some turbojets.Pulse jet and turbo don't belong in the same contraption, and quite possibly, not in the same sentence
  • #1
imperium2600
18
0
im finding a lot of relatively simple plans for jet and pulsejet engines using a turbocharger. what I am wondering is how practical would one (or multiple jets) be in a small aircraft.

the aircraft I am building is a model jet I am converting into a homebuilt uav. its about 14 feet long and weighs only a few hundred pounds. what i would like to know is if one of these engines is practical and what would i have to do to get enough power for the jet.
 
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  • #2
You're going to need a lot of thrust to get that thing flying, and I don't think a home-made turbo/pulse jet would fit the bill. I would look into a 4-stroke engine and prop.
 
  • #3
I agree with Mech. While it's certainly possible to build your own pulse-jet, it wouldn't likely be practical for your purposes. If you want the appearance of a jet, without the hassle, go with a ducted fan powered by the aforementioned 4-stroke. With the scale that you're looking at, it would be more efficient (and a lot quieter) than a 2-stroke.
If you insist upon using a jet, check out jetzilla.com to see what's what.
 
  • #4
Pulse jets are finicky beasts. They're also loud as all get out. Granted, they are relatively simple, but I don't think they are practical for what you want to do. A few hundred pounds is an order of magnitude greater than you would most likely be able to produce in terms of thrust.
 
  • #5
Agree with Fred, the home made ones are crude, incredibly noisy (seriously) and the specific thrust is pretty crap compared with something proper.
 
  • #6
Noisy... yeah, in about the same context as the 'noisy cricket' gun that Will Smith used in 'Men In Black'. :biggrin:
Think of lying around with your head in a 200hp wood-chipper.
 
  • #7
thanks for the help, every site i found on pulsejets never applied them to an actual vehicle. people just had them bolted into a metal frame for their own personal pyrotechnic pleasures.
 
  • #8
I've seen pulsejets propelling things like shopping trolleys and go-karts, (and even some scary contraption which got a very brave man up to 70mph on a runway) but I really doubt the practicality of trying to get airborne with one.
 
  • #9
Pulse jet and turbo don't belong in the same contraption, and quite possibly, not in the same sentence.

The V-2 did fly with a pulse-jet engine, and had a ~500 lb payload or something like that. Pulse jets are also popular for model airplanes.
 
  • #10
I had a buddy with a fairly large pulse jet - I would say about a foot in diameter and six feet long - and we took it up to the Oregon Museum of Science and Industry for a demo. The museum received complaints about the noise from people living on the other side of the Columbia River! And yes, for all the noise and fury, the thrust was a joke. This was a resonance type with no moving parts.
 
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  • #11
NateTG said:
Pulse jet and turbo don't belong in the same contraption, and quite possibly, not in the same sentence.

The V-2 did fly with a pulse-jet engine, and had a ~500 lb payload or something like that. Pulse jets are also popular for model airplanes.

V-1 was a Pulse jet buzz bomb, V-2 was rocket named the A-4

I agree a pulse is not a turbo, as a turbo spins and a pulse uses a flap
also a pulse need a running start as the flow at rest is = to zero

V-1 used an air drop or RATO to get going
 
  • #12
I think that you're confusing a pulse jet with a ram jet, ray. It doesn't need a running start because the combustion chamber is closed at the time of pressurization. The V-1's were launched from ramps resembling ski-jumps, and usually (AFAIK) started with a compressed air blast the same as some turbojets.
An interesting side-note is that the pulse jets (at least the V-1 versions) actually drew something like 85-90% of the new intake charge in through the tailpipe rather than the valve box.
 
  • #13
as I understand the pulse jet is a kind of ram
as there is no compresser to suck in air
and unless they force air in [by moving] there is no power
so ''As the pulsejet requires a high volume of incoming air for full thrust, the V-1 was launched from a ramp through the use of a chemical/steam catapult.''

Operating speed: 375-400 mph
Launching speed: 220 mph
Range: 150 miles
Operating altitude: 2,000 to 4,000 ft.

now how they get air to flow in a tail pipe againts the open front vanes
inflow at 390mph I do not understand some maybe but > 80%?
 
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  • #14
I acknowledge that catapults were used, but for much the same reason that they are on an aircraft carrier. The V-1 simply couldn't build up enough speed in that distance to become airborne under its own power. The engine was already running at launch. As I said, most of the new intake came through the tailpipe, so forward speed wouldn't have too much to do with the power generation.
 
  • #15
ray b said:
now how they get air to flow in a tail pipe againts the open front vanes
inflow at 390mph I do not understand some maybe but > 80%?

It doesn't burn like a normal jet or rocket; it's actually a very rapid series of individual explosions, more like a car engine. As with any explosion, a vacuum is created inside the blast area as a result of the initial overpressure. The tailpipe has less resistance to airflow than the valve box does, so that's where it gets sucked in the most.
 
  • #16
[edit...looked into it] According to Wik:
The inertia of the traveling exhaust gas causes a low pressure in the combustion chamber. This pressure is less than the inlet pressure (upstream of the one-way valve), and so the induction phase of the cycle begins.
http://en.wikipedia.org/wiki/Pulse_jet_engine

I'm sure that's true, but I suspect that the pressure difference isn't enough to do much more than keep the engine running at low speed. I doubt most can produce much usable thust without a running start.

Fred would be the expert, though...
 
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  • #17
We haven't studied pulse jets in my day. However, I have worked with some "old timers" that had played with them in the test cells. The ones that were run did use a compressor to provide the start conditions for the static tests. I can't say yeah or nay about the 80-90% flow through the tail pipe that Danger has mentioned. That seems like an awful lot of mass flow to be going against the inlet flow.

I have seen video of the German launches of the V1 and come to think of it, I have not seen how they initiated a start. I have always just seen them launch from ramps on the coast. I have read that a lot of them were launched from He-111's.

If anyone is interested, here's a pretty cut and dry theory for pulse jets: http://www.pulse-jets.com/count/pulse.php?ID=32
 
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  • #18
while I see a danger is doughting Danger
none of the on-line links say anything about high rear fill rates
in fact the burn is not sparked after starting but steady depending on pulse/fuel ratio
and it is hard to see how that works with a high % backflow
in fact why use a front scoop and valves if 85% is coming in the back

computer control of both air valve and fuel injection may get modern version to work better as would a form of stratifed or swirl
fuel/air mix and timing

other notes, the USA copys used the RATO launch not the germans
but has any type of pulse jet been flown without a kick of some kind to start the event?
 
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Related to Practicality of pulsejet made from turbo

What is a pulsejet made from turbo?

A pulsejet made from turbo is a type of pulsejet engine that utilizes a turbocharger to compress air before it enters the combustion chamber. This allows for more efficient combustion and increased thrust.

How practical is a pulsejet made from turbo?

The practicality of a pulsejet made from turbo depends on its intended use. It may be more practical for certain applications, such as powering small unmanned aerial vehicles, due to its simplicity and low cost. However, it may not be as practical for larger aircraft due to its inefficiency and noise.

What are the advantages of a pulsejet made from turbo?

Some advantages of a pulsejet made from turbo include its simplicity, low cost, and ability to operate on a variety of fuels. It also has a high thrust-to-weight ratio, making it suitable for small and lightweight applications.

What are the disadvantages of a pulsejet made from turbo?

One major disadvantage of a pulsejet made from turbo is its high fuel consumption, which can make it inefficient for larger applications. It also produces a loud and distinctive noise, which can be a nuisance in urban areas. Additionally, it may require frequent maintenance due to the high temperatures and stresses involved in its operation.

Are there any safety concerns with a pulsejet made from turbo?

As with any engine, there are potential safety concerns with a pulsejet made from turbo. The high temperatures and pressures involved in its operation can pose a risk of fire or explosion. Additionally, the loud noise it produces may be harmful to hearing if proper precautions are not taken.

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