Pulsejets are a popular DIY build for the keen experimenter, much loved for their mechanical simplicity and powerful roar. However, it can be difficult to get them running smoothly and producing high amounts of thrust. In an ongoing quest to do just that, [Integza] has been iterating hard on his designs, recently adding an electric turbocharger to add some boost.
Like any combustion engine, adding more air means that more fuel can be burned for more power. The electric turbocharger is a perfect way to do this, using a powerful brushless motor to turn a radial compressor wheel to force high-pressure air into the pulse jet’s combustion chamber. [Integza] used a resin printer to produce the turbocharger compressor wheel and housing, which made producing the complex geometry a cinch.
Initial results were positive, with the pulsejet maintaining better combustion with the turbocharger activated. It does come with the drawback of requiring battery power to run, but it may be worth the tradeoff for added thrust. However, the fragile setup requires more refinement before a thrust test can be carried out. Up until now, [Integza] has made do with a set of bathroom scales; we imagine a spring force gauge or strain gauge might be in order. If you’re keen to build your own pulsejet without welding, consider the carbon fiber method used in this project. Video after the break.
Pretty sweet.
Maybe get an automotive turbocharger, design things so some of the pulse jet exhaust spins the hot side (exhaust) turbine, and the intake turbine blows into the chamber? You may need a motor to spin it up initially, but it seems like it could work.
You mean build a jet engine?
It would be like a badly running jet engine, if it keeps the pulsed operation. I wonder if there’s any advantage over continuous combustion, like having greater efficiency or thrust at some range of air speeds.
Yeah it’s not a turbo, it’s a supercharger. And if you use a supercharger is it still a pulsejet?
Yes it’s similar to a vortech blower (that he was using).
But this project would lend itself to a turbo instead, just bleed off some of the exhaust.
If you also geared the drive to a propeller, it would be a motorjet. Not sure the absence of propeller disqualifies it really, so an electric motorjet?
Or gear the shaft to a generator, and make a turbo-generator?
The jet is not driving any shafts at this point, only the electric motor, so that would be fairly pointless.
That’s actually a very common project. https://www.youtube.com/watch?v=JzwfzgfJiJ4
There are so many easier ways to set your workshop alight. I salute this level of effort!
He has succeeded in doing so at least once already.
So the turbine is wasting energy fighting half the pulse, and that is an improvement?
Nope it is only used as a startermotor for the pulsejet. So the unit can be contained and self starting
Would I be correct in saying this is not a turbocharger, but a supercharger?
Yes! A supercharger is the correct term for any device that compresses the intake air. Turbochargers (aka turbosuperchargers) refers specifically to the turbine-driven variety.
That’s not a turbocharger. The “turbo” part of that word means that the compressor is driven by a turbine, which is a device that extracts work from a flowing fluid and imparts it to a rotating shaft. With the compressor powered by the exhaust flow, a turbocharger doesn’t even need the valve arrangement of a pulsejet — plenty of people have turned them into jet engines just by adding a combustion chamber and some plumbing. But making a turbine survive life in combustion exhaust is no mean feat, and 3D printing one is still an awfully expensive proposition.
Right, it’s technically a supercharger, even though most people would think that means a belt driven positive displacement supercharger, which is the default type nowadays, or something to plug a Tesla into.
Was about to say exactly that. Essentially if you have a working turbocharger on a jet then you have built a traditional jet engine.
That remembers me of the hybrid turbocharger, Mercedes used (or uses ?) in his Formula one engines: A “normal” turbocharger with a strong brushless motor/generator on the shaft to extract power from the turbine, if it is in excess or spins the turbo up electrically to give extra boost.
Seems like a complicated way to make a rechargeable leaf-blower. Wouldn’t the local big box store be a better choice?
Sure, but what fun is that when you can 3d print a turbo charger, at least the compressor portion :)
Pulse jets fire in pulses hence their name, should there be two chambers firing in a delayed manner so the exhaust doesn’t pulse? A stretch?
How about, you stick 3 on a spindle, with the nozzles slightly offset to spin the whole thing, and have a valve plate with one hole in it, that the blower blows through, and maybe gear the spindle to the blower so when it hits a few thousand RPM you can shut the ‘lectric off…
https://www.youtube.com/watch?v=rG_Eh0J_4_s
Doesn’t seem to be true to the spirit of a pulse jet, maybe try injecting LOX with the fuel, that’ll spice things up!
I make no pretense at expertise, but wouldn’t that make it a rocket?
I’m not sure either, I was just wondering how to increase the oxygen to increase the jet combustion. I don’t think so as long as you only use the LOX to increase the oxygen, not totally replace it.
I suspect that, at least for the first iteration, that would make it shrapnel…
Tons of sellers on ebay have cheap (<$150) turbo chargers. Some models appear to even have the electric motor needed to drive the fan. Could be a great alternative to a 3d printed design.
[Integza] likes to build things (and smash tomatoes), not buy things… and it’s faster to 3d print a new component that obviously melted away than to ship a replacement part.
why not put the intake duct on the front of the pulse jet? as it moves through the air, you should get a high pressure flow if the intake geometry is suited to it. I’m always a little perplexed when people measure thrust of these things in a static test fixture since movement is quite critical to most jet designs (at least from my naive 10,000′ view of things)
“It does come with the drawback of requiring battery power to run”
For extra credit, power the supercharger with an MHD generator driven by the jet exhaust.
Pet peve. It’s a 3d printed supercharger. Turbos have a turbine using exhaust flow and pressure to spin the turbine that is connected to the compressor via a shaft. Turbocharging is a form of supercharging.
What would have been cool to see is a 3d printed turbo out of ceramic.
Right, the full name you yell at a turbo when it’s in trouble is “turbosupercharger” like the only time you hear your middle name, with the supercharger bit being the blower and the turbo bit being the exhaust energy recovery turbine.