I'm currently in my first year at university studying mechanical engineering.Few lads at work are in their final year and are doing their dissertation.Its early days for me but id like to have a decent idea of what I am aiming to do . The idea is to design a pulse jet , fabricate it weld it and then test it. Just wondering if anyone on here has had much involvement with pulse jets and knows anything about the maths behind them. I've downloaded endless amounts of plans , etc but cant find anything in regards to how to design them. Any one help me out ?
- Thread starter ross1993
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the snooper
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Gareth J
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I built one with a mate at uni. Actually he did most of it really.
It was a great conversation starter with all the old fluids proffs (the noise in the carpark always drew a few academics out into the sunshine) and they generally loved fathoming in their minds what was going on.
It's a simple design but the fluid flows inside are far, far from simple. Describing in words whats going on is pretty simple (lots of descriptions online I imagine) but to mathematically get handle on whats happening is going to be nearly impossible. You've got rapidly expanding gasses, chemical reactions, pulses many times per second, flame fronts....
Regarding how to design them, there may be a set of plans with suitable scaling factor that can be used to make different sized ones based on calcs someone's put together I'm not sure but I'll bet trial and error played a lot in the design of any of them.
Using CFD to model one would be a fantastically involved dissertation and I think done well, including chemical reaction modelling would be potentially be masters level (or higher?) stuff.
Whatever you do, get out and build one pronto, they're super simple and you'll soon find a whole load of curious folk when you fire it up.
It was a great conversation starter with all the old fluids proffs (the noise in the carpark always drew a few academics out into the sunshine) and they generally loved fathoming in their minds what was going on.
It's a simple design but the fluid flows inside are far, far from simple. Describing in words whats going on is pretty simple (lots of descriptions online I imagine) but to mathematically get handle on whats happening is going to be nearly impossible. You've got rapidly expanding gasses, chemical reactions, pulses many times per second, flame fronts....
Regarding how to design them, there may be a set of plans with suitable scaling factor that can be used to make different sized ones based on calcs someone's put together I'm not sure but I'll bet trial and error played a lot in the design of any of them.
Using CFD to model one would be a fantastically involved dissertation and I think done well, including chemical reaction modelling would be potentially be masters level (or higher?) stuff.
Whatever you do, get out and build one pronto, they're super simple and you'll soon find a whole load of curious folk when you fire it up.
brightspark
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here 
ive been trying to think of what will be involved maths wise , at first doesnt seem to hard ; fuel , calorific values , flow rates force thrust etc but now ive started to look into it a bit more it seems to be getting a lot more involved. The pulse is causing the biggest issue. Ill speak to my lecturer and see what he has to say. We have ansys fluent at work so CFD shouldnt be to hard to do.
doubleboost
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I have done a bit with Gas Turbines
Gareth J
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You may be able to model one part with CFD, say testing a single hypothetical pulse, OK. But to get a model that fully approximates a running pulsejet will be bonkers and I imagine require some serious computing power. Yea, speak to those that are interested, fluids/thermofluids/CFD guy&gals.
Seriously though, try to make time to get in the workshop and make a prototype. I know it'll be busy in your first year but if you can, it'll help mark you out as someone who gets stuff done and hopefully ingratiate you with the stores/workshop folk who'll be a big help to have onside. Plus, past your first year you may not get a huge amount of fabrication/building stuff to do.
GKQ
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Try this web site http://pulse-jets.com loads of designs some simple so not so.
Made one at school many years ago it worked pretty well. On the dangerous side but good fun.
Also http://aardvark.co.nz/pjet/makingpulsejets.shtml
Graham
Made one at school many years ago it worked pretty well. On the dangerous side but good fun.
Also http://aardvark.co.nz/pjet/makingpulsejets.shtml
Graham
dobbslc
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QUB, Queens University Belfast know a lot about two stroke engine design and fabrication, there might be some crossover with the gas pulse work as the expansion chambers on their race bikes use this.
They were very successful with Jeremy McWilliaims on the old 250'S.
They were very successful with Jeremy McWilliaims on the old 250'S.
