Off-engine combustion chamber testing

[mitch]

How do the other members of this forum go about testing their combustion chambers? Or do most people just run them on the engine and do the testing that way? I have made some minor modifications to mine, and I am wondering if I shouldn't first do an off-engine benchmark test to make sure everything works fine. In the past I have attached a large shopvac output hose to the chamber and done some low power testing to see how the burn is inside the chamber. I know this is not that accurate compared to using the chamber on the engine, as the chamber has no back pressure on the test stand, and has very limited air flow through it compared to what the turbocharger will push. Any thoughts? Should I just attach it to the turbo and run it as normal? 

[racket]

Hi Mitch

You need to mount a thermometer at the outlet of the combustor to measure your " T I T" , the fuel needs to be regulated so that your measured temperature matches your intended T I T for the running engine.

As your airflow is considerably reduced compared to a running engine , you fuel burn rate will also be reduced accordingly , this may present some "abnormalities" because of fuel atomisation if a spray nozzle is used as the pressure will be lower , so ideally a small fuel nozzle would need to be installed so as to replicate running fuel pressure drops.

Similarly with a propane injector but probably not as important due to the gasious state of the fuel irrespective of supply pressure .

When using evaporators , I really don't know , but would hazard a guess that it would be somewhere in the middle , so you'd probably don't need to worry .

It really is only the spray nozzle pressure drop and atomisation thats an issue .

As long as the exiting temp is the same as your intended running T I T , then you should get a reasonable outcome from your experiments , the usual outcome when guys do atmospheric testing is overfueling leading to overtemping , keep the fuel supply under control and you should be OK .

Cheers
John

[microturbine711]

I performed two combustor bench tests using an EDF (electric ducted fan) with much success. My objective was to verify the functionality of the system but more so the flame behavior with respect symmetry and throttle position. Safety is important here with liquid fuel designs as the vaporizer component is initially cold and any excessive throttle condition will result in raw fuel being injected out of the combustor.

Both YouTube videos of my testing

Start Injector testing (biased flame due to injector location)

youtu.be/RWs5nq_IR1Y

Main Vaporizer injector activation

youtu.be/tG5yT3Q9lKw

~Ty