After a few weeks of post-graduation work on our afterburner the damn thing finally lit off!
We started testing last week, but were having trouble getting ignition. We tried varying a few parameters, like increasing our fuel rate and changing our spray patterns. However the big breakthrough came when we tried turning down our core engine. At it’s maximum thrust setting the core JetCat engine would run at 125,000 RPM, which is really really fast (full size engines run less than half that). So when we turned down the engine, the speed of the flow in the afterburner was slowed down enough that our re-circulation zone was able to actually hold a flame.
The first test we only ran for about 3 seconds, and after a lot of cheering and some re-setting we set up for another full blown run. Here’s a video of our engine in action, this is about 5 minutes into the test which gave the huge thermal mass of the afterburner some time to get up to temperature:
We started at 50,000 RPM and were trying to see at what point we’d get a blow out at our f/a ratio (which also affects blow out velocity).
Unfortunately about when we reached 70,000 rpm’s we started burning the fuel trough that is attached to the end of the test stand above. When we tried taking out the fuel trough, which was slightly blocking the flow the afterburner wouldn’t light. As it turns out the trough was back pressuring the combustion chamber (increasing the pressure in the area where the flame is started and held) enough to give us a stable combustion.
Oh yeah and we raced today in Burlington Iowa. If you’ve never done the road race, everyone pretty much treats it like a big 80 mile group ride so they’re fresh for Snake Alley tomorrow. However three people apparently didn’t get the memo and stayed away ‘spoiling the day for the sprinters’. I left my own sprint waaaaaay to late and ended up 3rd or 4rd in the field sprint, oh well live and learn, tomorrow’s another day (taming the snake), and other generic make you feel good expression.