After some delay, due to pressure of work, I finally got my afterburner set up
and gave it a test run..
Because I'm currently using a relatively low-pressure centrifugal pump to power the afterburner fuel feed, I decided to run a couple of vaporizing coils of copper tube around the tailpipe. This ensures that the kerosene is injected as a vapor and not just a stream of liquid.
Earlier trials without the pre-heat weren't very encouraging and the afterburn flame was very unstable, it's much better now.
In this picture you can see that the afterburner has just fired -- it tends to puff out a huge cloud of white vapor before ignition occurs. It's also worth noting that afterburners are incredibly fuel-hungry. This one consumes a pint and a half of kerosene per minute!
Here is the afterburner running with the engine at about 1/4 throttle -- the flame is quite orange because the volume and velocity of the air coming out the tailpipe is relatively small. In essence, the AB runs very "rich" at this throttle setting -- mind you, I can't see any point in running an afterburner when your at anything less than full throttle.
I found it interesting that hitting the afterburner at all revs obviously increases the back-pressure on the exhaust turbine because the revs decline slightly.
The EGT has remained unchanged since I fitted the AB which was quite a pleasant surprise.
Here's the AB with the engine running at near full throttle (about 30 PSI of boost and around 165K RPMs). You'll note that the flame is much "leaner" and although it looks smaller is actually generating a lot more power because it's heating that air to very high temperatures.
After just a minute running like this the AB tailpipe starts to glow red hot
but I've not had any erosion of the metal yet. The whole thing is made of
stainless and I'll include some close-ups here later.
It makes a timely reminder that you should always have a fire extinguisher handy and that these home-made turbines are not without risk.
Fortunately no damage was done in this case -- I simply turned off the AB pump and blew the excess fuel out with the leaf-blower.
And speaking of safety -- the eagle-eyed amongst you will probably notice that
I'm wearing hearing protection. Believe me, when you run up past 130K RPMs
its still uncomfortable to be as close as I am in these pictures -- even with
undustrial-strength hearing protection.