For someone that just burned through a $4000 radiative chamber, I am a happy camper.
We tested our fourth generation kerosene injector tonight. There will be pictures in this weekend's update, but basically it has an even tighter venturi, down to 0.6" (with a 0.5" throat), and instead of the fuel coming in as a high velocity jet from the side of the venturi, a stainless pipe comes in from the outside on the catalyst pack side of the venturi, and it has a pretty sizable hole in the bottom, before a plugged end. The idea is to have very low velocity fuel stream straight down the middle of the very high velocity (nearly sonic) peroxide decomposition, much like an SSME lox post injector in reverse. We put the radiative chamber together with the high temperature bolts, the stainless clamp ring, and the silica gasket material (not the gas-filled O-rings, which have yet to arrive). We also wet sanded the silicide coated flange, and used a torque wrench to evenly tighten the flange to 6 ft-lb on each of the #10 socket head cap screws. All of the runs sealed absolutely perfectly. We started off very rich (but not as rich as we were running the regen engine), and immediately on lighting, it was obvious things were working a lot better, because the engine started glowing much more rapidly, and much higher up. There was still a visible bias opposite the fuel inlet, probably because the flow had enough momentum that it was not "turned" completely axially when it came out of the drilled hole. Our oxidizer-only Isp was 246, up from a previous best of 192! We shrank the fuel jet a good chunk, and the oxidizer-Isp increased a bit more. We shrank it some more, and it finally nosed over a bit, which would still be at increasing "true Isp". We will have to get our sight glass hooked back up so we can measure the kerosene flow, but this was with an 0.040" kerosene jet, while a 0.060" jet resulted in a measured O:F of 2.2:1 on Saturday, so that would put us around 5:1 O:F, which would be a true Isp of 208! We will have to check the load cell calibration and more precisely measure the kerosene flow, but it was clearly a huge improvement. Thrust was 45 lbf +/- 5% at 250 psi feed pressure. We have great video of all these tests, including it throwing molten glass beads off of our cinder block blast deflector. The entire chamber is glowing like a star, flaring so you can't see the outline in the video. We loaded up four liters of peroxide and let it run. The burn was nice and monotonous, but after 45 seconds of hot fire, the plume started deflecting slightly, and some sparks started coming off the nozzle. I killed the kerosene, and let the rest run out as monoprop. We burned the silicide coating off at the nozzle, which allowed the TZM to vaporize a hole. The entire side opposite the fuel fitting has a different look to the coating, so I am going to send it back to Hitemco to have them tell us some things about it, and have the second chamber coated. We are going to resolve the bias towards one side, possibly improve our film cooling, and stay a bit richer. We may be near the theoretical max Isp (220 at a leaner mixture), but we wanted to get rid of the uneven combustion, so we modified the fuel injector tube to actually take a 90 degree turn (cut, bend, weld), instead of having a hole drilled in the side. This will give straighter, and even lower velocity fuel injection. We won't be able to "see" the difference until we get the second chamber coated, but we are going to test it with the regen engine (at a much richer jetting) this weekend. I have a good ring of film "cooling" steam holes in the injector, but I may make a ring on the bottom to turn them into a sheet instead of multiple jets. We may have problems with regen cooling, because the greatly increased efficiency will have increased the chamber temperature and decreased the peroxide flow. We are laying out the work for a 1000lbf regen biprop now. John Carmack _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
