Bruno Ogorelec wrote:
Bruno Ogorelec wrote:with different implications for the Short Lady.
Oops. I just noticed I've been referring to the Short Lady, which is a different design entirely, rather than the Focused Wave Engine. Sorry. My tired brain is not concentrating as well as it once was....
No, Bruno - shake your head till it clears. Focused Wave Engine is just the technical name for the Short Lady, which was the 'mystery' name that I threw out there before revealing what she really looked like.
More importantly, Larry, have you rethought the intake stack behavior?
When I suggested bent rather than 'broken' intake, you said you expected the stack to be useful mostly as a resonator and that exhaust flow would probably not be of importance.
Now that it is demonstrably not just a wave vessel, but also pushes out quite some gas flow, would you be motivated to redesign it? If so, what would you do?
I don't know. The present design doesn't seem to be suffering much from the crude 'elbow'. However, since blast mass is obviously moving there, a straighter path would theoretically be better. Do we care how much thrust is from the tail and how much is from the intake? I hardly think so. So, you could have just a slightly curved pipe that stops abruptly at just the right station inside the cone, with the cutoff facing forward, a la Thermojet. That also might be better in terms of less disruption of the flow of gas along the upper cone wall toward the tailpipe.
Also, you mentioned a very small flare at the tailpipe end. The very similar NRL engine has a larger but still very small flare. Do you think there is something about those engines that makes a small flare better than a large one? Mind you, the NRL was meant only to generate a great amount of hot air, not thrust.
The only reason I wanted the small flare was because of the weirdness of the curve UFLOW renders when it's included. It would be really odd to find out that there really is a physical singularity because of that tiny detail being just so! I doubt that's really the case, and see no reason why a big flare wouldn't be advantageous, in terms of a little more cold mass in the pipe.
You obviously like straight pipes. I don't think i remember a Cottrill engine with a bustle tailpipe. Is it just an affectation or some theory about pipe shape?
You might as well call it an affectation, since I do like the way that looks, but there's a practical aspect, too: Many scale jet models will need a pretty tight tail end to be truly scale, and you still have to have plenty of cross-section back there to get the cooling air flow moved out. It's a shame to ruin the sideview profile of a nice airplane by broadening the tail end. Some planes, like my unfinished F-104 Starfighter design, have plenty of rear-end cross-section, of course. And, there's another practical reason: ease and cost of construction. Most engine designs are, in my view, almost absurdly complicated. Look how much discussion recently went into describing precisely how to build the intake skirt properly for the Chinese! I want something that goes from the drawing board to the test stand simply and cheaply. In this case, I was willing to draw up a design with a front end that I'm not tooled up to build, and now I'm glad I did. But, darn it, I don't want it much more complicated than that, if it turns out to already work well. I want a machine that's easy for you if you want to build it, and cheap if you want me to build it and sell it to you. Not sophisticated, but the kid flipping burgers for a living will thank me for it, by gladly buying it off the shelf instead of the pretty Zannin sitting next to it.