Moderator: Mike Everman
steve wrote:Looks good larry, you want me to build it, or are you going to try it first?
If you would like (and if some of our "sort of" resident experts think it will work) I can have it built in a week or so. I am down in the shop at school for at least an hour per day (today I was there for 2.5!) and am running out of things to build.
It looks very promising and I would be thrilled to be able to try out a new design!
larry wrote:Our second concern is that this engine should be extremely good at fully purging the combustion mass, possibly leaving no residuals to ignite the next air/fuel charge!
Mike Everman wrote:Respectfully, I think not. To my eye, you'll still have plenty of free radicals in the CC boundary layer. I think you're over analyzing it.
Bruno Ogorelec wrote:I love it, Larry. I have good reason to believe you are onto a good thing with this. I am not at all surprised that Uflow shows it to be good, too.
But (there's always a 'but' somewhere), why the flat wall one? What conceivable purpose would it serve? It will only be structurally inferior, while performance will certainly not be better.
You say that making such a small cone might be difficult to do. In my opinion (for what itâ€™s worth), this is a typical case in which one should go for a cylinder (large diameter tube) converted to a truncated cone by means of making triangular slice cutouts to one side. Bruce Simpson proposes it on his website and I see no reason to avoid this relatively simple trick.
A relatively easy alternative is making a multi-sided (say, six-sided) truncated pyramid. It can be folded from flat sheet or built up from individual trapeze-shaped sides. No need to mention that mounting the intake tube on a flat side will probably be somewhat easier than doing it on the web of a cone.
In fact, I would make the intake tube square-sectioned, too. Forgo the intrusion of the intake pipe into the chamber and have it begin at the side wall in the same way it does in the Chinese. Another huge step towards easy fabrication. Bends are infinitely easier to do with square sections than with circular and oval ones. Thatâ€™s why SNECMA built their Ecrevisses with square section bends for a long time.
I am absolutely certain that the tube section will have little (if any) influence on performance on this level. Moreover, a square section tube with a circular bend will probably perform better than a round tube with an angular â€˜bendâ€™ like the one featured on both the Chinese and your Short Lady.
Next, donâ€™t forget the â€˜bustleâ€™ tailpipe. It increases the thrust greatly. Look at the Escopette for inspiration. You might wish to start with a cone and end with a circular-section tube. You are better equipped to work out the nodes at which the transitions should be located than I am.
All of the above said, I again encourage you and anyone else to build and develop this design. I am sure it will be a good one. I know of very good results achieved with a similar approach. As encouragement, let me show you a neat MEW jet, model 307, that seems to have been inspired by similar thinking, but should have had the reflector added. If they only thought of Bruceâ€™s â€˜double domeâ€™ valve-shield-cum-fuel-vaporizerâ€¦.
larry wrote:So, Mike, in broad terms, what do you think of this beast?
steve wrote:I rolled up and welded the tailpipe today, tomarrow I will try to finish the CC cone.
larry, dont worry about the cone, It's nothing compared to the one I had to do for the exaust for MK's K-pt01 That stupid thing took me an hour to roll!
Incidentally, the length shown for that tube is supposed to be the acoustic length, which means the real piece should be .6 x ID shorter in total physical length overall
Be sure and get the total finished weight as well, and measure the point that seems to be the CG with the plug in place. (You do want this to end up as a flight engine, don't you? ;-)
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