Mike Everman wrote:Hi Ed!
Well yes they are guesses originally, but you can converge on something like the right conditions for each segment by observing the first pop, and the velocties and temps that follow, to be input as the new starting conditions, and so on.
You're right, though, without knowing the initial pop pressure peak, it's gi-go. Though we should be seeing 160-180 kpa on small motors(?)
A friend of mine used to say (quite cynically): "Measure it with a micrometer, mark it with chalk, cut it with an axe." It seems to me that what you and Eric want me to do with UFLOW is just the opposite path: "Measure it with a piece of twine, mark it with a grease pencil, cut it with a vertical mill." You want the tool to be a kind of performance predictor, based on guesses about an engine we've never observed running! I just don't use UFLOW1D in that way, or feel that it's necessary to do so. Probably, the refined version of NUDIS you're trying to wring out will be a lot more likely for that kind of application.
I think perhaps it's just the difference in philosophy between you engineers and us blacksmiths. All I really want is a relatively quick way to get something that will run the first time you build it. Is that so awful? Remember back about a year ago, when I threw the Short Lady out there, and Steve built it and it ran on the first go? Remember the oohs and aahs? Remember how someone (I think it was you) who said, "I can't get over how short this engine is."? That was done by (a) intuitively designing the pipe and refining it with UFLOW - WITHOUT an intake pipe!!!; and (b) designing an intake geometry based solely on the Hinote Criteria, with end corrections, making a guess for a diameter that might work. All the UFLOW input was educated guesses. The trick is that our guesses have to pass some kind of reasonableness test in our own minds (now, let's see, we know the chamber will be red hot, the tailpipe probably not so hot ...). That's exactly how it was done.
I will be happy to see what you come up with as you work with the new program. Until then, I'll continue to use UFLOW1D as the handy blacksmithing tool that it is. (I hope the engineers one and all can find forgiveness in their hearts for my admittedly crude methods ;-)