I've been away for a day sorting things out for my trip to the USA on Monday so I'm very pleased to see so many educated responses.
Maybe I should have given a few more details as that would have prevented the one or two incorrect responses that have been posted.
First EVERYTHING except the shape of the exit is exactly the same on ALL 4 tests, otherwise the test would be meaningless and I've got better things to do than fabricate bullshit stories.
The pressure is the same, the solenoid flow rates (without the pipes) are the same and all pipe lengths are the same (in and out).
The reason the end one has an extra part fitted is because it was easier to machine the desired internal shape than to flair the copper pipe to such extremes. There are no unseen tricks being used and the copper tube butts up cleanly and perfectly to the alloy nozzle, so there is no internal change of diameter causing the different plume shape.
You've all spotted the differences and most of you have made appropriate comments but none of you have yet picked up on what core theory (of mine) the results support.
Dave,
You're right the left does spread wider but not by enough to make it your best choice but I still have some ideas on how to achieve that, without the negative effect that option suffers.
Bob,
Well spotted.
Carnut,
You're right about the liquid core and less phase change but your reason is wrong - very good try though.
Donkeypunch,
Correct observation but wrong reason, the pressures were all the same another good try though.
Daveg360,
Correct observation.
Brian,
Yes the only difference is the shape of the outlet but this has created one or 2 other changes besides the intended one;
1) The pipe length at the constant diameter is unavoidably shorter
2) The end bore is unavoidably larger
However there were 2 aims of the test and these results prove we're on the right track with both;
1) We wanted to see if the outlet shape affected the spread of the plume.
2) We wanted to determine if the shape of internal changes in diameter of the nitrous flow path affected the density of the nitrous flow.
I believe that the unavoidable changes may have had a minor influence on the result but they are not the major cause of the changes in plume shape and I'm confident that's due to the shape of the change in diameter.
Wise choice by the way and this or better will soon be in use on some very quick vehicles.
Denny,
Correct, although as I said above there is more to it than that, as it leads to confirming one of my main theories!
So more theories then please.