Hi folks,
Sorry this is a bit cryptic but I'm scared to spend too much time typing words in case I lose the whole lot with one wrong mouse click. It's already happened.
Good news for oldBUFFkeeper,
Six tube BPR is 0.25 as they passed 20%. See below for this and much, much more
http://www.enginehistory.org/Convent...ropulsion2.pdf
Hope this new revelation on low flow reqd raises your opinion of the elegance or lack of it for the tubes.
BTW Jane-DOH had already summed them up in one line although I think the relevance of the statement was missed, ie "there's only a certain degree of efficiency you need to accomplish a task. The rest is gravy" or big waste of money actually.
The apparently crude tubes were engineeringly elegant I'm sure ie reqd min mods to min # of components They did what was reqd cheapest and lightest and durable.
Following answers come from "The Engines of Pratt & Whitney, a Technical History" by Jack Connors
There are 3 pages on J91.
J91 compressor, in order to pass req flow for M3 with smallest size, hadnew low level of hub-tip-ratio, about 1/3 re previous 1/2, and also transonic blading so no IGV reqt. JT3D fan was slightly scaled down 1st 2 stages.
Finish off with thought for the day:
overall
PR of subject matter above at M3 is today attained by your big fan engines at zero flt speed, ie over 40:1
That's about it for now.
Any more P&W Qs I can look up for you in the book.
Thank you all for renewing my interest in above details.
PK