Peter
I've just noticed a Pj/Ps [Ps/Pj?] of 0.29 for the SR-71 at M3.2 (Peter Law's presentations on AEHS website). Can that tell us anything by itself on how the SR71 installation compared to Concorde?
Not by itself Peter, because as you point out the primary jet pipe area will be increased when you light up the afterburner and that will 'squeeze' the secondary flow. Concorde of course operated 'dry' in cruise. That same website (I think) gives the cooling air temperature at the nozzle and the primary jet nozzle pressure and temperature, so if one knew the fully open jet pipe area (can anyone help?) it should be possible to make some sort of comparison.
As it stands Ps/Pj is higher than a typical Concorde value (0.25) so there should be more cooling airflow, but this will be offset by that squeezing effect.
PS I left out the effect of increased Aj in my earlier explanation as I thought it would complicate things
- that's was why I was careful to specify primary jet area unchanged. I'm guessing that if Abernethy says cooling flow was increased when one lit afterburner than the temperature effect would outweigh the area change ....