FWIW Concorde for comparison ran something like an 81:1 overall pressure
ratio (including the inlet compression) at Mach 2.05 and had to have nickel
metal on the final compressor sections as well as the traditional 'hot'
section. It was ~43% energetically efficient at M2.05, which is very high
for a jet, modern high bypass subsonic jets are only now approaching that.
But it had to be like that or Concorde would have run out of fuel mid
Atlantic.
It's always a thermal limit with airbreathing jet engines.
Presumably the OPR, including the inlets, for SABRE would be several
hundred. Actually, come to think of it, that should be very comparable to
Concorde given that the effects of inlet compression has been dealt with in
the SABRE design by the precooler. SABRE would need more compressor
sections to reach 84:1 in the turbocompressor but that's about it,
temperatures reached should be similarish to Concorde.
On 18 February 2018 at 00:16, Keith Henson <hkeithhenson@xxxxxxxxx> wrote:
Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx> wrote:
Am 16.02.2018 um 17:07 schrieb Keith Henson:
The rest of it is turbomachinery of the sort we have
been building since WW II. (Though I must admit that 84 bar is a lot
of compression.)
84bar or pressure ration 1:84 ?
At sea level 84 to one. That's about twice what is used in a 787
engine. The only reason this works at all is that the air is cooled
to around -140 C.
As it goes up, (as I recall) the inlet pressure (from ram air) falls
to around half an atmosphere. That about doubles the compression
ratio.
The US branch of REL (and the AFRL?) are building a test setup on
Colorado. Why I am not sure, but I do recall the engineers griping
that LH2 in industrial quantities is just about impossible to get in
the UK.
Keith