Martin:
Gas velocity at the head (bulkhead) end of the combustion chamber is
lowest, thus pressure measurements at that location are little effected by
this issue.
Gas pressure at the nozzle is typically slightly higher than at the
bulkhead end, but not typically by very much. If one really wants that
measurement than the nozzle throat is the correct location where, by
definition the velocity is Mach 1. The issue then becomes the introduction
of shock waves into the gas from the presence of the pressure measuring
port. I am not aware of any sufficiently accurate simulation that would
allow deducing stagnation pressure with confidence in this case.
Alternately, one can tap pressure at the top of the nozzle (either at the
nozzle entrance or at the chamber wall) where gas velocity is typically
low. In a hybrid, in particular, the recirculation zone at the base of the
grain will typically have very low gas velocity.
Bill
On Tue, Jan 21, 2020 at 4:20 AM Martin Olde <MARTIN_OLDE@xxxxxxxxxxx> wrote:
Hey everyone,
A friend has posed me a question about hybrid propulsion (but solid or
liquid propulsion should not differ much):
How do you experimentally determine total temperature and total pressure
at the nozzle inlet if there are high port velocities? Are there standard
ways of deriving these properties from more easily measured values?
kind regards/ vriendelijke groeten,
Martin
