If you want to eliminate hole effects and monitor combustion stability then
a flush mounted piezoelectric transducer is the way to go. The ones I've
used are heat shielded and water cooled.
https://www.kistler.com/en/products/components/pressure-sensors/?pfv_metrics
=metric
<https://www.kistler.com/en/products/components/pressure-sensors/?pfv_metric
s=metric&pfv_pressure_applications=gas_turbine%2Ccombustion_engine>
&pfv_pressure_applications=gas_turbine%2Ccombustion_engine
PCB in the US also makes similar versions but I've never used them. I'm told
the PCB units don't offer the same temperature stability that Kistlers do
but I can't confirm that.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
<http://www.cesaronitech.com/> http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On Behalf
Of William Claybaugh
Sent: Tuesday, January 21, 2020 10:01 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Nozzle total conditions
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
<mailto: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
