I'm wondering if the 'soot' is actually polymerised propellant. Kinda like
the way proving pans gives a non stick surface in cooking. There, oxygen
and heat acts as a catalyst. The resultant material is stable at fairly
high temperature, 200-300C.
Presumably in a combustion chamber the polymerisation is happening at
*much* higher rates. That would be why the layer adheres to the metal;
otherwise I can't see why 'soot' would stick.
On 29 November 2016 at 20:24, Doug Jones <djones@xxxxxxxx> wrote:
The LOX-cooled chamber we tested at Rotary Rocket (Pc>100bar, thrust ~10
kN) produced phenomenal soot layers, up to 4 mm thick in the chamber after
runs of only a few seconds duration. These were a pain in the neck during
engine teardown and inspection, I was as grubby as a chimney sweep. The LOX
_seriously_ over cooled the chamber, and the soot layer only made that more
so.
It had a transpiration cooled throat using water (predicted heat flux 130
MW/m2) so I don't know what the soot thickness through the throat and
nozzle would have been for a fully regen engine. The injector had no
mixture ratio biasing and no film cooling.
Doug Jones, Chief Test Engineer
XCOR Aerospace
1325 Sabovich
Mojave CA 93501
(661) 824-4714 x117
cell 661 313-0584
On 11/29/2016 12:06 PM, Henry Spencer wrote:
On Tue, 29 Nov 2016, Graham Sortino wrote:
...does anyone have a reference to a paper discussing thermal deposits
on Rocket Engine chambers? ...it warrants me understanding it better before
I even consider including its effect in thermal calculations.
Schoenman, "LOX/Propane and LOX/Ethanol Combustion Chamber Heat
Transfer", JP&P 7.4 (July-Aug 1991) has some discussion of it.
The bad news is that it's almost impossible to calculate how much it will
help, or not, because sooting is poorly understood and nobody's got a good
handle on predicting it.
Henry
