The choices aren't 90 deg horizontal or vertical.
One can tip it down so it mostly drains.
Being sure that excess fuel can't get in the oxidizer is important.
How much you need to tip will depend on your injector geometry.
A Lox centered pintile probably drains well enough that horizontal works.
A system with drilled lox holes around the periphery will need to be tipped
much more. My standard would be that with the engine filled till it drains
out the nozzle the fuel can't be deeper that the lowest lox port...
A lot will depend on what fuel you use.
If your running something like alcohol that evaporates well with out
leaving residue then a good purge might suffice.
Otherwise a disassemble and cleaning of everything after the main lox valve
is prudent whenever you have a ignition or valve actuation failure....
On Mon, Apr 25, 2016 at 5:21 PM, Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
wrote:
Randall,
For a horizontally mounted engine, it is likely that if you pour fuel in
the end of the engine that it will also back up into the oxidizer injector
holes, depending on their position. Is a gaseous purge really enough to
clean out all traces of hydrocarbon in those lines? It must work since
you're suggesting it (and using it) but it seems like there could still be
some fuel left in the lines afterwards. How long of a purge do you use?
-Bob
On 04/25/2016 05:42 PM, Randall Clague wrote:
Easy to test, too. Load fuel. Do not load LOX. Disconnect igniter power.
Disconnect LOX Pre and LOX Main, because Murphy. Cold flow fuel. Safe the
stand. Pour fuel into chamber until it runs out the throat. Return to
bunker. Purge. Safe the stand and inspect the chamber.
If you want to be extra conservative, test with a liquid of higher
viscosity than your fuel.
Check your LOX system for fuel contamination afterward. Not because
there's any reason to believe there is any, but because if there is, this
is a good opportunity (fewer variables than usual) to find it and isolate
it.
-R
