From our experience, impinging injectors work well for nitrous and LOX, and
the heat in the head end of the motor (once it's lit) is plenty to vaporize
the droplets and sustain combustion (no TEA needed, at least for the
smallish motors--2800 lbf max--we've tested). The hard(er) part is
generating enough heat initially to get the whole thing going (to
dissociate the nitrous and to vaporize the LOX). We like big, long-burning
(5 to 8 sec) igniters.
We have chilled the nitrous supply tank with icewater in the desert,
getting the nitrous down to say 40 or 50 deg F (just a guess, no
instrumentation). We haven't taken it down below that but I would think
with proper injector design and a top pressure on the nitrous, it should
work fine.
Now for bigger motors on the scale of SS2, I don't know. It does seem like
the methane system was tacked on to solve some kind of combustion problem.
On Tue, Aug 4, 2015 at 1:06 PM, Bill Claybaugh <wclaybaugh2@xxxxxxxxxx>
wrote:
As best I can tell, liquid rocket injectors work because there is a heat
source that vaporizes the fog created by the injector (i.e., the combusting
gases): both are required to get vapor on vapor combustion.
Just making a fog of oxidizer at the head end of a hybrid motor will not
produce vapor, that requires heat.
Bill
Sent from my Commodore 64
On Aug 4, 2015, at 2:54 PM, Andrew Burns <burns.andrew@xxxxxxxxx> wrote:
Is there a reason while traditional like on like impinging injectors can't
be used to atomise and subsequently vaporise LOX or nitrous in a hybrid? Is
it something to do with getting the droplets to interact with the fuel
boundary layer?
Andrew
On Wed, Aug 5, 2015 at 6:37 AM, Bill Claybaugh <wclaybaugh2@xxxxxxxxxx>
wrote:
Mark:
It seems like an AN & ice water mix could be tailored to your temperature
goals. But why not go to a dry ice cooler and maximum density: a single
pass on a couple of coils should get you what you are seeking. LN2 is also
obviously an answer; both can be had in Mojave.
As Anthony has hinted, you will need a heat source at the head end to
assure the N2O fog is vaporized, otherwise combustion will be rough and
unstable. At Amroc we injected TEA throughout the burn to vaporize the
Lox; I gather VG is using Methane in the SS2 nylon motor.
Bill
Sent from my Commodore 64
On Aug 3, 2015, at 9:33 PM, Mark C Spiegl <mark.spiegl@xxxxxxxxx>wrote:
high density Nitrous. Im looking to cool 20-50 lbs of Nitrous to 25-ish
Wow... Im out of the office for a day and my inbox is full! :-)
Anyway.. Anyone who has followed my hybrid projects knows Im a fan of
degF.
burning 10-20 lbs of Nitrous. Much above 20lbs (esp in the desert),
Goals:
(1) Flashing liquid to vapor to chill Nitrous is fine in a motor
flashing liquid to gas becomes impractical. I would like to start a little
closer to my target temperature of 22 degF. The Peltier, Stirling Cooler,
or whatever would chill the supply tank, not the rocket tank.
little more elegant and deterministic. Bags of ice aren't a great answer at
I know ice is a quick-and-dirty answer, but I would like something a
FAR or Blackrock.
Cold weather is no problem. I cannot prove what is happening, but I suspect
(2) I have had trouble igniting high density Nitrous in warm weather.
temperature gradients in the long thin Nitrous tank are causing the
problem. If the Nitrous is 22 degF at the top of the tank, it may be much
much colder at the injector. Supplying Nitrous close to the final
temperature should help mitigate this problem, if Im correct.
the top and bottom of the rocket's oxidizer tank???
A related question: Any simple ways to equalize temperature between
electronics... ie Peltiers)
--MCS
(Im an EE kind of person so my solutions tend to feel like