And similar to regen cooling in preburner of NK-33:
http://lpre.de/sntk/NK-33/img/gg_1.jpg
On 01/01/2016 12:26 AM, David Gregory wrote:
Jon-
SSME preburners had a similar arrangement iirc. It's very common
in gas turbine augmentors/nozzles where it's referred to as a liner
On Dec 31, 2015, at 1:15 PM, Jonathan Goff <jongoff@xxxxxxxxx
<mailto:jongoff@xxxxxxxxx>> wrote:
Henry,
On Thu, Dec 31, 2015 at 1:37 PM, Henry Spencer
<hspencer@xxxxxxxxxxxxx <mailto:hspencer@xxxxxxxxxxxxx>> wrote:
On Thu, 31 Dec 2015, Richard Garcia wrote:
Of course, the ways to fend off hot gas, like film
cooling, all come at a price; it may be worth it.
Most LPREs have film cooling, and my previous comments where
made assuming there would be at least some film cooling involved.
I prefer to observe a distinction of terminology: the usual
(although not quite universal) practice of adjusting the injector
design to put a fuel-rich layer near the wall is "curtain
cooling", while "film cooling" is reserved for concepts that put
a low-velocity *liquid* layer on the wall, typically by angled
orifices in the wall itself (e.g., the V-2 engine did this).
Duct cooling is also an interesting approach worth considering for
high lifetime engines. Basic idea is you put a very thin-wall
cylindrical sleeve inside the straight part of the combustion chamber
with a thin gap between it and the chamber wall. You run your film
coolant behind that duct, and there's a gap at the bottom where the
liquid escapes the duct into the chamber just upstream of the
converging section of the nozzle. The duct doesn't see much stress
because it isn't in contact with the actual chamber wall, and it
isn't constrained from thermally expanding axially. The duct can be
made of high temperature materials like Inconel, and can be allowed
to get nice and roasty toasty, because it isn't really load bearing.
The duct keeps the coolant flow intact further into the engine, and
if done right can eliminate the need for most cooling on the engine
with a fairly low overall flow. Not sure how it trades versus other
concepts but it's an intriguing one that I don't know if it has been
used operationally yet. It's also been several years since I've
looked at duct cooling, so I might be mis-explaining it.
P&W's SSME proposal used transpiration cooling
It's my understanding that transpiration cooling, while
successful in a laboratory setting, ultimately proved to
difficult to build flight weight versions that was reliable
enough.
It has problems, both passage clogging and flow instabilities,
but people have made it work. If memory serves, P&W had used it
extensively in an experimental high-pressure engine, and thought
it entirely feasible for the SSME. Reportedly, MSFC dismissed it
as unworkable without paying any attention to the details of the
P&W experience.
Also, if you need an even flow distributed across the face, a
foam-like surface might not be your only approach. I can think of a
few ways of doing things that could be very clog resistant while
still metering the fluids effectively, which are possible with only
somewhat exotic manufacturing processes...
Beware of assuming that the design space has been thoroughly
explored -- often it hasn't! There is a particular problem with
people trying something once, having trouble, and concluding that
the whole idea is infeasible.
Along similar lines, quite by chance today I ran across NASA
CR-185257, aka AIAA 90-2116, Quentmeyer, "Rocket Combustion
Chamber Life-Enhancing Design Concepts", which discusses half a
dozen different concepts for making channel-wall chambers more
durable. Some seem like long shots, some look workable.
(Sorry, don't have a URL for that because I ran across it in my
own files, but it ought to be findable...)
Here's a link:
http://ntrs.nasa.gov/search.jsp?R=19900015867
~Jon
