Jet engine development.

[Artisi]

Here is an interesting development in jet engines.

http://vimeo.com/45136248

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[pmover]

Interesting. Very ambitious . . . Well, wait and see i suppose.

 

[patprimmer]

Interesting, however the actual operating principle kinda got past me. Maybe I wasn't paying enough attention.

I kinda suspected it was that by supercooling the inlet charge you could then get a greater heat rise before hitting critical temperatures for internal components?

I also kinda started thinking is thrust generated by the drop in pressure as the air cools and the plane is sucked forward as the air is sucked back, ie the reaction from the plane to the movement of the air?

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[handleman]

Yeah, that interview was rather short on actual technical detail/achievement and long on pie-in-the-sky, if-this-stuff-works type speculation. The only actual technical detail they mentioned was that they have developed a super-fast acting heat exchanger.

I could make the same interview about cold fusion.

-handleman, CSWP (The new, easy test)

 

[zdas04]

The only place in the process that you have temperatures in the 1000C range is at the compressor discharge, so it isn't a pre-cooler, it is an after cooler. To go to -150C in 1/100 sec is a big damn thing in many applications (a pre-cooler in front of a demethanizer jumps to mind, those things are huge today). Not to mention what it is designed for. I would pay a lot to get from LAX to Brisbane in 4 hours instead of 48.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[SomptingGuy]

My shower can do that thermal transient, no problem.

- Steve

 

[ivymike]

The only place in the process that you have temperatures in the 1000C range is at the compressor discharge

I am not sure that's true at mach 5, if you slow the air to subsonic speed before mechanically compressing it. I don't have the time to go look it up at the moment, though.

 

[Pud]

Not sure if out of UK can access the BBC website: BBC,
But they say:

But it is a challenging prospect. At high speeds, the Sabre engines must cope with 1,000-degree gases entering their intakes. These need to be cooled prior to being compressed and burnt with the hydrogen.

Reaction Engines' breakthrough is a module containing arrays of extremely fine piping that can extract the heat and plunge the intake gases to minus 140C in just 1/100th of a second.

And I still have no idea....

H



www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[zdas04]

I stand corrected. At speeds where you can consider air to be incompressible (less than about 0.6 Mach), the only place you have that kind of temperature is at the compressor discharge. Compressible flow is a different kettle of fish. It is easy to forget that. I'm still not convinced that you can get that kind of heat from friction (air really is a crappy heat exchange medium), but I'm no longer certain that you can't.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[ivymike]

Not sure it's really friction - when you bring a very fast stream to a "stop" the molecules take the kinetic energy that they had as part of the stream and internalize it as "temperature" - but that might be the same as saying that they stop all moving in the same direction and go bouncing around randomly at about the same speed.

 

[btrueblood]

Adiabatic heating at high speed can easily give those temperatures. The plane needs approx. Mach 11 or 12 to achieve orbit; at Mach 5, the compressor inlet would see about 1300 C air temperatures due to adiabatic heating (depending on local static temperature). To/Tstatic = 1 + (r-1)M^2/2

Without pre-cooling, there is no room left (at Mach 5) to add heat via combustion (and thus generate net thrust) before you start melting the walls of the combustor - and that is for a ramjet that has no turbine blades. For a turbine engine, even one that can bypass a large fraction of the air flow away from the turbines and operate in partial ramjet mode (i.e the SR-71 Blackbird), the upper limit is about Mach 3 to 3.5, and those speeds are at high altitudes where air is much cooler to start with.

Big problem, it would seem that an awful lot of LN2 needs to be carried to do all that pre-cooling...and an awful lot of structure for the tanks, pumps and heat exchangers. Not clear if there is a net weight savings due to carrying less oxidizer for the rocket stage, but presumably there is (or will be...on paper...). If the N2 boil-off was allowed to happen at a high enough pressure that it could be used for film cooling in the turbine and/or nozzle, then maybe there's a net advantage...or I might be missing some other trick to tweak a bit more thrust from venting the N2.