Just some thoughts.

[jetjay]

I've been doing a little thinking, and just figured I'd ask a more experienced group what they're thoughts are on these ideas. Now, I haven't done any math on these ideas and I don't expect anyone else to either. It's just that I know someone out there has enough experience to know at-a-glance whether these ideas are worth anything where I would have to really work at a solution.

1: Pulse jet as a gas generator for a turbine, Thoughts?

2: Liquid nitrogen filled pre-cooler ahead of the compressor to increase density of air. (seriously the stuff is cheaper than milk! I'm surprised we don't see it in way more projects in general, not JUST, jets.)

3: Liquid nitrogen filled intercoolers between radial compressor stages to allow for higher compression ratios. (seems WAAAAAY easier to build than perforated blades)

I understand that the last two would add another consumable to the list of things you need to run an engine, but we're already burning fuel and oil at obscene rates (compared to IC engines), so why not?

Again, these are just thoughts, I'm living in an apartment building right now so I'm a couple years away from a build but it's still fun to think.

Thanks for taking a look!

[gidge348]

Hi Jet Jay, Just a couple of notes on your post

May 5, 2016 2:01:12 GMT -5 jetjay said:

I've been doing a little thinking, and just figured I'd ask a more experienced group what they're thoughts are on these ideas. Now, I haven't done any math on these ideas and I don't expect anyone else to either. It's just that I know someone out there has enough experience to know at-a-glance whether these ideas are worth anything where I would have to really work at a solution.

1: Pulse jet as a gas generator for a turbine, Thoughts?

Yep been done John (Racket) has a video of the one he built on you tube, but I can't find it at the moment.

2: Liquid nitrogen filled pre-cooler ahead of the compressor to increase density of air. (seriously the stuff is cheaper than milk! I'm surprised we don't see it in way more projects in general, not JUST, jets.)

Not sure about this are you talking about some kind of heat exchanger or spraying the liquid in? Just spraying the liquid would displace oxygen so decrease efficiency.

3: Liquid nitrogen filled intercoolers between radial compressor stages to allow for higher compression ratios. (seems WAAAAAY easier to build than perforated blades)

The nitrogen would remove heat (energy) from the system so make the engine less efficient. The air cooled stators in large engines are partly to keep them cool and partly to return heat (energy) to the gas stream.

I understand that the last two would add another consumable to the list of things you need to run an engine, but we're already burning fuel and oil at obscene rates (compared to IC engines), so why not?

see above

Again, these are just thoughts, I'm living in an apartment building right now so I'm a couple years away from a build but it's still fun to think.

Thanks for taking a look!

Keep thinking and asking questions that is the way all of us get to learn.

Cheers
Ian...

[racket]

Hi Jetjay

1 ..........Turboprop PJ www.youtube.com/watch?v=uqMn0A2aUdo , not very successful as my conclusion was that a fair percentage of the PJ thrust is created by "pressure thrust" in the combustion chamber with only a portion by the "jet thrust" making it an inefficient gas producer for a turbine wheel .

2........Not a good idea as it would very quickly ice up , but direct injection into the ingoing air has merits , we've discussed using liquid CO2 at ~10% W/W with the air, both mass flow increases as well as pressure ratio for the same rpm

3...........Any sort of intercooler will increase output from the better second stage compression, the lower the temperature going into the second comp the better.

There are a lot of potential variable to increase power from a simple turbojet , the "bleed burn" method uses massive amounts more fluids but has the greatest increases in thrust .

Cheers
John

[racket]

Hi Jetjay

Checkout this doc ........... ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930082793.pdf , page 19.......

Cheers
John

[ripcrow]

John reading page 19. Could bleed off air be used without water injection by having a oversize comp wheel yo compensate for the bleed sir.

[racket]

Yep

[ripcrow]

So from this bleed air we could feed a afterburner with extra fuel increasing thrust

[racket]

Yep

The oversized compressor wheel will require the turbine wheel to work extra hard , so it'll need full expansion across it , so no jet nozzle or restriction downstream, just a diffusing exhaust to maximise the pressure ratio across the turb stage .