Mike's Build Log

metiz · Post by **metiz** » Tue Mar 24, 2009 11:49 pm

Hey Mike, looking good! (and the engine to; har har)

I've not been following this thread for some time and you might have mentioned this before, but why don't you try an expanding tailpipe for some more thrust with (don't know how thick that tailpipe is) almost no (if any) aditional weight?

Post by **Mike Everman** » Wed Mar 25, 2009 4:27 am

Why, indeed! For what I want to do, I want the highest gas speed and hottest exhaust. I'm close enough to my goal with this one, now I can take the next step (and it's not an expansive tail

Here's the video.

http://www.pulse-jets.com/pocket%20jet2x1.2%205meg.wmv

Post by **Mike Everman** » Wed Mar 25, 2009 5:29 am

Here's a vid of the test stand bearing and the first fuel up, without thrust gage, just getting the feel of it. Quite an easy starter. I think a fixed Rossco would make a good air free start.
http://www.pulse-jets.com/mikesbuilds/p ... earing.wmv

metiz · Post by **metiz** » Wed Mar 25, 2009 2:07 pm

Mike Everman wrote:I want the highest gas speed and hottest exhaust. (and it's not an expansive tail

http://www.pulse-jets.com/pocket%20jet2x1.2%205meg.wmv

Hmm revamping the tailpipe into one with an integrated augmenter?

GRIM · Post by **GRIM** » Wed Mar 25, 2009 2:08 pm

Geat engine , excellent videos,

5.4Lb from only 0.9 liter Wow , and the strain gauge is impressive too ,
Well done Mike
G

Post by **Mike Everman** » Wed Mar 25, 2009 4:24 pm

metiz wrote:
Hmm revamping the tailpipe into one with an integrated augmenter?

Yep, and also a free power turbine, and also a whirly motor.

Thanks guys. I'm really stoked about this one.

hinote · Post by **hinote** » Wed Mar 25, 2009 5:59 pm

Mike Everman wrote:
metiz wrote:
Hmm revamping the tailpipe into one with an integrated augmenter?
Yep, and also a free power turbine, and also a whirly motor.

Mike:

Nice job!!

Looks like you could augment both ends.

Bill

Post by **Mike Everman** » Wed Mar 25, 2009 7:01 pm

Yep. After a little detour, I'm going to build both conventional augmenters and a new type "to be named later". I'm torn right now between super augmenters and shaft power. I'm about to make a 3x pocket jet, 3 intakes, 3 exhausts, common elliptical cc, which will be my 1.5L entry. That will be of interest to you, Bill, as it will test the notion that all length and areal numbers times three will get me 3x thrust, which would push 10 lb hopefully. I'm sure that the 3 intakes with 3x duct areas and a single exhaust does not follow this reasoning, and must be longer.
I'll post the rendering when I get back to my project computer.

Edit: I meant all areas tripled, all lengths the same.

Post by **Mike Everman** » Thu Mar 26, 2009 4:49 am

Here's the triple. I think I want to bump up the intake dia, considering how well the upscale went at a little higher confinement ratio.

milisavljevic · Post by **milisavljevic** » Thu Mar 26, 2009 5:55 am

SUH-WEET!!!

Something is curiously "automotivey" about this design...

Cheers!
M.

Graham C. Williams · Post by **Graham C. Williams** » Thu Mar 26, 2009 9:39 am

Dear Mike.

What a lovely little motor (>5Lbs) Well done!
Ref the lower thrust value. It is a possible that the motor is producing negative thrust (Positive thrust but in the other direction) at your lowest fuel settings, it's easy enough to check. What impresses me is the resonate combustion at these low fuel settings.
So how are you going to get this motor up to 30+ N/L? Ha.

Great work - Lovely motor.
Graham.

Post by **Mike Everman** » Thu Mar 26, 2009 1:32 pm

thanks guys,
Yeah, Graham, the zero reading makes me want a more rigid link to the loadcell to see if it actually goes negative. Doesn't seem possible. Intake exhaust at that low setting is positively cold!

milisavljevic · Post by **milisavljevic** » Thu Mar 26, 2009 2:25 pm

Hello Graham (and Mike!) --

Graham C. Williams wrote: It is a possible that the motor is producing negative thrust [snip] at your lowest fuel settings[?]

You know how timid I am when it comes to interjecting maths (or facts) into any discussion of pulsed combustion!

As a duct is throttled down, its forward pressure ratio (and similarly, thrust split) declines to a limiting value of 1.*

It is entirely possible (and for deep-throttled poket-jet style ducts, near certain) the net intake thrust is negative.
This said, the overall net thrust must remain positive or zero, if the duct is in equilibrium under static conditions.
Boundary layers may absorb enough momentum to result in net nil thrust, but the boundary layers work both ways.

Graham C. Williams wrote: How are you going to get this motor up to 30+ N/L?

I know that you're simply teasing Mike, and that this small a duct can easily surpass 30 N/liter, but you also know
volume-specific thrust density moves inversely with thrust class: "The bigger the cushion, the thinner the pushin'!"

Cheers,
M.

*To eliminate any possible ambiguity, the pressure ratio goes to 1; net thrust split (as a ratio) goes to 0.

Post by **Mike Everman** » Fri Mar 27, 2009 5:06 am

Some progress on how it's going to go.

Post by **Mike Everman** » Fri Mar 27, 2009 5:14 am

one more. just having fun with the renderer.

www.pulse-jets.com

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