|
|
Post by wannabebuilderuk on May 19, 2020 4:11:37 GMT -5
|
|
|
|
Post by racket on May 19, 2020 4:23:22 GMT -5
|
|
|
|
Post by wannabebuilderuk on May 19, 2020 18:56:14 GMT -5
Jesus john, you're practically the mechanical aussie version of tesla lmao. How did the prop thust compare to the pulse jet?
|
|
|
|
Post by racket on May 19, 2020 19:32:25 GMT -5
Prop thrust was poor , I eventually came to the conclusion that PJ thrust is a combination of "reaction thrust" from the expelled gases plus "pressure thrust" from the differences in surface area of the combustion chamber , the front surface being greater in area than the rear surface which has a "hole" where the exhaust pipe is, so when the "explosion" happens theres more force ( thrust) put on the front than the rear. Theres a "Build Thread" over on the PJ Site www.pulse-jets.com/phpbb3/viewtopic.php?f=2&t=2349&hilit=turboprop+pjThe PJ experiment was a distraction from turbines for a short while after getting the TV84 turbine bike sorted . Without the prop being fitted, the freepower was able to be spun up to >20,000 rpm unloaded , it didn't make much difference whether the connecting sleeve between PJ and freepower duct was in place or not , the PJ "breathed" back through the freepower . If it was done again I'd recommend doing things slightly differently , having the freepower shaft at right angles to the PJ pipe and use a "scroll" arrangement like I did with my 12/118 freepower stage to get a "better" alignment . I ran the PJ on both liquid propane and/or petrol , it was a strange beast that took a while to get sorted but in the end starting was very simple and quick . Cheers John |
|
|
|
Post by racket on May 19, 2020 22:54:34 GMT -5
|
|
|
|
Post by slittlewing on May 20, 2020 2:31:26 GMT -5
That’s quite a fascinating experiment John!! I would never have thought of or considered adding a free power to a PJ haha. Great work!!
|
|
|
|
Post by racket on May 20, 2020 4:27:19 GMT -5
LOL..........I thought I might as well try something "different" ;-)
PJs are strange beasts, and there are things that probably could be done to improve their ability to more effectively power a freepower , longer pipework to reduce "frequency" would be a start , turning it from a high revving short stroke motor to a long stroke diesel .
Also maybe fitting the freepower at mid point of the engine closer to the combustion chamber .
But I doubt they'd ever compete with a standard gas turbine engine , but the bragging rights would be better :-)
Cheers
John
|
|
|
|
Post by racket on May 20, 2020 19:28:10 GMT -5
Hi Guys Its a wet miserable day with nothing to do, so heres some more pics of the PJ setup , its interesting going through old pics    And the sliding sleeve that joined the PJ to the freepower ducting to make the PJ breath back through the turb wheel  |
|
|
|
Post by racket on May 20, 2020 19:33:53 GMT -5
And a few more Sliding sleeve  Fuel pump  Gauges and switches for the various pumps , ignition etc  Starting air cylinder ( WW2 aircraft oxygen cylinder) with small 12v air comp to fill it  |
|
|
|
Post by racket on May 20, 2020 19:38:05 GMT -5
Front end with "horns" that were fitted with 2 stroke piston engine "plastic" reed valves and their mounts   fuse board and some plumbing  Expansion witness marks , the PJ was mounted at the front and was allowed to expand rearwards , sliding through the "saddle" , ............lotsa expansion , it got kinda hot  |
|
|
|
Post by racket on May 20, 2020 19:46:06 GMT -5
Inlet to the freepower ducting, because theres no pressure ratio across the freepower the ducting needed to maintain a constant flow area as the gases were turned in the "NGV" , the NGV "throats" were the same area as the exhaust pipe, actually a tad bigger to account for any losses in the turning process , I only provided a modest turning angle of ~60 degrees if I remember correctly , this could be increased to ~75 degrees I feel without too much problem 
"Bump bearing" for the long power shaft
Fuel valving was messy due to trying to combine petrol and propane
Turbine blades took a hammering from the extreme temperatures and pulsing , they were only segments of stainless tubing with minimal bend/deflection , again another area where power could be improved by greater deflection
And finally the poor old shaft tunnel and bearings , the heat got to them badly , it looks like I added air cooling , but that wasn't enough
 Cheers John |
|
|
|
Post by racket on May 20, 2020 22:31:36 GMT -5
|
|
|
|
Post by wannabebuilderuk on May 21, 2020 16:32:54 GMT -5
Man john that's rather impressive, what is just a little fool around/test to you is practically a project that accompanies a scientific paper for us in my opinion lmao. You have some great knowledge and skill so I tip my hat to you.
|
|
gidge348
Senior Member
Joined: September 2010
Posts: 426 
|
Post by gidge348 on Aug 1, 2021 21:03:04 GMT -5
Approximately 4.24 kg spread over 2 wires. |
|
