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Improved plan of K-PT 01
Posted: Fri Mar 26, 2004 8:17 pm
Here is the plan of the improved K-PT 01.
Thanks to Milisavljevic for recalculation!
Starting was much easier with the longer tailpipe, but the expected thrust is higher (3,0kgf - refering to Milisavljevic - but with the 41mm tailpipe outlet). Once gotten hot, the improved engine runs "smoother".
-A cone with a 30Â° cone angle and a length of about 12mm at the intake opening would be better than the "bell mouth".
- The optimal tailpipe outlet is 41mm!
- The sraight injector isn't optimal, but works for first tests.
Posted: Fri Mar 26, 2004 10:06 pm
GREAT! Pictures? Are you saying you started with 39mm exit, and changed to 41, or was that M.'s suggestion?
Posted: Sat Mar 27, 2004 7:28 pm
I calculated 39mm and Milisavljevic corrected it to 41mm. He said the thrust with the 39mm outlet would be nearer to 2.9kgf.
You can see the cc and intake nozzle with the starting assembly at the last picture of site 3 (unchanged). I improved the tailpipe by just cutting off the 3rd/last conical part of the tailpipe and making a new, shorter one then.
Posted: Sun Mar 28, 2004 5:18 pm
...especially for you, Mike...
Thanks to my friend Sven, who has taken the pictures!
Posted: Sun Mar 28, 2004 9:18 pm
thanks for the photos, Marten! It was all I hoped for, and more. I laughed, I cried; it made me want to call my mom just to say "hi". ;-P
summary (part I !?)
Posted: Sun Apr 18, 2004 6:09 pm
I improved the patent engine (now K-PT 03a) and the tiny engine I mentioned one day (also didn't want to run) in the forum (now K-PT 04a) after observations and experiences at different engines.
This three engines (->picture) are running pretty good and are mostly regulatable over a wide range (03a from 1/4 turn to nearly full opened, 01a from nearly shut to almost 4/5 full opened, 04a from nearly shut to almost 3/4 full opened main propane valve). In every one of the three engines is used the "pipe with holes" vaporizer. Till today I got best results with this simple injector. Trying other methods of injection at the SP-14c hasn't been succesful, but I have some more ideas in mind.
It also seems to me that engines under 50mm CC ID don't work, at least on propane and/ or my injector.
Some observations at testing my engines regarding to the STARTING PROCEDURE:
-The first could be useful for anybody, especially for people not living in the "sunshine belt" is that engines are much easier - at low temperatures maybe only - to start with preheated starting air. My hot-air gun broke down last month. But the electric motor could be saved, so I still have an air source to work with. But on cold air delivery the K-PT 01b engine didn't want to start, whether it did very simple with hot air. I used - and still use - a torch to preheat the outlet of the "gun" and the intake noozle of the engine and immediately the engine began to operate self-sustained.
-It was also better, especially with the "torch starting methode", leaving fuel delivery at a lower level (just a bit above the minimum operating fuel flow). By forcing air through the engine it becomes - more or less - slowly hot and swings into its resonance frequency. It is time to put the air source away when the engine begins to run with the typical pj sound, or rather, when it first does so and seems to get out of this frequency with some unregular pops (still forcing air through the engine when it seems to run).
-When using a hot air gun or something like that, a kind of noozle, eventually with a slit shape might be advantegous (at least at smaller engines).
The video showes the K-PT 04a in action, running nearly 1/2 of full throttle, that's why it pops a bit unregulary. These pops don't appear at low and at least 3/4 throotle.
I hope I didn't leave anything out...
Posted: Mon Apr 19, 2004 5:07 am
Great photos and video, Marten!!
Posted: Thu Apr 22, 2004 7:15 pm
The longer video is about 1MB. If somebody wants to have it, I could send it per email (also WMV format).
Posted: Thu Apr 22, 2004 8:04 pm
Marten, do you have a plan of your K-PT 04a?
I have got the metal so now I only need a plan of the little pjet.
K-PT 04 different experiments and frequency analyzing
Posted: Sun Apr 25, 2004 7:06 pm
1.: I'll post the plan this week.
Because of the reason I like small or rather tiny pulsejets (they don't consume much fuel; good for my small amount of money...), I did some tests with 60mm/2.36" CC ID engines. The K-PT 04a engine is the basic operation unit (overal length 886mm/ 34.88"). I still cannot measure any thrust (I'm looking forward to build something after exams), but the engine starts pretty easy with some pre-heating of the starting air. I thought of performance improvements by rising the operating/ resonance frequency to a higher level. Therefor I build a second engine having a shorter inlet and outlet cone, but with possibilities of a long and a short test version (K-PT 04c long/short now). I simply lengthened the tailpipe/ -cone with with a suitable piece of pipe. The result was that the smaller engine wasn't startable (at least with torch starting), the longer engine started very easy. When the longer engine had been running for a few seconds (till it got hot a bit), I could take the lengthening pipe away and the frequency jumped upwards, of course, immediately. The engine was better (in a wider range and faster) "throttle-able" than the longer version.
I noticed the same things that Bill H. mentioned at his report of the QD-88 tests, after changing fuel flow the engine needs a few seconds (5-8sec, I didn't measure) to restabilize again.
And here is my question: How can I make a frequency allocation/ split with a PC from a video or sound file of a running engine? Which programs do you use?
I think Mike E. posted such images of his running Locky Kazoo to the forum; very useful stuff.
Posted: Sun Apr 25, 2004 9:37 pm
Marten, I think the variable length tail has been discussed a lot, but I just love the idea of a starting cone that gets pulled away when you're running. Designing for the higher frequency, of course requires that your mixing is up to the higher frequency ;-) I must try this! Nice work.
I am not sure what you're asking about the video, but all I did was use a Logitech web-cam. The sound recording is unusable for anything but raw combustion frequency, and even that was represented at 2X, so clipped it was a square wave.
Re-reading, I think you are asking for FFT software. I got a shareware program that works well called Realtime Analyzer RAL. works well for $20 US. Download for 30 day trial. Great tone generator, o-scope and FFT.
Posted: Mon Apr 26, 2004 6:36 pm
(1) Thanks for your info Mike!
Ther is just one poor thing: I don't have a credit card!!
Maybe im writing a bit compilcated, because you, but also others, are writing "after re-reading"...I think I'll still have to improve my English in many ways...however, I don't take it too hard.
I found a piece of gutter pipe (85mm/ 3.35" OD) "hidden" in the garage. I think I'll have to build a "locky kazoo" next...
(2) Here is the plan.
Propane injector/ vaporizer info: I made the propane injector out of 12mm/ 0.47" OD (10mm/ 0.39" ID) steel pipe. The holes should then be angeled 90Â° to centre line and 180Â° to each other. There should be 6-7 holes (inline) on each side of the injector with an ID of 1.8mm/ 0.07". The (propane) injector pipe is only pressed together at the end (NOT along the length!), which finally has been welded up for getting a closed end. I use a self-build M12 connector nut/steelpipe assembly (7mm/ 0.25" ID).
You can add an intake cone to the engine (insted of the bell-mouth), which would have to be 11mm/ 0.43" long and should have a mouth-opening ID of 29mm/ 1.14".
The engine doesn't need very much fuel. I opened the propane main valve about 1/4 to 1 turn or so (I didn't count the turns or parts of one).
(3) Here is a video, containig "both" engines run. Perhaps somebody can analyze the frequency.
The short version DOES NOT start with the torch starting methode and the straight vaporizer/ injector I'm using at every of my engines.
Posted: Mon Apr 26, 2004 7:58 pm
I have got 0.75 mm steel. Do you think that is thick enough?
Do you think that an even smaller engine will work?
I like small jets!!!
Posted: Tue Apr 27, 2004 7:25 pm
(1) 0.75mm thick sheet steel should be optimal. It is easy to work with (you can get really nice results, even with simple rolling equipement) and should also be stiff enough (support at CC and at the last 1/3 part of the tailpipe is a must(!), else deformation appears).
(2) The K-PT 04 types are the smallest running engines of mine. I've build a smaller one (45mm/ 1.77" CC ID). It does not run self-sustained (but with forced air I get some signs of "self-sustaining-will"), at least with the straight injector and on propane. I'm planning to build an engine with an CC ID of 51mm / 2". With my actual "stage of development" it should be the smallest running engine.
(3) I also like small pulse-jets! They don't consume the typical huge fuel volumes and I don't need a lot of metal. They are also simply runable clamped in a vise. Just fascinating "noisy-fire-pipes"...
Posted: Tue Apr 27, 2004 8:29 pm
The sound file of the previous video has a waveform of 535 and the second engine is at 571. This is not the pulsation frequency, of course, it's a harmonic of it. So if it's the 2nd mode, then your operating frequency is 267 and 285. Seems high, but matches pretty well against a tone generator, but that can be decieving, too.