More free plans: 40 pound Chinese

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Re: More free plans: 40 pound Chinese

Post by pulsejetgroup » Thu Apr 12, 2012 4:11 am

Hello again Metiz,

Will get photos to you guys soon. We tested today but ran into some problems. We just couldn't get her to pulse. We got ignition and some flame out but no dice on it actually running on its own. We figure part of our problem is ignition source. We are using an electric fence charger that only sparks about once every second. Also we are not sure if we are getting enough fuel fast enough to it. Two tanks connected with maybe 10 ft of hose. We lifted the tanks up which seemed to help but not enough. We are using a shop vac to inject air and we also tried an air compressor and both at the same time too but still no good. We were outside and it was a nice day maybe around 65-70 F but it was pretty windy. Do you have any tips for us? Again thank you so much for your help.

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Re: More free plans: 40 pound Chinese

Post by metiz » Thu Apr 12, 2012 10:39 am

As an alternative ignition source, try some firework sparklers. They will provide a continious ignition for about 15 seconds. What kind of fuel are you using in what kind of cylinder?
make sure there are no restrictors or flow regulators on the tanks or fuel lines.

This engine takes quite a bit of fuel, make sure you are not holding back on the tanks. Actually, if you have 2 decent (full) tanks, it might be easier to start on one tank and once the engine is going, switch on the 2nd one. There might not be enough air to start, however, there might be too much. With engines this size it's easier to use a big volume of air instead of a small, fast one, so try your shopvac.

It would realy help if you have a video of a starting attempt or a pic of your setup.
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Re: More free plans: 40 pound Chinese

Post by pulsejetgroup » Thu Apr 12, 2012 3:40 pm

We did try sparklers but still no dice. We did have a solenoid valve on the line after the two tanks come together which could limit our flow. We are using Propane, two 20-lb tanks. We will try to get the video to you soon.

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Re: More free plans: 40 pound Chinese

Post by pulsejetgroup » Sat Apr 14, 2012 2:16 am

Hey Metiz,

We attempted a test again today with little luck. We got some burps but no long lived independent pulsing.

Here is a link to our best run so far:

http://www.youtube.com/watch?v=Kn4Y0A8o ... S-rUsfs%3D

I will be posting additional videos as soon as I can. Please, any suggestions you, or anyone on these forums have, we would love to hear.

Thanks again!

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Re: More free plans: 40 pound Chinese

Post by metiz » Sat Apr 14, 2012 11:02 am

You need a lot more fuel than that. Get rid of the weedburner and hook the injectors up directly. How full is your propane tank and what is the temperature outside?

I think you need more air to get it going. I always use a small battery powered leafblower.
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Re: More free plans: 40 pound Chinese

Post by pulsejetgroup » Sun Apr 15, 2012 12:03 am

We don't see how we are gonna get more fuel. There are excess flow valves inside the propane tanks ( propane tanks made in the last 12 years) that if you have a large pressure differential will shut off the flow to next to nothing. The weed burners allow the pressure differential to occur way beyond the valve thus allowing maximum flow. From the videos we have watched on your runs, it looks like you get it started off one propane tank (compared to some of our runs with two injecting fuel into both intakes). The injectors we had pinched to similar conditions as yours but even with both tanks full open it did not run nearly as well as the videos shown (weed burners). The shop vac we are running throws a lot of air so I don't know how it could be throwing less than your leaf blower. In addition we tried the shop vac and air compressor but it just blows everything out. The temperature outside was probably 50-60 F however we did heat the entire jet using the weed burners. Do you have older tanks that don't have this safety valve? Do you have any other ideas? In the video posted did it seem like it was getting close to running to you?

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Re: More free plans: 40 pound Chinese

Post by metiz » Sun Apr 15, 2012 11:11 am

I use european propane tanks so I'm not sure if that makes a difference. Sounds like your setup is right. In your video you had it running a couple of times on one intake already. I suggest opening up the 2nd intake and go from there. Please remember that this engine takes a lot of fuel. I have never managed to flame it out on 1 tank. What you could try is hooking up your 2 propane tanks to a single (non restrictive) valve that goes to both injectors so you can simultaniously throttle both injectors.

10 degrees celcius is pretty cold. You may not get enough pressure from your tanks to get the engine going. Heat up your propane tanks, not the engine, to get higher vapour pressure.
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Re: More free plans: 40 pound Chinese

Post by PyroJoe » Wed Apr 18, 2012 6:43 pm

Any luck with this one yet? It looked a little low on fuel supply. I used those type tanks and on that size engine, if you full open the valve for more than about 100 seconds the fuel pressure will drop off rapidly.

Try to preheat the tank up near 100F if possible before each attempt.

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Re: More free plans: 40 pound Chinese

Post by brownms » Mon May 07, 2012 12:55 pm

Hello Metiz...

It's been 25 years since I have built a pulsejet engine and I want to get back into it.
I would rather not repeat everybody elses design mistakes, so I'm looking for design information. I understand that you have set of rules that you use to design your valveless pulsejet engines. Are you willing to share your design method?
Does anyone else out there have a set of rules that they follow?

Mike

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Re: More free plans: 40 pound Chinese

Post by Mike Everman » Mon May 07, 2012 2:35 pm

Look to pyrojoe's recipe for beginners and the essential reading sections at the top of the valveless forum.
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metiz
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Re: More free plans: 40 pound Chinese

Post by metiz » Mon May 07, 2012 2:36 pm

I did not design the M40 with a set of rules. I'd been at it for 5 years and the M40 was an "eyeballed" design (and it needed a lot of rectifying afterwards.) The M25 was designed the same way and that engine works rgeat, kind of hit and miss. If you want to design your own engine, look at the top of the valveless pj forum. There's a sticky called "Pyrojoe's recipe for beginners" follow that guide and you'll be able to whip up a good engine in a singe.

*edit* Mike beat me to it by like 2 seconds - I thought this forum was dead! :lol:
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Re: More free plans: 40 pound Chinese

Post by brownms » Sat May 12, 2012 12:51 am

Hi Metiz...

Your engine designs have two inlets. I understand Pyro Joe uses one inlet.
Will your engines work the same with one inlet of the same area as the two inlets?


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Re: More free plans: 40 pound Chinese

Post by metiz » Sat May 12, 2012 1:14 pm

Yes should work fine. You might get a slightly higher fuel consumption due to a slightly decreased mixing efficieny
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Re: More free plans: 40 pound Chinese

Post by brownms » Sat May 12, 2012 10:52 pm

Hi Metiz/Pyro Joe...

Few more questions:
1. Will a cylindrical combustion chamber work as well as the truncated cone combustion chamber? Advantages?/Disadvantages?
2. Have any of you guys tried direct fuel injection into the combustion chamber? Advantages?/Disadvantages?
3. Have you guys used full-cone spray nozzles for the fuel injection for better air/fuel mixing?
4. Has anyone tried multiple inlets like the Gluhareff Pressure Jet for maximum air entrainment?

I think the bottom line is 'the more air you can cram into one of these engines, the more fuel you can cram in and therefore the more thrust you'll produce.
Enough questions for now.


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Re: More free plans: 40 pound Chinese

Post by metiz » Sun May 13, 2012 5:38 pm

1 The truncated cc is there to prevent any unwanted acoustic effects in the cc itself, disturbing the function of the engine.
2 direct injection results in poor mixing time and therefore a richer burn and a less efficient engine UNLESS you atomize or vapourize the fuel first (and disperse it properly)
3 I haven't
4 Multiple inlets help with mixing, but they ristrict breathing because of the larger surface area. for small engines, just use one inlet. For bigger ones I wouldn't go over 3.

bonus question answer: Yes, but there's a limit. More air+ more fuel means higer pressure and higer temperature. If the pressure and temp go to high, the acoustic profile of the combustions change so much that the exhaustpipe will no longer work. If you want to add "unlimited" air into the cc, you'll need some sort of dynamic tailpipe so it can change shape as you go.
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