Another pulsejet kick from Sweden

[erik]

That bad?

[WebPilot]

No way. I used the term as found here:

Urban Dictionary: geez louise

3. geez louise

oh my gooooodddd, i can't believe it.
when something is unbelievable.

[erik]

Some more progress!

[erik]

And almost a success.
I made the first test run today, but i couldn't make the engine self sustain.
I think one problem is that the 0.3mm redd valves are a bit to stiff, when i first tried the valves at assembly i noticed that i couldn't blow hard enough to open the valves at all so i tried to make the valves so they are a little bit open at default.
Another problem could be the cheap leaf blower.
I am also planing to try injecting half of the fuel in the CC, to make it less likely to get fireballs out of the intake when starting .


WebPilot:
What do you think of using 0.25mm reeds like in the solar instead of 0.3mm?


Here is a short clip of when we almost got it to run.
It definitely have some power , the kick is hold i place by the log but you can see how it moves.
I think the sparks is burning soot from the earlier startattempts .
http://hv4all.com/pulsejet/ny/pulsejet.wmv 5.9Mb .wmv

[WebPilot]

Erik,

Why are you trying your first starts outside in the cold? Do you think pre-heating of the aft area of the combustion chamber and neck-down region would be a good idea?

> when i first tried the valves at assembly i noticed that i couldn't blow hard enough to open the valves at all so i tried to make the valves so they are a little bit open at default.

I realize what you are trying to do here but ... it has been my experience with pulse combustor numerical simulations of operations, for the realization of a 'self sustaining' cycle, these valves need to be closed when the pressure differential is zero (default as you say).

> WebPilot:
What do you think of using 0.25mm reeds like in the solar instead of 0.3mm?

Well, didn't they write in the article they achieved a valve life of only 15 minutes?

As for air, let's look at your intake.



You've pretty much "blocked off" 1/3 of your intake area.

Why did you decide to go with a cone of smaller dia to a larger dia instead of one of larger dia (> cc dia) to a smaller dia (= cc dia)? You don't need a venturi here since you are using lpg, yes? or even go with a short straight tube whose ID is the same as the cc OD? I don't remember reading the V-1 having one at all.

Mind you, Erik, the above is meant for constructive criticism only. I think you are doing a remarkable job.

Furthermore, thanks for the wonderful video. I think I got just as excited as you, when it first tried to "breathe fire".

As soon as I get some time, I need to do some "sleuthing" with it.

[erik]

>Why are you trying your first starts outside in the cold? Do you think pre-heating of the aft area of the combustion chamber and neck-down region would be a good idea?

Because i cant run it inside, and i cant change the temperature outside, pre-heating could be a god idea.

Well, didn't they write in the article they achieved a valve life of only 15 minutes?
No, but iam not sure, but right now even 7 minutes would be enough for me


>
You've pretty much "blocked off" 1/3 of your intake area.

Why did you decide to go with a cone of smaller dia to a larger dia instead of one of larger dia (> cc dia) to a smaller dia (= cc dia)? You don't need a venturi here since you are using lpg, yes? or even go with a short straight tube whose ID is the same as the cc OD? I don't remember reading the V-1 having one at all.

The smaller intake hole area = the total valve area, ( valve area= (0.8cm x 1.4cm )x 18 ~80cm2, intake area= ID=105mm =86.5cm2

I am using Gasoline and i needed the smaller diameter to be able to keep the fuel mist inside the intake during starting,

[Eric]

If the valves wont open by blowing in them you need to go thinner, having them closed by default is important.

That should make a big difference, what kind of spring steel are you using?

Those bursts also seemed to be at a fairly low throttle level... with easier opening valves, and more fuel, you should have it.

[WebPilot]

 It seems to me I remember reading the V1 was initially started with acetylene (I don't advise it) and then after it warmed up, switched to kerosene (or a mix). You may be having a problem getting your gasoline (dangerous) to vaporize.

[WebPilot]

 I found an image of the V1's intake. I know you have little time for a mod now, but notice how 'clean' it is to incoming flow of air.

[WebPilot]

 

 Two low pressure centrifugal blowers connected in series delivering a maxi-
 mum flow of 3 pounds/second of air were used for starting and for simulating
 ram conditions up to a velocity of about 200 feet per second.

  ...
 

 The heavier reeds, in general, showed a longer life than thinner reeds
 although operation of the jet was more difficult to start and resonance of
 the jet was more easily upset when using heavy reeds than with the lighter
 reeds.

  ... 
 

2. Heavier reeds showed a longer life than thinner reeds, and annealed
 spring steel (or soft steel) was superior to spring steel for longevity,
 as the main causes of failure appeared to be impact and bending rather
 than heat. Methods for reducing the shock of impact should be investi-
 gated in order to increase reed life.

 I don't think you should wait for another spring steel order to arrive.

 Use whatever steel you can find of the appropriate thickness or less ... and/or find
 2 low pressure centrifugal blowers of adequate capacity you can 'hook up' end to end.

[erik]

Thanks, that was interesting! source?

[Kool]

Here's some interesting stuff

For more go to this topic: ''Plans/Documents for Argus AS014 Style Engine'' viewtopic.php?f=2&t=5208

Here are some very interesting links of a 22 inch diameter valved pulsejet with dimensions of it, which i just found.

Performance test:
http://naca.central.cranfield.ac.uk/rep ... -e-269.pdf

Neoprene-coated vs normal coated valve test
http://naca.central.cranfield.ac.uk/rep ... -e-270.pdf

[PyroJoe]

Hi Erik,
It looks pretty good to me, the intake matches the overall length fairly well. If all else fails, may want to try removing the second set of venturi behind the valves (looks like they are bolted in).

The CC is just slightly short on Helmholtz volume, which requires a little more starting air&fuel flow.

If it were me, I would go with thinner valves in the 4 center ports (pictured) and make sure the other "thick" valves shut completely.

Sounds like it is close to running, hope she fires up soon for you.

-

[PyroJoe]

The intake side of the valve head may be reducing the effective intake area. If the intake ports edges on the upstream side are 90 degrees, this could hinder flow.

[Eric]

With fuel injected into the intake you'll get better valve life than direct injection, from a bit of cooling. If you mix in 10% methanol with the gas you'll get it downright cold.

It doesnt need to be as streamlined as the argus, because hopefully you kick will not be going anywhere near as fast as the argus.

The intake will flow more than enough air, once you have the right valve thickness it would actually be somewhat difficult to get the engine to shut off by blocking the intake with your hands, just from the airflow between your fingers, if it were a venturi intake, it would be more critical.

From the video it definitely sounds labored, like the valves are barely opening enough for it to run at a low throttle level.

Thinner valves will let it sustain easier, and run at a much lower minimum throttle.