dynamic modeling of a strip valve

Moderator: Mike Everman

Post Reply
WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Tue Dec 09, 2008 2:07 pm

All fourier analyses done analytically, are a bit taxing.

continuing ...

Here is a display of how well the reconstructed waveform fits the original function. One virtually overlaps the other.

Image
Image

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Wed Dec 10, 2008 1:27 am

Image

We interrupt the present train of thought in this thread, for some important news!

Grim has designed and built a pulse jet, dubbed the EVG 043, which incorporates my Valve Glide™ criterion. He has written,
This one has the valves tuned to dfr 0.43 ,

The photo is the valves after two, approx 1 min runs, there is NO fracture damage as was observed in previous runs with other ratios , In fact the valves are in perfect condition,
Here is a picture of those valves after the runs.

Look carefully, ... those are valves, not cut outs in the valve plate.
Image

They do look pristine, do they not?

For more info, videos and basically a log of his progress, check out his thread, External Valve Grid.

Thanks again, G. !




Fact is stranger than fiction.
Image

Mike Everman
Posts: 4906
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: dynamic modeling of a strip valve

Post by Mike Everman » Wed Dec 10, 2008 1:50 am

Absolutely fantastic! Very nice work, applied science, confirmation, beautiful.
Mike
__________________________
Follow my technical science blog at: http://mikeeverman.com/
Get alerts for the above on twitter at: http://twitter.com/mikeeverman

Graham C. Williams
Posts: 571
Joined: Fri Oct 03, 2003 11:33 pm
Antipspambot question: 0
Location: England
Contact:

Re: dynamic modeling of a strip valve

Post by Graham C. Williams » Wed Dec 10, 2008 7:47 pm

Great bit of work Grim and Forrest.
Is a W shaped valve block in the offing?

Graham.
Dark days nurture new
light. Productions begin.
Now open your eyes.

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Wed Dec 10, 2008 9:24 pm

Absolutely fantastic! ...
I've never read that from you before, Mike. Thanks.

Just a 'bit of work', you say? YHNC

continuing ...

I want to return to p12, the pressure drop across the orifice. I wish to investigate the ramification(s) of my Valve Glide™ criterion there.

Image
Image

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Thu Dec 11, 2008 4:43 am

It took some work to get to this point ... and things are not looking well for the approximation.

Image
Image

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Fri Dec 12, 2008 2:42 am

I found that the pressures are extremely sensitive to the amplitude of the analytical function (it's non-linear, remember?) I am using to estimate them. IOW, I need a better estimate of 'a'.

I wrote a describing function for the particular solution in terms of the amplitude, a. This function had to meet two criteria:
  1. it had to 'end' at the end of the full cycle
  2. at the beginning and end of the cycle, it could not 'rise' above the y=0 axis. It had to form smooth fillets at either end of the cycle.
Graphically, I determined:

Image

The red and green curves are of interest, here.
Image

Irvine.J
Posts: 1063
Joined: Mon Jun 05, 2006 4:28 pm
Antipspambot question: 0
Location: Brisbane, Australia
Contact:

Re: dynamic modeling of a strip valve

Post by Irvine.J » Fri Dec 12, 2008 12:27 pm

For you Forrest, mike, grim, whoever... please read and enjoy.
Fascinating stuff, opens up new doors for my CFD work.

http://www.linflow.us/CADFEM05-Physics-FSI.pdf
James- Image KEEPING IT REAL SINCE 1982
http://pulseairdefence.com
[url=callto://project42labs]Image[/url]

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Fri Dec 12, 2008 4:19 pm

Thanks James. I found the paper interesting.

I considered the effect of the fluid interacting with the motion of the strip valve, a '2nd order one' and thus disregarded it. For our needs, this kept my model 'simple'. Grim's discovery appears to substantiate my assumption.

continuing ...

For this value of 'a', the requisite pressure estimates are now looking as they should.

Image
Image

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Fri Dec 12, 2008 8:04 pm

Atmospheric pressure is causing flow to enter the box, but noise is emanating from the box. Why?

The reasoning is similar to when you slurp your soup from a spoon. Flow (due to a pressure drop) is entering your mouth, but noise is directed to the people sitting around you. Some complain ... some do not.

I propose the following:
  1. this noise is caused by the pressure drop waveform and
  2. the spectral content of the pressure drop will show up in the wave file record at the front of the box.
Image
Image

GRIM
Posts: 474
Joined: Mon Jul 30, 2007 2:43 am
Antipspambot question: 0
Location: British living in Chile

Re: dynamic modeling of a strip valve

Post by GRIM » Fri Dec 12, 2008 9:53 pm

I have been sitting quietly at the back of the class here , a little lost ,
sometimes when you dont understand, it is best to wait a while before asking questions,

Eating soup will never be the same again ,

Fantastic ,

Good paper James , thanks,

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Sat Dec 13, 2008 5:25 am

I didn't forget you, G. Is it soup, yet?

I've done the Fourier analysis on the p12 waveform and now know it is composed of a DC level and a complete group of ω's; ω1, ω2, ω3, ω4, ω5, ω6, ... ω∞.

The reader should realize by now ωm equals m × ω1, m=1,2,3,4,5,6 ... ∞; each one is an integral multiple of the fundamental.

Image

A few notes concerning this colorful graphic:
  1. p12 is the waveform with which I started out,
  2. the rest of the waves of various colors are the 'spectral components' of p12, (I am showing the reader what they look like individually and have NOT added them together, yet)
  3. reconstruction is where I did add all the waves together to make p12, which is why p12 is covered up!
  4. notice how they all 'line up' in order to eventually make the big dip!
  5. I have only used the 1st six Fourier components and look how rapidly the sum converged to p12!
Remember, if you see the symbol, φ, or a reference to psi, it is my shortcut for dfr, or driving frequency ratio.

In the next graphic, I shall show how the reconstruction takes place by adding these waves together, one after the other.
Image

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Sat Dec 13, 2008 11:53 pm

Image

This shows the effect of adding another Fourier component during the reconstruction of the p12 waveform. After 5 terms, it is pretty close.

For the summation, ω6+ω5+ω4+ω3+ω2+ω1+DC, see the previous graphic - it and p12 almost overlap each other.
Image

Mike Everman
Posts: 4906
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: dynamic modeling of a strip valve

Post by Mike Everman » Sun Dec 14, 2008 3:26 am

Still watching with interest, Forrest!
Would you please look at:
viewtopic.php?f=3&t=5109
I'm hoping you can make a recommendation for which way to take the natural frequency of the valve?
Mike
__________________________
Follow my technical science blog at: http://mikeeverman.com/
Get alerts for the above on twitter at: http://twitter.com/mikeeverman

WebPilot
Posts: 3716
Joined: Tue Dec 07, 2004 6:51 pm
Antipspambot question: 0
Location: 41d 1' N 80d 22' W

Re: dynamic modeling of a strip valve

Post by WebPilot » Sun Dec 14, 2008 7:58 pm

I've tweaked the above graphic in a minor way.

Mike, adjusting the dfr or φ won't help until you 'close' off the unimpeded flow with another valve. I've explained what I mean by this on your thread.

I hope to post a waveform analysis of a jet later today, here.
Image

Post Reply