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Short question topic

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Re: Short question topic

Unread postAuthor: hectmarr » Thu May 09, 2019 10:00 am

I do not know if I understand what you explain to me ...
You mean that the area "B" must be 4 times larger than the area "A", and assuming a mixing pressure in the combustion chamber of 10 bar, the pressure on the "B" side of the piston, debris to be 30 bar ?, so that the piston opens at approximately the peak pressure of explosion, and not before ... :roll:
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Re: Short question topic

Unread postAuthor: jackssmirkingrevenge » Thu May 09, 2019 10:30 am

More or less, here are the numbers in a less imperial context:

The pressure on area A is trying to open the piston. The pressure on area B is trying to keep the piston closed.

Let's say that A is 1cm and B is 1.5cm and you have 10 bar pre-mix in the combustion chamber. The force trying to open the piston is 8kg, while the force keeping it closed is 18kg. This means that it will open when the force on A is 18kg, equivalent to about 22 bar in the chamber in our example. Since a 10 bar pre-mix can be expected to generate upwards of 70 bar, this means a lot of the energy will be wasted.

In order for the piston to open at 70 bar chamber pressure, the pressure on B in this example needs to be 31 bar.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Short question topic

Unread postAuthor: hectmarr » Thu May 09, 2019 10:37 am

OK understood.
It will be a bit annoying to have to compress at two different pressures, because I will need to include a pressure regulator at the outlet of the air pump, say 10 bar to pass through the doser and 30 bar of air only, to the rear of the piston.
Muchas gracias por la explicación.
 
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Re: Short question topic

Unread postAuthor: jackssmirkingrevenge » Thu May 09, 2019 11:02 am

You can always use a bigger piston, there will be more dead space but I think the bigger pop-off pressure will more than compensate for this...
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Short question topic

Unread postAuthor: wyz2285 » Wed May 15, 2019 3:08 am

Temperature raised considerably here so manually pump and keep the Yong Heng cool is getting tiresome. I'm ready to order the booster pump. Just one last question, how high is the maintenance of it? If I had put enough effort (which I would be very uncomfortable with) like open all the parts and clean every few uses with the Yong Heng I suppose it could have lived longer so, is the booster pump same thing? Or I have a relatively trouble free use?
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Re: Short question topic

Unread postAuthor: hectmarr » Wed Jun 19, 2019 10:11 am

I have thought about building a 3-way piston pressure regulator. I have conceived it in this way, as it is in the drawing, which is simple to build, what I can do. The maximum inlet pressure is about 50 bar, and should be able to regulate about 10 bar at the exit. Somebody's grip, about this? :roll:
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Re: Short question topic

Unread postAuthor: jackssmirkingrevenge » Sat Jun 22, 2019 4:30 am

Looks good, my only gripe would be the o-rings going past ports that would tend to tear them up under pressure.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Short question topic

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Re: Short question topic

Unread postAuthor: hectmarr » Sat Jun 22, 2019 9:59 am

jackssmirkingrevenge wrote:Looks good, my only gripe would be the o-rings going past ports that would tend to tear them up under pressure.

Good point to take into consideration :roll: I thought to make the holes of entrance and exit of 1 mm, and leave them without sharp edge, using an o`ring of at least 2.5 mm, well embedded in the body of the piston. It's like the solenoid valve that I have, more or less. Here is in this video https://youtu.be/ZuSvDV9DvWg how is inside. I suppose the o`rings should last a reasonable time, before having to replace them.
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Re: Short question topic

Unread postAuthor: D_Hall » Sat Jun 22, 2019 11:32 am

jackssmirkingrevenge wrote:Looks good, my only gripe would be the o-rings going past ports that would tend to tear them up under pressure.


FWIW... Many moons ago I designed a valve with a similar O-ring and port issue. I solved it by enlarging the internal diameter of the valve body start/ending about 1 O-ring diameter in front of and behind the side port. The enlargement was tapered, of course. The idea was that the valve actually broke seal before the piston passed the side port and resealed afterwards. Thus, in the region of interest the O-ring was not under stress as it passed the ports and in truth never actually touched the sharp edges of the port.

Worked great.
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Re: Short question topic

Unread postAuthor: jrrdw » Sun Jun 23, 2019 4:30 am

hectmarr wrote: I suppose the o`rings should last a reasonable time, before having to replace them.
A little lube goes a long way! :shock:

D_Hall wrote:FWIW... Many moons ago I designed a valve with a similar O-ring and port issue. I solved it by enlarging the internal diameter of the valve body start/ending about 1 O-ring diameter in front of and behind the side port. The enlargement was tapered, of course. The idea was that the valve actually broke seal before the piston passed the side port and resealed afterwards. Thus, in the region of interest the O-ring was not under stress as it passed the ports and in truth never actually touched the sharp edges of the port.

Worked great.


Soooo, you're the one who came up with chamfering the edges. :P
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Re: Short question topic

Unread postAuthor: hectmarr » Sun Jun 23, 2019 10:37 am

A little lube goes a long way! :shock:

I imagine it will be like that. I use silicone lubricant, it seems to work properly.
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Re: Short question topic

Unread postAuthor: hectmarr » Wed Jun 26, 2019 8:33 am

I'm going to build in this way, simpler :roll:
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Re: Short question topic

Unread postAuthor: hectmarr » Tue Aug 13, 2019 10:27 pm

Does anyone have information on the pressure needed to cause the autoignition temperature of a stoichiometric mixture of butane - air? :bom:
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Re: Short question topic

Unread postAuthor: mrfoo » Wed Aug 14, 2019 10:55 am

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Re: Short question topic

Unread postAuthor: hectmarr » Wed Aug 14, 2019 2:26 pm

mrfoo wrote:https://www.icheme.org/media/10183/xvi-paper-38.pdf

Somewhere around 1100°K

Good info, I am reading. Thank you.
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