Kevin071586
Mechanical
- Jun 25, 2009
- 6
Hello everybody,
This is my first post here, but I am looking forward to contributing more in the future. I am a recently graduated Mechanical Engineering student and I'm presently working in the aerospace industry with a PRV that I'm trying to learn a little bit more about.
I'm trying to understand how to analyze what is going on with the pressures in the system at a given valve position. For a basic PRV, the cracking pressure can be estimated with a force balance using the opposing pressures and areas. However, once the valve begins to crack open there will be a rush of fluid through the orifice created that will change directions. The resulting change in momentum of the fluid is due to the poppet results in a equal and opposite closing force on the poppet.
If this force is tending to close the poppet, does it ever become important to analyze? The force must be small, or else the valve would just close right after opening and create some sort of valve chatter, I would imagine. Is there any literature on this that I could review?
The second part of my question relates to the pressure transients that exist in the system. When the valve is closed, the pressures on the opposite sites of the poppet are distinctly different. However, as soon as the valve is opened the two pressures are "connected." There must exist some pressure gradient from that flow. If the pressure gradient is large enough to affect the backside pressure on the poppet, it must have some impact on the distance the valve is actually open. Furthermore, there will be an additional pressure drop in the flow due to the orifice losses -- does this play a role in how far open the valve is? If so, how?
I don't understand how each of these factors contribute to the overall dynamics of the valve, and how to analyze it (i.e. Pressure Drop/Flow relationship). Does anybody know of a good book that talks about the analytical force/pressure analysis on a poppet?
Thanks,
Kevin
This is my first post here, but I am looking forward to contributing more in the future. I am a recently graduated Mechanical Engineering student and I'm presently working in the aerospace industry with a PRV that I'm trying to learn a little bit more about.
I'm trying to understand how to analyze what is going on with the pressures in the system at a given valve position. For a basic PRV, the cracking pressure can be estimated with a force balance using the opposing pressures and areas. However, once the valve begins to crack open there will be a rush of fluid through the orifice created that will change directions. The resulting change in momentum of the fluid is due to the poppet results in a equal and opposite closing force on the poppet.
If this force is tending to close the poppet, does it ever become important to analyze? The force must be small, or else the valve would just close right after opening and create some sort of valve chatter, I would imagine. Is there any literature on this that I could review?
The second part of my question relates to the pressure transients that exist in the system. When the valve is closed, the pressures on the opposite sites of the poppet are distinctly different. However, as soon as the valve is opened the two pressures are "connected." There must exist some pressure gradient from that flow. If the pressure gradient is large enough to affect the backside pressure on the poppet, it must have some impact on the distance the valve is actually open. Furthermore, there will be an additional pressure drop in the flow due to the orifice losses -- does this play a role in how far open the valve is? If so, how?
I don't understand how each of these factors contribute to the overall dynamics of the valve, and how to analyze it (i.e. Pressure Drop/Flow relationship). Does anybody know of a good book that talks about the analytical force/pressure analysis on a poppet?
Thanks,
Kevin
