STABILITY OF PNEUMATIC and HYDRAULIC VALVES
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چکیده
There are three forces acting on the valve plate: the force of the escaping air Fv, the force of the steel spring Fs and the pneumatic damping force due to the pressure of the air in the dashpot Fd. Each of these forces varies with distance x. These interact with the valve mass and the pipeline dynamics to produce instability. Perturbations in the pressure travel along the pipe at the sonic velocity and are reflected from the volume as rarefactions (negative pressure). If the pipe length is resonant at a frequency near to the resonant frequency of the valve, they will interact. (Note that at closed ends such as a hydraulic pump, the pressure perturbations are reflected as positive pressure).
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