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The paper investigates instable behavior of a poppet-type gas pressure relief valve operating at a big flow rate (more than 2 kg/s) under super critical pressure drop. Instability is experienced as noise and vibration and leads to severe damage of a seat and other elements. Significant and unsteady flow forces coupled with small inherent damping make it difficult to stabilize the system. In previous works, the analytical and experimental research was carried out to reveal the most essential factors influencing stability and dynamic properties of the valve. The impact of the pilot valve dynamics on the system behavior was studied for the purpose of obtaining required accuracy and stability in a wide range of flow rate. It was shown in some testing that unstable behavior of the main valve occurred when the pilot valve was stable. This paper considers inherent stability of the main valve in the gas flow. CFD software ANSYS FLUENT is employed to study the effect of the poppet geometry on aerodynamic lifting force and valve stability in axial and lateral direction. The results have been verified through comparison with experimental data.

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This paper presents research on effectiveness of P-control algorithm with a pressure as an output signal for an active vibration isolator using pneumatic bellow. Pressure pulsation inside the pneumatic element of the vibration isolator is studied in the frequency range covering its sub resonant and resonant frequencies. Spectral analysis is used to compare the response to harmonic excitation of active pneumatic vibration isolator and that for the case with active control disabled. The minimal bore size of the control valve is defined to achieve a double advantage of the active system over the passive one in the frequency range including the vibration isolator resonant frequency. It is shown that to obtain this result, a fast-acting spool valve should be used. Moreover, at a low frequency range of a Hertz-level excitation signal, P-control algorithm demonstrates three times decrease of pressure pulsation amplitude. The analysis of experimental results shows that P-control algorithm with pressure output and the high response spool valve with the bore size as large as possible can be used for active pneumatic vibration isolator at the low frequency range.