A digital simulation method of the pressure pulsations in reciprocating compressor-piping systems. 1st report Calculation method.

Abstract

One method of analyzing pressure pulsations is to use an analog simulation which can consider the interaction between a compressor and the attached piping. Conventional digital pulsation analyses, in which suction/discharge gas flow is one-sidedly applied as a forcing function, do not consider the interaction effects. This paper describes new digital simulation methods which can account for a compressor-piping interaction. In these methods, non-return valves and the stroke of the valves of compressors are expressed by nonlinear damping and nonlinear stiffness respectively. The dynamic equation of the total system is constructed by assembling the characteristic equations of each element using the finite element method. This governing equation is integrated time historically using the Newmark-β method ; and then the flow rate and pressure variation are obtained. By using the above methods, the following three types of digital simulations were carried out for a compressor-piping model : (1) conventional digital simulation (2) new digital simulation equivalent to the analog simulation (3) new digital simulation including the valve dynamics. From these calculations, it is demonstrated that this present method has the same capability as the analog simulation. Furthermore, it is shown that this new method can deal with more detailed interactions by considering the valve dynamics, which is difficult to account for in the analog simulation.