New Iterative Scheme in Computer Simulation of Positive Displacement Compressors Considering the Effect of Gas Pulsations

Abstract

In a typical computer simulation of positive displacement compressors, the mathematical equations that model the compressor process are integrated in the time domain starting from a set of assumed initial conditions. The simulation has to be continued for enough iterations for the results to converge. The pulsation pressures in the suction and discharge cavities, which are assumed constant in the beginning, are calculated at the end of each iteration and used for the calculation in the next iteration. However, when this scheme is actually applied to fractional horsepower reciprocating compressors, it is found that the suction cavity pressure does not converge well, while all other parts of the results converge relatively quickly. The cause of this problem is explained qualitatively by the characteristics of the simulation method. A unique iteration scheme for the simulation was developed in this work to overcome this problem. In the new scheme, the updating rate of the pulsation pressures is adjusted based on the convergence trend of the previous iterations. A practical example is used to demonstrate the convergence of the simulation results and practicality of the simulation program.