The effect of gas compressibility on the effective flow area was studied by theory and experiment. The regression analysis method was used to fit the experimental data

and compared the degree of the coincidence between different theoretical models and experimental data. Results showed that the pressure of gas compressibility can be neglected when the gas pressure ratio was less than 1.081. When the pressure ratio was greater than 1.081

the fitting curve of the compressible gas theory model was consistent with the experimental data

and the value of effective flow area was stable at different pressure ratios. Fitting curves of the incompressible flow theory model deviated from the experimental data. The value of the effective flow area changed with different pressure ratios.