Research on dynamic leakage flow in the labyrinth seal of a labyrinth piston compressor

Abstract

To study the labyrinth leakage flow characteristics of a labyrinth piston compressor, firstly, a transient flow model was built to simulate the fluid flow through labyrinth seals. The dynamic pressures in the labyrinth chambers and the leakage flow rate were obtained by solving the transient flow model. Then, an experimental rig based on a labyrinth piston air compressor with rotational speed of 400 to 900 rpm, and discharge pressure of 0.2 to 0.5 MPa was built to validate the simulation results. In the experiments, dynamic pressures in the cylinder and in the labyrinth chambers were measured at different discharge pressures and different rotational speeds. The simulation results of pressures showed a good agreement with the experimental ones with the maximum relative error of 20%. Later, the transient flow model was used to study the dynamic pressure distribution and leakage flow rate through the labyrinth chambers. The results show that the pressure drop across each labyrinth chamber increases along the leakage flow path from the compression chamber side to the environment side. The pressure drop of the last third chambers accounts for 50% of the total pressure drop of all the chambers. The leakage flow rate increases quickly with the increase of the discharge pressure at low rotational speed. At the speed of 500 rpm, the leakage mass flow doubles when discharge pressure increases from 0.2 MPa to 0.5 MPa. However the growth rate slows down at a high speed of 800 rpm. The leakage characteristics indicate that the labyrinth piston compressor should work at a high rotational speed and a low discharge pressure.