Research on precise control of piston eccentricity by electromagnetic levitation in labyrinth piston compressor

Abstract

The piston in the Labyrinth piston compressor (LPC) usually runs eccentrically in the cylinder, which results in large internal leakage and low volumetric efficiency. An active electromagnetic control method based on the electromagnetic levitation theory was proposed in this paper to control the piston eccentricity, and a triple close-loop multi-factor coupled feedback control strategy composed of a current loop, a velocity loop, and a displacement loop was designed to realize the levitation control of the piston. The experimental research shows that there is serious piston eccentricity in the LPC, and the piston eccentricity is positively correlated with the increase of compressor pressure ratio and speed. By adopting the active electromagnetic control system proposed in this paper, the piston eccentricity is significantly reduced, and the maximum reduction is over 88%. Further research shows that the volume flow rate and volumetric efficiency of the LPC with control are maximum improved by about 45.6% and 44%, respectively. In conclusion, the piston eccentricity in the LPC could be effectively reduced by adopting the active electromagnetic control method proposed in this paper, thus improving its performance.