Huiming Zou*, Liqin Zhang, Guohong Peng and Changqing Tian
The Journal of Mechanical Science and Technology, vol. 25, no. 8, pp.1885-1892, 2011

Abstract : The dual-cylinder opposed linear compressor (DOLC) contains a couple of symmetrical gas loads on the two sides of the movement components. Because the gas loads are symmetrical, the balanced position of movement components will not be offset by gas force during the operating process, and piston displacement can be detected and controlled more easily. Based on the kinetics and thermodynamics theory, the non-linear gas load of the DOLC was linearized by the Fourier method. The relationship between the supply voltage and displacement is presented. Through air compression experiments, the operation features of the DOLC with different syntonic spring groups were analyzed. The performance of the DOLC was considerably affected by work conditions and the stiffness of syntonic spring groups; the closer the work condition was to the sympathetic vibration, the higher the observed efficiency of the DOLC. A jump, hysteresis, and an unstable phenomenon in the process of voltage regulation occurred around sympathetic vibration conditions. In the process of increasing voltage on a certain discharge pressure condition, the displacement jump phenomenon occurred when the intrinsic frequency approacheds power frequency, causing the discharge pressure to drop synchronously. In the process of decreasing voltage on the lower discharge pressure condition, the displacement shrink phenomenon occurred when the intrinsic frequency approached power frequency. Because sympathetic vibration conditions changed with discharge pressures, a hysteresis district existed between the displacement jump point and shrink point. The DOLC worked unstably on the hysteresis district because the discharge pressure fluctuated between the two values. To make the DOLC work stably on higher efficiency, the intrinsic frequency should be configured to a slightly larger value than the power frequency by setting the syntonic spring groups and the mass of movement components to the ratings on the work conditions. Controlling the power frequency after is needed to adhere to the intrinsic frequency of the variable work conditions.

Keyword : Linear compressor; Dual-cylinder; Dynamics characteristics; Sympathetic vibration