Numerical simulation of CO2 piston compressor in transcritical compression cycle

Abstract

Based on theory of thermodynamics and kinetics, the mathematical model of crank connecting rod of a CO2 piston compressor was established and the stress deformations were employed by ANSYS finite element software. In the compression process, when the differential pressure is 4 and 5 MPa, the maximal displacement variation, stress variation, and strain variation are 18.79 μm, 12.8 MPa, and 0.28 × 10−3. When the differential pressure is 6 and 7 MPa, the maximal displacement variation, stress variation, and strain variation are 26.30 μm, 18.0 MPa, and 0.39 × 10−3. In the discharge process, when the differential pressure is 4 and 5 MPa, the maximal displacement variation, stress variation, and strain variation are 19.43 μm, 27.7 MPa, and 0.615 × 10−3. When the differential pressure is 6 and 7 MPa, the maximal displacement variation, stress variation, and strain variations are 27.20 μm, 48.4 MPa, and 1.08 × 10−3. No matter the compression process or the discharge process, the maximal displacement deformation, the maximal stress variation or the maximal strain variation are mainly concentrated in the small head of crank connecting rod, and small head is also more likely to damage. The higher differential pressure causes the crank connecting rod to product a bigger stress variation and displacement variation. Under the same conditions, the connecting rod in discharge process has a bigger displacement variation than the compression process, so the small head of crank connecting rod in discharge process is more easily to be broken. Some fundamental data were obtained for improving the efficiency of CO2 piston compressor and developing the products of CO2 refrigeration air condition and heat pumps. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1772–1783, 2016