Influence of the Displacement Profile on the Performance and Mechanical Stresses of an Axial Piston Compressor for Refrigeration Applications

Axial piston compressors are commonly equipped with rotating disk plates that make the pistons following a sinusoidal displacement. The variation of the plate angle leads to stroke increments without changing the displacement profile. The axial piston architecture allows one to make piston displacement profiles that are different from a sinusoidal one by using rotating disk with a shaped circumferential profile. In this work, a detailed analysis on the thermodynamic cycle of compressors with different disk geometries was carried out. A lumped parameter numerical model of a compressor for refrigeration application was developed. The compressor performance (i.e. indicated power, compressed mass of gas and specific power) was estimated by imposing piston displacement profiles that are different from the sinusoidal one. The influence on the cycle COP in which the compressor runs was evaluated for each analysis. For each profile, the study of the forces acting on the rotating plate was also investigated. A sensitivity analysis allowed the definition of a profile design that guarantees the optimization of both the thermodynamic cycle and the mechanical stresses.