A 3-D Transient CFD Model of a Reciprocating Piston Compressor with Dynamic Port Flip Valves

In this paper a full transient 3-D CFD model of a complete single piston compressor system along with dynamic inlet and outlet port flip valves is presented. The model includes the motion of the cam driven piston, and also predicts the motion of the dynamic flip valves. All activities related to model creation, simulation and postprocessing were performed within the simulation software Simerics–PD (also known as PumpLinx). The mesh creation and mesh motion for the piston chamber and the flip valve volumes were performed using meshing algorithms implemented within the simulation software. In addition, a novel mesh motion algorithm was implemented to enable a fully coupled simulation of the inlet port flip valve and the piston surface: which have intersecting swept volumes and may interfere during the operation of the compressor. The entire simulation was performed in a fully coupled manner in which the motion of the valves is calculated within Simerics–PD during the transient CFD simulation. This is achieved by a Fluid Structure Interaction (FSI) methodology where the pressure distribution acting on the valve is used to calculate the valve motion using a robust ordinary differential equation (ODE) solver. Important input parameters of the rotational dynamics (such as torsion constant) of the flip valve were calculated from the beam bending theory. In addition a Full Closure model for flip valves implemented within Simerics–PD ensures that there is no leakage through the valves when they are in the fully closed position, which are essential for accurate compressor simulation. In the present work, detailed descriptions are provided of the model creation and simulation methodology for an industrial single piston compressor system. The model creation was performed on the real world geometry without simplifications and real-gas fluid properties were used for the simulation. The fully coupled 3-D transient CFD simulation of the piston compressor and the flip valves is shown to have excellent simulation speed and several relevant results are presented. The model set-up and performance of the simulation are demonstrated to be robust and user friendly and the algorithms developed can be readily applied to single piston compressor systems with dynamic port valves.