CFD Evaluation of Pressure Losses on Reciprocating Compressor Components

Abstract: Reciprocating compressor efficiency is driven by the pressure losses generated at suction and discharge. While the valves are the major contributors to these losses, a key role is played by other components along the cylinder suction and discharge paths. CFD simulations of complete systems are a viable solution for prediction of total pressure losses. On the other hand, these simulations require noticeable man work for set-up; moreover, the results are dependent on the specific geometric and fluid-dynamic parameters chosen for the calculation. Recent studies have suggested that an approach based on superposition of effects is suitable for the prediction of pressure losses caused by the different components. Valve geometries are replaced by equivalent porous regions, thus providing a great simplification of the model and enhancing productivity due to the possibility of evaluating different configurations without having to re-construct and re-mesh the geometries. In this paper, the same approach is presented and applied to one specific, real-world case. Total pressure losses are computed by a steady-state CFD simulation of a complete configuration of cylinder equipped with 16 valves and other components (cylinder head, liner, valve unloaders, cages etc.), at suction and discharge condition. Calculation of the P-V cycle inside the cylinder is performed taking into account the loss coefficients obtained at previous step. Comparison with measured data is provided in order to support the validity of this approach.