Critical Inlet Pressure Prediction for Inline Piston Pumps Using Multiphase Computational Fluid Dynamics Modelling

Inline piston pumps are extensively used in aircraft hydraulic systems. They can be found in engine-driven large-sized hydraulic pumps and zonal electric motor-driven small to medium sized pumps. Inline piston pumps are positive displacement pumps with variable volumetric flow controls. Positive displacement pumps can provide a variable flow rate over a wide range of suction pressures. Aircraft fly at high altitudes, and therefore these pumps have to work in extreme conditions such as low atmospheric pressure, low temperature. At low inlet pressures, the pump is highly susceptible to cavitation, i.e., insufficient filling capacity. The pressure below which pump flow rate drops drastically is known as critical inlet pressure. Extensive research has been carried out to study cavitation in inline piston pumps. One-dimensional (1D) and three-dimensional (3D) single fluid Computational Fluid Dynamics (CFD) simulations have been in use; however, such models are valid under various simplifying assumptions. Such methods cannot be directly used to evaluate the performance under severe conditions such as very low pressure and temperature. Simplified simulations can also not be used in the case of complex inline piston pump assemblies that have a centrifugal boost stage. Testing is a costly option to evaluate the cavitation performance of inline piston pumps. A validated 3D CFD multiphase methodology is therefore needed to be developed to predict cavitation-affected pump performance. The present text describes a methodology developed to address this need. It is utilized to optimize pump designs.