Simulating the dynamic behavior of a Triple Screw Pump without CFD

Abstract

Pressure pulsations in screw pumps lead to noise, vibration and system strain. In order to increase the amount of dissolved and undissolved gas in the fluid while keeping noise, vibration and stress on the system at an acceptable level, the pump behavior must be understood in detail. Physical tests and CFD are common methods in modern pump design. However, both methods are not able to assess numerous design changes and machine integration challenges quickly. The system simulation approach tackles both challenges efficiently and allows to evaluate machine dynamics. Siemens Simcenter Amesim has been used to model a Leistritz Flexcore 45/90 triple screw pump. The model, containing components of a multi-physics library, calculates the movement of the chambers along the spindle package length by having virtual chambers alternately change their volume depending on the spindle rotation. Fluid properties, pressure dependent aeration and inertia effects are considered. The generation and displacement of the chamber volumes cause the suction and discharge of the fluid. The overlay of the single chambers results in the total volume flow of the pump. Internal leakage between the chambers is also considered, turning the model into a realistic digital twin of the screw pump. For the overall model and each individual chamber, the model gives volume flow rates, discharge pressure, pressure pulsation and internal pressure evolution. The air content has a significant influence on the pressure pulsations. To verify the model, measurements of operating points on a real pump have been carried out. Simulated volume flows and pressure pulsation show very good agreement with measurements. This new method for modeling screw pumps dramatically increases the speed of simulating pump behavior and opens the possibility of integrating the models into higher-level systems. The reproduction of dynamic effects and system responses for control tasks is also possible. The existing model can be extended towards further physics like friction modeling or additional system components like an electrical power unit.