Insights Into the Flow Field and Performance of a Boundary Layer Pump

Abstract

A flow field analysis of a realistic, integrated, multidisk boundary layer pump as is necessary for investigating the reasons for typically quoted low efficiencies in such pumps is described. The study focuses on the three-dimensional RANS solutions of a water boundary layer pump model created to replicate a design by Morris, 1973, which consists of 170 disks and a volute channel. A baseline study is performed to investigate the rotor-only performance after which a volute alone is separately simulated to identify the performance and losses in each as separate systems. Thereafter, an integrated model is characterized across mass flow rates and rotational speeds. The flow fields of all three models are discussed and the results of the integrated model are compared to the experimental data. The results from the model with the rotor only confirm the typically made claim that the efficiency of the rotor in a boundary layer pump possesses relatively high values which in this case is ∼87% at the design point, reinforcing results from previous studies that the rotor assembly is not the cause of inefficiency. The volute on its own indicated a hydraulic efficiency of around 97%. However, the integrated model yielded a rotor efficiency of around 74\% and an overall pump efficiency of 51% at the design point, clearly outlining the fact that the effect of the volute integrated with the rotor is the reason for both the rotor and pump efficiency degradation. The reason for this drop in efficiency is discussed in detail by highlighting the change in the flow topologies. The insights into the flow field and the identification of the reason for inefficiencies using a separated component analysis approach provide directions for avenues in which design improvements would need to be attempted.