Design and Numerical Analysis of a High Head Inducer for a Rocket Pump

The inducer is a special type of axial pump, which is especially designed to improve suction performance of a centrifugal pump. The usage of inducers allows designers to choose higher operating speeds for a typical centrifugal pump, thereby reducing the overall weight of the system. As far as rocket engine pumps are concerned, this aspect is of prime importance and most of the rocket engine pumps are equipped with inducers upstream of centrifugal impellers. Inducers are broadly classified into low head and high head inducer based on the head coefficient (ψ). This paper focuses on hydrodynamic design of a high head inducer having head coefficient (ψ) > 0.35. A mean line design is done initially based on the recommended design criteria available from literature, followed by a 3D CFD analysis to further optimize and fine tune the design. An accurate numerical model capable of predicting the performance of an axial inducer is of particular interest to rocket engineers in order to rapidly provide indications for the preliminary design of the machine. Commercial CFD solver ANSYS CFX is used for the numerical studies and meshing was done in TurboGrid. Grid independence study was done to ensure correctness of the mesh. The head rise and efficiency characteristics over a broad range of flow coefficients were determined. NPSH requirements for the nominal flow rate were also determined through CFD using Rayleigh–Plesset cavitation model. Among various design parameters, number of blades, radial tip clearance, and wrap angle were found to have a major influence on the performance of the inducer. Based on the results of the CFD analysis, initial design was optimized and found to meet the design requirements.