Numerical Model to Predict Unsteady Cavitating Flow Behavior in Inducer Blade Cascades

R Fortes-Patella,O Coutier-Delgosha,J Perrin,J L Reboud

doi:10.1115/1.2409320

Abstract

Abstract The cavitation behavior of a four-blade rocket engine turbopump inducer is simulated. A two-dimensional numerical model of unsteady cavitation was applied to a blade cascade drawn from an inducer geometry. The physical model is based on a homogeneous approach of cavitation, coupled with a barotropic state law for the liquid/vapor mixture. The numerical resolution uses a pressure-correction method derived from the SIMPLE algorithm and a finite volume discretization. Unsteady behavior of sheet cavities attached to the blade suction side depends on the flow rate and cavitation number. Two different unstable configurations of cavitation are identified. The mechanisms that are responsible for these unstable behaviors are discussed, and the stress fluctuations induced on the blade by cavitation instabilities are estimated.

Highlights

To achieve operation at high rotational speed and low inlet pressure, rocket engine turbopumps are generally equipped with an axial inducer stage
Cavitation develops on the suction side of the blades and at inducer periphery near the tip
When pressure is decreased from cavitation inception, vapor develops more and more and, leads to the inducer performance breakdownFig. 1͒

Summary

Introduction

To achieve operation at high rotational speed and low inlet pressure, rocket engine turbopumps are generally equipped with an axial inducer stage. Under such operating conditions, cavitation develops on the suction side of the blades and at inducer periphery near the tip. A steady and balanced flow pattern with one short attached cavity on each blade is observed from flow visualizationsFig. 2͑1͒͒. Over the last few years, numerical models have been developed to predict the cavitation instability in inducers5͔ These models are based on stability analyses and linear approach, taking into account the total flow-rate variations through a cavitating bladeto-blade channel6–9͔, or calculating the flow around attached cavities10–12͔. In spite of the progress of CFD, 3D unsteady calculations in inducer geometries are very time consuming and 2D approach is still interestingeven if it cannot represent completely the original three-dimensional case

Physical and Numerical Model

Results

Conclusion