Dynamics of the Blade Channel of an Inducer Under Cavitation-Induced Instabilities

Angelo Pasini,Ruzbeh Hadavandi,Dario Valentini,Giovanni Pace,Luca D'Agostino

doi:10.1115/1.4041728

Angelo Pasini, Ruzbeh Hadavandi + Show 3 more

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https://doi.org/10.1115/1.4041728

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Abstract

A high-head three-bladed inducer has been equipped with pressure taps on the hub along the blade channels with the aim of more closely investigating the dynamics of cavitation-induced instabilities developing in the impeller flow. Spectral analysis of the pressure signals obtained from two sets of transducers mounted both in the stationary and rotating frames has allowed to characterize the nature, intensity, and interactions of the main flow instabilities detected in the experiments: subsynchronous rotating cavitation (RC), cavitation surge (CS), and a high-order axial surge oscillation. A dynamic model of the unsteady flow in the blade channels has been developed based on experimental data and on suitable descriptions of the mean flow and the oscillations of the cavitating volume. The model has been used for estimating at the inducer operating conditions of interest the intensity of the flow oscillations associated with the occurrence of the CS mode generated by RC in the inducer inlet.

Highlights

Liquid-fed rocket engines still play a crucial role in primary space propulsion systems
The experimental data are arranged in such a way that the resulting characteristic surface can be used both for assessing the cavitating performance and for estimating the gradient of the head coefficient in its main independent variables
The rotating cavitation detected in the RAPDUD inducer for a wide range of flow coefficient has been identified in the stationary frame as a sub-synchronous one lobe corotating instability and in the rotating frame as a subsynchronous one lobe counter-rotating instability at a frequency shifted by the rotating speed

Summary

Introduction

Liquid-fed rocket engines still play a crucial role in primary space propulsion systems In these applications propellant feed turbopumps are one of the most important components, whose design and operation are critical for the success of the mission. Modern turbopumps need to be high power density, dynamically stable machines capable of meeting the extremely demanding suction, pumping and reliability requirements of modern Space Transportation Systems. The attainment of such high power/weight ratios is invariably obtained by running the impeller at the maximum allowable speed and lower shaft torque. The rotating cavitation in combination with the corresponding cavitation surge usually excited by the azimuthal instability are the most dangerous cavitation induced instabilities [14] for the introduction of both unsteady rotordynamic forces and significant flow oscillations that can couple with either the rotordynamic of the impeller or the dynamics of the combustion chamber

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