Characterization of cavitation instabilities in rocket engine turbopump inducers
Name
971023062-MIT.pdf
Description
Full printable version
Size
48.26 MB
Format
Adobe PDF
Checksum (MD5)
cac1d17c93f3da16a334b937dae775b8
Author(s)
Wang, Vincent, S.M. Massachusetts Institute of Technology
Advisor(s)
Zoltán S. Spakovszky.
Date Issued
2016
Publisher
Massachusetts Institute of Technology
Abstract
Characterized by super-synchronous rotation of cavities around the periphery of rocket engine turbopump inducers, rotating cavitation is the primary cavitation instability considered in this thesis. A recently developed hypothesis for rotating cavitation onset is assessed through novel experimental analysis and a previously developed body force modeling approach using the MIT inducer, representative of the design of the Space Shuttle main engine low-pressure oxidizer pump inducer. A previously developed temporal and spatial Fourier decomposition, known as Traveling Wave Energy (TWE) analysis, of experimental unsteady inlet pressure measurements of the cavitating MIT inducer is demonstrated. TWE analysis offers several advantages over the current experimental analysis methods, resolving frequency, spatial mode shapes, and rotation direction of cavitation phenomena. Cut-on/cut-off behavior between rotating cavitation and alternate blade cavitation is observed, supporting the hypothesis that alternate blade cavitation is a necessary precursor to rotating cavitation onset. TWE is adapted for use on high speed borescope video data taken in the same experimental campaign. The frequency content extracted is qualitatively correlated with the results from the pressure data, establishing TWE as a viable tool for quantitative analysis of optical data. The video TWE results indicate that cavitation instability signatures are uniform in the radial direction, suggesting that a pressure transducer array can be established as the primary detection method for rotating cavitation and thereby simplifying test setups. A body force based modeling approach typically used for aero-engine compressor stability prediction is assessed for use in predicting rotating cavitation. A previously developed inducer-specific body force model formulation is validated in a representative compressor geometry, capturing global performance across the characteristic within 7%. However, the model exhibits convergence issues when applied to the inducer, hypothesized to be due to sensitivity in the inducer's loss characteristics. The investigation suggests the low flow coefficient design of the inducer drives the loss sensitivity and is the root cause behind the model's convergence issues. The results indicate the body force model is valid for the higher flow coefficient designs and lower stagger angles typically found in aero-engine compressors and fans. Suggestions for desensitizing the model for the inducer as well as further diagnostics defining the limiting geometry case for body force modeling are made.
Description
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 135-138).
Subjects
Aeronautics and Astronautics.
MIT Department
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
Terms of Use
MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.
Persistent DSpace Link
