Aerodynamic Response of Turbomachinery Blade Rows to Convecting Density Wakes

Abstract

The aim of the current research has been to contribute to the "aerodynamic forcing function" aspect of the high cycle fatigue problem. In this regard density wakes were identified as a potential new source of turbomachinery blade vibration. In order to characterize the density wake induced force and moment fluctuations a two-dimensional computational study was conducted to simulate the passage of density wakes through a cascade blade row. Both inviscid incompressible flows and viscous compressible flows M sub infinity=0.15 to M sub infinity=0.87 and Reynolds number Re(c,U sub infinity) approximately equal 700,000) were considered. The inviscid flow simulations show a pair of counterrotating vortices in the blade passage and a flux of density wake fluid to the blade suction/pressure surface as low/high density wakes convect through the blade row. This fluid flux is found to be the key mechanism which affects the blade static pressure distribution and hence the blade force and moment response. The viscous flow simulations have uncovered additional mechanisms for blade force and moment fluctuations: (1) periodic vortex shedding at the blade trailing edge, (2) convecting separation bubbles on the blade suction surface (due to the density wake - blade boundary layer interaction) and (3) axial deflection of the blade passage shock wave position (due to the density wake - shock wave interaction). Simple functional relationships have been derived to quantify the force and moment fluctuations for each flow simulation. A simple cascade flow model has also been developed to determine parametric trends in the blade force and moment fluctuations with varying density wake properties and compressor geometries.

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Document Details

Document Type
Technical Report
Publication Date
Jan 03, 1999
Accession Number
ADA363039

Entities

People

  • B. Ramer
  • Choon S. Tan
  • Eugene E. Covert
  • H. S. Wijesinghe
  • T. Wilson

Organizations

  • Massachusetts Institute of Technology

Tags

Communities of Interest

  • Energy and Power Technologies
  • Ground and Sea Platforms
  • Space
  • Weapons Technologies

DTIC Thesaurus Topics

  • Boundary Layer
  • Compressible Flow
  • Computational Fluid Dynamics
  • Flow Visualization
  • Fluid Dynamics
  • Fluid Flow
  • Incompressible Flow
  • Inviscid Flow
  • Pressure Distribution
  • Reynolds Number
  • Shock Waves
  • Static Pressure
  • Turbomachinery
  • Two Dimensional
  • Ultrasounds
  • Viscous Flow
  • Vortex Shedding

Fields of Study

  • Physics

Readers

  • Aerodynamics.
  • Fluid Dynamics.