Unsteady boundary layer and numerical modeling of transient heat transfer with application in wave rotors
Abstract
Unsteady flow devices offer potential performance improvement and unique features compared with their steady state counterparts. As a member in the family of unsteady flow devices, wave rotors represent a promising technology for use in gas turbine engines with significant fuel efficiency and emissions reduction benefits. Unlike conventional combustors that have a liner to protect the pressure vessel, the wave rotor combustor relies on transient cold and hot flow to control thermal loading. An accurate knowledge of the time-varying thermal response is thus necessary in the design and transient operation of wave rotors. Numerical methods are developed in this research with the capability of predicting the transient thermal boundary layer response for typical unsteady wave rotor channel flow and thermal conditions. Based on boundary layer theory, the two-dimensional compressible Reynolds-averaged boundary-layer equations are transformed into incompressible form through the Dorodnitsyn-Howarth transformation and solved with similarity transformations. Both laminar and turbulent flow conditions are considered. The developed methodology and computer codes are verified by comparing with previous transient boundary layer heat transfer studies. Wave rotor transient heat transfer phenomena are investigated including the transient thermal boundary layer variation due to a moving fluid of varying temperature, and the unsteady boundary layer formed by a centered expansion wave. The derived results regarding the transient time scale, the predicted magnitude and direction change of the heat transfer rate during the unsteady process provide valuable tools to improve wave rotor heat transfer predictions.
Degree
Ph.D.
Advisors
Nalim, Purdue University.
Subject Area
Mechanical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.