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research-article

Effects of wall heat loss on swirl-stabilized non-premixed flames in a model gas turbine combustor

[+] Author and Article Information
Huangwei Zhang

Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Republic of Singapore
huangwei.zhang@nus.edu.sg

1Corresponding author.

ASME doi:10.1115/1.4040516 History: Received February 25, 2018; Revised May 10, 2018

Abstract

Large eddy simulation with three-dimensional Conditional Moment Closure sub-grid model for combustion is applied to simulate a swirl-stabilized non-premixed methane flame with localized ex-tinction, with special focus on the effects of heat loss to the burner surface. The convective wall heat loss is modelled through introducing a source term in the conditionally filtered total enthalpy equation for the CMC cells adjacent to the wall. The mean heat flux is high on the middle surface of the bluff body, but relatively low near its edges. The turbulent heat flux based on the gradient of the resolved temperature is relatively low compared to the laminar counterpart, but increases with the turbulent intensity. The heat loss facilitates the occurrences of extinction and re-ignition for the CMC cells immediately adjacent to the wall, evidenced by comparing flame structures in the near-wall CMC cells. This can be directly linked to the increase of the mean conditional scalar dissipation near the wall in the heat loss case. Furthermore, the degree of local extinction near the bluff body measured by conditional reactedness at stoichiometry is intensified due to the wall heat loss. However, the results also show that there is negligible influence of wall heat loss on the probability density function of the lift-off height, demonstrating the dominance of aerodynamic effects on flame stabilisation. The results are in reasonable agreement with experimental measurements.

Copyright (c) 2018 by ASME
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