Approximating Gas Turbine Combustor Exit Temperature Distribution Factors Using Spatially Under-Sampled Measurements

Abstract

In gas turbine engines, the temperature field at the exit plane of the combustor is highly unsteady and complex, with large radial and circumferential variations. The circumferential temperature variations (hot-streaks) are caused by the discrete nature of fuel and dilution air jets, and combustor lining coolant flow results in a strong radial temperature gradient. Two widely adopted parameters include the radial temperature distribution factor (RTDF) and the overall temperature distribution factor (OTDF) to quantify combustor exit temperature nonuniformity. The state-of-the-art approach to characterizing the combustor exit temperature nonuniformity is to carry out an extensive traverse along the circumferential direction at a spatial resolution of two to three degrees. With hundreds of measurements in place, the combustor OTDF and RTDF can be obtained. Though the approach is practical, this involves the design of complex traverse mechanisms and can be costly. To address this challenge, this paper presents a novel method for predicting combustor exit TDFs using much sparser measurements. The approach's effectiveness was examined using three engine representative combustor exit temperature measurements covering a single-burner, double-burner, and entire annulus. In all cases, the hot-streaks-related features are well resolved in the reconstructed temperature field, and the multiwavelet approximation method yields almost identical RTDF to experiment with majority variations of less than 1.0% using sparse measurements. In addition, the method's robustness was examined, and considerations for the implementation of the method were provided.