Quantification of Combustion Inhomogeneity Based on Sparsely Arranged Thermocouples at the Outlet of Multistage Turbines

Abstract The localized temperature anomalies induced by combustion, manifested as circumferential or radial temperature inhomogeneity, are detrimental to the performance and reliability of the turbine cascades. Temperature inhomogeneities within the gas turbine are typically monitored by thermocouples installed at the turbine outlet, which cannot directly reflect the operating conditions of the combustion chambers and high-pressure turbines because of the migration and mixing of temperature inhomogeneities. Based on the effective prediction method for the azimuthal migration of temperature inhomogeneity, the temperature reconstruction using the multi-Gaussian function approximation is developed. Dual-objective optimization is adopted for solving the system of nonlinear equations in reconstruction. Reconstruction is applied to data from cold streak migration experiments on a multistage turbine. Equal-span temperature profiles in different streamwise planes within the turbine are reconstructed based on sparsely arranged thermocouples at the turbine outlet. In addition, the azimuthal migration of the hot/cold streaks and the variation of the temperature profiles with the streamwise direction are reproduced. Comparison of the reconstruction with full-annulus unsteady-state numerical simulations shows that the temperature inhomogeneities and asymmetries in the circumferential and radial directions are correctly captured. The robustness tests show that the reconstruction is sensitive to the parameter characterizing the azimuthal migration of the combustion inhomogeneities, while it is relatively insensitive to the thermocouple mounting positions and the parameters characterizing the temperature distributions.