Study on the heat transfer characteristics of turbine vanes under active modulation of gas turbine cooling air flow

Gas turbines are critical power equipment for national security and economic development. Turbine vanes operate at temperatures exceeding the thermal endurance limits of materials, relying on cooling air extracted from the compressor to maintain safe operation. Under partial load conditions, the temperatures of hot components fall below design values, resulting in excessive cooling air flow. Although studies and applications have indicated that actively modulating turbine cooling air flow can improve gas turbine efficiency at partial loads, the turbine vane heat transfer characteristics and modulation boundaries remain unclear. To fill this gap, this study develops a vane numerical model with complex cooling structures and a thermodynamic model of a three-shaft marine gas turbine, introducing a coolant pressure modulation coefficient to reflect the modulation of cooling air flow. Through co-simulations, the conjugate heat transfer method is used to analyze the heat transfer characteristics and modulable boundaries of the vane under various gas turbine load conditions for four modulation methods of coolant in two cavities: synchronous modulation, modulation of the front cavity only, modulation of the rear cavity only, and separate modulation for each cavity. Investigations show that when the coolant-to-mainstream pressure ratios in the vane front and rear cavities fall below 1.0154 and 0.9846, respectively, gas ingestion begins to occur in the film holes on the corresponding cavities. The maximum modulable cooling air flow volumes for the four modulation methods are calculated, and it is found that within the boundary without gas ingestion, the modulable cooling air flow volumes of the four methods are essentially consistent under different load conditions. Additionally, the variation patterns of parameters such as cooling efficiency, temperature non-uniformity, and vane kinetic efficiency are analyzed during the cooling air flow modulation process.