Research on active modulation of gas turbine cooling air flow

Abstract

Gas turbines are the core power equipment for efficient energy conversion and clean utilization. Their hot components operate in environments that largely exceed the heat resistance limit of materials, using cooling air to maintain operation, but the cooling air is often in excess at low engine loads. Therefore, this paper proposes the active modulation of turbine cooling air flow to improve their cycle efficiency by appropriately reducing the cooling air flow rate at low engine loads. Accordingly, a dynamic gas turbine model applicable for the active modulation of turbine cooling air flow is established, along with an analytical turbine vane cooling model considering air-film cooling and thermal barrier coating. For the first time, this paper distinguishes between the hot gas parameters on the pressure and suction surfaces of turbine blades. Additionally, a new concept of equivalent air-film coverage is proposed and optimized by genetic algorithms to make the model calculation results closer to actual temperature distribution. A cooling air active modulation system combining open-loop and closed-loop control is the first ever designed. Studies indicate that active coolant modulation can significantly improve gas turbine efficiency at partial loads. Finally, the possibility of active coolant modulation to suppress blade overheating and enhance blade’s service life under off-design conditions is analyzed.