Suppression mechanism of a novel chamber structure on the unsteady aerodynamic force

Abstract

Partial admission can ensure the efficient operation of the turbine unit while adjusting the aerodynamic load. It has a wide range of application prospects due to its advantages. However, the rotor blades of partial admission turbine are subjected to periodic airflow excitation, which affects the blade fatigue life to a large extent. Based on the control stage model, the optimized chamber structure was proposed to reduce the local aerodynamic exciting force in the previous research. However, the local aerodynamic exciting force was not significantly reduced in the nozzle group linking-up section. Therefore, a novel chamber structure by adding flow cavity at nozzle group linking-up section is proposed to effectively suppress the local aerodynamic exciting force. The three-dimensional unsteady numerical method is employed to analyze the flow parameters of the cascade and the variation of unsteady aerodynamic exciting force. The feasibility and superiority of the proposed novel chamber structure are explained from the flow mechanism. The simulation results show that the high-speed flow caused by the narrow flow space in the nozzle group linking-up section is greatly reduced. Thus, enabling the relief of the pressure sudden change and the promotion of pressure in the low-pressure zone. The local axial aerodynamic exciting force is reduced by up to 59.4%. Meanwhile, the novel chamber structure reduces the rotor inlet pressure value from the block section to the inlet section of the nozzle group linking-up section. The local axial aerodynamic exciting force is reduced by 6.8%. In addition, it is worth noting that the novel chamber structure does not have an obvious impact on the aerodynamic performance. The relative change of efficiency is only 0.91%. From the verification results, it is evident that the novel chamber structure can effectively reduce the local aerodynamic exciting force in the nozzle group linking-up section.