涡轴发动机动力涡轮转子失去负载转速预测

Speed prediction for power turbine rotors of turboshaft engine on loss-of-load

为满足发动机适航规章CCAR33.27对涡轮失去负载时转子完整性的设计要求,研究涡轮失去负载瞬间转速随时间变化规律。采用多点稳态法对动力涡轮超转瞬时气动效率与转速对应关系进行研究,在此基础上,假设动力涡轮进口燃气能量不变,进而分析动力涡轮扭矩与转速的变化关系。然后采用理论力学和工程分析相结合的方法建立了动力涡轮失去负载瞬间转子转速随时间变化预测模型,并采用整机试验数据对该模型进行了验证,证明了该预测模型的合理性和准确性,建立的预测模型可为动力涡轮强度和超转保护设计提供理论依据。研究结果表明,动力涡轮转子失去负载后转速在200~300 ms上升至160%,接近大部分轮盘破裂转速,需要在涡轴发动机超转保护设计中引起足够重视。

In order to meet the integrity of the rotor design requirements of the engine airworthiness regulation CCAR33.27 on turbine loses-of-load, the time-dependent law of the turbine speed on the moment of loss-of-load was studied. The multi-point steady-state method was used to study the relationship between the transient aerodynamic efficiency of the power turbine and the speed. On this basis, assuming that the power turbine inlet gas energy remains constant, the relationship between the torque and the speed of the power turbine was analyzed. Then, a combination of theoretical mechanics and engineering analysis was performed to establish a prediction model for the time-dependent change of rotor speed for the loss-of-load on a turbine, and the model was verified by engine test data, which proved the rationality and accuracy of the prediction model. The established prediction model can provide a theoretical basis for the design of power turbine strength and overspeed protection. The research results showed that the speed of the power turbine rotor can reach 160% in 200-300 ms after loss-of-load, which was close to the rupture speed of most disks. Special attention should be paid to the design of turboshaft-engine overspeed protection.