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.