关键词: 轴断裂, 动态仿真, 涡轮, 超转, 变比热

Abstract: Based on physical mechanisms, this study establishes a simulation model of the unloaded turbine integrating initial operating conditions, interpolation calculation, power calculation and rotor dynamic calculation, aiming to reveal the dynamic evolution law of the speed of unloaded turbines after shaft failure. The model adopts the backbone char-acteristic method to extend the high-speed characteristics of the turbine and obtain the flow and efficiency charac-teristics at high speeds; combined with the combustion toolbox, it analyzes the variable specific heat effect caused by changes in gas composition, and defines the correction coefficients for corrected speed and mass flow based on the similarity theory, thus realizing the accurate extrapolation of turbine characteristics under fuel-rich conditions. Furthermore, the control variable method is employed to systematically investigate the influence laws of fuel-air ratio, initial speed, mass flow, as well as inlet parameters on the speed variation of the turbine. The results show that an increase in the fuel-air ratio significantly enhances turbine acceleration by altering the specific heat at con-stant pressure and specific heat ratio of the gas; the lower the initial speed, the higher the average acceleration of the turbine, and even if shaft failure occurs under low-speed operating conditions, the turbine may still overspeed rapidly to the disc burst speed; the mass flow is extremely sensitive to the speed response, and reducing the mass flow can effectively restrain the rise of speed; inlet temperature is positively correlated with turbine acceleration, while inlet pressure indirectly acts on the speed evolution by influencing the corrected mass flow. This paper elabo-rates on the physical mechanisms by which various factors affect the speed of unloaded turbines, and provides a theoretical basis and technical support for the design of turbine overspeed protection strategies and the whole-engine safety simulation of aero-engines under the shaft failure condition.

Key words: shaft failure, dynamic simulation, turbine, overspeed, variable specific heat