Investigation of aerodynamic excitation and forced vibration induced by rotor-stator interaction on the radial turbine with double-row staggered tubular nozzles in aircraft environment control system

Under complex flight conditions, the aircraft environmental control system (ECS) plays an important role in ensuring the comfortable cabin environment and reliability of the electronic system. Radial turbines in ECS are susceptible to high-cycle fatigue (HCF) failures caused by rotor-stator interaction (RSI). Given the HCF failures frequently identified in radial turbines with double-row staggered tubular nozzles, this study investigated the behavior and formation mechanism of aerodynamic excitation by the nonlinear harmonic (NLH) method. The forced vibration of the turbine wheel was investigated using the fluid–structure interaction (FSI) approach, which was validated by the vibration experiment. The influence of the inlet and outlet pressure on the aerodynamic excitation was discussed. The results demonstrate that the staggered double-row tubular nozzles induce a partial conversion of first-order aerodynamic excitation into second-order aerodynamic excitation. Consequently, the overall second-order aerodynamic excitation is comparable to the first-order aerodynamic excitation, with the maximum difference being only 13 % in the paper. The two full resonance points with high stress are both induced by second-order aerodynamic excitation, which causes the HCF failure at the leading edge of the splitter blade. A substantial risk of damage to the leading edge of the main blade is also observed. Furthermore, variations in inlet and outlet pressures induce proportional changes in aerodynamic excitation, which accounts for the non-monotonic relationship between excitation amplitude and expansion ratio in ECS radial turbines. This finding provides practical guidance for ground-based HCF testing.