Prediction of railway wheel load unbalance induced by air suspension leveling valves using quasi-steady curve negotiation analysis procedure

While air suspensions are widely utilized for passenger railway vehicles as secondary suspension, initial lever angle setting of the air spring levelling valve can make a non-negligible impact on the residual wheel load unbalance in curve negotiation on small radius curved tracks. To enable accurate and quick prediction of the levelling valve-induced residual wheel load unbalance for vehicle safety evaluation, this study proposes a new quasi-steady curve negotiation analysis procedure considering the detailed thermodynamic air suspension system model that accounts for the nonlinear airflow characteristics of levelling valve and differential pressure valves. This approach allows for eliminating a limitation of existing full dynamic simulation models associated with high computational intensity that prevents quick safety evaluation with long-distance simulation under actual railway operating scenarios. A co-simulation scheme for the quasi-steady vehicle motion solver is also proposed to further improve the computational efficiency with explicit force-displacement coupling. Several numerical examples are presented to demonstrate the proposed quasi-steady vehicle motion solver for prediction of levelling valve-induced residual wheel load unbalances in small radius curved tracks. The numerical results are compared with those of the dynamic simulation model and validated against the test data. It is demonstrated that computational time is substantially decreased by the proposed approach while accurately predicting the levelling valve-induced residual wheel load unbalance caused by the initial offset of lever angles on small radius curved tracks.