Prediction Method of Off-Design Aerodynamic Parameter Radial Distributions Between Blade Rows in a Multi-Stage Turbine Based on Stage Similarity Characteristics

A method for predicting aerodynamic parameters radial distribution between blade rows in a multi-stage turbine under different operating conditions is proposed. The primary objective is to efficiently obtain the needed parameters, which are derived from the assessment of on-design and off-design conditions conducted during the design process of the turbine’s main flow path. This method is based on the stage similarity characteristics and radial balance of the turbine. By analyzing the flow characteristics, expansion ratio, and efficiency of each stage, as well as the total pressure recovery coefficient of each stage’s guide vanes, and the Mach number and flow angle of each axial clearance between blade rows, it is possible to determine the average velocity and density between blade rows under different operating conditions. The distribution of velocity and density between blade rows under various operating conditions can be estimated based on the circumferentially-averaged flow field at the design point. Additionally, the distribution of static pressure can be calculated using the radial-equilibrium equation. These distribution results enable the calculation of the turbine blade’s axial force and provide boundary conditions for secondary air system analysis. To validate the proposed method, a three-stage axial turbine is used as a case study. The results demonstrate that, for most operating conditions above idle, the predicted pressure exhibits a comparatively high level of accuracy, with a maximum error of less than 5%. Furthermore, the predicted axial blade forces have a maximum error of less than 5%. The validation demonstrates that the proposed method satisfactorily fulfills engineering requirements.