Analytical Investigation of the Unsteady Aerodynamic Environments in Space Shuttle Main Engine (SSME) Turbines

Abstract

Unsteady computational fluid dynamics (CFD) analyses of the SSME alternate turbopump development (ATD) high pressure fuel turbopump (HPFTP) and high pressure oxidizer turbopump (HPOTP) turbine first stage blades are presented. Modal analyses of the first stage blades of each turbine indicated possible resonance problems in crucial operating ranges of the turbopumps. Unsteady aerodynamic simulations were conducted for each turbine to support further investigations of dynamic responses of the first stage blades. To appropriately characterize the aerodynamic environments in the turbines, unsteady, multistage, and multiblade calculations were required. Within this set of requirements, two approaches were taken. The first approach was to apply a two-dimensional (2D) Navier-Stokes code at each turbine midspan. Because the unsteady interactions were believed to be dominated by wake effects, this viscous approach was considered to be the more accurate. However, unsteady Navier-Stokes calculations have been shown to be computer intensive. Therefore, a second, quicker approach was undertaken. This approach was to apply, at each turbine midspan, an Euler code modified with a shear stress model that was calibrated with a set of turbine test data. Comparisons of time-averaged and transient pressure distributions, axial and tangential loads, and entropy contours calculated by each approach are presented. Discrepancies between results are noted and the relative merits of each approach are discussed.