VALIDATION OF COMPRESSIBLE FLOW SOLVER WITH ROTHALPY EQUATION ON THE NASA ROTOR 67 TRANSONIC TURBOFAN TEST CASE

This work presents the validation of a recently implemented compressible flow solver within foam-extend on the example of NASA Rotor 67 transonic turbofan. NASA Rotor 67 transonic turbofan is the axial-flow fan which is a common test case for compressible flow in turbomachinery due to available comprehensive experimental data provided by Strazisar et al. The presented formulation of pressure-based, compressible flow solver is specific regarding energy conservation equation, which is alternatively described in terms of the conservation of rothalpy - a thermodynamic quantity of a compressible fluid that is constant over a streamline, conserved over a rotor or stator blade row, but not over a stage. Within this work, a focus is pointed on resolving the complex transonic flow within the NASA Rotor 67 turbofan in two characteristic operating points fully described by reference experimental data: first one is the nominal, near peak efficiency operating point, while the second one is near stall. Numerical results are compared with the experimental data in order to validate numerical code in use. NASA Rotor 67 turbofan geometry is well-known for the generation of vortices downstream of rotor in the vicinity of rotor blade trailing edge and in the tip-gap due to tip-leakage flow. Successful resolving of those vortices serve as the additional confirmation of capabilities of the new numerical code for solving complex compressible fluid flows in turbomachinery, especially in unstable parts of the turbofan operating range such as stall region. A number of additional numerical simulations were carried out by changing the back-pressure in order to generate the performance curve at the nominal angular velocity. Generated performance curve is compared with the performance curve obtained by experimental approach, presenting the numerical accuracy along the operating range of a turbofan.