Numerical and Experimental Investigations on Optimized 3D Compressor Airfoils

Abstract

The objective of the presented work is to perform numerical and experimental studies on compressor stators. This paper presents the modification of a baseline stator design using numerical optimization resulting in a new 3D stator. The Rolls Royce in-house compressible flow solver HYDRA was employed to predict the 3D flow, solving the steady RANS equations with the Spalart-Allmaras turbulence model, and its corresponding discrete adjoint solver. The performance gradients with respect to the input design parameters were used to optimize the stator blade with respect to the total pressure loss over a prescribed incidence range, while additionally minimizing the flow deviation from the axial direction at the stator exit. Non-uniform profile boundary conditions, being derived from the experimental measurements, have been defined at the inlet of the CFD domain. The presented results show a remarkable decrease in the axial exit flow angle deviation and a minor decrease in the total pressure loss. Experiments were conducted on two compressor blade sets investigating the three-dimensional flow in an annular compressor stator cascade. Comparing the baseline flow of the 42° turning stator shows that the optimized stator design minimizes the secondary flow phenomena. The experimental investigation discusses the impact of steady flow conditions on each stator design while focusing on the comparison of the 3D optimized design to the baseline case. The flow conditions were investigated using five-hole probe pressure measurements in the wake of the blades. Furthermore, oil-flow visualization was applied to characterize flow phenomena. These experimental results are compared with the CFD calculations.

RBF-based morphing of B-Rep models for use in aerodynamic shape optimization

“…objectives, [34] decreased the exit flow angle by 38.6% and the total pressure losses by 3.2% w.r.t. the baseline.…”

“…The TurboLab Berlin compressor stator common research model has been tested in the measurement rig of the Chair for Aero Engines at TU Berlin. In the past, several research groups from academia and industry studied this case [31][32][33] and experiments were conducted on the original geometry and one optimized by Rolls-Royce Deutschland [34]. This stator is an aerodynamic model of a blade typically found in modern jet engine compressors.…”

CAD-based and CAD-free aerodynamic shape optimization of turbomachinery blade rows using the adjoint method

“…In order to validate the improved performance of the OPS, measurements were carried out for all three operating conditions using the experimental setup/procedure presented in subsection 2.7.2. whereas its performance at OD+ seems to be slightly worse (increased loss values for most of the passage height). More details regarding this comparison can be found in [209]. To conclude this subsection, the superior performance of the OPS geometry ob-…”

“…All the experiments were carried out using a low-speed open circuit wind tunnel at the Chair for Aero Engines of TUB [209], depicted in the schematic of fig. The annular measurement rig consists of the highly loaded compressor stator cascade.…”

“…The accuracy of the approach presented in this subsection for computing geometric sensitivities was verified after comparing the FD against AD values (following section). This approach was selected to perform the CAD-based optimization of the Compressor OGV case, which has led to the publications [46,209]; results are presented in section 5.5. Computing geometric sensitivities using central FD was found to (practically) remove the dependency on the perturbation step size (a constant value of δb = 0.01 was used for every design parameter), and the total cost required for the dX S db computation (for N = 196) was 48 min (∼ 15 sec per parameter), which is almost half the cost of the previous approach (subsection 5.3.1).…”