Steady and Unsteady Numerical Characterization of the Secondary Flow Structures of a Highly Loaded Low-Pressure Compressor Stage

peer reviewedThis paper presents the numerical characterization of a highly loaded compressor by means of 3D unsteady RANS simulations. The focus is on critical flow structures and their evolution at different operating points of the machine. First, the numerical setup and mesh quality are presented to support the reliability of the provided results. The comparison against experiments is then described for this purpose. Later, a full description of the unsteady behavior of the machine is provided, giving special attention to the two regions where the most critical features are expected: the rotor hub wall and the casing. Rotor–stator interactions are then investigated and the role of the inlet guide vane (IGV) is finally discussed. Results are analyzed at design and near-stall conditions, with a focus on the behavior close to the stability limit at 100% speed

ON THE IMPACT OF THE TURBULENCE MODEL ON THE SECONDARY FLOW STRUCTURE OF A HIGHLY-LOADED COMPRESSOR STAGE

peer reviewedRANS turbulence models still represent a weak point of industrial simulations of turbomachinery flows. In presence of a large blade loading the turbulence model can impact severely on the prediction of the end-wall flow and secondary structures in the blade passage, with an important effect on the computed global performance and flow stability. This paper presents a turbulence model comparison for the characterization of a highly-loaded low-pressure compressor at multiple operating points using 3D RANS simulations. The turbulence models mostly employed for the design and analysis of axial compressors are considered, with the aim of providing a clear physical description of their impact on the critical flow features of the machine. It will be shown that no single turbulence model is generally better than others and the prediction depends on the operating point, with increasing discrepancies as the mass-flow is reduced

Forced Response Analysis of a Highly-Loaded Low-Pressure Compressor Stage With Inlet Distortions

peer reviewedAbstract Due to modern evolutions in propulsion, in view of obtaining higher propulsive efficiency, turbofan engines are subjected to ever higher inlet flow distortions. In these systems, structural damage can be induced by distortion patterns with excitation close to the blade natural frequency. To fill the gap currently present in literature about the impact of inlet distortions on the aeroelastic behaviour of engine components, this paper presents an aerodynamic damping and forced-response analysis on a highly-loaded axial compressor subjected to intake total pressure distortions. First, a stability analysis for the vibrational mode with natural frequency close to the resonance condition at the nominal speed of the machine is performed. Blade deformations are then computed through a distortion induced forced-response analysis at different distortion amplitudes. This work aims at studying the aeromechanical behaviour of a modern compressor, highlighting that the amplitude of the blade vibration does not increase linearly with the distortion amplitude

Redesign of a closed-loop high-speed facility to test distortion generators

peer reviewedAircraft engine architectures are currently in the phase of a change to meet future market demands. Certain such novel architectures force engines to operate under distorted inflow conditions, which are undesirable during flight. It is important to characterize the effect of such inflow distortions in order to understand the impact on the performance of engine components. This paper discusses the design and development of a novel test-facility that has the capability to test combined total pressure and swirl distortion generators under desired flow conditions. The return duct of the high-speed closed-loop compressor rig R4 at the von Karman Institute for Fluid Dynamics (VKI) has been redesigned to incorporate a test-section where distortion generators can be tested and characterized. Thus, a compressor test-rig is modified to act also as a wind tunnel capable of testing distortion generators at engine-like conditions

Poster ASME Turbo Expo 2022

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