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Energies 2018, 11(2), 342; https://doi.org/10.3390/en11020342

Investigation of Unsteady Flow Interactions in a Transonic High Pressure Turbine Using Nonlinear Harmonic Method

1
National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, School of Energy and Power Engineering, Beihang University, Beijing 100191, China
2
Collaborative Innovation Center of Advanced Aero-Engine, Beihang University, Beijing 100191, China
3
Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
4
School of Aeronautics and Astronautics, and ZJU-UIUC Institute, Zhejiang University, Zhejiang 310027, China
*
Authors to whom correspondence should be addressed.
Received: 4 January 2018 / Revised: 21 January 2018 / Accepted: 24 January 2018 / Published: 2 February 2018
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Abstract

The performance of a transonic high pressure turbine is mainly influenced by the unsteady interactions associated with the passing blades. In this paper, the unsteady flow interactions in a transonic turbine have been numerically investigated using the nonlinear harmonic (NLH) method in comparison with the steady and unsteady Reynolds-averaged Navier–Stokes (RANS). The comparison shows that the NLH method using three harmonics could capture the main unsteady flow interactions efficiently with about seven times smaller computational cost than the unsteady RANS, resulting in a more accurate time-averaged flow than for steady RANS. However, the continuity of the flow variables across the rotor-stator interface has shown some discrepancies compared with the unsteady RANS, which can be further satisfied by increasing the numbers of harmonics. The unsteady interactions are analyzed in detail; the results show that the wake and trailing edge shock from the upstream stator are the major sources of unsteadiness in the downstream rotor passage. The stator trailing edge shock impinges on the suction side of the passing rotor blades and generates pressure waves. These pressure waves are periodically reflected back to trigger the stator wake shedding. These waves are strong enough to travel through the rotor passage, and eventually affect the flow at the rotor’s trailing edge. The stator wakes are chopped by the downstream rotor, and travel through the rotor passage. This significantly enhances the unsteadiness of the flow near the rotor trailing edge. Lastly, the deterministic stresses and enthalpy distributions extracted from the NLH method have revealed that the effects of the unsteadiness are relatively weaker in the axial direction. Furthermore, the deterministic correlations analysis has shown that, some empirical deterministic correlations models based on the decay concept of compressors are not suitable for turbines. View Full-Text
Keywords: nonlinear harmonic method; unsteady interaction; transonic turbine; deterministic stress; deterministic enthalpy; harmonic pressure amplitude nonlinear harmonic method; unsteady interaction; transonic turbine; deterministic stress; deterministic enthalpy; harmonic pressure amplitude
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Asghar, M.A.; Liu, Y.; Cui, J.; Lu, L. Investigation of Unsteady Flow Interactions in a Transonic High Pressure Turbine Using Nonlinear Harmonic Method. Energies 2018, 11, 342.

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