Hongyan Huang

Conjugate Heat Transfer Analysis of a High Pressure Air-Cooled Gas Turbine Vane

The ANSYS-CFX software is used to simulate NASA-Mark II high pressure air-cooled gas turbine. The work condition is Run 5411 which have transition flow characteristics. The different turbulence models are adopted to solve conjugate heat transfer problem of this three-dimensional turbine blade. Comparing to the experimental results, k-ω-SST-γ-θ turbulence model results are more accurate and can simulate accurately the flow and heat transfer characteristics of turbine with transition flow characteristics. But k-ω-SST-γ-θ turbulence model overestimates the turbulence kinetic energy of blade local region and makes the heat transfer coefficient higher. It causes that local region temperature of suction side is higher. In this paper, the compiled code adopts the B-L algebra model and simulates the same computation model. The results show that the results of B-L model are accurate besides it has 4% temperature error in the suction side transition region. In addition, different turbulence characteristic boundary conditions of turbine inner-cooling passages are given and K-ω-SST-γ-θ turbulence model is adopted in order to obtain the effect of turbulence characteristic boundary conditions for the conjugate heat transfer computation results. The results show that the turbulence characteristic boundary conditions of turbine inner-cooling passages have a great effect on the conjugate heat transfer results of high pressure gas turbine. ANSYS is applied to analysis the thermal stress of Mark II blade which has ten radial cooled passages and the results of Von Mises stress show that the temperature gradient results have a great effect on the results of blade thermal stress.Copyright

Coupled BEM and FDM Conjugate Analysis of a Three-Dimensional Air-Cooled Turbine Vane

A coupled boundary element method (BEM) and finite difference method (FDM) are applied to solve conjugate heat transfer problem of a three-dimensional air-cooled turbine blade. A loosely coupled strategy is adopted, in which each set of field equations is solved to provide boundary conditions for the other. In the fluid region, computation code (HIT-NS CODE) adopts the FDM to solve the Navier-Stokes equations. In the solid region, the BEM is adopted to resolve the conduction heat transfer equations. An iterated convergence criterion is the continuity of temperature and heat flux at the fluid-solid interface. The solid heat transfer computation code (3D-BEM CODE) is validated by comparing with the results of an analytic solution and the results of commercial code, the results from 3D-BEM CODE have a good agreement with the analytic solution and commercial code results. The BEM uses a weighted residual method to make the Laplace equation convert into a surface integral equation and the surface integral equation is discretized. The BEM avoids the complicated mesh needed in other computation methods and saves the computation time. In addition, the BEM has the characteristic of a combination of an analytic and a discrete solution. So the BEM solutions of heat conduction problems are more accurate. The results of the coupling computation code (HIT-NS-3DBEM CODE) have a good agreement with the experimental results. The adiabatic condition result is different from the results of experiment and code calculation. So the results from conjugate heat transfer analysis are more accurate and they are closer to realistic thermal environment of turbines. Four turbulence models are applied: K-epsilon model, K-omega model, K-omega (SST-Gamma Theta) model, and B-L model adopted by computation code. Different turbulence models gives different the results of vane wall temperature. Comparing the four turbulence models, the different turbulence models can exactly simulate the flow field, but they can not give exact values for the heat conduction simulation in the boundary layer. The result of K-Omega (SST-Gamma Theta) turbulence model is closer to the experimental data.Copyright

Numerical Simulation of Rotor Clocking Effect in a Low-Speed Compressor

Two-dimensional (2D) unsteady numerical simulation has been applied to study the effect of the variation in relative circumferential positions of rotors on the performance of a low speed compressor. The result shows that the variation will change the relative position of upstream rotor wake to the downstream rotor as well as the periodic and turbulent velocity fluctuations on the airfoils. When the upstream rotor wake impinges upon the leading edge of the downstream rotor, the corresponding stage efficiency will be higher; when the upstream wake is transferred into the mid-passage of the downstream rotor, the corresponding stage efficiency will be lower. The proper configuration of the relative position of rotors will cause obvious reduction in the unsteady aerodynamic effect on the second rotor airfoils and improve the aerodynamic performance of blades.

Fully Clocking Effect in a Two-Stage Compressor

Turbomachines have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. The important part of the unsteady effects results from the rotor-stator interaction. The main sources of unsteadiness in the rotor-stator interaction are potential flow interaction and wake interaction. Since the distribution of the potential flow and wake in the flow passage depends much on the relative position of blade row, variation in the relative circumferential position (clocking effect) of stator or rotor will change the distribution and consequently result in different multistage performance. The current study presents the experimental result of stator clocking effect in low-speed axial compressor, and performs numerical simulation to investigate the effects of fully (stator & rotor) clocking. In the test, time averaged data were collected. The result of time accurate flow calculation for stator clocking was in good qualitative agreement with experimental data. During the clocking of rotor, the stator was indexed to a position corresponding to maximum efficiency, and 8 clocking positions are compared for each clocking.© 2003 ASME

Topology and Vortex Structures of Turbine Cascade with Different Tip Clearances

Abstract This paper uses the topology theory to analyze the surface flow spectrums of straight, positively curved and negatively curved cascades with relative tip clearances of 0.023 and 0.036, finds apparent differences of topology and vortex structures in the blade tip and the suction side wall corner of single type of cascade with this two clearances, and studies the mechanism of the difference formation as well as their effects on the energy loss.