Zhao Liu

Numerical Study of Swirl Cooling in a Turbine Blade Leading-Edge Model

In this paper, a numerical simulation is conducted to predict the swirl cooling performance of an internal leading-edge cooling passage model for a gas turbine blade. The swirling cooling performance and its effectiveness are investigated in the case of two rectangular section inlets that cause flow to impinge tangentially on the internal surface of the circular cooling passage. Parametric analysis on the local and average flows and heat transfers are performed at various Reynolds numbers, as well as the ratio of swirl chamber radius to jet slot height for a constant ratio of swirl chamber radius to jet nozzle length and constant jet nozzle area, respectively. The results indicate that the position of the swirl flow center is changing along the axial of the swirl chamber, and the swirl flow center of one constant axial section is not uniform as well in different ratios of swirl chamber radius to jet slot height. The larger ratio of swirl chamber radius to jet slot height and the higher Reynolds number are...

Numerical study on the effect of jet spacing on the Swirl flow and heat transfer in the turbine airfoil leading edge region

ABSTRACT In this paper, flow and heat transfer of a swirl chamber that models an internal cooling passage for a gas turbine airfoil leading edge is studied with numerical simulation. The geometry consists of a circular pipe, and rectangular section inlets that lead inlet flow to impinge tangentially on the circular pipe. The effects of the ratio of jet spacing to swirl chamber radius and Reynolds numbers on swirl cooling performance are investigated. The results indicate how the pressure loss and globally averaged Nusselt number on the swirl chamber wall increase with increases of Reynolds number and the ratio of jet spacing to swirl chamber radius. A Nusselt number correlation on these parameters is suggested. Also shown is how Nusselt numbers on the swirl chamber surface increase with the ratio of jet spacing to swirl chamber radius.

Numerical Study on the Effect of Jet Slot Height on Flow and Heat Transfer of Swirl Cooling in Leading Edge Model for Gas Turbine Blade

In this paper a numerical simulation is conducted to predict the swirl cooling performance of an internal leading edge cooling passage model for gas turbine blade. The Shear-Stress Transport (SST) κ-ω model is adopted for the simulation as this model was found as the best one based on authors’ previous work. Two rectangular section inlets that cause flow to impinge tangentially on the internal surface of the circular cooling passage are arranged to investigate the swirl cooling performance and its effectiveness. The effects of the Reynolds numbers, the ratio of swirl chamber radius to jet slot height with constant ratio of swirl chamber radius to jet nozzle length, and the ratio of swirl chamber radius to jet slot height while jet nozzle area is constant on the local and average flow and heat transfer characteristics for swirl cooling on cylindrical pipe are studied. The results indicate that the position of the swirl flow center is changing along the axial of the swirl chamber, and the swirl flow center of one constant axial section is not uniform as well in different ratios of swirl chamber radius to jet slot height. And larger ratio of swirl chamber radius to jet slot height and larger Reynolds number are desirable to improve the performance of swirl cooling on the turbine leading edge, though the pressure loss of the swirl chamber will increase.© 2013 ASME

Influence of Jet Impingement Configurations and Aerothermal Variables on Film Cooling

In this study, the effects of impingement with various configurations at different aerothermal conditions on film cooling are investigated. The detailed adiabatic film cooling effectiveness distributions are obtained by solving steady three dimensional Reynolds-averaged Navier-Stokes equations with SST k-ω turbulence model closure. The influence of impingement on film cooling effectiveness is revealed by comparing the results from two cases: one where coolant is directly fed from a plenum (baseline case) and the other where the film coolant is extracted from the post-impingement flow on spherical dimples. For the latter case with post-impingement flow, the variations of the jet impingement configurations are considered at separation distances (H/Dj) from jet plate to target surface of 1, 2, 4 and 6, and eccentricities (F/Dj) between dimple center and film hole center of 0, 2, and 4. Besides, the effects of target wall heating the post-impingement flow on the external adiabatic film cooling performance are examined. The temperature ratios of the target surface to main flow at the inlet are set at 0.6, 0.7 and 0.8. The results are presented for four various averaged jet Reynolds numbers, which correspond to blowing ratios ranging from 0.5 to 2.0. It is observed that the impingement through the jet plate brings out pressure re-distributions on the target plate with film holes, and the dominant effect is on the flow structures in the supply chamber and near the entrance of the film hole. At the lowest blowing ratio of 0.5, film cooling with post-impingement air on dimples is reduced in comparison with the baseline case, while at higher blowing ratios, the effect of the impingement configuration on film cooling all depends on the flow conditions. In addition, the heating effect of target wall on the post-impingement flow could lower the coolant-to-mainstream density ratio, and then reduces the adiabatic film cooling performance.Copyright

Effect of Film Extraction on Impingement Heat Transfer Characteristics of Jet Arrays on Spherical-Dimpled Surfaces

Detailed heat transfer distributions are numerically investigated on a multiple jet impingement target surface with staggered arrays of spherical dimples where coolant can be extracted through film holes for external film cooling. The three dimensional Reynolds-averaged Navier-Stokes analysis with SST k-ω turbulence model is conducted at jet Reynolds number from 15,000 to 35,000. The separation distance between the jet plate and the target surface varies from 3 to 5 jet diameters and two jet-induced crossflow schemes are included to be referred as large and small crossflow at one and two opposite exit openings correspondingly. Flow and heat transfer results for the dimpled target plate with three suction ratios of 2.5%, 5.0% and 12.0% are compared with those on dimpled surfaces without film holes. The results indicate the presence of film holes could alter the local heat transfer distributions, especially near the channel outlets where the crossflow level is the highest. The heat transfer enhancements by applying film holes to the dimpled surfaces is improved to different degrees at various suction ratios, and the enhancements depend on the coupling effect of impingement and channel flow, which is relevant to jet Reynolds number, jet-to-plate spacing and crossflow scheme.Copyright