| Gas turbine is a key power equipment for aviation and energy utilization.In order to achieve higher power and efficiency,the temperature of hot components usually exceeds the allowable material temperature.Therefore,the efficient and advanced cooling structure of hot components is essential.Film cooling is one of the core cooling technologies for high temperature blades,and its fine design is of great significance for improving gas turbine performance.Normally,in real blades,the coolant first flows through the internal ribbed passage and then flows into the film hole.The coolant flow direction at the entrance of film hole is perpendicular to the mainstream flow direction,which means crossflow feeding.However,most of the studied are used stagnant plenum to feed coolant,which ignores the effects of crossflow feeding.Based on this,numerical simulation is adopted in this paper to analyze the effects of ribbed crossflow on film cooling characteristics.The main works are as follows:Firstly,the effect mechanism of smooth,45° rib and 135° rib channels on film cooling characteristics of cylindrical holes was studied,and the effects of different crossflow Reynold number and blowing ratios were considered.The results showed that the anticlockwise vortex is generated near the entrance of the film hole in the 45° rib channel,which does not match the inclined direction of the film hole,resulting in serious blockage at the entrance and low discharge coefficient.A clockwise vortex is generated near the entrance of the film hole in the135° rib channel.It matches the inclined direction of the film hole very well,so the blockage at the entrance is slight and the discharge coefficient is large.The change of crossflow Reynolds number has a great effect on the film cooling effectiveness of smooth channel and45° rib channel,but has little effect on 135° rib channel.Secondly,based on the above 45° and 135° rib channels,the effects of rib height on film cooling characteristics of cylindrical holes were studied.The results showed that with the increase of the rib height,the size of the rib induced vortex in the crossflow channel enlarge,and the vortex core moves from the side to the middle,which changes the velocity distribution at the entrance of the film hole,and then affects the film cooling effectiveness.With the increase of blowing ratio,the film cooling effectiveness of 45° rib channel varies with different rib heights.For the 135° rib channel,the film cooling effectiveness decreases with the increase of blowing ratio.Then,the interaction between upstream and downstream film cooling rows fed by ribbed crossflow channel was studied.The results showed that the film cooling effectiveness on both sides of the downstream film holes will suddenly expand outward when the film holes are arranged in line,while the film cooling effectiveness on both sides of the downstream film holes will contract inward when the arrangement is staggered.Different combination cases have great influence on film cooling effectiveness.The film cooling effectiveness of Case IAB is the highest when the blowing ratio is 0.5,and the film cooling effectiveness of Case SAA is the highest when the blowing ratio is 1.0.The staggered arrangement can increase the width of film cooling effectiveness and NHFR,so its overall cooling performance is better than that of in-line arrangement.Finally,the flow and heat transfer characteristics of trenched holes and sister holes were studied,and the effects of different coolant feeding methods on film cooling effectiveness,heat transfer coefficient ratio,NHFR and flow characteristics were analyzed.The results showed that the kidney vortex and anti-kidney vortex will be generated in the downstream of the trenched hole,which can enhance the spreading ability of coolant.The film cooling effectiveness and NHFR of 135° rib channel are high at different blowing ratios,while the film cooling performance of 45° rib channel is better only at high blowing ratio of 2.0.For sister holes,the kidney vortices at exit of the main hole and the auxiliary hole are close to each other,and there is no theoretical vortex structure in the downstream.With the increase of blowing ratio,the area-averaged film cooling effectiveness of different crossflow channels first increases and then decreases,among which the 45° rib channel is the highest,while the135° rib channel is the lowest.Moreover,the heat transfer coefficient ratio and NHFR of the45° rib channel are always higher than that of the 135° rib channel. |
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