The turbine blades of aircrafts must be properly cooled to prevent engine failure.Thus,to investigate the influence of the tip structure on the film cooling effect,pressure-sensitive paint test technology was used to ...The turbine blades of aircrafts must be properly cooled to prevent engine failure.Thus,to investigate the influence of the tip structure on the film cooling effect,pressure-sensitive paint test technology was used to determine the adiabatic film cooling effectiveness in this study.The experiment was completed in a cascade comprising three straight blades.The effects of the blowing ratio,density ratio,tip clearance,and tip structure on film cooling efficiency were analyzed.The experimental results demonstrated that,as the blowing ratio increased,the film coverage area and film cooling efficiency increased under most experimental conditions.However,the film cooling efficiency was found to initially increase,and subsequently decrease,as the blowing ratio increased.The respective influences of the density ratio and tip clearance on the film cooling efficiency were found to be significant.The density ratio experiments revealed that a high-density ratio can result in better film coverage than the low-density-ratio air.The tip clearance experimental results indicated that a small tip clearance promotes an increase in film cooling efficiency;this is because the small tip clearance negatively affects the main stream leakage flow,which can reduce the film coverage area.Under the conditions of the Base case 2 configuration,a blowing ratio of 2.1,and a tip clearance of 0.6%h,the average film cooling efficiency of the blade tip was 0.22.Among the three blade tip structures applied in this study,Base case 2 demonstrated higher film cooling efficiency than the other two blade tip structures under the conditions of the same blowing ratio,tip clearance,and density ratio.展开更多
As one of the hottest components of gas turbine,the blade tip is difficult to be cooled down for the complexity flow field in the tight tip clearance.The blade tip protection requires advanced tip structures.To develo...As one of the hottest components of gas turbine,the blade tip is difficult to be cooled down for the complexity flow field in the tight tip clearance.The blade tip protection requires advanced tip structures.To develop new structures,the effect of ribs on blade squealer tip aerothermal performance and cooling performance were investigated.Ribbed squealers tips(1R,2R and 3R,compared to the Basic case) were designed and their cooling ability under five coolant blowing ratios(M) were measured by the Pressure Sensitive Paint(PSP)technique,taking film cooling effectiveness(η) as the criterion.Numerical method was validated and then was adopted to analyze the flow field and aerodynamic loss in the tip gap.The results indicated that the cooling coverage and η increase with M for sufficient coolant supply.Compared to the Basic case,the η on the middle section is higher while that on the trailing part is lower for the ribbed squealer tips.The flow field analysis showed that the coolant flows downstream to the trailing edge in the Basic case,bringing additional cooling protect to the downstream region.The ribs induce vortices behind them to involve the local and upstream coolant and prevent upstream coolant from flowing down,leading to the improvement in the local and the degradation in the downstream for the film cooling performance.The aerodynamic results pointed out that the ribbed squealer tips are superior to the Basic case in terms of the aerodynamic performance,even though the tip leakage mass flow of these cases are larger than that of the Basic case.The maximum reduction on pressure loss coefficient is 16.2% for the ribbed squealer tip.展开更多
The recently developed European flaw assessment procedure, structural integrity assessment procedure（SiNTAP） is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw ...The recently developed European flaw assessment procedure, structural integrity assessment procedure（SiNTAP） is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement （CTOD） tests are conducted at 0℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone （HAZ） specimens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assessment procedure-fracture assessment diagram（SINTAP FAD） method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.展开更多
基金supported by the National Natural Science Foundation of China (51906008)the Fundamental Research Funds for Central Universities (YWF-21-BJ-J-822)the National Science and Technology Major Project (2017-Ⅲ-0003-0027)
文摘The turbine blades of aircrafts must be properly cooled to prevent engine failure.Thus,to investigate the influence of the tip structure on the film cooling effect,pressure-sensitive paint test technology was used to determine the adiabatic film cooling effectiveness in this study.The experiment was completed in a cascade comprising three straight blades.The effects of the blowing ratio,density ratio,tip clearance,and tip structure on film cooling efficiency were analyzed.The experimental results demonstrated that,as the blowing ratio increased,the film coverage area and film cooling efficiency increased under most experimental conditions.However,the film cooling efficiency was found to initially increase,and subsequently decrease,as the blowing ratio increased.The respective influences of the density ratio and tip clearance on the film cooling efficiency were found to be significant.The density ratio experiments revealed that a high-density ratio can result in better film coverage than the low-density-ratio air.The tip clearance experimental results indicated that a small tip clearance promotes an increase in film cooling efficiency;this is because the small tip clearance negatively affects the main stream leakage flow,which can reduce the film coverage area.Under the conditions of the Base case 2 configuration,a blowing ratio of 2.1,and a tip clearance of 0.6%h,the average film cooling efficiency of the blade tip was 0.22.Among the three blade tip structures applied in this study,Base case 2 demonstrated higher film cooling efficiency than the other two blade tip structures under the conditions of the same blowing ratio,tip clearance,and density ratio.
基金supported by the National Science and Technology Major Project (J2019-Ⅲ-0007-0050)。
文摘As one of the hottest components of gas turbine,the blade tip is difficult to be cooled down for the complexity flow field in the tight tip clearance.The blade tip protection requires advanced tip structures.To develop new structures,the effect of ribs on blade squealer tip aerothermal performance and cooling performance were investigated.Ribbed squealers tips(1R,2R and 3R,compared to the Basic case) were designed and their cooling ability under five coolant blowing ratios(M) were measured by the Pressure Sensitive Paint(PSP)technique,taking film cooling effectiveness(η) as the criterion.Numerical method was validated and then was adopted to analyze the flow field and aerodynamic loss in the tip gap.The results indicated that the cooling coverage and η increase with M for sufficient coolant supply.Compared to the Basic case,the η on the middle section is higher while that on the trailing part is lower for the ribbed squealer tips.The flow field analysis showed that the coolant flows downstream to the trailing edge in the Basic case,bringing additional cooling protect to the downstream region.The ribs induce vortices behind them to involve the local and upstream coolant and prevent upstream coolant from flowing down,leading to the improvement in the local and the degradation in the downstream for the film cooling performance.The aerodynamic results pointed out that the ribbed squealer tips are superior to the Basic case in terms of the aerodynamic performance,even though the tip leakage mass flow of these cases are larger than that of the Basic case.The maximum reduction on pressure loss coefficient is 16.2% for the ribbed squealer tip.
基金This project is supported by National Natural Science Foundation of China(No.50375109).
文摘The recently developed European flaw assessment procedure, structural integrity assessment procedure（SiNTAP） is applied to assessment for welded joints of the API 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. As one of the basic input data, fracture toughness crack tip opening displacement （CTOD） tests are conducted at 0℃ and performed according to the requirements of the standard of BS7448. For the heat affected zone （HAZ） specimens, the microstructure observation is performed to insure that the tip of the crack is located in the coarse grain zone. The result explains the dispersity of the test values. In structural integrity assessment procedure-fracture assessment diagram（SINTAP FAD） method, the failure curves of welded joints at level 1 and 3 are derived from the tensile test results. The results of the assessment show that all assessment points are located within the failure lines of analysis level 1 and 3. So the welded joint of the pipeline is safe. This study laid the foundation of application of SINTAP to pipeline structure assessment.
