采用涂敷和预制2种方式加入CoCrNi中熵粉末,研究该合金化粉末对铝/钢TIG熔钎焊接头形貌和组织性能的影响。试验结果表明:钢侧坡口涂敷中熵合金粉时,钎接面有椭球状未熔CoCrNi颗粒层存在,颗粒周围缝隙由灰色的Al基体和Al 0.7 Si 3Fe 0.3...采用涂敷和预制2种方式加入CoCrNi中熵粉末,研究该合金化粉末对铝/钢TIG熔钎焊接头形貌和组织性能的影响。试验结果表明:钢侧坡口涂敷中熵合金粉时,钎接面有椭球状未熔CoCrNi颗粒层存在,颗粒周围缝隙由灰色的Al基体和Al 0.7 Si 3Fe 0.3填充,界面两侧Al、Fe无明显元素扩散,残余CoCrNi颗粒一定程度上起到了增强相作用,但是其大小和分布的不均匀性影响了液态AlSi_(5)焊丝的流动,背面焊缝包覆性差,形成了较高余高和底部未熔合缺陷。预制方式下CoCrNi粉熔化与钢界面结合良好,熔敷金属在铝和钢表面有较好铺展,接头成形好,界面两侧各元素发生相互扩散,界面生成了Al_(0.7)Si_(3)Fe_(0.3)、Co_(3)Fe_(7)、Fe(Cr,Ni)和Al_(0.9)Ni_(1.1),金属间化合物(IMC)层平均厚3.15μm。CoCrNi中熵粉末有效阻隔了Al-Fe金属间化合物生成,2种方式下接头强度均大于未添加中熵合金粉的接头,其中预制中熵合金粉的强度较高(86 MPa)。涂敷中熵合金粉的接头维氏硬度最高达到467HV,位于钎接界面近焊缝侧,预制中熵合金粉的钢侧出现软化区,接头维氏硬度最高为248HV,位于近钎接界面钢侧。展开更多
Experimental and numerical investigations were conducted to investigate the variations of shock-wave boundary layer interaction(SBLI) phenomena in a highly loaded transonic compressor cascade with Mach numbers.The sch...Experimental and numerical investigations were conducted to investigate the variations of shock-wave boundary layer interaction(SBLI) phenomena in a highly loaded transonic compressor cascade with Mach numbers.The schlieren technique was used to observe the shock structure in the cascade and the pressure tap method to measure the pressure distribution on the blade surface.The unsteady pressure distribution on blade surface was measured with the fast-response pressure-sensitive paint(PSP) technique to obtain the unsteady pressure distribution on the whole blade surface and to capture the shock oscillation characteristics caused by SBLI.In addition,the Reynolds Averaged Navier Stokes simulations were used to compute the three-dimensional steady flow field in the transonic cascade.It was found that the shock wave patterns and behaviors are affected evidently with the increase in incoming Mach number at the design flow angle,especially with the presence of the separation bubble caused by SBLI.The time-averaged pressure distribution on the blade surface measured by PSP technique showed a symmetric pressure filed at Mach numbers of 0.85,while the pressure field on the blade surface was an asymmetric one at Mach numbers of 0.90 and 0.95.The oscillation of the shock wave was closely with the flow separation bubble on the blade surface and could transverse over nearly one interval of the pressure taps.The oscillation of the shock wave may smear the pressure jump phenomenon measured by the pressure taps.展开更多
Transonic tandem cascades can effectively increase the working load,and this feature conforms with the requirement of the large loads and pressure ratios of modern axial compressors.This paper presents an optimization...Transonic tandem cascades can effectively increase the working load,and this feature conforms with the requirement of the large loads and pressure ratios of modern axial compressors.This paper presents an optimization strategy for a German Aerospace Center(DLR)transonic tandem cascade,with one front blade and two rear blades,at the inlet Mach number of 1.051.The tandem cascade profile was parameterized using 19 control parameters.Non-dominated sorting Genetic algorithm(NSGA-II)was used to drive the optimization evolution,with the computational fluid dynamics(CFD)-based cascade performances correction added for each generation.Inside the automatic optimization system,a pressure boundary condition iterative algorithm was developed for simulating the cascade performance with a constant supersonic inlet Mach number.The optimization results of the cascade showed that the deflection of the subsonic blade changed evidently.The shock wave intensity of the first blade row was weakened because of the reduced curvatures of the optimized pressure and suction sides of the front blade part and the downstream moved maximum thickness position.The total pressure losses decreased by 15.6%,20.9%and 19.9%with a corresponding increase in cascade static pressure ratio by 1.3%,1.8%and 1.7%,for the three cascade shapes in the Pareto solution sets under the near choke,the design and near stall conditions,respectively.展开更多
This paper presents an experimental study of the self-sustained transonic shock oscillating behaviors in a heavy-duty gas turbine compressor cascade under the inlet Mach number of 0.85,0.90 and 0.95.The transonic shoc...This paper presents an experimental study of the self-sustained transonic shock oscillating behaviors in a heavy-duty gas turbine compressor cascade under the inlet Mach number of 0.85,0.90 and 0.95.The transonic shock patterns and the surface flow structures are captured by schlieren imaging and oil flow visualization.The time-averaged and instantaneous transonic shock oscillating behaviors at the near choke point and the near stall point are investigated by the Anodized Aluminum Pressure-Sensitive Paint(AA-PSP)surface pressure measurement.The normal passage shock dominant pattern and the detached bow shock dominant pattern at the near choke point and the near stall point are experimental characterized,respectively.The passage shock oscillation behaviors at the near choke point have been observed to undergo periodic pressure perturbations of the shock shift between the upstreamλshock feet mode and the downstreamλshock feet mode.The detached bow shock oscillation behaviors at the near stall point have been observed to undergo the pressure perturbations of the shock cycle movement between the upstream detached bow shock mode and the downstream detached bow shock mode.The differences between the shock shift mode and the shock cycle movement mode lead to the different streamwise oscillation travel ranges and different shock intensity variations under the same inlet Mach number.展开更多
基金supported by National Science and Technology Major Project (2017-Ⅱ-0007-0021)。
文摘Experimental and numerical investigations were conducted to investigate the variations of shock-wave boundary layer interaction(SBLI) phenomena in a highly loaded transonic compressor cascade with Mach numbers.The schlieren technique was used to observe the shock structure in the cascade and the pressure tap method to measure the pressure distribution on the blade surface.The unsteady pressure distribution on blade surface was measured with the fast-response pressure-sensitive paint(PSP) technique to obtain the unsteady pressure distribution on the whole blade surface and to capture the shock oscillation characteristics caused by SBLI.In addition,the Reynolds Averaged Navier Stokes simulations were used to compute the three-dimensional steady flow field in the transonic cascade.It was found that the shock wave patterns and behaviors are affected evidently with the increase in incoming Mach number at the design flow angle,especially with the presence of the separation bubble caused by SBLI.The time-averaged pressure distribution on the blade surface measured by PSP technique showed a symmetric pressure filed at Mach numbers of 0.85,while the pressure field on the blade surface was an asymmetric one at Mach numbers of 0.90 and 0.95.The oscillation of the shock wave was closely with the flow separation bubble on the blade surface and could transverse over nearly one interval of the pressure taps.The oscillation of the shock wave may smear the pressure jump phenomenon measured by the pressure taps.
基金financially supported by the National Science and Technology Major Project(2017-II-0007-0021)。
文摘Transonic tandem cascades can effectively increase the working load,and this feature conforms with the requirement of the large loads and pressure ratios of modern axial compressors.This paper presents an optimization strategy for a German Aerospace Center(DLR)transonic tandem cascade,with one front blade and two rear blades,at the inlet Mach number of 1.051.The tandem cascade profile was parameterized using 19 control parameters.Non-dominated sorting Genetic algorithm(NSGA-II)was used to drive the optimization evolution,with the computational fluid dynamics(CFD)-based cascade performances correction added for each generation.Inside the automatic optimization system,a pressure boundary condition iterative algorithm was developed for simulating the cascade performance with a constant supersonic inlet Mach number.The optimization results of the cascade showed that the deflection of the subsonic blade changed evidently.The shock wave intensity of the first blade row was weakened because of the reduced curvatures of the optimized pressure and suction sides of the front blade part and the downstream moved maximum thickness position.The total pressure losses decreased by 15.6%,20.9%and 19.9%with a corresponding increase in cascade static pressure ratio by 1.3%,1.8%and 1.7%,for the three cascade shapes in the Pareto solution sets under the near choke,the design and near stall conditions,respectively.
基金financially supported by the National Science and Technology Major Project(2017-Ⅱ-0007-0021)。
文摘This paper presents an experimental study of the self-sustained transonic shock oscillating behaviors in a heavy-duty gas turbine compressor cascade under the inlet Mach number of 0.85,0.90 and 0.95.The transonic shock patterns and the surface flow structures are captured by schlieren imaging and oil flow visualization.The time-averaged and instantaneous transonic shock oscillating behaviors at the near choke point and the near stall point are investigated by the Anodized Aluminum Pressure-Sensitive Paint(AA-PSP)surface pressure measurement.The normal passage shock dominant pattern and the detached bow shock dominant pattern at the near choke point and the near stall point are experimental characterized,respectively.The passage shock oscillation behaviors at the near choke point have been observed to undergo periodic pressure perturbations of the shock shift between the upstreamλshock feet mode and the downstreamλshock feet mode.The detached bow shock oscillation behaviors at the near stall point have been observed to undergo the pressure perturbations of the shock cycle movement between the upstream detached bow shock mode and the downstream detached bow shock mode.The differences between the shock shift mode and the shock cycle movement mode lead to the different streamwise oscillation travel ranges and different shock intensity variations under the same inlet Mach number.
