To improve the cooling performance, shape optimization of a laidback fan-shaped film cooling hole was performed. Three geometric parameters, including hole length, lateral expansion angle and forward expansion angle, ...To improve the cooling performance, shape optimization of a laidback fan-shaped film cooling hole was performed. Three geometric parameters, including hole length, lateral expansion angle and forward expansion angle, were selected as the design parameters. Numerical model of the film cooling system was established, validated, and used to generate 32 groups of training samples. Least square support vector machine(LS-SVM) was applied for surrogate model, and the optimal design parameters were determined by a kind of chaotic optimization algorithm. As hole length, lateral expansion angle and forward expansion angle are 90 mm, 20° and 5°, the area-averaged film cooling effectiveness can reach its maximum value in the design space. LS-SVM coupled with chaotic optimization algorithm is a promising scheme for the optimization of shaped film cooling holes.展开更多
Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immed...Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immediate region of injection but also downstream region. This paper numerically investigated the film cooling effectiveness on two types of hole geometries which are cut-shaped hole and antivortex hole. The 3D computational geometries are modeled with a single 30 deg angled hole on a flat surface. The different blowing ratios of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5 and k-Epsilon turbulence model are used in this study. A two dimensional distribution of film cooling effectiveness in the downstream region of the cooling hole is performed. A comparison of spanwise averaged effectiveness is also performed in the field starts from center point of hole to X/D=-30.展开更多
Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detac...Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detached Eddy Simulation (SDES), Stress-Blended Eddy Simulation (SBES), and Zonal Large Eddy Simulation (ZLES), along with a no-model laminar simulation. Each is used to simulate an adiabatic flat plate film cooling experiment of a shaped hole at low Reynolds number. Adiabatic effectiveness is calculated for Blowing Ratio (BR) = 1.5 and Density Ratio (DR) = 1.5. The ZLES method and laminar simulation most accurately match experimental lateral-average adiabatic effectiveness along the streamwise direction from the trailing edge of the hole to 35 hole diameters downstream of the hole (X/D = 0 to X/D = 35), with RMS deviations of 5.1% and 4.2%, and maximum deviations of 8% and 11%, respectively. The accuracy of these models is attributed to the resolution of turbulent structures in not only the mixing region but in the upstream boundary layer as well, where the other methods utilize RANS and do not switch to LES.展开更多
Diffusion shaped film cooling holes with compound-angle diffuser structures exhibit superior cooling performance,which have gradually been applied in turbine blades of the advanced aeroengines.In our previous research...Diffusion shaped film cooling holes with compound-angle diffuser structures exhibit superior cooling performance,which have gradually been applied in turbine blades of the advanced aeroengines.In our previous research,the method of Servo Scanning three-dimensional Electrical Discharge Machining(SS-3D EDM)has been proven effective for high-precision machining of complex 3D cavities,offering notable advantages such as low tool cost,automatic compensation of electrode wear,and high machining flexibility.However,using tubular electrodes in SS-3D EDM,challenges persist under the conditions of the large layer depth.The lateral discharge phenomenon of tubular electrodes causes significant deformation at the electrode tip,increases the risk of lateral collisions,and complicates the accurate calculation of electrode wear length.To address these limitations,this research proposes a Trajectory Servo Scanning three-dimensional Electrical Discharge Machining(TSS-3D EDM)process.Axial servo motion of tubular electrode is used to maintain the discharge gap of electrode bottom,and an innovative trajectory servo motion along the tangential orientation is introduced to stabilize the lateral discharge gap,enabling automatic compensation for tool wear at the rotating electrode tip.The effect of servo control parameters on machining depth accuracy is analyzed.Furthermore,a method for electrode wear length calculation is proposed based on the voltage signals of discharge gaps.An estimation method for the electrode wear coefficient is presented.Machining experiments on superalloys validate the effectiveness and capabilities of the TSS-3D EDM method by fabricating fan-shaped and conical diffusion shaped film cooling holes.The results show that the calculation error of tubular electrode wear length<5%,the dimensional error of hole profile dimensions as 4%–6%,the repeatability error<±4μm,and the material removal rate up to 0.664 mm^(3)/min using tubular electrodes with an outer diameter of 0.4 mm.展开更多
基金Project(U1508212)supported by the National Natural Science Foundation of ChinaProject(2015M570448)supported by the Postdoctoral Science Foundation of China
文摘To improve the cooling performance, shape optimization of a laidback fan-shaped film cooling hole was performed. Three geometric parameters, including hole length, lateral expansion angle and forward expansion angle, were selected as the design parameters. Numerical model of the film cooling system was established, validated, and used to generate 32 groups of training samples. Least square support vector machine(LS-SVM) was applied for surrogate model, and the optimal design parameters were determined by a kind of chaotic optimization algorithm. As hole length, lateral expansion angle and forward expansion angle are 90 mm, 20° and 5°, the area-averaged film cooling effectiveness can reach its maximum value in the design space. LS-SVM coupled with chaotic optimization algorithm is a promising scheme for the optimization of shaped film cooling holes.
文摘Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immediate region of injection but also downstream region. This paper numerically investigated the film cooling effectiveness on two types of hole geometries which are cut-shaped hole and antivortex hole. The 3D computational geometries are modeled with a single 30 deg angled hole on a flat surface. The different blowing ratios of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5 and k-Epsilon turbulence model are used in this study. A two dimensional distribution of film cooling effectiveness in the downstream region of the cooling hole is performed. A comparison of spanwise averaged effectiveness is also performed in the field starts from center point of hole to X/D=-30.
文摘Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detached Eddy Simulation (SDES), Stress-Blended Eddy Simulation (SBES), and Zonal Large Eddy Simulation (ZLES), along with a no-model laminar simulation. Each is used to simulate an adiabatic flat plate film cooling experiment of a shaped hole at low Reynolds number. Adiabatic effectiveness is calculated for Blowing Ratio (BR) = 1.5 and Density Ratio (DR) = 1.5. The ZLES method and laminar simulation most accurately match experimental lateral-average adiabatic effectiveness along the streamwise direction from the trailing edge of the hole to 35 hole diameters downstream of the hole (X/D = 0 to X/D = 35), with RMS deviations of 5.1% and 4.2%, and maximum deviations of 8% and 11%, respectively. The accuracy of these models is attributed to the resolution of turbulent structures in not only the mixing region but in the upstream boundary layer as well, where the other methods utilize RANS and do not switch to LES.
基金co-supported by the Tsinghua University Initiative Scientific Research Program,China(No.20244186005)the Science Center for Gas Turbine Project,China(No.P2022-A-IV-002-003)the National Natural Science Foundation of China(No.92060108)。
文摘Diffusion shaped film cooling holes with compound-angle diffuser structures exhibit superior cooling performance,which have gradually been applied in turbine blades of the advanced aeroengines.In our previous research,the method of Servo Scanning three-dimensional Electrical Discharge Machining(SS-3D EDM)has been proven effective for high-precision machining of complex 3D cavities,offering notable advantages such as low tool cost,automatic compensation of electrode wear,and high machining flexibility.However,using tubular electrodes in SS-3D EDM,challenges persist under the conditions of the large layer depth.The lateral discharge phenomenon of tubular electrodes causes significant deformation at the electrode tip,increases the risk of lateral collisions,and complicates the accurate calculation of electrode wear length.To address these limitations,this research proposes a Trajectory Servo Scanning three-dimensional Electrical Discharge Machining(TSS-3D EDM)process.Axial servo motion of tubular electrode is used to maintain the discharge gap of electrode bottom,and an innovative trajectory servo motion along the tangential orientation is introduced to stabilize the lateral discharge gap,enabling automatic compensation for tool wear at the rotating electrode tip.The effect of servo control parameters on machining depth accuracy is analyzed.Furthermore,a method for electrode wear length calculation is proposed based on the voltage signals of discharge gaps.An estimation method for the electrode wear coefficient is presented.Machining experiments on superalloys validate the effectiveness and capabilities of the TSS-3D EDM method by fabricating fan-shaped and conical diffusion shaped film cooling holes.The results show that the calculation error of tubular electrode wear length<5%,the dimensional error of hole profile dimensions as 4%–6%,the repeatability error<±4μm,and the material removal rate up to 0.664 mm^(3)/min using tubular electrodes with an outer diameter of 0.4 mm.
