A computational modeling for the sheet cavitating flows is presented. The cavitation model is implemented in a viscous Navier-Stokes solver. The cavity interface and shape are determined using an iterative procedure m...A computational modeling for the sheet cavitating flows is presented. The cavitation model is implemented in a viscous Navier-Stokes solver. The cavity interface and shape are determined using an iterative procedure matching the cavity surface to a constant pressure boundary. The pressure distribution, as well as its gradient on the wall, is taken into account in updating the cavity shape iteratively. Numerical computations are performed for the sheet cavitating flows at a range of cavitation numbers across the hemispheric headform/cylinder body with different grid numbers. The influence of the relaxation factor in the cavity shape updating scheme for the algorithm accuracy and reliability is conducted through comparison with other two cavity shape updating numerical schemes. The results obtained are reasonable and the iterative procedure of cavity shape updating is quite stable, which demonstrate the superiority of the proposed cavitation model and algorithms.展开更多
The advanced optimization method named as adaptive range differential evolution(ARDE)is developed.The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard g...The advanced optimization method named as adaptive range differential evolution(ARDE)is developed.The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard genetic algorithm and differential evolution.Combined with parallel ARDE,surface modeling method and Navier-Stokes solution,a new automatic aerodynamic optimization method is presented.A low aspect ratio transonic turbine stage is optimized for the maximization of the isentropic efficiency with forty-one design variables in total.The coarse-grained parallel strategy is applied to accelerate the design process using 15 CPUs.The isentropic efficiency of the optimum design is 1.6%higher than that of the reference design.The aerodynamic performance of the optimal design is much better than that of the reference design.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
Tip clearance leakage flow in a radial inflow turbine rotor for microturbines under the stage environment is investigated using a three-dimensional viscous flow simulation. The results indicate that the scraping flow ...Tip clearance leakage flow in a radial inflow turbine rotor for microturbines under the stage environment is investigated using a three-dimensional viscous flow simulation. The results indicate that the scraping flow caused by relative motion between casing and rotor tip, and the pressure difference between pressure side and suction side at rotor tip, play important roles in tip clearance leakage flow. The more the rotor tip speed increases and tip clearance height decreases, the more the scraping effect acts. Though the leakage velocity of tip clearance at midsection and exducer regions changes less when the rotor rotational speed is changing, the distance between passage vortex and rotor suction side varies in evidence. Main leakage flow rate of tip clearance takes place at region of exducer tip and some seal configurations will be quite effective for cutting leakage flow if these configurations are arranged over midsection and exducer of the radial inflow rotor.展开更多
This paper presents an aerodynamic optimum design method for transonic turbine cascades based on the Genetic Algorithms coupled to the inviscid flow Euler solver and the boundary-layer calculation.The Genetic Algorith...This paper presents an aerodynamic optimum design method for transonic turbine cascades based on the Genetic Algorithms coupled to the inviscid flow Euler solver and the boundary-layer calculation.The Genetic Algorithms control the evolution of a population of cascades towards an optimum design.The fitness value of each string is evaluated using the flow solver. The design procedur6 has been developed and the behavior of the genetic algorithms has been tested. The objective functions of the design examples are the minimum mean-square deviation between the aimed pressure and computed pressure and the minimum amount of user expertise.展开更多
Based on control theory,adjoint system for the general problem of turbomachinery aerodynamic optimization was studied and developed in the present paper by using the variation technique in the grid node coordinates co...Based on control theory,adjoint system for the general problem of turbomachinery aerodynamic optimization was studied and developed in the present paper by using the variation technique in the grid node coordinates combined with Jacobian Matrics of flow fluxes.Then the adjoint system for aerodynamic design optimization of turbine cascade governed by compressible Navier-Stokes equations was derived in detail.With the purpose of saving computation resources,the mathematic method presented in this paper avoids the coordinate system transforming in the traditional derivation process of the adjoint system and makes the adjoint system much more sententious.Given the general expression of objective functions consisting of both boundary integral and field integral,the adjoint equations and their boundary conditions were derived,and the final expression of the objective function gradient including only boundary integrals was formulated to reduce the CPU cost,especially for the complex 3D configurations.The adjoint system was solved numerically by using the finite volume method with an explicit 5-step Runge-Kutta scheme and Riemann approximate solution of Roe's scheme combined with multi-grid technique and local time step to accelerate the convergence procedure.Finally,based on the aerodynamic optimization theory in the present work,2D and 3D inviscid and viscous inverse design programs of axial turbomachinery cascade for both pressure distribution and isentropic Mach number distribution on the blade wall were developed,and several design optimization cases were performed successfully to demonstrate the ability and economy of the present optimization system.展开更多
In order to further understand the aerothermodynamic performance and flow loss mechanism of SCO_2 turbines, RANS equations and an SST Turbulence Model were chosen for a numerical study on the secondary flow and vortex...In order to further understand the aerothermodynamic performance and flow loss mechanism of SCO_2 turbines, RANS equations and an SST Turbulence Model were chosen for a numerical study on the secondary flow and vortex structure of cascades using the commercial software CFX. The dimensionless vorticity analysis method was used to study the flow characteristics of the logarithmic layer and viscous sublayer in high pressure guide vane cascades. The new vortex structure and formation mechanism of the vortices were given and analyzed. Simulation results indicated that during the motion of the boundary layer in the cascades, the logarithmic layer and viscous sublayer obtain the different rotational direction vorticity, respectively. The endwall logarithmic layer and pressure side leg of the horseshoe votex gradually develop into the passage vortex, with the endwall viscous sublayer gradually developing into the corner viscous sublayer vortex II and the endwall viscous sublayer vortex I. The endwall viscous sublayer that rolled by the passage vortex is encountered with the upstream-side and radial boundary layer of the vane at the suction separation line, forming the suction separation line vortex beside the passage vortex. A pair of radial transition vortices are formed between the wake and the main stream.展开更多
This paper investigated the effects of variable jetting nozzle angles on the cross-flow suppression and heat transfer enhancement of swirl cooling in gas turbine leading edge. The swirl chamber with vertical jet nozzl...This paper investigated the effects of variable jetting nozzle angles on the cross-flow suppression and heat transfer enhancement of swirl cooling in gas turbine leading edge. The swirl chamber with vertical jet nozzles was set as the baseline, and its flow fields and heat transfer characteristics were analyzed by 3D steady state Reynolds-averaged numerical methods to reveal the mechanism of cross-flow weakening the downstream jets and heat transfer. On this basis, the flow structure on different cross sections and heat transfer characteristics of swirl chamber with variable jetting nozzle angels were compared with the baseline swirl chamber. The results indicated that for the baseline swirl chamber the circumferential velocity gradually decreased and the axial velocity gradually increased, and the cross-flow gradually formed. The cross-flow deflected the downstream jets and drawn them to the center of the chamber, thus weakening the heat transfer. For swirl chamber with variable jetting nozzle angles, the air axial velocity is axial upstream, opposite to the mainstream, so that the impact effects of cross-flow on the jets were reduced, and the heat transfer was enhanced. Furthermore, with the increase of axial velocity along the swirl chamber, the jetting nozzle angle also gradually increased, as well as the effect of cross-flow suppression, which formed a relative balance. For all swirl chambers with variable jet nozzle angles, the thermal performance factors were all larger than 1, which indicated the heat transfer was enhanced with less friction increment.展开更多
基金This project is supported by the Grants from Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP), China(No.20040698049)Natural Science Foundation of Xi'an Jiaotong University, China(No.2004).
文摘A computational modeling for the sheet cavitating flows is presented. The cavitation model is implemented in a viscous Navier-Stokes solver. The cavity interface and shape are determined using an iterative procedure matching the cavity surface to a constant pressure boundary. The pressure distribution, as well as its gradient on the wall, is taken into account in updating the cavity shape iteratively. Numerical computations are performed for the sheet cavitating flows at a range of cavitation numbers across the hemispheric headform/cylinder body with different grid numbers. The influence of the relaxation factor in the cavity shape updating scheme for the algorithm accuracy and reliability is conducted through comparison with other two cavity shape updating numerical schemes. The results obtained are reasonable and the iterative procedure of cavity shape updating is quite stable, which demonstrate the superiority of the proposed cavitation model and algorithms.
基金This project is supported by Advanced Propulsion Technologies Demonstration Program of Commission of Science Technology and Industry for National Defense of China(No.APTD-0602-04).
文摘The advanced optimization method named as adaptive range differential evolution(ARDE)is developed.The optimization performance of ARDE is demonstrated using a typical mathematical test and compared with the standard genetic algorithm and differential evolution.Combined with parallel ARDE,surface modeling method and Navier-Stokes solution,a new automatic aerodynamic optimization method is presented.A low aspect ratio transonic turbine stage is optimized for the maximization of the isentropic efficiency with forty-one design variables in total.The coarse-grained parallel strategy is applied to accelerate the design process using 15 CPUs.The isentropic efficiency of the optimum design is 1.6%higher than that of the reference design.The aerodynamic performance of the optimal design is much better than that of the reference design.
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Supported by National High Technology Research and Development Program of China (Grant Nos. 2002AA503020, 2004AA503020)Doctoral Foundation of Xi’an Jiaotong University (Grant No. DFXJTU2005-02)
文摘Tip clearance leakage flow in a radial inflow turbine rotor for microturbines under the stage environment is investigated using a three-dimensional viscous flow simulation. The results indicate that the scraping flow caused by relative motion between casing and rotor tip, and the pressure difference between pressure side and suction side at rotor tip, play important roles in tip clearance leakage flow. The more the rotor tip speed increases and tip clearance height decreases, the more the scraping effect acts. Though the leakage velocity of tip clearance at midsection and exducer regions changes less when the rotor rotational speed is changing, the distance between passage vortex and rotor suction side varies in evidence. Main leakage flow rate of tip clearance takes place at region of exducer tip and some seal configurations will be quite effective for cutting leakage flow if these configurations are arranged over midsection and exducer of the radial inflow rotor.
文摘This paper presents an aerodynamic optimum design method for transonic turbine cascades based on the Genetic Algorithms coupled to the inviscid flow Euler solver and the boundary-layer calculation.The Genetic Algorithms control the evolution of a population of cascades towards an optimum design.The fitness value of each string is evaluated using the flow solver. The design procedur6 has been developed and the behavior of the genetic algorithms has been tested. The objective functions of the design examples are the minimum mean-square deviation between the aimed pressure and computed pressure and the minimum amount of user expertise.
基金supported by the National Natural Science Foundation of China (Grant No. 50776065)
文摘Based on control theory,adjoint system for the general problem of turbomachinery aerodynamic optimization was studied and developed in the present paper by using the variation technique in the grid node coordinates combined with Jacobian Matrics of flow fluxes.Then the adjoint system for aerodynamic design optimization of turbine cascade governed by compressible Navier-Stokes equations was derived in detail.With the purpose of saving computation resources,the mathematic method presented in this paper avoids the coordinate system transforming in the traditional derivation process of the adjoint system and makes the adjoint system much more sententious.Given the general expression of objective functions consisting of both boundary integral and field integral,the adjoint equations and their boundary conditions were derived,and the final expression of the objective function gradient including only boundary integrals was formulated to reduce the CPU cost,especially for the complex 3D configurations.The adjoint system was solved numerically by using the finite volume method with an explicit 5-step Runge-Kutta scheme and Riemann approximate solution of Roe's scheme combined with multi-grid technique and local time step to accelerate the convergence procedure.Finally,based on the aerodynamic optimization theory in the present work,2D and 3D inviscid and viscous inverse design programs of axial turbomachinery cascade for both pressure distribution and isentropic Mach number distribution on the blade wall were developed,and several design optimization cases were performed successfully to demonstrate the ability and economy of the present optimization system.
基金financially supported by the Postdoctoral Science Foundation of China (Grant No. 2017M613294XB)National Key R&D Program of China (Grant No. 2018YFB1501004)+3 种基金National Natural Science Foundation of China (Grant No. 51406166, 51706181 and 51806172)the Postdoctoral Science Foundation of Shaanxi Province of China (Grant No. 2017BSHQYXMZZ08)Key Programs of China Huaneng Group (Grant No. HNKJ15-H07), R&D Foundation of TPRI (Grant No.ZD-18-TYK13)Young Talent Programs of Chinese Society for Electrical Engineering(Grant No. JLB-2016-70)
文摘In order to further understand the aerothermodynamic performance and flow loss mechanism of SCO_2 turbines, RANS equations and an SST Turbulence Model were chosen for a numerical study on the secondary flow and vortex structure of cascades using the commercial software CFX. The dimensionless vorticity analysis method was used to study the flow characteristics of the logarithmic layer and viscous sublayer in high pressure guide vane cascades. The new vortex structure and formation mechanism of the vortices were given and analyzed. Simulation results indicated that during the motion of the boundary layer in the cascades, the logarithmic layer and viscous sublayer obtain the different rotational direction vorticity, respectively. The endwall logarithmic layer and pressure side leg of the horseshoe votex gradually develop into the passage vortex, with the endwall viscous sublayer gradually developing into the corner viscous sublayer vortex II and the endwall viscous sublayer vortex I. The endwall viscous sublayer that rolled by the passage vortex is encountered with the upstream-side and radial boundary layer of the vane at the suction separation line, forming the suction separation line vortex beside the passage vortex. A pair of radial transition vortices are formed between the wake and the main stream.
基金This study is financially supported by the National Natural Science Foundation of China(Grant No.51876156).
文摘This paper investigated the effects of variable jetting nozzle angles on the cross-flow suppression and heat transfer enhancement of swirl cooling in gas turbine leading edge. The swirl chamber with vertical jet nozzles was set as the baseline, and its flow fields and heat transfer characteristics were analyzed by 3D steady state Reynolds-averaged numerical methods to reveal the mechanism of cross-flow weakening the downstream jets and heat transfer. On this basis, the flow structure on different cross sections and heat transfer characteristics of swirl chamber with variable jetting nozzle angels were compared with the baseline swirl chamber. The results indicated that for the baseline swirl chamber the circumferential velocity gradually decreased and the axial velocity gradually increased, and the cross-flow gradually formed. The cross-flow deflected the downstream jets and drawn them to the center of the chamber, thus weakening the heat transfer. For swirl chamber with variable jetting nozzle angles, the air axial velocity is axial upstream, opposite to the mainstream, so that the impact effects of cross-flow on the jets were reduced, and the heat transfer was enhanced. Furthermore, with the increase of axial velocity along the swirl chamber, the jetting nozzle angle also gradually increased, as well as the effect of cross-flow suppression, which formed a relative balance. For all swirl chambers with variable jet nozzle angles, the thermal performance factors were all larger than 1, which indicated the heat transfer was enhanced with less friction increment.
