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
Nickel oxide (NiO_(x)) has significant cost and stability advantages over poly[bis (4-phenyl)(2,4,6-trimethyl phenyl)amine](PTAA) for inverted p-i-n perovskite solar cells (PSCs),but the poor NiO_(x)/perovskite contac...Nickel oxide (NiO_(x)) has significant cost and stability advantages over poly[bis (4-phenyl)(2,4,6-trimethyl phenyl)amine](PTAA) for inverted p-i-n perovskite solar cells (PSCs),but the poor NiO_(x)/perovskite contact stemming from some reactive species at the interface led to suboptimal device performance.To solve this problem,we take a multiple donor molecule approach,using 3,3’-(4,8-bis(hexylthio)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl)bis(10-(6-bromohexyl)-10H-phenoxazine)(BDT-POZ) as an example,to modify the NiO_(x)/perovskite interface.The primary goal was to reduce the under-coordinated Ni^(≥3+) cations via electron transfer from the donor molecules to NiO_(x),thus mitigating the detrimental reactions between perovskite and NiO_(x).Equally importantly,the hole extraction at the interface was greatly enhanced after the organic donor modification,since the hydrophobic species atop NiO_(x) not only enabled pinhole-free crystallization of the perovskite but also properly tuned the interfacial energy level alignment.Consequently,the PSCs with NiO_(x)/BDT-POZ HTL achieved a high power conversion efficiency (PCE) up to 20.16%,which compared excellently with that of the non-modified devices (17.83%).This work provides a new strategy to tackle the exacting issues that have so far impeded the development of NiO_(x) based PSCs.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
This paper describes the improvement of leading edge film cooling effectiveness for a turbine inlet guide vane by using fan-shaped film cooling holes. The modification details are presented in comparison with the base...This paper describes the improvement of leading edge film cooling effectiveness for a turbine inlet guide vane by using fan-shaped film cooling holes. The modification details are presented in comparison with the base-line configuration of cylindrical holes. Numerical simulations were carried out for the base-line and modified configurations by using CFX, in which the k-ε turbulence model and scalable wall function were chosen. Contours of adiabatic film cooling effectiveness on the blade surfaces and span-wise distributions of film cooling effectiveness downstream the rows of cooling holes interested for the different cooling configurations were compared and discussed. It is showed that with the use of fan-shaped cooling holes around the leading edge, the adiabatic film cooling effectiveness can be enhanced considerably. In comparison with the cylindrical film cooling holes, up to 40% coolant mass flow can be saved by using fan-shaped cooling holes to obtain the comparable film cooling effectiveness for the studied inlet guide vane.展开更多
Based on its band alignment,p-type nickel oxide(NiO_(x))is an excellent candidate material for hole transport layers in crystalline silicon heterojunction solar cells,as it has a smallΔEV and largeΔEC with crystalli...Based on its band alignment,p-type nickel oxide(NiO_(x))is an excellent candidate material for hole transport layers in crystalline silicon heterojunction solar cells,as it has a smallΔEV and largeΔEC with crystalline silicon.Herein,to overcome the poor hole selectivity of stoichiometric NiO_(x) due to its low carrier concentration and conductivity,silver-doped nickel oxide(NiO_(x):Ag)hole transport layers with high carrier concentrations were prepared by co-sputtering high-purity silver sheets and pure NiO_(x) targets.The improved electrical conductivity of NiO_(x) was attributed to the holes generated by the Ag^(+)substituents for Ni^(2+),and moreover,the introduction of Ag^(+)also increased the amount of Ni^(3+)present,both of which increased the carrier concentration in NiO_(x).Ag^(+)doping also reduced the c-Si/NiO_(x) contact resistivity and improved the hole-selective contact with NiO_(x).Furthermore,the problems of particle clusters and interfacial defects on the surfaces of NiO_(x):Ag films were solved by UV-ozone oxidation and high-temperature annealing,which facilitated separation and transport of carriers at the c-Si/NiO_(x) interface.The constructed c-Si/NiO_(x):Ag solar cell exhibited an increase in open-circuit voltage from 490 to 596 mV and achieved a conversion efficiency of 14.4%.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.
基金the support from NSFC(U2001217,21972006,51803035)the Shenzhen Peacock Plan(KQTD2016053015544057)+4 种基金the Shenzhen-Hong Kong Innovation Circle United Research Project(SGLH20180622092406130)the Nanshan Pilot Plan(LHTD20170001)the Guangdong Basic and Applied Basic Research Foundation(2020A1515110981)the Research Fund Program of Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices(2019B121203003)the Shenzhen Fundamental Research Program(JCYJ20190813105205501)。
文摘Nickel oxide (NiO_(x)) has significant cost and stability advantages over poly[bis (4-phenyl)(2,4,6-trimethyl phenyl)amine](PTAA) for inverted p-i-n perovskite solar cells (PSCs),but the poor NiO_(x)/perovskite contact stemming from some reactive species at the interface led to suboptimal device performance.To solve this problem,we take a multiple donor molecule approach,using 3,3’-(4,8-bis(hexylthio)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl)bis(10-(6-bromohexyl)-10H-phenoxazine)(BDT-POZ) as an example,to modify the NiO_(x)/perovskite interface.The primary goal was to reduce the under-coordinated Ni^(≥3+) cations via electron transfer from the donor molecules to NiO_(x),thus mitigating the detrimental reactions between perovskite and NiO_(x).Equally importantly,the hole extraction at the interface was greatly enhanced after the organic donor modification,since the hydrophobic species atop NiO_(x) not only enabled pinhole-free crystallization of the perovskite but also properly tuned the interfacial energy level alignment.Consequently,the PSCs with NiO_(x)/BDT-POZ HTL achieved a high power conversion efficiency (PCE) up to 20.16%,which compared excellently with that of the non-modified devices (17.83%).This work provides a new strategy to tackle the exacting issues that have so far impeded the development of NiO_(x) based PSCs.
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supported by the National 973 Program of China through grant number 2007CB210108
文摘This paper describes the improvement of leading edge film cooling effectiveness for a turbine inlet guide vane by using fan-shaped film cooling holes. The modification details are presented in comparison with the base-line configuration of cylindrical holes. Numerical simulations were carried out for the base-line and modified configurations by using CFX, in which the k-ε turbulence model and scalable wall function were chosen. Contours of adiabatic film cooling effectiveness on the blade surfaces and span-wise distributions of film cooling effectiveness downstream the rows of cooling holes interested for the different cooling configurations were compared and discussed. It is showed that with the use of fan-shaped cooling holes around the leading edge, the adiabatic film cooling effectiveness can be enhanced considerably. In comparison with the cylindrical film cooling holes, up to 40% coolant mass flow can be saved by using fan-shaped cooling holes to obtain the comparable film cooling effectiveness for the studied inlet guide vane.
基金supported by the National Natural Science Foundation of China(Grant No.61974076)the China National Key R&D Program(Grant No.2022YFC2807104).
文摘Based on its band alignment,p-type nickel oxide(NiO_(x))is an excellent candidate material for hole transport layers in crystalline silicon heterojunction solar cells,as it has a smallΔEV and largeΔEC with crystalline silicon.Herein,to overcome the poor hole selectivity of stoichiometric NiO_(x) due to its low carrier concentration and conductivity,silver-doped nickel oxide(NiO_(x):Ag)hole transport layers with high carrier concentrations were prepared by co-sputtering high-purity silver sheets and pure NiO_(x) targets.The improved electrical conductivity of NiO_(x) was attributed to the holes generated by the Ag^(+)substituents for Ni^(2+),and moreover,the introduction of Ag^(+)also increased the amount of Ni^(3+)present,both of which increased the carrier concentration in NiO_(x).Ag^(+)doping also reduced the c-Si/NiO_(x) contact resistivity and improved the hole-selective contact with NiO_(x).Furthermore,the problems of particle clusters and interfacial defects on the surfaces of NiO_(x):Ag films were solved by UV-ozone oxidation and high-temperature annealing,which facilitated separation and transport of carriers at the c-Si/NiO_(x) interface.The constructed c-Si/NiO_(x):Ag solar cell exhibited an increase in open-circuit voltage from 490 to 596 mV and achieved a conversion efficiency of 14.4%.
