In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HE...In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can effectively inhibit the interfacial diffusion between Al and Mg,which is conducive to the formation of solid solution,especially when the thickness of HEA is 800 nm.With the increase of casting temperature from 720 ℃ to 730 ℃,740℃,and 750 ℃,α-Al(Mg),α-Al(Mg)+Al3Mg2,Al3Mg2+Al12Mg17,and Al12Mg17+δ-Mg are formed at the interface of Ti/Mg bimetal,respectively.When the thickness of the HEA layer is 800 nm and the pouring temperature is 720 ℃,the bonding strength of the Ti/Mg bimetal can reach the maximum of 93.6 MPa.展开更多
The Cd1-xZnxTe(CZT) single crystals were annealed by a two-step method including a vapor-environment step and a liquid-environment step in sequence. The effects of annealing on the properties of CZT were analyzed in...The Cd1-xZnxTe(CZT) single crystals were annealed by a two-step method including a vapor-environment step and a liquid-environment step in sequence. The effects of annealing on the properties of CZT were analyzed in detail. IR transmission measurement results show that IR transmission of CZT is improved dramatically after annealing. X-ray rocking curves indicate that the annealing treatment ameliorates crystal quality obviously, which is ascribed to the release of residual stress and the reduction of point defects. Photoluminescence(PL) spectra reveal that the full width at half maximum(FWHM) of the donor-bound exciton (D0, X) peak is reduced obviously, and the free exciton emission is weakened after annealing. Meanwhile, the intensity of the donor-acceptor pair(DAP) peak decreases to a great degree, which implies that the impurities are removed from CZT wafers. In addition, the deep defect-related emission band Dcomplex disappears after annealing, which mean that Cd vacancies are well-compensated. The results confirm that the two-step annealing is an effective approach to improve the qualities of CZT single crystals.展开更多
An efficient high-order numerical method for supersonic reactive flows is proposed in this article.The reactive source term and convection term are solved separately by splitting scheme.In the reaction step,an adaptiv...An efficient high-order numerical method for supersonic reactive flows is proposed in this article.The reactive source term and convection term are solved separately by splitting scheme.In the reaction step,an adaptive time-step method is presented,which can improve the efficiency greatly.In the convection step,a third-order accurate weighted essentially non-oscillatory(WENO)method is adopted to reconstruct the solution in the unstructured grids.Numerical results show that our new method can capture the correct propagation speed of the detonation wave exactly even in coarse grids,while high order accuracy can be achieved in the smooth region.In addition,the proposed adaptive splitting method can reduce the computational cost greatly compared with the traditional splitting method.展开更多
A fault tolerant control method is proposed in this paper for a turbofan engine gas path degradation through the full flight envelope. A Quantum-behaved Particle Swarm Optimization(QPSO) algorithm is applied to obtain...A fault tolerant control method is proposed in this paper for a turbofan engine gas path degradation through the full flight envelope. A Quantum-behaved Particle Swarm Optimization(QPSO) algorithm is applied to obtain engine inputs adjustments, which contribute to construct off-line performance accommodation interpolation schedules. With a double closed-loop control system structure, command control is corrected based on real-time fault diagnostic results. Simulations indicate that fault tolerant control could reduce thrust and stall margin loss effectively in gas path faults.展开更多
Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally s...Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally studied for supercritical fluids. Two types of flow excursion occur in a single tube. Type Ⅰ and Type Ⅱ excursions, and they are corresponding to decreasing and increasing flow rate respectively. They can trigger flow maldistribution between parallel tubes and the hysteresis phenomenon of flow distribution. The effects of system parameters, including inlet temperature,system pressure, and heat flux, on flow distribution were analyzed. In addition, the relationship between flow excursion and the pseudo-critical interval proposed in the literature was established according to the heated tube outlet temperature at the onset of flow instability. Finally, the flow excursion instability boundary was obtained using two dimensionless parameters. These experimental results can provide helpful insight on the mechanism of Scramjet regenerative cooling.展开更多
Al2O3 and Ti-6Al-4V alloy were brazed with Ag-Cu-Ti +B fillers in different brazing conditions. Effects of brazing temperature, holding time and additive Ti content on joints microstructure and shear strength were in...Al2O3 and Ti-6Al-4V alloy were brazed with Ag-Cu-Ti +B fillers in different brazing conditions. Effects of brazing temperature, holding time and additive Ti content on joints microstructure and shear strength were investigated by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, transmission electron microscopy and shear testing. Results indicate that TiCu and Ti(Cu,Al) decrease, but Ti2Cu and -Ti2(Cu,Al) increase in brazing seam with increasing brazing temperature, holding time and additive Ti content. Area consisting of Ti3(Cu,Al)30 and TiO near Al2O3 becomes gradually discontinuous from continuity when brazing temperature rises or holding time extends. As Ti additive content increases, TiO is absent near Al2O3, area consisting of only Ti3(Cu,Al)30 thickens. TiB whiskers are in situ synthesized by Ti and B atoms during brazing process. The brazing temperature, holding time and additive Ti content on joints microstructure influence the joints shear strength directly. The shear strength of joints, obtained at 850 ℃ holding for 10 min, reaches the maximum of 78 MPa. According to the experimental results, phase diagram and thermodynamics calculation, the interface evolution mechanism of the Al2O3/Ti-6Al-4V alloy joint was analyzed.展开更多
The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio ...The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×10 5 to 2.96×10 5 . The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioration of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer separation flow is severe. The interaction between boundary layer separation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.展开更多
Bamboo OSB(BOSB) medium experimental line and key equipments are presented for the first time based on the analysis of BOSB production technologies and processes requirements. Component of BOSB medium experimental lin...Bamboo OSB(BOSB) medium experimental line and key equipments are presented for the first time based on the analysis of BOSB production technologies and processes requirements. Component of BOSB medium experimental line and key equipments stated.The paper illustrated BOSB flaker,glue blender,orienting former.Then medium experimental line is given to a great deal of test run and optimization.The tests indicated that the medium experimental line operated smoothly for producing BOSB.Tested BOSB key performance indicators were higher than the LY/T 1580 - 2000(OSB /4).展开更多
基金financial supports from the National Natural Science Foundation of China (No. 51875062)China Postdoctoral Science Foundation (No. 2021M700567)。
文摘In this study,HEA/AI composite interlayer was used to fabricate Ti/Mg bimetal composites by solidliquid compound casting process.The Al layer was prepared on the surface of TC4 alloy by hot dipping,and the FeCoNiCr HEA layer was prepared by magnetron sputtering onto the Al layer.The influence of the HEA layer thickness and pouring temperature on interface evolution was investigated based on SEM observation and thermodynamic analysis.Results indicate that the sluggish diffusion effect of HEA can effectively inhibit the interfacial diffusion between Al and Mg,which is conducive to the formation of solid solution,especially when the thickness of HEA is 800 nm.With the increase of casting temperature from 720 ℃ to 730 ℃,740℃,and 750 ℃,α-Al(Mg),α-Al(Mg)+Al3Mg2,Al3Mg2+Al12Mg17,and Al12Mg17+δ-Mg are formed at the interface of Ti/Mg bimetal,respectively.When the thickness of the HEA layer is 800 nm and the pouring temperature is 720 ℃,the bonding strength of the Ti/Mg bimetal can reach the maximum of 93.6 MPa.
基金Project(50336040) supported by the National Natural Science Foundation of China
文摘The Cd1-xZnxTe(CZT) single crystals were annealed by a two-step method including a vapor-environment step and a liquid-environment step in sequence. The effects of annealing on the properties of CZT were analyzed in detail. IR transmission measurement results show that IR transmission of CZT is improved dramatically after annealing. X-ray rocking curves indicate that the annealing treatment ameliorates crystal quality obviously, which is ascribed to the release of residual stress and the reduction of point defects. Photoluminescence(PL) spectra reveal that the full width at half maximum(FWHM) of the donor-bound exciton (D0, X) peak is reduced obviously, and the free exciton emission is weakened after annealing. Meanwhile, the intensity of the donor-acceptor pair(DAP) peak decreases to a great degree, which implies that the impurities are removed from CZT wafers. In addition, the deep defect-related emission band Dcomplex disappears after annealing, which mean that Cd vacancies are well-compensated. The results confirm that the two-step annealing is an effective approach to improve the qualities of CZT single crystals.
基金supported by the National Natural Science Foundation of China(Grants 51476152,11302213,and 11572336)
文摘An efficient high-order numerical method for supersonic reactive flows is proposed in this article.The reactive source term and convection term are solved separately by splitting scheme.In the reaction step,an adaptive time-step method is presented,which can improve the efficiency greatly.In the convection step,a third-order accurate weighted essentially non-oscillatory(WENO)method is adopted to reconstruct the solution in the unstructured grids.Numerical results show that our new method can capture the correct propagation speed of the detonation wave exactly even in coarse grids,while high order accuracy can be achieved in the smooth region.In addition,the proposed adaptive splitting method can reduce the computational cost greatly compared with the traditional splitting method.
文摘A fault tolerant control method is proposed in this paper for a turbofan engine gas path degradation through the full flight envelope. A Quantum-behaved Particle Swarm Optimization(QPSO) algorithm is applied to obtain engine inputs adjustments, which contribute to construct off-line performance accommodation interpolation schedules. With a double closed-loop control system structure, command control is corrected based on real-time fault diagnostic results. Simulations indicate that fault tolerant control could reduce thrust and stall margin loss effectively in gas path faults.
基金co-supported by the Open Fund of Key Laboratory of Power Research of China(No.2017-Ⅲ-0005-0029)the National Natural Science Foundation of China(No.51776167).
文摘Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally studied for supercritical fluids. Two types of flow excursion occur in a single tube. Type Ⅰ and Type Ⅱ excursions, and they are corresponding to decreasing and increasing flow rate respectively. They can trigger flow maldistribution between parallel tubes and the hysteresis phenomenon of flow distribution. The effects of system parameters, including inlet temperature,system pressure, and heat flux, on flow distribution were analyzed. In addition, the relationship between flow excursion and the pseudo-critical interval proposed in the literature was established according to the heated tube outlet temperature at the onset of flow instability. Finally, the flow excursion instability boundary was obtained using two dimensionless parameters. These experimental results can provide helpful insight on the mechanism of Scramjet regenerative cooling.
基金the National Natural Science Foundation of China (Grant Nos.51275135,51105107 and 51021002)the Natural Science Foundation of Heilongjiang Province,China (Grant No.QC2011C044)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No.20112302130005)
文摘Al2O3 and Ti-6Al-4V alloy were brazed with Ag-Cu-Ti +B fillers in different brazing conditions. Effects of brazing temperature, holding time and additive Ti content on joints microstructure and shear strength were investigated by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, transmission electron microscopy and shear testing. Results indicate that TiCu and Ti(Cu,Al) decrease, but Ti2Cu and -Ti2(Cu,Al) increase in brazing seam with increasing brazing temperature, holding time and additive Ti content. Area consisting of Ti3(Cu,Al)30 and TiO near Al2O3 becomes gradually discontinuous from continuity when brazing temperature rises or holding time extends. As Ti additive content increases, TiO is absent near Al2O3, area consisting of only Ti3(Cu,Al)30 thickens. TiB whiskers are in situ synthesized by Ti and B atoms during brazing process. The brazing temperature, holding time and additive Ti content on joints microstructure influence the joints shear strength directly. The shear strength of joints, obtained at 850 ℃ holding for 10 min, reaches the maximum of 78 MPa. According to the experimental results, phase diagram and thermodynamics calculation, the interface evolution mechanism of the Al2O3/Ti-6Al-4V alloy joint was analyzed.
基金supported by the National Natural Science Foundation of China (Grant No. 51176087)
文摘The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×10 5 to 2.96×10 5 . The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioration of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer separation flow is severe. The interaction between boundary layer separation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.
文摘Bamboo OSB(BOSB) medium experimental line and key equipments are presented for the first time based on the analysis of BOSB production technologies and processes requirements. Component of BOSB medium experimental line and key equipments stated.The paper illustrated BOSB flaker,glue blender,orienting former.Then medium experimental line is given to a great deal of test run and optimization.The tests indicated that the medium experimental line operated smoothly for producing BOSB.Tested BOSB key performance indicators were higher than the LY/T 1580 - 2000(OSB /4).