The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine ...The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine adopts various cooling techniques to ensure cooling,including a metal thermal barrier coating,multiple liquid film cooling slots,spiral milled regenerative cooling channels with high aspect ratio,a non-weld forming thrust chamber and an optimal cooling flow path design.In addition,the 480-ton LOX/kerosene engine for China’s future heavy-lift launch vehicle LM-9 will be larger in size,which makes it more difficult to be developed and will have more strict requirements in the cooling process.The main differences between the LM-5B and LM-5 are briefly described in this paper and the development process and working characteristics of YF-100 engines are introduced.The advantages and disadvantages of main cooling methods used in the thrust chambers of high-thrust liquid propellant engines are also described.Finally,the future challenges and countermeasures in cooling technology for China’s high-thrust LOX/kerosene engines and future reusable rocket engines are also presented.展开更多
The ultra-fast cooling technology of large section bars and the microstrueture for different cooling patterns were studied by optical microscope, transmission electron microscope and energy spectrometer. The results i...The ultra-fast cooling technology of large section bars and the microstrueture for different cooling patterns were studied by optical microscope, transmission electron microscope and energy spectrometer. The results indicated that the large section bars were passed through the zone of secondary carbide precipitation quickly by ultra-fast cooling technology （UFC） at instantaneous cooling rate of about 200 ℃/s and the finishing cooling temperature was higher than Ms. The lamellar spacing of pearlite decreased and the microhardness increased with decreasing the rereddening temperature. The precipitation of network carbide was restrained when re-reddening temperature was 690 ℃. And fine laminated pearlite was obtained through transformation of pseudopearlition that induced the reduction of the diameter of pearlite grain and refinement of the lamellar spacing of pearlite, so ideal microstructures of promoting spheroidizing annealing were obtained.展开更多
Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-tempera...Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.展开更多
When converting solar energy to electricity,a big proportion of energy is not converted for electricity but for heating PV cells,resulting in increased cell temperature and reduced electrical efficiency.Many cooling t...When converting solar energy to electricity,a big proportion of energy is not converted for electricity but for heating PV cells,resulting in increased cell temperature and reduced electrical efficiency.Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield.However,little crucial review work was proposed to comment cooling technologies for PV modules.Therefore,this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules,and given appropriate comments,comparisons and discussions.According to the ways or principles of cooling,existing cooling technologies have been classified as fluid medium cooling(air cooling,water cooling and nanofluids cooling),optimizing structural configuration cooling and phase change materials cooling.Potential influential factors and sub-methods were collected from the review work,and their contributions and impact have been discussed to guide future studies.Although most cooling technologies reviewed in this paper are matured,there are still problems need to be solved,such as the choice of cooling fluid and its usability for specific regions,the fouling accumulation and cleaning of enhanced heat exchangers with complex structures,the balance between cooling cost and net efficiency of PV modules,the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas.To be advocated,due to efficient heat transfer and spectral filter characters,nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization.展开更多
The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and ch...The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and chemical basics of external media that influence the mechanical processing of materials appeared, how these ideas explained the differences between traditional tribology and specific technology of metal processing are discussed. The question of the possible realization of Rehbinder＇s adsorption effect in contact zone is also stated. The description of a very captivating problem is related to the explanation of the mechanism of lubricant penetration into the contact zone between the material being processed and the tool. The birth and development of the hypothesis of microcapillary penetra- tion of the lubricant into the dynamically changed intersurface clearance that has finally led to formulating the ＂necessary kinetic condition of the lubricating activity＂ is relayed.展开更多
文摘The LM-5B launch vehicle has successfully completed four missions.Eight high-pressure staged combustion LOX/kerosene engines(YF-100)are equipped in the four boosters of the LM-5B,two in each booster.The YF-100 engine adopts various cooling techniques to ensure cooling,including a metal thermal barrier coating,multiple liquid film cooling slots,spiral milled regenerative cooling channels with high aspect ratio,a non-weld forming thrust chamber and an optimal cooling flow path design.In addition,the 480-ton LOX/kerosene engine for China’s future heavy-lift launch vehicle LM-9 will be larger in size,which makes it more difficult to be developed and will have more strict requirements in the cooling process.The main differences between the LM-5B and LM-5 are briefly described in this paper and the development process and working characteristics of YF-100 engines are introduced.The advantages and disadvantages of main cooling methods used in the thrust chambers of high-thrust liquid propellant engines are also described.Finally,the future challenges and countermeasures in cooling technology for China’s high-thrust LOX/kerosene engines and future reusable rocket engines are also presented.
基金Sponsored by National Natural Science Foundation of China(50334010)
文摘The ultra-fast cooling technology of large section bars and the microstrueture for different cooling patterns were studied by optical microscope, transmission electron microscope and energy spectrometer. The results indicated that the large section bars were passed through the zone of secondary carbide precipitation quickly by ultra-fast cooling technology （UFC） at instantaneous cooling rate of about 200 ℃/s and the finishing cooling temperature was higher than Ms. The lamellar spacing of pearlite decreased and the microhardness increased with decreasing the rereddening temperature. The precipitation of network carbide was restrained when re-reddening temperature was 690 ℃. And fine laminated pearlite was obtained through transformation of pseudopearlition that induced the reduction of the diameter of pearlite grain and refinement of the lamellar spacing of pearlite, so ideal microstructures of promoting spheroidizing annealing were obtained.
文摘Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.
基金The authors gratefully acknowledge the funding support from the National Key R&D Program of China(No.2017YFC0702900).
文摘When converting solar energy to electricity,a big proportion of energy is not converted for electricity but for heating PV cells,resulting in increased cell temperature and reduced electrical efficiency.Many cooling technologies have been developed and used for PV modules to lower cell temperature and boost electric energy yield.However,little crucial review work was proposed to comment cooling technologies for PV modules.Therefore,this paper has provided a thorough review of the up-to-date development of existing cooling technologies for PV modules,and given appropriate comments,comparisons and discussions.According to the ways or principles of cooling,existing cooling technologies have been classified as fluid medium cooling(air cooling,water cooling and nanofluids cooling),optimizing structural configuration cooling and phase change materials cooling.Potential influential factors and sub-methods were collected from the review work,and their contributions and impact have been discussed to guide future studies.Although most cooling technologies reviewed in this paper are matured,there are still problems need to be solved,such as the choice of cooling fluid and its usability for specific regions,the fouling accumulation and cleaning of enhanced heat exchangers with complex structures,the balance between cooling cost and net efficiency of PV modules,the cooling of circulating water in tropical areas and the freezing of circulating water in cold areas.To be advocated,due to efficient heat transfer and spectral filter characters,nanofluids can promote the effective matching of solar energy at both spectral and spatial scales to achieve orderly energy utilization.
文摘The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and chemical basics of external media that influence the mechanical processing of materials appeared, how these ideas explained the differences between traditional tribology and specific technology of metal processing are discussed. The question of the possible realization of Rehbinder＇s adsorption effect in contact zone is also stated. The description of a very captivating problem is related to the explanation of the mechanism of lubricant penetration into the contact zone between the material being processed and the tool. The birth and development of the hypothesis of microcapillary penetra- tion of the lubricant into the dynamically changed intersurface clearance that has finally led to formulating the ＂necessary kinetic condition of the lubricating activity＂ is relayed.
