Low-temperature thermal energy conversions down to exergy zero to electric power must contribute energy sustainability. That is to say, reinforcements of power harvesting technologies from extremely low temperatures l...Low-temperature thermal energy conversions down to exergy zero to electric power must contribute energy sustainability. That is to say, reinforcements of power harvesting technologies from extremely low temperatures less than 373 K might be at least one of minimum roles for the current generations. Then, piezoelectric power harvesting process for recovering low-temperature heats was invented by using a unique biphasic operating medium of an underlying water-insoluble/low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) in small quantity and upper-layered water in large quantity. The higher piezoelectric power harvesting densities were naturally revealed with an increase in heating temperatures. Excessive cooling of the operating medium deteriorated the power harvesting efficiency. The denser operating medium was surpassingly helpful to the higher piezoelectric power harvesting density. Concretely, only about 5% density increase of main operating medium (i.e. water with dissolving alum at 0.10 mol/dm3) came to the champion piezoelectric power harvesting density of 92.6 pW/dm2 in this study, which was about 1.4 times compared to that with the original biphasic medium of pure water together with a small quantity of NOVEC.展开更多
The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% -...The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% - 80% have been studied by hot compressing testing. The microstructures of TC17 alloy were observed and analyzed using Olympus/PMG3 optical microscope. The flow stresses were correlated with strain rate and the temperature by the constitutive equation. The results show that the flow stress of TC17 alloy increase quickly with the strain, then decrease with a steady value. The deformation activation energy obtained in the α + β region for TC17 was 407 kJ/mol, and in the β region was 155 kJ/mol. It was also found that the degree of dynamic globularization of α phase increases with increasing strains, increasing temperature and decreasing strain rate in α + β region, the dynamic re-crystallization is obvious at low strain rate and dynamic recovery is obvious at high strain rate in β region.展开更多
In order to obtain the combustion characteristics of the CH4/Air premixed flame under the action of the wall interaction,a study on the impact of the jet flame on the wall at different separation distances was carried...In order to obtain the combustion characteristics of the CH4/Air premixed flame under the action of the wall interaction,a study on the impact of the jet flame on the wall at different separation distances was carried out.The separation distance from the burner outlet to the lower surface of the wall is changed and the flame structure is obtained through experiments.The temperature,velocity and reaction rate are obtained through numerical simulation,and the law of flame characteristics change is obtained through analysis.The results show that as the separation distance increases,the premixing cone inside the flame gradually changes from a horn shape to a complete cone shape and the length of the premixing cone profile increases.Also,the peak temperature and velocity of the mixture in the axial direction gradually increase,and the temperature and velocity in the radial direction first increase and then decrease.The temperature gradient and velocity reach the maximum when the separation distance is 11 mm.The peaks of reactants(CH_(4))net reaction rate intermediate products(CO)and products(CO_(2),H_(2)O)on the axis and the axial distance corresponding to the peaks increase accordingly.The chemical reaction rate near the wall also gradually decreases with the increase of the separation distance.展开更多
Previous works on impinging streams mainly focused on the structures of flow field,but paid less attention to the structures of temperature field,which are very important in practical applications.In this paper,the in...Previous works on impinging streams mainly focused on the structures of flow field,but paid less attention to the structures of temperature field,which are very important in practical applications.In this paper,the influences of the Reynolds number(Re)and Prandtl number(Pr)on the structures of flow and temperature fields of non-isothermal laminar impinging streams are both studied numerically with the lattice Boltzmann method,and two cases with and without buoyancy effect are considered.Numerical results show that the structures are quite different in these cases.Moreover,in the case with buoyancy effect,some new deflection and periodic structures are found,and their independence on the outlet boundary condition is also verified.These findings may help to understand the flow and temperature structures of non-isothermal impinging streams further.展开更多
The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and producti...The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag.The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation.The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied.Depending on the melting mechanism of melt-dissolution,the melting time of fine slags is short.Three fine slags all produce glassy slags,which is conducive to slag discharge.The degree of polymerization of silicate melt is proportionate to the amount of SiO_(2)in the slag.A part of Al^(3+)exist in the form of[AlO_(4)]^(5-)because of the effect of CaO and Na_(2)O,as the network former.Finally,the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one.展开更多
文摘Low-temperature thermal energy conversions down to exergy zero to electric power must contribute energy sustainability. That is to say, reinforcements of power harvesting technologies from extremely low temperatures less than 373 K might be at least one of minimum roles for the current generations. Then, piezoelectric power harvesting process for recovering low-temperature heats was invented by using a unique biphasic operating medium of an underlying water-insoluble/low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) in small quantity and upper-layered water in large quantity. The higher piezoelectric power harvesting densities were naturally revealed with an increase in heating temperatures. Excessive cooling of the operating medium deteriorated the power harvesting efficiency. The denser operating medium was surpassingly helpful to the higher piezoelectric power harvesting density. Concretely, only about 5% density increase of main operating medium (i.e. water with dissolving alum at 0.10 mol/dm3) came to the champion piezoelectric power harvesting density of 92.6 pW/dm2 in this study, which was about 1.4 times compared to that with the original biphasic medium of pure water together with a small quantity of NOVEC.
文摘The high temperature deformation behavior and microstructures evolution of TC17 alloy in the temperature range of 820°C - 930°C, strain rate range of 0.01 s-1 - 10 s-1 and height direction reduction of 20% - 80% have been studied by hot compressing testing. The microstructures of TC17 alloy were observed and analyzed using Olympus/PMG3 optical microscope. The flow stresses were correlated with strain rate and the temperature by the constitutive equation. The results show that the flow stress of TC17 alloy increase quickly with the strain, then decrease with a steady value. The deformation activation energy obtained in the α + β region for TC17 was 407 kJ/mol, and in the β region was 155 kJ/mol. It was also found that the degree of dynamic globularization of α phase increases with increasing strains, increasing temperature and decreasing strain rate in α + β region, the dynamic re-crystallization is obvious at low strain rate and dynamic recovery is obvious at high strain rate in β region.
基金supported by the National Natural Science Foundation of China(Grant No.51976082)and Qing Lan project.
文摘In order to obtain the combustion characteristics of the CH4/Air premixed flame under the action of the wall interaction,a study on the impact of the jet flame on the wall at different separation distances was carried out.The separation distance from the burner outlet to the lower surface of the wall is changed and the flame structure is obtained through experiments.The temperature,velocity and reaction rate are obtained through numerical simulation,and the law of flame characteristics change is obtained through analysis.The results show that as the separation distance increases,the premixing cone inside the flame gradually changes from a horn shape to a complete cone shape and the length of the premixing cone profile increases.Also,the peak temperature and velocity of the mixture in the axial direction gradually increase,and the temperature and velocity in the radial direction first increase and then decrease.The temperature gradient and velocity reach the maximum when the separation distance is 11 mm.The peaks of reactants(CH_(4))net reaction rate intermediate products(CO)and products(CO_(2),H_(2)O)on the axis and the axial distance corresponding to the peaks increase accordingly.The chemical reaction rate near the wall also gradually decreases with the increase of the separation distance.
基金supported by National Natural Science Foundation of China(Grant Nos.51006040,51006039)the Fundamental Research Funds for the Central Universities,HUST(Grant Nos.2010JC005,2010MS131 and 2010QN057).
文摘Previous works on impinging streams mainly focused on the structures of flow field,but paid less attention to the structures of temperature field,which are very important in practical applications.In this paper,the influences of the Reynolds number(Re)and Prandtl number(Pr)on the structures of flow and temperature fields of non-isothermal laminar impinging streams are both studied numerically with the lattice Boltzmann method,and two cases with and without buoyancy effect are considered.Numerical results show that the structures are quite different in these cases.Moreover,in the case with buoyancy effect,some new deflection and periodic structures are found,and their independence on the outlet boundary condition is also verified.These findings may help to understand the flow and temperature structures of non-isothermal impinging streams further.
基金financially supported by Class A Strategic Pilot Science and Technology Project,Chinese Academy of Sciences(Grant No.XDA21040602)the National Natural Science Foundation of China(Grant No.U1810127)the Youth Innovation Promotion Association,Chinese Academy of Science(Grant No.Y201932)。
文摘The entrained flow gasification has been identified as the most promising gasification technology.Serious environmental pollution and waste of land resources are caused by the increasing amount of storage and production of coal gasification slag.The aim of this work is to explore the feasibility of high-temperature combustion and melting technology for treating coal gasification fine slag and determine the important parameters of system operation.The flow properties and molten slag structure characteristics of three fine slags from different entrained flow gasifiers were studied.Depending on the melting mechanism of melt-dissolution,the melting time of fine slags is short.Three fine slags all produce glassy slags,which is conducive to slag discharge.The degree of polymerization of silicate melt is proportionate to the amount of SiO_(2)in the slag.A part of Al^(3+)exist in the form of[AlO_(4)]^(5-)because of the effect of CaO and Na_(2)O,as the network former.Finally,the degree of polymerization of the three type molten slag was calculated by considering the role of Si and Al in molten slag and the property of each one.
