Sundial solar tracking machines are machines that tracking the sun,and can promote sunshine receiving efficiency of solar panels.Their operations are strongly influenced by wind load.Previous studies were focused on t...Sundial solar tracking machines are machines that tracking the sun,and can promote sunshine receiving efficiency of solar panels.Their operations are strongly influenced by wind load.Previous studies were focused on tracking accuracy and tracking methods,the influence of wind load to the operation of the tracking machines has not caused enough attention,so that many tracking machines did not have the reasonable design basis,which led to unreasonable design and high maintenance costs,and had seriously influenced the application and popularization of the tracking machines.Therefore,the 16 m2 sundial solar tracking machine is taken as research object from the perspective of wind load.A series of computational fluid dynamics（CFD） analyses are carried out on the model of the 16 m2 sundial solar tracking machine.Firstly,in order to make CFD analyses carry on smoothly,after the three-dimensional solid model is established,the model is simplified,and grids are meshed on the simplified model.Then,in the virtual environment,to make the simulation closer to real but at the same time not too complex to make simulation hard to realize,assumptions of the nature of air flow are conducted,boundary conditions of the analyses are set reasonably,and appropriate CFD analysis solver is also chosen.Finally,the results of the CFD analyses are also analyzed and sorted;and limit requirements（i.e.,force conditions of limit case）,such as the maximum load and the maximum total torque,are provided for the further finite element analyses（FEA） and the optimization design of the products.This paper presents an effective computer simulation analysis method for the design and optimization of this type of solar tracking machine,and this method can greatly shorten the development cycle and cost.展开更多
Sediment-hosted hydrate reservoir often contains saturated pore fluid, which changes the heat transfer and mass transfer characteristics of the hydrate reservoir. The exploitation of hydrate under saturated pore fluid...Sediment-hosted hydrate reservoir often contains saturated pore fluid, which changes the heat transfer and mass transfer characteristics of the hydrate reservoir. The exploitation of hydrate under saturated pore fluid using depressurization is simulated experimentally to investigate the influence of particle size of porous media, dissociation temperature, pressure drop and injected fluid type on gas production behavior. Homogeneous methane hydrate was firstly formed in frozen quartz sand. With the formed hydrate sample, hydrate dissociation experiments by depressurization were conducted. The test results showed that the gas production rate of hydrate under saturated pore fluid was substantially influenced by the particle size, the pressure drop and the injected fluid type, while it was influenced little by the dissociation temperature. The hydrate dissociates faster under larger pressure drop and in the presence of smaller porous media within the experimental region. The dissociation rate increases with an increasing fluid salinity in the initial stage, while it decreases in the later stage. The increase of gas diffusion resistance resulted from ionic hydration atmosphere in saturated chloride solution impeded the dissociation of hydrate. It can be solved by increasing the pressure drop and decreasing the fluid salinity in the process of gas recovery from hydrate reservoir.展开更多
Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining,which could promote further decomposition and expand mining areas of gas hydrate. St...Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining,which could promote further decomposition and expand mining areas of gas hydrate. Steam heat calculation would provide the basis for the design of heating device and the choice of the field test parameters. There were piping heat loss in the process of mining. The heat transfer of steam flowing in the pipe was steady,so the heat loss could be obtained easily by formula calculation. The power of stratum heating should be determined by numerical simulation for the process of heating was dynamic and the equations were usually nonlinear. The selected mining conditions were 500-millimeter mining radius,10 centigrade mining temperature and 180 centigrade steam temperature. Heat loss and best heating power,obtained by formula calculation and numerical simulation,were 21. 35 W/m and 20 kW.展开更多
The Mohe permafrost in northeast China possesses favorable subsurface ambient temperature, salinity, Eh values and pH levels of groundwater for the formation of microbial gas, and the Mohe Basin contains rich organic ...The Mohe permafrost in northeast China possesses favorable subsurface ambient temperature, salinity, Eh values and pH levels of groundwater for the formation of microbial gas, and the Mohe Basin contains rich organic matter in the Middle Jurassic dark mudstones. This work conducted gas chromatography and isotope mass spectrometry analyses of nearly 90 core gas samples from the Mk-2 well in the Mohe Basin. The results show that the dryness coefficient(C1/C1–5) of core hydrocarbon gas from approximately 900 m intervals below the surface is larger than 98%, over 70% of the δ13 C values of methane are smaller than-55‰, and almost all δD values of methane are smaller than-250‰, indicative of a microbial origin of the gas from almost 900 m of the upper intervals in the Mohe permafrost. Moreover, the biomarker analyses of 72 mudstone samples from the Mohe area indicate that all of them contain 25-norhopane series compounds, thereby suggesting widely distributed microbial activities in the permafrost. This work has confirmed the prevailing existence of microbial gas in the Mohe area, which may be a potential gas source of gas hydrate formation in the Mohe permafrost. This result is of great significance to gas hydrate accumulation in the permafrost across China.展开更多
基金supported by the Second Stage of Jilin University "985"Project-Northeast Resources and Environment Technology Innovation Platform of China (Grant No. 450070021107)
文摘Sundial solar tracking machines are machines that tracking the sun,and can promote sunshine receiving efficiency of solar panels.Their operations are strongly influenced by wind load.Previous studies were focused on tracking accuracy and tracking methods,the influence of wind load to the operation of the tracking machines has not caused enough attention,so that many tracking machines did not have the reasonable design basis,which led to unreasonable design and high maintenance costs,and had seriously influenced the application and popularization of the tracking machines.Therefore,the 16 m2 sundial solar tracking machine is taken as research object from the perspective of wind load.A series of computational fluid dynamics（CFD） analyses are carried out on the model of the 16 m2 sundial solar tracking machine.Firstly,in order to make CFD analyses carry on smoothly,after the three-dimensional solid model is established,the model is simplified,and grids are meshed on the simplified model.Then,in the virtual environment,to make the simulation closer to real but at the same time not too complex to make simulation hard to realize,assumptions of the nature of air flow are conducted,boundary conditions of the analyses are set reasonably,and appropriate CFD analysis solver is also chosen.Finally,the results of the CFD analyses are also analyzed and sorted;and limit requirements（i.e.,force conditions of limit case）,such as the maximum load and the maximum total torque,are provided for the further finite element analyses（FEA） and the optimization design of the products.This paper presents an effective computer simulation analysis method for the design and optimization of this type of solar tracking machine,and this method can greatly shorten the development cycle and cost.
基金supported by the National Natural Science Foundation of China(Grant No.51304079,Grant No.51474112,Grant No.41502343 and Grant No.51506073)
文摘Sediment-hosted hydrate reservoir often contains saturated pore fluid, which changes the heat transfer and mass transfer characteristics of the hydrate reservoir. The exploitation of hydrate under saturated pore fluid using depressurization is simulated experimentally to investigate the influence of particle size of porous media, dissociation temperature, pressure drop and injected fluid type on gas production behavior. Homogeneous methane hydrate was firstly formed in frozen quartz sand. With the formed hydrate sample, hydrate dissociation experiments by depressurization were conducted. The test results showed that the gas production rate of hydrate under saturated pore fluid was substantially influenced by the particle size, the pressure drop and the injected fluid type, while it was influenced little by the dissociation temperature. The hydrate dissociates faster under larger pressure drop and in the presence of smaller porous media within the experimental region. The dissociation rate increases with an increasing fluid salinity in the initial stage, while it decreases in the later stage. The increase of gas diffusion resistance resulted from ionic hydration atmosphere in saturated chloride solution impeded the dissociation of hydrate. It can be solved by increasing the pressure drop and decreasing the fluid salinity in the process of gas recovery from hydrate reservoir.
基金Supported by project of China Geological Surrey(No.GZHL20110326)
文摘Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the same time of depressurization mining,which could promote further decomposition and expand mining areas of gas hydrate. Steam heat calculation would provide the basis for the design of heating device and the choice of the field test parameters. There were piping heat loss in the process of mining. The heat transfer of steam flowing in the pipe was steady,so the heat loss could be obtained easily by formula calculation. The power of stratum heating should be determined by numerical simulation for the process of heating was dynamic and the equations were usually nonlinear. The selected mining conditions were 500-millimeter mining radius,10 centigrade mining temperature and 180 centigrade steam temperature. Heat loss and best heating power,obtained by formula calculation and numerical simulation,were 21. 35 W/m and 20 kW.
基金supported by Prospecting and Testing Production Project of Gas Hydrate resources, Ministry of Land and Resources of China (grants No. GZHL20110317, GZHL20110320, GZHL20110322)
文摘The Mohe permafrost in northeast China possesses favorable subsurface ambient temperature, salinity, Eh values and pH levels of groundwater for the formation of microbial gas, and the Mohe Basin contains rich organic matter in the Middle Jurassic dark mudstones. This work conducted gas chromatography and isotope mass spectrometry analyses of nearly 90 core gas samples from the Mk-2 well in the Mohe Basin. The results show that the dryness coefficient(C1/C1–5) of core hydrocarbon gas from approximately 900 m intervals below the surface is larger than 98%, over 70% of the δ13 C values of methane are smaller than-55‰, and almost all δD values of methane are smaller than-250‰, indicative of a microbial origin of the gas from almost 900 m of the upper intervals in the Mohe permafrost. Moreover, the biomarker analyses of 72 mudstone samples from the Mohe area indicate that all of them contain 25-norhopane series compounds, thereby suggesting widely distributed microbial activities in the permafrost. This work has confirmed the prevailing existence of microbial gas in the Mohe area, which may be a potential gas source of gas hydrate formation in the Mohe permafrost. This result is of great significance to gas hydrate accumulation in the permafrost across China.
