It is well known that quackgrass is both very aggressive and persistent. In agriculture, many attempts have been made to eliminate this weed without success. Within the context of a sustainable agriculture, mechanical...It is well known that quackgrass is both very aggressive and persistent. In agriculture, many attempts have been made to eliminate this weed without success. Within the context of a sustainable agriculture, mechanical control of quackgrass represents an interesting alternative to chemical means. The use of a ＂C＂ shaped mounted tine cultivator, a rotary cross-harrow, and an ＂S＂ shaped trailed tine cultivator （alone or in combination） to control quackgrass in grassland was investigated. The rate of quackgrass present in each experimental plot was determined before and after the treatments using a one square meter quadrant. Also, the time required for each passage as well as the fuel consumption were computed. Results revealed that the fuel consumption and the time required by the ＂C＂ and ＂S＂ shaped tine cultivators to transport and expose the rhizomes to the sun on the soil surface highly depend on the quality of tillage during the first stubble passage. Also, subsequent tillage with the ＂C＂ shaped tine cultivator after a first passage with a rotary cross-harrow resulted in less fuel consumption and passage time. On the other hand, stubble and subsequent soil tillage with only the ＂C＂ shaped tine cultivator is the least successful method.展开更多
This study carried out full-scale gas water heater combustion experiments and adopted FDS （fire dynamics simulator） to simulate three scenarios--different balcony environments when using water heater, such as airtig...This study carried out full-scale gas water heater combustion experiments and adopted FDS （fire dynamics simulator） to simulate three scenarios--different balcony environments when using water heater, such as airtight balcony, indoor door with openings and force ventilation to compare with full-scale combustion experiments. According to FDS simulation results, 02, CO and CO2 simulation concentration value correspond with full-scale experimental results. When the indoor O2 concentration was lower than 15%, which causes incomplete combustion, the CO concentration would rise rapidly and even reached above 1,500 ppm, causing death in short time. In addition, when the force ventilation model supplied the water heater with enough air to bum, the indoor CO concentration will keep low and harmless to humans. The study also adopted diverse variables, such as the opening area of window, outdoor wind speed and water heater types, to analyze deeply user＇s safety regarding gas water heater. In a result, while balcony area is larger than 14 mE, the volume of water heater is below 16 L （33.1 kW）, and the indoor window, connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is larger than 0.2 mE, this can ensure the personal security of the indoor space.展开更多
Spray structure and atomization characteristics were investigated through a comparison of a porous and a shear coaxial injector. The porous injector shows better atomization performance than the shear coaxial injector...Spray structure and atomization characteristics were investigated through a comparison of a porous and a shear coaxial injector. The porous injector shows better atomization performance than the shear coaxial injector. To in- crease atomization performance and mixing efficiency of two-phase jets, a coaxial porous injector which can be applicable to liquid rocket combustors was designed and tested. The characteristics of atomization and spray from a porous and a shear coaxial injector were characterized by the momentum flux ratio. The breakup mechanism of the porous injector is governed by Taylor-Culick flow and axial shear forces. Momentum of injected gas flow through a porous material which is composed of sintered metal is radically transferred to the center of the liquid column, and then liquid column is effectively broken up. Although the shapes of spray from porous and shear co- axial jets were similar for various momentum ratio, spray structures such as spray angle and droplet sizes were different. As increasing the momentum flux ratio, SMD from the porous injector showed smaller value than the shear coaxial injector展开更多
Steam channeling is one of the main barriers for EOR after steam flooding.In order to enhance the oil recovery in steam flooded reservoirs,steam channel volumes should be precisely known.In this paper,a set of methods...Steam channeling is one of the main barriers for EOR after steam flooding.In order to enhance the oil recovery in steam flooded reservoirs,steam channel volumes should be precisely known.In this paper,a set of methods has been established in order to study steam channeling quantitatively by using dynamic data.Firstly,steam channeling wells are identified through curves of watercut and temperature.Then,considering the hysteresis phenomenon,channeling relations are identified with the correlation coefficients between injection wells and production wells under different conditions.Lastly,an analytic model,in which steam condensation,pressure and temperature are considered,is established to calculate the steam channel volumes.A production well named L31615 in some block in Henan Oilfield in China is systematically analyzed by using the method established.The whole block is further analyzed,and the distribution map of steam channels and the steam channel volumes are obtained.The results show that steam channeling does not only occur inside a well group,but also sometimes occurs between wells in different well groups.The calculation of the steam channel volumes provides a theoretical basis for bringing a remedial action like plugging into operation.展开更多
文摘It is well known that quackgrass is both very aggressive and persistent. In agriculture, many attempts have been made to eliminate this weed without success. Within the context of a sustainable agriculture, mechanical control of quackgrass represents an interesting alternative to chemical means. The use of a ＂C＂ shaped mounted tine cultivator, a rotary cross-harrow, and an ＂S＂ shaped trailed tine cultivator （alone or in combination） to control quackgrass in grassland was investigated. The rate of quackgrass present in each experimental plot was determined before and after the treatments using a one square meter quadrant. Also, the time required for each passage as well as the fuel consumption were computed. Results revealed that the fuel consumption and the time required by the ＂C＂ and ＂S＂ shaped tine cultivators to transport and expose the rhizomes to the sun on the soil surface highly depend on the quality of tillage during the first stubble passage. Also, subsequent tillage with the ＂C＂ shaped tine cultivator after a first passage with a rotary cross-harrow resulted in less fuel consumption and passage time. On the other hand, stubble and subsequent soil tillage with only the ＂C＂ shaped tine cultivator is the least successful method.
文摘This study carried out full-scale gas water heater combustion experiments and adopted FDS （fire dynamics simulator） to simulate three scenarios--different balcony environments when using water heater, such as airtight balcony, indoor door with openings and force ventilation to compare with full-scale combustion experiments. According to FDS simulation results, 02, CO and CO2 simulation concentration value correspond with full-scale experimental results. When the indoor O2 concentration was lower than 15%, which causes incomplete combustion, the CO concentration would rise rapidly and even reached above 1,500 ppm, causing death in short time. In addition, when the force ventilation model supplied the water heater with enough air to bum, the indoor CO concentration will keep low and harmless to humans. The study also adopted diverse variables, such as the opening area of window, outdoor wind speed and water heater types, to analyze deeply user＇s safety regarding gas water heater. In a result, while balcony area is larger than 14 mE, the volume of water heater is below 16 L （33.1 kW）, and the indoor window, connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is larger than 0.2 mE, this can ensure the personal security of the indoor space.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean Government(MEST)(NRF-2011-0015435 and NRF-2012M 1A3A3A02033146)
文摘Spray structure and atomization characteristics were investigated through a comparison of a porous and a shear coaxial injector. The porous injector shows better atomization performance than the shear coaxial injector. To in- crease atomization performance and mixing efficiency of two-phase jets, a coaxial porous injector which can be applicable to liquid rocket combustors was designed and tested. The characteristics of atomization and spray from a porous and a shear coaxial injector were characterized by the momentum flux ratio. The breakup mechanism of the porous injector is governed by Taylor-Culick flow and axial shear forces. Momentum of injected gas flow through a porous material which is composed of sintered metal is radically transferred to the center of the liquid column, and then liquid column is effectively broken up. Although the shapes of spray from porous and shear co- axial jets were similar for various momentum ratio, spray structures such as spray angle and droplet sizes were different. As increasing the momentum flux ratio, SMD from the porous injector showed smaller value than the shear coaxial injector
基金supported by China National Science and Technology Major Project(Grant No.2011ZX05009-004-05)the National Natural Science Foundation of China(Grant No.51274212)
文摘Steam channeling is one of the main barriers for EOR after steam flooding.In order to enhance the oil recovery in steam flooded reservoirs,steam channel volumes should be precisely known.In this paper,a set of methods has been established in order to study steam channeling quantitatively by using dynamic data.Firstly,steam channeling wells are identified through curves of watercut and temperature.Then,considering the hysteresis phenomenon,channeling relations are identified with the correlation coefficients between injection wells and production wells under different conditions.Lastly,an analytic model,in which steam condensation,pressure and temperature are considered,is established to calculate the steam channel volumes.A production well named L31615 in some block in Henan Oilfield in China is systematically analyzed by using the method established.The whole block is further analyzed,and the distribution map of steam channels and the steam channel volumes are obtained.The results show that steam channeling does not only occur inside a well group,but also sometimes occurs between wells in different well groups.The calculation of the steam channel volumes provides a theoretical basis for bringing a remedial action like plugging into operation.
