In order to apply a swirling jet to a PDC drill bit, the nozzle performance influenced by nozzle inlet geometric parameters and rock breaking tests under submerged conditions were studied. Numerical simulation was use...In order to apply a swirling jet to a PDC drill bit, the nozzle performance influenced by nozzle inlet geometric parameters and rock breaking tests under submerged conditions were studied. Numerical simulation was used to study the influence of the nozzle structure on the swirling intensity and nozzle discharge coefficient. Simulation results indicate that spreading angle of the swirling jet is greater than that of＂ the non-swirling jet, and the swirling intensity of the jet is strongly influenced by the length of the nozzle body but weakly by the number of tangential inlets. Rock breaking tests were conducted to evaluate the performance of the swirling jet. It is found that the swirling jet shows a lower threshold pressure to break the rock samples and could break rock more efficiently compared with the non-swirling jet.展开更多
In this paper, to simulate the arc motion in an air circuit breaker （ACB）, a three- dimensional magneto-hydrodynamic （MHD） model is developed, considering the influence of ther- mal radiation, the change of physic...In this paper, to simulate the arc motion in an air circuit breaker （ACB）, a three- dimensional magneto-hydrodynamic （MHD） model is developed, considering the influence of ther- mal radiation, the change of physical parameters of arc plasma and the nonlinear characteristic of ferromagnetic material. The distributions of pressure, temperature, gas flow and current density of arc plasma in the arc region are calculated. The simulation results show some phenomena which discourage arc interruption, such as back commutation and arc burning at the back of the splitter plate. To verify the simulation model, the arc motion is studied experimentally. The influences of the material and position of the innermost barrier plate are analyzed mainly. It proved that the model developed in this paper can efficiently simulate the arc motion. The results indicate that the insulation barrier plate close to the top of the splitter plate is conducive to the arc splitting, which leads to the significant increase of the arc voltage, so it is better for arc interruption. The research can provide methods and references to the optimization of ACB design.展开更多
基金financial support from the Fundamental Research Funds for the Central Universities and the Natural Science Foundation of China (51179201)
文摘In order to apply a swirling jet to a PDC drill bit, the nozzle performance influenced by nozzle inlet geometric parameters and rock breaking tests under submerged conditions were studied. Numerical simulation was used to study the influence of the nozzle structure on the swirling intensity and nozzle discharge coefficient. Simulation results indicate that spreading angle of the swirling jet is greater than that of＂ the non-swirling jet, and the swirling intensity of the jet is strongly influenced by the length of the nozzle body but weakly by the number of tangential inlets. Rock breaking tests were conducted to evaluate the performance of the swirling jet. It is found that the swirling jet shows a lower threshold pressure to break the rock samples and could break rock more efficiently compared with the non-swirling jet.
基金supported by National Key Basic Research Program of China (973 Program) (Nos.2015CB251002,6132620303)National Natural Science Foundation of China (Nos.51221005,51377128,51577144)the Fundamental Research Funds for the Central Universities,China
文摘In this paper, to simulate the arc motion in an air circuit breaker （ACB）, a three- dimensional magneto-hydrodynamic （MHD） model is developed, considering the influence of ther- mal radiation, the change of physical parameters of arc plasma and the nonlinear characteristic of ferromagnetic material. The distributions of pressure, temperature, gas flow and current density of arc plasma in the arc region are calculated. The simulation results show some phenomena which discourage arc interruption, such as back commutation and arc burning at the back of the splitter plate. To verify the simulation model, the arc motion is studied experimentally. The influences of the material and position of the innermost barrier plate are analyzed mainly. It proved that the model developed in this paper can efficiently simulate the arc motion. The results indicate that the insulation barrier plate close to the top of the splitter plate is conducive to the arc splitting, which leads to the significant increase of the arc voltage, so it is better for arc interruption. The research can provide methods and references to the optimization of ACB design.
