The choice of the UHV lines depends on surface electric field of the bundle conductors.Based on existing calculation methods,the optimized charge simulation method is used to calculate the conductors' surface elec...The choice of the UHV lines depends on surface electric field of the bundle conductors.Based on existing calculation methods,the optimized charge simulation method is used to calculate the conductors' surface electrical field of±800 kV UHVDC transmission lines in this paper.During calculation,the offset distance is set as the variance of the objective function,the position and the quantity of the simulation charges are optimized with the gold section method,and the surface electrical field is calculated when the charge is in the optimal position.The result shows that the distribution of the surface electrical field and its maximal value can be calculated accurately with this method,although less number of simulation charges is used in this proposed method and the calculation is simple.展开更多
A one-dimensional pipe flow model of single-cylinder diesel engine is established to investigate the intake and exhaust flow characteristics of diesel engine in the condition of high power density(HPD).A space-lime co...A one-dimensional pipe flow model of single-cylinder diesel engine is established to investigate the intake and exhaust flow characteristics of diesel engine in the condition of high power density(HPD).A space-lime conservation element and solution element(CE/SE)method is used to derive the discrete equations of the partial differential equation for the intake and exhaust systems.The performance parameters of diesel engine with speed of 2100 r/min are simulated.The simulated results are in accordance with the experimental data.The effect of increased power density on charging coefficient is analyzed using a validated model.The results show that the charging coefficient is slowly improved with the increase in intake pressure,and is obviously reduced with the increase in engine speed.展开更多
An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of succe...An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of successive images,the proposed method has the number and location of the simulated charges not arbitrary.When the surface electric field of a conductor exceeds the onset value,charges are emitted from corona into the space around,and the space ions and the surface charges on each sub-conductor are simulated by using the images of the other sub-conductors.The displacements of the space ions are calculated at every time step during corona periods in both the positive and the negative half cycles.Several examples are calculated by using the proposed method,and the calculated electric field at the ground level and the corona power loss agree well with previous measurements.The results show that simulating 12 charges in each conductor during 600 time steps in one cycle takes less time while guarantees the accuracy.The corona discharge from a 220 kV transmission line enhances slightly(less than 2%) the electric field at the ground level,but this effect is little from a 500 kV line.The improved method is a good compromise between the time cost and the accuracy of calculation.展开更多
An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ)and a single Moving Plate(MP)is proposed in this article using both experimental and numerical approaches.First,an experimental set-up is prese...An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ)and a single Moving Plate(MP)is proposed in this article using both experimental and numerical approaches.First,an experimental set-up is presented.Four collision tests have been performed:two tests in Backward Moving Plate(BMP)configuration,where the plate moves in opposition to jet,and two tests in Forward Moving Plate(FMP)configuration,where the plate moves alongside the jet.Based on the virtual origin approximation,a methodology(the Virtual Origin Method,VOM)is developed to extract quantities from the X-ray images,which serve as comparative data.gSPH simulations are carried out to complete the analysis,as they well capture the disturbance dynamics observed in the experiments.Based on these complementary experimental and numerical results,a new physical description is proposed through a detailed analysis of the interaction.It is shown that the SCJ/MP interaction is driven at first order by the contact geometry.Thus,BMP and FMP configurations do not generate the same disturbances because their local flow geometries are different.In the collision point frame of reference,the BMP flows in the same direction as the jet,causing its overall deflection.On the contrary,the FMP flow opposes that of the jet leading to an alternative creation of fragments and ligaments.An in-depth study,using the VOM shows that deflection angles,fragment-ligament creation frequencies,and deflection velocities evolve as the interaction progresses through slower jet elements.展开更多
基金Project Supported by National Natural Science Foundation of China（90510015）.
文摘The choice of the UHV lines depends on surface electric field of the bundle conductors.Based on existing calculation methods,the optimized charge simulation method is used to calculate the conductors' surface electrical field of±800 kV UHVDC transmission lines in this paper.During calculation,the offset distance is set as the variance of the objective function,the position and the quantity of the simulation charges are optimized with the gold section method,and the surface electrical field is calculated when the charge is in the optimal position.The result shows that the distribution of the surface electrical field and its maximal value can be calculated accurately with this method,although less number of simulation charges is used in this proposed method and the calculation is simple.
文摘A one-dimensional pipe flow model of single-cylinder diesel engine is established to investigate the intake and exhaust flow characteristics of diesel engine in the condition of high power density(HPD).A space-lime conservation element and solution element(CE/SE)method is used to derive the discrete equations of the partial differential equation for the intake and exhaust systems.The performance parameters of diesel engine with speed of 2100 r/min are simulated.The simulated results are in accordance with the experimental data.The effect of increased power density on charging coefficient is analyzed using a validated model.The results show that the charging coefficient is slowly improved with the increase in intake pressure,and is obviously reduced with the increase in engine speed.
基金supported by National Basic Research Program of China(973 Program)(2011CB209404)
文摘An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of successive images,the proposed method has the number and location of the simulated charges not arbitrary.When the surface electric field of a conductor exceeds the onset value,charges are emitted from corona into the space around,and the space ions and the surface charges on each sub-conductor are simulated by using the images of the other sub-conductors.The displacements of the space ions are calculated at every time step during corona periods in both the positive and the negative half cycles.Several examples are calculated by using the proposed method,and the calculated electric field at the ground level and the corona power loss agree well with previous measurements.The results show that simulating 12 charges in each conductor during 600 time steps in one cycle takes less time while guarantees the accuracy.The corona discharge from a 220 kV transmission line enhances slightly(less than 2%) the electric field at the ground level,but this effect is little from a 500 kV line.The improved method is a good compromise between the time cost and the accuracy of calculation.
基金supported by the Ministère des Armées,and the Agence de l'Innovation de Défense(AID).
文摘An analysis of the interaction mechanisms between a Shaped Charge Jet(SCJ)and a single Moving Plate(MP)is proposed in this article using both experimental and numerical approaches.First,an experimental set-up is presented.Four collision tests have been performed:two tests in Backward Moving Plate(BMP)configuration,where the plate moves in opposition to jet,and two tests in Forward Moving Plate(FMP)configuration,where the plate moves alongside the jet.Based on the virtual origin approximation,a methodology(the Virtual Origin Method,VOM)is developed to extract quantities from the X-ray images,which serve as comparative data.gSPH simulations are carried out to complete the analysis,as they well capture the disturbance dynamics observed in the experiments.Based on these complementary experimental and numerical results,a new physical description is proposed through a detailed analysis of the interaction.It is shown that the SCJ/MP interaction is driven at first order by the contact geometry.Thus,BMP and FMP configurations do not generate the same disturbances because their local flow geometries are different.In the collision point frame of reference,the BMP flows in the same direction as the jet,causing its overall deflection.On the contrary,the FMP flow opposes that of the jet leading to an alternative creation of fragments and ligaments.An in-depth study,using the VOM shows that deflection angles,fragment-ligament creation frequencies,and deflection velocities evolve as the interaction progresses through slower jet elements.
