According to the formation of shock wave resulting from coal and gas outburst, the gas flow of coal and gas outburst was transformed from an unsteady flow to a steady one based on selected appropriate reference coordi...According to the formation of shock wave resulting from coal and gas outburst, the gas flow of coal and gas outburst was transformed from an unsteady flow to a steady one based on selected appropriate reference coordinates, and the mathematical expressions were then established by applying mass conservation, momentum conservation equation, and energy conservation equation. On this basis, analyzed gas flow mitigation of variable cross-section area and the outburst intensity, and the relations between cross-section area, velocity, and density; the relations between overpressures and outburst intensity were deduced. Furthermore, shock waves resulting from coal and gas outburst and outburst intensity were measured by experimental setup, the overpressure and outburst intensity of different gas pressures were obtained, and the similar conditions of the experiment were numerically simulated. The averaged overpressure and gas flow velocity of variable cross-section under different gas pressures were numerically derived. The results show that the averaged overpressure and outburst intensity obtained from simulation are in good agreement with the experimental results. Moreover, the gas flow velocity of variable cross-sections approximates to the theoretical analysis.展开更多
Pure proportional navigation(PPN) is suitable for endoatmospheric interceptions,for its commanded acceleration is perpendicular to interceptor velocity.However,if the target is much faster than the interceptor,the hom...Pure proportional navigation(PPN) is suitable for endoatmospheric interceptions,for its commanded acceleration is perpendicular to interceptor velocity.However,if the target is much faster than the interceptor,the homing performance of PPN will be degraded badly.True proportional navigation(TPN) does not have this problem,but its commanded acceleration is perpendicular to the line of sight(LOS),which is not suitable for endoatmospheric interceptions.The commanded acceleration of differential geometric guidance commands(DGGC) is perpendicular to the interceptor velocity,while the homing performance approximates the LOS referenced guidance laws(PPN series).Therefore,DGGC is suitable for endoatmospheric interception of high-speed targets.However,target maneuver information is essential for the construction of DGGC,and the guidance commands are complex and may be without robustness.Through the deep analysis of three-dimensional engagement,a new construction method of DGGC is proposed in this paper.The target maneuver information is not needed any more,and the robustness of DGGC is guaranteed,which makes the application of DGGC possible.展开更多
基金Supported by the National Natural Science Foundation of China （50874111） the National High Technology Research and Development Program （2009AA063201）+2 种基金 the Program for New Century Excellent Talents in University of China （NCET-10-0724） the Fundamental Research Funds for Central Universities（2010QZ05） SRF for ROCS, SEM
文摘According to the formation of shock wave resulting from coal and gas outburst, the gas flow of coal and gas outburst was transformed from an unsteady flow to a steady one based on selected appropriate reference coordinates, and the mathematical expressions were then established by applying mass conservation, momentum conservation equation, and energy conservation equation. On this basis, analyzed gas flow mitigation of variable cross-section area and the outburst intensity, and the relations between cross-section area, velocity, and density; the relations between overpressures and outburst intensity were deduced. Furthermore, shock waves resulting from coal and gas outburst and outburst intensity were measured by experimental setup, the overpressure and outburst intensity of different gas pressures were obtained, and the similar conditions of the experiment were numerically simulated. The averaged overpressure and gas flow velocity of variable cross-section under different gas pressures were numerically derived. The results show that the averaged overpressure and outburst intensity obtained from simulation are in good agreement with the experimental results. Moreover, the gas flow velocity of variable cross-sections approximates to the theoretical analysis.
文摘Pure proportional navigation(PPN) is suitable for endoatmospheric interceptions,for its commanded acceleration is perpendicular to interceptor velocity.However,if the target is much faster than the interceptor,the homing performance of PPN will be degraded badly.True proportional navigation(TPN) does not have this problem,but its commanded acceleration is perpendicular to the line of sight(LOS),which is not suitable for endoatmospheric interceptions.The commanded acceleration of differential geometric guidance commands(DGGC) is perpendicular to the interceptor velocity,while the homing performance approximates the LOS referenced guidance laws(PPN series).Therefore,DGGC is suitable for endoatmospheric interception of high-speed targets.However,target maneuver information is essential for the construction of DGGC,and the guidance commands are complex and may be without robustness.Through the deep analysis of three-dimensional engagement,a new construction method of DGGC is proposed in this paper.The target maneuver information is not needed any more,and the robustness of DGGC is guaranteed,which makes the application of DGGC possible.
