针对钻遇破碎、漏失等复杂地层时反循环形成效果差,孔口返风严重这一实际问题,根据柯恩达附壁效应的基本原理,设计出一种煤矿应急钻孔救援用新型强力抽吸反循环钻头。借助流体分析软件FLUENT对钻头内部流场进行数值模拟。结果表明,相同...针对钻遇破碎、漏失等复杂地层时反循环形成效果差,孔口返风严重这一实际问题,根据柯恩达附壁效应的基本原理,设计出一种煤矿应急钻孔救援用新型强力抽吸反循环钻头。借助流体分析软件FLUENT对钻头内部流场进行数值模拟。结果表明,相同条件下强力抽吸式钻头内部最大负压值达到20 k Pa,而普通内喷孔式反循环钻头的负压值为15 k Pa;强力抽吸式钻头环空边界抽吸气体的质量流量为0.039 kg/s,而普通内喷孔式反循环钻头环空边界抽吸气体的质量流量为0.026 kg/s,抽吸量提高到原来的约1.5倍,内部流场模拟显示其性能优于普通反循环钻头。展开更多
The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are...The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.展开更多
The effect of pressurized air inlets in the reservoir upstream of the annular slit on characteristics of the axial and tangential velocity components is investigated numerically, and the mechanism of occurrence of spi...The effect of pressurized air inlets in the reservoir upstream of the annular slit on characteristics of the axial and tangential velocity components is investigated numerically, and the mechanism of occurrence of spiral nozzle flow is clarified. In simulations, Unified Platform for Aerospace Computational Simulation (UPACS) is used. The governing equations under consideration are the unsteady compressible Navier - Stokes. A second-order finite volume scheme with MUSCL (Roe scheme) is used to discretize the spatial derivatives, and a second order-central difference scheme for the viscous terms, and a MFGS (Matrix Free Gauss Seidel) is employed for time integration. Spalart-Allmaras model was used as a turbulence model. The results obtained are compared with velocity distributions in the experiment measured by the two-component fiber optic laser Doppler velocimeter system. The existence of discrete pressurized air inlets that leads to the occurrence of asymmetrical characteristics is a very important factor for the formation of spiral flow.展开更多
文摘针对钻遇破碎、漏失等复杂地层时反循环形成效果差,孔口返风严重这一实际问题,根据柯恩达附壁效应的基本原理,设计出一种煤矿应急钻孔救援用新型强力抽吸反循环钻头。借助流体分析软件FLUENT对钻头内部流场进行数值模拟。结果表明,相同条件下强力抽吸式钻头内部最大负压值达到20 k Pa,而普通内喷孔式反循环钻头的负压值为15 k Pa;强力抽吸式钻头环空边界抽吸气体的质量流量为0.039 kg/s,而普通内喷孔式反循环钻头环空边界抽吸气体的质量流量为0.026 kg/s,抽吸量提高到原来的约1.5倍,内部流场模拟显示其性能优于普通反循环钻头。
基金Project supported by the National Basic Research Program (973) of China (No.2006CB705400)the National Natural Science Foundation of China (No.50575200)
文摘The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.
文摘The effect of pressurized air inlets in the reservoir upstream of the annular slit on characteristics of the axial and tangential velocity components is investigated numerically, and the mechanism of occurrence of spiral nozzle flow is clarified. In simulations, Unified Platform for Aerospace Computational Simulation (UPACS) is used. The governing equations under consideration are the unsteady compressible Navier - Stokes. A second-order finite volume scheme with MUSCL (Roe scheme) is used to discretize the spatial derivatives, and a second order-central difference scheme for the viscous terms, and a MFGS (Matrix Free Gauss Seidel) is employed for time integration. Spalart-Allmaras model was used as a turbulence model. The results obtained are compared with velocity distributions in the experiment measured by the two-component fiber optic laser Doppler velocimeter system. The existence of discrete pressurized air inlets that leads to the occurrence of asymmetrical characteristics is a very important factor for the formation of spiral flow.
