Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing...Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing internal pressure status as well as provide reliable performance predictions for large-diameter DTH hammers to which conventional empirical and experimental approaches cannot be applied. In this study, CFD simulations coupled with dynamic meshing are utilized to simulate the air flow and piston movement inside the large-diameter DTH hammers. The numerical modeling scheme is verified against a theoretical model published in literature. Effects of structural parameters on hammer performance, including piston mass, piston upper-end diameter, piston groove diameter, and lengths of intake and exhaust stroke in both front and rear chambers, are analyzed in detail by virtue of sets of numerical simulations. The simulations suggest that changing the intake stroke of front chamber has a negligible influence on hammer performance while increasing the piston groove would lower all the four indicators of hammer performance, including impact energy, impact frequency, maximum stroke, and air consumption rate. Changing the other structural parameters demonstrates mixed effects on the performance indicators. Based on the numerical simulations, a large GQ-400 DTH hammer has been designed for reduced air consumption rate and tested in a field drilling practice. The air drilling test with the designed hammer provided a penetration rate 1.7 times faster than that of conventional mud drilling.展开更多
A new dinucleating 36 membered octoazadiphenol macrocyclic ligand, 3,6,9,12,20,23,26,29 octoaza 35,36 dihydroxy 16,33 dimethyl tricyclo hexatriacontane 1(34),14,16,18(36),31,32 hexene, ODTH, was synthesized by NaBH4 h...A new dinucleating 36 membered octoazadiphenol macrocyclic ligand, 3,6,9,12,20,23,26,29 octoaza 35,36 dihydroxy 16,33 dimethyl tricyclo hexatriacontane 1(34),14,16,18(36),31,32 hexene, ODTH, was synthesized by NaBH4 hydrogenation of the corresponding Schiff base obtained from the condensation between triethylenetetraamine and diformyl p cresol. It was characterized by elemental analysis, IR, UV Vis, 1H NMR and MS. The protonation constants of ODTH and the stability constants of its complexes with Cu?in 1∶1 and 1∶2 system(metal ODTH), have been determined potentiometrically at 25.0℃and μ=0.100 mol·L-1 KCl. Potentiometric equilibrium studies indicate that a variety of deprotonated and protonated mononuclear and dinuclear, as well as hydroxy bridged complexes, form in the pH range 2～12 in aqueous solution. The species distributions and the characteristics of ODTH and the complexes are also described.展开更多
针对一体化平板天线增益测量的准确度问题,对直播卫星电视接收系统的组成和一体化平板天线的特点及其性能要求进行了简要介绍,系统地总结了卫星电视接收天线增益测量的传统方法,指出了在一体化卫星电视接收天线增益测试中的局限性,提出...针对一体化平板天线增益测量的准确度问题,对直播卫星电视接收系统的组成和一体化平板天线的特点及其性能要求进行了简要介绍,系统地总结了卫星电视接收天线增益测量的传统方法,指出了在一体化卫星电视接收天线增益测试中的局限性,提出了在经典的比较法测量增益的基础上,通过在增益基准天线中增加同类型的低噪声下变频放大器,实现直播卫星电视(Direct to Home,DTH)一体化平板天线增益测试的新设想,巧妙地解决了由于此类天线输出信号变频而造成的不能同频比较增益的难题。分析了用改进的比较法测量一体化平板天线增益的误差,其均方根误差≤±0.3 d B。给出了工程测试实例,验证了该方法的可行性和有效性。展开更多
The pneumatic down-the-hole(DTH) hammer is one of the efficient equipments used in medium hard to very hard rock drilling frield,and any change in its structure design affects all performance parameters of a pneuamtic...The pneumatic down-the-hole(DTH) hammer is one of the efficient equipments used in medium hard to very hard rock drilling frield,and any change in its structure design affects all performance parameters of a pneuamtic DTH hammer directly.Yet,owing to the complexity of the dynamic interaction among the components in DTH hammer systems,until now it has been difficult to obtain reliable estimates of the design parameter affects.Thus providing an design parameter optimization and the layout of dynamics behavior of DTH hammer is of great importance.This paper documents the development and solution of a computational model for the dynamic response of a pneumatic DTH hammer.The model consists of rigid piston dynamics equation and chamber thermodynamics equations.The resulting model represented by a set of coupled nonlinear differential equations were computed in Visual C++ program.The developed solutions are used to perform a parametric study to illustrate the inffluence of the piston mass and supply pressure on the impact performance of DTH hammer system.展开更多
基金This work was supported by the Natural Science Foundation of Jilin Province(YDZj202101ZYTS143)National Key Research and Development Project of China(project No.2018YFC1505303).
文摘Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing internal pressure status as well as provide reliable performance predictions for large-diameter DTH hammers to which conventional empirical and experimental approaches cannot be applied. In this study, CFD simulations coupled with dynamic meshing are utilized to simulate the air flow and piston movement inside the large-diameter DTH hammers. The numerical modeling scheme is verified against a theoretical model published in literature. Effects of structural parameters on hammer performance, including piston mass, piston upper-end diameter, piston groove diameter, and lengths of intake and exhaust stroke in both front and rear chambers, are analyzed in detail by virtue of sets of numerical simulations. The simulations suggest that changing the intake stroke of front chamber has a negligible influence on hammer performance while increasing the piston groove would lower all the four indicators of hammer performance, including impact energy, impact frequency, maximum stroke, and air consumption rate. Changing the other structural parameters demonstrates mixed effects on the performance indicators. Based on the numerical simulations, a large GQ-400 DTH hammer has been designed for reduced air consumption rate and tested in a field drilling practice. The air drilling test with the designed hammer provided a penetration rate 1.7 times faster than that of conventional mud drilling.
文摘A new dinucleating 36 membered octoazadiphenol macrocyclic ligand, 3,6,9,12,20,23,26,29 octoaza 35,36 dihydroxy 16,33 dimethyl tricyclo hexatriacontane 1(34),14,16,18(36),31,32 hexene, ODTH, was synthesized by NaBH4 hydrogenation of the corresponding Schiff base obtained from the condensation between triethylenetetraamine and diformyl p cresol. It was characterized by elemental analysis, IR, UV Vis, 1H NMR and MS. The protonation constants of ODTH and the stability constants of its complexes with Cu?in 1∶1 and 1∶2 system(metal ODTH), have been determined potentiometrically at 25.0℃and μ=0.100 mol·L-1 KCl. Potentiometric equilibrium studies indicate that a variety of deprotonated and protonated mononuclear and dinuclear, as well as hydroxy bridged complexes, form in the pH range 2～12 in aqueous solution. The species distributions and the characteristics of ODTH and the complexes are also described.
文摘针对一体化平板天线增益测量的准确度问题,对直播卫星电视接收系统的组成和一体化平板天线的特点及其性能要求进行了简要介绍,系统地总结了卫星电视接收天线增益测量的传统方法,指出了在一体化卫星电视接收天线增益测试中的局限性,提出了在经典的比较法测量增益的基础上,通过在增益基准天线中增加同类型的低噪声下变频放大器,实现直播卫星电视(Direct to Home,DTH)一体化平板天线增益测试的新设想,巧妙地解决了由于此类天线输出信号变频而造成的不能同频比较增益的难题。分析了用改进的比较法测量一体化平板天线增益的误差,其均方根误差≤±0.3 d B。给出了工程测试实例,验证了该方法的可行性和有效性。
基金This study was supported by the NSFC No.50475056
文摘The pneumatic down-the-hole(DTH) hammer is one of the efficient equipments used in medium hard to very hard rock drilling frield,and any change in its structure design affects all performance parameters of a pneuamtic DTH hammer directly.Yet,owing to the complexity of the dynamic interaction among the components in DTH hammer systems,until now it has been difficult to obtain reliable estimates of the design parameter affects.Thus providing an design parameter optimization and the layout of dynamics behavior of DTH hammer is of great importance.This paper documents the development and solution of a computational model for the dynamic response of a pneumatic DTH hammer.The model consists of rigid piston dynamics equation and chamber thermodynamics equations.The resulting model represented by a set of coupled nonlinear differential equations were computed in Visual C++ program.The developed solutions are used to perform a parametric study to illustrate the inffluence of the piston mass and supply pressure on the impact performance of DTH hammer system.
