Burden is one of the main parameters in blast design.However,field tests,either single-or multi-hole blasts,used to determine an appropriate burden,are difficult to capture crack propagation,evolution of breakage angl...Burden is one of the main parameters in blast design.However,field tests,either single-or multi-hole blasts,used to determine an appropriate burden,are difficult to capture crack propagation,evolution of breakage angle,and the mechanism governing these processes in the rock.In this study,a single-hole bench blasting model is developed using LS-DYNA software to comprehensively investigate the relationship between burden and rock breakage.The simulation results show that the breakage angle decreases with the increase in burden,and the blasted volume reaches a peak value with a burden of 4 m.Meanwhile,backbreak distance increases with increasing burden.The optimum burden in this simulation is found to be 4.0 m,as the ratio of burden to blasthole diameter is equal to 20.62 and the ratio of burden to bench height is 0.44,based on a comprehensive analysis of the blasted volume,average damage,and total damage.Under the optimum burden condition,tensile stress wave regions are simultaneously generated at the free surfaces of both the bench top and bench slope,allowing more effective utilization of the two free surfaces and resulting in a more uniform damage distribution within the burden region.展开更多
为探明柴油中混合高含氧量、来源广泛的清洁燃料庚酸甲酯对颗粒物排放的影响,基于一台四冲程高压共轨柴油机开展台架试验。庚酸甲酯分别按体积比0%、10%、20%与柴油进行掺混(燃料分别记为D100、MH10、MH20)燃烧,采用TSI公司生产的SMPS-3...为探明柴油中混合高含氧量、来源广泛的清洁燃料庚酸甲酯对颗粒物排放的影响,基于一台四冲程高压共轨柴油机开展台架试验。庚酸甲酯分别按体积比0%、10%、20%与柴油进行掺混(燃料分别记为D100、MH10、MH20)燃烧,采用TSI公司生产的SMPS-3936颗粒物粒径谱仪进行颗粒物排放监测,探究不同负荷、废气再循环(exhaust gas recirculation,EGR)率、喷射策略下燃用D100、MH10、MH203种燃料的颗粒物数浓度和体积分数变化趋势。结果表明:中高负荷时颗粒物数浓度与体积分数显著高于低负荷,颗粒物粒径向大粒径偏移,且庚酸甲酯掺混比例越高,颗粒物数浓度与体积分数越低,且燃用D100、MH10、MH203种燃料时呈现依次递减的规律;EGR率增加导致积聚态颗粒数浓度上升、粒径增大,同时导致颗粒物体积分数变大。掺混庚酸甲酯能大幅度抑制颗粒物的增长。在EGR率为0%和12%时,MH10的颗粒数浓度较D100的颗粒数浓度分别降低74.4%、75.7%,MH20的颗粒数浓度较D100分别降低78.6%、77.6%;双喷模式下增大主预喷间隔角可有效降低颗粒物数浓度,积聚态颗粒降幅显著高于核态颗粒,且掺混庚酸甲酯能进一步减少排放;单次喷射时,随着喷油时刻的推迟,颗粒物总数先降后升,D100核态颗粒变化微弱,积聚态颗粒在上止点前4°最低;MH20在上止点前6°时排放控制最优,且颗粒物体积分数随喷油推迟整体呈下降趋势。研究表明,掺混庚酸甲酯能显著降低颗粒物排放水平。展开更多
基金supported by the European Union in the frame of Horizon Europe AVANTIS project,Grant Agreement No.101137552.
文摘Burden is one of the main parameters in blast design.However,field tests,either single-or multi-hole blasts,used to determine an appropriate burden,are difficult to capture crack propagation,evolution of breakage angle,and the mechanism governing these processes in the rock.In this study,a single-hole bench blasting model is developed using LS-DYNA software to comprehensively investigate the relationship between burden and rock breakage.The simulation results show that the breakage angle decreases with the increase in burden,and the blasted volume reaches a peak value with a burden of 4 m.Meanwhile,backbreak distance increases with increasing burden.The optimum burden in this simulation is found to be 4.0 m,as the ratio of burden to blasthole diameter is equal to 20.62 and the ratio of burden to bench height is 0.44,based on a comprehensive analysis of the blasted volume,average damage,and total damage.Under the optimum burden condition,tensile stress wave regions are simultaneously generated at the free surfaces of both the bench top and bench slope,allowing more effective utilization of the two free surfaces and resulting in a more uniform damage distribution within the burden region.
文摘为探明柴油中混合高含氧量、来源广泛的清洁燃料庚酸甲酯对颗粒物排放的影响,基于一台四冲程高压共轨柴油机开展台架试验。庚酸甲酯分别按体积比0%、10%、20%与柴油进行掺混(燃料分别记为D100、MH10、MH20)燃烧,采用TSI公司生产的SMPS-3936颗粒物粒径谱仪进行颗粒物排放监测,探究不同负荷、废气再循环(exhaust gas recirculation,EGR)率、喷射策略下燃用D100、MH10、MH203种燃料的颗粒物数浓度和体积分数变化趋势。结果表明:中高负荷时颗粒物数浓度与体积分数显著高于低负荷,颗粒物粒径向大粒径偏移,且庚酸甲酯掺混比例越高,颗粒物数浓度与体积分数越低,且燃用D100、MH10、MH203种燃料时呈现依次递减的规律;EGR率增加导致积聚态颗粒数浓度上升、粒径增大,同时导致颗粒物体积分数变大。掺混庚酸甲酯能大幅度抑制颗粒物的增长。在EGR率为0%和12%时,MH10的颗粒数浓度较D100的颗粒数浓度分别降低74.4%、75.7%,MH20的颗粒数浓度较D100分别降低78.6%、77.6%;双喷模式下增大主预喷间隔角可有效降低颗粒物数浓度,积聚态颗粒降幅显著高于核态颗粒,且掺混庚酸甲酯能进一步减少排放;单次喷射时,随着喷油时刻的推迟,颗粒物总数先降后升,D100核态颗粒变化微弱,积聚态颗粒在上止点前4°最低;MH20在上止点前6°时排放控制最优,且颗粒物体积分数随喷油推迟整体呈下降趋势。研究表明,掺混庚酸甲酯能显著降低颗粒物排放水平。
