氢气在实际应用中存在着许多负压场景,确定负压工况下的燃爆参数是对氢气进行科学评估和有效防控的首要前提。采用高精度配气及爆炸压力采集系统研究氢气在负压场景下的燃爆特性,明确氢气的爆炸上限、爆炸下限、临界爆炸压力、最大爆炸...氢气在实际应用中存在着许多负压场景,确定负压工况下的燃爆参数是对氢气进行科学评估和有效防控的首要前提。采用高精度配气及爆炸压力采集系统研究氢气在负压场景下的燃爆特性,明确氢气的爆炸上限、爆炸下限、临界爆炸压力、最大爆炸压力、最大爆炸升压比等燃爆参数;并通过Python中的Matplotlib等软件库对试验数据进行拟合,分析压力对氢气燃爆参数的影响。结果表明:在室温、空气条件下,初始压力从100 k Pa降至3.5 k Pa的过程中,爆炸范围不断缩小,特别是从初始压力低于10 k Pa开始,爆炸范围缩小速度明显增加,该现象与分子间距受压力影响的变化趋势存在强关联;当初始压力低至3.72 k Pa时,爆炸上、下限重合在12.58%体积分数的位置,该压力称为临界爆炸压力,低于该压力时体系将失去爆炸性;一般认为最大爆炸压力通常在理论当量体积分数29.6%附近取得,试验发现此规律仅适用于初始压力大≥5 k Pa的场景,当初始压力<5 k Pa时,理论当量体积分数将随着压力的减小而发生改变,逐渐偏离至体积分数10%~15%;最大爆炸升压比会随着初始压力的减小而降低,从常规的7.30降低至4.63,特别是在初始压力<5 k Pa的体系中,该比值大幅降低。展开更多
柔性软开关(soft open point, SOP)能够实现配电网的柔性互联与潮流的动态调节,从而优化配电资源的配置与调度。换流器可以在故障时输出正负序电流来提供电压支撑并提高自身的故障穿越能力,从而改善不对称接地故障的负载电压。然而采用...柔性软开关(soft open point, SOP)能够实现配电网的柔性互联与潮流的动态调节,从而优化配电资源的配置与调度。换流器可以在故障时输出正负序电流来提供电压支撑并提高自身的故障穿越能力,从而改善不对称接地故障的负载电压。然而采用开环计算的方案易受实际工况影响,采用传统负序电压闭环的支撑效果较差。因此文中在传统负序电压外环的基础上进行改进,控制负序电流的幅值以抑制负序电压,控制负序电流的相位以优化抑制效果。为提高逆变器容量利用率并限制有功波动,文中提出正负序电流限幅的综合方案,并通过PSCAD仿真软件依据实际配电网参数搭建短路工况进行仿真。结果验证该控制策略可以有效改善故障时的电压表现,提高逆变器低压穿越能力,具有更高的实际可应用性。展开更多
Through laboratory test, the relationships among change of compactibility, liquid/plastic limit, free swell, swell ratio without load, california bearing ratio (CBR) and soakage (after being soaked in water), and mix-...Through laboratory test, the relationships among change of compactibility, liquid/plastic limit, free swell, swell ratio without load, california bearing ratio (CBR) and soakage (after being soaked in water), and mix-ratio of quick lime and time were studied. The results show that optimum water content, plastic limit and CBR of high liquid limit clay improved by quick lime increase with the increase of mix-ratio of quick lime, while the maximum dry density, liquid limit, plasticity index, soakage (after being immersed in water), free swell, and swell ratio without load decrease with the increase of mix-ratio of quick lime. Plastic limit of high liquid clay improved by quick lime gradually increases with time, while the liquid limit, plasticity index, free swell and swell ratio without load gradually decrease with time. When the mix-ratio of quick lime exceeds 2%, after 14 d, swell ratio without load of the improved clay is zero, its free swell is about 30% of that of untreated soil, and its plasticity index is less than 26 for sub-grade material, satisfying the requirement by 'Specifications for Design of Highway Subgrade'.展开更多
This work aims to understand the relationship between the member angle limit and the energy ratio for 24 test samples of composite beams and CFT square steel tube columns. This work also compares the formula applicabi...This work aims to understand the relationship between the member angle limit and the energy ratio for 24 test samples of composite beams and CFT square steel tube columns. This work also compares the formula applicability for member angle limit with the previous test result to provide the basic data for the design of composite beam-CFT column. The evaluation of the member angle limit was performed with concrete compressive strength (fC =22.16 MPa, 30.49 MPa), breadth-to-thickness ratio (B/t=25.0, 33.3, 43.5), and axial capacity ratio (N/N0=0, 0.3, 0.4, 0.5) as the main variables of the test samples. For the relationship between the member angle limit (Ru) and the energy ratio (ES/EC ), the test result shows that the energy ratio becomes lower as the axial capacity ratio and the breadth-to-thickness ratio increase. The energy ratio is lower for the Type B test sample compared with that of Types A and C. For the formula suggested by SATO, the test samples are distributed evenly for comparison between test values and the member angle limit; however, other formulas indicate a deviation. Specifically, for the comparison between R u,cal and R u (Test), Maeda's formula shows severe deviation.展开更多
文摘氢气在实际应用中存在着许多负压场景,确定负压工况下的燃爆参数是对氢气进行科学评估和有效防控的首要前提。采用高精度配气及爆炸压力采集系统研究氢气在负压场景下的燃爆特性,明确氢气的爆炸上限、爆炸下限、临界爆炸压力、最大爆炸压力、最大爆炸升压比等燃爆参数;并通过Python中的Matplotlib等软件库对试验数据进行拟合,分析压力对氢气燃爆参数的影响。结果表明:在室温、空气条件下,初始压力从100 k Pa降至3.5 k Pa的过程中,爆炸范围不断缩小,特别是从初始压力低于10 k Pa开始,爆炸范围缩小速度明显增加,该现象与分子间距受压力影响的变化趋势存在强关联;当初始压力低至3.72 k Pa时,爆炸上、下限重合在12.58%体积分数的位置,该压力称为临界爆炸压力,低于该压力时体系将失去爆炸性;一般认为最大爆炸压力通常在理论当量体积分数29.6%附近取得,试验发现此规律仅适用于初始压力大≥5 k Pa的场景,当初始压力<5 k Pa时,理论当量体积分数将随着压力的减小而发生改变,逐渐偏离至体积分数10%~15%;最大爆炸升压比会随着初始压力的减小而降低,从常规的7.30降低至4.63,特别是在初始压力<5 k Pa的体系中,该比值大幅降低。
文摘柔性软开关(soft open point, SOP)能够实现配电网的柔性互联与潮流的动态调节,从而优化配电资源的配置与调度。换流器可以在故障时输出正负序电流来提供电压支撑并提高自身的故障穿越能力,从而改善不对称接地故障的负载电压。然而采用开环计算的方案易受实际工况影响,采用传统负序电压闭环的支撑效果较差。因此文中在传统负序电压外环的基础上进行改进,控制负序电流的幅值以抑制负序电压,控制负序电流的相位以优化抑制效果。为提高逆变器容量利用率并限制有功波动,文中提出正负序电流限幅的综合方案,并通过PSCAD仿真软件依据实际配电网参数搭建短路工况进行仿真。结果验证该控制策略可以有效改善故障时的电压表现,提高逆变器低压穿越能力,具有更高的实际可应用性。
文摘Through laboratory test, the relationships among change of compactibility, liquid/plastic limit, free swell, swell ratio without load, california bearing ratio (CBR) and soakage (after being soaked in water), and mix-ratio of quick lime and time were studied. The results show that optimum water content, plastic limit and CBR of high liquid limit clay improved by quick lime increase with the increase of mix-ratio of quick lime, while the maximum dry density, liquid limit, plasticity index, soakage (after being immersed in water), free swell, and swell ratio without load decrease with the increase of mix-ratio of quick lime. Plastic limit of high liquid clay improved by quick lime gradually increases with time, while the liquid limit, plasticity index, free swell and swell ratio without load gradually decrease with time. When the mix-ratio of quick lime exceeds 2%, after 14 d, swell ratio without load of the improved clay is zero, its free swell is about 30% of that of untreated soil, and its plasticity index is less than 26 for sub-grade material, satisfying the requirement by 'Specifications for Design of Highway Subgrade'.
基金supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) and funded by the Ministry of Education,Science and Technology (2011-0009227)
文摘This work aims to understand the relationship between the member angle limit and the energy ratio for 24 test samples of composite beams and CFT square steel tube columns. This work also compares the formula applicability for member angle limit with the previous test result to provide the basic data for the design of composite beam-CFT column. The evaluation of the member angle limit was performed with concrete compressive strength (fC =22.16 MPa, 30.49 MPa), breadth-to-thickness ratio (B/t=25.0, 33.3, 43.5), and axial capacity ratio (N/N0=0, 0.3, 0.4, 0.5) as the main variables of the test samples. For the relationship between the member angle limit (Ru) and the energy ratio (ES/EC ), the test result shows that the energy ratio becomes lower as the axial capacity ratio and the breadth-to-thickness ratio increase. The energy ratio is lower for the Type B test sample compared with that of Types A and C. For the formula suggested by SATO, the test samples are distributed evenly for comparison between test values and the member angle limit; however, other formulas indicate a deviation. Specifically, for the comparison between R u,cal and R u (Test), Maeda's formula shows severe deviation.
