The seepage property of low-permeability rock is of significant importance for the design and safety analysis of underground cavities. By using a self-developed test system, both permeability and porosity of granite f...The seepage property of low-permeability rock is of significant importance for the design and safety analysis of underground cavities. By using a self-developed test system, both permeability and porosity of granite from an underground oil storage depot were measured. In order to study the influence of rock types on permeability, a tight sandstone was selected as a contrast. The experimental results suggested that the porosity of this granite is less than 5% and permeability is low to 10–20 m^2 within the range of effective stress. During the loading process, both exponential relationship and power law can be utilized to describe the relationship between effective stress and permeability. However, power law matches the experimental data better during the unloading condition. The stress dependent porosity of granite during loading process can be described via an exponential relationship while the match between the model and experimental data can be improved by a power law in unloading paths. The correlation of permeability and porosity can be described in a power law form. Besides, granite shows great different evolution rules in permeability and porosity from sandstone. It is inferred that this difference can be attributed to the preparing of samples and different movements of microstructures subjected to effective stress.展开更多
磁场能量收集是能源互联网中无线传感器供电的有效方法。磁场能量收集器(magnetic field energy harvester,MFEH)需要配合串联匹配电容、整流桥和DC-DC变换器以实现能量的最大功率提取与传输。然而,由MFEH与匹配电容和整流桥构成的高阶...磁场能量收集是能源互联网中无线传感器供电的有效方法。磁场能量收集器(magnetic field energy harvester,MFEH)需要配合串联匹配电容、整流桥和DC-DC变换器以实现能量的最大功率提取与传输。然而,由MFEH与匹配电容和整流桥构成的高阶非线性电路无法采用低阶简化模型对其输出特性展开分析。因匹配电容与等效电感谐振,整流桥的开路电压可能超过MFEH的交流开路电压峰值,不能简单地将MFEH的交流开路电压峰值视为整流桥的开路电压。为此,文中采用相量法和高斯-赛德尔迭代法建立高阶非线性整流桥的稳态最佳输出电压的精准模型;采用四阶-五阶龙格库塔自适应方法提取整流桥的暂态开路输出特性,实现非侵入式磁场能量收集的自供电的低功耗开路电压法最大功率跟踪方案。该研究可为磁场能量收集系统最大功率点的确定和开路电压法中参数的设定提供理论支撑。展开更多
基金Projects(11172090,51479049,11272113,11572110,51209075)supported by the National Natural Science Foundation of ChinaProject(BK2012809)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(201406710042)supported by China Scholarship Council
文摘The seepage property of low-permeability rock is of significant importance for the design and safety analysis of underground cavities. By using a self-developed test system, both permeability and porosity of granite from an underground oil storage depot were measured. In order to study the influence of rock types on permeability, a tight sandstone was selected as a contrast. The experimental results suggested that the porosity of this granite is less than 5% and permeability is low to 10–20 m^2 within the range of effective stress. During the loading process, both exponential relationship and power law can be utilized to describe the relationship between effective stress and permeability. However, power law matches the experimental data better during the unloading condition. The stress dependent porosity of granite during loading process can be described via an exponential relationship while the match between the model and experimental data can be improved by a power law in unloading paths. The correlation of permeability and porosity can be described in a power law form. Besides, granite shows great different evolution rules in permeability and porosity from sandstone. It is inferred that this difference can be attributed to the preparing of samples and different movements of microstructures subjected to effective stress.
文摘磁场能量收集是能源互联网中无线传感器供电的有效方法。磁场能量收集器(magnetic field energy harvester,MFEH)需要配合串联匹配电容、整流桥和DC-DC变换器以实现能量的最大功率提取与传输。然而,由MFEH与匹配电容和整流桥构成的高阶非线性电路无法采用低阶简化模型对其输出特性展开分析。因匹配电容与等效电感谐振,整流桥的开路电压可能超过MFEH的交流开路电压峰值,不能简单地将MFEH的交流开路电压峰值视为整流桥的开路电压。为此,文中采用相量法和高斯-赛德尔迭代法建立高阶非线性整流桥的稳态最佳输出电压的精准模型;采用四阶-五阶龙格库塔自适应方法提取整流桥的暂态开路输出特性,实现非侵入式磁场能量收集的自供电的低功耗开路电压法最大功率跟踪方案。该研究可为磁场能量收集系统最大功率点的确定和开路电压法中参数的设定提供理论支撑。
