The reinforced two layered foundation bed considered for study consists of a layer of granular fill overlying soft non-homogeneous clay with inclusion or reinforcement （geosymhetic strips, grids or sheets） in single...The reinforced two layered foundation bed considered for study consists of a layer of granular fill overlying soft non-homogeneous clay with inclusion or reinforcement （geosymhetic strips, grids or sheets） in single layer at soil-granular fill interface A method is developed to estimate the bearing capacity of a strip footing on the surface of a reinforced foundation bed over a finite layer of clay whose undrained strength increases linearly with depth incorporating the contribution of axial resistance of the reinforcement together with those of granular fill and soft ground. Parametric studies presented quantify the improvement in bearing capacity.展开更多
One of the most significant human-made methane emission sources is the MSW （municipal solid waste）, deposited on sanitary landfills and open dumps. Within this work, an alternative MSW treatment concept is presented...One of the most significant human-made methane emission sources is the MSW （municipal solid waste）, deposited on sanitary landfills and open dumps. Within this work, an alternative MSW treatment concept is presented, which could provide a relatively clean waste/biomass-to-energy transformation. The proposed procedure comprises of a combustion and a gasification （or pyrolysis） step, which are consecutively taking place in a two-stage hybrid porous reactor system. The core of the system is two packed bed reactors, in which solid fuel （waste or biomass） is mixed with inert ceramic particles of similar size. This paper overviews the initial experimental investigation of the combustion step of a hybrid mixture, composed of wood pellets （fuel） and alumina balls （inert ceramic particles） in a 250 ram-high batch reactor. The temperature profile along the reactor, the concentration of CO and the flame front propagation velocity were measured as a function of the ceramic particle size （11 and 20 mrn）, the inert-to-fuel mass ratio （0：1, 2：1, 3：1） and the airflow rate （30, 42, 60 1/min）. Experiments indicate that an increase of the mass ratio of inert-to-fuel material and a decrease of the inert ceramic particles size lead to a decrease of the maximum temperature of the packed hybrid bed. Measured CO concentrations showed strong dependence on the inert ceramic particle size, i.e. the particle size reduction from 20 to 11 mm resulted in a significant reduction of CO-emission peaks. The maximum flame front propagation velocity of 0.2 mm/sec was detected for the airflow of 42 1/min, the particle size of 20 mm and the mass ratio of 3：1.展开更多
The heat transfer property of the powder bed greatly affects the performance of a thermochemical heat storage system. Therefore, an accurate evaluation of effective thermal conductivity （ETC） is a key for developing...The heat transfer property of the powder bed greatly affects the performance of a thermochemical heat storage system. Therefore, an accurate evaluation of effective thermal conductivity （ETC） is a key for developing thermochemical heat storage systems. This paper focuses on the ETCs of commonly used por- ous thermochemical materials, such as MgOJMg（OH）2 and CaOJCa（OH）2 powders, as well as the corre- sponding composites with embedded metal foams. Random sphere-like particles packing （RSPP） method is proposed to reconstruct the microstructures of the powder and micro-scale generation method and computed tomography are adopted for the metal foams. Energy transport equations through porous media are solved by the lattice Boltzmann method （LBM） to obtain ETC. Results obtained using RSPP-LBM method agree with experimental data better than other existing methods. For thermochemical heat stor- age, the variation of ETC during chemical reactions is numerically predicted. Metal foam-embedded ther- rnochemical materials are also studied to evaluate the enhancing effects of the metal foams. Results show that ETC of the powders is dominated by the gas phase, whereas that of the metal foam composites is dominated by the metal Phase.展开更多
文摘The reinforced two layered foundation bed considered for study consists of a layer of granular fill overlying soft non-homogeneous clay with inclusion or reinforcement （geosymhetic strips, grids or sheets） in single layer at soil-granular fill interface A method is developed to estimate the bearing capacity of a strip footing on the surface of a reinforced foundation bed over a finite layer of clay whose undrained strength increases linearly with depth incorporating the contribution of axial resistance of the reinforcement together with those of granular fill and soft ground. Parametric studies presented quantify the improvement in bearing capacity.
文摘One of the most significant human-made methane emission sources is the MSW （municipal solid waste）, deposited on sanitary landfills and open dumps. Within this work, an alternative MSW treatment concept is presented, which could provide a relatively clean waste/biomass-to-energy transformation. The proposed procedure comprises of a combustion and a gasification （or pyrolysis） step, which are consecutively taking place in a two-stage hybrid porous reactor system. The core of the system is two packed bed reactors, in which solid fuel （waste or biomass） is mixed with inert ceramic particles of similar size. This paper overviews the initial experimental investigation of the combustion step of a hybrid mixture, composed of wood pellets （fuel） and alumina balls （inert ceramic particles） in a 250 ram-high batch reactor. The temperature profile along the reactor, the concentration of CO and the flame front propagation velocity were measured as a function of the ceramic particle size （11 and 20 mrn）, the inert-to-fuel mass ratio （0：1, 2：1, 3：1） and the airflow rate （30, 42, 60 1/min）. Experiments indicate that an increase of the mass ratio of inert-to-fuel material and a decrease of the inert ceramic particles size lead to a decrease of the maximum temperature of the packed hybrid bed. Measured CO concentrations showed strong dependence on the inert ceramic particle size, i.e. the particle size reduction from 20 to 11 mm resulted in a significant reduction of CO-emission peaks. The maximum flame front propagation velocity of 0.2 mm/sec was detected for the airflow of 42 1/min, the particle size of 20 mm and the mass ratio of 3：1.
基金supported by the National Key Basic Research Program of China (2013CB228303)
文摘The heat transfer property of the powder bed greatly affects the performance of a thermochemical heat storage system. Therefore, an accurate evaluation of effective thermal conductivity （ETC） is a key for developing thermochemical heat storage systems. This paper focuses on the ETCs of commonly used por- ous thermochemical materials, such as MgOJMg（OH）2 and CaOJCa（OH）2 powders, as well as the corre- sponding composites with embedded metal foams. Random sphere-like particles packing （RSPP） method is proposed to reconstruct the microstructures of the powder and micro-scale generation method and computed tomography are adopted for the metal foams. Energy transport equations through porous media are solved by the lattice Boltzmann method （LBM） to obtain ETC. Results obtained using RSPP-LBM method agree with experimental data better than other existing methods. For thermochemical heat stor- age, the variation of ETC during chemical reactions is numerically predicted. Metal foam-embedded ther- rnochemical materials are also studied to evaluate the enhancing effects of the metal foams. Results show that ETC of the powders is dominated by the gas phase, whereas that of the metal foam composites is dominated by the metal Phase.
