Fire behaviour of composite laminates

The thermal response of laminated glass fibre reinforced panels to severe fire conditions has been investigated by furnace fire testing and thermal modelling. Excellent fire resistance has been demonstrated for several matrix materials and the materials response has been modelled to a high degree of accuracy. The thermal resistance properties are due to a combination of low thermal conductivity, good structural integrity and significantly, the endothermic decomposition of the matrix, which slows down the heat transmission through the laminate.     

Design of a solar-driven methanol steam reforming receiver/reactor with a thermal storage medium and its performance analysis

A novel method of triple line focused on solar-powered receiver/reactor with a thermal storage medium for methanol steam reforming (MSR) hydrogen production is proposed in this paper. The photo-thermal-chemical energy conversion and coupling equations of the receiver/reactor are established, and the dynamic regularity between solar radiation and the hydrogen production characteristics is obtained by numerical simulation. The results show that a high solar radiation intensity helps to stabilize the duration of the reaction. For every 100 W m⁻² increase in the solar radiation intensity, the duration of the reaction maintained at the phase change point temperature of the phase change material (PCM) increases by approximately 11%. The daily hydrogen production performance of the system in Kunming (102°43′E and 25°02′N) during typical solar days is studied. The average annual total hydrogen production per unit of the lighting area is approximately 1300 m³. This research can guide similar issues related to solar thermochemical technology.     

Concentrated solar photocatalysis for hydrogen generation from water by titania-containing gold nanoparticles

Photocatalysis is an effective way to utilize solar energy to produce hydrogen from water. Au/TiO₂ nanoparticles (NPs) have a better performance in photocatalytic hydrogen generation because of the localized surface plasmon resonance (LSPR) effect of Au/TiO₂ NPs. In the photocatalytic hydrogen generation experiments, it was found that light intensity plays a key role in the photocatalytic reaction rate of Au/TiO₂ NPs. At a light intensity of 0–7 kW/m², the reaction rate has a super-linear law dependence on the light intensity (Rate ∝ Intensityⁿ, with n > 1). However, at a light intensity of 7–9 kW/m², the dependency becomes sub-linear (n < 1). This means that the increase rate of photocatalytic rate is smaller than that of light intensity when the light intensity exceeds 7 kW/m². In addition, the finite element method (FEM) was utilized to further elucidate the role of light intensity by calculating the absorption power and nearfield intensity mapping of a Au/TiO₂ nanoparticle. The variation trend of the calculated total absorption power agrees with the photocatalytic experimental results for different light intensities. These results shed light on the utilization of concentrated solar photocatalysis to increase the solar-to-hydrogen performance of Au/TiO₂ NPs.     

Mismatch effect of material creep strength on creep damage and failure probability of planar solid oxide fuel cell

The constraint effect with material parameters mismatch between every parts of planar solid oxide fuel cell (SOFC) plays an important role in the operation life. In this study, the mismatch effect of material creep strength coefficient on creep damage and failure probability of planar SOFC was investigated by finite element method. The results show that the maximum equivalent creep strain and failure probability of SOFC are located in the outer corner of sealant layer. With the increase of the creep strength coefficient of the sealant layer, the maximum creep damage, damage area and failure probability of the sealant layer all increase gradually. The creep strength coefficient of the sealant layer is suggested to be smaller than that of the frame material, which will improve service life of SOFC.     

Theoretical research on radial wells orientating hydraulically created fracture directional extended

Hydraulic fracturing of radial wells have become new technologies to effectively develop low permeability reservoir, thin reservoir, fractured reservoir, “dead area” after water injection etc. Influenced by ground stress and reservoir heterogeneity, hydraulically created fracture will probably not extend smoothly to connect the target area along the direction of radial wells, the reservoir stimulation effect is not ideal. Based on the pressure analysis of fracturing initiation of multiple radial holes and the theory of plasticity district, criterion of multiple radial wells orientating directional fracture propagation in the condition of ground stress is derived. In this condition, multiple radial wells will produce a continuous plasticity district in the reservoirs, while maintaining the fracture extending in plastic zone directionally without the effect of ground stress, which guarantees that fracture is interconnected between the radial wells during fracturing operation, to form the main crack along the direction of radial wells’ axis plane. In consideration of economy, maximum spacing of radial wells are optimized, in order to provide a reliable scientific basis for effectively implementation of hydraulic fracturing technology in radial wells.     

Fundamental data on the gas–liquid two-phase flow in minichannels

We report on the results of investigations into the characteristics of an air–water isothermal two-phase flow in minichannels, that is, in capillary tubes with inner diameters of 1 mm, 2.4 mm, and 4.9 mm, also in capillary rectangular channels with an aspect ratio of 1 to 9. The directions of flow were vertical upward, horizontal and vertical downward. Based on the authors 15 years of fundamental research into the gas–liquid two-phase flows in circular tubes and rectangular channels, we summarized the characteristics of the flow phenomena in a minichannel with special attention on the flow patterns, the time varying holdup and the pressure loss. The effects of the tube diameters and aspect ratios of the channels on these flow parameters and the flow patterns were investigated. Also the correlations of the holdup and the frictional pressure drop were proposed.     

Theoretical and experimental investigation of the onset of slugging in horizontal stratified air-water countercurrent flow

An experimental and theoretical study has been carried out to derive the wave height and transition criterion from wavy to slug flow in horizontal air-water countercurrent stratified flow conditions. A theoretical formula for the wave height in a stratified wavy flow regime has been developed using the concept of total energy balance over a wave crest to consider the shear stress acting on the interface of two fluids. From the limiting condition of the formula for the wave height, a criterion for transition from a stratified wavy flow to a slug flow has been derived. A series of experiments have also been conducted changing the non-dimensional water depth and the flow rates of air in a horizontal pipe and a duct. Comparisons between the measured data and the predictions of the present theory show that the agreement is within ±10%.     

Atomistic simulation study of the grain-size effect on hydrogen embrittlement of nanograined Fe

Although hydrogen-induced fracture at grain boundaries has been widely studied and several mechanisms have been proposed, few studies of nanograined materials have been conducted, especially for grain sizes below the critical size for the inverse Hall-Petch relation. In this research work, molecular dynamics (MD) simulations are performed to investigate the hydrogen segregation and hydrogen embrittlement mechanism in polycrystalline Fe models. When the same concentration of H atoms is added, the H segregation ratio in the model with the smallest grain size is the highest observed herein, showing the high hydrogen trapping ability of small-grain Fe, while the H concentration at the grain boundaries (GBs) is, on the contrary, the lowest. Uniaxial tensile test simulations demonstrate that as the grain size decreases, the models show an increased resistance to hydrogen embrittlement, and for small-grain models (d < 10 nm), the GB-related deformation modes dominate the plastic deformation, where the segregated H mainly influences the toughness by inhibiting GB-related processes.     

天然气水合物沉积物不排水剪切特性的离散元模拟

天然气水合物资源广泛分布于深海浅层沉积物中,具有储量大、能量密度高、燃烧清洁等优点,是一种极具开发前景的环保能源,深入研究天然气水合物沉积物的力学特性是实现天然气水合物资源安全开采的重要前提.利用常体积方法对天然气水合物沉积物的不排水剪切特性进行了离散元模拟,并依据物理实验结果对数值模拟结果进行了标定,最后对剪切过程中...