Local entropy generation and entropy fluxes of a transient flame during head-on quenching towards solid and hydrogen-permeable porous walls

Premixed H₂-air flames are studied in a one-dimensional wall-bounded configuration. The laminar flame propagates towards and quenches at a wall that is either solid or permeable. Entropy generation by each of 19 elementary reactions is evaluated. Their total contribution remains the most important up to the quenching instance. Close to quenching, the conduction entropy generation grows considerable. Mass diffusion has a modest contribution, which decreases towards quenching. Viscous forces are negligible as a source of entropy. Effects of unburnt-mixture temperature and fuel-air ratio are investigated, and also dilution with nitrogen (inert) and water vapour. The diffusive entropy flux changed direction away from the permeating wall compared that of the solid wall. A major finding is that fuel permeation through the wall tends to decrease the entropy generation per unit of converted fuel, in particular for initially lean mixtures.     

Electro-osmotic flow of fractional second-grade fluid with fractional Cattaneo heat flux through a vertical microchannel

This study investigates the unsteady electro-osmotic flow (EOF) of a fractional second-grade fluid through a vertical microchannel with convection heat transfer. The fractional Cattaneo heat flux model will be used to modify the heat equation. The solutions for the velocity and the temperature have been derived by employing the Laplace and finite Fourier sine transforms and their numerical inverses. The results show that at the beginning of the time period, the fractional parameter postpones the movement of the fluid. Furthermore, the results show that at the high values of retardation time (non-Newtonian case), the required time for the velocity and the flow rate to reach the steady state increases. Moreover, the heat relaxation time reduces the heat transfer until a critical time, and then the effect reverses.     

Influence of Al2O3 on the electrical conductivity and structure of calcium-silicate-based melts

Electrical conductivity and structure of the CaO-SiO₂-based mold flux melts with various Al₂O₃ contents were investigated. The results show that the electrical conductivity increases with the addition of Al₂O₃ from 2 wt% to 4 wt%, but decreases with the further increase of Al₂O₃ from 4 wt% to 8 wt%. Correspondingly, the apparent activation energy reduces firstly from 55.12 ± 1.20 kJ mol to 41.09± 0.38 kJ mol, and then increases from 41.09 ± 0.38 kJ mol to 98.99 ± 1.42 kJ mol. The structure analyses suggest that complex structural units, such as Si-O-Al, Al-O⁰, Si-O-Si and Q³(Si), reduce first, but increase with the further addition of Al₂O₃. Conversely, these simple structural units, such as Al-O^-, Q⁰(Si), Q¹(Si) and Q²(Si) vary in the opposite way with the change of Al₂O₃ content. From the variations of electrical conductivity, activation energy and structural units, it can be found that when Al₂O₃ works as network breaker to simplify the melt structure, the energy barrier for transportation of conducting ions/ionic reduce, which results in the increase of electrical conductivity; while when Al₂O₃ becomes into network former, the conductivity increases, correspondingly.     

流体驱动智能管道内检测机器人关键技术及应用

使用以管道自身流体驱动并搭载漏磁检测设备的管道内部机器人进行长距离输送管道的检测是一种重要且有效的手段，其作用愈发重要。本文以省科技重大专项项目为依托，介绍了管道漏磁内检测的原理、缺陷漏磁场的算法以及关乎缺陷检出效果等在内的内检测机器人驱动力、通过适应性、速度控制和漏磁检测模块设计，并将上述项目研究成果运用到实际工业实践。结果表明：本项目开发的内检测机器人其检测适应能力更强，能进一步提高缺陷的检出灵敏度和分辨力。经开挖验证后发现缺陷信号特征与实际缺陷状态高度吻合，可在行业内推广应用。     

铜精炼反射炉熔化期重油流量数学模型与应用

依据能量平衡原理,建立了基于铜精炼反射炉熔化期重油流量的数学模型,并根据不同富氧率和不同预热温度下的铜精炼反射炉熔化期重油流量数学模型进行计算。计算结果表明,助燃空气预热时更能节约重油。采用此方案后,铜精炼反射炉的节能效果十分显著。     

硅灰石在烧结焊剂中的应用研究

通过研究硅灰石的矿物组成和物理性能以及化学组成等 ,对照烧结焊剂熔渣的化学组成进行了硅灰石在烧结焊剂中应用的试验。试验结果显示 ,硅灰石具有改善烧结焊剂的焊接工艺性能和熔敷金属力学性能的作用。     

粉状铝基钎料的钎焊性能研究

介绍了粉状铝基钎料的制备方法,探讨了以粉状铝基钎料为焊料,钎焊铝材的工艺性能,从表面张力的角度出发,讨论了粉末粒度对铝材钎焊工艺和性能的影响,结果表明:采用粒度在150～180 μm的粉状铝基钎料钎焊铝材,其焊件的剪切强度较高;采用粒度大于300,μm的粗钎料或粒度小于150 μm的细钎料钎焊铝材,其剪切强度较低,粉状...     

高气泡表面积通量浮选柱浮选硫化铜矿参数的研究

通过浮选硫化铜矿的研究，检验高气泡表面积通量浮选柱的浮选性能，优化主要结构参数和操作参数。研究表明，高气泡表面积通量浮选柱采用多段相互独立的发泡器，可以在表观充气速率较高的情况下，不增大气泡直径，而增加气泡数量，从而有效地增大气泡表面积通量，并且减少了气泡在浮升过程中兼并的可能性，避免了疏水颗粒的脱落和因气泡携带能力不足导致的回收率损失，对分选效率的提高有着十分显著的效果。高气泡表面积通量浮选柱浮选硫化铜矿，在精矿品位下降不大的情况下，回收率可提高10个百分点以上。     

浓度和流量对瓦斯加热氧化净化率的影响

传统的瓦斯爆炸防治方法虽然具有一定的效果,但却存在着很大的局限性,为了从根本上解决瓦斯爆炸的危害,对绝热氧化法进行了实验研究,在实验条件下通过绝热氧化使瓦斯气体中的CH4在爆炸浓度以下（体积浓度1％－5％）,流量在25－90L／min时氧化成无毒,无爆炸危险的CO2和H2O,净化了瓦斯气体,通过系统试验,研究了浓度和流量对瓦斯气体加热氧化净化率的影响,为消除煤矿瓦斯积聚提供了实验基础和进一步研究的新途径。     

硅藻土多孔陶瓷的耐蚀性及酸/碱处理研究

采用注浆成型的方法制备硅藻土多孔陶瓷，对不同温度烧结样品的耐酸、碱腐蚀性进行了研究。材料的耐酸蚀性优于耐碱蚀性。硅藻土多孔陶瓷经过酸或碱处理后，微观结构和宏观性能会发生相应变化，也可利用这一特性通过酸或碱处理来控制瓷的微结构和过滤性能，碱处理样品、酸处理样和原始样品的氮气通量分别为1189、802和677m^3m^-2h^-1bar^-1。