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.     

槽式太阳能聚光器能流密度测试系统研制技术

设计一种用于槽式太阳聚光器焦线能流密度测试系统,系统主要由余弦反射体、CCD光学测量系统、导轨及调整系统等组成.首先在实验室内采用辐射标定装置对余弦反射体和CCD光学测量系统进行精密标定,得到CCD光学测量系统灰度与能流密度定量关系;然后再用该系统对槽式太阳聚光器焦线能流密度进行测试.介绍该测试系统的标定方法和各部分设...     

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.     

Characterizing bubble behavior in a pseudo-2D fluidized bed of wet particles

By applying digital image analysis on the bubble characteristics in a two dimensional wet-particle fluidized-bed, we report two-stage evolution of bubble characteristics with increasing liquid content. In the first stage, bubble number and uniformity of bubble fraction increase, while bubble average diameter and aspect ratio decrease. In the second stage, these characteristics shift toward an opposite direction. This two-stage evolution of bubble characteristics are analogous to that of reducing particle size in dry-particle fluidization, and the fluidizing properties of particles shifts from Geldart Group B to Group A and then to Group C. Furthermore, liquid addition causes a continuous decrease of bubble fraction and bubble flow rate. This is different from dry-particle fluidization, in which reducing particle size causes an increase trend. An explanation for this difference is that liquid addition increases the equivalent size of agglomerates in wet-particle fluidization, which is opposite to the effect of reducing particle size.     

Impacts of Cattaneo–Christov heat flux on the radiative MHD nanofluid flow past a stretched cylinder under multiple slip conditions

This investigation explores the features of velocity distribution, mass and heat transmissions of nanoliquid stream over a permeable cylinder accompanied by Cattaneo–Christov heat model and thermal radiation with nonlinear sort. Multiple slip conditions have been also encountered here. A magnetic force is oriented along vertically upward. The existence of thermophoresis together with Brownian motion has been assumed here. The foremost equations and associated boundary conditions have been normalized through the similarity technique. Then we solve the system numerically along with the fourth-order Runge–Kutta shooting scheme by using the software MAPLE-17 and round it with our preassigned accuracy level. The obtained outcomes are epitomized by tables and graphs. All of the impacts have been compared in suction and injection correspondingly and explained with proper reasoning. In charts, the physical consignments (such as Sherwood number, Nusselt number and skin friction) reveal the transference of mass and temperature and amount of friction by nanoparticles in the nanocomposition. For suction, the nanofluidic temperature gradually diminished due to the advanced thermal relaxation, whereas the contrary fact is exhibited in injection. The relaxation parameter of concentration provides a positive influence on mass transmission. The rates of amplification of this transportation are 1.99% and 3.87%, measured in consideration of injection and suction, respectively. Thermal radiation influenced the fluid's temperature in a positive direction. It increases Nusselt number with 41.75% in suction, and 45.21% is recorded for injection.     

Effect of TiO2 on viscosity and structure for CaO-SiO2-Al2O3-based mold flux

The viscosity of CaO-SiO₂-Al₂O₃-MgO-Na₂O-CaF₂-(TiO₂) was measured by the rotating column method, and the viscosity, break temperature and viscous flow activation energy of the slag were analyzed based on the results. The effect of TiO₂ content on the structure of the slag was studied by Raman spectroscopy. The results show that with the increase of TiO₂ content in CaO-SiO₂-Al₂O₃-based mold flux, the viscosity of mold flux increases, the break temperature increases from 1418 K to 1535 K, and the viscous flow activation energy changes little. At high temperature, TiO₂ can depolymerize the [Si-O] and enter into the network structure as [Ti-O], which increases the frictional resistance to the viscous flow of the mold flux. At the same time, the crystallization temperature and viscosity of the slag is increased.     

多弧离子镀TiAlN薄膜的制备及其抗氧化性能

目前,关于氮氩比对TiAlN薄膜高温抗氧化性能影响的研究较少。采用多弧离子镀技术在M2高速钢上沉积TiAlN薄膜,利用SEM、XRD等方法研究氮氩流量比对薄膜组织结构、表面形貌和抗氧化性的影响。结果表明:TiAlN薄膜呈δ-TiN面心立方晶体结构;随着氮氩流量比的提高,薄膜表面熔滴数量显著下降,膜层表面更加平整光滑,相结构的择优取向发生改变,硬度先增大后趋于稳定,表面氧化物含量逐渐下降;当氮氩流量比为9∶1时,所得TiAlN薄膜在800℃氧化温度下,其表面会生成一层致密的Al_2O_3保护膜,有效阻止了薄膜被进一步氧化,具有良好的抗氧化性能。     

BP神经网络模糊PID控制在加热炉煤气流量控制中的应用

钢厂中加热炉是一个复杂的受控对象,存在着非线性、时变性、纯滞后因素和不确定随机干扰等因素.从对其燃烧状况的分析来看,加热炉温度的调节主要是靠对煤气流量的控制来完成的,因而确立一种合理的煤气流量控制方案是实现加热炉燃烧智能化控制的关键.本文提出将模糊控制、PID控制和神经网络三种技术相结合,应用于煤气流量进行控制.仿真研究表明这种BP神经网络模糊PID控制在克服对象的大惯性、抗干扰性、非线性和纯滞后上,大大改善控制品质.     

流量累计和虚拟通道功能在无纸记录仪的实现

介绍JLY－2000型无纸记录仪中流量累计和虚拟通道功能的实现方法。