An experimental study of combustion characteristics of hydrogen–Air pre-mixture on the wall boundary condition

By means of the Schlieren method, the combustion characteristics of hydrogen–air pre-mixture on wall boundary conditions have been studied in a constant volume combustion cell with ignition point located in the upper part of the cell. The results indicated that the restrictive combustion process of the pre-mixture can be divided into four stages: the laminar flame stage, the cellular flame stage, the squish flame stage and the auto-ignition stage. The squish flames appear on both sides of the main flame under most of the experimental conditions. The appearance of squish flames can cause a fluctuation in pressure change rate. The lower the equivalence ratio is, the earlier squish flames appear spatially and the less the auto-ignition is prone to present itself. The lower the initial pressure is, the more difficultly the squish flames present themselves. As the initial pressure drops, the combustion tends toward directly enter into the auto-ignition stage from the laminar flame stage. The higher the initial pressure is, the earlier the auto-ignition presents itself spatially. Squish flames experience two processes of formation and spread. The restrictive effect of the wall could be a factor that impacts on squish flames.     

射水法建造薄型塑性混凝土防渗墙在向阳水库除险加固中的应用

射水法建造塑性混凝土防渗墙,是近十生年来才发展并日趋完善的建造地下连续墙的新工法.该工法具有工艺合理,工序衔接紧密,设备配套完整且自成系统,适应地层范围广,成墙垂直精度高,施工布置灵活,事故处理难度小及造墙性价比高等显著优点.本文通过该技术在向阳水库除险加目中的应用,介绍射水法建造塑性混凝土防渗墙施工工艺及施工中应注意的一些问题.     

The application and research of high-frequency ultrasonic reflection technique used in the measurement of small diameter’s tube cavity size

Based on the problems that the photoelectric detection method and the X-ray testing method cannot provide the ideal accuracy when they are applicated to detect the cavity of small workpiece with diameter Φ6 mm and the general probes cannot stretch to the internal of the workpiece, we propose a high-frequency ultrasonic reflection technique which is used to measure the cavity size of diameter tube. The method uses ultrasound to measure the thickness. It can extract information about the wall size of workpiece through signal processing, feature extraction and other methods. By using this information, we can measure the size of cavity. Compared with the test results showed by a venire caliper and screw micrometer, we can get the conclusion that the immersion focusing probe with center frequency of 10 MHz can accurately detect the cavity of the workpiece. The experiment shows that the method gives consideration to the accuracy and computational efficiency of the workpiece’s cavity parameters. It can get data supplely and effectively. There are other advantages of this method such as stable performance, easy installation, and lower power consumption and penetration ability. It is suitable for the precision measurement of the workpiece.     

THE LAMINAR FLOW TUBULAR REACTOR WITH HOMOGENEOUS AND HETEROGENEOUS REACTIONS I. Integral Equations for Diverse Reaction Rate Regimes

Design equations for non-isothermal Laminar Flow Tubular Reactors (LFTRs) with homogeneous and heterogeneous - at the reactor wall - reactions with arbitrary kinetic equations have been satisfactorily treated transforming the original P.D.E. problem into a system of integral equations. The kernels of the integral operators are related to an eigenvalue problem which does not depend on the kinetic equations; this avoids repetitive computational effort in the treating of different reaction kinetics.

To render a more efficient numerical treatment and according to the governing reaction rate regime, modified expressions of the general solution were obtained was follows: (i) a solution with kernels depending only on the diffusion and convective times was obtained for a low reaction regime; (ii) another solution with kernels including the reaction lime, besides the diffusion and convective ones, was necessary for a fast reaction regime and (iii) the local quasi-steady-state approximation was obtained as limiting case of solution (ii) for a instantaneous reaction regime.     

Fluxes and Patterns of Wall Deposits for Skim Milk in a Pilot-Scale Spray Dryer

The pattern of wall deposits in a pilot-scale spray dryer has been studied, using skim milk, by changing the flow rate to the nozzle and measuring the resultant deposition fluxes at different positions inside the dryer. The solids concentration was maintained at 30%. The deposition was measured at three locations of the conical section and in the cylindrical section of the spray dryer. Particle deposition can be either due to the inertia of the particles or turbulent diffusion, and it is not immediately obvious which of these mechanisms is dominant. Inertial deposition appeared to be present mainly at the bottom location of the conical section and was the largest amount in quantitative terms, being at least an order of magnitude larger compared with diffusion deposition, which seemed to be dominant on the side (cylindrical) walls of the spray dryer. In addition to the above observations, the deposition patterns in the conical section have been quantified. The relative deposition flux, in m^?2, which is the ratio of the deposition flux, in g m^?2 h^?1, to the solids flow rate into the dryer, in g h^?1, was between 0.04 and 0.09 m^?2 at a solids concentration of 8.8% and between 0.15 and 0.4 m^?2 at a solids concentration of 30%. The fused appearance of the microstructure in the wall deposits of skim milk powder, as seen in the Micro-CT study, suggests that re-entrainment of the wall deposits is unlikely.     

福州湾边特大桥3号墩双壁钢围堰施工

介绍福州湾边特大桥3号墩无覆盖层裸露岩石钻孔桩施工和大体积水中承台施工,为类似水上工程的施工提供一定的参考价值。     

微型磁阻元件中磁畴活动和畴壁态极性转变的研究

采用Bitter粉纹技术详细观察和研究了微型磁阻元件在磁化和反磁化过程中的磁畴结构，结果表明Barkhausen噪声来源于磁化和反磁化过程中的磁畴活动和畴壁态极性转变。磁阻元件中的曲折状畴的产生、强化和畴壁合并及畴壁态极性转变是不可逆过程，是磁阻元件输出信号噪声的主要根源。实验发现，在磁阻元件和引线的连接处存在着磁畴结构，且这一过程是不可逆的。目前尚未见过报道。这必然也是磁阻元件输出信号噪声的来源之一。     

Stability and chaotic characteristics of a wall plume

In this study artificial disturbances were introduced into a wall plume adjacent to a vertical side wall, and its stability and chaotic characteristics were experimentally examined. The main results are: (1) for high and low frequency disturbances the neutral region (a region between stability and instability) is lower and higher values of the modified Grashof number than an analytical neutral curve, respectively. (2) As the Grashof number increases, a chaotic fluctuation of temperature is observed above a critical value. This chaotic region is completely included in the region where the wall plume is unstable. (3) The flow can be classified into four regions based on patterns, a stable region, disturbance-amplification region, chaotic region and non-chaotic region.     

An investigation of air inlet types in mixing ventilation

Previous studies have shown that dispersion of contaminant concentrations strongly depends on air inlet types. However, these studies were performed computationally, not experimentally. Thus, the purpose of the current research is to obtain contaminant concentrations in a room, to perform qualitative and quantitative comparison for a wall jet (WJ) air inlet and a ceiling diffuser (CD) air inlet, and to determine more efficient inlet and outlet configuration.     

建筑节能墙体材料管理信息系统

本系统是专为北京市建筑节能墙改办开发的计算机管理信息系统。其功能复杂、结构庞大，共有六个主模块，挂接了187个基本功能模块。系统采用了目前先进的开发技术，具有WINDOWS风格，易于掌握。