Influences of flow rate and baffle spacing on hydraulic characteristics of a novel baffle dropshaft

Due to limited flow capacity and the instability of the asymmetric structure of traditional baffle dropshafts, a novel baffle dropshaft with a symmetric structure, adopting the construction shield well directly, is proposed for large-range flow discharge in deep tunnel drainage systems. In this study, a two-phase flow field of the novel baffle dropshaft with three different baffle spacings was simulated at seven different flow rates with a three-dimensional (3D) numerical model verified with experiments, to study hydraulic characteristics of this novel baffle dropshaft. The results show that the novel baffle dropshaft has a remarkable energy dissipation effect. Baffle spacing of the novel baffle dropshaft has a greater effect on flow patterns and baffle pressure distributions than the comprehensive energy dissipation rate. Flow rate is a critical issue for the selection of baffle spacing in the design. Some guidance on baffle spacing selection and structure optimization for the application of this novel baffle dropshaft in deep tunnel drainage systems is proposed.     

Influence of the Disk Diameter and Baffle Position on the Performance of Generated Colloidal Gas Aphrons

Aphrons are surfactant‐stabilized microbubbles with thick soapy shells. Colloidal gas aphrons (CGA) with an average diameter of 50 μm have some unique properties: a high interfacial area due to their small size, a thick soapy shell and, above all, high stability compared to conventional foams. Various factors that can influence the performance of CGA dispersion, such as the type and concentration of surfactant, mixing time and processing parameters, have already been extensively studied. However, although CGA applications in various fields continue to advance, the influence of the disk diameter and baffle position of the aphron generator on the performance of CGAs has not been well studied. In this experimental work, the influences of the spinning disk diameter and baffle position inside the aphron generator have been investigated. Analyzing the drainage curve of various experimental runs revealed that the disk diameter and baffle position might have a positive impact on the stability of CGA dispersion particularly when the generation time or surfactant concentration is low. The experimental findings have been supported by other techniques such as half‐life time and a new stability index, T_0.1, the time elapsed when the drained liquid from CGA dispersion reaches ten percent of its final height.     

LIQUID FLOW OVER DISTILLATION COLUMN PLATES

The liquid flow field over a bubble-cap tray or a perforated plate in distillation columns was determined numerically using the upwind difference method. The results of the numerical calculations indicate that with flow over such a plate there exists a stagnant region along the side of the plate, which expands with the increase in the Reynolds number. Furthermore, the size of the stagnant region depends upon the inlet liquid velocity distribution and is at a minimum when the distribution is uniform. It was also found that by installing baffles, the size of the stagnant region may be significantly reduced.     

An L9 orthogonal design methodology to study the impact of operating parameters on particulate emission and related characteristics during pulse-jet filtration process

This study embodies experimental characterization of emitted particulate and filtration performance under varied situation in a pulse-jet cleaning process. Tests were conducted under simulated condition in a filtration apparatus consisting four bags. The effect of four different factors such as fabric punch density, baffle plate height, air to cloth ratio and cycle time have been investigated on the key parameters; emission, pressure drop along with PM_2.5 and average particle diameter of emitted particulate matter in a pulse-jet filtration process. Experimental investigation based on L₉-orthogonal design shows that emission is reduced with the increases in punch density and pulse cycle time; but it increases up to a certain extent with the increase in air to cloth ratio. However baffle plate height has no effect on the emission. On the other hand pressure drop across the tube sheet increases with the material consolidation, air to cloth ratio and pulse cycle time; but the above parameter first decrease with the increase in baffle plate height. PM_2.5 (based on the number distribution) is found to be mainly affected by the baffle plate height and cycle time; as it first increases and then decrease with the increase in baffle plate height but it shows reverse trend with the increase in cycle time. Average particle diameter based on number volume is found to be mainly affected by the baffle plate height and cycle time. With the increase in time of filtration, both emission and pressure drop tend to increase without affecting PM_2.5 and average particle diameter based on number volume.     

Effects of various baffle designs on acoustic characteristics in combustion chamber of liquid rocket engine

Effects of various baffle designs on acoustic characteristics in combustion chamber are numerically investigated by adopting linear acoustic analysis. A hub-blade configuration with five blades is selected as a candidate baffle and five variants of baffles with various specifications are designed depending on baffle height and hub position. As damping parameters, natural-frequency shift and damping factor are considered and the damping capacity of various baffle designs is evaluated. Increase in baffle height results in more damping capacity and the hub position affects appreciably the damping of the first radial resonant mode. Depending on baffle height, two close resonant modes could be overlapped and thereby the damping factor for one resonant mode is increased exceedingly. The present procedure based on acoustic analysis is expected to be a useful tool to predict acoustic field in combustion chamber and to design the passive control devices such as baffle and acoustic resonator.     

Velocity profiles between two baffles in a horizontal circular tube

The shell and tube heat exchanger is an essential part of a power plant for recovering heat transfer between the feed water of a boiler and the wasted heat.The baffles are also an important element inside the heat exchanger.Internal materials influence the flow pattern in the bed.The influence of baffles in the velocity profiles was observed using a three-dimensional particle image velocimetry around baffles in a horizontal circular tube.The velocity of the particles was measured before the baffle and between them in the test tube.
Results show that the flows near the front baffle flow were parallel to the vertical wall,and then concentrate on the upper opening of the front baffle.The flows circulate in the front and rear baffles.These flow profiles are related to the Reynolds number（Re） or the flow intensity.The velocity profiles at lower Re number showed a complicated mixing,concentrating on the lower opening of the rear baffle as front wall.
Swirling flow was employed in this study,which was produced using tangential velocities at the inlet.At the entrance of the front baffle,the velocity vector profiles with swirl were much different from that without swirl.However,velocities between two baffles are not much different from those without swirl.     

折流板换热器壳程流体流动与传热特性数值模拟

根据流体动力学和计算传热学理论,建立了折流板管壳式换热器计算模型,运用CFD技术对换热器壳程流体的流动与传热问题进行了三维数值模拟,得到了不同壳程进口雷诺数Re条件下换热器壳程流体的流场和温度场。对数值模拟结果进行分析,以总传热系数h．壳程总压降△p以及单位压力损失下的传热系数h／Ap作为换热器性能的衡量标准,分析了不同折流板间距和不同折流板圆缺高度时管壳式换热器壳程总传热系数h、总压降△p以及h／Ap随壳程进口雷诺数的变化规律。结果表明：随着壳程进口流速的增大,换热器壳程总传热系数和总压降增大、h／Ap减小：在壳程流体流量不变的情况下,结合单位压力损失下的传热系数h／Ap,适当减小折流板间距或减小折流板圆缺高度。可提高换热器的换热性能。     

连续式液相法制备锰酸钾的反应釜

我国采用传统的固相焙烧法生产锰酸钾,转化率低且污染环境;三相加压法实际是采用多塔间断操作保证后续工序连续生产。云南冶金集团最新发明的连续式液相法制备锰酸钾的反应釜,在反应釜内设置折流墙,突破矿浆轻成品重不能采用溢流矿浆法的瓶颈,解决卧式反应釜矿浆连续输送的难题,实现了液相法生产锰酸钾真正意义上的碱浸工序连续生产,并保证转化率达到90％以上。     

A MATHEMATICAL MODEL OF A BUBBLE COLUMN REACTOR FOR THE CUMENE OXIDATION

The liquid flow field over a bubble-cap tray or a perforated plate in distillation columns was determined numerically using the upwind difference method. The results of the numerical calculations indicate that with flow over such a plate there exists a stagnant region along the side of the plate, which expands with the increase in the Reynolds number. Furthermore, the size of the stagnant region depends upon the inlet liquid velocity distribution and is at a minimum when the distribution is uniform. It was also found that by installing baffles, the size of the stagnant region may be significantly reduced.     

空压机一级压缩系统机械故障分析

介绍了L2 5 5 5 / 4 0型空压机机体振动导致一级压缩系统发生故障的现象和原因 ,从管理、技术、维护使用诸方面提出了同类故障的预防措施。