大气压对流体动力过程的影响及校正

本文应用流体力学原理 ,研究了大气压对流体动力过程的影响 ,得出不同大气压时 ,泵的允许安装高度 ,离心式风机风压 ,轴功率 ,气体转子流量计刻度的校正方法和逆流高位冷凝器气压管长度的计算方法 ,对不同海拔高度地区 ,特别是高原和盆地地区具有十分重要的现实意义。

富营养化作用和自净作用:大尺度周期和流体动力过程的反作用

90年代,氮的储量在波罗的海北部有上升的趋势,这可以用脱氮作用变化来解释所观察到的在氮储量方面的某些波动情况。虽然脱氮作用是一个缺氧过程,但沉积物可以被适度氧化,所以通过脱氮作用除去氮还是一种比较有效的方法。人们注意到,1973～1999年27年的时间里,波罗的海北部SiO_4与DIN(DIN=NO_3+NH_4)的比率大大降低了。假如可溶性的硅能够限制浮游植物赤潮的话,那么由硅藻引发的赤潮就会消失而由鞭毛藻所取代,从而导致磷酸盐储存并且沉积下来。7年以后,以前曾经流入这里的高盐水已经随着时间的推移而消失并且缺氧现象已经扩散到周围很大的一片区域。在海底深处,磷的含量已开始增长并且脱氮能力正在减弱。因此,从长远观点看,如果能使氮和磷的含量减少到最低水平,那么将有可能帮助波罗的海摆脱因富营养化而造成的影响。

流体动力净化气体效果的综合评定

在有深部矿井开采的矿区，由于矿井通风造成地面空气危急的形态，如空气中充满烟雾气体。这些是来自于烧煤锅炉、干燥装置、选煤厂和矸石堆，因此需要采用流体动力净化空气的装置。在净化装置中，压缩气体和热气体转变成液体的气举状态。这种方法实质是计算和分析参与热动力过程物体的热力函数增长。对于净化气体流体动力过程热力分析的热力函数-循环法是以著名的Гюи-Стодолы关系为基础的。一般是用i-部件表示热力函数的变化。

Simulation of mould filling process using smoothed particle hydrodynamics

The implementation of high pressure die casting （HPDC） filling process modeling based on smoothed particle hydrodynamics （SPH） was discussed. A new treatment of inlet boundary was established by discriminating fluid particles from inlet particles. The roles of artificial viscosity and moving least squares method in the present model were compared in the handling pressure oscillation. The final model was substantiated by simulating filling process in HPDC in both two and three dimensions. The simulated results from SPH and finite difference method （FDM） were compared with the experiments. The results show the former is in a better agreement with experiments. It demonstrates the efficiency and precision of this SPH model in describing flow pattern in filling process.

Smoothed particle hydrodynamics modeling and simulation of foundry filling process

A numerical model of foundry filling process was established based on the smoothed particle hydrodynamics（SPH）method.To mimic the constraints that the solid mold prescribes on the filling fluid,a composite treatment to the solid boundaries is elaborately designed.On solid boundary surfaces,boundary particles were set,which exert Lennard-Jones force on approaching fluid particles;inside the solid mold,ghost particles were arranged to complete the compact domain of near-boundary fluid particles.Water analog experiments were conducted in parallel with the model simulations.Very good agreement between experimental and simulation results demonstrates the success of model development.

2004年技术委员会暨化学工程技术信息交流会“论文集”简介

化学工程中心站于2004年11月23日至26日在西安召开“2004年技术委员会暨化学工程技术信息交流会”，会议出版的“论文集”突出工程设计应用，对工程设计人员具有很好的实际应用价值。主要内容有：综述，蒸馏、吸收、吸附、干燥过程及设备，传热、搅拌、流体动力过程及设备，非均相分离过程及设备，

Leaching process of rare earths from weathered crust elution-deposited rare earth ore

In order to strengthen the leaching procedure,the chemical processes of leaching rare earths (RE) from the weathered crust elution-deposited rare earth ore were investigated frow the viewpoints of kinetics,hydrodynamic and mass transfer.The results show that the leaching hydrodynamics follows the Darcy law.The leaching kinetics can be described by the shrinking core model;the leaching process is controlled by diffusion of porous solid layer;and the mass transfer can be described with Van Deemter equation.This provides a theoretic basis and a scientific approach with high efficiency and optimized extraction conditions in industrial practice.

Characteristics of unsteady lubrication film in metal-forming process with dynamic roll gap

Based on the theory of unsteady hydrodynamic lubrication and relevant mathematic and physical methods, a basic model was developed to analyze the unsteady lubrication film thickness, pressure stress and friction stress in the work zone in strip rolling. The distribution of pressure stress and friction stress in the work zone was obtained. A numerical simulation was made on a 1850 cold rolling mill. The influence of back tension stress and reduction on the distribution of pressure stress and friction stress between the roll gaps was qualitatively analyzed by numerical simulation. The calculated results indicate that the higher the back tension, the lower the pressure stress and the friction stress in the work zone, and the largest friction stresses are obtained at the inlet and outlet edges. The pressure and friction gradients are rather small at high back tension. The pressure-sensitive lubricant viscosity increases exponentially with the increase of pressure. The unsteady lubrication phenomenon in the roll bite is successfully demonstrated.

Kinetics of Reaction-Crystallization of Struvite in the Continuous Draft Tube Magma Type CrystallizersmInfluence of Different Internal Hydrodynamics

A laboratory-scale reaction-crystallization process of struvite synthesis from diluted water solution of Mg^2＋, NH^＋ 4 and PO3- ions was studied. The research covered the tests of two original constructions of continuous jet-pump Draft Tube Magma （DTM）-type crystallizers with internal circulation of suspension （upward/downward）. Interactions between constructional, hydrodynamic and kinetic factors were established and discussed. Nucleation and linear growth rates of struvite crystals were calculated on the basis of population density distribution. Kinetic model of idealized Mixed Suspension Mixed Product Removal （MSMPR） crystallizer considering the size-dependent growth mechanism was applied （Rojkowski hyperbolic equation）. For comparison purposes the kinetic data corre- sponded to a simpler, continuous draft tube-type crystallizer equipped with propeller agitator were analyzed. It was concluded that crystal product of larger size was withdrawn from the jet-pump DTM crystallizer of the descending flow of suspension in a mixing chamber.

A Numerical Study on Fully Developed Fluid Flow and Heat Transfer in a Spiral Finned Tube

In this paper, the standard k-ε two-equation model is adopted to numerically simulate fully developed fluid flow and heat transfer in a spiral finned tube within a cracking furnace for ethylene manufacturing. By variable transformation, the original 3-D problem is converted into a 2-D problem in spiral coordinates. The algorithm of SIMPLEC is used to study the fully developed fluid flow and heat transfer in the spiral finned tube at constant periphery temperature and constant axial heat flux. The computed results agree pretty well with the experimental data obtained from the industry. Further studies on the fluid flows and temperature profiles at different Reynolds numbers within straight and spiral finned tubes are conducted and the mechanisms involved are explored. It is found that with the spiral finned tube, pressure drop increases to a great extent whereas heat transfer tends to be decreased.

Design aspect of a novel L-shaped pulsed column for liquid–liquid extraction applications: Energy consumption and the characteristics velocity concept

This article deals with the evaluation of the consumption of energy for a steady state solvent extraction in a novel L-shaped pulsed sieve-plate column, which is highly required for design and optimization of the periodic flow processes for industrial applications. In this regard, a comprehensive evaluation on the energy consumption in case of a pulsed flow for three different chemical systems is conducted and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and the plate free area is investigated as well. Moreover, the concept of characteristic velocity models at flooding points is evaluated with respect to the variation of pressure drop along the column at different operational conditions.

Numerical investigation of optimal geometry parameters for ejectors of premixed burner

An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.

Estimation of the Hydrodynamic Regime of the Water Movement under the Influence of the Atmospheric Processes in the Bering Sea and the Sea of Okhotsk

The given investigation presents the results of estimating the water circulation in the water area of the Bering Sea and the Sea of Okhotsks, considering the influence of various types of the atmospheric processes. To solve the given problem it is used a hydrodynamic model calculating the integral functions of the flow from the surface to the bottom. By results of calculations, the maps of the integral water circulation were built for the following types of atmospheric circulation： ＂north-western＂ and ＂okhotsk-aleutian＂. In accordance with the performed calculations for the water area being studied, the hydrodynamic structures are distinguished both non-depending and depending on the type of the atmospheric circulation. The non-depending structures are characterized by the cyclonic activity in the Bering Sea and the Sea of Okhotsk in whole. Hydrodynamic structures depending on types of the atmospheric circulation have their peculiarities in the spatial-temporal distribution.

A new scheme for identifying free surface particles in improved SPH

The present paper proposes a new scheme for identifying free surface particles in an improved SPH (Smoothed Particle Hydrodynamics). With the development of the SPH, free surface identification becomes a key challenge in free surface flow simulations, especially for violent breaking water waves. According to numerical tests, existing free surface identified schemes are not reliable for weakly compressible SPH when violent waves are modeled. The new free surface identification scheme suggested here considers changes in density ratio and three auxiliary functions. Although this new scheme originates from a scheme for another meshfree method (MLPG_R method), it includes several improvements, especially developed for the improved SPH. The limited numerical tests have indicated that the scheme does not significantly increase CPU time required, but it considerably improves the identification of free surface particles.

Numerical Study of Shock Tube Flows with Homogeneous and Heterogeneous Condensations in Rarefaction Wave

Shock tubes are devices in which the state of a gas is changed suddenly from one uniform state to another by the passage of shock and expansion waves.In the theory of ideal shock tube flow,it is customarily assumed that the unsteady expansion and shock waves generated by diaphragm rupture are a perfectly centered plane wave.However, such waves are generally not centered,or may not even by plane in practice.In the present research,the time-dependent behavior of homogeneous and heterogeneous condensation of moist air in the shock tube is investigated by using a computational fluid dynamics work.Further,the numerical and experimental studies were carried out in order to investigate the effect of the diaphragm rupture process on the flow characteristics of expansion and shock waves generated near the diaphragm.