离心泵轴向力计算方法研究与试验验证

在设计工况下平衡腔液体压力数学模型计算中,引入了泵腔液体压力损失修正系数,解决了有液体泄漏时泵腔进口与后密封环进口液体压力差的计算问题.以降速后的IS80-50-315型离心泵为例,采用改变叶轮平衡孔直径和后密封环间隙来改变比面积的方法,研究了设计工况下平衡腔液体压力数学模型和轴向力的特性.研究结果表明,设计工况下平衡腔液体压力数学模型特性曲线,可以解决轴向力计算中平衡腔区域叶轮后盖板液体压力差计算这一关键问题;平衡腔液体压力是由平衡孔和后密封环构成的2道"闸阀"协联调节的结果,从控制轴向力角度,可通过轴向力特性曲线寻求叶轮平衡孔直径与后密封环间隙的最佳比值.用2个测试实例验证了应用设计工况下平衡腔液体压力数学模型计算轴向力的可靠性.

那罗寨煤矿13号煤层瓦斯赋存规律研究

为准确掌握那罗寨煤矿13号煤层的瓦斯赋存规律,并建立合理的瓦斯压力数学模型,从矿区古沉积环境、沉积史及构造控制特征等瓦斯地质特征入手,分析了那罗寨煤矿的瓦斯赋存特征,并划分了瓦斯地质单元;在同时考虑了多种主要影响因素的条件下,通过合理的因子分析方法,得出了影响瓦斯赋存的关键因素,并最终建立了13号煤层瓦斯压力的多元数学模型。对比研究结果表明,多元模型预测的平均相对误差为12.74%,而单因素模型预测的平均误差为23.48%,多元模型预测效果明显好于单因素。

煤层气井井间干扰研究及应用

井间干扰是实现煤层气稳产高产的有效技术措施。目前,煤层气井间干扰的理论研究较多,准确量化的现场认识较少。根据煤层气井排采的特点,提出了一种方便、可靠、高效的用于判断井间干扰现象及定量计算井间干扰程度的新方法,该方法利用现场观察到的煤层气井启抽水位与原始水位存在的明显差异,定量化煤层气排采降压过程中出现的井间干扰现象。通过在保德区块的实际应用,对比了所提出方法与煤层气理论判断方法的优缺点,并验证了所提出方法的可靠性,得出了该区块井间干扰特征的定量化认识,同时提出了井间干扰规律在合理部署井位、提高产气速度、缩短见气时间及优化排采制度等方面的应用建议。

MATHEMATICAL MODEL OF ~4He QUANTUM INTERFEROMETER GYROSCOPE

The mathematical model of 4He quantum interferometer gyroscope is presented. The model includes the driven equation, the current equation and the position equation. Therefore, it can sufficiently describe the gyro- scope system. The driven equation shows the thermally driven gyroscope can work for a long time but the pres- sure driven one cannot. From the current equation, the superfluid currents passing through the weak link contain the AC currents which show the rotation flux, and other currents caused by drive. As shown in the position equa- tion, the displacement of diaphragm is the only detectable parameter in the gyroscope system. The model is tested by the simulations based on experimental parameters, and can be used to research performance of the gyroscope and analyse the gyroscope error.

Mechanics Model to Determine Swelling Potential of Expansive Soils

The factors influencing on soil expansion are reviewed in the paper. A mechanics model to determine swelling potential of expansive soils is presented. The mechanics model is based on the softening of expansive soil following absorption of water. The constitutive relationships of the mechanics model include the relationship among swelling under free load, swelling under load, and vertical pressure, and the relationship of swelling under free loading and swelling pressure. A concept of additional compression modulus is introduced and the method determining the modulus is proposed. Finally, the predicted results of swelling potential using the mechanics model compare well with the measured data.

Progress in Pressure Swing Adsorption Models During the Recent 30 Years

The pressure swing adsorption (PSA) models discussed here are divided into three categories: partialdifferential equation model, electrical analogue model and neural network model. The partial differential equationmodel, including equilibrium and kinetic models, has provided an elementary viewpoint for PSA processes. Usingthe simplest equilibrium models, some influential factors, such as pressurization with product, incomplete purge,beds with dead volume and heat effects, are discussed respectively. With several approximate assumptions i.e.,concentration profile in adsorbent, 'frozen' column, symmetry and heat effects of bed wall, the more complexkinetic models can be simplified to a certain degree at the expense of a limited application. It has also been foundthat the electrical analogue model has great flexibility to handle more realistic PSA processes without any additionalhypothesis.

Modeling of Arc Force in Plasma Arc Welding

A three-dimensional mathematical model for the transferred-type argon arc was developed to describe arc force on the anode surface. The software ANSYS was employed to solve the model. The model includes a part of torch and tungsten electrode to achieve more reasonable resuits. The arc temperature and flow fields were derived. And the influences of welding parameters on arc force were also studied. The simulated results show that arc pressure at the anode are dependent on the welding current, plasma gas flow rate and electrode neck-in, while not sensitive to arc length.

Experimental study on the pressure control of soil chamber in shield tunneling

A mathematical model of the soil pressure system in shield tunneling was proposed to optimize soil pressure control in the soil chamber, based on the constitutive relationship between strain and stress. The desired pressure is determined by using the finite element method. A linear quadratic constant state tracking problem was considered over an infinite time interval. The optimal control law was derived by differentiating the Hamilton function with respect to system input. In order to verify the effectiveness of the proposed mathematical model and optimal control law, an experimental study on the pressure control of the soil chamber in shield tunneling was conducted in a laboratory. The experiment results show that soil pressure in the soil chamber in shield tunneling can be accurately controlled.

Simulation of Continuous Esterification Process of Polyester Polyols

Based on the kinetic and thermodynamic equations, a comprehensive mathematical model for the con- tinuous esterification process of polyester polyols was developed, which was carried out in an innovational bub- bling reactive distillation tower （BRDT） at atmospheric pressure. In this new type of reactor, direct esterification between ethylene glycol and adipic acid was accomplished efficiently and rapidly. A bench BRDT with the height of 2 m was applied for the esteriflcation process of l^oly （ethylene adlpate） （P＇EA）. In the continuous operation, Hn- ear oligomers were discharged from the bottom of the column, while water passed a few column trays and a pack- ing section as a condensation byproduct. The influence of major operating conditions on reactor performance was also simulated. Simulation results were in good agreement with experimental data, providing a strategy for devel- oping and optimizing this process.

Numerical simulation on influence of jet angle on jet's characteristics in flowing ambient fluid

Based on the stress-algebraic model, the turbulent buoyant jet with variable density was studied by the relation between density and concentration. A simple expression for buoyancy coefficient was proposed. The governing equations of turbulent buoyant jet with variable density were closed by introducing the expression of β and the relation between density and concentration. Numerical results for the jet axis with density difference agree well with experimental ones. By finite volume method, the 2 - D vertical jet＇s flow field with different jet angles was studied. The analysis of the relation among the vortex center, the position of separation point and jet angles shows that the circumfluenee field is the largest when the jet angle is 90°. The area turbulent kinetic energy ka is proposed and the relationship between mixing intensity and jet angles is analyzed based on it. Results show that the jet angle of is the optimum condition for jet water mixing with environment water;and the reduced rate of difference between the centerline density of jet and the density of ambient water is the largest at the jet angle of 90°.

Study on cogging force of permanent magnet linear synchronous motor

Presented the methods to obtain the cogging force of permanent magnet linear synchronous motors(PMLSMs), analyzed the characteristics of the cogging force, and provided a basis for reducing the effect of the cogging force. 2-dimensional finite element method(2D FEM) was used to solve the whole motor when its mover was at dif- ferent position, so that the relation was derived between the cogging force and the mover position. The analysis results show that the cogging force between the two ends of the primary iron-core and the secondary permanent magnets (PMs) is sinusoidal function of the mover position under certain conditions only. Two proposed methods, namely direct and indirect methods, are applied to calculate the cogging force between the primary iron-core teeth and the secondary PMs. The agreement of the two methods is validated.

Parametric design of an electrorheological shock absorber with the mixed-mode

A mathematical model based on an electrorheological (ER) shock absorber with the mixed-mode is presented. Its application to the parametric design of an electrorheological fluid shock absorber with the simulation calculation performed by program MATLAB demonstrates that the model can predict the behavior of ER shock absorbers satisfactorily, shorten the design period of an electrorheological shock absorber, and reduce the cost in the prototype manufacturing. The strength analysis based on a three-dimensional finite element model for the electrorheological shock absorber confirm that the structure design of the ER shock absorber is reasonable, and the stress distribution is uniform.

Application of artificial neural networks and multivariate statistics to estimate UCS using textural characteristics

Before any rock engineering project,mechanical parameters of rocks such as uniaxial compressive strength and young modulus of intact rock get measured using laboratory or in-situ tests,but in some situations preparing the required specimens is impossible.By this time,several models have been established to evaluate UCS and E from rock substantial properties.Artificial neural networks are powerful tools which are employed to establish predictive models and results have shown the priority of this technique compared to classic statistical techniques.In this paper,ANN and multivariate statistical models considering rock textural characteristics have been established to estimate UCS of rock and to validate the responses of the established models,they were compared with laboratory results.For this purpose a data set for 44 samples of sandstone was prepared and for each sample some textural characteristics such as void,mineral content and grain size as well as UCS were determined.To select the best predictors as inputs of the UCS models,this data set was subjected to statistical analyses comprising basic descriptive statistics,bivariate correlation,curve fitting and principal component analyses.Results of such analyses have shown that void,ferroan calcitic cement,argillaceous cement and mica percentage have the most effect on USC.Two predictive models for UCS were developed using these variables by ANN and linear multivariate regression.Results have shown that by using simple textural characteristics such as mineral content,cement type and void,strength of studied sandstone can be estimated with acceptable accuracy.ANN and multivariate statistical UCS models,revealed responses with 0.87 and 0.76 regressions,respectively which proves higher potential of ANN model for predicting UCS compared to classic statistical models.

Dynamic Model for Evaluation of Risk Factors During Work in Hot Environment

Mathematical model is developed for prediction of physiological changes in man during work in hot environment taking into consideration intensity of work, clothing and environment. To evaluate human functional state the heat stress index was calculated. Modeling researches made the conclusion that the main risk factor during work in hot environment is water losses that happens through thermoregulatory sweat evaporation. Modeling showed that in humid environment man wearing protective clothing has short time to work as water losses became more than 2% of human weight that means body dehydration. Preliminary model prediction can be used as preventive method to avoid hazard of human health.

Theoretical Model of the Tropospheric Pressure Variation on the Height

In the study and the research of the troposphere, the knowledge about its pressure variation on the height is necessary and important. Of course, exist the sounding to make this work, but not always it is possible to access to sounding data when is necessary, so then, it is important to has others alternatives methods in order to replace it. The troposphere is basically a fluid, susceptible to be studied under the fluid mechanics and thermodynamics of the ideals gases without loss generalities. So, it is possible to study of the atmospheric air like as a continuous perfect gas. These facts are important questions to study the troposphere under the laws and beginning Physics, using its respective equations, in order to get a theoretical model to simulate the behavior of its thermodynamics variables and parameters. Working on this line, it was developed a model in order to simulate the tropospheric pressure variation on the height from its measure on surface data.

Numerical Simulation on Effects of Pressure Distribution of Wind Turbine Blade with a Tip Vane

It is important to study the pressure distribution on the blade and in the adjacent area while searching the power augmentation theory with adding a tip vane to the wind turbine. This paper shows the CFD simulation relationship of the pressure distribution on the rotor blade and in the adjacent area, after calculating the pressure of the different chordwise and spanwise point on the blade with the tip vane-V（8.8×8） and without the tip vane under tip speed ratio λ 4.5. Combining the isobaric section figure in certain location, it can be seen that the tip vane improve the pressure difference between pressure and suction surface. The most influenced zone is found and these can further display the power augmentation theory of the wind turbine using the tip vane. The simulation calculation was based on N-S equations. 3-D, steady, implicit solver was chosen. Turbulence model was k-ω SST. Discretization scheme is SECOND ORDER UPWIND. Pressure-velocity coupling was a typical SIMPLE scheme. In the whole grid system, two-divided grid formation was adopted, that is, inner region and outer region. Inner region including rectangular solid blade and neighboring, outer region is semi-cylinder. There were together 720,000 nodes with tetra-prism unstructured mesh.

A new route for length measurement by phase-shifting interferometry

By the mathematic models of flexible hinge,the accurate relationship between the phase-shifting and pressure acting on the hinge is deduced and verified by experimental results.Through the optimization of the geometric parameter of flexible hinge,a phase-shifting generator is developed to determine the length of an object precisely by interferometry.The experiments show that the triple phase-shifting produced using this generator is up to 1 m.With this generator,an example for the application in length measurement is introduced.The result shows the length uncertainty is 0.5 nm when the temperature uncertainty is limited in 2 mK.This paper provides a novel technique to measure the dimension of an object,especially to the diameter of a silicon sphere for Avogadro constant project.

Investigation of the spike-stall warning method using the blade passing signal

The vaned-diffuser usually brings compressor instability problems under the small flow rate, for instance the spike-type rotating stall phenomenon which restricts the operation range and may cause the trouble of blade fatigue. Since it is difficult to mathematically predict the spike-type stall for its randomness, finding out a practical method to warning this stall precursor appears to be meaningful. The paper explains the relationship between the spike-type precursor and the blade passing irregularity coefficient to analyze whether this coefficient is appropriate for the spike-stall warning inside a centrifugal compressor with the vaned-diffuser. The advanced wireless measurements were conducted on a 1.5 stages test centrifugal compressor to capture the unsteady behavior progressing from the design to stall inception within the region between the impeller trailing edge(TE) and diffuser leading edge(LE). The circumferential distribution of the blade passing irregularity has been quantitatively revealed.The steep increase of the blade passing irregularity at some "special locations", which is responsible for the onset of the spiketype precursor, is highlighted. Also, to further understand the spike precursor inside the diffuser passage corresponding to the circumferential "special location" with maximum irregularity, the high-response transient measurement within this passage is presented. With the help of full-annulus computational fluid dynamics(CFD) simulation and the mathematical model, it is proved that the blade passing irregularity precisely reflects the flow characteristics during the spike precursor, which presents the guidance for this stall warning method.

Mathematical Modelling of the Transient Response of Pipeline

Steam pipelines applied in power units operate at high pressures and temperatures.In addition,to stress from the pipeline pressure also arise high thermal stresses in transient states such as start-up,shutdown or a load change of the power unit.Time-varying stresses are often the cause of the occurrence of fatigue cracks since the plastic deformations appear at the stress concentration regions.To determine the transient temperature of the steam along the steam flow path and axisymmetric temperature distribution in the pipeline wall,a numerical model of pipeline heating was proposed.To determine the transient temperature of the steam and pipeline wall the finite volume method(FVM) was used Writing the energy conservation equations for control areas around all the nodes gives a system of ordinary differential equations with respect to time.The system of ordinary differential equations of the first order was solved by the Runge-Kutta method of the fourth order to give the time-temperature changes at the nodes lying in the area of the wall and steam.The steam pressure distribution along pipeline was determined from the solution of the momentum conservation equation.Based on the calculated temperature distribution,thermal stresses were determined.The friction factor was calculated using the correlations of Churchill and Haaland,which were proposed for pipes with a rough inner surface.To assess the accuracy of the proposed model,numerical calculations were also performed for the thin-walled pipe,and the results were compared to the exact analytical solution.Comparison of the results shows that the accuracy of the proposed model of pipeline heating is very satisfactory.The paper presents examples of the determination of the transient temperature of the steam and the wall.

Heat transfer analysis of viscoelastic fluid flow due to metachronal wave of cilia

This study describes ciliary motion on the transport of fluids in human body with heat transfer. The mathematical model of the flow of a Jeffrey fluid in a tube of finite length is considered due to metachronal wave of cilia motion. Flow equations have been modeled and simplified using similarity variables. Exact solutions of the formulated problem have been obtained for velocity, temperature and pressure gradient and graphs for velocity, pressure rise pressure gradient and temperature profile have been plotted and studied for different values of specific physical parameters. Trapping phenomena and isotherms are presented at the end of the paper.