Reaction thrust characteristics of high-pressure submerged water jet of cylinder nozzles

The shapes and geometrical parameters of nozzles are key factors for fluidics. The relationship among the reaction thrust, flow rate pressure, diameter do and length L of a cylinder nozzle is analyzed theoretically. The simulation of the flow field characteristics was conducted via the FLUENT computational fluid dynamics package. Effects of the inlet conditions and the nozzle dimensions on the reaction thrust of a water jet were addressed particularly. The reaction thrust experiments were performed on a custom-designed test apparatus. The experimental results reveal that a） the nozzle diameter and the inlet conditions exert great influence on the water jet reaction thrust; and b） for L≤4d0, where the nozzle is treated as a thin plate-orifice, the reaction thrust is independent of nozzle length; for L〉4d0, where the nozzle is treated as a long orifice, the reaction thrust can reach maximum under the condition of a certain flow rate. These findings lay a theoretical foundation for the design of nozzles and have significant value, especially for the future development of high-oressure water-let orooulsion technology.     

圆锥曲线定义的应用

圆锥曲线定义的应用在近几年的高考题中屡见不鲜,主要是灵活运用圆锥曲线的第一定义和统一定义求轨迹、离心率、最值、范围等,问题的难点是由题怎样挖掘出圆锥曲线定义,关键是灵活运用圆锥曲线定义式进行转化,并能熟练掌握每一个定义的本质属性,把握其内涵与外延,才能灵活地用定义解题。     

固结试验法求取基床系数的运用

武汉市轨道交通二号线一期工程勘察,主要应用固结试验法对各类土层进行基床系数测试。针对参数取值中遇到的实际问题,通过分析固结法试验与其它试验方法和地区经验给出的基床系数之间的关系,结合原位荷载板试验的尺寸效应修正经验和原理,对固结试验法的基床系数进行尺寸效应修正,并考虑两种试验方法中土样尺寸和受力状态的不同及其相关性进行下沉量放大系数修正。在确定了基床系数的取值后,分别通过固结试验法原理和弹性理论法进一步推导出基床系数与压缩模量间的关系,进而可以通过验证两者的匹配性,使基床系数的取值更加合理,也更加科学地运用于地铁隧道设计中。     

沉淀效应对配位平衡的影响

通过引入副反应系数讨论了沉淀效应对配位平衡的影响。     

Numerical simulation of bubble chaotic motion in a cavitating water jet

~~00002RKRSr= (6) If 0tKt=, Eqs. (2),(3) and (4) change into the following equation that is applied to simulations using the MathCAD software. ddd(,,)dd1dxyygxyzzttt=== (7) where 11251(,,)()(1)gxyzABCyxaaaa=++-+, 2132131145678222124531678831(1),23(1)[(1sin],[3cos()] AyyByxxyxzCxyxyxyxzggaaaaaaaaaaaaagaaaa-------=--=++---+=+-- (8) 5g00pK6g0p…     

水能切割废钢喷嘴的设计与实验研究

喷嘴是水射流切割系统的关键元件，通过研究一级喷嘴直径、二级喷嘴直径、混合腔直径和喉管距、系统工作压力、磨料直径大小等对轴向射流速度的影响，为水切割喷嘴的优化设计奠定了基础，其结果可为高压水切割工具的设计提供参考依据。     

交错轴渐开线锥形齿轮的接触特性

Based on the theory of gearing and the gear generating mechanism, this study investigates the contact characteristics of conical involute gear pairs with crossed axes. The meshing model with a reference rack as intermedium is established and tooth contact analysis （TCA） is performed to examine the meshing and bearing contact of the conical involute gear pairs composed of a pinion and a gear. Using the contact line of reference rack tooth surface, the path of contact is confirmed, and the calculation formula of principal direction, relative curvature, path of contact and ellipse of contact are derived. Finally, numerical examples are provided to demonstrate computational results and test gears are made for tooth-bearing tests. The conclusion verifies that the theory is applicable.     

推力轴承的力学特性

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｓｉｎｃｅ 1990 ,ａｎｉｍｐｏｒｔａｎｔｄｉｓｃｏｖｅｒｙｉｎｒｏｔｏｒ ｈｙｄｒｏ ｄｙｎａｍｉｃｂｅａｒｉｎｇｓｙｓｔｅｍｄｙｎａｍｉｃｓｉｓｔｈｅｃｏｕｐｌｅｄａｃ ｔｉｏｎｏｆｔｈｒｕｓｔｂｅａｒｉｎｇｕｐｏｎｔｈｅｌａｔｅｒａｌｖｉｂｒａｔｉｏｎｉｎａｒｏｔｏｒｓｙｓｔｅｍ .Ｉｎｔｈｅ ｐｉｏｎｅｅｒｉｎｇｒｅｓｅａｒｃｈｏｆＭｉｔｔｗｏｌｌｅｎｅｔａｌ .( 1990 ) [1] ,ａｓｅｒｉｅｓｏｆｒｏｔｏｒ ｄｙｎａｍ ｉｃｃｏｅｆｆｉｃｉｅｎｔｓｏｆｔｈｒｕｓｔｍａｇｎｅ…     

超微气流粉碎技术的应用研究

超微气流粉碎技术因其耐热敏性、无污染和环境友好等特点在微纳米粉体领域有着广泛应用,并且随着超微气流粉碎设备的不断改进和研究的深入,其应用范围也在不断拓宽．概述了超微气流粉碎技术的基本原理及设备发展现状;介绍了超微气流粉碎技术在物理粉碎和化学研究尤其是化学改性和绿色合成化学中的应用研究;最后对超微气流粉碎技术的进一步应用研究做了展望．     

变推力作用下的柔性旋转飞行器动力学建模

The dynamic response of a flexible spinning vehicle with the varying thrust was investigated. The varying thrustwas modeled as a series of simple harmonic components superimposed on a constant thrust. The analytical solutions forlongitudinal motion were obtained by combining the motion equations and boundary conditions, and then, the transversebending of rocket was examined solved by considering a coupled forcing vibration with varying parameters. Numericalsolutions for a rocket with end-varying thrust were studied. It is shown that the lateral vibrations and motion attitudes ofrocket depend on the frequencies of varying thrust to great extent, and an important phenomenon, beating, maybe take place.The proposed approach is more accurate and efficient in comparison to those standard numerical techniques.     

Simulation investigation on fluid characteristics of jet pipe water hydraulic servo valve based on CFD

Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve (WHJPSV) is conducted through a commercial computational fluid dynamics (CFD) software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that: (i) Structural parameters have ...     

重氮盐的卤代反应及其反应机理

通过对亚硝酸与伯芳胺反应形成重氮盐 ,以及重氮盐被卤素取代生成卤代芳烃的反应条件和反应机理的研究 .提高了重氮盐的稳定性和产率 ,同时也使Sandmeyer反应操作更加简便 ,提高了卤代芳烃的反应速度和产率 .     

The Analysis of Performance on Spring Supported Thrust Pads Inclusive of One Dimensional Pressure Buildup

１　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ｗｉｔｈｔｈｅｉｎｃｒｅａｓｉｎｇｃａｐａｃｉｔｙｏｆｈｙｄｒｏｇｅｎｅｒａｔｏｒｓａｎｄｔｈｅｒｅｌｅｖａｎｔｌｙｉｎｃｒｅａｓｉｎｇｓｉｚｅａｎｄｌｏａｄｉｎｇｏｆｔｈｒｕｓｔｂｅａｒｉｎｇｓ,ｔｈｅｃｏｎｆｉｇｕｒａｔｉｏｎｏｆｐａｄｓｕｐｐｏｒｔｅｄｏｎａｓｉｎｇｌｅｐｉｖｏｔｈａｓｍｏｒｅａｎｄｍｏｒｅｄｉｆｆｉｃｕｌｔｙｉｎｍｅｅｔｉｎｇａｌｌｔｈｅｄｅｍａｎｄｓｉｎｒｅａｌｏｐｅｒａｔｉｏｎｃｏｎｄｉｔｉｏｎｓ．Ｔｈｅｃｏｎｆｉｇｕｒａｔｉｏｎ…     

用待定系数法配平复杂氧化还原反应方程式

根据原子平衡原理．针对较为复杂氧化还原反应方程式，在众多已有的配平方法基础上，从不定方程的角度，给出了更为简捷的所谓”待定系数“配平法，从而简化了原有结果。     

化学反应时间与半衰期及反应级数间的关系

从半衰期通式推导出t34,t78,……的通式及其共同表达式,并说明其物理意义.     

Large eddy simulation of a particle-laden turbulent plane jet

Gas-solid two-phase turbulent plane jet is applied to many natural situations and in engineering systems. To predict the particle dispersion in the gas jet is of great importance in industrial applications and in the designing of engineering systems. A large eddy simulation of the two-phase plane jet was conducted to investigate the particle dispersion patterns. The particles with Stokes numbers equal to 0.0028, 0.3, 2.5, 28 (corresponding to particle diameter 1 μm, 10μm, 30μm, 100μm, respectively) inRe=11 300 gas flow were studied. The simulation results of gas phase motion agreed well with previous experimental results. And the simulation results of the solid particles motion showed that particles with different Stokes number have different spatial dispersion; and that particles with intermediate Stokes number have the largest dispersion ratio. Project (No. G19990222) supported by the Special Funds for Major State Basic Research of China     

Large eddy simulation of a particle-laden turbulent plane jet

ＩＮＴＲＯＤＵＣＴＩＯＮＭａｎｙｅｘｐｅｒｉｍｅｎｔａｌａｎｄｎｕｍｅｒｉｃａｌｓｔｕｄｉｅｓｈａｖｅｂｅｅｎｃｏｍｐｌｅｔｅｄｔｏｉｎｖｅｓｔｉｇａｔｅｔｈｅｐａｒｔｉｃｌｅｍｏｔｉｏｎｉｎｔｕｒｂｕｌｅｎｃｅ .Ｐｒｅｖｉｏｕｓｆｌｕｉｄｄｙｎａｍｉｃｓｓｔｕｄｉｅｓｗｅｒｅｃｏｍｍｏｎｌｙｂａｓｅｄｏｎｔｉｍｅ ａｖｅｒａｇｅｄＲｅｙｎｏｌｄｓｅｑｕａｔｉｏｎｓ,ｓｕｃｈａｓｔｈｅｔｗｏ ｅｑｕａｔｉｏｎｍｏｄｅｌ.Ｊｕｓｔｌｉｋｅｔｈｅｃａｒｒｉｅｒｇａｓｐｈａｓｅ,ｔｈｅｐａｒｔｉ ｃｌｅｐｈ…     

Experimental investigation on mixing enhancement mechanism of turbulent jet flow with tabbed nozzle

Flow visualization and hot-wire measurement techniques were combined to investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Streamwise vortices generated by the tabs of different sizes and numbers were ob- served from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals （longitudinal and transverse velocity components） at different cross sections along radius direction and streamwise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-streamwise vortices, azimuthal vortices and double-row azi-muthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow.     

Effects of cryogenic cold air jet cutting on chip break in metal machining

1.IntroductionTherequirementsforenvironmentalprotectionaregettingstricterworldwide.Notonlythenaturalecologyandresourcesshouldbeconsideredinconservation,butalsotheenvironmentbeprotectedfrombeingsacrificedastheexpenseofproductivityboosts.Aconventionalmachiningprocessusedtotakeoilasthelubricantandcoolantforthesurfacesofmachinedtoolsandworkpieces,whichbroughtforthenvironmentpollution,andincreasedcostsonpost-treatingoftools,workpiecesandcuttingscrap.Asaresult,greenmachiningtechnologyfeaturingcleanp…     

浅谈氧化还原反应方程式的配平

介绍用化合价升降法配平无机、有机氧化还原反应方程式。