涡街流量测量中一种振动信号识别方法的研究

基于流体振动原理的涡街流量计对振动干扰尤为敏感,为解决振动问题对涡街流量计发展的影响,通过实验证明了管道振动方向的多样性,同时基于涡街载荷方向的单一性提出了通过方向区分振动信号和涡街信号的新思路。为验证这一思路,将MEMS加速度计安装在探头末端,在振动条件下采集实验信号。实验结果证实:加速度计在3个方向上检测到了不同的信号,通过不同方向的加速度信号能够对涡街信号和振动信号进行有效区分。     

基于MSP430的数字涡街流量计的实验研究

针对涡街流量计低流速的信号噪声问题,介绍基于MSP430数字涡街流量计的实验系统,探讨、研究噪声信号的处理.采用精度较高的称重法在流量实验标准装置上对数字涡街流量计进行标定.实验结果表明,运用MSP430功能强大的微处理器及高速运算能力,有效地扩大涡街的量程比,实现对涡街流量计的信号分析、处理,提高对噪声的抗干扰能力.     

随机温度信号互相关法测量吸热型碳氢燃料密度

为实现超临界压力下吸热型碳氢燃料密度的准确测量,以相关测量技术为基础,设计搭建了一套密度在线测量系统。该系统在间距148 mm的管道上下游安装两只具有相同热电特性的K型热电偶作为互相关法的传感器,通过对热电偶检测到的随机温度信号进行相关计算,得出该信号经过上下游热电偶的延迟时间,计算得到流体截面的平均流速,在已知质量流量后,根据质量守恒定律进而求得流体密度。采用纯物质十二烷及质量比1∶1正辛烷/正庚烷二元混合物标定测量系统精度,实验结果与文献值的最大误差在±1.2%以内,平均相对误差小于0.6%。在此基础上,对压力p = 3.0、4.0、5.0 MPa,温度T = 302.0～529.6 K,吸热型碳氢燃料密度进行测量,该方法的应用为超临界压力下吸热型碳氢燃料密度的准确测量提供了新思路。     

用密度泛函理论研究二元体系的液液界面张力

应用密度泛函理论和统计缔合流体理论建立了二元液液界面的状态方程 ,通过纯流体汽液平衡时的压力数据和液相密度数据回归了非极性流体和极性流体的链节参数 .将界面分层 ,使用已建立的状态方程和回归的纯流体链节参数 ,根据界面各微层达到相平衡时化学势相等的原则计算了液液界面层的厚度和液液界面中的密度分布 ,预测了 16个水 -有机溶剂二元体系的液液界面张力 .计算结果与实验值符合情况良好 .     

基于波理论的涡街流量计雾状流测量模型

建立了雾状流条件下涡街流量计的修正模型。雾状流中液相的存在会导致涡街流量计的测量误差,通过将以往研究者在单相流中对Karman涡街现象的认识及取得的研究成果作为基础,并结合实验流体本身所具有的动力特点,利用Karman涡街波传递的理论分析了非定常不稳定的雾状流流场中的Karman涡街现象,构建了双向耦合的气液两相流动力学模型。试验结果显示,当液相体积含率从0～0.13%变化时,模型修正后的结果与实际值较为接近。     

用密度泛函理论研究非极性混合流体表面性质

应用密度泛函理论研究了二元非极性混合流体的表面性质.分子作为球形链处理,不同分子内的两链节相互作用以硬核Yukawa势能表示.为了避免计算中势能作用数值积分截断导致的误差,采用了合理的长程校正方法.根据微扰理论建立了流体的状态方程以计算汽液相平衡.从纯流体汽液相平衡数据回归得分子的链节作用参数ε/k、d和m_s,这些参数预测纯流体表面张力时可获得较好结果.继而引入混合参数k_ij表示不同分子链节作用情况,计算了6种非极性混合流体的汽液相平衡、表面张力、表面密度剖面.结果表明,本方法应用于二元非极性流体混合物时汽液表面张力计算值与实验值符合良好,同时显示某些二元混合流体表面区可能出现组分的相对富集现象.     

提高涡街流量计精度的一种补偿算法及实现

通过对涡街流量计的仪表常数随着流速的变化而略有起伏这个规律的观察与总结,建立数学模型,并根据这个数学模型,可以在不同的流速段对仪表常数做适当的补偿,可以提高涡街流量计的计算精度。该方案通过单片机809C51实现。     

混合气体流量测量优化方案

以炼化干气为例,对混合气体的物理状态进行分析,结合容积式流量计、涡轮流量计及涡街流量计等的不同流量特性,计算炼化干气的工况状态密度在偏离设计状态密度不同程度的情况下各种流量计测量结果的偏差变化。     

油气管道非线性振动基频分析

为了揭示外部激励、油气介质对管道非线性自由振动基频的影响规律,首先基于Euler-Bernoulli非线性几何方程和Hamilton原理,建立油气管道非线性动力学控制方程,然后通过伽辽金法和同伦摄动法,求得油气管道频幅关系、位移-时间曲线的一阶近似解和基频理论解。计算结果表明:推导的理论解与相关文献和实验数据相吻合。管道基频与外激励初始振幅正相关,与介质流速和密度负相关。过高的流体流速或密度易引起管道基频急剧降低。当有适当的扰力出现时,管道系统易发生较大受迫振动乃至共振失效。     

乳化炸药密度在线快速检测与调控技术研究

为了实现乳化炸药生产过程中密度在线快速检测与调控,提出了一种运用数字速率技术间接测量样品密度的新方法,建立了样品密度在线快速检测与调控系统.研究表明,乳化炸药密度与速率检测系统电流输出信号之间呈现较好的线性关系;通过对比样品密度在线检测试验值与真实值,结果表明,密度在线检测精度可达0.2％,能够满足生产实践需求,同时该...     

泰勒反应器中流体流动及停留时间分布研究

以水为介质对泰勒反应器中的流动状况和停留时间及其分布(RTD)进行了研究,并应用计算流体力学(CFD)技术对反应器进行了流场模拟和RTD计算。结果表明,在实验范围内,泰勒反应器中停留时间分布受内筒转速、轴向流动速率等因素影响,基于流体力学计算结果与实验结果基本相当。     

NUMERICAL SIMULATION OF THE TRANSPORT OF VORTEX RINGS IN AN INITIALLY STRATIFIED FLUID

A numerical study of the formation and transport of vortex rings in a cylindrical tank initially occupied by a thermally stratified fluid is presented. A control-volume based finite-difference technique (Patankar's SIMPLER method) is used. The formation of a vortex ring was simulated by injecting a quantity of a fluid through a tube centrally located near the free surface. Initially, the fluid in the tank was stably thermally stratified, with a low density in the upper half and higher density in the lower half. Buoyancy effects were considered. Modelling aspects are discussed and the formation and transport of a vortex ring in the stratified fluid as well as the resulting mixing characteristics are presented.     

Computational fluid dynamics simulation of hydrodynamics in an uncovered unbaffled tank agitated by pitched blade turbines

Computational fluid dynamics (CFD) simulations were applied for evaluating the hydrodynamics characteristics in an uncovered unbaffled tank agitated by pitched blade turbines. A volume of fluid (VOF) method along with a Reynolds stress model (RSM) was used to capture the gas-liquid interface and the turbulence flow in the tank. The reliability and accuracy of the simulations are verified. The simulation results show that the vortex can be divided into central zone and peripheral zone, and flow field in the tank can be divided into forced vortex flow region and free vortex flow region. With the increase of impeller speed, the vortex becomes deeper, while the critical radius of the two zones keeps almost unchanged. The impeller clearance and the rotational direction have little effect on the vortex shape. The vortex becomes deeper with increasing of the impeller diameter or the blade angles at the same rotational speed. Power number is little influenced by the impeller speed, and decreases by about 30% when impeller diameter varies from 0.25T to 0.5T. When blade angle varies from 30° to 90°, power number increases by about 2.32-times. Power number in uncovered unbaffled tank is much smaller than that in baffled tank, but is very close to that in a covered unbaffled tank. The discrepancy of power number in uncovered unbaffled tank and that in covered unbaffled tank is less than 10%.     

Number density of turbulent vortices in the entire energy spectrum

In coalescence and break‐up modeling, vortex number density and size distributions of turbulent vortices are required to calculate the rate of interaction between continuous and dispersed phases. Existing number density models are only valid for the inertial subrange of the energy spectrum and no model of the vortex number density, valid for the entire energy spectrum, is available. The number density of the turbulent vortices were studied and modeled for the entire energy spectrum including the dissipative, inertial, and energy containing subranges. It was observed that the new number density model depends on vortex size, local turbulent kinetic energy, and dissipation rate. Moreover, the new number density model was validated by the number density distributions quantified in a turbulent pipe flow. The turbulent vortices of the pipe were identified and labeled using a vortex‐tracking algorithm that was developed recently by the authors. © 2014 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 60: 3989–3995, 2014     

旋风分离器内旋进涡核的实验研究

采用热线风速仪测速,ＦＦＴ 变换处理数据的方法,研究直切式旋风分离器内旋进涡核（ＰＶＣ） 现象。研究表明,涡核旋进运动主要存在于排尘口附近区域内,其频率接近为一常数,且与入口气速成正比,在排尘口附近,涡核形成高强度的偏心摆动。     

LIQUID DISPERSION MECHANISMS IN AGITATED TANKS: PART I. PITCHED BLADE TURBINE

An oil into water dispersion, created by a pitched blade turbine, was observed using high speed, stereoscopic motion pictures. Two different dispersion mechanisms were responsible for the break-up of the oil drops, even though both mechanisms occurred in the vortex system trailing from the impeller blade tips. The first mechanism could be described as ligament stretching, since large oil drops were stretched by fluid shear to form elongated ligaments, which subsequently ruptured into small drops. The second mechanism was turbulent fragmentation, where large oil drops were shattered into large droplet clouds the instant they entered the trailing vortex system. Observations of the oil drops undergoing ligament stretching also indicated that velocities in the trailing vortex system were proportional to impeller tip speed.     

LIQUID DISPERSION MECHANISMS IN AGITATED TANKS: PART I. PITCHED BLADE TURBINE

An oil into water dispersion, created by a pitched blade turbine, was observed using high speed, stereoscopic motion pictures. Two different dispersion mechanisms were responsible for the break-up of the oil drops, even though both mechanisms occurred in the vortex system trailing from the impeller blade tips. The first mechanism could be described as ligament stretching, since large oil drops were stretched by fluid shear to form elongated ligaments, which subsequently ruptured into small drops. The second mechanism was turbulent fragmentation, where large oil drops were shattered into large droplet clouds the instant they entered the trailing vortex system. Observations of the oil drops undergoing ligament stretching also indicated that velocities in the trailing vortex system were proportional to impeller tip speed.     

带纵向涡发生器喷动床内颗粒流动特性PIV实验

针对喷动床内环隙区颗粒缺少横/径向运动的特点,通过实验将纵向涡流发生器及纵向涡流效应引入喷动床。采用粒子图像测速技术研究了在内径为152 mm的喷动床内纵向涡流及颗粒设计参数对喷动床内喷射区及环隙区颗粒相径向速度的影响,研究结果表明,纵向涡发生器在扰流元件上方横截面内颗粒相运动出现大量二次涡流,相比较于无纵向涡流扰流件情况,喷动床内的颗粒径向速度得到了显著增加,表明纵向涡发生器能够增强颗粒相在喷射区及环隙区的径向运动能力。在喷动床稳定喷动范围内,颗粒直径及颗粒密度越小,纵向涡流对颗粒相径向运动的强化效果越佳。     

低密度修井液的室内研究

本实验主要研究密度低于0.8g/cm3的泡沫修井液体系。该体系用SDS(十二烷基硫酸钠)与QHP的复配物(最佳配比是4∶1,最佳加量1.5%)作为起泡剂,用0.08%的十二醇、1.2%的CM C和HEC混合物(比例为3∶2)以及0.2%的明胶作为稳泡剂。制备出的泡沫稳定性好,具有好的抗盐性,抗油性,抗水性,可用作低压油井修井液。     

近红外光谱在中药大黄乙醇提取液快速分析中的应用研究

用声光可调滤光器(AOTF)-近红外(NIR)光谱法在线分析中药大黄乙醇提取液比重及大黄素含量,用偏最小二乘(PLS1)法分别建立NIR光谱与含量、比重的校正模型。结果表明,提取液NIR光谱与比重、含量的校正模型相关系数R2分别为0.989 0,0.988 4,相对偏差分别为0.26%,2.66%,精密度分别为0.15%,2.84%;5 h稳定性分别为0.13%,2.03%,回收率分别为99.8%,95.6%。该方法具有快速、直接、多成分同时测定特点,并能实现现场在线分析。