LZR-Ⅰ智能蒸汽流量热量积算仪通过鉴定

由长沙市计量仪器仪表研究所研制的LZRⅠ智能蒸汽流量热量积算仪年前在长沙通过省级鉴定。该积算仪可和标准孔板配合测量饱和蒸气的质量流量和热能量;能实时修正蒸气密度、膨胀校正系数及蒸气湿度(<20%);集压力、流量、累计质量、累计热能、输入通道电流测量五种功能于一体。压力测量范围为0～2.5MPa;流量测量范围为0.02～100t/h(量程比1:4);模拟量输入通道3路,0～10mA,输入阻抗500Ω;采用0.5级     

CW-612Y型带压力补偿装置双波纹管差压计

该仪表是带压力补偿的饱和蒸汽流量测量装置,它是在原有CW-610型双波纹管差压流量计基础上应用了一个行之有效的数学模型而研制成功的。文中详细地介绍了该仪表的补偿原理、密度数学模型及系统构成等,并着重阐述了乘法、开方电路的工作原理及其误差分析。     

CEL-52型膜盒差压流量计——压力补偿式蒸汽流量计

CEL-52型膜盒差压流量计是与孔板等节流装置配套、能作压力波动影响补偿的流量仪表,专门用以测量饱和蒸汽流量。本仪表针对工业锅炉饱和蒸汽流量测量中工况常有变动的特定条件,用较简单的组件补偿压力波动影响,从而在蒸汽负荷波动、压力变化幅度较大的情况下,获得一定的测量精确度。相对说来,这是一种"价廉"的仪表,价格约为DDZ-Ⅱ型仪表的 1/3。     

饱和蒸汽流量测量的手动压力补偿

在用差压法测量饱和蒸汽流量时,由于受到工作压力变化的影响,有时会产生较大的测量误差,甚至可达30%以上,在这种情况下,测量也就失去了实际意义。为了克服蒸汽压力变化造成的测量误差,人们提出了各种各样的饱合蒸汽流量测量压力自动补偿方案。     

DCS—T程实施中的流量补偿计算

在DCS工程实施中,为了保证流量测量计量、累积准确,配料合理及控制精确,有效,常会有气体流量温压补偿、分子量补偿或密度补偿计算。本文章以天然气流量补偿计算、饱和蒸汽流量补偿计算和空气流量补偿计算三个工程实例作为典型在编程和软件组态实现上对气体流量补偿进行了阐述。     

流量测量中温度、压力补偿数学模型建立

在流量测量中，为精确测量流量应进行温度，压力补偿修正，本文重点介绍应用计算机建立温度，压力补偿数学模型。     

单片机过热蒸汽流量表的研制

本仪表的设计针对目前过热蒸汽流量测量中存在的密度变化引起较大测量误差的问题,利用回归分析方法拟合出多段密度的压力、温度补偿公式,并以单片机技术在线实现,密度相对误差小于±0.5％,从而获得了较高的测量精度。为生产部门提高计量等级、改善控制质量提供了可能。图3幅。     

差压式流量测量技术问答(七) 节流装置计算及温压补偿计算

47过热蒸汽流量的温压补偿方法如何实现?具体补偿公式是怎样的?过热蒸汽密度与温度、压力不遵守理想气体方程,因此没有已经总结好的物理公式。只能根据过热蒸汽密度与温度、压力的关系找出关联公式或经验公式进行补偿。常用的温压补偿公式见题45的式(45-3)。(见《自动化博览》2011年第6期杂志P50)补偿方框图如图12所示。     

涡街流量计测量饱和蒸汽质量流量和密度补偿法的探讨

采用汽液两相流均相流动模型,分析了涡街流量计在饱和蒸汽质量流量测量中的适用性,结合低压湿蒸汽的物理性质,论述涡街流量计测量饱和蒸汽质量流量的误差与饱和蒸汽干度的关系,还介绍测量饱和蒸汽质量流量的变系数补偿法及其特点.     

蒸汽密度计算的改进

在智能流量计中过热蒸汽密度计算公式基础上,采用加权最小二乘算法,重新计算了密度公式中的多项式系数,使新系数下的密度公式既适用于过热蒸汽也适用于饱和蒸汽密度的温度补偿.     

A mathematical model for a class of frying processes

We present a mathematical model for deep frying in absence of mechanical deformation and in one-dimensional geometry. In the generic stage of the process the inner zone is saturated with liquid water below the boiling point at atmospheric pressure. When the boiling point is reached partial vaporization occurs and a zone of water–vapor thermodynamical equilibrium is formed, followed by a region of pure vapor. The interface between mixed and vapor region can be either a zero saturation surface or a level set of pressure when the latter reaches an imposed constraint. The outmost layer is crust. In each region the governing equations are written for temperature and pressure and the conditions at the interfaces comes out as the corresponding Rankine–Hugoniot relations. Boundary conditions at the crust–oil interface are discussed. Rescaling leads to only moderate simplifications and we are left with a considerably difficult free boundary problem for a parabolic system.     

Satellite-based estimation of surface vapor pressure deficits using MODIS land surface temperature data

Vapor Pressure Deficit (VPD) is a principle mediator of global terrestrial CO₂ uptake and water vapor loss through plant stomata. As such, methods to estimate VPD accurately and efficiently are critical for ecosystem and climate modeling efforts. Based on prior work relating energy partitioning, remotely sensed land surface temperature (LST), and VPD, we developed simple linear models to predict VPD using saturated vapor pressure calculated from MODIS LST at a number of different temporal and spatial resolutions. We developed and assessed the LST-VPD models using three data sets: (1) instantaneous and daytime average ground-based VPD and radiometric temperature from the Soil Moisture Experiments in 2002 (SMEX02); (2) daytime average VPD from AmeriFlux eddy covariance flux tower observations; and (3) estimated daytime average VPD from Global Surface Summary of Day (GSSD) observations. We estimated model parameters for VPD estimation both regionally (MOD11 A2) and globally (MOD11 C2) with RMSE values ranging from .32 to .38 kPa. VPD was overestimated along coastlines and underestimated in arid regions with low vegetation cover. Also, residuals were larger with higher VPDs because of the non-linear function of saturation vapor pressure with LST. Linear relationships were seen at multiple scales and appear useful for estimation purposes within a range of 0 to 2.5 kPa.     

PR状态方程在烷烃粘度计算中的应用

本文基于P-V-T与T-u-P联系的相似性，结合Peng—Robinson立方型状态方程（PREOS），建立了一个预测纯烷烃气液相粘度的统一模型。新模型首先运用PREOS方程来计算指定温度下物质的饱和蒸汽压，然后以温度和饱和蒸汽压为独立变量，计算饱和气液相粘度。采用大量实测数据对新模型进行考核的结果表明，新模型在亚临界和超临界范围内，都有较好的计算结果。     

超临界流体技术的工业化应用以及超临界流体的过量焓解析

在近３０年间，超临界流体作为溶剂在施多领域的研究已经取得了较大发展，本文将通过实例对超临界流体在萃取，清洗，结晶，材料制造，废物回收利用，以及反应，合成等方面的应用和研究开发的动向进行说明，同时，超临界流体所拥的大量热能，在新型节能工艺过程中开发利用方面研究引起了我们的兴趣，为此，我们搜集了至今为止已公开表的各处有关超临界汉体的二元混合物过量焓的文献，并结其些体系的过量焓进行了测定，建立了超临界流     

自适应Smith补偿器在基于IP的网络控制系统中的应用

在基于IP网络的网络控制系统(NCS s)中,网络诱导时延变化显著且往往大于一个采样周期.本文引用数据通信中应用广泛的网络回程时间来估计NCS s中时变的全回路网络诱导时延,并提出了一种新的自适应Sm ith补偿器.仿真结果表明,该补偿器能够有效地消除网络诱导时延变化对控制性能的负面影响;结合该自适应Sm ith补偿器所设计的控制系统能够获得很好的控制性能与较强的鲁棒性.     

A direct numerical simulation of axisymmetric cryogenic two-phase flows in a pipe with phase change

An accurate finite-volume based numerical method for the simulation of a cryogenic two-phase flow with phase change heat transfer, consisting of a saturated liquid slug translating in its own superheated vapor in a circular pipe is presented. This method is built on a sharp interface concept and developed on an Eulerian Cartesian fixed-grid with a cut-cell scheme and marker points to track the moving interface. The unsteady, axisymmetric Navier–Stokes equations in both liquid and vapor phases are solved separately. The mass continuity, momentum flux conditions and conservation of energy are explicitly matched at the true boundary between the two phases to determine the interface shape and movement. A quadratic curve fitting algorithm with marker points is used to yield smooth and accurate information of the interface curvatures.It is uniquely demonstrated for the first time with the current method that conservation of mass is strictly enforced for continuous infusion of flow into the domain of computation. The method has been used to compute the velocity, pressure and temperature fields and the deformation of the liquid core. It is also shown that the current method is capable of producing accurate results for a wide range of Reynolds number, Re, Weber number, We, Jakob number, Ja and large property jumps at the interface.     

基于系统输出的嵌套饱和系统抗饱和补偿器设计

针对嵌套输入饱和系统的吸引域扩大问题,本文提出了一种基于系统输出的抗饱和补偿器激发策略,将被控系统输出信号经性能补偿器馈入到抗饱和补偿器激发环节中,形成蕴含系统实时性能信息的抗饱和激发新机制,克服了传统抗饱和激发机制无法直接反映系统性能的缺点.基于上述抗饱和控制新框架,本文建立了抗饱和补偿器及性能补偿器存在的充分条件,并依此构建了优化问题求解最优补偿器增益以实现扩大闭环系统吸引域的目的.仿真结果表明本文方法的有效性.     

基于蒸汽压方程下的管道煤气流量微机测量系统

基于水的蒸汽压方程下，建立工况下管道煤气流量新的计量模型，由该计量模型的应用可知，该模型中不再要求建立管道煤气中不同温度下所对应的水蒸汽饱和压力数据库，从而可以大大简化管道煤气流量计量软件，在流量计设计范围内可以快速难确地实现管道煤气流量实时在线计量。     

FCC油品质量指标智能监测系统的数据挖掘与修正技术

为使ＦＣＣ油品质量指标智能监测系统更加有效地实时预测从人平行 的汽、柴油重要质量指标,本文利用模糊匹配技术和计算机网络技术,建立了基于稳定历史工竞的数据挖掘及修正子,并在实际生产装置中稳定运行结果表明,该子系统能更加有效、对稳定汽油蒸汽压、粗汽油干点和轻柴油凝点进行实时修正,从而提高了ＦＣＣ油品质量指标明监测系统的预测精度和运用水平。     

Adaptive Pseudo Inverse Control for a Class of Nonlinear Asymmetric and Saturated Nonlinear Hysteretic Systems

This paper aims at eliminating the asymmetric and saturated hysteresis nonlinearities by designing hysteresis pseudo inverse compensator and robust adaptive dynamic surface control(DSC)scheme.The"pseudo inverse"means that an on-line calculation mechanism of approximate control signal is developed by applying a searching method to the designed temporary control signal where the true control signal is included.The main contributions are summarized as:1)to our best knowledge,it is the first time to compensate the asymmetric and saturated hysteresis by using hysteresis pseudo inverse compensator because the construction of the true saturated-type hysteresis inverse model is very difficult;2)by designing the saturated-type hysteresis pseudo inverse compensator,the construction of true explicit hysteresis inverse and the identifications of its corresponding unknown parameters are not required when dealing with the saturated-type hysteresis;3)by combining DSC technique with the tracking error transformed function,the"explosion of complexity"problem in backstepping method is overcome and the prespecified tracking performance is achieved.Analysis of stability and experimental results on the hardware-inloop platform illustrate the effectiveness of the proposed adaptive pseudo inverse control scheme.