Discrete Particle Simulation of Gas-Solid Flow in Air-Blowing Seed Metering Device

In this paper,the gas and seed flow characters in the air-blowing seed metering device are investigated by using the coupled computational fluid dynamics and discrete element method(CFD-DEM)in three dimensions(3D).The method of establishing boundary model based on the computer-aided design(CAD)drawing,has been used to build the boundary model of seed metering device.The 3D laser scanning technique and multi-element method are adopted to establish the particle model.Through a combined numerical and experimental effort,using 3D CFD-DEM software,which is based on the in-house codes,the mechanisms governing the gas and solid dynamic behaviors in the seed metering device have been studied.The gas velocity field and the effect of different rotational speeds and air pressures on the seeding performance and particle velocity have been studied,similar agreements between numerical and experimental results are gained.This reveals that the 3D CFD-DEM model established is able to predict the performance of the air-blowing seed metering device.It can be used to design and optimize the air-blowing seed metering device and other similar agriculture devices.

Energy flow problem solution based on state estimation approaches and smart meter data

Accurate electric energy(EE)measurements and billing estimations in a power system necessitate the development of an energy flow distribution model.This paper summarizes the results of investigations on a new problem related to the determination of EE flow in a power system over time intervals ranging from minutes to years.The problem is referred to as the energy flow problem(EFP).Generally,the grid state and topology may fluctuate over time.An attempt to use instantaneous(not integral)power values obtained from telemetry to solve classical electrical engineering equations leads to significant modeling errors,particularly with topology changes.A promoted EFP model may be suitable in the presence of such topological and state changes.Herein,EE flows are determined using state estimation approaches based on direct EE measurement data in Watt-hours(Volt-ampere reactive-hours)provided by electricity meters.The EFP solution is essential for a broad set of applications,including meter data validation,zero unbalance EE billing,and nontechnical EE loss check.

Generation of Arbitrary Pressure Pulsation of Wide Frequency Range for Flow Meter Testing in a Laminar Gas Pipeline

The present paper presents a device to test flow meters under an arbitrary pressure pulsation in a gas pipeline with a laminar flow containing frequency components up to 50 Hz, with the amplitude reaching hundreds of pascals. In order to reduce flow noise, the device has a strainer-like element connected to a pipeline under test and uses an open-loop control law based on the frequency response test. The control signal is calculated by adding the inputs to obtain each of the sinusoidal waves included in the original wave, which was decomposed by Fourier analysis. The validity of the developed method is demonstrated through the generation tests of superimposed pressure waves containing frequency components up to 50 Hz. Analysis of the relative uncertainty demonstrated the relative uncertainty to be less than 10% when the generated pressure is larger than 360 Pa.

Vacuum and Air Flow for 2QXP-1 Vacuum Precision Seed Metering

Vacuum precision seed metering is the key part of vacuum seed planter. Planting performance of planter is affected by vacuum and air flow which are important parameters for choosing fan. Effects of qualification percent and miss percent on air chamber vacuum 3, 4, 5 and 6 kPa were studied at different operating speeds. The results showed that operating performance of the seed metering was excellent when air chamber vacuum was 5 and 6 kPa, which air flow was 7.4-8.0 m3·s-1 and 8.0-8.8 m3·s-1 , respectively.

Computer Aided Design of Differential Pressure Flow Meters

New methodology of designing the differential pressure flow meters for fluid energy carriers is developed in order to provide minimum uncertainty of results of flow rate measurement. This methodology is implemented in “Raskhod-RU” CAD system for computer aided design and calculation of differential pressure flow meters. “Raskhod-RU” CAD meets the requirements of new Standards implemented in CIS countries (GOST 8.586.1,2,3,4,5-2005) and provides accomplishment of the following tasks: verification of conditions (constraints) for application of the differential pressure method according to the requirements of new Standards;calculation of parameters of primary device, pipe straight lengths and flow meter in general according to the requirements of new Standards;calculation of uncertainty of results of fluid flow rate and volume measurement.

AutoFlow在定容控制通气模式中的应用

目的探讨AutoFlow(自动变流)在机械通气定容控制通气模式中对患者气道压力和血液动力学的影响。方法 71例接受机械通气的患者随机分为观察组(SIMV-PSV-PEEP+AutoFlow)和对照组(SIMV-PSV-PEEP),采集相关数据进行统计学分析比较。结果在SIMV-PSV方式基础上加用AutoFlow,能显著降低气道吸气峰压(PIP)和气道平均压(Pmean),气道阻力(R)有减小,差异有显著性;观察组和对照组患者的血流动力学监测结果差异无显著性。结论 SIMV定容控制通气模式联合AutoFlow既可以保证潮气量又避免气道压过高,对血液动力学影响不大。

OpenFlow交换机动态共享限速机制的研究

每流限速一直以来都是互联网服务质量保障(QoS)的一大挑战,由于受到硬件资源的限制,很难找到一种快速高效的算法在数据包级对流量进行区分限速.OpenFlow1.3协议对每流限速(Meter)部分,给出了具体定义和描述,该文参照该协议标准,提出了具体的Meter实现方案,并在ONetSwitch硬件平台上,进行了实验验证和性能测试.本文通过对网络流量的统计分析,发现网络中共存的流数量往往只占总流量的万分之一,因此使多条流分时共享硬件资源,可以有效解决每流限速的难题.参考动态队列共享(DQS)的思想,该文提出动态共享限速(DMS)算法,在多条流之间进行调度,实现多条流分时共享限速通道,在硬件资源受限,限速通道数量一定,同时需要限速的流数量大于限速通道数量时,能够有效地实现对各条流进行限速的功能.实验结果表明,Meter能够为每条流有效分配限速通道,从而在网络中对多条流以不同的速率区分限速.

Uncertainty analysis of flow rate measurement for multiphase flow using CFD

The venturi meter has an advantage in its use,because it can measure flow without being much affected by the type of the measured fluid or flow conditions.Hence,it has excellent versatility and is being widely applied in many industries.The flow of a liquid containing air is a representative example of a multiphase flow and exhibits complex flow characteristics.In particular,the greater the gas volume fraction（GVF）,the more inhomogeneous the flow becomes.As a result,using a venturi meter to measure the rate of a flow that has a high GVF generates an error.In this study,the cause of the error occurred in measuring the flow rate for the multiphase flow when using the venturi meter for analysis by CFD.To ensure the reliability of this study,the accuracy of the multiphase flow models for numerical analysis was verified through comparison between the calculated results of numerical analysis and the experimental data.As a result,the Grace model,which is a multiphase flow model established by an experiment with water and air,was confirmed to have the highest reliability.Finally,the characteristics of the internal flow Held about the multiphase flow analysis result generated by applying the Grace model were analyzed to find the cause of the uncertainty occurring when measuring the flow rate of the multiphase flow using the venturi meter.A phase separation phenomenon occurred due to a density difference of water and air inside the venturi,and flow inhomogeneity happened according to the flow velocity difference of each phase.It was confirmed that this flow inhomogeneity increased as the GVF increased due to the uncertainty of the flow measurement.

Performance of a Horizontally Mounted Venturi in Low-pressure Wet Gas Flow

The performance of a Venturi tube used in wet gas flow have been explored mainly under higher-pressure condition, but very often, low-pressure test exists in some oil and gas fields in Tianjin Dagang Oil and Gas Field in China. In this study, the performance of horizontally mounted Venturi meters in low-pressure wet gas flow is discussed. Three 50 mm Venturi meters were tested systematically, with fl values of 0.4048, 0.55 and 0.70, the opera- tion pressure of 0.15 MPa, 0.20 MPa, 0.25 MPa, the gas densiometric Froude number from 0.6 to 2.0, the modified Lockhart-Maretinelli parameter from 0.0022 to 0.06, and the ratio of the gas liquid mass flow rate from 0.5 to 0.99. The effects of modified Lockhart-Maretinelli parameter, pressure, gas densiometric Froude number, diameter ratio, and gas-liquid mass flow rate ratio to the Venturi tube are analyzed with new independent data. Furthermore, low-pressure performance was compared with that under high pressure.

Iterative learning control approach for ramp metering

An iterative learning control scheme is developed to the traffic densitycontrol in a macroscopic level freeway environment. With rigorous analysis, the proposed intelligentcontrol scheme guarantees the asymptotic convergence of the traffic density to the desired one. Thecontrol scheme is applied to a freeway model, and simulation results confirm the efficacy of theproposed approach.

Wet Gas Meter Development Based on Slotted Orifice Couple and Neural Network Techniques

A slotted orifice has many superiorities over a standard orifice. For single-phase flow measurement, its flow coefficient is insensitive to the upstream velocity profile. For two phase flow measurement, various characteristics of its differential pressure （DP） are stable and closely correlated with the mass flow rate of gas and liquid. The complex relationships between the signal features and the two-phase flow rate are established through the use of a back propagation （BP） neural network. Experiments were carried out in the horizontal tubes with 50ram inner diameter, ooerated with water flow rate in the range of 0.2m^3·h^-1 to 4m3·h^-1, gas flow rate in the range of 100m^3·h^-1 to 1000m^3·h^-1, and pressure at 400kPa and 850kPa respectively, where the temperature is ambient temperature. This article includes the principle of wet gas meter development, the experimental matrix, the signal processing techniques and the achieved results. On the basis of the results it is suggested that the slotted orifice couple with a trained neural network may provide a simple but efficient solution to the wet gas meter development.

Methodology for production logging in oil-in-water flows under low flow rate and high water-cut conditions

This study aimed to obtain the production profiles of oil-in-water flow under low flow rate and high water-cut conditions in oil wells.A combination production profile logging composed of an arc-type conductance sensor(ATCS)and a cross-correlation flow meter(CFM)with a center body is proposed and experimentally evaluated.The ATCS is designed for water holdup measurement,whereas the CFM with a center body is proposed to obtain the mixture velocity.Then,a drift-flux model based on flow patterns is established to predict the individual-phase superficial velocity of oil-in-water flows.Results show that the ATCS possesses high resolution in water holdup measurement and that flow pattern information can be deduced from its signal through nonlinear time series analysis.The CFM can enhance the correlation of upstream and downstream signals and simplify the relationship between the cross-correlation velocity and mixture velocity.On the basis of the drift-flux model,individual-phase superficial velocities can be predicted with high accuracy for different flow patterns.

Design and Implementation of an Ultrasonic Heat Meter Based on MSP430F437

Flowing with the reform of the hot water heating method in China, heat meter will enter into households in the near future. A portable ultrasonic heat meter is designed in this paper. The meter uses chip microprocessor MSP430F437 as the data process core, and uses ultrasonic flow sensor to measure flow rate of the hot water, and capture input and output temperatures of the hot water using the thermal resistance sensor Ptl000, and then household energy consumption is calculated via temperature difference between input temperature and output temperature of the hot water multiplied by volume of hot water that is calculated though flow rate integration of hot water. In order to test the performance of the proposed heat meter, experiments is carried out. Both the temperature and flow measurement results satisfy the requirements of accuracy and the heat meter is effective in the heat measurement.

液阻全桥网络负载口独立电液系统节能控制策略仿真

针对传统电液控制系统节流损失大、能耗高、效率低的问题,采用液阻全桥网络搭建了具有负载口独立控制特性的新型电液控制系统,详细研究了该系统在典型四象限负载下的节能控制策略。液阻全桥网络电液系统由5个二位二通比例阀组成,根据其具有的负载口独立控制特性,将系统归纳为传统三位四通、负载口独立和负载敏感3种控制模式。传统三位四通下,两负载口开度控制模拟三位四通进出口耦合形式;负载口独立模式下,采用一腔控制流量另一腔阀口全开的控制策略;负载敏感模式下,控制泵出口压力比进油腔压力高一个定值,从而实现负载敏感功能。在超越负载下,3种模式都使用流量再生回路进行节能控制。AMESim+Matlab联合仿真结果表明,与传统的三位四通模式相比,三位四通流量再生、负载口独立、负载口独立流量再生、负载敏感模式分别节能43.38%、65.27%、77.91%、83.58%。

一种光纤布喇格光栅涡街流量传感器

在流量计量领域中,利用光纤传感技术对涡街流量计量的研究较少,故具有重要的研究意义。该文设计了一种悬臂梁式的光纤布喇格光栅涡街流量传感器,其利用悬臂梁自由端振动使光纤布喇格光栅中心波长发生周期性移位,从而测量涡街频率,得到流体流量信息。温度传感测试实验与流量传感测试实验结果表明,该传感器温度灵敏度为17 pm/℃,涡街流量灵敏度为0.01895 Hz/(L·h^(-1)),非线性误差为2.23%。实验验证了该传感器可应用于液体涡街流量计量。

具有变超越负载的液压调平系统负载口独立控制方法

液压调平系统平台回落过程中存在超越负载,且随着负载重心偏移和平台倾角变化,作用于支腿液压缸的负载力也会随之变化。传统液压系统中负载控制阀或平衡阀在平衡变超越负载时速度控制效果差,容易发生速度抖动。为解决这一问题,采用负载口独立控制技术,针对平台回落时液压缸存在的变超越负载工况,提出对液压调平系统中液压缸有杆腔进行压力控制,无杆腔进行流量控制的压力-流量复合控制方法,建立其数学模型,并进行AMESim和Simulink联合仿真验证。结果表明,在负载力发生突变时,液压缸有杆腔压力和无杆腔流量均可在0.2 s内恢复至控制值,平衡掉系统变超越负载的同时,能够满足系统的速度控制需求。

德尔塔巴流量计K系数数值仿真研究

德尔塔巴流量计采用独特的双龟翼对称型结构,具有压损小、结构简单、可靠性高等优点,已被广泛应用于石油、石化、电力及化工等众多领域。该文使用流体仿真软件对德尔塔巴流量计在不同入口流速下进行仿真,仿真结果表明德尔塔巴流量计的K系数不仅跟自身的结构有关系,还与流速成正比关系,在全量程测量范围内使用一个K系数将造成较大的测量误差。最后使用标准表法水流量标准装置对德尔塔巴流量计在不同流速下进行检定,结果表明在全量程内使用固定K系数将造成测量结果超差。因此需要对德尔塔巴流量计的K系数进行分段设置。

皂膜流量计法测量电池隔膜透气度测试仪透气体积的研究与分析

本文针对葛尔莱法电池隔膜透气度测试仪的有效溯源方法,以玻璃管皂膜流量计为标准器,建立了一种透气体积校准方法,分析了其原理及影响因素,并进行不确定度评定。结果表明:该方法的测量结果准确,不仅能对透气体积进行量值溯源,而且能确保量值的准确性和可靠性。

天然气能量计量核查系统的研究与应用

本文研发了一套基于OCS控制器的天然气能量计量核查系统,针对SICK流量计算机的数据参数,动态配置数据类型、从机地址、字节顺序、读写权限并映射到OCS的%R类本地寄存器,解决了天然气计量核查数据受显示窗口限制预采集的难题。结合现场天然气介质组份、实时工况温度、实时工况压力等数据,使用依据GB/T 11062-2020《天然气发热量、密度、相对密度和沃泊指数的计算方法》所研发的“天然气流量能量计量核查软件”,进行天然气现场数据的能量计量核查。实现了硬件自动化采集预处理,软件自动化快速计算,有效提升了计量的工作效率和可靠性。