FL燃气调压器变量相关性和调压性能下降原因

基于统计学原理,基于FL燃气调压器运行历史数据,研究FL燃气调压器运行过程中各变量之间的相关性。进行调压器性能检测实验,分析调压性能下降的原因。调压器出口压力和负载压力呈中度负相关。出口压力和流量呈一般负相关。流量和开度呈显著正相关。流量滞后于负载压力变化;将流量曲线的时间向前移动70 s,形式调整后流量;调整后流量与负载压力的相关系数可达0.5以上,呈中度正相关。调压性能下降的原因主要是弹簧弹性下降、燃气中混有杂质。     

燃气系统中调节阀相对开度变化时流量的计算

分析了燃气系统中影响调节阀流量的因素,调节阀流量与流通能力系数、相对开度等因素有关。通过对调节阀理想流量特性的分析,推导出流通能力系数与相对开度的数学关系式,再利用流量与流通能力系数的关系,得到流量与相对开度的数学关系式。用此方法计算的流量与实际流量的相对误差不超过8％,表明此流量计算方法具有工程实用价值。     

基于调节阀实际特性的空调机组优化控制

通过实测获得一空调机组调节阀实际的开度-相对流量特性.利用所建立的空调机组仿真平台,模拟研究了按照调节阀理想工作曲线制定的控制参数对实际调节阀的控制效果.结果显示,此调节阀在实际运行时单位开度变化引起的流量变化较理想流量特性下大,导致调节阀开度超调及房间温度波动,控制效果与预期理想效果出现偏差.基于调节阀实际流量特性,...     

正确选择流量调节阀是实现供热系统流量平衡的关键

供热系统出现水力失调、冷热不均现象，其中一个重要原因是流量调节阀选择不当。本文就各种流量调节阀的调节特性、阀权度和流量调节阀的正确选择、应用进行了阐述并提出了相关建议。     

燃气限流调节阀的可调比及精度

燃气输配供需双方严格执行精确的年月同供气计划,但在高峰时段用户不会自动减小负荷,供方只能采用调节阀限制下游用户的流量提取,双方均关注调节阀的运行状况。文章通过对限流过程中某种调节阀开度及进出口差压变化引起流量特性的畸变,分析不同限流值时调节阀开度变化规律,计算并绘制出限流调节过程的可调比曲线和精度曲线,为合理选择调节阀的参数提供参考计算方法。     

套筒式水量连续调节阀导纳函数的试验研究及其应用分析

针对水量电动连续调节阀在管网中的动态调节特性描述不准确等问题,基于调节阀前后压降关于流量及阀门流阻系数的数学模型,提出了调节阀导纳的定义。通过测量不同开度下调节阀前后压差及流量,建立了调节阀导纳关于开度的数学回归方程。基于该方程对其理想流量特性及工作流量特性进行了量化描述。     

膨胀机燃气调压的发电性能研究

提出一种膨胀机调压发电系统,在进行燃气调压的同时回收压力能发电,满足调压设施用电需求。建立系统的热力学模型,研究系统的发电性能。研究结果显示,在进气绝对压力0.6 MPa、排气绝对压力0.1 MPa的条件下,系统日均电能回收率为25.1%,日净发电量60.9 kW·h。该系统可有效解决无电燃气调压设施的用电问题,产生较好的环境效益。     

三通调节阀的选用和安装

三通调节阀广泛应用于调节热交换器冷热水的进出流量或温度,以满足系统冷热交换的需要。为了得到良好的调节性能,达到人们所希望的开度—热量特性基本按线性变化。本文对不同使用条件下选用何种开度—流量特性进行了论述;也阐述了三通阀应如何安装。强调设计人员在设计中应指明所选用的是何种开度—流量特性,以及三通阀在系统申的水流方向。     

LNG接收站燃料气调压工艺的改进与应用

LNG接收站燃料气系统一般通过压力调节阀和燃料气空气、电加热器对燃料气进行调压、升温以供下游用户使用,调压精度较低且调压范围受限。论文提出一种新型LNG接收站多路异压燃气管路工艺设计方法,利用燃气调压橇装系统替换原有工艺中的燃料气空温加热器、电加热器及配套调压措施,具有调压级数多、调压范围大、间歇供气、安全性突出等优点。此新方法已经运用在某接收站的工程设计中,取得了良好效果。     

中低压燃气智能调压系统

介绍智能调压器和中低压燃气智能调压系统的组成。中低压燃气智能调压系统以智能调压器为基础,通过增加压力变送器、阀位开关、带阀位开关的进出口球阀、PLC控制器等组成,具备远程监控功能、故障自诊断功能、流量模拟功能等。     

Characterization of two-phase flow in a single rock joint

An experimental study using a triaxial apparatus was used to analyze the two-phase flow patterns in jointed rock specimens. Rock specimens having a single natural fracture were tested for two-phase flow of water and air. Triaxial tests were conducted to characterize the two-phase flow through fractured granite specimens at low confining pressures. It was found that for a relatively smooth joint (JRC<6), bubble flow pattern occurred within the rock joint when the gas velocity is below 15 m/s. The average velocity of water usually varied between 0.1 and 0.5 m/s for bubble flow patterns. In this velocity range, air bubbles were able to form along the joint walls or to be randomly displaced within the water phase. When the gas velocity inside the rock joint exceeded 22 m/s, the flow patterns took annular form for non-zero capillary pressures (i.e., injected gas pressure is not equal to injected water pressure). At elevated (>0.25 MPa) gas injection pressures, the gas occupied the main part of the fracture and the liquid was able to flow as an unstable film forming an annular flow along the joint. When the annular flow developed, the mixture flow pattern was independent of the air flow velocity. This was due to the fact that once the injected air velocity reached a critical value (i.e., 20 m/s), water velocity inside the joint was negligible for a given confining pressure and injected water pressure. Further increase in inlet air pressures developed a single-phase air flow with no water flow.     

An analysis of compartment fire doorway flows

A mathematical study is made to compute the doorway flow behavior due to fire in a room. Two approaches were taken, first a model attempting to include the effect of fire entrainment and vent mixing; second was a model based on an ideal point source plume fire—both in the zone model concept. Limiting analytic results were found for the latter to give insight into the physics. The results were compared to available flow data, and an approximate formula was developed to predict the doorway mass flow rate to within 20% for a wide range of fire conditions. CFD computations were also explored using FDS. Results are compared from FDS and the zone model with experimental data for a wide range of variables.     

Evaluation of low flow estimation techniques for ungauged catchments

Low flow indices are of interest for a number of water‐related applications. Conventionally, low flow indices are derived from continuous streamflow data; however, these data may not always be available for analysis. A number of techniques have therefore been developed for low flow estimation in ungauged catchments. These approaches vary in complexity and in the amount of initial data required to generate the low flow model. In the UK, software is available which assists in low flow estimation for ungauged catchments. However, certain desktop studies only require a simple evaluation of low flows, with specific low flow indices, such as the Q₉₅ index, being of interest. In this case, the use of such software may not be justified or required in the first instance. This paper demonstrates that a simple regression model is adequate for low flow estimation for multisite analysis where the order magnitude of the low flow index is of importance.     

Study on performance of horizontal single pass shell and multi-tube heat exchanger with baffles by air bubble injection

ABSTRACT

The single pass shell and multi-tube heat exchanger with double segmental baffles'’ performance improvement were experimentally investigated by two methods of air injection into shell side when an increase in air bubble created an effect in the corresponding values of shell and tube heat exchanger such as the overall heat transfer coefficient, effectiveness, NTU and the pressure loss. In the first method, air bubble injection into shell side was parallel to the cold water flow; also in the second method, air bubble injection into shell side was cross flow to the cold water with different air flow rates to calculate approximately the most favourable performance conditions. 1–6?LPM of air flow rates and 10–20?LPM shell side water flow rates were transformed with constant tube side hot water flow rate.     

The importance of gully flow modelling to urban flood simulation

ABSTRACT

Urban flood simulation often ignores or simplifies the function of underground gully systems due to data and computational limitations. To discover the influence of gullies on urban flooding, a novel approach is proposed in this study, by fully-coupling a 1D gully flow model (GFM), a 1D sewer flow model (SFM), and a 2D overland flow model (OFM) to simultaneously simulate the flow exchanges between surface, gullies and sewer pipes. This fully-coupled approach is compared with a simplified approach which directly introduces surface water into sewer pipes without being via gullies. The validation results show that the fully-coupled approach considerably reduces the underestimation of flood extent by 27% compared with the simplified approach. Without considering the capacity of lateral tubes between gullies and sewer pipes, the simplified approach over-drains the surface water into sewer pipes. The modelling of gully flow is crucial for correctly evaluating the efficiency of drainage systems.     

基于Fluent的轴流式风机风筒内部流场分析

针对现有的森林灭火设备不能完全适应森林火场的恶劣环境的问题,设计了一种节水、环保、高效、安全的电控自行走式风水灭火装备。利用三维软件 Solidworks 对自走式风水灭火机进行整机的结构设计,选定风机形式是轴流风机。采用 Fluent软件对轴流风机内部流场进行分析,建立模型,得到流量图和速度云图,分析认为整机装备达到灭火要求。最后进行了样机的试制,完成样机对灭火的功能性试验,试验结果表明：样机的灭火时间在可控范围内,证明该机器的设计符合预计的设计要求。     

The effects of vegetation distribution pattern on overland flow

Soil erosion is a major environmental problem. Vegetation, on the other hand, plays an important role in controlling soil erosion. The goal of the study is to examine the effects of the distribution pattern of vegetation on water flow. The vegetation parameters involved included the direction of plant rows, plant stem diameter and row spacing. To study how vegetation affects the flow of water on slopes, flume simulation experiments were conducted using three different plant row directions, three different plant diameters and three row spacing. Experimental slope is fixed, slope ratio of 1.0%. The hydraulic characteristics of the slope under the three vegetation distribution patterns are explored. The results showed that the pattern of vegetation distribution significantly affected the resistance of vegetation to water flow and pattern on this slope. When the angle (θ) between plant row and water flow directions decreased, the plant diameter (d) increased, or the row spacing (a × a) decreased, the Darcy–Weisbach resistance coefficient (f) for water flow became larger. Simultaneously, the Reynolds and Froude numbers (Re and Fr) both became smaller. In experimental procedure condition, the change rate of f, Re and Fr were analysed by linear regression, the θ decreased every 10°, the average increase rate of f was 6.6%, the average decrease rate of Re and Fr were 2.0 and 3.0%. The d increased every 0.001 m, the average increase rate of f was 41.6%, the average decrease rate of Re and Fr were 11.2 and 12.2%. The a × a decreased every 0.01 m, the average increase rate of f was 45.2%, the average decrease rate of Re and Fr were 11.7 and 10.7%. The flow depth h increased every 0.01 m, the average increase rate of f and Re were 13.6 and 25.2%, and the average decrease rate of Fr was 10.4%. The experimental procedure results will be valuable for not only revealing the hydraulic characteristics of flow over vegetation land, but also the optimisation of the distribution of vegetation on a slope.     

虹口港、杨浦港地区旱流污水截流工程设计水量的论证

对虹口港、杨浦港地区近几年来产业结构调整 ,污染大户的外迁 ,工业废水量明显减少的情况进行调研 ,通过对现状污水量的采集 ,规划、现状水量的测定等进行了详细的分析和论述 ,比较客观合理确定虹口港、杨浦港地区旱流污水截流工程的设计污水量     

The mathematical model for steady magnetohydrodynamic flow between parallel porous plates with an angular velocity

ABSTRACT

The model is developed as the steady magnetohydrodynamic (MHD) flows with an angular velocity between parallel porous plates are considered. The problem is solved analytically by using similarity transformation, whose solution deals with increasing fluid flow with an angular velocity. The applications in MHD are power generators, polymer technology, cooling system, petroleum industry, aerodynamics heating used. The objective of this paper is to analyse the steady MHD flow of viscous fluid with an angular velocity between parallel porous plates when the fluid is being withdrawn through both the walls of the channel at the same rate. The problem is reduced to a third-order linear differential equation which depends on a Suction Reynolds number R and M ₁ for which an exact solution is obtained.     

Assessing the Flow Needs of Rivers

Human and environmental needs sometimes conflict: the more for the environment, the less for the people and vice versa . Environmental needs include soil water, wetlands, lakes, rivers and estuaries. The paper recognizes that all these aspects must be catered for, but focuses on the flow needs of rivers; in particular, it suggests a method to determine river-flow targets which are objective, sustainable, integrated with river-quality characteristics and economically justified. Such targets could help the Environment Agency to balance human and environmental water needs in a rational manner.