离心泵故障诊断及实例分析

以迁钢离心泵的实际运行情况为背景,通过举例分析了离心泵在工作过程中的典型故障及解决方案,为离心泵故障的诊断提供参考。     

浅谈变频调速装置在风机及水泵中的应用

某公司为降低成本,节能降耗,对负载变化较大的风机、水泵引进变频调速技术,通过调节风机、水泵的转速来调节其提供的风量、流量,取得了良好的节能效果。     

离心泵流量调节方式对耗能的影响

发电厂在运行中随时调节负荷，包括各系统流量，涉及到离心泵的流量变化．对离心泵定速和变速两种运行方式调节流量时的耗能和效率分析结果表明：变速调节方式耗能少，且经济效益好．     

高压变频器在风机泵类等设备中的应用

介绍了高压大功率变频器在风机泵类等设备上的成功应用,以达到节能减排的效果。     

锅炉烟气飞灰对离心式引风机叶轮的影响及处理

１前言莱钢热电厂目前有５台锅炉,担负着莱钢的蒸汽供应。锅炉采用强制通风,主要燃料是烟煤,燃烧后的烟气通过引风机吸引力强制排出。经除尘后烟气仍含有部分灰分,细小的尘粒对叶轮会产生冲刷并且部分粘结在叶片上影响叶轮的动平衡,导致风机运行中产生振动,严重时影响设备安全运行,甚至会造成事故停炉,影响蒸汽供应。２影响原因烟气中的水分来源于燃料自身、水力除渣设备及锅炉蒸汽吹灰产生的水分。烟气含有的不饱和水分导致灰分颗粒潮湿具有粘性并使风机叶轮粘灰,特别是４＃锅炉装有氨水脱硫装置,部分水蒸汽会随烟气进入引风机,…     

Parameters Affecting Hydraulic Behavior of Aerated Lagoons

Tracer studies were performed at the full-scale St-Hermas aerated lagoon, Quebec, Canada, and a dynamically similar laboratory model to determine the effects of the water flow rate and aeration rate on hydraulic mixing. The tracer study E-curves were extrapolated to ensure conservation of the tracer mass within the system and in turn were analyzed using a two-celled compartmental model. The results of the compartmental model analysis demonstrate that the water flow and aeration rates both influence the percentage of dead zones and bypassing within the system, with the water flow rate being the dominant parameter. This study therefore concludes that hydraulic mixing of aerated lagoons is significantly affected by the water flow and aeration rates. The ability to demonstrate that these hydraulic parameters affect the mixing of aerated lagoons is attributed to the E-curve development and the compartmental model analysis used in this study.     

Centrifugal Modeling of Seismic Behavior of Large-Diameter Pipe in Liquefiable Soil

This study focused on the behavior of a large-diameter burial pipe with special reference to its stability against flotation subject to soil liquefaction. Centrifugal modeling technique was used where the results are presented for a total of eight shaking table tests conducted on the burial pipe in a laminar box under 30g gravitational field. The ground was prepared with Nevada sand at a relative density of 38% and shaken with a sinusoidal wave at an amplitude of 0.5g. The use of a viscous fluid in a saturated soil deposit satisfied the time scaling relationships of both dynamic and dissipation phenomena. The centrifugal modeling technique simulated flotation of pipeline as the soil liquefied. A technique that used gravels and geosynthetic material was used to mitigate flotation. The response of the soil deposit, in terms of acceleration and excess pore pressure, was investigated. The uplifting of the pipe, earth pressure response and ground surface deformation were also presented. Based on the test results, a design procedure was proposed for the burial pipe in resisting flotation due to soil liquefaction. The deadweight and stiffness of the gravel unit, which was confined by geosynthetic, were important items in design.     

Media-Induced Hydraulic Behavior and Performance of Upflow Biofilters

Laboratory studies were conducted to assess the influence of media-related factors such as porosity, specific surface, and pore size on hydraulic behavior and performance of upflow anaerobic biofilters (ABFs). Three 15-L upflow biofilters, each packed with different support media, were subject to identical synthetic protein-carbohydrate substrate with chemical oxygen demand (COD) concentrations ranging from 2,500 to 10,000 mg∕L, and hydraulic retention times from 15 to 30 hours, corresponding to organic loading rates (OLRs) varying from 2 to 16 g COD∕L∕d. Tracer studies were carried out to characterize hydraulic behavior of the biofilters containing media with and without biomass, designated as dirty-bed and clean-bed, respectively. The results indicate that hydraulic flow regimes in all biofilters were characterized by a plug-flow pattern with a large extent of dispersion under clean-bed conditions. The tracer response curve under dirty-bed conditions operating at an OLR of 16 g COD∕L∕d reflects more closely the response of a mixed-flow reactor than that of a plug-flow unit, which suggests that there is significant short-circuiting in the ABFs. Waste treatment performance indicates that the biofilter associated with media of the largest pore size and porosity consistently demonstrated the highest COD removal from 96% to 73% at loadings varying from 2 to 16 g COD∕L∕d. The same reactor exhibited the lowest magnitude of dispersion along with minimum dead space within the bed from the tracer analysis. This implies that the use of support media with larger pore size and porosity may reduce the extent of short-circuiting, leading to better waste treatment performance. Increasing the media specific surface at the expense of media porosity may result in lower treatment performance in upflow anaerobic biofilters.     

Transient Modeling of Arbitrary Pipe Networks by a Laplace-Domain Admittance Matrix

An alternative to the modeling of the transient behavior of pipeline systems in the time-domain is to model these systems in the frequency-domain using Laplace transform techniques. Despite the ability of current methods to deal with many different hydraulic element types, a limitation with almost all frequency-domain methods for pipeline networks is that they are only able to deal with systems of a certain class of configuration, namely, networks not containing second-order loops. This paper addresses this limitation by utilizing graph theoretic concepts to derive a Laplace-domain network admittance matrix relating the nodal variables of pressure and demand for a network comprised of pipes, junctions, and reservoirs. The adopted framework allows complete flexibility with regard to the topological structure of a network and, as such, it provides an extremely useful general basis for modeling the frequency-domain behavior of pipe networks. Numerical examples are given for a 7- and 51-pipe network, demonstrating the utility of the method.     

Hydraulic Behavior of Filter Protected Silt under Cyclic Flow

The spatial distribution of hydraulic gradients within a soil sample under cyclic flow with different frequencies was measured and compared with calculated results. The permeability within the soil before and after cyclic flow was compared. This study shows that a lower ratio of consolidation coefficient of the soil to the angular velocity of cyclic flow will result in higher hydraulic gradients at the boundaries, and lower gradients within the soil. This study suggests that besides geometrical parameters of soil and geosynthetics, the consolidation coefficient of the soil and the frequency of cyclic flow need to be considered as well in the design of filters under cyclic flow.     

Transient Turbulent Flow in a Liquid-Metal Model of Continuous Casting,Including Comparison of Six Different Methods

Computational modeling is an important tool to understand and stabilize transient turbulent fluid flow in the continuous casting of steel to minimize defects. The current work combines the predictions of two steady Reynolds-averaged Navier–Stokes (RANS) models, a “filtered” unsteady RANS model, and two large eddy simulation (LES) models with ultrasonic Doppler velocimetry (UDV) measurements in a small-scale liquid GaInSn model of the continuous casting mold region fed by a bifurcated well-bottom nozzle with horizontal ports. Both mean and transient features of the turbulent flow are investigated. LES outperformed all models while matching the measurements, except in locations where measurement problems are suspected. The LES model also captured high-frequency fluctuations, which the measurements could not detect. Steady RANS models were the least accurate methods. Turbulent velocity variation frequencies and energies decreased with distance from the nozzle port regions. Proper orthogonal decomposition analysis, instantaneous velocity patterns, and Reynolds stresses reveal that velocity fluctuations and flow structures associated with the alternating-direction swirl in the nozzle bottom lead to a wobbling jet exiting the ports into the mold. These turbulent flow structures are responsible for patterns observed in both the time average flow and the statistics of their fluctuations.     

Effect of Centrifugal Speed in Abrasive Wear Behavior of Al-Si5Cu3/SiC Functionally Graded Composite Fabricated by Centrifugal Casting

Centrifugal casting was adopted for fabricating AlSi5Cu3/10 wt% SiC functionally graded metal matrix composite under three different centrifugal speeds of 800, 1000 and 1200 rpm, and hollow cylindrical components (φ_out 150 × φ_in 132 × 150 mm) were obtained. Microstructures of outer and inner periphery of all composites were observed through optical microscope and micro hardness of outer, intermediate and inner region of composite was tested using Vicker’s hardness tester. Results revealed that outer region of the composites centrifuged at all speeds have particle rich region with higher hardness. Abrasive wear experiments were conducted only on surface of particle rich region based on Taguchi’s technique by varying parameters such as centrifugal speed of casting process, rotating speed and applied load of abrasive wear tester. Analysis of variance results revealed that, centrifugal speed had highest significance on wear rate. Abraded surfaces were examined using scanning electron microscope and the maximum wear resistance was observed on particle rich zone of composite centrifuged at 1200 rpm.     

复杂网络无尺度特征及其演化机理研究

根据复杂网络演化的两个基本机理抽象出一种复杂网络演化的一般模型(GP Model),该模型具备增长和择优两个普遍特征,并根据连续动力学原理分析了该模型的平凡特征量.在平凡特征量的基础上,利用极大似然原理得出了该模型网络在经历长期演化后节点分布具有幂律特征这一结论,从概率理论上解释了这一类网络度分布特征的成因.此外,利用GP模型研究了互联网度分布的指数截断特征以及长期演化的节点度分布特征,并分析了互联网的长期演化态势和节点行为特征.     

Transient Behavior and Thermodynamics of Inclusions in Al-Ti-Deoxidized and Ca-Treated Steel

Metallurgical and Materials Transactions B - Ti-alloyed steels have severe nozzle clogging problems, which are detrimental to the steel production process. However, little research on the...     

Data Reconciliation on the Complex Hydraulic System of Canal de Provence

A data reconciliation module, based on the measurements from the hydraulic network, has been recently developed and implemented in the supervisory system of the Société du Canal de Provence (SCP). The software has initially been used daily to check the measured flow on the main canal. The data reconciliation occurs just after the measurement process. The measurement network on the hydraulic system includes many sensors subject to failure or deviation and is spread over a huge area. In addition, discharge and volume measurements in open-channel hydraulic networks are characterized by large uncertainties. The objective of the data reconciliation is to take advantage of information redundancy on a system to make a cross-check of real-time measurements. By using this information redundancy, a data reconciliation module allows detection of inconsistent measurements and measurement deviations and provides corrected values whether the initial measurements are valid, biased, or invalid. A derived consequence is better scheduling of the maintenance of sensors. The results are corrected values for measured variables and proposed values for nonmeasured quantities. A statistical analysis of the results is performed. This analysis allows evaluation of the uncertainties attached to the estimated flows and volume values. It allows also detecting invalid measurements and drift of sensors and making decisions about which maintenance operations to perform.     

Effects of Placement Method on Geotechnical Behavior of Hydraulic Fill Sands

Results of an investigation of the geotechnical behavior of a hydraulic sand placed at a land reclamation site in Hong Kong are presented and interpreted. The study was conducted to aid in developing guidelines for quality control of hydraulic landfill placement. The work described consisted of: (1) field investigations; (2) static and cyclic triaxial testing; and (3) calibration chamber tests to study the cone penetration test versus Dr relationships for marine sands obtained from the reclamation sites. The results of this study clearly indicate that the placement technique is the single most important factor controlling the geotechnical behavior of a given type of sand when placed as a hydraulic fill. The weakest zone is generally located just beneath the water level where fill deposition is placed by pipeline discharge.     

Online Measurement for Transient Mold Friction Based on the Hydraulic Oscillators of Continuous-Casting Mold

The interaction of the strand shell surface and mold copper plates has significant effects on the slab surface quality and casting productivity. This article focuses on developing a reliable approach to measure the transient friction force between the slab and the mold for the purpose of the investigation of lubrication and friction behavior inside a mold. This method is presented to monitor transient mold frictions for the slab continuous caster equipped with hydraulic oscillators. A mathematical model is also developed to calculate the empty working force of the no casting state, and a new algorithm, based on the particle swarm optimization, is proposed to predict the dynamic characteristic parameters of mold oscillation. The results have shown that the method has a sufficient sensitivity to variation, especially to the periodical variation of the mold friction, and it has been identified that the transient mold friction can be used as an effective index with regard to detecting mold oscillation and optimizing the casting parameters for process control. It may lay the practical foundation for the online detection of powder lubrication and the visualization of the continuous-casting mold process.