油浸式变压器油流速与温度场关联性建模

变压器瓦斯继电器油流速的大小直接决定瓦斯保护是否动作,从油流速的角度分析瓦斯保护具有重要意义。依据变压器运行时的产热、散热机理,基于ANSYS仿真软件和有限元数值计算方法,建立变压器三维暂态温度场模型,计算出变压器内部稳态和故障时的温度场分布,定量反映故障前后变压器内部温度的变化情况,在此基础上,推导出油膨胀和油裂解产气对油流速的影响,建立变压器油流速与暂态温度场关联性数学模型。以某油浸式变压器为对象进行三维温度场仿真分析,分析油流速对变压器温度场的影响,仿真结果验证了模型的正确性,为变压器气体继电器设置整定值提供良好的参考。

码头收发油流速问题探讨

广东省石油企业集团公司所属黄埔油库,总容量26万m^3,拥有2.5万吨级和0.5万吨级油码头各1座,收发油作业以港口接卸为主,汽车、铁路发油为辅。 原有的码头操作规程规定“……用输油胶管卸油,压力不超过0.3MPa,卸油时最高流速不得超过4m/s。”受规定的限制,码头收卸油料在工作压力0.3MPa,流速约4m/s时,收卸柴油约445t/h,汽油约330t/h,一艘2.5万吨级油轮卸油时间需要60h左右。

变压器重瓦斯油流速监测与温度关联技术研究

本文集中分析了超声波时差法、声波多普勒、激光多普勒三种油流速的测量方法。根据变压器运行时油温特点,从油热解产气和膨胀产气的角度建立对应的温度产气模型,并以此为基础分别推导油流速与温度的函数关系,得到变压器重瓦斯油流速与温度的关联模型。对一35kV油浸式变压器加装测量传感器实现温度、油流速的监测。以此变压器为对象,根据本文建立的油流速与温度关联模型进行ANASYS仿真,测试与仿真结果对比分析了三种测量方法的优缺点,可为进一步研究设计变压器非电量保护监测系统提供参考。

利用过程模拟技术优化焦化加热炉操作

从炉管结焦机理及控制结焦速度的角度出发 ,提出利用过程模拟技术优化加热炉操作 。

有载分接开关瓦斯继电器动作特性试验研究

近年来,在工程现场中出现过多起正常切换导致有载分接开关瓦斯保护误动的事件,而其误动基理尚不明确。为了探究其误动原因,搭建了基于2XCMDI-1000/126C-10193W型有载分接开关的瓦斯继电器动作特性研究实验平台,并通过空气压缩机注压的方式在油箱内部模拟不同的工况,对不同种类的瓦斯继电器在各种压强、油流速环境下的动作特性进行了大量实验。实验结果表明:随着压力源压力值增大,有载分接开关所用挡板式瓦斯继电器动作时刻对应的油流速有逐渐减小的趋势,而油流加速度则逐渐增大。分析认为,瓦斯继电器中挡板动作是油流速对应的“动压力”与绝缘油液体中“静压力”共同作用的结果。文中研究结果解释了在油流速未达到整定值的情况下有载分接开关的瓦斯保护发生误动的原因,为有载分接开关瓦斯继电器整定值的设置以及校验提供了一定的理论及实验基础。

Ultrasonic method for measuring water holdup of low velocity and high-water-cut oil-water two-phase flow

Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with severely non-uniform local-velocity flow profiles and dispersed-phase concentration（of oil droplets） in oil-water two-phase flow,which makes it difficult to measure water holdup in oil wells.In this study,we use an ultrasonic method based on a transmission-type sensor in oil-water two-phase flow to measure water holdup in lowvelocity and high water-cut conditions.First,we optimize the excitation frequency of the ultrasonic sensor by calculating the sensitivity of the ultrasonic field using the finite element method for multiphysics coupling.Then we calculate the change trend of sound pressure level attenuation ratio with the increase in oil holdup to verify the feasibility of the employed diameter for the ultrasonic sensor.Based on the results,we then investigate the effects of oildroplet diameter and distribution on the ultrasonic field.To further understand the measurement characteristics of the ultrasonic sensor,we perform a flow loop test on vertical upward oilwater two-phase flow and measure the responses of the optimized ultrasonic sensor.The results show that the ultrasonic sensor yields poor resolution for a dispersed oil slug in water flow（D OS/W flow）,but the resolution is favorable for dispersed oil in water flow（D O/W flow） and very fine dispersed oil in water flow（VFD O/W flow）.This research demonstrates the potential application of a pulsed-transmission ultrasonic method for measuring the fraction of individual components in oil-water two-phase flow with a low mixture velocity and high water cut.

Laser Measurement and Intensity Evaluation of Intake Swirl in Engine Using a Water Analog

The intake swirl in the cylinder was induced by a swirler which was fixed in one of two intake ports. In order to understand the characteristics of the intake swirl, a transparent water analog was designed which simulated 150 type single cylinder engine. At the same time, the particle image velocimetry was used to measure the flow fields induced by various swirlers in the analog. After measurement, a new method was presented to evaluate the intensity of the intake swirl. Then, when the measured sections, the lifts of valve and the swirlers were different, the calculated results of the flow field were compared.

散热器组抬高对变压器温升的影响

为了分析散热器组抬高对变压器温升的影响,在传统温升计算的基础上,利用有限元法对油流速度进行计算,从理论上解析了油流速对散热性能的影响。同时结合相关的温升试验数据,针对散热器组架高的情况,给出了传统温升计算结合油流速分析温升计算方法。

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.

Failure in Fuel Injector Nozzles Used in Diesel Engines

This paper aims to conduct a study of the problems associated with the wear of the needles and fuel injection nozzles utilized in diesel engines. The wear found on the needles is mainly associated to impurities in the fuel oil and microcavitation occurred due to high pressure in the phase of the air compression for combustion of the combustible fluid. These pressures associated with the temperature and the fluid velocity results in the occurrence of vaporization, which releases shock waves that cause damage to the affected surface. The impurities solid particles from the fuel oil cause problems inside the nozzles as obstruction of the holes and wear on the needle tip and nozzle seat surface. These failures affect in the atomization of the fuel, since the deterioration of the internal passages of the nozzles interferes in the spray formation and in the end passage of the fluid. For the execution of this study it will be used digital microscopic analysis in specimens that suffered damage, in order to investigate the effects of fuel property, and the temperature conditions and pressure in the formation of the wear on the needles and injector nozzle.

Heat transfer and friction factor of Therminol liquid phase heat transfer fluid in a ribbed tube

Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm,pitch and rib height of 4.5 and 1.0 mm.respectively.Experimental results show that the heat transfer and thermal performance of Therminol-55 liquid phase heat transfer fluid in the ribbed tube are considerably improved compared to those of the smooth tube.The Nusselt number increase with the increase of Reynolds number.The increase in heat transfer rate of the ribbed tube has a mean value of 2.24 times.Also,the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.4 and 2.8 times over the smooth tube.Numerical simulations of three-dimensional flow behavior of Therminol-55 liquid phase heat transfer fluid are carried out using three different turbulence models in the ribbed tube.The numerical results show that the heat transfer of ribbed tube is improved because vortices are generated behind ribs,which produce some disruptions to fluid flow and enhance heat transfer compared with smooth tube.The numerical results prove that the ribbed tube can improve heat transfer and fluid flow performances of Therminol liquid phase heat transfer fluid.

Effects of the injector geometry on a sonic jet into a supersonic crossflow

Large-eddy simulation of a sonic injection from circular and elliptic injectors into a supersonic crossflow has been performed.The effects of injector geometry on various fundamental mechanisms dictating the intricate flow phenomena including shock/jet interaction,jet shear layer vortices and their evolution,jet penetration properties and the relevant turbulence behaviors have been studied systematically.As a jet issuing transversely into a supersonic crossflow,salient three-dimensional shock and vortical structures,such as bow,separation and barrel shocks,Mach disk,horseshoe vortex,jet shear layer vortices and vortex pairs,are induced.The shock structures exhibit considerable deformations in the circular injection,while their fluctuation becomes smaller in the elliptic injection.The jet shear layer vortices are generated at the jet periphery and their evolution characteristics are analyzed through tracing the centroid of these coherent structures.It is found that the jet from the elliptic injector spreads rapidly in the spanwise direction but suffers a reduction in the transverse penetration compared to the circular injection case.The turbulent fluctuations are amplified because of the jet/crossflow interaction.The vertical Reynolds normal stress is enhanced in the downstream of the jet because of the upwash velocity induced by the counter-rotating vortex pair.

Supersonic Cavity Based Combustion with Kerosene/Hydrogen Fuel

A comparative study with kerosene and hydrogen fuel in a model scramjet combustor has been carried out nu- merically. The effect of fuel-air equivalence ratio on the flow field properties in a cavity based mixing mechanism at a freestream Math number of 2.08 has been probed. The investigation has been carried out in a two dimension- al numerical model where a cavity of length to depth ratio of 2 is mounted on one of the walls of the flow channel The flow field shock structure is observed to change with the change in fuel-air equivalence ratio. Total pressure loss is observed to depend both on fuel air equivalence ratio and the fuel type. The spread of fuel in the test sec- tion shows marked variation with the equivalence ratio. Performance of injector location on the fuel-air mixing is also probed during the course of the investigation.