A New Distribution Method for Wet Steam Injection Optimization

A new approach and a new related distribution system are proposed to address the issue of uneven steam injection caused by the different suction capacities of the used wells during the application of steam“stimulation”methods for enhanced oil recovery.The new distribution system consists of a swirler,spiral dividing baffles,and critical flow nozzles.Numerical simulations are used to analyze the flow-field and degree of steam homogeneity obtained with such an approach.The results indicate that a higher inlet pressure leads to better results.Additionally,the internal flow field becomes more stable,and the deviation from an even distribution reduces to±4.0%even when the resistance of each branch is inconsistent.Furthermore,field tests have yielded satisfactory results.

NUMERICAL SIMULATION OF WET STEAM CONDENSING FLOW WITH AN EULERIAN/EULERIAN MODEL

Wet steam condensing flow in low-pressure steam turbine leads to efficiency losses and blade erosions.In order to investigate this problem by numerical approach, an Eulerian/Eulerian model has been developed, in which the wet steam is regarded as mixture comprising two coupled systems: the vapor phase and the liquid phase.These two systems are both described by conservation equations.High resolution TVD scheme is employed to capture condensing phenomena in wet steam flow.This model has been validated by numerical simulations of condensing flows in 1D and 2D nozzles.Compared with experimental data, a good agreement is observed.This Eulerian/Eulerian model can be extended to 3D calculation of condensing flow.

2D-simulation of wet steam flow in a steam turbine with spontaneous condensation

Removal of condensates from wet steam flow in the last stages of steam turbines significantly promotes stage efficiency and prevents erosion of rotors. In this paper, homogeneous spontaneous condensation in transonic steam flow in the 2-D rotor-tip section of a stage turbine is investigated. Calculated results agree with experimental data reasonably well. On the basis of the above work, a 2-D numerical simulation of wet steam flow in adjacent root sections of a complex steam turbine stage was carried out. Computational results were analyzed and provide insights into effective removal of humidity.

CFD analysis of a CiADS fuel assembly during the steam generator tube rupture accident based on the LBEsteamEulerFoam

Steam generator tube rupture(SGTR) accident is an important scenario needed to be considered in the safety analysis of lead-based fast reactors. When the steam generator tube breaks close to the main pump, water vapor will enter the reactor core, resulting in a two-phase flow of heavy liquid metal and water vapor in fuel assemblies. The thermal-hydraulic problems caused by the SGTR accident may seriously threaten reactor core's safety performance. In this paper, the open-source CFD calculation software OpenFOAM was used to encapsulate the improved Euler method into the self-developed solver LBEsteamEulerFoam. By changing different heating boundary conditions and inlet coolant types, the two-phase flow in the fuel assembly with different inlet gas content was simulated under various accident conditions. The calculation results show that the water vapor may accumulate in edge and corner channels. With the increase in inlet water vapor content, outlet coolant velocity increases gradually. When the inlet water vapor content is more than 15%, the outlet coolant temperature rises sharply with strong temperature fluctuation. When the inlet water vapor content is in the range of 5–20%, the upper part of the fuel assembly will gradually accumulate to form large bubbles. Compared with the VOF method, Euler method has higher computational efficiency. However, Euler method may cause an underestimation of the void fraction, so it still needs to be calibrated with future experimental data of the two-phase flow in fuel assembly.

Calculating densities and viscosities of natural gas with a high content of C_(2+) to predict two-phase liquid-gas flow pattern

The paper is devoted to the two-phase flow simulation.The gas-condensate mixture flow in a horizontal pipe under high pressure is considered.The influence of the equation of state(EOS)choice for mixture properties modelling on the flow regime calculation results is studied for gas with high content of methane homologues.An analytical overview of the methods to predict the flow pattern is provided.Based on this analysis,two techniques are selected.For these techniques,values of density and viscosity for each phase are required.Density calculation for the gas phase is performed with Van der Waals based EOS.The propriate EOS is selected based on studies of calculation errors for test mixtures.Calculation of liquid phase density is done by means of Patela-Teja and Guo-Du equations,two different models are considered for viscosity estimation.The flow patterns of gas-condensate mixture in a range of temperatures and pressures are calculated and verified via probability map.The results of study allow to recommend the Brusilovsky EOS for calculation of densities for similar gas mixtures and make more rigorous flow regime evaluation.The probability map shows that for the chosen composition and parameters of media the flow pattern is mostly transitional between segregated and annular independent from EOS.

Experimental study on prediction model of wet gas pressure drop across single-orifice plate in horizontal pipes in the low gas phase Froude number region

The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates.However,this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow,which is corresponding to a region of low FrG(gas phase Froude number)in the flow pattern map of wet gases.In this study,the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low FrG region.By the experiment,the flow pattern transition in the downstream of single-orifice plates,as well as the effects of FrG and FrL(liquid phase Froude number)on UG(gas phase multiplier),were determined and compared when the upstream is in the flow pattern transition and the stratified flow region,respectively.Prediction performances were examined on the available pressure drop models.It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low FrG region with an acceptable accuracy.With a new method of correlating FrG and FrL simultaneously,new correlations were proposed for the low FrG region.Among which the modified Chisholm model shows the best prediction accuracies,with the prediction deviations of UG being within 7%and 3%when the upstream is in flow pattern transition and stratified flow region,respectively.

Improvement of Heating Method for Measuring the Wetness of Flowing Wet Steam

In this paper, an improvement of heating method for measuring wetness of the flowing wet steam is developed, the basic principle of the heating method is presented and the mathematical model has been built for analyzing the thermodynamics problezns during the process of heating. Moreover, an instru-ment for measuring wetness of wet steam flow was designed and made out. This instrument has been used for measuring wetness of the wet steam flow at the outlet of the nozzle rig in Thermal TUrbine Laboratory Xi’an Jiaotong University. By analyzing the relative error of the result, it was found that this instrument has fairly high accuracy it can be used as the prototype of practical instrument and has an important applicable value in engineering.

透平叶轮内湿蒸汽凝结水滴流动的三维数值模拟

以水蒸汽为介质的透平膨胀机,其内部流场可能会出现湿蒸汽凝结现象,形成的水滴将进一步导致叶片损伤和机组效率降低。因此,研究透平叶轮内湿蒸汽凝结水滴的流动,对于评估叶片侵蚀损伤和气动设计,具有重要意义。本文在Euler-Lagrange两相流动模型的基础上,开发水滴示踪程序,用以捕捉三维流场中凝结水滴的运动轨迹。计算结果表明,该程序能较好地追踪水滴的运动及碰撞信息。

Research on Wet Steam Spontaneous Condensing Flows Considering Phase Transition and Slip

A new dual-fluid model considering phase transition and velocity slip was proposed in this paper and the Cunningham correction was used in the droplet resistance calculation. This dual-fluid model was applied to the numerical simulations of wet steam flow in a 2D LAVAL nozzle and in the White cascade respectively. The results of two simulations demonstrate that the model is reliable. Meanwhile, the spontaneous condensing flow in White cascade was analyzed and it infers that the irreversible loss caused by condensation accounts for the largest share (about 8.78% of inlet total pressure) in total pressure loss while the loss caused by velocity slip takes the smallest share (nearly 0.42%), and another part of total pressure loss caused by pneumatic factors contributes a less share than condensation, i.e. almost 3.95% of inlet total pressure.

Correction of Non-Isokinetic Sampling of Wetness Measurement for Wet Steam Flow

A mathematical model for predicting the behavior of wet steam flow in the vicinity of the intake head of the sampling probe is presented. The vapor flow field and droplet trajectory in the calculated region have been obtained. The errors caused by non-isokinetic sampling for different conditions have been analyzed and the analytical results would provide useful data for the design and application of a heating method-based wetness measurement probe in practice.

Numerical Investigation on Wet Steam Non-equilibrium Condensation Flow in Turbine Cascade

Based on the two-phase wet steam flow with spontaneous condensation,experimental verification and flow analysis on nozzle and 2D cascade are carried out.The 3D Reynolds-Averaged gas-liquid two-phase flow control equation solver is explored with k ε k p turbulence model.Furthermore,3D flow numerical simulation on the last stage stator of the steam turbine is carried out.The results show that a sudden pressure rise on blade suction surface is mainly caused by the droplet growth in condensation flow.The more backward the condensation position is in cascade passage,the less the sudden pressure rise from condensation is,and the larger the nucleation rate is,the maximum under-cooling and the number of droplets per unit volume are.Interaction of condensation wave and shock wave has imposed greater influence on the parameters of the blade cascade outlet.

Losses Estimation in Transonic Wet Steam Flow through Linear Blade Cascade

Experimental investigations of non-equilibrium spontaneous condensation in transonic steam flow were carried out in linear blade cascade. The linear cascade consists of the stator blades of the last stage of low pressure steam turbine. The applied experimental test section is a part of a small scale steam power plant located at Silesian University of Technology in Gliwice. The steam parameters at the test section inlet correspond to the real conditions in low pressure part of 200 MWe steam turbine. The losses in the cascade were estimated using measured static pressure and temperature behind the cascade and the total parameters at inlet. The static pressure measurements on the blade surface as well as the Schlieren pictures were used to assess the flow field in linear cascade of steam turbine stator blades.

一种基于布拉格光纤光栅测量湿蒸汽两相流湿度场的新方法

在论述 Bragg 光纤光栅传感测试技术独特性能的基础上,提出了一种基于 Bragg 光纤光栅传感技术测量湿蒸汽两相流湿度场的新方法。重点对光纤光栅测量湿蒸汽两相流湿度场以及温度场的机理进行研究,对实验系统装置的构建作了详尽的描述。讨论光纤光栅的湿增敏机理、湿敏材料的选择和涂覆方法,并对测量的影响因素和误差进行分析。该测试新方法将能解决湿蒸汽两相流中湿度的动态、准分布测量的技术难题。

布拉格光纤光栅测量湿蒸汽两相流温/湿度的理论数学模型

基于布拉格(Bragg)光纤光删(FBG)测量湿蒸汽两相流温度和湿度的物理模型,推导测量湿蒸汽两相流温度和湿度的数学模型,设计了新颖的测量结构和实验系统,并进行了分析。在同一光纤两段区域上写入不同中心反射波长的FBG,在一处FBG外面涂覆了湿敏材料(如PI材料),增强其感湿能力,把湿敏材料吸湿后发生湿膨胀引起的膨胀量当作产生湿应变来处理,同时还引入了湿敏材料与FBG的界面粘接系数,得出由于温度和湿度变化湿敏材料产生的应变使FBG波长发生漂移;把另一处FBG封装在温敏材料(如铝材料)中,只感受温度的响应,通过热应变对FBG作用,波长发生漂移,从而推导出测量的理论数学模型。

一种新型的测量汽轮机内湿蒸汽两相流的集成化探针系统

汽轮机内湿蒸汽两相流中一次、二次水滴的参数和流场是密切相关的，但国内外迄今没有能同时测量这些参数的技术和设备。作者成功研制了能同时测量湿蒸汽两相流中一次、二次水滴和流场的集成化探针。该探针已在３５０ＭＷ汽轮机上进行了实测。本文介绍了该测量系统的原理和构成。

一维喷管中存在自发凝结的跨音速湿蒸汽两相流动数值模拟

本文结合液滴成核、生长理论及Ｅｕｌｅｒ方程组，在无滑移假设下，导出了描述存在自发凝结的湿蒸汽两相流动控制方程组。对汽液两相流动控制方程组采用ＴＶＤ格式离散、时间推进法求解。对准一维喷管中的湿蒸汽两相流动进行了数值模拟，得到了满意的计算结果。

湿蒸汽两相凝结流动中水滴生长模型研究

为了准确描述湿蒸汽两相流中水滴生长过程,以提高数值模拟的精度和可信度,基于传热传质平衡耦合求解方法提出一种水滴生长模型。将建立的模型与目前湿蒸汽两相流计算中广泛使用的几种水滴生长模型进行了对比分析,结果显示在整个克努森数Kn变化范围内,该模型表现良好,明显优于其他模型,特别是在过渡区内具有很高的精确性。同时为了揭示不同水滴生长模型对两相参数的影响,采用各水滴生长模型对一维拉瓦尔Laval喷管中存在的自发凝结的湿蒸汽流动进行数值模拟。结果表明,不同水滴生长率模型对液相成核率、水滴数、水滴半径的影响非常明显,但对蒸汽湿度影响较小。

汽轮机内湿蒸汽两相流流场的实验研究

凝汽式汽轮机末几级往往工作于湿蒸汽区 ,工作条件恶劣。作者研制了能同时测量汽液两相流动状况的集成化探针 ,并成功地在电厂进行了实测。实验结果表明 :汽轮机中湿蒸汽的流动特性沿叶高是不均匀的 ,湿蒸汽中二次水滴的流动速度和方向与主汽流都有很大差别。讨论了湿蒸汽流场的测量方法并对部分实验结果进行了分析。图 1 0参

膨胀率对湿蒸汽自发凝结流动影响的数值分析

结合液滴成核、生长理论,在无滑移假设下,导出了描述存在自发凝结湿蒸汽两相流动的方程组,对喷管中的湿蒸汽自发凝结不平衡稳定两相流动进行了数值模拟,得到了沿喷管轴向蒸汽两相参数的分布。分析了相同进口蒸汽参数和喷管形状下,膨胀率对蒸汽压力、过冷度、水滴半径、蒸汽湿度沿轴向分布和成核率大小的影响。汽轮机内湿汽损失的大小与蒸汽过冷度、水滴半径、湿度大小和由于凝结产生的“压力冲波”剧烈程度等因素有关,膨胀率是影响这些因素的主要参数。通过选择合适的膨胀率,对通流部分进行优化设计,控制蒸汽凝结的成核过程,可以预期减小级的湿汽损失。

汽轮机湿蒸汽两相流中水滴尺寸研究进展

综述了国内外湿蒸汽两相流的理论和实验研究进展,分析了目前湿蒸汽中水滴尺寸研究的状况和遇到的困难,并详细介绍了能同时测量一次水滴和二次水滴的集成化探针,给出了在电厂350 MW汽轮机上的测量结果.