自然循环锅炉深度调峰时水冷壁汽水两相流动不稳定特性计算及安全分析  

Calculation and safety analysis of unstable characteristics of vapor-liquid twophase flow in water wall during deep peak shaving of natural circulation boiler

作　　者：王志勇 李维腾 堵根旺 马玉华 周科[3] 杨冬[2] WANG Zhiyong;LI Weiteng;DU Genwang;MA Yuhua;ZHOU Ke;YANG Dong(Dandong Power Plant,Huaneng Power International Co.,Ltd.,Donggang 118300,China;State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China;Xi’an Thermal power Research Institute Co.,Ltd.,Xi’an 710054,China)

机构地区：[1]华能国际电力股份有限公司丹东电厂,辽宁东港118300 [2]西安交通大学动力工程多相流国家重点实验室,陕西西安710049 [3]西安热工研究院有限公司,陕西西安710054

出　　处：《热力发电》2024年第11期119-129,共11页Thermal Power Generation

基　　金：中国华能集团有限公司总部科技项目(HNK22-H103)。

摘　　要：为对深度调峰时对冲燃烧自然循环锅炉水冷壁管道内的汽液两相流动不稳定特性进行研究,建立了适用于不同工况的频域法数学模型。通过对质量、能量、动量方程进行小扰动线性化,消去高阶无穷小扰动量以及稳态量后经拉普拉斯变换得到了用于描述管道内汽液流体流动稳定性传递函数,通过Nyquist曲线图解的方法判断管内工质流动的稳定性。计算结果表明典型回路在25%BMCR和50%BMCR工况运行时的临界热流密度分别为182.20、240.13k W/m^(2)。同时,利用该模型计算了某350MW自然循环锅炉水冷壁管段的不稳定边界并研究了入口过冷度、质量流速、管长、倾斜角度以及入口节流系数等参数对流动不稳定特性的影响。计算结果表明:入口过冷度对临界热流密度的影响呈非单值性,不稳定边界图表现为“双C”型;增大质量流速使流体的进口和出口密度差减小,有利于流动的稳定;增大热流密度使流体的进口和出口密度差增大,不利于流动的稳定;增大入口节流系数,可以抑制入口处流量的脉动,有利于流动的稳定;增加管道的倾斜角度,会增大重位压降,使其产生的扰动增加,不利于流动的稳定。In order to study the unstable characteristics of vapor-liquid two-phase flow in water-cooled wall pipe of an opposed combustion natural circulation boiler during deep peak shaving,a frequency domain mathematical model suitable for different working conditions is established.By performing small perturbation linearization on the mass,energy,and momentum equations,eliminating high-order infinitesimal perturbations and steady-state quantities,and conducting Laplace transformation,the transfer function used to describe stability of the vapor-liquid fluid flow in the pipeline is obtained through the Nyquist diagram.The graphical method is used to judge the stability of the working fluid flow in the pipe.The calculation results show that,the critical heat flux densities of typical circuits operating at 25%BMCR and 50%BMCR are 182.20 kW/m^(2) and 240.13 kW/m^(2).Moreover,this model is used to calculate the unstable boundary of the water wall pipe section of a 350 MW natural circulation boiler and study the influence of parameters such as inlet subcooling,mass flow rate,pipe length,inclination angle and inlet throttling coefficient on the flow instability characteristics.The calculation results show that,the influence of inlet subcooling on critical heat flux density is non-unique,and the unstable boundary diagram shows a“double-C”shape.Increasing the mass flow rate reduces the density difference between the inlet and outlet of the fluid,which is beneficial to the flow stability.Increasing the heat flow density increases the density difference between the inlet and outlet of the fluid,which is not conducive to the stability of the flow.Enhancing the inlet throttling coefficient can suppress the pulsation of the flow at the inlet,which is conducive to the stability of the flow.Increasing the inclination angle of the pipe will increase the weight pressure drop and increase the disturbance caused by it,which is not conducive to the stability of the flow.

关 键 词：自然循环锅炉 流动不稳定性 频域法 Nyquist图 

分 类 号：TM621.2[电气工程—电力系统及自动化]