洁净煤技术

2020, v.26;No.126(02) 58-65

[打印本页] [关闭]
本期目录(Current Issue) | 过刊浏览(Past Issue) | 高级检索(Advanced Search)

风粉混合器内气固两相流动的模拟及试验研究
Simulation and experimental study of gas-solid two-phase flow in the air-powder mixer

张朝;崔豫泓;刘羽;王鹏涛;
ZHANG Chao;CUI Yuhong;LIU Yu;WANG Pengtao;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

摘要(Abstract):

煤粉工业锅炉系统中风粉混合器是实现煤粉与一次风快速均匀混合的关键设备,测量及计算风粉混合器内煤粉、一次风气固两相流流场,对于优化风粉混合器结构,强化风粉混合效率及提高一次风粉的均匀稳定供给具有重要意义。笔者针对竖直结构及倾斜结构的2种风粉混合器,开展了数值计算及现场工程试验研究。基于几何拓扑学知识,采用ICEM软件针对2种风粉混合器划分了合适的三维网格;多相流理论模型中,多相连续介质模型中的双流体模型各相视为相互渗透、耦合但又保持各自运动特征的连续介质,相比于单流体模型,双流体模型考虑了固相的湍流输运以及气固两相间相互滑移引起的阻力,使得计算结果更接近实际情况;冷态双流体模型基本方程由守恒方程、相间耦合方程以及封闭方程构成,其中相间耦合方程用于表征气固相动量之间的耦合;为了探究不同停留时间下风粉混合器内气固两相的流场特征,采用非稳态数值计算方法,利用Fluent软件开展数值计算。基于两相流模型及Schilller-Naumann曵力系数模型研究了不同结构下风粉混合器内煤粉浓度分布随停留时间变化特征,采用德图testo425热敏风速仪测量了不同煤粉落料量下风粉混合器内负压变化规律。结果表明,竖直结构的风粉混合器内停留时间由0.25 s增至1 s时,混合器底部颗粒沉积的现象一直存在,即存在较长时间的颗粒流动死角区域;而对于倾斜结构的风粉混合器,当停留时间大于0.3 s,混合器内颗粒浓度基本降为0,较好避免了颗粒在混合器底部的沉积,该结构对于强化混合器内风粉混合及降低供料波动具有重要意义。不同落料量下的现场工程试验结果表明,高落料量下竖直结构的风粉混合器内平均负压偏小,几乎接近正压,且存在间断正压喷粉的现象,故该风粉混合器在高落料量下负压不足,易造成供料波动较大;高落料量下倾斜风粉混合器负压平均值仍大于-1 000 Pa,且无喷粉现象。相比于竖直结构,倾斜风粉混合器具有稳定且较宽的负压变化范围,能较好地克服供料波动大的现象。
In the pulverized coal industrial boiler system,the mixer is the key equipment to realize the rapid and uniform mixing of pulverized coal and primary air.The measurement and calculation of the flow field of pulverized coal and primary air-solid two-phase flow in the air-powder mixer is of great significance to optimize the structure of the mixer,strengthen the mixing efficiency and improve the uniform and stable supply of pulverized coal.In this paper,numerical calculation and field engineering test were carried out for two kinds of air powder mixers with vertical structure and inclined structure.Based on the knowledge of geometry and topology,ICEM software was used to divide appropriate three-dimensional grids for two kinds of mixers. In the theoretical model of multiphase flow,each phase of the two fluid model in the multiphase continuum model is regarded as a continuum with mutual penetration,coupling but maintaining its own motion characteristics.Compared with the single fluid model,the two fluid model takes into account the turbulent transport of solid phase and the resistance caused by the sliding of gas-solid phases,which makes the calculation result more close to the actual situation. The basic equations of cold two fluid model are composed of conservation equation,inter phase coupling equation and closed equation,in which the inter phase coupling equation is used to represent the coupling between gas and solid momentum.In order to explore the flow field characteristics of gas-solid two phases in the mixer under different residence time,the unsteady model was adopted. In this paper,the numerical calculation and engineering test were carried out for two kinds of mixers.Based on the two-flow model of Fluent software and Schiller Naumann force coefficient model,the time-varying characteristics of the pulverized coal concentration distribution in the mixer with two different structures were studied.The negative pressure variation law in the mixer with different pulverized coal dropping amount was measured by using the testo 425 thermal anemometer.The results show that when the residence time in the vertical structure of the mixer increases from 0.25 s to 1 s,the phenomenon of particle deposition at the bottom of the mixer always exists,that is to say,there is a long dead angle area of particle flow,and for the inclined structure of the air-powder mixer,when the residence time is greater than 0.3 s,the particle concentration in the mixer basically drops to zero,which better avoids particles at the bottom of the mixer.This structure is of great significance to strengthen the mixing of pulverized coal and reduce the fluctuation of feed.The results of engineering tests under different blanking amount show that when the feed quantity is large,the average negative pressure in the vertical structure of the mixer is small,almost close to the positive pressure,and there is a phenomenon of intermittent positive pressure powder spraying,so the negative pressure of the air-powder mixer under high blanking amount is insufficient,which is easy to cause large feed fluctuation.However,the average negative pressure of the inclined mixer is still greater than-1 000 Pa,and there is no phenomenon of powder spraying.Compared with the vertical structure,the inclined mixer has a stable and wide range of negative pressure changes,which can better overcome the phenomenon of large feed fluctuation.

关键词(KeyWords): 多相流模型;两相流;风粉混合器;数值计算
multiphase-flow model;two-phase flow;air-powder mixer;numerical calculation

Abstract:

Keywords:

基金项目(Foundation): 煤炭科学技术研究院科技发展基金项目技术创新项目(2018CX02)

作者(Author): 张朝;崔豫泓;刘羽;王鹏涛;
ZHANG Chao;CUI Yuhong;LIU Yu;WANG Pengtao;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

Email:

DOI: 10.13226/j.issn.1006-6772.20011903

参考文献(References):

文章评论(Comment):

序号(No.) 时间(Time) 反馈人(User) 邮箱(Email) 标题(Title) 内容(Content)
反馈人(User) 邮箱地址(Email)
反馈标题(Title)
反馈内容(Content)
扩展功能
本文信息
服务与反馈
本文关键词相关文章
本文作者相关文章
中国知网
分享