湍流热环境中毫米级木质生物质颗粒燃烧特性  

Combustion characteristics of millimeter-sized wood biomass particles in high-temperature turbulent environments

作　　者：郭慧娜 吴玉新[1] 冯乐乐 刘杰[2] GUO Huina;WU Yuxin;FENG Lele;LIU Jie(Department of Energy and Power Engineering,Tsinghua University,Beijing100084,China;School of Safety Engineering,China University of Mining and Technology,Xuzhou221116,China)

机构地区：[1]清华大学能源与动力工程系,北京100084 [2]中国矿业大学安全工程学院,江苏徐州221116

出　　处：《洁净煤技术》2024年第6期36-46,共11页Clean Coal Technology

基　　金：国家自然科学基金资助项目(51761125011);清华大学山西清洁能源研究院种子基金资助项目。

摘　　要：燃煤机组耦合生物质甚至全燃生物质是高效低成本降碳的可行技术。生物质燃料破碎能耗高导致入炉粒径相对较大,部分大粒径颗粒在炉内高温湍流环境中的燃尽问题值得重视。采用四风扇对冲高温湍流实验装置,构造近均匀各向同性湍流流场。以两种粒径的木质生物质颗粒(d_(p,0)=2.5、6.0 mm)为研究对象,通过改变炉温(T_(gas)=500、700、900℃)和湍流脉动速度(u_(rms)=0~1.8 m/s),研究湍流脉动速度urms对毫米级生物质颗粒燃烧特性的影响。试验通过颗粒表面-中心温度测量系统记录了颗粒温度,通过彩色图像测量系统捕捉燃烧全过程,确定不同工况下生物质颗粒的燃烧时间、着火模式、火焰形态及粒径变化。结果表明,生物质颗粒通常倾向于发生均相着火,仅在T_(gas)=500℃时增大u_(rms)使着火模式由均相着火转变为异相着火。u_(rms)增至1.8 m/s,着火前颗粒升温速率提高了近30%,挥发分燃烧阶段颗粒表面温度升高约300℃。u_(rms)增加引起挥发分火焰锋面褶皱变形,均相燃烧强度增加,tvol略微缩短;生物质焦炭的孔隙发展更加迅速,大量氧气扩散进颗粒内发生反应,使焦炭燃尽时间大幅缩短40%以上,焦炭燃烧温度亦随之增加。颗粒湍流雷诺数Re_(p,t)越大,受湍流脉动影响越显著。升高炉温,增大u_(rms)对颗粒温度的影响将减弱,对缩短燃烧时间的影响越强烈。Biomass co-firing in coal-fired power plants represents a viable technology for efficient and low-cost CO_(2)reduction.The high energy consumption for crushing biomass fuel results in relatively large particle sizes entering the furnace.The burnout of these large parti-cles in the high-temperature turbulent environment within the furnace is a matter of concern.A four-fan opposed high-temperature turbu-lent experimental apparatus was employed to create a nearly homogeneous and isotropic turbulent flow field.Woody biomass particles of two sizes(d_(p,0)=2.5 and 6.0 mm)were used as the research subjects,the effect of turbulent fluctuation velocity urms on the combustion charac-teristics of millimeter-sized biomass particles were examined by varying the furnace temperature(T_(gas)=500,700,900℃)and turbulent fluctuation velocity(u_(rms)=0-1.8 m/s).The particle temperature using a particle surface-center temperature measurement system was used and the entire combustion process using a color image capture system was captured.The biomass particle′s combustion time,ignition mode,flame shape,and particle size change under different conditions could be determined.The results indicate that biomass par-ticles tend to undergo homogeneous ignition,with the mode of ignition shifting to heterogeneous only at T_(gas)=500℃when u_(rms) increases.The particle heating rate before ignition rises by nearly 30%,and the particle surface temperature during the volatile combustion stage in-creases by approximately 300℃,when u_(rms) increases to 1.8 m/s.The increase in u_(rms) causes the volatile flame front to wrinkle and de-form,intensifying homogeneous combustion and slightly shortening the volatile combustion time.The porosity development of biomass char becomes more rapid,allowing a large amount of oxygen diffuse into the particles and react with carbon matrix,significantly shortening the char burnout time by over 40%and increasing the char combustion temperature.The larger the particle turbulent Reynolds number,the more signific

关 键 词：均匀各向同性湍流 生物质能源 单颗粒燃烧 湍流热环境 

分 类 号：TK6[动力工程及工程热物理—生物能]