生物质颗粒燃烧特性的数值模拟及实验研究

Numerical simulation and experimental study on combustion characteristics of biomass particles

基于ICEM软件对燃烧室进行二维建模和结构化网格划分,并应用FLUENT软件对玉米秸秆、棉秆、木屑和稻秆4种生物质颗粒在燃烧室中进行燃烧仿真模拟,与煤粉燃烧进行对比。对比分析5种燃料燃烧时,燃烧室内不同位置中心截面的温度、O_(2)、CO_(2)和NO_(x)质量分数的变化曲线,同时分别对5种燃料做单独燃烧实验,结合对比分析结果将4种生物质颗粒分别和煤粉按照5.00%、10.00%、15.00%、20.00%的质量掺混比做混烧实验。研究结果表明,5种燃料中,煤粉在燃烧室中心截面上的温度最高,且最高温度比4种生物质颗粒高600 K以上,但生物质颗粒的温度分布均匀程度均优于煤粉;煤粉燃烧产生的NOx含量最高达到2.00%,而生物质颗粒产生的NOx含量基本为0.00%,且生物质颗粒的燃烧特性受一次风速、一次风温及自身含水率的影响较大;5种燃料燃烧时燃烧室最高温度的模拟值均高于实验值,但误差均小于20.0%,4种生物质颗粒与煤粉混合燃烧的质量掺混比不宜超过15.00%,当质量掺混比为15.00%时,燃烧室的最高温度比单独燃煤时降低150 K,但最大NOx质量分数能降低44%。

Based on ICEM software,two-dimensional modeling and structured grid division were carried out for the combustor.Fluent software was used to simulate the combustion of four kinds of biomass particles,including corn stalk,cotton stalk,wood chips and rice stalk,and the results are compared with pulverized coal combustion.The temperature change,mass fraction of O_(2),mass fraction of CO_(2) and mass fraction of NO_(x) at different positions in the combustion chamber were compared and analyzed for the five fuels combustion.At the same time,separate combustion experiments were carried out for five kinds of fuels and mixed combustion experiments were carried out for four kinds of biomass particles and pulverized coal with the mass mixing ratio of 5%,10%,15% and 20%.The results show that among the five fuels,pulverized coal has the highest temperature on the center section of the combustion chamber,and the highest temperature is more than 600 K higher than that of the four biomass particles,but the temperature distribution uniformity of biomass particles is better than that of pulverized coal.The maximum NO_(x) content of pulverized coal combustion reaches 2.00%,while the NOr content of biomass pellets is basically 0.00%.The combustion characteristics of biomass pellets are greatly affected by primary wind speed,primary air temperature and their own moisture content.The simulation values of the maximum temperaturein the combustion chamber are all higher than the experimental values,but the deviations are all less than 20.0%.The mass mixing ratio of the four biomass particles and pulverized coal should not exceed 15%.When the mass mixing ratio is 15%,the maximum temperature of the combustion chamber is 15o K lower than that when the coal is burned alone,but the maximum NO_(x),mass fraction can be reduced by 44%.