多孔金属板燃气灶燃烧性能数值模拟

Numerical Simulation of Combustion Performance of Gas Cooking Appliance with Porous Metal Plate

应用FLUENT软件对影响多孔金属板燃气灶燃烧性能的多个参数进行了控制变量的数值模拟,对各参数进行归一化处理与敏感性分析,探讨各参数对灶具燃烧性能的影响。简化模拟计算,取多孔金属板上的一个单火孔的一半作为数值模拟对象并划分网格进行模拟。得出以下结论:火焰中心位置随板面表面发射率的增大而上升,表面发射率的增大使氮氧化物体积分数峰值出现下降,降幅约7.9%。表面发射率的增大在维持火焰温度基本不变且氮氧化物排放降低的情况下,提升了火焰位置,因此为提升灶具热效率,应将主要优化方向集中在通过表面处理以提高板面的表面发射率。灶具热负荷和火孔内直径的增加对上板面温度的提升有明显的促进作用,当热负荷从3.1 kW增加至3.9 kW时,火焰中心温度增幅为5.3%,同时氮氧化物排放量随之增大。内直径对上板面温度的提升作用在其值大于1.10 mm后开始显现,内直径的增加会明显提高氮氧化物的排放。因此在适当考虑烟气中氮氧化物排放的范围内,可提高灶具的热负荷和火孔内直径。在灶具热负荷较小时,孔隙率不可过大,但随着热负荷的增加,孔隙率可适当增大。鉴于板面厚度增加会明显增加达到稳态所需的时间,因此不宜采用过厚板面,以3.00~4.00 mm为宜。

FLUENT software is used to numerically simulate the control variables of multiple parameters that affect the combustion performance of gas cooking appliance with porous metal plate. The normalization treatment and sensitivity analysis of each parameter are carried out,and the influence of each parameter on the combustion performance of the cooking appliance is discussed. To simplify the simulation calculation,half of a single fire hole on the porous metal plate is taken as the numerical simulation object and grid is divided for simulation. The following conclusions are drawn:the flame center position increases with the increase of the surface emissivity of the plate,and the increase of the surface emissivity causes the peak value of the nitrogen oxide volume fraction to decrease by about7. 9%. The increase of the surface emissivity raises the flame position while maintaining the flame temperature basically unchanged and reducing nitrogen oxide emissions. Therefore,in order to improve the thermal efficiency of the cooking appliance,the main optimization direction should be focused on improving the surface emissivity of the plate through surface treatment. The increase in the heat load of the cooking appliance and the inner diameter of the fire hole has a significant promotion effect on the increase in the upper plate surface temperature. When the heat load increases from 3. 1 k W to 3. 9 k W,the flame center temperature increases by 5. 3%,and the nitrogen oxide emissions increase accordingly. The increasing effect of the inner diameter on the upper plate surface temperature begins to appear after its value is greater than 1. 10 mm,and the increase of the inner diameter will significantly increase the nitrogen oxide emissions. Therefore, within the scope of properly considering the emission of nitrogen oxides in the flue gas,the heat load of the cooking appliance and the inner diameter of the fire hole can be increased. When the heat load of the cooking appliance is small,the porosity cannot be too large,but as the heat load increases,the porosity can be increased appropriately. In view of the fact that the increase of the thickness of the plate will obviously increase the time required to reach the steady state,it is not suitable to use the excessively thick plate,and the appropriate thickness is 3. 00 to 4. 00 mm.