稀释率与温度耦合作用对天然气预混燃烧等量影响研究

Research on Equivalent Effects of Dilution Ratio and Temperature on Premixed Combustion of Natural Gas

基于定容燃烧弹,利用球形发展火焰和纹影法研究了在初始压力0.3 MPa、当量比1.0条件下,不同初始温度、稀释率时的天然气预混燃烧等量影响关系。分析了拉伸火焰传播速度、无拉伸火焰传播速度、马克斯坦长度、层流燃烧速率及NOx排放变化规律。结果表明:在拉伸火焰传播速度相近组别的工况点,无拉伸火焰传播速度、火焰发展期、燃烧持续期近乎相同,但层流燃烧速率存在较大的差异;在稀释率较小阶段,无拉伸火焰传播速度和层流燃烧速率受稀释率影响比受初始温度影响更大。进一步研究发现:温度差50 K与稀释率差2%具有一定等量影响效果;相近拉伸火焰传播速度组别的边界条件下,相比更小初始温度与稀释率工况点,更高初始温度与稀释率工况点的NOx排放量更低。

The equivalent effects of initial temperature and dilution ratio on premixed combustion of natu- ral gas in the constant volume combustion bomb are studied. The initial pressure Pu and equivalence ratio th are set to be 0. 3 MPa and 1.0 in experiment, respectively, and the ball type flame extension method by high speed schlieren photography is used in the experiment. Stretched flame propagation velocity S, unstretched flame propagation velocity SL, Markstein length Lb, laminar combustion velocity uL and NOx emission are analyzed in detail. The results show that SL, flame development duration and combustion duration are nearly identical, but the laminar burning velocity uL has a big difference at the operating points that have similar S, value. The influence of dilution ratio on SL and uL is greater than that of initial temperature when the dilution ratio is small. Further research finds that the temperature difference ATu = 50 K has equivalent effect on combustion process compared with dilution ratio ADR = 2%. Under the boundary conditions of the similar Sn, the NOx emission is lower under the conditions of higher initial temperature and dilution ratio compared with the smaller initial temperature and dilution ratio.