稀释气对天然气掺甲醇裂解气预混层流燃烧特性的影响

Effects of Diluent Gas on Burning Characteristics in Natural Gas-Dissociated Methanol Gas-Air Premixed Flames

运用了定容燃烧弹-纹影系统球形发展火焰的研究方法,用体积比H2:CO=2:1的混合气来模拟甲醇裂解气,用N_2和CO_2作为稀释气,在初始温度为343 K、初始压力为0.3 MPa的条件下进行了稀释气-天然气-甲醇裂解气-空气预混燃烧试验,研究了不同当量比(0.8～1.4)下不同稀释气种类(N2和C02)及不同稀释气添加比例(0.05、0.1、0.15)对天然气-甲醇裂解气-空气(其中甲醇裂解气体积占比0.4、天然气体积占比0.6)层流燃烧速度、马克斯坦长度及胞状结构等燃烧特性的影响.并且在不添加稀释气的条件下,进行了同样初始温度和压力下的天然气(1/0.6/0.2)-甲醇裂解气(0/0.4/0.8)-空气预混层流燃烧的对比试验.结果表明:掺甲酵裂解气会增加混合气层流燃烧速率,促进胞状结构的产生;添加稀释气会降低层流燃烧速率;CO_2对流体动力学不稳定性的抑制作用以及对热扩散不稳定性的促进作用强于N2.在此条件下,热扩散不稳定性是影响火焰不稳定性的主要因素.

The experiments were conducted with the method of constant-pressure spherical flame in a constant-volume combustion chamber by using a schlieren system.Mixture (H2:CO=2:1 by volume) was used to simulate the dissociated methanol gas,and N2/CO2 were used as diluent gases.The experiments were conducted in the condition of initial temperature for 343K and initial pressure for 0.3MPa.The effects of different kinds of diluent gases (N2,CO2) and different adding proportions of diluent gas (0.05,0.1,0.15)under different equivalence ratios (0.8~1.4)on burning characteristics such as laminar burning velocities,Markstein lengths and cellular structures in natural gas-dissociated methanol gas-air mixture (ratio of dissociated methanol gas was 0.4while that of natural gas was 0.6 by volume)were studied.Moreover,experiments of natural gas (1/0.6/0.2)-dissociated methanol gas (0/0.4/0.8)-air mixture were conducted under the same temperature and pressure.The result showed that it would increase,the laminar burning velocities and the generation of cellular structures when adding dissociated methanol gas,however,it would decrease the laminar burning velocities while adding diluent gas.The suppression of C02on hydrodynamic instability and the promotion of CO2 on thermodynamic instability was stronger than that of N2.The flame instability was mainly affected by thermodynamic instability in this paper.