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为研究滞止点回流燃烧器的热声脉动特性,搭建了实验室规模的滞止点回流燃烧器试验台架,进行甲烷空气火焰的多工况试验研究。燃烧器采用同轴设计,中心管为燃料风管,外管套为空气管。燃烧室为内径48 mm,高300 mm的石英玻璃管,下端平齐密封,上端开口,燃烧器朝下并且其轴线与燃烧室轴线一致。研究发现,过低的输入功率将不能实现滞止点回流燃烧方式;当系统处于滞止点回流燃烧方式时,系统激发起剧烈的热声不稳定,其压力波的主峰振幅和有效振幅随着化学当量比的增大而增大,有效声压级超过138 dB;主峰共振频率与化学当量比无关,半峰频宽介于主峰频率的4%到10%之间,预示着滞止点回流燃烧器激发起的热声脉动在主峰频率附近声能分散,从而造成有效声压级与主峰声压级之间相差10 dB以上。另外,燃烧器出口的温度、NOx浓度和CO浓度均随着化学当量比的增大而增加,CO浓度的增加主要是由于化学当量比的增大,增加了燃料扩散的难度,从而提高了燃烧不完全性。
In order to study the thermoacoustic pulsation characteristics of stagnant point reflow burner, a lab-scale stagnation point reflow burner test bench was set up to study the multi-condition test of methane air flame. Burner coaxial design, the central tube for the fuel duct, the outer tube for the air tube. The combustion chamber is a quartz glass tube with an internal diameter of 48 mm and a height of 300 mm. The lower end is flush-sealed, the upper end is open, the burner faces down and its axis coincides with the axis of the combustion chamber. The results show that when the input power is too low, the stagnation point back-flow combustion mode can not be achieved. When the system is in the stagnation point back-flow combustion mode, the system stimulates violent thermoacoustic instability. The main peak amplitude and effective amplitude of the pressure wave The stoichiometric ratio is increased and the effective sound pressure level is over 138 dB. The resonance frequency of the main peak has nothing to do with the stoichiometric ratio. The half-peak bandwidth is between 4% and 10% of the main peak frequency, which indicates the stagnant point return The thermoacoustic pulsation excited by the burner is dispersed in the vicinity of the main peak frequency, resulting in a difference of more than 10 dB between the effective sound pressure level and the main peak sound pressure level. In addition, the outlet temperature of the burner, the concentration of NOx and the concentration of CO both increase with the increase of the stoichiometric ratio. The increase of CO concentration is mainly due to the increase of the stoichiometric ratio, which increases the difficulty of fuel diffusion and improves the combustion Incompleteness.