Rijke型燃烧器热声振动特性的试验研究

EXPERIMENTAL INVESTIGATION OF THERMOACOUSTIC VIBRATION CHARACTERISTICS IN A RIJKE-TYPE COMBUSTOR

为研究燃烧过程中的热声振动特性,搭建了Rijke型预混燃烧器热声振动特性试验台架,并进行了化学当量Ф为0.8、1.0和1.2的三组试验研究。Rijke型预混燃烧器为直径40 mm,管长1066 mm的不锈钢圆管,下端封闭,上端开口。致密堇青石材质的多孔介质稳燃体位于燃烧器四分之一管长处,甲烷与空气的预混气体在稳燃体上方燃烧。试验获得的燃烧温度位于611 K—943 K之间;热声振动频率在440 Hz—476 Hz之间;热声振动声压级位于131 dB—146 dB之间。试验发现,Rijke型预混燃烧器的燃烧温度在同一燃烧功率下基本一致,不受化学当量比的影响。热声振动频率随燃烧功率的增加轻微上升,不同化学当量比下振动频率的变化幅度不相同,贫燃和富燃时频率随燃烧功率的增加有较大的增加,且贫燃大燃烧功率时出现了低频大振幅振动与高频振动并存的现象。热声振动强度强烈依赖于燃烧功率和化学当量比,同一燃烧功率不同化学当量下的热声振动强度相差可达50%。

In order to study the characteristics of thermoacoustic vibration occuring in process of combustion,experimental setup is built.Three cases with chemical equivalent ratios Ф of 0.8,1.0 and 1.2 and different combustion powers for each equivalent ratio are investigated.A closed-open Rijke-type combustor with 40 mm of diameter and 1066 mm of length is used.The flame holder made of dense cordierite is installed in a quarter of the combustor length.The premixed gas of methane and air is burned at upstream of the flame holder.The obtained combustion temperature is between 611-943 K,and the sound pressure level of thermoacoustic vibration is between 131 and 146 dB at a resonant frequency range from 440 to 476 Hz.Experimental results show that the combustion temperature is identical in the same combustion power with different chemical equivalent ratios.The vibration frequency increases slightly with the combustion power,and there are different amplitudes in different chemical equivalent ratios,much larger amplitudes appear in rich or lean conditions compared with the stoichiometric cases.On the other hand,large-amplitude vibrations with low-frequency are observed in the lean condition with 431 W combustion powers.The vibration intensity is susceptible to the combustion power and the chemical equivalent ratios,it can have 50% difference chemical between different equivalent ratios with the same combustion power.