基于二氧化碳红外热成像的火焰起升高度分析

Analysis of Premixed Jet Flame Lift-Off Height of Droplet Streams Based on CO2 Infrared Thermal Imaging

摘要:

基于CO2红外热成像方法拍摄了可控活化热氛围下的正庚烷液滴群预混射流火焰，测量了火焰起升高度，研究了热氛围协流温度、液滴群预混当量比、液滴群射流速度3个因素对起升高度的影响规律.结果表明：射流火焰起升高度主要受到化学着火延迟期控制，起升高度随着协流温度的升高而降低，但当协流温度足够高时，起升高度几乎不再变化；当量比增大会使物理着火延迟期缩短，从而使火焰起升高度降低；在相同的当量比下，如果协流温度较低，射流出口速度增加会提高火焰起升高度，而当协流温度高于某临界温度后，加大射流出口速度却会降低火焰起升高度.

Abstract:

The CO2 infrared thermal imaging technology was used to capture the premixed nheptane droplet stream jet flames in a controllable active thermo-atmosphere. The flame liftoff heights were measured by developing an in-house picture processing code. The effects of co-flow temperature, premixed equivalence ratio and jet velocity were studied. The experimental results showed that the lift-off height of jet flame was mainly controlled by chemical ignition delay, the flame height decreased with the increase of co-flow temperature. Besides, when the co-flow temperature was high enough, the liftoff height almost did not further decrease. The increasing equivalence ratio shortened the physical ignition delay, making the lift-off height decrease. When the equivalence ratio was fixed, there existed a critical co-flow temperature. Increasing the jet velocity could improve the lift-off height when the co-flow temperatures were lower than the critical value. But the lift-off hight would derease when the co-flow temperature is higher than the critical values.