振荡环境下正己烷和异辛烷液滴燃烧特性研究

Combustion Characterization of N-hexane and Iso-octane Droplets in an Oscillating Environment

以正己烷和异辛烷燃料液滴为对象,在频率为100、200、500 Hz和声压为12.5、25.0、37.5 Pa的声波激励下对其蒸发点火燃烧特性进行实验研究,以确定不同频率和压强的声波对正己烷和异辛烷液滴点火和燃烧的影响。结果表明,声波振荡不会改变液滴燃烧的控制机制,液滴燃烧受液滴蒸发过程控制。施加100 Hz、25 Pa的声场激励后,正己烷和异辛烷液滴的点火延迟时间分别减小了72%和40%。燃料液滴的燃烧火焰对声波振荡的响应具有低通滤波的特点。在声波频率为100 Hz时,正己烷和异辛烷液滴燃烧过程中出现了明显的火焰跳动。在振荡环境中,声波频率越低,压强越大,正己烷和异辛烷燃料液滴的燃烧速率越高,两者均在100 Hz、37.5 Pa时燃烧速率最大,分别为0.3842和0.3139 mm^(2)·s^(-1),比未加振荡时分别增大了43.2%和52.6%。

The evaporation,ignition and combustion characteristics of n-hexane and iso-octane fuel droplets are experimentally investigated under acoustic excitation at 100,200,500 Hz,and sound pressure of 12.5,25.0 and 37.5 Pa to determine the effects of acoustic waves at different frequencies and pressures on the ignition and combustion of n-hexane and isooctane fuel droplets.The results show that the acoustic oscillation does not change the control mechanism of droplet combustion,which is still controlled by the droplet evaporation process.After applying a sound field excitation of 100 Hz and 25 Pa,the ignition delay time of n-hexane and iso-octane droplets are reduced by 72%and 40%,respectively.The response of fuel droplet combustion flame to acoustic wave oscillation is characterized by low-pass filtering.When the frequency of sound wave is 100 Hz,the flame pulsation of n-hexane and iso-octane droplet combustion occurs obviously.In the oscillating environment,the lower the sound wave frequency and the higher the pressure,the higher the combustion rate of n-hexane and iso-octane fuel droplets.Both of them show the maximum combustion rate at 100 Hz and 37.5 Pa,which are 0.3842 and 0.3139 mm^(2)·s^(-1),respectively,increasing by 43.2%and 52.6%compared with the case without oscillation.