来流条件对微燃烧室中庚烷燃烧特性的影响

Effects of Inlet Flow on Combustion Characteristics of n-Heptane in a Micro-Combustor

为了通过改变来流条件提高微燃烧器中火焰的稳定性,使用液体正庚烷作为燃料,在内径为4mm的微燃烧室中,对不同庚烷流量和氧气浓度下庚烷液滴的燃烧特性进行了实验研究。结果表明,固定当量比为0.9,庚烷流量由10μL/min增大到30μL/min时,点火时间缩短,液滴滴落并形成液膜,液膜对点火以及稳定火焰有利。固定来流速度为0.33m/s时,加入氧气后,火焰出现瞬时喷射现象,但火焰不会熄灭。增加氧气浓度可以缩短点火时间,增强火焰稳定性。随着氧气浓度的增大,火焰长度总体上先增大后减小。燃烧声振呈现出低频特性,氧气浓度为0.46时声振最为强烈。

In order to improve flame stability by changing inlet flow condition, following experiments were performed by using n-heptane as fuel in a micro-combustor of 4mm internal diameter to study effects of fuel flow- rate and oxygen concentration on n-heptane droplet combustion in micro-tube. It was found that, when equiva- lence ratio is fixed at 0.9 and heptane flow rate increases from 10μL/min to 30μL/min, ignition time decreases and droplet drips. Then the film was formed, which was beneficial for ignition and flame stability. At a fixed inlet flow velocity of 0.33m/s, instantaneous jet flame appeared when pure oxygen was added to air and the flame didn＇ t quench. Increasing oxygen concentration can reduce ignition time and improve flame stability. With in- creasing of oxygen concentration, flame length first increased and then decreased on the whole. Combustion sound-vibration exhibited low frequency characteristics and became most intense when oxygen concentration is 0.46.