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

关键词:  微小尺度燃烧  火焰稳定性  氧气浓度  庚烷液滴  声振

Key words:  Micro scale combustion  Flame stability  Oxygen concentration  n-heptane droplet  Sound vibration

摘要:

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。

Abstract:

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 flowrate and oxygen concentration on n-heptane droplet combustion in micro-tube. It was found that，when equivalence 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 increasing 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.