The impact of equivalence ratio oscillations on combustion dynamics in a backward-facing step combustor
The impact of equivalence ratio oscillations on combustion dynamics in a backward-facing step combustor
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DOI：
10.1016/j.combustflame.2009.07.024
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发表时间：
2009-11
影响因子：
4.4
通讯作者：
H. M. Altay;R. Speth;D. Hudgins;A. Ghoniem
中科院分区：
文献类型：
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作者：
H. M. Altay;R. Speth;D. Hudgins;A. Ghoniem
在常压、大气进口温度、稀薄预混后向阶梯燃烧室中，研究了丙烷-空气火焰的燃烧动力学。通过改变喷油器的位置来考察到达火焰的当量比振荡对燃烧动力学的影响。压力、速度、放热率和当量比的同时测量以及实验的高速视频被用来识别和表征几种不同的工作模式。当燃料被喷射到远离台阶的上游时，到达火焰的当量比是稳定的，燃烧动力学仅受火焰-旋涡相互作用的控制。在这种情况下，根据操作参数的不同，观察到不同的动态区域。当燃料被喷射到靠近台阶的位置时，到达火焰的当量比呈现振荡。在当量比振荡存在的情况下，即使到达火焰的当量比振荡与压力振荡异相，测得的声压级在整个稀薄平均当量比范围内也是显著的。燃烧动力学主要受火焰与旋涡相互作用的影响，当量比振荡起次要作用。在某些工况下，当量比振荡会在每个循环内引起燃烧动力学的变化，使整个贫当量比范围内的火焰不稳定，并增加贫燃极限下的平均当量比的值。
The combustion dynamics of propane–air flames are investigated in an atmospheric pressure, atmospheric inlet temperature, lean, premixed backward-facing step combustor. We modify the location of the fuel injector to examine the impact of equivalence ratio oscillations arriving at the flame on the combustion dynamics. Simultaneous pressure, velocity, heat-release rate and equivalence ratio measurements and high-speed video from the experiments are used to identify and characterize several distinct operating modes. When the fuel is injected far upstream from the step, the equivalence ratio arriving at the flame is steady and the combustion dynamics are controlled only by flame–vortex interactions. In this case, different dynamic regimes are observed depending on the operating parameters. When the fuel is injected close to the step, the equivalence ratio arriving at the flame exhibits oscillations. In the presence of equivalence ratio oscillations, the measured sound pressure level is significant across the entire range of lean mean equivalence ratios even if the equivalence ratio oscillations arriving at the flame are out-of-phase with the pressure oscillations. The combustion dynamics are governed primarily by the flame–vortex interactions, while the equivalence ratio oscillations have secondary effects. The equivalence ratio oscillations could generate variations in the combustion dynamics in each cycle under some operating conditions, destabilize the flame at the entire range of the lean equivalence ratios, and increase the value of the mean equivalence ratio at the lean blowout limit.