进口速度分布对钝体稳定器贫油点熄火性能的影响研究

Effects of Inlet Velocity Profile on Lean Ignition and Lean Blowout Limits of a Bluff Body Flame-Holder

关键词:  速度构型  钝体  点火  熄火  流场特性

Key words:  Velocity profile  Bluff body  Lean ignition limit  Lean blowout  Flow characteristic

摘要:

为了探究燃烧室不均匀进口速度分布对燃烧性能的影响，采用试验的方法，开展了0.101MPa，700K进口条件下四种进口速度分布对钝体稳定器贫油点熄火性能的影响研究，结合流场特性分析了贫油点熄火性能变化的原因，四种进口速度分布依次为：h/H=0,3/6, 4/6和5/6（其中h为速度峰值距离通道底部的高度，H为试验通道的高度）。结果表明：整体而言，均匀进口贫油点熄火性能优于非均匀进口。当h/H=3/6时，贫油点熄火性能最差；而当h/H=5/6时，贫油点熄火性能最优。随着h/H由3/6增大到5/6时，贫油点火当量比下降7.39%，贫油熄火当量比下降18.45%。当进口速度分布为h/H=0和3/6时，钝体稳定器下游回流区基本对称；而当h/H=4/6和5/6时，钝体下游回流区不对称，且每个涡出现主副双涡心，存在流体由一个涡心向另一个涡心流动的现象。同时，当进口速度分布由h/H=3/6增大到h/H=5/6时，钝体下游回流区变长，其特征长度L_{vc_A}增大14.56%，L_{vc_B}增大50.70%。

Abstract:

In order to explore the effects of non-uniform inlet velocity distribution of combustion chamber on combustion performance, experimental studies are conducted to investigate the characteristics of lean ignition and lean blowout limits at 700K and 0.101MPa with four velocity profiles, namely h/H=0, 3/6, 4/6 and 5/6, where h/H describes the shape of the velocity peak, as h is the length between the velocity peak and channel bottom, H is the height of rectangular channel. Besides, the performance of lean ignition and blowout is well explained by the experimental flow characteristic downstream of the bluff body. Results indicate that overall the lean ignition and lean blowout limits at the uniform inlet velocity profile are greater than those at the non-uniform one. The worst performance of lean ignition and lean blowout occurs at h/H=3/6, while the best one happens at h/H=5/6. With the stepwise increase of h/H from 3/6 to 5/6, the equivalence ratios of lean ignition and lean blowout decrease by 7.39% and 18.45%, respectively. Additionally, the asymmetry recirculation downstream of bluff body occurs at h/H=0 and h/H=3/6, whereas the asymmetry recirculation happens at h/H=4/6 and h/H=5/6, in which the vortex contains a primary and secondary vortex center and there exists a phenomenon that the fluid flows from one vortex to another. At the same time, with the increase of h/H from 3/6 to 5/6, the characteristic length of L_{vc_A} and L_{vc_B} in the recirculation zone increase 14.56% and 50.70%, respectively.