Ignition is of importance in many combustion applications and raises fundamental and practical issues. The light-round process corresponding to the flame spreading phase in the ignition of annular combustors is examined in this article by performing experiments in a model scale configuration “MICCA-Spray”. This system features 16 swirling injectors each comprising a hollow cone pressurized injector. Experiments are carried out with premixed gases as well as n-heptane and dodecane sprays. The flow, spray and flame are first characterized in a single injector configuration. Propagation from the initial kernel created by a spark plug is then observed using high speed light emission imaging. This provides flame structures at various times during the process and gives access to the time delays for flame merging. With n-heptane and dodecane fuel injection, it is found that the light-round process is similar to the one observed under fully premixed propane/air experiments but the duration of the process is augmented especially for the less volatile fuel. It is also confirmed that the delay is notably influenced by thermal conditions prevailing in the chamber at the moment of ignition, injection process and fuel composition. Making use of a flamelet like model of the combustion process, the relative changes in light-round time delay are found to be, to the first order, proportional to the relative changes in laminar burning velocity induced by the fuel spray in the air flow.

点火在许多燃烧应用中很重要，并引起了基本和实际的问题。本文通过在模型规模配置“ MICCA-Spray”中进行实验，研究了与环形燃烧器点火中的火焰扩散阶段相对应的轻绕过程。该系统具有16个涡旋式喷油器，每个喷油器都包括一个空心圆锥增压喷油器。实验是使用预混合气体以及正庚烷和十二烷喷雾剂进行的。首先以单喷射器配置来表征流量，喷雾和火焰。然后使用高速光发射成像观察火花塞产生的初始核的传播。这在过程中的各个时间提供了火焰结构，并提供了火焰合并的时间延迟。使用正庚烷和十二烷燃料喷射时，发现轻循环过程类似于在完全预混合的丙烷/空气实验中观察到的过程，但是该过程的持续时间增加了，特别是对于挥发性较低的燃料。还可以确定，延迟明显受点火，喷射过程和燃料成分时腔室内普遍存在的热条件的影响。利用类似于火焰过程的燃烧过程模型，发现光轮时间延迟的相对变化与空气流中的燃料喷雾引起的层状燃烧速度的相对变化成一阶。已经发现，轻绕过程类似于在完全预混合的丙烷/空气实验中观察到的过程，但是该过程的持续时间增加了，特别是对于挥发性较小的燃料。还可以确定，延迟明显受点火，喷射过程和燃料成分时腔室内普遍存在的热条件的影响。利用类似于火焰过程的燃烧过程模型，发现光轮时间延迟的相对变化与空气流中燃料喷雾引起的层流燃烧速度的相对变化成一阶。已经发现，轻绕过程类似于在完全预混合的丙烷/空气实验中观察到的过程，但是该过程的持续时间增加了，特别是对于挥发性较小的燃料。还可以确定，延迟明显受点火，喷射过程和燃料成分时腔室内普遍存在的热条件的影响。利用类似于火焰过程的燃烧过程模型，发现光轮时间延迟的相对变化与空气流中燃料喷雾引起的层流燃烧速度的相对变化成一阶。