Premixed Combustion Flame Instability Characteristics (PREFIC)

由于热扩散和流体动力学不稳定性，预混火焰的胞状不稳定性和自加速现象在燃料燃烧中是常见的。在球形火焰的研究中，火焰的不稳定性对火焰的结构和速度有着重要的影响，其产生的自加速现象对各种燃烧系统的湍流燃烧速度有着重要的影响，并会引起较大的火灾和爆炸危险。绘制细胞不稳定性和自加速状态可以帮助改进燃烧模型，该模型广泛用于燃烧系统设计以及火灾和爆炸危险的调查。该项目分为两个主要工作包，其中研究正在从基本数据获取转向不稳定的原因，并最终导致自加速的后果。采用显微摄影和图像处理技术对火焰胞状结构进行数学表征和量化，而不是传统的通过计算火焰尺寸或压力历史来测量燃烧速度，引入了一个新定义的胞状因子来表征火焰胞状结构特征，首先通过测量胞状结构参数计算分析了火焰前缘胞的变化规律，这是定量确定充分发展的蜂窝状火焰的临界点和描述自加速的主要参数。目前的工作将开发一个新的燃烧速度模型火焰加速。改进的关联，提出了纳入瞬态和多维效应，有限速率化学，这是至关重要的预测工程模型的发展。

Cellular instability and self-acceleration of premixed flames are commonly observed in fuel combustion, due to the thermal-diffusive and hydrodynamic instability. Cellar instability significantly influences the flame structure and speed, and the resultant self-acceleration has been widely observed in spherical flame studies, with high influences on the turbulent burning velocity of various combustion systems and causing higher fire and explosion hazards. Mapping the regimes of cellular instability and self-acceleration could help improve combustion modelling which is widely used in design of combustion systems and investigation of fire and explosion hazards.The project is divided into two main work packages, in which the research is moving from basic dada acquirement to the cause of instability and in the end of the consequence of self-acceleration. The flame cellular structure will be mathematically characterised and quantified by the microscopic photography and image processing technique rather than traditionally by measuring burning velocity through calculation of flame size or pressure history.A newly defined Cellularity Factor is introduced to represent the flame cellular structure characteristics, and the variation regularity of flame front cells is firstly calculated and analysed by measuring the cellular structure parameters, which are the primary parameters to quantitatively determine the critical point of the fully developed cellular flame and to describe the self-acceleration. Present work will develop a new burning velocity model for flame acceleration.Improved correlations are proposed, incorporating transient and multidimensional effects, as finite rate chemistry, which are crucial for the predictive engineering model developments.