Title: Thermal-diffusive instabilities in unstretched, planar diffusion flames Show Chinese title

Title: 非拉伸平面扩散火焰中的热-扩散不稳定性

Abstract: Our recent development of a novel research burner has made it possible to experimentally investigate truly unstretched and planar diffusion flames. Hence it has become feasible to directly validate theoretical models for thermal-diffusive instabilities in idealized one-dimensional diffusion flames by experiment. In this paper, the instabilities observed close to the lean extinction limit have been mapped as a function of the Lewis numbers of both reactants. Cellular and pulsating instabilities are identified in parameter regions corresponding qualitatively to theoretical predictions. A detailed investigation of these two types of instabilities reveals the dependence of the cell size and pulsation frequency of unstable flames on the transport properties of the reactants and on flow conditions. While the experimental scaling of the cell size is found in good agreement with theoretical models, the comparison with theory remains inconclusive for the scaling of the pulsation frequency. An experimental correlation for the pulsation frequency in terms of flow parameters, transport properties, in particular the Damkoohler number, and oscillation amplitude has been developed and awaits theoretical interpretation. Show Chinese abstract

Abstract: 我们最近开发的一种新型研究燃烧器使得实验研究真正未拉伸和平面扩散火焰成为可能。因此，通过实验直接验证理想化一维扩散火焰中的热-扩散不稳定性理论模型成为可能。在本文中，靠近贫油熄灭极限处观察到的不稳定性已被绘制为两种反应物的Lewis数的函数。在定性上与理论预测相对应的参数区域内识别出细胞状和脉动不稳定性。对这两种不稳定性进行详细研究揭示了不稳定火焰的细胞尺寸和脉动频率与反应物的传输特性和流动条件之间的依赖关系。虽然实验得到的细胞尺寸的尺度关系与理论模型相符，但脉动频率的尺度关系与理论的比较仍不确定。已经建立了一个以流动参数、传输特性（特别是Damkoohler数）和振荡幅度表示的脉动频率的实验相关性，并等待理论解释。