Images of Local Propagation Speeds and Stretch Rates of Turbulent Premixed Flames to Improve Numerical Models

詹姆斯·F. DRISCOLL CTS-9904198这是一项首次对湍流预混火焰表面局部传播速度沿着进行量化的实验研究。 由于在起皱的火焰表面上形成凸起和尖点，某些火焰段以异常大的速度向前传播。 PIV-PLIF（粒子成像测速-平面激光诱导荧光）诊断已被用来测量的非定常，弯曲，二维层流火焰，经历火焰涡相互作用的传播速度。 在这项研究中，这种技术被扩展到三维（3-D）火焰的情况下，通过使用两套正交的激光片。 这些工作包括：（a）沿湍流火焰表面沿着的局部传播速度的测量;（B）三维火焰拉伸速率的测量;（c）产生异常大的局部传播速度的火焰前缘中的尖点和凸起的识别以及这些异常现象的物理原因的调查;图像允许将快速火焰传播与涡流的存在、火焰曲率或火焰段之间自由基的共享相关联;（d）将测得的传播速度与来自不同团体的高级直接数值模拟（DNS）的传播速度进行比较;局部传播速度是发展大涡模拟（LES）必须正确建模的关键参数预混燃烧和部分预混燃烧。 这些模型为湍流燃烧领域的重大新突破提供了可能性，包括开发低污染的燃气涡轮机和内燃机。

ABSTRACTJAMES F. DRISCOLL CTS-9904198This is an experimental study to quantify, for the first time, the local propagation speed along the surface of a turbulent, premixed flame. As bulges and cusps form on the wrinkled flame surface, certain flame segments propagate forward at unusually large speeds. A PIV-PLIF ( particle imaging velocimetry- planar laser induced fluorescence) diagnostic has been used to measure propagation speed for an unsteady, curved, two-dimensional laminar flame that undergoes a flame-vortex interaction. In this study, this technique is extended to the three-dimensional (3-D) flame case by using two sets of orthogonal laser light sheets. The effort includes (a) measurements of local propagation speed along a turbulent flame surface; (b) measurements of 3-D flame stretch rates; (c) identification of cusps and bulges in the flame front that yield abnormally large local propagation speeds and investigation of the physical reasons for these abnormalities; images allow correlation of fast flame propagation with the presence of a vortex, with flame curvature, or with the sharing of radicals between flame segments; (d) comparison of measured propagation speeds to those from advanced direct numerical simulations (DNS) from various groups; and to those predicted by the Theory of Flame Stretch.Local propagation velocity is the key quantity that must be correctly modeled in order to develop large-eddy simulations (LES) of premixed and partially premixed combustion. Such models offer the possibility of major new breakthroughs in turbulent combustion, including the development of low-polluting gas-turbine and internal-combustion engines.