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The effects of volume expansion and laminarization on turbulent mixing in a diffusion flame

扩散火焰中体积膨胀和层流对湍流混合的影响

基本信息

批准号：
08650256
负责人：
SHIOJI Masahiro
金额：
$ 1.41万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

This study aims at the clarification of the non-equilibrium process and turbulence generation in the diffusive combustion. The contents of the present study are summarized as follows :1. Particle image velocimetry(PIV)for measuring velocity vectors was applied to the flow in a methane jet flame and a cold methane jet. Characteristics of turbulent eddies were clarified from the distribution of fluctuating velocity and vorticity. Results show that eddies generated inside flame front entrain the combustion products into the fuel stream, at the same time the dissipation of turbulence eddies takes place by the laminarization due to local heat-release.2. Time-repetitive measurements of gas flow using cross-correlation particle image velocimetry is developed. The velocity vector is accurately estimated from the interpolated cross-correlation function. The application of this method to the flow in a methane jet flame and a nitrogen jet is demonstrated, and the distributions of the ensemble-averaged velocity and turbulence intensity are calculated from the change of velocity vectors with time. The results show that this method may successfully give the feasible information about turbulence characteristics.3. Numerical simulation were performed to predict fluid motions induced by interactions between density and pressure gradients due to the presence of a vortex string situated in a deviated position from the jet flame axis. Deformation and stretching of the flame front take place once the vorticity production becomes stronger than the dissipation due to viscosity. When either the pressure gradient or the density gradient is high, the vorticity production proceeds at a high rate, which promotes the deformation of flame front and accelerates the heat release.

本研究旨在澄清扩散燃烧中的非平衡过程和湍流产生。本研究的内容概括如下： 1．将用于测量速度矢量的粒子图像测速（PIV）应用于甲烷喷射火焰和冷甲烷射流中的流动。从脉动速度和涡度的分布阐明了湍流涡流的特征。结果表明，火焰前锋内部产生的涡流将燃烧产物夹带到燃料流中，同时由于局部放热产生层流，使湍流涡流消散。 2．开发了使用互相关粒子图像测速技术对气体流量进行时间重复测量。速度矢量是根据插值互相关函数准确估计的。演示了该方法在甲烷射流火焰和氮气射流流动中的应用，并根据速度矢量随时间的变化计算了系综平均速度和湍流强度的分布。结果表明，该方法可以成功地给出湍流特性的可行信息。 3．进行数值模拟以预测由于存在位于偏离喷射火焰轴的位置的涡流串而导致密度和压力梯度之间的相互作用引起的流体运动。一旦产生的涡量强于粘性引起的耗散，火焰锋就会发生变形和拉伸。当压力梯度或密度梯度较高时，涡量产生速度较高，促进火焰前锋变形，加速热量释放。