Combustion Analysis of Unsteady Diffusion Flame of Spray by Means of Measurement of Spatial Distribution of Chemical Species and Soot

本项目期间的研究成果概述如下：1)非定常蒸发喷雾撞击平热壁的建模。采用液滴破碎模型、液滴分散模型和传热模型这三种新的模型对非定常喷雾撞击平热壁的蒸发过程进行了精确的模拟，作为其火焰模拟的重要步骤。它们可以表达非沸腾、成核、转变和膜沸腾的所有蒸发现象。应用这些模型，利用KIVA-II原始程序对目标喷雾进行了模拟。模拟得到的燃料蒸气浓度分布和液滴包裹分布与激光诱导法检测的结果吻合较好。2)采用光学方法对直喷柴油机喷雾非定常扩散火焰的燃烧分析利用光学通道对直喷柴油机产生的客观火焰进行了烟尘、OH自由基和火焰温度分布的检测，采用双色法测量了化学物质代表OH自由基的自然排放量。得到以下主要结论：(1)扩散燃烧期间平均相对烟灰直径随着时间的延长而增大。(2)平均相对烟炱数密度在燃烧由预混合燃烧转向扩散燃烧时达到峰值。(3)在燃烧室的中心区域，预混合燃烧产生了大量的小直径煤烟。(4) OHI自由基自然排放的首次出现要晚于烟尘。3)采用光学方法对直喷柴油机喷雾非定常扩散火焰进行燃烧分析。采用双色法测量了目标火焰中OH自由基的自然排放分布、烟尘的自然排放分布和火焰温度的分布。得到以下主要结论：(1)在燃烧初期，旋流室内出现逆时钟方向的流动。(2)燃烧中期，涡流与主室之间通道附近火焰温度较低。(3) OH自由基在通道附近和火焰尖端区域自然释放。少

The outline of research results conducted during the term of this project is as follows :1)Modeling of unsteady and evaporating spray impinging on a flat and hot wallThe evaporating process of an unsteady spray impinging on a flat and hot wall is simulated precisely by use of new three models, that is, droplet breakup model, droplet dispersion model and heat transfer model, as the significant step of the simulation of its flame. They can express all the evaporation phenomena of non-boiling, nucleate, transition and filmboilings. The objective spray is simulated by KIVA-II original code applying these models. The simulated results of distributions of fuel vapor concentration and droplet parcels agree very well the experimental results detected by the laser induced method.2)Combustion analysis of unsteady diffusion flame of spray in direct injection diesel engine with optical accessThe simultaneous application of methods of laser induced scattering and laser induced incandescence, that o … More f two-color method and the measurement of the natural emission of OH radicalas the representative of chemical species were carried out in the objective flame generating in a direct injection diesel engine with the optical access to detect distributions of soot, OH radical and flame temperature. The following main conclusions are drawn :(1)The mean relative soot diameter increases as the passage of the time during the period of diffusion burning.(2) The mean relative soot number density has the peak when combustion turns from the pre-mixed burning to the diffusion burning.(3)In the central region of the combustion chamber a great deal of soots with small diameter produce by the pre-mixed burning.(4)The first appearance of the natural emission of OHI radical is later than that of soot.3)Combustion analysis of unsteady diffusion flame of spray in in-direct injection diesel engine with optical accessThe distribution of the natural emission of OH radical and those of soot and flame temperature by means of the two-color method were measured in the obj ective flame. The following main conclusions are obtained :(1)The counter clock wise flow appears in the swirl chamber during the initial combustion stage.(2)The flame temperature is low near the passage way between both swirl and main chambers during the middle combustion stage.(3)The natural emission of OH radical breaks out near the passage way and the flame tip region. Less