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Analysis of Mechanism of and Model for Compression Ignition Diffusion Combustion in Burned Gas Diluted Mixture

已燃气体稀混合气压燃扩散燃烧机理及模型分析

基本信息

批准号：
11450090
负责人：
NISHIWAKI Kazuie
金额：
$ 3.26万
依托单位：
Ritsumeikan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450090/
关键词：
H.C.C.I EGR Heterogeneity Heat transfer Turbulent mixing Pseudo turbulence simulation law temperature Integral scale of concentration 圧縮自着火濃度温度 LES 濃度積分スケール既燃ガス希釈自着火反応動力学濃度むら温度むら

项目摘要

Theoretical and experimental analyses were made for the mechanism of premixed charge compression ignition and turbulent mixing process of gas jet of fuel for producing the premixed charge.Theoretical model was developed for compression-autoignition and combustion of heterogeneous mixture of fuel and air in a cylinder. The model relies on the spatially-filtered transport equations, instead of Reynolds averaged ones, integrating a reduced kinetic model for the low temperature oxidation reaction and a one-step global model for the hot flame reaction. The numerical computation of the model simulated each realization of spatial and temporal fluctuations of velocities, fuel concentrations and temperatures of the mixture blobs in sizes of almost the integral length scale of turbulence. The model reproduced the moderate combustion in a bulk, which features the premixed charge compression ignition process in low total-equivalence ratios or mixtures diluted with EGR gas or burned gas. The comput … More ational analyses showed that the heterogeneity in fuel concentration and temperature, and the dilution with burned gas are two equally dominant factors to give the moderate bulk combustion instead of abrupt pressure rise.In the experiments, plane images of scattered light from incense smoke in steady and unsteady air jets were photographed with a Nd : YAG laser in spatial resolution of 18 μm. The integral length scale was analyzed for the concentration field along the jet axis. It was revealed that flue integral length scale of concentrations decreases in a down steam direction, while the integral length scale of the velocity field increases. Experiments were conducted also with LIF technique to result in the same tendency in the integral length scale. Theoretical study gives an explanation that the turbulent mixing of concentrations is slower than that of momentum in a jet. This idea suggests that mixture formation by fuel jet needs additional turbulence generation when the momentum comes into well diffused state for faster mixture preparation. Less

对预混装药压缩点火机理和燃料气体射流产生预混装药的湍流混合过程进行了理论和实验分析。建立了非均质燃料-空气混合气在气缸内压缩自燃燃烧的理论模型。该模型依赖于空间过滤输运方程，而不是雷诺兹平均方程，集成了低温氧化反应的简化动力学模型和热火焰反应的一步全局模型。该模型的数值计算模拟了几乎在湍流积分长度尺度上的速度、燃料浓度和混合团温度的时空波动的每一种实现。该模型再现了整体的中度燃烧过程，其特点是在低总当量比或稀释EGR气体或燃烧气体的混合物中预混装药压缩点火过程。更多的国家分析表明，燃料浓度和温度的非均匀性以及燃烧气体的稀释是导致适度的大块燃烧而不是突然的压力上升的两个同样重要的因素。实验采用空间分辨率为18 μm的Nd: YAG激光器，分别在定常和非定常空气射流中拍摄了香烟散射光的平面图像。对沿射流轴方向的浓度场进行了积分长度尺度分析。结果表明，沿下蒸汽方向烟道浓度积分长度尺度减小，而速度场积分长度尺度增大。用LIF技术也进行了实验，在积分长度尺度上得到了相同的趋势。理论研究给出了湍流中浓度混合比射流中动量混合慢的解释。这一观点表明，为了更快地制备混合气，燃料射流形成混合气需要在动量达到良好扩散状态时产生额外的湍流。少