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A Study on Effects of Spray Characteristics on Prevaporization and Premix Combustion Mechanism

喷雾特性对预汽化及预混燃烧机理的影响研究

基本信息

批准号：
07650232
负责人：
INAMURA Takao
金额：
$ 1.41万
依托单位：
Hirosaki University (1996)Tohoku University (1995)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

This study aims to clarify the relationship between spray characteristics, evaporation characteristics, combustion characteristics and emission characteristics, and to obtain the guide to the design of a premix and prevaporization combustor with low NOx emission. From the results of atomization experiments at room temperature, the radial profile of droplet mass flux approaches to uniform profile downstream. At the exit of the evaporation tube (495mm downstream from the nozzle), the droplet mass flux at the center is about twice of that near the tube wall. By evaporation experiments using a water at 30m/s of inlet air velocity and 550K of inlet air temperature, at 175mm far from the nozzle the droplet mass flux at the center is larger than that of the vapor. The droplet evaporation advances rapidly downstream, and at 430mm far from the nozzle the mass flux of the vapor at the center becomes larger than that of the droplet. Concerning to the radial profile of a rate of the vapor to the w … More ater component including droplets and vapor, the rate has a peak at the middle between the center and the tube wall. From the results of combustion experiments using a kerosene, the flame holding mechanism changes at 0.6 of equivalence ratio. The lower flammability limit decreases with a increase of a length of the vaporization tube, the inlet air temperature and the inlet air velocity. The NOx concentration in the exhausted gas increases exponentially with a increase of the equivalence ratio. The empirical equation of the emission index of NOx was obtained. The emission index of NOx can be reduced less than 1g (NOx) /kg (Fuel) and that of CO less than 10g (CO) /kg (Fuel) within the range of 0.54 to 0.68 of the equivalence ratio using newly designed combustor. By the numerical simulation of the spray flow and the spray evaporation without combustion under the condition of 30m/s of the inlet air velocity and 550K of the inlet air temperature, at 500mm far from the nozzle the air temperature at the center is 35K lower than that at the periphery, and the Sauter's mean diameter of the spray at the center is 30 micron smaller than that at the periphery. Less

本研究旨在阐明喷雾特性、蒸发特性、燃烧特性与排放特性之间的关系，为低NOx排放预混预汽化燃烧室的设计提供指导。从室温下的雾化实验结果来看，液滴质量通量的径向分布在下游趋于均匀分布。在蒸发管出口（喷嘴下游495mm处），中心液滴质量通量约为管壁附近液滴质量通量的2倍。在进气速度为30m/s，进气温度为550K的条件下，在距离喷嘴175mm处，液滴中心的质量通量大于水蒸气的质量通量。液滴蒸发向下游快速推进，在距离喷嘴430mm处，中心蒸汽的质量通量大于液滴的质量通量。在含液滴和水蒸气的水组分较多的情况下，在中心和管壁之间的中间位置有一个峰值。从煤油燃烧实验结果来看，当当量比为0.6时，持焰机理发生变化。可燃性下限值随汽化管长度、进气温度和进气速度的增加而减小。废气中NOx浓度随当量比的增大呈指数增长。得到了NOx排放指数的经验方程。采用新设计的燃烧室，在等效比0.54 ~ 0.68的范围内，NOx排放指标可降至1g (NOx) /kg（燃料）以下，CO排放指标可降至10g (CO) /kg（燃料）以下。通过对进气速度为30m/s、进气温度为550K条件下的喷雾流动和无燃烧蒸发的数值模拟，在距离喷嘴500mm处，中心处的空气温度比外围低35K，中心处喷雾的Sauter平均直径比外围小30微米。少