高温条件下柴油机喷雾粒度的测量

Drop Size Measurement of a Diesel Spray at Elevated Temperature

为了了解柴油机燃烧室中燃油与空气的混合及后续燃烧过程，准确地描述燃油雾化和油滴蒸发过程是至关重要的。运用激光衍射法测量液体喷雾粒度具有时喷雾无干扰、设备简单、数据处理迅速等优点，但这种方法对加热环境中的蒸发液雾进行测量时，由于先路上存在的温度及浓度梯度，激光被折射而偏转，测量结果受到严重影响。以往对柴油机喷雾的测量大都是在常温不蒸发条件下进行的，而本文则是通过对粒子激光衍射测量原理的深入分析，对基于激光衍射法的ＭＡＬＶＥＲＮ２６０４Ｃ粒度测量系统加以改进，排除了加热气体中温度和浓度梯度对测量结果的影响，在模拟柴油机燃烧室高温条件下的定容加热装置中，成功地测量不同温度下柴油机喷雾粒度分布，其测量条件为：温度３００～１０００Ｋ，压力０．１～０．５ＭＰａ。结果表明，在保持环境密度不变的条件下，温度在３００～５００Ｋ之间变化时，喷雾的索特平均直径变化不大，而当温度节过５００Ｋ时，喷雾的索特平均直径迅速增加，达到最大值后再缓慢减小。本文对这一实验结果进行了分析。

Accurate descriptions of behavior of atomizating and vaporiaing in the fuel spray are importantfor comprehension of the processes of air fuel mixing and subsequent combustion.When the laserdiffraction technique, which is simple, high speed in data processing and undisturbed to spray, is applied to measure drop size distribution of fuel spray in heated air, the laser beam is diffracted in a random way because of the temperature and concentration gradients and the measurement isheavily distorted. In the past, it is at ordinary ambient temperature that most of researches on spray drop size measurement have been carried out. In this study, based on the principle of laserdiffraction, the measurement system of MALVERN 2604C particle sizer was improved and with the influence of temperature and concentration gradients being eliminated, the drop size distributions ofdiesel spray at different ambient temperature were measured successfully in a constant volume bomb which simulated elevated temperature condition in diesel chamber. Test condition is in atemperature range from 300K to 1000K and a pressure range from 0.1MPa to 0.5MPa. The resultsshowed that with the ambient gas density unchanged, when ambient temperature increased from 300K to 500K, the Sauter Mean Diameter (SMD) of spray changed a little and when ambient temperature increased more than 500K, the SMD of spray increased to maximum rapidly, and then decreased slowly with a further increase of ambient temperature. The results were analyzed in the paper.