三旋流雾化装置中预燃级喷雾特性的实验研究

Experimental Investigation on Spray Characteristic of Pilot Stage in Triple Swirling Atomizer

关键词:  三旋流  预燃级  喷雾特性  近场区  液滴尺寸关系式

Key words:  Triple swirling  Pilot stage  Spray characteristic  Near field region  Droplet size correlation

摘要:

为深入研究三旋流分级燃烧室中预燃级的喷雾特性，采用煤油为工质，在接近贫油熄火状态时对某三旋流雾化装置中预燃级的雾化特性进行了实验研究。利用相位多普勒测速仪对雾化装置下游的整体喷雾场以及近场区喷雾进行了研究和分析。结果表明：下游喷雾场主要有中心回流区、高速区和喷雾边缘区，但是在X=10mm截面上高速区中存在着台阶低速区。喷雾结构由空心锥结构渐渐转变为全锥形。线平均后的液雾索泰尔平均直径SMDˉ沿轴向增加，气流压降是液滴平均尺寸的主要影响因素。雾化装置中的雾化过程符合复合式空气雾化。在X=10mm截面的近场区，径向上各点处的液滴轴向速度基本与液滴尺寸无关，而液滴径向速度与尺寸的关系与径向位置有关。对文献中提出经验预测公式进行了修正，得到适用于该雾化装置的液滴尺寸关系式，发现在空气压降为4kPa时可忽略第三级旋流气流，一二级旋流气流是近场区液滴平均尺寸的主导因素。

Abstract:

To investigate the spray characteristics of pilot stage in triple swirling staged combustor in depth， using kerosene， atomization characteristics of pilot stage in a triple swirling atomizer were experimentally investigated which is near the lean blowout condition. The whole spray field and near field region spray in the downstream of atomizer were investigated and analyzed by using phase Doppler anemometry. The result indicates that the downstream spray field mainly includes central toroidal recirculation zone， high-speed zone and spray edge zone， but there exists a step low-speed zone in the high-speed zone at X=10mm section. The spray structure gradually changes from a hollow-conical structure to full cone-type. Along axial the linear averaged Sauter mean diameter SMDˉ increases， and the airflow pressure drop has a major impact on mean droplet size. The atomization processes in the atomizer accord with hybrid airblast atomization. At the near field region of X=10mm section， the droplet axial velocity is basically independent with the droplet size in radially， while the correlation between droplet radial velocity and droplet size is related to the radially position. Revising the previously proposed empirical prediction formula， a droplet size correlation applicable to this atomizer is obtained. In addition， the first and second swirling airflow are the dominant factor of mean droplet size in the near field region when the pressure drop of airflow is 4kPa， the third swirling airflow could be ignored.