航空发动机离心式喷嘴宏观喷雾特性

Macro Spray Characteristics of Pressure-Swirl Nozzle in Aero-Engine

关键词:  离心式喷嘴  液膜破碎长度  雾化角  阴影法  纹影法

Key words:  Pressure-swirl nozzle  Breakup length of liquid film  Spray cone angle  Backlight illumination technology  Schlieren imaging technology

摘要:

为探究航空发动机离心式喷嘴的喷雾宏观特性，通过将该喷嘴在高温高压定容弹中进行喷雾过程的实验，并结合阴影法与纹影法进行光学测量。首先以水作为射流工质，观察不同喷射压力下水进入大气环境中的雾化角变化，发现喷嘴结构对雾化角有着重要影响，最大雾化角与喷嘴出口的导流结构夹角相等。其次以正癸烷作为工质，通过不同环境压力和温度下的多组实验测量其它喷雾宏观特性如液膜破碎长度，结果表明在背压大于1.75MPa的工况下，该离心式喷嘴无法形成清晰稳定的锥形喷雾结构，此外还揭示了高背压加强了气动力而高环境温度减小了表面张力和粘性力，两者都起着促进雾化的作用。

Abstract:

To clarify the macro spray characteristics of pressure-swirl nozzle in aero-engine， a certain type of pressure-swirl nozzle was used to simulate the fuel injection process in a high-temperature and high-pressure constant-volume chamber. Optical diagnostic measurements were conducted through backlight illumination technology and schlieren imaging technology. Firstly， water was injected into atmosphere to investigate the change of spray cone angle at different injection pressures. It was found that the nozzle structure has an important influence on the spray cone angle and the maximum spray cone angle is equal to the angle of the flow-guiding structure at the nozzle outlet. Secondly， n-decane was used as spray substance to investigate other macroscopic spray characteristics such as breakup length of liquid film at different environmental pressures and temperatures. The results showed that the pressure-swirl nozzle could not form a clear and stable conical structure when the ambient pressure was greater than 1.75 MPa. It was also found that increased ambient pressure promotes atomization by increasing aerodynamic forces and increased ambient temperature promotes it by decreasing viscous force and surface tension of spray.