不同喷口扩张角下离心喷嘴雾化锥角特性研究

Effects of Trumpet Angle on Spray Angle Characteristics of Pressure Swirl Atomizer

关键词:  离心喷嘴  扩张角  雾化锥角  回流区  湍流模型  数值模拟

Key words:  Pressure swirl atomizer  Trumpet angle  Spray angle  Reflux region  Turbulence model  Numerical simulation

摘要:

为研究扩口式离心喷嘴的雾化锥角特性，对5个不同扩张角度的喷嘴展开了试验与数值计算研究。试验以RP-3航空煤油为工质，采用高速摄影对油雾场进行拍摄，Matlab二值化处理得到雾化锥角；数值计算采用VOF（Volume of fluid）方法结合RSM（Reynolds stress model）湍流模型。研究表明：随着扩张角的增大，锥角不是单一的变化规律，而是呈先增大后减小的趋势，且不同油压差下锥角峰值及其对应的扩张角有所差异。揭示了随扩张角增大，扩张段内液膜呈现附壁/未附壁两种流动模态。结合试验与理论计算结果分析，发现供油压差增大后，60°扩张角会限制锥角的大小，使锥角峰值出现在90°扩张角处。然后，比较100°，120°扩张角的气液两相图，发现扩张段内的射流使附近空气与其同方向运动产生回流区，而回流区与空气核相互作用反过来又影响着射流的偏转幅度，决定液膜未附壁时的锥角值。最后比较发现平口喷嘴的雾化特性决定了两种模态的出现与否，解释了已有研究中规律不一致的原因。

Abstract:

In order to study the spray angle characteristics of pressure swirl atomizer with trumpet， 5 atomizers with different trumpet angles were tested and simulated. RP-3 aviation kerosene was used as working substance in the experiment. The spray pattern was observed by a high speed camera， and the spray angle was obtained by Matlab binarization processing. The VOF （volume of fluid） method and RSM （Reynolds stress model） turbulence model were carried out. The results show that： the spray angle increases first and then decreases with increase of trumpet angle， it does not show a single change rule， and the maximum spray angle correspondes to different trumpet angles under different oil pressures. It revealed that with the increase of trumpet angle， film show two different flow modes： deflected/detached. Combined experimental and theoretical results， it is found that when the pressure drop increases， the 60° trumpet angle limits spray angle and the maximum spray angle appeares at 90° trumpet angle. By comparing the gas-liquid two-phase diagrams at 100° and 120° trumpet angle， it is obvious that a reflux region is generated owing to the same direction movement of the jet and nearby air in the trumpet section. In turn， the interaction between the reflux region and air core affects the deflection amplitude of the jet flow， which can determine spray angle when the film is deflected. Finally， it is found that the spray characteristics of the plain atomizers determine whether the two modes appear or not， and explain the reasons for the inconsistency in the existing studies.