不同工况下针栓喷注器雾化特性研究

Study on Atomization Characteristic of Needle Bolt Injector under Various Working Conditions

摘要: 对针栓喷注器的工况分析，采用对其雾化过程模拟仿真的方式进行。使用流体体积法、界面对流方法、网格自适应技术，基于OpenFOAM计算流体力学平台，开展对不同工况下针栓式喷注器雾化情况仿真研究，完成了针栓正常开度及大开度工况下的雾化仿真并对比了其结果；使用基于拉格朗日法的求解器来对液滴的数目、直径、位置等进行统计，通过对仿真流场结构对比及仿真数据对比两方面，来开展对具体问题的分析。研究分析初步发现：针栓喷注器喷注时，正常开度与大开度工况下液体都会出现沿针栓下表面附壁流动的情况，影响到液体的雾化。正常开度下液膜受轴向气体作用附壁流动，大开度下液体初速度较低而发生附壁流动。通过降低气体流量及提高液体初速度均可改善附壁流动现象。正常开度情况下轴向气体流量的增加将改善雾化质量，过高的气体流量将减少雾化液滴数量；大开度条件下径向液体流量的增加将使雾化平均直径升高，粒径均匀度改善，雾化液滴数量提高；相同条件下大开度工况较正常开度的雾化液滴数量少，而雾化质量高。

Abstract: The working condition analysis of the needle valve injector is carried out by simulating and mimicking its atomization process. Using the volume of method, interface convection method, and grid adaptive technology, based on the OpenFOAM computational fluid dynamics platform, the atomization of the needle valve injector under working conditions is simulated, and the atomization simulation under normal and large opening conditions of the needle valve is completed and compared. A solver based on the Lagrange method is used to count the number, diameter, and position of the liquid droplets. By comparing the simulation flow field structure and the simulation data, the analysis of specific problems is conducted. The preliminary research analysis found that during the injection of the needle valve injector, the liquid would flow along the lower surface of the needle valve both normal and large opening conditions, affecting the atomization of the liquid. In the normal opening condition, the liquid film flows along the wall due to the axial, and in the large opening condition, the liquid’s initial velocity is lower, causing it to flow along the wall. Both reducing the gas flow and increasing the initial velocity can improve the wall flow phenomenon. In the normal opening condition, increasing the axial gas flow will improve the atomization quality, but too high a flow will reduce the number of atomized droplets; in the large opening condition, increasing the radial liquid flow will increase the average diameter of the atomization, the uniformity of the droplet size, and increase the number of atomized droplets; under the same conditions, the large opening condition has fewer atomizedplets than the normal opening condition, but the atomization quality is higher.