敞口式离心喷嘴内部流动特性的试验及模拟

Experimental and Numerical Investigation of Internal Flow Characteristics in an Open-End Swirl Injector

关键词:  离心喷嘴  流量系数  液膜厚度  空心涡  结构参数

Key words:  Swirl injector  Discharge coefficient  Film thickness  Air core  Geometrical parameters

摘要:

为了研究敞口式离心喷嘴内部流动特性，包括填充过程及结构参数和工作参数对流量系数及液膜厚度的影响，对7个不同切向孔直径及长径比的喷嘴展开了试验和数值模拟。采用高速背光对透明敞口式离心喷嘴进行光学测量，喷注压降从0.1～0.8MPa，结合数值模拟研究了旋流室内液膜的填充过程，捕获了空心涡形成及发展过程，得到了敞口式离心喷嘴液膜厚度和流量系数随结构参数及工作参数的变化规律。研究发现几何特性参数越高，液膜厚度、流量系数和质量流量越低；低压降时流量系数随喷注压降升高而略微增加，当喷注压降达到临界值0.4MPa后，流量系数和液膜厚度几乎不变，最大波动分别为1.1%和6%。综合考虑工作参数及结构参数，拟合流量系数及质量流量经验公式，最大偏差皆不超过10%。

Abstract:

In order to study the internal flow characteristics，including the filling process and the effects of geometrical parameters and operating parameters on the atomization characteristics of the open swirl injector，7 injectors with different tangential inlet diameters and ratios of nozzle length to nozzle orifice diameter were tested and simulated. Using high-speed shadowgraph on the transparent swirl injector，the liquid filling process in the swirl chamber was investigated combining with numerical simulation. And the injection pressure drop was among 0.1～0.8MPa. The formation and development of air core was captured. What’s more，the evolution laws of the liquid film thickness and discharge coefficient with the operating and geometric parameters were analyzed in detail. The geometric characteristic constant increases with a decrease in the liquid film thickness，discharge coefficient and mass flow rate. Discharge coefficient is a direct function to injection pressure drop under low pressure drop. After the injection pressure drop approaches or reaches a critical value of 0.4MPa，the liquid film thickness and discharge coefficient almost keep constant with maximum fluctuations of 1.1% and 6%，respectively. Comprehensively considering the effect of geometric and operating parameters，empirical formulas of discharge coefficient and mass flow rate were put forward as references for engineering applications with maximum relative errors of 10%.