篦齿封严封油特性的数值与实验研究

Numerical and Experimental Investigations on the Oil Sealing Characteristics of the Labyrinth Seal

封严是燃气轮机空气系统中的重要单元,其密封特性对燃气轮机性能有重要影响。篦齿作为最传统的封严结构,广泛承担着封油封气的作用。目前对篦齿的研究集中于其封气性能,对其封油特性较少涉及。本文对5种不同篦齿封严结构在6个封严压差条件下进行二维数值计算,得到滑油泄漏量,并取其中2种结构进行了实验验证。通过三维数值计算,对篦齿内部起封油作用的封严气流场进行分析,从而得出封严压差、齿数、齿腔大小、甩油齿角度等参数对篦齿封油特性的影响规律。研究发现,由于不同参数会对篦齿内部封严气的压力分布、湍动能耗散、流动路径等产生影响,篦齿的封油效果也将随参数的变化发生规律性变化。5kPa封严压差效果最佳,齿数4相对齿数3泄漏量平均减少6.2%,大齿腔更利于封油,60°甩油齿表现更好。

The seal is an important unit of gas turbine air system,which has a significant effect on gas turbine performance. Labyrinth seal,being the most typical seal form,is widely used for sealing oil and air. The air sealing characteristics were investigated extensively in the last several decades. However,there are few studies on the oil sealing characteristics of labyrinth seal in open literatures. The oil leakage of five different labyrinth seal geometric constructions was acquired under six pressure differentials numerically and two of them were verified experimentally. Then the three-dimensional air flow field of sealing gas which is used to avoid oil leakage was analyzed to obtain the influence of pressure differential,number of teeth,tooth cavity size and angle of oil-swinging tooth upon oil sealing characteristics. As a conclusion,because of the effects on pressure distribution,turbulent kinetic energy loss and flow route,the oil sealing characteristics change regularly. Pressure differential of 5 kPa is optimum,four-tooth labyrinth reduces leakage by 6. 2% than three-tooth labyrinth,bigger tooth cavity is helpful and oil-swinging tooth of 60°acts better.