燃气轮机旋向槽-迷宫密封结构设计与动力学分析

Structure Design and Dynamical Analysis of a Labyrinth Seal with Swirl Slots in Gas Turbine Application

流体密封技术是燃气轮机设计的重要部分之一,被用于减少泄漏和提高燃气轮机的效率。在传统迷宫密封结构的基础上,设计一系列具有旋向槽的密封叶片,对级间射流进行分流和导向,以降低环流速度,从而获得一种动力学性能更优的旋向槽-迷宫密封结构。通过Fluent求解新结构与传统结构的流场,并对其动力学特性与泄露性能进行对比分析。结果表明:旋向槽的添加可以大幅降低工质的环流速度,在齿顶间隙与腔室内分别可获得约44.47%、71.56%的降幅;相比传统迷宫密封,旋向槽-迷宫密封可获得约4.2%的直接刚度提升与33.4%的交叉耦合刚度降低,但同时会带来3.2%的泄漏量提升;旋向槽周向宽度0.6°、深度6 mm、轴向偏转角60°并在周向均布16个时,能获得较好的动力学特性与尽可能低的泄露量。

Fluid seal technology is one of the critical technologies in gas turbine design, which is used to reduce leakage and improve the efficiency of the gas turbine. Based on the traditional labyrinth seal(LS) structure, a series of seal fins with plenty of swirl slots are designed to divert and guide the interstage jet. Extra swirl slots can slow down the circumferential velocity of working gas to obtain a new type of seal with better rotordynamic characteristics, named slot labyrinth seal(SLS). The flow fields of the new structure and the traditional structure are calculated by Fluent. Rotordynamic characteristics and leakage performance of two types of seals are compared and analyzed. The following conclusions are obtained: the addition of SLS can significantly reduce the circumferential velocities of the working medium by 44.47% and 71.56% in the tip clearance and cavity, respectively. Compared with the traditional LS, the SLS can obtain about a 4.2% increase for direct stiffness and about a 33.4% decrease for cross-coupling stiffness. However, it will also increase the leakage by 3.2%. When the circumferential width of the slot width is 0.6 °, the depth is 6mm, the axial deflection angle is 60°, and 16 slots are uniformly distributed in the circumferential direction, better dynamic characteristics and as low leakage as possible can be obtained.