刷式密封泄漏和传热特性影响因素的数值研究

Numerical Investigations on Influence Factors of Leakage Flow and Heat Transfer Characteristics of Brush Seal

关键词:  刷式密封  泄漏特性  传热特性  数值模拟

Key words:  Brush seal  Leakage characteristics  Heat transfer characteristics  Numerical simulation

摘要:

刷式密封作为接触式密封，刷丝与转子之间的摩擦热直接影响到密封封严性能和使用寿命，为向高性能刷式密封的设计提供参考，采用数值求解基于Non-Darcian多孔介质模型的Reynolds-Averaged Navier-Stokes(RANS)和局部非热平衡能量方程并结合有限元方法，建立了考虑刷丝束与转子摩擦热效应的刷式密封泄漏和传热特性分析的数学模型。研究了运行工况转速与压比和后夹板围栏高度对刷式密封泄漏和传热特性的影响规律。结果表明:不考虑刷丝束与转子的摩擦热效应时，刷式密封的泄漏量随转速升高略微降低；考虑摩擦热时，泄漏量因转速升高而显著降低，转速为8kr/min时泄漏量降低到0转速时的69%。刷丝最高温度随转速、压比和围栏高度增大而升高，刷丝束内部温度沿径向降低速率随压比和围栏高度增大而加快。高转速工况下转子产生离心伸长使其与刷丝之间的干涉量增大而影响摩擦热效应。

Abstract:

As a kind of contact sealing technology, the frictional heat generation between bristles and rotor is becoming a major concern for the seal performance and operation life of brush seals. The mathematical model of leakage flow and heat transfer of brush seal analysis with consideration of frictional heat generation between the bristle pack and rotor is established to offer a reference for the design of high performance brush seal. Reynolds-Averaged Navier-Stokes (RANS) based on the Non-Darcian porous medium model and local thermal non-equilibrium energy equation coupled with finite element method is conducted to analyze the leakage flow and heat transfer performance of brush seal. Effects of pressure ratios, rotational speeds and the hence heights of backing plate on the leakage flow and heat transfer characteristics of brush seal are numerically investigated using presented numerical method. The obtained results show that the leakage flow rate of brush seal slightly decreases with increase of the rotational speed without considering the frictional heat generation effect. The leakage flow rate of brush seal significantly decrease with the rotational speed increases with consideration of the frictional heat generation effect. The leakage rate of brush seal at 8kr/min is reduced to 69% of no-rotational case considering the frictional heat generation between the bristle pack and rotor. The highest temperature of the bristle pack increases with the increasing of the pressure ratio, the rotational speed and the fence height. The decrease rate of bristle pack temperature along the radial direction increases with the increasing of the pressure ratio and the fence height. The interference between rotor and bristle pack increases with consideration of the rotor centrifugal growth effect at high rotational speed case. This behavior results in the variation of the frictional heat generation effect of brush seal.