新型径向环形组合密封增效减振理论与关键技术研究

The project presents a new kind of radial annular seal theory with higher efficiency and lower vibration. It includes four major ideas, which are resistance improvement with large turbulence, reduction of seal gap, reduction of circular velocity and improvement of cylinder cavity. The honeycomb disk combined with the circular annular seal is installed on shaft end or blade tip to change the leakage flow from the axial direction to the radial direction. Spiral flow is disappeared due to the resistance of honetcomb disk. Flow near the two sides of the disk is opposite and seal force is counteracted partially. Flow induced force in seal will be reduced using the above mentioned two methods. The compressed air is imported into the adjustment cavity to control seal gap automatically based on the measured expansion difference value. Four turns in the seal and the combination of honeycomb disk and radial annular seal will enhance votex and flow resistance in the seal.Seal efficiency is improved. The improved test method for seal dynamic coefficients identification will be set up considering disadvantages of the traditional identification method in the frequency domain. We will use cylinder resonance to enlarge the influence of seal force on vibration. Multiple point exciting and multiple point influence coefficients method of rotor dynamics is used here to improve test accuracy and to consider the tilting motion of cylinder ,the coupling between the vertical vibration and the horizontal vibration. Synchronous excition method using unbalance force is used to identify seal dynamic coefficients. Seal fluid field, expansion coefficient, temperature rise and dynamic coefficients are calculated and analyzed using CFD software. The project will also set up seal leakage calculation equation using thermal dynamics theory considering the influence of the changed flow area along seal leakage path and the influence of centrifugal force effect. We will evaluated seal characteristics and compared with other kinds of seals based on the above mentioned theoretical and experimental research results. The special solvement method considering the disadvantages of the radial annular seal will be put forward. The project will use this new kind of seal to control leakage of shaft end and blade tip.

提出径向环形密封增效减振理论，包含湍流增阻、减小间隙、减小周向流速、改进环形腔室理念。借鉴推力轴承思想，在轴上或叶尖处设置蜂窝盘并安装环形密封，将泄漏由轴向改为径向。流体被蜂窝盘阻挡后消除了螺旋流动，蜂窝盘两侧气流方向相反，这两条措施可以减小气流力。调节腔内引入压缩空气，实现间隙自适应调整。密封内增加4个直角转弯，采取蜂窝盘和环形齿组合模式，预计能增大涡旋和流动阻力，提高密封效果。研究密封动力特性改进试验方法。利用气缸共振放大气流力影响，引入转子动力学多测点影响系数法考虑气缸偏摆、垂直/水平振动耦合等问题，提高识别精度，采用不平衡激励法辨识动力特性系数。利用CFD计算密封流场、扩散系数、温升和动力系数，应用热力学理论，考虑变截面和离心力影响，建立径向环形密封泄漏计算公式。在上述基础上，客观评价径向环型组合密封增效减振性能。针对其缺点提出有效解决措施。将径向环形密封应用于叶尖和轴端泄漏控制。

本项目建立了密封内流场三维CFD计算模型，分析了进出口压比、偏心率、转速等对密封性能的影响，指出流体的螺旋形流动会使最高压力点偏离最小间隙，形成与转子偏心方向垂直的切向气流力，诱发转子失稳。在此基础上，提出径向环形密封增效减振理论，通过隔断螺旋形流动减小气流力。应用热力学理论，考虑变截面和离心力影响，建立了径向环形密封泄漏计算模型。分析了径向环形密封内部两种不同形式的流动特性，并对其结构进行了优化。将径向环形密封应用于透平机械叶顶及轴端处，建立了包含动叶片通流部分和叶顶间隙密封部分的三维偏心计算模型，分析了密封泄漏、激振力及对其下游主流的影响。研究表明，径向环形叶顶间隙密封能够有效减少叶顶间隙处的流体泄漏和激振力，减小泄漏流体与主流的混流作用，降低混合流动带来的损失，也可以减小轴端密封泄漏。在转子-轴承-密封系统试验台上研究了密封特性改进试验方法，并开展了梳齿密封和径向环形密封性能试验研究。设计了以气缸为研究对象的气流力及刚度系数测试方法，试验验证了切向气流力的存在，研究了压比、转速、密封间隙等对泄漏量和气流力的影响，并观察到了气流力导致系统提前失稳现象。试验发现轴承对系统稳定性影响较大，选择合适的轴承型式可以补偿气流力对系统稳定性的不利影响。理论和试验研究表明，径向环形密封泄漏低，气流力小，耐磨性强，具有较强的增效减振性能。

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