Abstract:

A new-type of cylindrical spiral dry gas seal was employed in gas turbine with large vibration. In order to investigate the performance of the cylindrical gas seal, the approximate analytic solution of the gas pressure was obtained by the methods of PH linearization and iteration, which was deduced from the steady micro-scale cylindrical Reynolds equation with the slip boundary conditions. According to the related formulas, the dimensionless buoyancy, leakage and friction torque of cylindrical spiral gas film were analyzed with the different operation conditions and groove structural parameters. Furthermore, part of the optimized structural parameters of spiral groove was proposed based on the comparison of the steady characteristics. It is indicated that the influence of pressure difference on the steady characteristic is more significant than the eccentricity ratio. The influence of the groove number(n) on the buoyancy is not obvious. The friction torque increases with the increase of the groove number but the leakage decreases to a stable value when n=12. The buoyancy decreases with the increase of the groove depth, which is opposite to the friction torque and leakage. With the increase of the seal width(L), the leakage get stable at L=0.035 m. The increase of the spiral angle leads to the decrease of the buoyancy but the increase of the friction torque and leakage. The friction torque increases with the structural parameters under the pressure difference. The increase of the groove number leads to the decrease of the buoyancy, which is opposite to the influence of groove depth. The buoyancy decreases at L=0.04 m then increases with the increase of the seal width, which is opposite to the influence of spiral angle. The increase of the groove number and seal width lead to the robust decrease of the leakage. Optimized structural parameters are obtained: n=12-18, L=0.03-0.045 m, a=40°-50°.

Key words: cylindrical spiral groove seal, micro-scale, working condition, structural parameters, steady characteristics

摘要：

针对燃气轮机转子振动较大的特点，提出一种新型柱面螺旋槽气膜密封。利用考虑滑移边界条件下的微尺度效应稳态柱面雷诺方程，求解柱面气膜的压力的近似解析解，获得柱面螺旋槽气膜量纲1浮升力、泄漏量以及摩擦转矩，并讨论了工况参数和螺旋槽结构参数对稳态性能的影响。综合考虑参数对稳态特性的影响，提出优化结构参数。结果表明：密封压差对稳态特性的影响要远大于偏心率。在不同的偏心率下，螺旋槽槽数对浮升力的影响不明显，随着槽数的增加，摩擦转矩升高，泄漏量降低并在槽数n=12左右趋于稳定；随着槽深的增大，浮升力呈下降趋势，摩擦转矩和泄漏量相应增大；随着密封宽度增大，浮升力呈上升趋势，但偏心率不同，上升幅度不同；泄漏量在密封宽度L=0.035 m处基本稳定。螺旋角的增大导致了浮升力的下降，摩擦转矩和泄漏量呈上升趋势。在密封压差的作用下，摩擦转矩随着4种结构参数的增大而上升。槽数增大导致浮升力下降，与槽深的影响刚好相反。随着密封宽度的增加浮升力先降低后升高，与螺旋角的影响刚好相反。槽数和密封宽度的增加导致泄漏量快速下降至稳定值。提出优化的结构参数如下：槽数n=12～18，密封宽度L=0.03～0.045 m，螺旋角a=40°～50°。

关键词: 柱面螺旋槽密封, 微尺度, 工况, 结构参数, 稳态特性