考虑实际气体效应双列螺旋槽干气密封反转性能分析

离心式压缩机在实际生产运行中，因故障停机时会发生反转，要求配置的干气密封具有一定的抗反转能力。针对双列螺旋槽干气密封，选用CO₂作为密封介质。用R-K方程表达实际气体效应，修正气体润滑Reynolds方程，分析在反转情况下，不同转速、膜厚、压差以及反向螺旋槽径向尺寸与正向螺旋槽径向尺寸之比（ε）对密封性能的影响。分别获得了正转、反转和静止3种状态下的端面开启力、泄漏率、气膜刚度和开漏比等密封性能参数。以气膜零刚度反转速度为抗反转能力性能指标，结果表明：CO₂实际气体端面开启力和泄漏率大于理想CO₂气体，而开漏比小于理想气体，分析CO₂气体润滑的双列螺旋槽干气密封性能需要考虑实际气体效应。双列螺旋槽干气密封具有一定的抗反转能力，当反转速度小于气膜零刚度反转速度时，干气密封可以正常操作。以气膜零刚度时的反转速度为最大值，本计算案例最大反转速度为2 524 r/min。

Analysis on the Performance of the Reverse Rotation of Double-spiral Groove Dry Gas Seal Considered Effect of Real Gas Behavior

Centrifugal compressors will be reverse during shutdown due to failure in actual application, so the dry gas seal applied in compressors should possess some ability to the reverse rotation. The double-row spiral groove dry gas seal was taken as an example and the CO₂ gas was used as the sealing medium. The opening force, leakage rate, gas film stiffness and ratio of opening force to leakage rate etc were calculated at the rotation of forward, stop and reverse. The speed of reverse rotation at which the gas film stiffness equals to zero is an important indicator to show the anti-reversal capability of dry gas seal. The results showed that the opening force and leakage rate of CO₂ real gas are greater than those of ideal gas, but the ratio of opening force to leakage rate less than those of ideal gas. When the dry gas seal performance of double-spiral groove lubricated by CO₂ gas is analyzed, it is necessary to consider the real gas effects of CO₂ gas. Double-spiral groove dry gas seals have some reverse rotation capability and the seals will normally operate when the reversal speed is less than that of the gas film zero stiffness. The gas film zero stiffness rotational speed reaches a maximum of 2 524 r/min as to the calculated example.