Rotordynamic characteristics of a novel pocket damper seal with self-regulated injection

The conventional fully partitioned pocket damper seal (FPDS) was improved by introducing several nozzles on the first seal tooth, which generates a reverse injection fluid suppressing the cavity flow in the circumferential direction. Computational fluid dynamics (CFD) models of the conventional FPDS and current novel FPDS were established. An infinitesimal theory was employed to identify the rotordynamic coefficient of the FPDS. The influence of nozzle types (negative, straight, positive), inlet/outlet areas, deflection angles (θ) on the rotordynamic performance was comprehensively analyzed. It was found that reducing the circumferential flow in the first seal cavity is crucial for increasing the stability of the FPDS. A negative nozzle angle can restrict the circumferential flow effectively and significantly improve the effective damping and system stability. The crossover frequency for the novel FPDS with θ = −10° is ∼62 Hz, which is much lower than that for the conventional FPDS (∼85 Hz). The increasing inlet/outlet area ratio of the nozzle can also enhance the seal stability. Increasing the negative nozzle angle (θ = none, −10°, −15°, −20°) can effectively increase the effective damping and reduce the crossover frequency from ∼85 Hz to ∼38 Hz. However, the novel FPDS with three kinds of nozzles shows a slight increase (< 2.5 %) in the leakage flow rate compared with the conventional FPDS.