Influence of shunt injection on dynamic characteristics of labyrinth seals and its effectiveness
The influences of adding or not adding the shunt injection with different preswirl ratios on the pressure,the circumferential flow velocity,the growth rate of the circumferential swirling flow and rotordynamic characteristics coefficients in each seal cavity were compared and analyzed.The effec-tiveness of the shunt injection was quantitatively analyzed and evaluated.Studies showed that the shunt injection device had a strong inhibitory effect on the circumferential flow of the seal,and also a different influence on the pressure in each cavity,with a more obvious influence on the pressure in C3—C6.The growth rate of the circumferential swirling flow was introduced to measure the effect of the shunt injection.With the addition of shunt injection,the circumferential swirling flow growth rate for labyrinth seal was reduced along the direction of leakage to C8,and slightly rebounded at C9.The labyrinth seal without shunt injection remained largely unchanged.The shunt injection increased the direct damping of C3—C6,decreased the cross-coupled stiffness of each cavity,thus improving the effect damping of each cavity,and enhancing the system stability.The preswirl ratio influenced the direct damping of C1—C2.The shunt injection made the cross-coupled stiffness of each cavity decrease more at the high preswirl ratio.The effect damping was less affected by the preswirl ratio,thus the shunt injection had a better suppression effect on inlet the positive preswirl ratio.
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