Labyrinth seal works

Labyrinth seals sealing principle, we must first analyze the gas flow in a sealed state. When the gas flow through a gap seal teeth and the shaft surface, the air flow by a throttle, the airflow pressure and temperature drop, while the flow rate increased.

The air flow through the gap after the larger cavity formed by the two seal teeth. Gas content in the cavity of the plot suddenly increases, the formation of a strong vortex flow velocity is almost zero in the volume ratio of the clearance volume of the cavity, the kinetic energy into heat due to vortex all, heating the gas itself, so the gas in this cavity , the temperature back to the throttle, but the pressure has picked up very little pressure, can be considered to maintain flows through the gap. Each gas through a gap and then a larger cavity, air flow by a throttle and expansion of the role of the vortex loss of energy, gas pressure is falling, the specific volume and velocity increase.

Airflow after sealing the tooth, its pressure is reduced from p1 to p2, as the pressure decreases, the gas leakage is reduced. By the above process, the labyrinth seal is the use of increased local loss in order to consume their energy to prevent leak out of the airflow, therefore, labyrinth seals belong to the flow resistance, non-contact dynamic seal.

It can be seen from the above analysis, the smaller the seal gap sealing of teeth is more, the better the sealing effect, the seal of teeth to a certain number, however, improve the effect is no longer so obvious.

Therefore, the sealing of teeth should not be too much, the interstage around the impeller seal, generally located 3 to 6 teeth, shaft seal located 6 to 35 teeth. Tooth tip clearance is too large, poor sealing effect, if the gap is too small, would lead to friction of the rotor and the seal between the teeth in the rotor vibration or slightly curved, so the tooth tip clearance is also suitable.