Output details

A Seal Assembly

The award-winning paper by Curtis et.al. [1], describes experiments demonstrating the benefit of using fluid jets or ‘air curtains’ to reduce leakage flow in turbomachinery seals. CFD calculations by Hogg & Gomez-Ruiz [2] on leakage flow through simple uniform channels, showed that it is not possible to achieve a net leakage reduction (including the jet) with jets orientated normal to the channel flow. Inclining the jet against the channel flow was shown to result in only modest flow reductions.

Auld et. al. [3] used CFD to develop a fluid jet seal to reduce rotor tip leakage in a single stage axial flow turbine. The seal geometry had a uniform annular cavity between the rotor tip shroud and the turbine casing, into which the fluid jet entered. The tip seal geometry also featured axial restrictions at inlet and exit from the cavity. CFD calculations showed 50% net leakage flow reduction compared to a standard seal design. The results revealed a large drop in pressure across the jet, needed to turn the jet fluid into it direction of the over-tip leakage flow. The pressure on the exit flow side of the jet is therefore reduced which decreases the pressure drop across the axial exit restriction. All of the leakage flow must pass through the exit restriction and so the over-tip flow is reduced by the presence of the jet.

This patent invention is the use of fluid jets in combination with any type of aerodynamics seal, to reduce the pressure drop across the aerodynamic seal in the manner described above, bringing about a decrease in leakage flow.

References

1. Curtis et al., ASME Turbo Expo 2009, GT2009-59411.

2. Hogg & Gomez-Ruiz, ASME Turbo Expo 2011, GT2011-45353.

3. Auld et al, ASME Turbo Expo 2013, GT2013-94198.