Gas turbine engine labyrinth seal modeling and optimization considering the strength properties

Aeronautical and Space-Rocket Engineering


DOI: 10.34759/vst-2022-2-107-117

Аuthors

Androsovich I. V.

PJSC UAC Sukhoi Design Bureau, 23A, Polikarpova str., Moscow, 125284, Russia

e-mail: irishapd-35@mail.ru

Abstract

Promising engines parameters improving can be achieved primarily by significant parameters upgrading of the units and their components, such as labyrinth seals. The gas turbine engine efficiency depends on air leaks in both compressor and turbine, for which various types of seals are being used in the cooling and bleed air system. Labyrinth seals are the most common in aircraft engines. The state-of-the-art labyrinth seals are of high quality and their further improvement requires application of computer aided modeling and optimization.

The author conducted gas dynamic and strength computing of the labyrinth seal operation, and performed the labyrinth seal geometry optimization with account for the strength properties. The article demonstrates the optimization technique, which may be applied while labyrinth seal design to ensure minimum air consumption and meeting the strength criteria.

The gas flow in the labyrinth seal computing was being performed with the 1.1 pressure ratio at the rated rotation frequency of 16,000 rpm. Analysis of the circumferential speed impact on the labyrinth seal operation was performed. The circumferential speed impact on the air consumption was up to 3%.

With the circumferential velocity increase, the absolute value of the velocity in the seal gap increases, and the axial component decreases, which results in the air flow decrease through the seal. Prior to optimization, the total mass air consumption through the labyrinth seal was 8.46 g/s.

The strength calculation used boundary conditions with the pressure field on the labyrinth seal surface, obtained as the result of the gas-dynamic computation of the flow in the channel and rotation frequency. The following parameters were being calculated: total deformation, von-Mises equivalent stress, and safety margin.

As the result of optimization, the space between the ridges increases. Vortex structures emerge in the space between the ridges, caused by the action of viscous forces between the flow core and the gas between the ridges, sufficient space between the ridges ensures the vortex structures unhampered formation. More intensive vortex structures ensure, in their turn, more intensive energy dissipation, which leads to the air consumption reduction in the labyrinth seal gap. Besides this, emerging of the radial component of the velocity prior to the top of each ridge leads to the air consumption reduction as well.

After optimization, the air consumption reduction through the labyrinth seal by 16,8% was achieved at the rated speed of 16,000 rpm. Deformation and strength margin criteria were met as well. Deformation decreased by 6 %, Mises stresses decreased by 13,66 %, and the safety margin of the labyrinth seal increased by 16,13 %.

The presented calculation technique may be applied in solving problems of labyrinth seal optimization for searching for the labyrinth seal configuration ensuring minimum air consumption and meeting the strength criteria.

Keywords:

labyrinth seal, computational gas dynamics (CFD), strength properties, labyrinth seal optimization, pressure ratio, air leakage

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