Abstract
Seals are considered one of the most important flow elements in turbomachinery applications. The most traditional and widely known seal is the labyrinth seal but in recent years other types like the brush or carbon seals were introduced since they considerably reduce the sealing air consumption. When seals are used for sealing of aero engine bearing chambers they are subjected to high “bombardment” through oil particles which are present in the bearing chamber. These particles mainly result from the bearings as a consequence of the high rotational speeds. Particularly when carbon or brush seals are used, problems with carbon formation (coking) may arise when oil gets trapped in the very tight gap of these seals. In order to prevent oil migration into the turbomachinery, particularly when the pressure difference over a seal is small or even negligible, significant improvement can be achieved through the introduction of so called windback seals. This seal has a row of static helical teeth (thread) and below this thread a scalloped or smooth shaft section is rotating. Depending on the application, a windback seal can be used alone or as a combination with another seal (carbon, brush or labyrinth seal). A CFD analysis carried out with ANSYS CFX version 11 is presented in this paper with the aim to investigate this seal type. The simulations were performed by assuming a two-phase flow of air and oil in the bearing compartment. Design parameters like seal clearance, thread size, scallop width, were investigated at different operating conditions.
Highlights
In modern aero-engines, the lubrication system holds a key role due to the demand for high safety and reliability standards
The targets set through this paperofare aswindback follows: seal and particle tracing in order to evaluate flow evaluation as a function of the operating conditions for different windback seal designs the ability of the seal to repulse oil
The aim of this work was to investigate the flow through windback seals and their ability to repulse oilofwhich an adjacent compartment lowtheir pressure
Summary
In modern aero-engines, the lubrication system holds a key role due to the demand for high safety and reliability standards. Oil migration into the compressor will contaminate the cabin air whereas oil migration into the turbine may ignite and cause component failure For this reason, additional precaution measures are considered during the design phase in order to make oil migration into the turbo machinery as remote as possible. Additional precaution measures are considered during the design phase in order to make oil migration into the turbo machinery as remote as possible Such measures are for example drains attached to the bearing chamber and windback seals. [2] has numerically and experimentally investigated in his PhD thesis the impact of different design parameters on the performance of windback seals for compressor applications He based his work on the same operating conditions as in [1]. This work has been inspired by engine projects which have involved the particular windback seal design
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