Brush Seal for Turbine
Publication Date: 2005-Jul-07
The IP.com Prior Art Database
A new design for brush seals intended for a turbine to reduce leakage flow between blade tips and adjacent components comprises a front plate of the brush seal having an inner diameter modified to close to the inner diameter of the backing ring that supports the bristle pack on the downstream side. In addition, the front plate comprises a chamfer on its downstream side. A further new design for brush seals comprises devices such as a honeycomb structure attached to the front plate. By these designs the risk of damage to the seal due to swirl in the leakage flow is reduced.
Brush Seal for Turbine
Brush seals are used in turbines and other devices for the reduction of leakage flow between stationary and rotating components, for example in a turbine between the blade tip shroud and the casing or rotor. The brush seals are typically mounted in a blade tip seal cavity of the casing or rotor and extend toward the blade tip shroud. They comprise a bristle pack mounted between a front plate and a back support plate or backing ring. Depending on operating conditions in the turbine, damage can occur to the brush seal such that its sealing effectiveness diminishes and turbine efficiency can be reduced. It has been found that swirl in the inlet flow approaching the brush seal causes the bristles on the upstream side of the bristle pack facing the inlet flow to lift away from the bristle pack in the direction against the leakage flow. Such lifted-off bristles are exposed to a drag force from the swirling upstream flow. This can give rise to mechanical stress levels within the bristles large enough to cause them to fail (usually due to fatigue) and cause damage to the brush seal as a whole.
In view of the bristle failure mechanism described above, two new concepts for brush seal designs are presented, which provide a brush seal with maximised shielding in order to minimise the risk of bristle damage due to swirl in the approaching leakage flow.
In the first design, illustrated in figure 1, the brush seal is modified by a front plate having an inner diameter modified to close to the diameter of the backing ring or back support plate that supports the bristle pack on the downstream side. By this modification only a short length of the bristles is exposed to the drag forces of the swirl and lift-off, and resulting stresses of the bristles are reduced.
Additionally, the front plate of the brush seal is provided with a chamfer o...