Sealing and purging arrangement for a main bearing region

Apparatus for sealing and purging a bearing region includes a bearing housing having at least one hole that allows a flow of air to flow through the at least one hole, and at least one bearing seal that allows the flow of air to flow through the at least one bearing seal, thereby creating a pressure difference across the bearing seal. The apparatus also includes an air directional device having at least a portion of the flow of air to flow adjacent to the air directional device, and a pair of components having a gap between the pair of components that allows the at least a portion of the flow of air to flow through the gap, thereby purging the gap.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to main bearings and, more particularly, to a sealing and purging arrangement at a main bearing region.

A gas turbine includes a main rotor that requires sealing of the main bearing to prevent leakage of the bearing oil in the bearing housing or compartment. Such leakage may cause operational issues for the gas turbine. It is known to use labyrinth seals in the sealing of the bearing housing. However, these labyrinth seals oftentimes pose added cost and reliability issues.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, apparatus for sealing and purging a bearing region includes a bearing housing having at least one hole that allows a flow of air to flow through the at least one hole, and at least one bearing seal that allows the flow of air to flow through the at least one bearing seal, thereby creating a pressure difference across the bearing seal. The apparatus also includes an air directional device having at least a portion of the flow of air to flow adjacent to the air directional device, and a pair of components having a gap between the pair of components that allows the at least a portion of the flow of air to flow through the gap, thereby purging the gap.

According to another aspect of the invention, apparatus for sealing and purging a bearing region includes a bearing housing having at least one hole that allows a flow of air to flow through the at least one hole, and at least one bearing seal that allows the flow of air to flow through the at least one bearing seal, thereby creating a pressure difference across the bearing seal. The apparatus also includes an air directional device having at least a portion of the flow of air to flow adjacent to the air directional device, and a rotor and stator having a gap between the rotor and the stator that allows the at least a portion of the flow of air to flow through the gap, thereby purging the gap.

According to yet another aspect of the invention, a method of sealing a bearing housing containing oil includes routing a flow of air through one or more holes located in the bearing housing, and routing the flow of air through at least one bearing seal, thereby creating a pressure difference across the bearing seal to seal the oil within the bearing housing. The method also includes routing at least a portion of the flow of air adjacent to an air directional device, and routing the at least a portion of the flow of air through a gap between a rotor and a stator, thereby purging the gap.

DETAILED DESCRIPTION OF THE INVENTION

InFIG. 1is shown a portion of a gas turbine10, specifically, at a main or #1 bearing region of the gas turbine10, in which embodiments of the present invention may be located. Embodiments of the present invention are not limited to a bearing region of a gas turbine. Embodiments of the present invention may be located in devices other than a gas turbine, wherein these other devices include a bearing region to be sealed in accordance with embodiments of the present invention. The main bearing region of the gas turbine10may include a rotor14, a bearing housing16and bearing seals18. Also included may be an inlet guide vane (IGV) shroud24, a forward stub shaft (FSS)30, and a gap or cavity32between the rotor14and a stator. In embodiments of the present invention located in devices other than a gas turbine, the rotor14and stator may comprise other components in which a gap is located between these other components. A line with an arrowhead34shows a flow of bearing oil from the bearing housing16to a sump. Embodiments of the present invention effectively seal the bearing oil within the bearing housing16and prevent any leakage from the bearing housing16, including into a main airflow path, which may cause issues with operation of the gas turbine10. The one or more bearings within the bearing housing16may comprise vacuum-type bearings for the rotor14, which are those where the bearing oil within the housing16is drained due to suction. That is, the sump is maintained at a pressure lower than the atmospheric pressure.

InFIG. 2is shown a more detailed cross section the main or #1 bearing portion of the gas turbine10in which embodiments of the present invention may be located. In an embodiment, a flow of ambient air as indicated by the line with an arrowhead40may come from the surrounding atmosphere of the gas turbine10. The flow of ambient air40may then pass through a load tunnel compartment of the gas turbine10before getting into the main or #1 bearing region. There, the flow of ambient air40passes through holes42,44formed in the bearing housing16, in accordance with an embodiment of the present invention. The holes42,44may be circular or any other suitable shape. The ambient airflow40then passes through the bearing seals18, and a portion of the airflow40passes adjacent to a cover plate46or other suitable air directional device, according to an embodiment of the present invention. The ambient air flow40passing through the bearing seals18creates a relatively high pressure difference across the seals18, which prevents the oil from leaking out from the bearing housing16.

The cover plate46may be fitted into a groove48formed in the IGV shroud24for attachment purposes. Other suitable methods of attaching the cover plate46in the desired location may be utilized. A portion of the cover plate46may be located adjacent to or abutting the bearing housing16. The cover plate46may comprise nodular cast iron, sheet metal, or other suitable material. The flow of ambient air40then passes through the rotor-stator gap or cavity32before entering a main airflow path50. The cover plate46blocks the flow of ambient air from flowing directly to the gap32between the rotor and stator.

In embodiments of the present invention, a flow of ambient air40is routed through the main or #1 bearing seals18and then through the rotor-stator (RO) gap32. This provides for relatively effective #1 bearing oil sealing (i.e., primarily by the forward portion of the seals18inFIG. 2), thereby achieving a reduction in the amount of oil leakage from the bearing housing16. In addition, the routing of the ambient air flow40in accordance with embodiments of the present invention reduces the amount of air leakage flow from the ambient air entering the holes42,44in the bearing housing16and passing through the rotor-stator gap32and into the main airflow path50. A greater amount of air leakage flow passing through the rotor-stator gap32and into the main airflow path50may disturb the flow of air in the main airflow path50. At the same time, the reduced amount of the flow of air40through the rotor-stator gap32and into the main airflow path50is still high enough to allow for purging of the rotor-stator gap or cavity32, which is a desirable effect.

Embodiments of the invention provide for one or more holes42,44in the bearing housing16. Also provided is a cover plate46. This configuration of the holes42,44ensures a relatively effective seal of the bearing #1 oil within the housing16. Without the cover plate46, a forward stub shaft (FSS) labyrinth seal52(FIG. 1) is needed for restricting the flow to the rotor-stator gap32. Adding a cover plate46eliminates the need for the use of a FSS labyrinth seal52, with the bearing seal18aft portion taking care of any flow restriction. Embodiments of the invention provide for a relatively more effective oil sealing with a relatively higher delta P (i.e., higher air pressure difference) across the bearing seals18at the #1 bearing aft end. Also, the overall oil sealing and air purging system of embodiments of the present invention is relatively more reliable, since the rotor surface is closed. As such, the necessity for use of the forward stub shaft (FSS) labyrinth seal can be eliminated, thereby providing for cost saving and improved reliability. Further, the amount of air flow into the main flow path50through the rotor-stator (RO) gap32may be reduced by a relatively significant amount at any given flow path pressure condition, thereby meeting certain aerodynamic requirements.