Turbomachine

A method of reducing oil leakage in a turbomachine comprising a unitary housing defining a bearing cavity, a turbine chamber and an integral heat shield, the bearing cavity and turbine chamber being separated by a first wall;

• a turbine wheel mounted to a shaft for rotation within said turbine chamber about a machine axis;
• the heat shield disposed between the first wall and the turbine wheel, a heat shield cavity being defined between the first wall and the heat shield;
• the shaft extending from the turbine chamber into the bearing cavity through a passage defined at least in part by a first aperture in said first wall and a second aperture in the heat shield, the shaft being mounted for rotation on a bearing assembly provided in the bearing cavity;
• a first seal between the shaft and said first aperture;
• a second channel between the heat shield cavity and said passage, the second channel opening to said passage on the opposite side of said first seal to said bearing assembly;
• and
• a method comprising supplying pressurised air to said heat shield cavity to raise the pressure within the heat shield cavity and thereby raise the pressure within the passage on the opposite side of said first seal to said bearing assembly.

A method of manufacturing a turbomachine comprising:

• forming a unitary housing defining an integral bearing cavity, an integral turbine chamber and an integral heat shield as a single component, the bearing cavity and turbine chamber being separated by a first wall;
• mounting a turbine wheel to a shaft for rotation within said turbine chamber about a machine axis;
• forming the unitary housing so that the heat shield is disposed between the first wall and the turbine wheel and so that a heat shield cavity is defined between the first wall and the heat shield;
• the shaft assembled with the housing so that the shaft extends from the turbine chamber into the bearing cavity through a passage defined at least in part by a first aperture in said first wall and a second aperture in the heat shield, the shaft being mounted for rotation on a bearing assembly provided in the bearing cavity;
• forming a first seal between the shaft and said first aperture;
• forming the unitary housing so that it defines a first gas channel communicating with the heat shield cavity for connection to a pressure source for raising pressure within the heat shield cavity;
• forming a second channel between the heat shield cavity and said passage, the second channel opening to said passage on the opposite side of said first seal to said bearing assembly;
• and
• forming a second seal between the shaft and said second aperture.