Oil recovery system

Abstract

An oil recovery system arranged to recover lubricating oil in a gas turbine engine, the oil recovery system comprising: a separator arranged to extract lubricating oil from a mixture of lubricating oil and air; an oil tank arranged to collect lubricating oil extracted from the mixture; and an exit mast arranged to vent air extracted from the mixture overboard from a core of the engine, wherein the exit mast comprises one or more openings for venting air from the separator; and wherein the one or more openings faces at least partially upstream relative to a direction of airflow through the gas turbine engine, such that the air is vented in the upstream direction, and a dynamic head of any airflow pressurises the oil tank, via the exit mast.

We claim: 
     
         1 . An oil recovery system arranged to recover lubricating oil in a gas turbine engine, the oil recovery system comprising:
 a separator arranged to extract lubricating oil from a mixture of lubricating oil and air;   an oil tank arranged to collect lubricating oil extracted from the mixture; and   an exit mast arranged to vent air extracted from the mixture overboard from a core of the engine,
 wherein the exit mast comprises one or more openings for venting air from the separator; and wherein the one or more openings faces at least partially upstream relative to a direction of airflow through the gas turbine engine, such that the air is vented in the upstream direction, and a dynamic head of any airflow pressurises the oil tank, via the exit mast. 
   
     
     
         2 . The oil recovery system as claimed in  claim 1 , wherein the exit mast is arranged to vent air into a bypass duct of the gas turbine engine. 
     
     
         3 . The oil recovery system as claimed in  claim 1 , comprising:
 a pump for circulating lubricating oil from the oil tank to a lubricating chamber for lubricating a part of the gas turbine engine,
 wherein an inlet pressure of the pump is at least in part dependent on a pressure of the oil tank. 
   
     
     
         4 . The oil recovery system as claimed in  claim 1 , comprising:
 a pump for circulating the mixture of lubricating oil and air from a lubricating chamber for lubricating a part of the gas turbine engine to the separator.   
     
     
         5 . The oil recovery system as claimed in  claim 1 , wherein the separator outputs the lubricating oil to the tank, and a second mixture of lubricating oil and air, with reduced concentration of oil; and wherein the oil recovery system further includes:
 an oil breather, arranged to extract further lubricating oil from the second mixture of lubricating oil and air, and to provide the further lubricating oil to the oil tank, and the air with any remaining oil content to the exit mast.   
     
     
         6 . The oil recovery system as claimed in  claim 1 , wherein the exit mast is in direct fluid communication with the separator or oil tank. 
     
     
         7 . The oil recovery system as claimed in  claim 1 , comprising one or more conduits arranged between the lubricating chamber and the exit mast, wherein the conduits do not include any pressure control valve or pressure control constriction. 
     
     
         8 . The oil recovery system as claimed in  claim 1 , wherein:
 each of the one or more openings has an opening axis extending perpendicular to a plane defined be the opening;   each of the one or more openings has an opening angle defined between the opening axis and the direction of airflow;   the opening angle can vary between 0 degrees and 90 degrees, such that the pressure of the oil tank is at least partially dependent on the opening angle.   
     
     
         9 . A gas turbine engine for an aircraft comprising:
 an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;   a fan located upstream of the engine core, the fan comprising a plurality of fan blades;   one or more lubricating chambers arranged around the core shaft, each lubricating chamber comprising seals between a housing of the chamber and the core shaft;   an air supply system arranged to direct pressurised air at the seals, in order to prevent escape of lubricating oil from the lubricating chamber, wherein the air mixes with the lubricating oil in the lubricating chamber; and   an oil recovery system as claimed in  claim 1 , arranged to recover lubricating oil from the oil and air mixed in the lubricating chamber.   
     
     
         10 . The gas turbine engine as claimed in  claim 9 , wherein the seals comprise a seal selected from: contacting carbon seals, air riding carbon seals, and brush seals. 
     
     
         11 . The gas turbine engine as claimed in  claim 9 , wherein:
 the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft;   the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor;   the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft; and   the air supply system is arranged to draw air from upstream of the first compressor.   
     
     
         12 . The gas turbine engine as claimed in  claim 9 , wherein the oil recovery system is arranged to circulate lubricating oil from the oil tank to the lubricating chamber. 
     
     
         13 . The gas turbine engine as claimed in  claim 9 , wherein:
 the gas turbine engine includes a bypass duct arranged around the engine core;   the bypass duct includes radially extending support structures and/or guide vanes; and   wherein the exit mast is arranged in one of the support structures and/or guide vanes, and the support structures and/or guide vane includes an opening facing downstream into a bypass airflow, to vent air from the exit mast into the bypass duct.   
     
     
         14 . The gas turbine engine as claimed in  claim 9 , wherein at least one of the lubricating chambers comprises a bearing chamber. 
     
     
         15 . The gas turbine engine as claimed in  claim 9 , further comprising:
 a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft,
 wherein at least one of the lubricating chambers comprises the gearbox. 
   
     
     
         16 . The gas turbine engine as claimed in  claim 9 , wherein the oil and air mixture from the lubricating chamber is exhausted only to the separator or oil tank. 
     
     
         17 . A method of pressuring an oil tank for collecting lubricating oil from a mixture of oil and air, in a gas turbine engine, the method comprising:
 separating a mixture of oil and air;   collecting the lubricating oil in an oil tank; and   venting the air through an exit mast having an opening facing at least partially upstream into an air flow through the gas turbine engine, such that a dynamic head of any airflow through the engine pressurises the oil tank, via the exit mast.   
     
     
         18 . The method as claimed in  claim 17 , wherein the tank is pressurised without a pressure control valve or pressure control constriction.