Fluid system

Abstract

In a fluid system for a gas turbine engine, oil is supplied from an oil tank ( 10 ) by a constant displacement pump ( 12 ) to lubricate engine components ( 18 ). The oil is supplied to the components ( 18 ) via a heat exchanger ( 16 ) in which oil and fuel are placed in direct heat exchange relationship. The flow of oil to the components ( 18 ) is controlled by recirculating a proportion of the oil flow through a bypass ( 20 ). The bypass ( 20 ) regulates the flow of oil to the components ( 18 ) so that the amount of heat transferred to the fuel in the heat exchanger ( 16 ) is controlled. At low engine powers a greater proportion of the oil flows through the bypass ( 20 ) to reduce the oil flow to the components ( 18 ). This reduces the heat transferred to the fuel in the heat exchanger ( 16 ) and so prevents overheating of the fuel.

1 - 14 . (canceled) 
   
   
       15 . A fluid system for an engine which supplies a first and a second fluid to said engine, said fluid system comprising a heat exchanger, a pump, a valve and a pump bypass wherein said first and second fluids are placed in direct heat exchange relationship, said valve being configured to regulate recirculation of a portion of said first fluid through said pump bypass in dependence upon engine running conditions, and thereby controls the temperature of the first fluid in order to control the temperature of said second fluid, wherein the flow of said first fluid to the engine is reduced by said valve to reduce the amount of heat transferred from the first fluid to the second fluid in the heat exchanger wherein said first fluid flows in a closed circuit system. 
   
   
       16 . A fluid system as claimed in  claim 15  in which the flow of the first fluid is reduced by recirculating a proportion of the first fluid flow upstream of the engine. 
   
   
       17 . A fluid system for an engine which supplies a first and a second fluid to said engine, said fluid system comprising a heat exchanger, a pump, a valve and a pump bypass wherein said first and said second fluids are placed in direct heat exchange relationship, said valve being configured to regulate recirculation of a portion of said first fluid through said pump bypass in dependence upon engine running conditions, and thereby controls the temperature of the first fluid in order to control the temperature of said second fluid, said pump being a constant displacement pump, the output of which is regulated by recirculation of a proportion of the first fluid flow upstream of the engine to reduce the flow of said first fluid to the engine and so control the amount of heat transferred from the first fluid to the second fluid in the heat exchanger wherein said first fluid flows in a closed circuit system. 
   
   
       18 . A fluid system for an engine as claimed in  claim 15  in which any of the first fluid in excess of the engines requirements is recirculated. 
   
   
       19 . A fluid system for an engine as claimed in  claim 17  in which the constant displacement pump has an inlet and an outlet and said pump bypass connects the outlet of the pump to the pump inlet through which the proportion of the first fluid is recirculated. 
   
   
       20 . A fluid system for an engine as claimed in  claim 17  in which a proportion of the first fluid is recirculated through the pump bypass that connects an outlet from the heat exchanger to an inlet of the pump. 
   
   
       21 . A fluid system as claimed in  claim 17  in which a filter is provided in flow series between the pump and the heat exchanger. 
   
   
       22 . A fluid system as claimed in  claim 21  in which a proportion of the first fluid is recirculated through the pump bypass that connects an outlet of the filter to an inlet of the pump. 
   
   
       23 . A fluid system for an engine as claimed in  claim 18  in which the valve controls the amount of the first fluid that is recirculated. 
   
   
       24 . A fluid system for an engine as claimed in  claim 23  in which the valve is pressure operated. 
   
   
       25 . A fluid system for an engine as claimed in  claim 23  in which the valve is temperature operated. 
   
   
       26 . A fluid system for an engine as claimed in  claim 17  in which the first fluid is oil and the second fluid is fuel. 
   
   
       27 . A gas turbine engine oil system for regulating heat transferred from a lubrication oil to a fuel and regulate the temperature of the lubrication oil:
 a heat exchanger;   a tank constructed for containing lubrication oil in communication with the heat exchanger;   a first pump constructed and arranged for pumping lubrication oil through engine components and for pumping lubrication oil from the tank through the heat exchanger during operation of the engine;   a fuel tank in communication with the heat exchanger;   a second pump for transferring fuel from the fuel tank to the heat exchanger such that heat can be transferred from the lubrication oil to the fuel during operation of the engine; and   a valve and first pump bypass constructed and arranged to regulate a flow of lubrication oil recirculated though the first pump bypass to the tank instead of the engine components in dependence upon engine operating conditions and thereby control a temperature of the lubrication oil, such that as the flow to the first pump bypass is increased the amount of heat transferred to the fuel is reduced.   
   
   
       28 . A gas turbine engine oil system according to  claim 27 , wherein the valve is pressure operated.