System for reducing oil consumption in gas turbine engines

Abstract

A system for reducing oil usage from a sump in a gas turbine engine. Two sources of oil usage, which usage includes leakage and consumption, have been identified: (1) during idle, leakage of oil from an oil sump through seals and (2) during high-power operation, consumption of oil entrained in vent air exiting from the sump. At idle, the invention reduces pressure in the sump, to thereby increase airflow across the seals into the sump, to inhibit the oil leakage across the seals. At high power operation, the pressure reduction is terminated, but flow exiting the vent is artificially restricted.

1 - 4 . (canceled) 
   
   
       5 . Method, comprising:
 a) ascertaining amount of airflow across seals which seal a lubrication sump; and   b) b) maintaining said airflow above a predetermined minimum.   
   
   
       6 . Method according to  claim 5 , wherein said airflow is maintained above said minimum by activating an eductor which draws air from the sump. 
   
   
       7 . Method according to  claim 5 , wherein the sump is contained in a gas turbine engine. 
   
   
       8 . Method according to  claim 5 , and further comprising the step of
 c) recovering oil scavenged from the sump and delivering the oil recovered to a bearing in a gas turbine engine.   
   
   
       9 . Method, comprising:
 a) in a gas turbine engine, maintaining an eductor in fluid communication with a vent of a lubrication sump; and   b) using the eductor to maintain fluid flow through the vent above a predetermined minimum.   
   
   
       10 . Method according to  claim 9 , wherein the operation of paragraph (b) occurs at idle speeds. 
   
   
       11 . Method according to  claim 9 , and further comprising:
 c) measuring a parameter which makes an indication of air flow which would exist in the vent without the eductor and, if the indication exceeds a floor, de-activating the eductor.   
   
   
       12 . Method of operating a gas turbine engine, comprising:
 a) maintaining an eductor, having a flow restrictor therein, in fluid communication with a vent of a lubrication sump;   b) when engine speed is below a floor, injecting a jet of air into the eductor, to increase flow through the vent, to decrease pressure in the sump; and   c) when engine speed is above a threshold,   i) terminating the jet of air, and   ii) utilizing the flow restrictor to limit flow through the vent.   
   
   
       13 . Apparatus, comprising:
 a) a gas turbine engine;   b) a lubrication sump in the engine which vents air to an exit; and   b) first means for increasing flow through the vent above normal during idle operation.   
   
   
       14 . Apparatus according to  claim 13 , and further comprising:
 c) second means for de-activating the first means at high-power operation of the engine.   
   
   
       15 . Apparatus according to  claim 14 , and further comprising:
 d) means for restricting flow to a level below normal at said high-power operation.   
   
   
       16 - 25 . (canceled)