Auxiliary oil system for negative gravity event
A lubrication system includes a bearing compartment. A main reservoir is fluidly connected to the bearing compartment by a main supply passage. A main pump is arranged in the main supply passage configured to provide fluid from the main reservoir to the bearing compartment during a positive gravity condition. A secondary supply passage fluidly connects the main reservoir to at least one segment of the main supply passage, thereby providing fluid from the main reservoir to the bearing compartment during a negative gravity condition. A method of supplying a bearing compartment with fluid includes pumping a fluid from a main reservoir to a bearing compartment through a main supply passage during a positive gravity condition, and providing fluid from the main reservoir to the bearing compartment through a secondary supply passage, fluidly connected to at least one segment of the main supply passage, in response to a negative gravity condition.
1. A lubrication system for a gas turbine engine comprising:
a bearing compartment;
a main reservoir fluidly connected to the bearing compartment by a main supply passage, which includes one or more passage segments therein;
a main pump arranged in the main supply passage configured to draw fluid from the main reservoir and provide the fluid to the bearing compartment during a positive gravity condition;
an auxiliary reservoir;
an auxiliary pump fluidly connected between the auxiliary reservoir and the bearing compartment via an auxiliary passage; and
a secondary supply passage fluidly connecting the main reservoir to at least one segment of the main supply passage, thereby providing fluid from the main reservoir to the bearing compartment during a negative gravity condition, wherein the main reservoir includes upper and lower portions, the main supply passage in fluid communication with the lower portion, and the secondary supply passage in fluid communication with the upper portion, wherein fluid from the main pump is configured to reach the bearing compartment before reaching the auxiliary reservoir.
2. The system according to claim 1 , comprising a first check valve arranged in the secondary supply passage fluidly between the main reservoir and the main supply passage.
3. The system according to claim 2 , comprising a bleed passage fluidly connected to the secondary passage and configured to bypass the first check valve.
4. The system according to claim 2 , wherein the main reservoir includes a vent having a pressure valve configured to maintain a desired pressure in the main reservoir and open the first check valve in the negative gravity condition.
5. The system according to claim 4 , wherein the desired pressure is at least 20 psia (137.90 kPa).
6. The system according to claim 2 , comprising a second check valve in the main supply passage and arranged upstream from an intersection of the main supply passage with the secondary supply passage.
7. The system according to claim 1 , wherein the bearing compartment includes a sump, and a scavenge pump fluidly connecting the sump to the main reservoir.
8. The system according to claim 1 , comprising a shuttle valve interconnecting the auxiliary passage and the main supply passage and arranged upstream from the auxiliary and main pumps.
9. The system according to claim 1 , comprising a check valve provided in the main reservoir movable in response to the positive and negative gravity conditions.
10. The system according to claim 1 , wherein the main supply passage includes an ejector fluidly connected to the secondary supply passage at an ejector throat.