Turbomachine Lubrication System with an Anti-Siphon Valve for Windmilling

Abstract

The present application relates an oil feed system for a turbomachine having a tank designed to contain a volume of oil, a pump designed to suck the oil from the tank and discharge it to at least one device on the turbomachine, and an anti-siphon valve designed to prevent the flow of oil to the device or devices. The anti-siphon valve is located upstream of the pump and is designed to allow the flow of oil when the speed of the pump becomes higher than a speed R1. The present application also relates to a turbojet fitted with a fan and two anti-siphon valves designed to open at different rotational speeds of the first pump.

We claim: 
     
         1 . Oil feed system for a turbomachine, comprising:
 a tank configured to contain a volume of oil;   a feed pump for at least one device on the engine, the pump being connected to the tank and the one or more devices; and   means of closure for the flow from the feed pump to the device or devices when the pump speed is less than a speed R1;   wherein the means of closure are located hydraulically upstream of the pump, between the pump and the tank.   
     
     
         2 . The oil feed system in accordance with  claim 1 , wherein the means of closure comprises:
 an anti-siphon valve configured to close when the suction level of the feed pump is lower than a given threshold.   
     
     
         3 . The oil feed system in accordance with  claim 1 , wherein the means of closure are located in the tank. 
     
     
         4 . The oil feed system in accordance with  claim 1 , wherein the means of closure are mechanically controlled by the suction level of the feed pump and by the pressure in the tank. 
     
     
         5 . The oil feed system in accordance with  claim 1 , wherein the pump is a first pump, the means of closure are a first means of closure, wherein the system further comprises:
 a second feed pump for which the mechanical drive is coupled to that of the first pump connected to the tank and one or more other devices in the turbomachine, the second means of closure of the discharge from the second feed pump when the speed of the first feed pump falls below a speed R2, the means being located upstream of the said pump, speed R2 being different from speed R1.   
     
     
         6 . The oil feed system in accordance with  claim 5 , wherein speeds R1 and R2 differ by greater than 5%, more preferably by greater than 10%, more preferably by greeter than 30%, even more preferably by greater than 100%. 
     
     
         7 . The oil feed system in accordance with  claim 5 , wherein speeds R1 and R2 differ by greater than 10%. 
     
     
         8 . The oil feed system in accordance with  claim 5 , wherein speeds R1 and R2 differ by greater than 30%. 
     
     
         9 . The oil feed system in accordance with  claim 5 , wherein speeds R1 and R2 differ by greater than 100%. 
     
     
         10 . The oil feed system in accordance with  claim 1 , wherein the feed pump has internal bypasses designed to reduce its suction pressure when the corresponding means of closure cut the flow. 
     
     
         11 . The oil feed system in accordance with  claim 1 , further comprisiung:
 a control channel connecting the outlet to the feed pump to the corresponding means of closure, so as to allow a flow of oil when the discharge pressure of the pump exceeds a pressure P1.   
     
     
         12 . A turbojet, comprising:
 one or devices; and   an oil feed system comprising:
 a tank configured to contain a volume of oil; 
 a feed pump for at least one device on the engine, the pump being connected to the tank and the one or more devices; and 
 means of closure for the flow from the feed pump to the device or devices when the pump speed is less than a speed R1; 
 wherein the means of closure are located hydraulically upstream of the pump, between the pump and the tank. 
   
     
     
         13 . The turbojet in accordance with  claim 12 , further comprising:
 a fan, the drive from which is coupled to that of the feed pump, the fan driving the feed pump at a speed R3 when the turbojet is in flight and is not being supplied with fuel, corresponding to an autorotation flight mode, the speed R3 being less than the speed R1, so that the feed pump does not discharge when the turbojet is in autorotation flight mode.   
     
     
         14 . The turbojet in accordance with  claim 12 , further comprising:
 a fan which is coupled to drive the first and second feed pumps, the fan rotating and driving in rotation the first feed pump to a speed R3 of the first feed pump when the turbojet is in flight and is not being supplied with fuel, corresponding to an autorotation flight mode, the speed R3 being between the speeds R1 and R2, such that one of the first and second feed pumps discharges to its corresponding devices and the other of the pumps does not discharge when the turbojet is in autorotation flight mode.   
     
     
         15 . The turbojet in accordance with  claim 13 , wherein the drive speed R3 relative to the drive speed when the turbojet is at its rated operational speed is less than 50%. 
     
     
         16 . The turbojet in accordance with  claim 13 , wherein the drive speed R3 relative to the drive speed when the turbojet is at its rated operational speed is less than 30%. 
     
     
         17 . The turbojet in accordance with  claim 13 , wherein the drive speed R3 relative to the drive speed when the turbojet is at its rated operational speed is less than 10%. 
     
     
         18 . The turbojet in accordance with  claim 12 , wherein the devices fed by the feed pumps comprises:
 at least one lubricating chamber for a rotor bearing.   
     
     
         19 . The turbojet in accordance with  claim 12 , wherein the oil feed system further comprises:
 an oil recovery loop for at least one of the devices, the loop being provided with a scavenge pump for which the drive is preferably coupled to the drive for the feed pump.   
     
     
         20 . The turbojet in accordance with  claim 12 , wherein the oil feed system comprises:
 a control pipe connecting the recovery loop downstream of the recovery pump with corresponding means of closure, the means being designed to allow a flow of oil when the pressure in the control channel is greater than a pressure P2.