Patent Application
20060090964
The present invention relates to a lubrication system for an aircraft gas turbine engine, and relates in particular to a lubrication system which provides an uninterrupted supply of lubricant when the is in an inverted flight condition.
Many proposals have been made to avoid the problems associated with lubricant starvation in bearing chambers when, for example, an aircraft takes up an inverted flight condition and the lubricant in the tank moves away from the pump inlet, which prevents the pump from supplying any lubricant. The proposals usually involve baffles within the tank in order to maintain a reservoir of lubricant at the pump inlet during inverted flight and the positioning of the pump inlet within the reservoir, so that the pump continues to supply lubricant for a limited period.
However, there is still a need for alternative configurations and arrangements for a lubrication system of gas turbine engines which is adapted to continuously supply lubricant for engine bearings when the aircraft changes to inverted flight condition.
One object of the present invention is to provide an improved lubrication system for aircraft engines.
In accordance with one aspect of the present invention, there is a gravity controlled lubrication system provided for an engine of an aircraft, which comprises a lubricant tank for containing a lubricant therein, a pump having an outlet and an inlet, a first fluid passage for directing the lubricant in the tank to the pump inlet during a normal flight condition, and a second fluid passage isolated from the first fluid passage during the normal flight condition to direct a used lubricant flow from a lubricant returning system of the engine to the tank. A gravity controlled mechanism is provided for closing the first fluid passage to the tank and connecting the first fluid passage with the second fluid passage when the aircraft changes from the normal flight condition into a inverted flight condition, thereby a majority portion of the used lubricant flow from the lubricant returning system directly entering the pump inlet without passing through the tank.
In accordance with another aspect of the present invention, there is a gravity controlled lubrication system provided for an engine of aircraft, which comprises a lubricant tank for containing a lubricant therein, a pump having an outlet and an inlet, and a valve assembly. The valve assembly includes a valve body defining a cavity therein and a valve member positioned in a first position within the cavity and moveable under the gravity thereof from the first position to a second position within the cavity when the aircraft changes to an inverted flight condition. The valve body further defines first, second, third and fourth openings therein in fluid communication with the cavity. The first opening is connected to a first tube terminating within the tank at a bottom thereof. The second opening is connected to the inlet of the pump. The third opening is connected to a lubricant returning system of the engine. The fourth opening is in fluid communication with the inside of the tank. The valve member when being positioned in the first position divides the cavity into isolated sections to permit a first fluid passage between the first and second openings and a second fluid passage between the third and fourth openings, respectively. The valve member when moving into the second position closes the fourth opening and permits fluid communication within the cavity between the first, second and third openings.
In accordance with a further aspect of the present invention there is a method for pumping a lubricant to a lubricant circulating system of an engine of an aircraft when the aircraft changes from a normal flight condition to an inverted flight condition. The method comprises during the normal flight condition, pumping the lubricant to the lubricant circulating system using a pump to suck the lubricant from a tank through a pump inlet passage while directing a used lubricant flow from the lubricant circulating system through a returning passage into the tank; and when the aircraft change to the inverted flight condition, using a gravity controlled mechanism to shift the returning passage from fluid communication with the tank to fluid communication directly with the pump inlet passage such that the pump sucks the lubricant directly from the used lubricant flow rather than from the tank.
The present invention provides a simple configuration of a lubricating system for aircraft engines to solve the lubricant starvation problem in engine bearings for a limited period of time when the aircraft changes to the inverted flight condition.
Other features and advantages of the present invention will be better understood with reference to the preferred embodiments described hereinafter.
Reference will now be made to the accompanying drawings showing by way of illustration preferred embodiments, in which:
Referring to
The valve body 12 defines two lower openings 26, 28 in a part of the valve body 12 defining the middle section 18 of the cavity 14, and two upper openings 30, 32 in a part of the valve body 12 defining the upper section 16 of the cavity 14. The lower opening 26 is connected to a tube 34 terminating at the other end thereof within a lubricant tank 36, at the bottom thereof. The lower opening 28 is connected to an inlet tube 38 of a lubricant pump 40. The upper opening 30 is connected to a lubricant returning system of the engine, such as a lubricant cooler or scavenger (not shown), through a lubricant returning line 42. The upper opening 32 is in fluid communication with the lubricant tank 36, preferably with an inner space of the tank 36 above the lubricant level within the tank 36.
A valve member includes, for example, a piston element 44 freely moveable within the upper section 16 of the cavity 14 along a longitudinal axis (not indicated) of the valve body 12. The valve member preferably further includes another piston element 46 freely moveable within the bottom section 20 of the cavity 14 along the longitudinal axis of the valve body 12. A rod 48 extends between the two piston elements 44, 46 and interconnects same together. The piston element 44 within the upper section 16 rests on the interface 22 between the upper section 16 and the middle section 18 of the cavity 14 under the gravity thereof under normal flight conditions. Thus, the piston element 44 isolates the upper section 16 from the entire lower section including the middle section 18 and the bottom section 20 of the cavity 14. The piston element 46 and the rod 48 enhance a gravity force on the piston element 44 to secure a sealing position of the piston element 44 on the interface 22. Therefore, the piston element 46 preferably does not contact a bottom wall 50 of the cavity 14 in order to prevent interference with the isolation performance achieved by piston element 44 resting on the interface 22.
Under normal flight conditions the valve assembly 12 constitutes two isolated fluid passages. In the first passage the lubricant pump 40 sucks the lubricant contained within the lubricant tank 36 out of the pipe 34, through the middle and bottom sections 18, 20 of the cavity 14 and the inlet tube 38, and then pumps the lubricant through a pump outlet tube 52 into the lubricant circulating system of the aircraft engine (not shown). In this first passage, the tube 34 functions as an extension of the pump inlet tube 38. A filter device 54 is preferably connected in the pump inlet tube 38 such that the lubricant is filtered by the filter device 54 before entering the lubricant pump 40. In the second passage the used lubricant is delivered from the lubricant returning line 42 into the upper section 16 of the cavity 14 and through the opening 32 into the lubricant tank 36.
Referring to
The entire valve member can either rest on the top wall 56 (by piston element 44) or on the interface 24 (by piston element 46), provided the piston element 44 is aligned with the opening 32 to efficiently close same.
In this upside down situation, the pump 40 is no longer capable of sucking the lubricant from the tank 36 because the lubricant within the tank 36 has been collected in the top portion thereof (now in a lower position) and the opening of the tube 34 is exposed to the empty portion of the tank 36. Nevertheless, the cavity 14 of the valve assembly 10 permits fluid communication between the openings 26, 28 and 30. Thus, the used lubricant is delivered through the lubricant returning line 42 by another pumping device (not shown) in the lubricant returning system, into the upper section 16 (now in a lower position) and the middle section 18 of the cavity 14. The lubricant in the cavity 14 is sucked by the lubricant pump 40 through the pump inlet tube 38 and is pumped out through the pump outlet tube 52 into the lubricant circulating system of the aircraft engine.
It should be noted that the used lubricant usually contains a certain amount of air mixed therein even though the used lubricant may have been treated by an air/lubricant separating device (not shown) in the lubricant returning system. Therefore, the volume of the used lubricant entering the cavity 14 is usually greater than the capacity of the lubricant pump 40. The excess portion of the used lubricant flows into the tube 34 and is discharged into the tank 36.
The gravity controlled lubrication system according to another embodiment of the present invention is described with reference to
The valve assembly 110 according to this embodiment defines a cavity 114 including an upper section 116 and a lower section 118 which has a diameter smaller than the diameter of the upper section 116. Thus, a valve member seat is formed on the interface 122 between the upper and lower sections 116, 118 of the cavity 114. The lower openings 126, 128 are positioned in a part of the valve body 112 defining the lower section 118 of the cavity 114. The upper openings 130, 132 are positioned in a part of the valve body 112 defining the upper section 116 of the cavity 114. In contrast to the embodiment shown in
Referring to
In a further embodiment of the present invention as illustrated in
The valve assembly in the above described embodiments is preferably positioned within the lubricant tank. Nevertheless, the valve assembly can be positioned outside of the tank and provides equal function, provided that an appropriate tube is connected to the upper opening 32 of
It should be noted that the lubrication system according to the present invention is intended for use during a limited period of time of inverted flight conditions because a small amount of used lubricant from the returning line is not re-pumped into the lubricant circulating system, but enters the tank.
Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.
