BACKGROUND OF THE INVENTION

This application relates to face seals as utilized in gas turbine engines.

Gas turbine engines are known, and typically include a fan delivering into a bypass duct for propulsion, and into a core engine where it is compressed. The compressed air is delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate. The turbine rotors, in turn, drive compressor rotors and the fan. Shafts connect the turbine rotors to the compressor and fan rotors.

Bearings support these shafts. The bearings may be provided with lubricant, and thus it is desirable to seal a compartment on each axial side of the bearings.

Face seal arrangements are utilized in the prior art. A seal seat rotates with the shaft on each side of the bearing. A face seal is biased in the contact with the seal seat.

Typically a spring force biases the face seal into the seal seat. Pressurized air acting on a surface of the face seal also provides a bias force.

In the prior art the balance ratio, which is the area over which the pressurized air acts on the face seal taken as a ratio to the entire sealing face area of the face is relatively high. In addition, with this arrangement the spring force has been relatively high. This has resulted in challenges for operation of the prior face seal arrangements. A high axial closing force results in high heat generation, and sometimes oil coking and result in reduced service life.

SUMMARY OF THE INVENTION

In a featured embodiment, a gas turbine engine includes a fan for delivering air into a bypass duct as propulsion air and to a core engine. The core engine includes a compressor section including at least one compressor rotor, a combustor section and a turbine section including at least one turbine rotor. The turbine rotor is connected to drive a shaft which in turn is connected to a drive at least one of the compressor rotor and the fan. A bearing is mounted to a static structure outwardly of the shaft, and supports the shaft. A bearing compartment is defined by face seal arrangements on each of two axial sides of the bearing. Each face seal arrangement includes a seal seat rotating with the shaft and a non-rotating face seal. Each non-rotating face seal includes a sealing ring mounted to a seal housing. The sealing ring includes a mount portion mounted to the seal housing and a sealing face biased into contact with the seal seat. The sealing ring also has a groove defined remote from the seal face relative to the seal seat. The groove provides a pressure face that will be exposed to high pressure air outward of the bearing compartment. A coil spring biases the seal housing towards the seal seat, such that the sealing face of the sealing ring is biased into contact with the seal seat by air pressure against the pressure face, and the coil spring. A balance ratio is defined between an area of the pressure face and an area of the sealing face, the balance ratio is between 0.5 and 0.64.

In another embodiment according to the previous embodiment, wherein the balance ratio is between 0.52 and 0.58.

In another embodiment according to any of the previous embodiments, the seal housing is formed of one of a titanium alloy and a ceramic.

In another embodiment according to any of the previous embodiments, the at least one compressor rotor includes a high speed compressor rotor and a low speed compressor rotor. The at least one turbine rotor includes a high speed turbine rotor and a low speed turbine rotor. A low speed turbine rotor drives the low speed compressor rotor through a low speed shaft. The high speed turbine rotor drives the high speed compressor rotor through a high speed shaft.

In another embodiment according to any of the previous embodiments, the high speed shaft is the shaft supported by the bearing.

In another embodiment according to any of the previous embodiments, the low speed shaft is the shaft supported by the bearing.

In another embodiment according to any of the previous embodiments, the low speed shaft also drives the fan rotor through a gear reduction, and the gear reduction drives a fan shaft. The fan shaft is the shaft supported by the bearing.

In another embodiment according to any of the previous embodiments, the seal seat has a radially outermost surface and the sealing ring has a radially outermost surface. The seal seat radially outermost surface extends radially outward of the sealing ring radially outermost surface.

In another embodiment according to any of the previous embodiments, the seal seat has a radially outermost surface and the sealing ring has a radially outermost surface. The seal seat radially outermost surface is radially inward of the sealing ring radially outermost surface.

In another embodiment according to any of the previous embodiments, the width quantity is defined as the balance ratio multiplied by a radial width of the sealing face divided by an outer diameter of the sealing ring at the sealing face, and the width quantity is between 0.009 and 0.013 or between 0.0135 and 0.0160.

In another embodiment according to any of the previous embodiments, the seal seat has an inner diameter and an outer diameter. There is a plurality of slots circumferentially spaced and have an inlet to receive oil from an inner diameter of the seal seat and a circumferentially spaced outlet to outlet oil to an outer diameter of the seal seat and a plurality of drain grooves circumferentially spaced and radially inward of the slots. A supply groove connects the inner diameter to the inlet in the slots and a discharge groove connects the outlet of the slots to the outer diameter. A drain groove discharge groove communicates the drain grooves to the outer diameter.

In another embodiment according to any of the previous embodiments, the inlet groove, the outlet groove, and the discharge groove all extend at an angle that is not directly radially outward of a rotational axis of the seal seat. The seal seat rotates in a first circumferential direction. The angles of each of the inlet groove, outlet groove and drain groove have a radially outward component and a component in a circumferential direction opposed to the first circumferential direction.

In another featured embodiment, a face seal arrangement includes a seal seat for rotating with a shaft and a non-rotating face seal. Each the non-rotating face seal includes a sealing ring mounted to a seal housing. The sealing ring includes a mount portion mounted to the seal housing and a sealing face biased into contact with the seal seat. The sealing ring also has a groove defined remote from the seal face relative to the seal seat. The groove provides a pressure face that will be exposed to high pressure air. A coil spring biases the seal housing towards the seal seat, such that the sealing face of the sealing ring is biased into contact with seal seat by air pressure against the pressure face, and the coil spring. A balance ratio is defined between an area of the pressure face and an area of the sealing face. The balance ratio is between 0.5 and 0.64.

In another embodiment according to the previous embodiment, the balance ratio is between 0.52 and 0.58.

In another embodiment according to any of the previous embodiments, the seal housing is formed of one of a titanium alloy and a ceramic.

In another embodiment according to any of the previous embodiments, the width quantity is defined as the balance ratio multiplied by a radial width of the sealing face divided by an outer diameter of the sealing ring at the sealing face, and the width quantity being between 0.009 and 0.013 or between 0.0135 and 0.0160.

In another embodiment according to any of the previous embodiments, the seal seat has a radially outermost surface and the sealing ring has a radially outermost surface. The seal seat radially outermost surface extends radially outward of the sealing ring radially outermost surface.

In another embodiment according to any of the previous embodiments, the seal seat has a radially outermost surface and the sealing ring has a radially outermost surface. The seal seat radially outermost surface is radially inward of the sealing ring radially outermost surface.

In another embodiment according to any of the previous embodiments, the seal seat has an inner diameter and an outer diameter. There are a plurality of slots circumferentially spaced and has an inlet to receive oil from an inner diameter of the seal seat and a circumferentially spaced outlet to outlet oil to an outer diameter of the seal seat and a plurality of drain grooves circumferentially spaced and radially inward of the slots. A supply groove connects the inner diameter to the inlet in the slots and a discharge groove connecting the outlet of the slots to the outer diameter. A drain groove discharge groove communicates the drain grooves to the outer diameter.

In another embodiment according to any of the previous embodiments, the inlet groove, the outlet groove, and the discharge groove all extend at an angle that is not directly radially outward of a rotational axis of the seal seat. The seal seat rotates in a first circumferential direction. The angles of each of the inlet groove, outlet groove and drain groove have a radially outward component and a component in a circumferential direction opposed to the first circumferential direction.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

