Tri-body variable area fan nozzle and thrust reverser

This invention relates to gas turbine engines and, more particularly, to a gas turbine engine having a nozzle that integrates functions of a variable fan nozzle and a thrust reverser.

Gas turbine engines are widely known and used for power generation and vehicle (e.g., aircraft) propulsion. A typical gas turbine engine includes a compression section, a combustion section, and a turbine section that utilize a primary airflow into the engine to generate power or propel the vehicle. The gas turbine engine is typically mounted within a housing, such as a nacelle. A bypass airflow flows through a passage between the housing and the engine and exits from the engine at an outlet.

Presently, conventional thrust reversers are used to generate a reverse thrust force to slow forward movement of a vehicle, such as an aircraft. One type of conventional thrust reverser utilizes a moveable door stowed near the rear of the nacelle. After touch-down of the aircraft for landing, the door moves into the bypass airflow passage to deflect the bypass airflow radially outwards into cascades, or vents, that direct the discharge airflow in a forward direction to slow the aircraft. Although effective, this and other conventional thrust reversers serve only for thrust reversal and, when in the stowed position for non-landing conditions, do not provide additional functionality. The use of a variable area fan nozzle (VAFN) has been proposed for low pressure ratio fan designs to improve the propulsive efficiency of high bypass ratio gas turbine engines. Therefore, the problem to be solved is integrating the VAFN functionality with the thrust reverser to reduce complexity and weight.

A gas turbine engine system includes a fan, a housing arranged about the fan, a gas turbine engine core having a compressor within the housing, and a fan bypass passage downstream of the fan for conveying a bypass airflow between the housing and the gas turbine engine core. A nozzle associated with the fan bypass passage includes a first nozzle section that is operative to move in a generally axial direction to influence the bypass airflow, and a second nozzle section that is operative to also move in a generally axial direction between a stowed position and a thrust reverse position that diverts the bypass airflow in a thrust reversing direction. An actuator selectively moves the first nozzle section and the second nozzle section to influence the bypass airflow and provide thrust reversal.

An example method of controlling the gas turbine engine system includes the steps of selectively moving the first nozzle section between an open position and a closed position to vary an effective cross-sectional area of the nozzle to control the bypass airflow and selectively moving the second nozzle section between a stowed position and a thrust reverse position to reverse a direction of the bypass flow and produce a thrust reversal force.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.

FIG. 1 illustrates selected portions of an example gas turbine engine system having a nozzle for varying an effective exit area or producing a thrust reversing force.

FIG. 2 illustrates a schematic view of the nozzle in a closed/stowed position.

FIG. 3 illustrates a schematic view of the nozzle in an open position for increasing the effective exit area.

FIG. 4 illustrates a schematic view of the nozzle in a thrust reverse position.

FIG. 5 illustrates a perspective view of the nozzle in the thrust reverse position.

FIG. 1 illustrates a schematic view of selected portions of an example gas turbine engine 10 suspended from an engine pylon 12 of an aircraft, as is typical of an aircraft designed for subsonic operation. The gas turbine engine 10 is circumferentially disposed about an engine centerline, or axial centerline axis A. The gas turbine engine 10 includes a fan 14 , a low pressure compressor 16 a , a high pressure compressor 16 b , a combustion section 18 , a low pressure turbine 20 a , and a high pressure turbine 20 b . As is well known in the art, air compressed in the compressors 16 a , 16 b is mixed with fuel that is burned in the combustion section 18 and expanded in the turbines 20 a and 20 b . The turbines 20 a and 20 b are coupled for rotation with, respectively, rotors 22 a and 22 b (e.g., spools) to rotationally drive the compressors 16 a , 16 b and the fan 14 in response to the expansion. In this example, the rotor 22 a also drives the fan 14 through a gear train 24 .

In the example shown, the gas turbine engine 10 is a high bypass turbofan arrangement. In one example, the bypass ratio is greater than 10:1, and the fan 14 diameter is substantially larger than the diameter of the low pressure compressor 16 a . The low pressure turbine 20 a has a pressure ratio that is greater than 5:1, in one example. The gear train 24 can be any known suitable gear system, such as a planetary gear system with orbiting planet gears, planetary system with non-orbiting planet gears, or other type of gear system. In the disclosed example, the gear train 24 has a constant gear ratio. Given this description, one of ordinary skill in the art will recognize that the above parameters are only exemplary and that other parameters may be used to meet the particular needs of an implementation.

An outer housing, nacelle 28 , (also commonly referred to as a fan nacelle or fan cowl) extends circumferentially about the fan 14 . A generally annular fan bypass passage 30 extends between the nacelle 28 and an inner housing, inner cowl 34 , which generally surrounds the compressors 16 a , 16 b and turbines 20 a , 20 b.

In operation, the fan 14 draws air into the gas turbine engine 10 as a core flow, C, and into the bypass passage 30 as a bypass airflow, D. In one example, approximately 80 percent of the airflow entering the nacelle 28 becomes bypass airflow D. A rear exhaust 36 discharges the bypass airflow D from the gas turbine engine 10 . The core flow C is discharged from a passage between the inner cowl 34 and a tail cone 38 . A significant amount of thrust may be provided by the discharge flow due to the high bypass ratio.

The example gas turbine engine 10 shown FIG. 1 also includes a nozzle 40 (shown schematically) associated with the bypass passage 30 . In this example, the nozzle 40 is shown near the rear of the nacelle 28 , however, in other examples, the nozzle 40 is not an exhaust nozzle but is rather located farther forward but aft of the fan 14 . In this example, the nozzle 40 is coupled to the nacelle 28 .

The nozzle 40 is operatively connected with actuators 42 for movement between a plurality of positions to influence the bypass airflow D, such as to manipulate an air pressure of the bypass airflow D. A controller 44 commands the actuators 42 to selectively move the nozzle 40 among the plurality of positions to manipulate the bypass airflow D in a desired manner. The controller 44 may be dedicated to controlling the actuators 42 and nozzle 40 , integrated into an existing engine controller within the gas turbine engine 10 , or be incorporated with other known aircraft or engine controls. For example, selective movement of the nozzle 40 permits the controller 44 to vary the amount and direction of thrust provided, enhance conditions for aircraft control, enhance conditions for operation of the fan 14 , or enhance conditions for operation of other components associated with the bypass passage 30 , depending on input parameters into the controller 44 .

In one example, the gas turbine engine 10 is designed to operate within a desired performance envelope under certain predetermined conditions, such as cruise. For example, the fan 14 is designed for a particular flight condition—typically cruise at 0.8 Mach and 35,000 feet. The fan 14 is designed at a particular fixed stagger angle for an efficient cruise condition. The nozzle 40 is operated to influence the bypass airflow D such that the angle of attack or incidence on the fan 14 is maintained close to design incidence at other flight conditions, such as landing and takeoff, thus enabling a desired engine operation over a range of flight condition with respect to performance and other operational parameters such as noise levels. In one example, it is desirable to operate the fan 14 under a desired pressure ratio range (i.e., the ratio of air pressure forward of the fan 14 to air pressure aft of the fan 14 ) to avoid fan flutter. To maintain this range, the nozzle 40 is used to influence the bypass airflow D to control the air pressure aft of the fan 14 and thereby control the pressure ratio. In some examples, the nozzle varies an effective cross-sectional area associated with the rear exhaust 36 of the bypass passage 30 by approximately 20% to influence the bypass airflow D.

FIG. 2 illustrates an example of the nozzle 40 for varying the effective cross-sectional area and functioning as a thrust reverser to slow movement of a vehicle such as an aircraft, as will be described below. In this example, the nozzle 40 includes a first nozzle section 54 a and a second nozzle section 54 b that is located forwardly adjacent the first nozzle section 54 a . The first nozzle section 54 a is moveable between a plurality of positions in a generally axial direction relative to the centerline axis A, and the second nozzle section 54 b is moveable between a stowed position and a thrust reverse position that diverts the bypass airflow D in a thrust reversing direction.

In this example, each actuator 42 includes a control section 56 that communicates with the controller 44 , and a telescoping member 58 for selectively moving the first nozzle section 54 a and the second nozzle section 54 b . In this example, the telescoping member 58 includes a first telescoping section 60 a , such as a cylindrical shaft, connected with the first nozzle section 54 a . A second telescoping section 60 b , such as another cylindrical shaft, is concentrically arranged about the first telescoping section 60 a and connected with the second nozzle section 54 b . Given this description, one of ordinary skill in the art will recognize other types of actuator arrangements suitable for moving the first nozzle section 54 a and the second nozzle section 54 b.

The second nozzle section 54 b includes a leading end 62 having a curved surface 64 that seals against the nacelle 28 in this example. A radially inner portion of the second nozzle section 54 b stows blocker doors 66 (one shown) that are pivotally attached to the second nozzle section 54 b in a known manner. A drag link 68 is pivotally attached at one end to the blocker door 66 and pivotally attached at its other end to the inner cowl 34 in this example. Optionally, the drag links 68 are slidably connected to the blocker doors 66 , inner cowl 34 , or both to facilitate movement of the blocker doors 66 between the stowed position and the deployed, thrust reverse position ( FIG. 4 ).

In operation, the controller 44 selectively commands the actuators 42 to move the first nozzle section 54 a to influence the bypass airflow D or to move the second nozzle section 54 b to provide thrust reversal. The actuators 42 can independently move the first nozzle section 54 a and the second nozzle section 54 b . FIG. 2 illustrates the first nozzle section 54 a in a closed position and the second nozzle section 54 b in the stowed position sealed against the nacelle 28 . In the closed/stowed position, the bypass airflow D exits axially through the rear exhaust 36 , and the nozzle 40 has an effective cross-sectional area that corresponds to a distance AR between the nozzle 40 and the inner cowl 34 in this example.

Referring to FIG. 3 , the actuators 42 extend the first telescoping section 60 a from the second telescoping section 60 b in response to a command from the controller 44 to move the nozzle from the closed position to the open position. In the open position, the first nozzle section 54 a is spaced apart from the second nozzle section 54 b to provide an opening 70 there between. In one example, the first telescoping section 60 a is moved in a known manner using hydraulic or pneumatic power.

The opening 70 provides an auxiliary passage having a cross-sectional area proportional to a distance AR′ between the first nozzle section 54 a and the second nozzle section 54 b for the discharge of the bypass airflow D. The auxiliary passage provides an additional passage (i.e., additional effective cross-sectional flow area) for exit of the bypass airflow D from the bypass passage 30 to thereby alter the bypass airflow D. Thus, the total effective cross-sectional area for discharge of the bypass airflow D in this example is AR+AR′.

The controller 44 selectively actuates the first nozzle section 54 a , as described above, to control the air pressure of the bypass airflow D within the bypass passage 30 . For example, closing the first nozzle section 54 a reduces the effective cross-sectional area, which restricts the bypass airflow D and produces a pressure build-up (i.e., an increase in air pressure) within the bypass passage 30 . Opening the first nozzle section 54 a increases the effective cross-sectional area, which permits more bypass airflow D and reduces the pressure build-up (i.e., a decrease in air pressure). Likewise, a relatively smaller effective cross-sectional area results in less thrust due to the discharge of the bypass airflow D and a relatively larger effective cross-sectional area results in more thrust from the discharge of the bypass airflow D. In one example, the controller opens the first nozzle section 54 a during take-off for additional thrust. Given this description, one of ordinary skill in the art will be able to recognize other types of nozzles for influencing the bypass airflow D.

Referring to FIGS. 4 and 5 , the actuators 42 move the second telescoping section 60 b axially aft in response to a command from the controller 44 to move the second nozzle section 54 b from the stowed position to the thrust reverse position. In the thrust reverse position, the second nozzle section 54 b is spaced apart from the nacelle 28 to provide an opening 72 there between. In one example, the second telescoping section 60 b is moved in a known manner using hydraulic or pneumatic power.

Movement of the second nozzle section 54 b causes the drag links 68 to pivot the blocker doors 66 into the bypass passage 30 . The blocker doors 66 block the bypass airflow D and deflect the bypass airflow D radially outwards and forward relative to the centerline axis A through the opening 72 . The movement of the second nozzle section 54 b to the thrust reverse position also exposes the curved surface 64 . The curved surface 64 deflects the bypass airflow D in a forward direction Z to generate a reverse thrust force.

In the disclosed example, the first telescoping section 60 a and the first nozzle section 54 a move axially when the second telescoping section 60 b and the second nozzle section 54 b move to the thrust reverse position. Alternatively, the first telescoping section 60 a and the first nozzle section 54 a remain stationary relative to the second telescoping section 60 b and the second nozzle section 54 b such that the first nozzle section 54 a closes (i.e., the first nozzle section seals against the second nozzle section 54 b to eliminate the opening 70 ).

Optionally, the nozzle 40 includes one or more cascade sections 74 for diverting the bypass airflow D that is discharged for thrust reversal in a desired direction. In this example, the cascade section includes louvers 76 , such as airfoil-shaped louvers, that divert the discharged bypass airflow D in directions away from the pylon 12 and away from the ground (the bottom of FIG. 5 ).

The disclosed example nozzle 40 thereby integrates the function of influencing the bypass airflow D with the thrust reversing function. The nozzle 40 utilizes a single set or system of actuators 42 to eliminate the need for separate actuators or sets of actuators for altering the bypass airflow D and deploying the thrust reverser. Using a single actuator or set of actuators 42 as in the disclosed examples eliminates at least some of the actuators that would otherwise be used, thereby reducing the weight of the gas turbine engine 10 and increasing the fuel efficiency.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.