Combined control valve and air turbine starter

This application relates to a starter system for a gas turbine engine wherein an airflow control valve is incorporated into a nozzle of an air turbine starter.

Gas turbine engines are utilized in aircraft applications. Various accessories are associated with aircraft gas turbine engines.

One type of accessory is an air turbine starter. An air turbine starter is selectively connected to an accessory gearbox in the gas turbine engine. A source of pressurized air is communicated into the air turbine starter, and drives a turbine which in turn drives the accessory gearbox.

As known, an accessory gearbox has a tower shaft that is connected to a spool shaft in the gas turbine engine. During normal aircraft operation the spool shaft drives the tower shaft to in turn drive the accessories associated with the accessory gearbox. However at start, the torque transfer moves in the opposite direction to begin turning the spool shaft.

Typically a control valve controls the flow of air between the source of compressed air and the air turbine starter. In the prior art this valve has been remote from the air driven starter and its housing.

A combined air turbine starter and flow control valve includes a turbine having turbine blades and a shaft rotating with the turbine blades. The turbine is received within a nozzle housing. The nozzle housing includes an inlet. A radially outwardly extending inner surface extends from the inlet and toward the turbine blades. A flow control piston is received to be movable along a rotational axis of the turbine shaft, and toward and away the radially outwardly extending surface of the nozzle housing. A control is programmed to direct a movement system to position the flow control piston relative to the radially outwardly extending surface to achieve a desired volume of airflow to the turbine blades.

These and other features will be best understood from the following drawings and specification, the following is a brief description.

FIG. 1 schematically shows a gas turbine engine and an associated starter system.

FIG. 2 shows an airflow control valve incorporated into the nozzle of an air turbine starter in an open position.

FIG. 3 shows the airflow control valve at an intermediate position.

FIG. 4 shows the airflow control valve in a closed position.

FIG. 1 shows a gas turbine engine 20 having a spool shaft 22 rotating with a fan rotor 24 , a compressor 26 and a turbine 28 . A combustor 30 is positioned intermediate the compressor 26 and turbine 28 . In practice, there are typically at least two spool shafts each driving compressor and turbine sections. That is, FIG. 1 shows the gas turbine engine 20 in a very schematic manner.

A starter system 31 is shown having a source of compressed air 32 . The source of compressed air 32 may be an auxiliary power unit (“APU”), an air cart, or a cross bleed from a gas turbine engine which is already running. Air from the source 32 passes into a conduit 33 and to an air turbine starter 34 . The air turbine starter 34 includes a shaft 46 driving a shaft 25 in the auxiliary gearbox 36 to in turn drive the tower shaft 100 . The tower shaft 100 is rotatably connected with the spool shaft 22 , and drives the spool shaft 22 at startup to begin rotation of the components 24 , 26 and 28 . The description to this point is known, other than in the prior art there has typically been an airflow control valve on the conduit 33 .

FIG. 2 shows a combination 34 of the air turbine starter and the airflow control valve. Thus, a housing 37 defines a nozzle surface 40 moving from an inlet 38 connected to the conduit 33 and leading into a radially outwardly extending nozzle surface 40 . Downstream of the nozzle surface 40 , the airflow reaches a generally cylindrical section 41 that is generally centered about a rotational axis X of a turbine shaft 46 . The air passes over vanes 42 , and then blades 44 which drive the turbine shaft 46 .

Air from the source 32 thus moves through the nozzle surface 40 and drives the blades 44 . A valve piston 54 is received in housing structure 50 which provides a guiding surface for the valve piston 54 . As shown, housing surface 50 is connected to the vanes 42 , although this is not necessary.

A stop 51 is shown abutting a rear end 52 of the piston 54 . A generally conical outer surface 56 defines the flowpath in combination with the nozzle surface 40 . Shaft 46 is shown schematically driving the gearbox 36 .

A control 48 controls a drive 60 for moving the piston 54 along axis X toward and away from the radially outwardly extending surface 40 . The details of how drive 60 may move piston 54 are within the skill of a worker in the art. Any number of arrangements may be utilized. A connection 62 is shown schematically. The control may be an appropriate electronic controller, and may be programmed to deliver a desired volume of air to the turbine blades 44 . As an example, in the FIG. 2 position the valve piston 54 defines a fully open position within piston end 52 abutting stop surface 51 . Alternatively a pneumatic, hydraulic or mechanical control could be used.

Air turbine starters often operate in a “bowed shaft” mode. If the gas turbine 20 is started before it is fully cooled off the shaft 22 may be somewhat distorted. Thus, the starting speed would be at a percentage of a full starting speed that would be achieved in the FIG. 2 position to allow the gas turbine to cool down.

This bowed start position is shown in FIG. 3 . The surface 56 of the valve piston 54 has now been moved closer to the radially outwardly extending surface 40 . The end 52 of the piston 54 is still guided on the surface 50 . This position is achieved with the control 48 controlling drive 60 and its rotational axis 62 to move the valve piston 54 to the left along the axis X as shown in FIG. 3 from the FIG. 2 position.

FIG. 4 shows yet another position. In this position, the radially outwardly extending surface 56 of the valve piston 54 now abuts the radially outwardly extending surface 40 of the housing 37 . In this position, no airflow is allowed to reach the turbine blades 44 .

The mechanical member 60 is shown in a chamber 58 within piston 54 and spaced toward the inlet 38 relative to the turbine blades 44 and shaft 46 .

By incorporating the valve into the nozzle, a separate required valve as found in the prior art is eliminated. Moreover, the guiding surface between an interior 49 of piston 54 that is generally formed to be cylindrical and centered on the axis X, is closely guided along the surface 50 to achieve very precise positioning. Moreover, the overall packaging size is reduced given the incorporation of the valve.

A combined air turbine starter and flow control valve under this disclosure could be said to include a turbine having turbine blades and a shaft rotating with the turbine blades. The turbine is received within a nozzle housing. The nozzle housing includes an inlet. A radially outwardly extending inner surface extends from the inlet and toward the turbine blades. A flow control piston is received to be movable along a rotational axis of the turbine shaft, and toward and away the radially outwardly extending surface of the nozzle housing. A control is programmed to direct a movement system to position the flow control piston relative to the radially outwardly extending surface to achieve a desired volume of airflow to the turbine blades.

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