GB2084655A - Multi-application turbo engine control - Google Patents

Abstract

A basic hydromechanical fuel control for a turbofan engine is adapted to other configurations such as turboprop and turboshaft engines by removable adapter elements in the form of cylindrical ported plugs 48, 50, 52. In this way the basic control has the control elements common to all configurations, including throttle valve 8, pressure regulator 12 and condition responsive valve 30, and the adapter elements supply the uncommon elements specific to a particular configuration. <IMAGE>

Description

SPECIFICATION Multi-application turbo engine control This invention relates to hydromechanical fuel controls for multi-configuration gas turbine engines.

To operate more efficiently, small turbofan, tur bodrop and turboshaft engines will require more sophisticated control systems. The hybrid systems combining hydromechanical controls with electronic digital controls appears to be the most probable. A basic system having high commonality between turbofan, turbodrop and turboshaft engines is desir able and could then be applicable to all forms of engine with a minimum of change.

Several engine types have many common requirements such as the safe limits defined by the hydromechanical unit a manual backup, acceleration and deceleration limiting and overspeed protection.

For all these the basic unit provides the necessary or common components. The turbofan may require a core speed control, a fan speed sensor and/or a compressor bleed control as the uncommon elements. The turboprop requires core speed control, power rating, propellar speed control and automatic feather or reverse pitch control elements, certain of which are not required for the other types of engine.

The turboshaft requires free turbine governing, available power display, rotor compensation and torque limits and mechanisms to accomplish these results must be incorporated in the basic control in adapting it for a turboshaft engine.

A hybrid system utilizing a basic hydromechanical system and adapted for turbofan engines is known and has been extensively tested in service. One form of this system is described in the co-pending application of Stearns, Serial No. 069,141, filed August 23, 1979 having a common assignee with this application. Adaptation of a known form of control such as this to all types of turbo engines would minimize design, manufacture and testing problems and expense.

A characteristic of this basic fuel control is that without any impairment engine operation can continue without the electronic control unit. The hydromechanical control establishes the minimum flow to the engine necessary for acceleration and deceleration all in response to the movement of the power level. The electronic unit modifies the basic flow in response to certain engine and environmental parameters; thus the reliability of a hydromechanical system is provided and in the present invention the system is adaptable to any ofturbojet, turboprop or turboshaft engine configurations.

A feature of this invention is a fuel control readily adaptable to any of the several types of engines by one or more adapters for the particular type involved.

Another feature is the incorporation in the main control housing of recesses for the insertion of appropriate plugs which direct fuel flow or pressure sense lines such that scheduling may be accomplished for any particular type of engine.

A particular feature is a hydromechanical control that is adaptable for the several engine types in conjunction with an electronic control unit with the conversion to any type of engine effected by the selection and positioning of adapters that permit scheduling for any engine application.

According to the invention, the main fuel metering housing is designed to permit the attachment to or insertion in the housing of adapter elements that route fuel flow or pressure sense lines either simply or through restrictive orifices and/or selective valves to accomplish scheduling for each engine application. More particularly, the main housing has a plurality of recesses therein in which are positioned plugs that serve to control the fluids through these plugs to accomplish the necessary change in the fuel functioning for adaptation to another type ofturbo engine.That is to say the basics of the fuel control are so arranged that the elements common to the several engine configurations are fixed and the elements that are uncommon, that is, peculiar to a particular engine type, can be inserted into the basic arrangement as needed to adapt the overall system for a specific type of engine.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments and accompanying drawings.

Fig. lisa diagrammatic view of the fuel control with parts in structural detail to show the invention as applied to a turbofan engine.

Fig. 2 is a detail of a part of Fig. 1 as modified to adapt it to a turboprop engine.

Fig. 3 is a view similar to Fig. 2 but with the structure adapted for a turboshaft engine.

Fig. 4 is an elevational view of one of the adapter plugs.

Fig. 5 is a diagrammatic view of a detail.

Fig. 6 is a diagrammatic view of another detail.

Fig. 7 is a diagram of the scheduling accomplished for a turbofan engine at one altitude.

Fig. 8 is a diagram similar to Fig. 7 for a turboprop engine at one altitude.

Fig. 9 is a diagram similar to Fig. 7 for a turboshaft engine at one altitude.

The diagrammatic showing of Fig. 1 represents the structure incorporated in the main fuel housing. The part shown in structural detail including the elements necessary to adapt the control to any one of the several engine types. The basic diagram is essentially similar to that already described and claimed in Stearns co-pending application Serial No.

069,141 above identified and reference is made to that application for any greater detail if necessary.

Fuel is supplied to an inlet port 2 and discharged from an outlet port 4 to the engine. The fuel flow in conduit 6 reaches the power level valve or throttle valve 8 and through line 10 to the pressure regulator valve 12 that serves to maintain the desired pressure drop across the throttle valve. The throttle valve 8 Is connected to a potentiometer 14 that delivers a signal by leads 16 to the connection 18 for the electronic control unit 20. This unit is not a part of the present invention; it serves to control the operation of the hydromechanical control as a function of engine parameters or environmental parameters.

The throttle valve is connected to the pilot lever 22.

From this valve fuel may go directly to the engine through lines 24 and 26 in the configuration of Fig. 1.

The adapter 27 through which this fuel flows will be described later. This line carries the minimum flow to the engine as established by the throttle valve.

The power lever or throttle valve also regulates flow through line 28 to a condition responsive valve 30. The position ofthis valve 30 is controlled by a servo 32 actuated in response to compressor discharge pressure. From this valve, fuel flows through line 33 to the line 26 to the engine. Another line 34 from the line 6 upstream of the power lever valve reaches the condition responsive valve 30. The details of this valve 30 are described in the aboveidentified application.

As above stated, the invention involves a system by which to adapt the main control described in general above to the several types of turbine engines. To accomplish this the main fuel housing 40, only a portion of which is shown structurally, has a plurality of cylindrical recesses 42,44 and 46 therein, to receive selective plugs 48,50 and 52 for the turbofan arrangement of Fig. 1. These plugs are removable and may be replaced by other plugs 54, 56 and 58 as shown in Fig. 2for the turboprop engine and other plugs 60, 62 and 64 for the turboshaft engine as shown in Fig. 3.

Thus in a turbojet configuration the arrangement is such that there are three circuits supplying fuel to the engine. The first circuit is through the throttle and condition response valves in series. The second is solely through the condition responsive valve. The third is solely through the throttle valve and serves as a minimum flow control. Thus with the structure shown with the plugs as in Fig. 1, the power lever angle can establish the hydraulic control limits as shown in Fig. 7 in which the shaded area represents the hydraulic control authority limit.

For the turbofan configuration, the fuel is directed from line 24 to line 26 through a passage 66 in plug 48. Thus, this plug serves only as a direct connection from the throttle valve to the engine in this configuration.

The fuel control also includes a torque motor 68 to which the electronic control supplies a signal through leads 70. The torque motor includes a flapper valve 72 that is opened or closed by the electronic signal. This motor is connected to fuel line 6 by a line 74 and as the valve 72 opens, fuel under pressure passes this valve to line 76 leading to fuel line 26 to the engine thus increasing the pressure drop across the metering orifices in the throttle valve 8. The pressure in line 76 is fed back to the regulating valve 12 through line 80 from line 76 to recess 46, a passage 82 in plug 52, a cross passage 84 from recess 46 to recess 44, passage 86 in plug 50 and a line 88 to the valve 12. A damping orifice 90 is in line 88 close to the valve 12.

Thus, by placing appropriate plugs 50 and 52 in the recesses 44 and 46, a connection is made from the torque motor to the regulating valve so as to maintain the appropriate pressure at the inlet to the throttle valve. A line 92 from line 88 leads to a recess 96 in the fuel housing. This recess in Fig. 1 has a plugged insert 98 therein for the configuration of Fig.

1.

In the turboprop configuration the eiectrical and hydromechanical control limits are generally the same as above but the added feature of a reverse authority is added. To accomplish this the plug 54 has a three-way passage 102 therein connecting line 24 to line 26 through an orifice 104 and also connecting line 24 to cross passage 106 between recesses 42 and 44.

The plug 56 also has a transverse passage 108 therein connecting cross passages 84 and 106 and connecting passage 110 to line 88. In passage 108 is an orifice 112 and check valve 114 upstream of the passage 110 and another orifice 116 downstream of passage 110. This plug is referred to as the most selector plug.

In recess 46 there is a plug 58 that has a transverse passage 118 and the connecting passage 120. Passage 118 has two check valves 122 and 124 therein on opposite sides of passage 102 and arranged to permit flow from passage 102 in both directions in passage 118. The transverse passage 118 at one end communicates with line 80 and at the other end with a line 126 to the acceleration flow line 28 between the throttle valve and the condition responsive valve 30. The cross passage connects to line 84 to deliver control pressure fluid through plug 56 to line 88. This is the limit selector plug.

One further change is made for the turboprop engine. The insert 98 has a check valve 130 placed in the passage 99 therein and this valve 130 is opened by an arm connected to the engine condition lever 134. When this condition lever is moved in the off direction, it drops the pressure in line 88 to shut off fuel by dropping the pressure on the end of the regulating valve 12. This shut off is necessitated to provide for the reversability of the prop.

With this arrangement pressure from fuel line 24 is transferred through plugs 54 and 56 to pressure line 88 thus changing the pressure on the end ofthe regulating valve 12. This same pressure from line 26 passes through plug 58 to line 126 and also to line 76. By this arrangement, the pressure reaching the regulating valve is determined by the pressure downstream ofthetorque motor valve 72 orthe pressure in accelerator line 28 whichever is the least.

As these pressures become less than the pressure in line 24, the most selector plug takes over and the pressure in line 24 is transmitted to the relief valve.

With this valve arrangement the hydromechanical control obtains the desired fuel flow by altering the pressure on the pressure regulating valve. The check valve 130 in insert 98 also permits changing the balancing pressure in the pressure relief valve by movement ofthe condition level 134.

In converting to the turboshaft configuration of Fig. 3, the plugs 60,62 and 64 are placed in the three recesses as shown in this figure. Plug 60 has a connecting passage 136 comparable to the passage in valve 48 connecting lines 24 and 26. A transverse passage 138 connects with passage 136 and also with a connecting passage 140 that lines up with cross passage 106 in the housing. There are orifices in passage 138 on both sides of the passage 140.

Plug 62 is the same as plug 58 with a transverse passage 118 and connecting passage 120 and the two check valves 122 and 124. Plug 64 has a passage 142 connecting cross passage 84 in the housing to line 126 to the accelerator line 28 and a transverse passage 144 connecting with passage 142 and establishing fluid connection from line 80 to line 126.

This passage 144 has a restriction 146 therein. With this arrangement, the power lever may be set in run position and the electronic control can change fuel flow over the entire range. In the event of an electronic unit failure, the control has the torque motor 70 replaced by a stepper motor 150 that actuates a flapper valve 152 comparable to valve 72 of Fig. 1.

This stepper motor is designed to stay at the last position commanded upon electronic unit failure and permits pilot control with appropriate power level setting.

With this arrangement pressure from fuel line 24 is transferred through plugs 54 and 56 to pressure line 88 thus changing the pressure on the end of the regulating valve 12. This same pressure from line 26 passes through plug 58 to line 26 and also to line 76.

By this arrangement the pressure reaching the regulating valve is determined by the pressure downstream ofthetorque motor valve 72 or the pressure in accelerator line 28 whichever is the least. As these pressures become less than the pressure in line 24 the most selector plug takes over and the pressure in line 24 is transmitted to the regulating valve. With this valve arrangement the hydraulic control obtains the desired fuel flow by altering the pressure on the pressure regulating valve. The check valve 130 in insert 98 also permits changing the balancing pressure on the pressure regulating valve by movement of a condition level 134.

With this arrangement the minimum fuel flow pressure in line 24 and the pressure in line 6 pass the restrictions in line 60 and the higher of the two pressures is transmitted to plug 62. In plug 64 the pressure in accelerator line 28 and the pressure in line 76 as modified by restriction 146 is transmitted to plug 62. The least selector plug 62 selects the lower of these pressures by the check valves as the operating pressure in line 88 to the pressure regulating valve.

It will be understood that the passages, valves and restrictions in the plugs shown in Figs. 1-3 are diagrammatic. Each plug is constructed to provide the desired structural arrangement to accommodate the necessary functions. For example, as shown in Fig.

4, the plug 48 may have an axial passage 160 and communicating axially spaced passages 162 and 164 entering peripheral grooves 166 and 168 in the plug.

Axially spaced O-rings 170 between the grooves 166 and 168 and nearthe ends of the plugs prevent leakage of any fluid axially. In this arrangement the plug need not be oriented in the recess. Obviously the other plugs will be so constructed that orientation is unecessary.

As shown in Fig. 7 for a turbofan engine, the electronic control sets fuel flow only about a selected hydromechanical valve unit fuel setting. If the electronic control unit fails, full power is obtained by extending the power lever to the overtravel range.

Fuel flow can be reduced to nearly idle by reduction of the power lever regardless of the mode of failure of the electronic control unit. This shows the fuel flow at one altitude and these schedules will change at other altitudes.

As shown in Fig. 8, the electronic control unit and hydromechanical units are the same as in Fig. 7 but the selector valves insure the engine is controlled by the electronic control unit or the hydromechanical unit but not both; with the additional feature of a reverse authority added. Failure is the same as in Fig. 7. Shut off is implemented because of the reverse feature by the addition of one condition lever shut off feature above described.

The turboshaft gives full range of fuel authority to the electronic control unit as well as to the hydromechanical unit. The power lever of the hydromechanical unit is placed in run position and the electronic control unit changes power over full range. The authority of the electronic control can be limited by the power lever angles below the run position. To prevent a full excursion of engine speed in the event of an electronic control unit failure, the pilot can then select an appropriate setting with the power lever angle.

Although the torque motor and the stepper motor are above described as usable in specific engine con figurations, it will be understood that either one may be utilized as desired dependent upon the desired response to an electronic control unit failure. That is to say, if the electronic failure is intended to be at a given fuel ratio then the torque motor will be used.

However, if the stepper motor is utilized then the electronic control unit failure is stopped in whatever engine control position the failure occurs.

Although this invention has been shown and described with respect to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.

Claims (12)

1. Afuel control adapted for various different gas turbine configurations including: a housing having a plurality of cylindrical recesses therein; a plug removable positioned in each of said recesses; a fuel flow valve in said housing, said housing having inlet and outlet passages for flow to and from said valve, said outlet passage intersecting at least one of said recesses; pressure-responsive means in said housing and a passage in said housing for pressure supply to said means, said passage intersecting at least one of said recesses; and means in said plugs for directing flow therethrough in selected modes.

2. Afuel control as in claim 1 in which at least some of the plugs have restrictive orifices therein.

3. Afuel control as in claim 1 in which at least some of the plugs have restrictive orifices therein.

4. A fuel control as in claim 1 in which at least some of the plugs are replaced by other plugs in adapting the control to a different engine configuration.

5. A fuel control adapted for different gas turbine configurations including: a housing; removable means forming a part of said housing, said means and said housing having common interfaces; a fuel control valve; at least one fuel flow circuit from said valve to an outlet port, said circuit extending through said removable means; a pressure-responsive device in said housing; at least one pressure flow circuit including said pressure-responsive device and extending through said removable means; and said removable means having means therein for directing fuel flow and pressure flow in selected modes in the passages therein.

6. Afuel control as in claim 5 in which there is a second removable means adapted for substitution for the first removable means, said second removable means having means therein for directing fuel flow and pressure flow in a different selected mode than in the first removable means.

7. Afuel control as in claim 5 in which said pressure flow and fuel flow through said removable means includes restrictive orifices and selective flow valves therein.

8. A fuel control device shaped for different gas turbine configurations including: a housing; a fuel flow metering valve in said housing having inlet and outlet passages for fuel flow through the device; a condition-responsive valve in said outlet passage; a pressure regulating valve for said fuel flow pressure through the metering valve; and a plurality of cylindrical recesses in said housing, said outlet passage intersecting one of said recesses and a plug removable positioned n each of said recesses, said housing having pressure passages therein for directing fluid under pressure to and from said pressure regulating valve, said pressure passages intersecting other of said recesses and means in the plugs in said other recesses for directing flow therethrough in selected modes.

9. A fuel control device as in claim 8 in which there are other pressure responsive means in the housing, and passages to said means that intersect at least one of said recesses.

10. Afuel control device as in claim 8 in which some of the plugs have restrictive orifices therein.

11. Afuel control device as in claim 8 in which at least some of the plugs have selected flow control valves therein.

12. Afuel control device as in claim 8 in said plugs are interchangeable one with another to adapt the control to a selected engine configuration.