Control system for aircraft anti-icing

A control system for aircraft anti-icing is disclosed including a conduit coupled at a first end to a source of hot high-pressure bleed air, a control valve in fluid communication with the conduit and an injector head, wherein the control valve is in electronic communication with a controller and configured to regulate the flow of bleed air between the conduit and the injector head, and a first sensor in electronic communication with the controller and configured to report a first data. The system may initialize a control valve to an initial regulated pressure. The system may determine a control temperature and control the control valve based on the control temperature, the first data, and a set value.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of India Patent Application No. 201841041587 titled, “CONTROL SYSTEM FOR AIRCRAFT ANTI-ICING” filed, Nov. 2, 2018. All of the contents of the previously identified application are hereby incorporated by reference for any purpose in their entirety.

FIELD

The disclosure relates generally to vehicles and machinery and, more specifically, to anti-icing systems including bleed air circulation to be used with aircraft and aircraft engines.

BACKGROUND

In operation, a gas turbine engine nacelle may experience conditions in which icing may occur. For example, an engine nacelle of an aircraft, as well as other parts of the aircraft such as the wing leading edge, may experience the formation of ice when operating in cold or below-freezing temperatures. The formation of such ice may dramatically alter one or more flight characteristics of the aircraft. For example, the formation of ice may deleteriously affect the aerodynamics of the aircraft and add additional undesirable weight, as well as generate a hazard when such ice breaks off and potentially strikes another portion of the aircraft. For example, ice breaking loose from the leading edge of the gas turbine engine nacelle inlet may be ingested by the gas turbine engine and thereby severely damage the rotating fan, compressor, and turbine blades.

SUMMARY

In various embodiments, a control system for aircraft anti-icing is disclosed comprising a conduit coupled at a first end to a source of hot high-pressure bleed air, a control valve in fluid communication with the conduit and an injector head, wherein the control valve is in electronic communication with a controller and configured to regulate the flow of bleed air between the conduit and the injector head, a first sensor in electronic communication with the controller and configured to report a first data, and a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the controller, cause the controller to perform operations comprising: initializing the control valve to an initial regulated pressure, determining a control temperature, and controlling the control valve based on the control temperature, the first data, and a set value.

In various embodiments, the system may receive a command signal and, in response, retrieve a Pupperlimitand a Plowerlimitand calculate the initial regulated pressure based on the Pupperlimitand Plowerlimit. In various embodiments, the first sensor is a first temperature sensor and the first data is a T1 data; wherein the system further comprises a second temperature sensor in electronic communication with the controller and configured to report a T2 data, and an ice detection sensor in electronic communication with the controller and configured to report a binary ice status, wherein the system may receive the ice status and an ambient temperature. The system may set the T2 data as the control temperature in response to a true ice status.

The system may compare the ambient temperature with an ambient temperature threshold and set the T2 data as the control temperature when the ambient temperature is less than the ambient temperature threshold. The system may compare the ambient temperature with the ambient temperature threshold and set the T1 data as the control temperature when the ambient temperature is greater than the ambient temperature threshold.

In various embodiments, the system may compare the control temperature to the set value. The system may increment the initial regulated pressure where the control temperature is less than the set value to generate a regulated pressure or decrement the initial regulated pressure where the control temperature is greater than the set value to generate the regulated pressure. The system may control the control valve to the regulated pressure. In various embodiments, the system may compare the regulated pressure to the Pupperlimitand the Plowerlimitand control the control valve to one of the Pupperlimitor the Plowerlimitbased on the comparison.

In various embodiments, the system may receive a disable command signal and, in response, control the control valve to a fully closed position. The system may receive an enable command signal and, in response, set the T2 data as the control temperature. In various embodiments, the first temperature sensor is coupled to an outer lipskin of a D-duct and the second temperature sensor is coupled to an inner lipskin of the D-duct.

DETAILED DESCRIPTION

In various embodiments and with reference toFIG. 1, a gas turbine engine10is provided and housed within a nacelle12, of which some components are omitted for clarity. Gas, such as air, enters the gas turbine engine10through an annular inlet section14, between the cap16(or spinner) of the engine and the annular inlet lip18or annular housing which constitutes the forward most section of the engine inlet housing20of nacelle12. Gas turbine engine may produce thrust by: (i) compressing a gas to a core air flow in a compressor section22forward of a combustor section23positioned with the gas turbine engine core, burning incoming core air flow and fuel within the combustor section23, and expanding the combustor exhaust through a turbine section24aft of the combustor section; and (ii) compressing and passing a large mass bypass air flow of inlet air through the fan section21of the gas turbine engine. Hot, high-pressure exhaust gases from the turbine section24of the engine10pass through exhaust outlet25and out the rear of the engine10. The compressed bypass fan air flows past the outside of the engine core within the engine nacelle cowl housing12and exits at the rear of the engine10.

In various embodiments and when operating in flight under icing conditions, ice may tend to form on the inlet lip18of nacelle12. The ice may alter the geometry of the inlet area between the inlet lip18and the spinner16tending thereby to disrupt airflow within annular inlet section14and reducing gas turbine engine10performance. In various embodiments, ice may periodically break free from these components and may be ingested into fan section21or compressor section22tending thereby to damage internal components of engine10such as, for example, stator vanes, rotor blades, radiators, ducting, etc.

In various embodiments and with additional reference toFIGS. 2 and 3, an anti-icing system may comprise a conduit26coupled at a first end28to a bleed air source of gas turbine engine10which provides relatively hot, high pressure, bleed air. In various embodiments, the bleed air source temperature may be between 150° F. [65° C.] and 1400° F. [760° C.] and the source pressure may be between 10 psig [0.6 bar] and 500 psig [34.5 bar]. The other end of conduit26passes through inlet housing20and penetrates D-duct300through a bulkhead302which encloses a quantity of air within the annular space created by bulkhead302and inlet lip18. Conduit26is fluidly coupled to an injector head304which extends into D-duct300from bulkhead302. D-duct300may extend a distance L between bulkhead302and the leading edge310of inlet lip18. Body306of injector head304comprises one or more nozzles312and may extend into D-duct300a distance D between 30% of L and 70% of L. In various embodiments, body306may comprise between one or more nozzles312.

In various embodiments and with additional reference toFIGS. 4A and 4Bdetails of D-duct300of the anti-icing system are shown illustrating circulating D-duct flow400.FIG. 4Aillustrates a schematic perspective of the D-duct proximate the injector head304andFIG. 4Billustrates a simplified D-duct flow field corresponding toFIG. 4A. Cool, moisture-laden, free-stream air scrubs the exterior of the inlet lip18skin, with impinging super-cooled droplets tending to accumulate as ice. Injector head304injects the bleed air through the nozzles312into the mass of air within the D-duct300and jet flow408from nozzles312entrains the air mass to induce flow400in a rotational circulatory motion. The relatively hot and high pressure bleed air mixes with mass of air within the D-duct300to increase the temperature of the D-duct air mass to an intermediate temperature sufficient to preclude the formation of ice along inlet lip18. In various embodiments, the injector head304may be oriented with a centerline of nozzles312and/or an injector head face relatively tangential to the curve of the D-duct300.

In this regard, bleed air exiting the nozzles may graze the inner lipskin404before eventually impacting the interior surface of the inlet lip18. Bleed air exiting the nozzles312may impact an area of the interior surface of inlet lip18in line with the jet flow408from nozzles312, tending thereby to elevate the temperature of the impact area generating a hot spot410relative to the remaining area of the inlet lip18. In various embodiments, the hot spot410may exceed 500° F. over an area of the outer lipskin402and tend to induce thermal stress relative to the surrounding relatively colder areas thereby promoting metal fatigue, cracking, and/or buckling of the outer lipskin402. Stated another way, generating a hot spot410may tend to exceed a material limit of the lipskin material. In this regard, generating a hot spot tends to degrade lipskin lifetime and may thereby degrade performance of the anti-icing system.

As bleed air is injected via injector head304, a portion of D-duct flow400may recirculate within D-duct300while a portion of D-duct flow400may exit the D-duct300through exhaust ports308to the atmosphere. At steady state, the hot air injection inflow into the D-duct through the injector head equals outflow of spent air through the exhaust ports308. In various embodiments, ejector-like pumping within enclosed geometry of the D-duct300results in the circulating flow400inside the D-duct300which may be several times larger than the injection flow rate. Stated another way, the resulting circulating flow400may be described as a self-communicating ejector wherein the D-duct flow being pumped in the nozzle region circulates around within the inlet lip, to once again re-enter the nozzle region. Circulation enhances heat transfer, but skews velocity towards the outer lipskin402, thereby favoring of heat rejection to outer lipskin402. Stated another way, the circulating flow400inside the D-duct tends to result in a higher speed flow near the outer lipskin402of the inlet lip18and a lower speed flow near the inner lipskin404of inlet lip18. The magnitude of the circulating flow may be limited by D-duct wall friction and drag at the injector head304. In various embodiments, the slowest flow is observed proximate the corner406between the inner lipskin404and the bulkhead302. In various embodiments, corner406may comprise an acute angle tending to benefit heating of the inner lipskin404toward a throat station of the inlet.

With additional reference toFIGS. 5A and 5B, body geometries and orientations of an injector head304are shown with relation to bulkhead302. Body306of injector head304extends from bulkhead302along a perpendicular centerline500that is perpendicular to the bulkhead302. In various embodiments, body306may be oriented at an angle α relatively away from the centerline. Stated another way, body306may be “bent” proximate the penetration point502at bulkhead302. In like regard and in various embodiments, body306may be rotated to an angle β relative to a perpendicular plane extending from bulkhead302. Bulkhead has a height H defined between an inboard edge504and an outboard edge506and the penetration point502may be located between 30% to 70% of distance H as taken from the inboard edge504(proximate the inner lipskin404).

With additional reference toFIG. 6a block diagram for a control system600for aircraft anti-icing is illustrated. Control system600includes controller602, sensors604which may include ice detector612, control interface606, database608, and control valve610.

Controller602may comprise at least one computing device in the form of a computer or processor, or a set of computers/processors, although other types of computing units or systems may be used. In various embodiments, controller602may be implemented as and may include one or more processors and/or one or more tangible, non-transitory memories and be capable of implementing logic. Each processor may be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. Controller602may comprise a processor configured to implement various logical operations in response to execution of instructions, for example, instructions stored on a non-transitory, tangible, computer-readable medium configured to communicate with controller602. In various embodiments, controller602may be integrated into computer systems onboard an aircraft, such as, for example a Full Authority Digital Engine Control (FADEC) system.

System program instructions and/or controller instructions may be loaded onto a non-transitory, tangible computer-readable medium having instructions stored thereon that, in response to execution by a controller, cause the controller to perform various operations. The term “non-transitory” is to be understood to remove only propagating transitory signals per se from the claim scope and does not relinquish rights to all standard computer-readable media that are not only propagating transitory signals per se. Stated another way, the meaning of the term “non-transitory computer-readable medium” and “non-transitory computer-readable storage medium” should be construed to exclude only those types of transitory computer-readable media which were found in In Re Nuijten to fall outside the scope of patentable subject matter under 35 U.S.C. § 101.

Controller602is in electronic communication with sensors604which may be coupled to or in electronic communication with gas turbine engine10and the anti-icing system. Sensors604may comprise a temperature sensor, a torque sensor, a speed sensor, a pressure sensor, a position sensor, an accelerometer, a mass flow sensor, or any other suitable measuring device known to those skilled in the art. Sensors604may be configured to measure a characteristic of an aircraft system or component such as gas turbine engine10. In various embodiments, sensors604include a first temperature sensor T1, a second temperature sensor T2, and an ice detection sensor612.

Sensors604may be configured to measure, for example, a lipskin temperature, a shaft speed, a flow rate, a pressure, a control valve position, an ambient temperature, a compressor exit temperature, an ice condition, and/or the like. Sensors604may be configured to transmit the measurements to controller602, thereby providing sensor feedback about the aircraft system to controller602. The sensor feedback may be, for example, a speed signal, or may be position feedback, temperature feedback, pressure feedback and/or other data. In various embodiments, T1 may be mounted on the outer lipskin402proximate hot spot410and may provide temperature feedback of the relatively hot area of the outer lipskin402. In like regard, T2 may be mounted on the inner lipskin404proximate exhaust ports308and thereby provide temperature feedback of a relatively cold area of the inner lipskin404.

Database608may be configured to communicate with controller602and to store and maintain data such as sensor data616, configuration settings, temperature response models, and/or the like. Database608may be in operative and/or electronic communication with controller602, sensors604, and control interface606. Data may be stored or recalled from database608in response to commands from controller602. Data may be stored in database608using any suitable technique described herein or known in the art. In various embodiments, configuration settings may include a control valve pressure regulation upper limit (Pupperlimit), a control valve pressure regulation lower limit (Plowerlimit), and a lipskin temperature setting (set value). In various embodiments, the set value may be between 35° F. [1.6° C.] and 500° F. [260° C.] or may be between, 50° F. [10° C.] and 400° F. [205° C.], or may be between 50° F. [10° C.] and 100° F. [38° C.]. The Pupperlimitand Plowerlimitmay be calculated analytically. For example, Pupperlimitmay be calculated based on a worst case icing condition and the Plowerlimitmay be calculated based on a worst case dry air condition (i.e. a worst case non-icing condition).

In various embodiments, controller602may be in electronic communication with a pilot of an aircraft through a control interface606such as, for example, a switch panel in a cockpit of the aircraft. The control interface606may display a status of the controller602and/or other system element status or may display measurements of sensors604. Control interface606may provide command signals614to controller602. In various embodiments, the command signals may be of the form ‘ENABLE, ‘DISABLE’, or ‘AUTOMATIC’.

Control valve610may be in electronic communication with controller602and be configured to be controlled by controller602. Control valve610may be a pressure regulator in fluid communication between the bleed air source and the conduit26feeding injector head304. In this regard, controller602and control valve610may control the pressure of bleed air injected into D-duct300by injector head304and thereby control the temperature of the inner lipskin404and the outer lipskin402. In various embodiments, controller602may receive a DISABLE command signal and in response command the control valve610to a fully closed position.

With additional reference toFIGS. 7A and 7B, a process flow700for temperature control in a control system for aircraft anti-icing is illustrated. The controller may determine an initial regulated pressure (Preg) based on the configuration settings and initialize the control valve to the initial regulated pressure (step702). Step702includes receiving by controller602one of the ENABLE or AUTOMATIC command signals614from control interface606. Step702includes retrieving by controller602the Pupperlimitand Pupperlimitfrom database608and calculating the Pregbased on the Pupperlimitand Plowerlimit. Step702includes controller602controlling the control valve610to output the Pregpressure.

In response to initializing the control valve610, the controller602may determine a control temperature and may control the control valve based on the control temperature and the set value. Controller602may receive sensor data616from ice detection sensor612including a binary ice status (e.g. indicating a presence or absence of at least some ice) and may select the T2 control temperature based on the true ice status (step704). In response to the false ice status, controller602may receive an ambient temperature data and may select the T2 control temperature when the ambient temperature data is below an ambient temperature threshold or select the T1 control temperature when the ambient temperature is above the ambient temperature threshold (step706). In various embodiments, the ambient temperature threshold may be about 32° F. [0° C.]. In various embodiments, the set value may vary based on the selecting the T1 or the T2 control temperature. For example, a T1 set value (i.e., a first set value) may be based on a dry air material temperature limit whereas a T2 set value (i.e., a second set value) may be based on a component ice thickness limit and controller602may select the first set value or the second set value in response to determining the control temperature.

In various embodiments, controller may select the T2 control temperature in response to receiving the ENABLE command signal. In response to selecting the T2 control temperature, controller602may receive the T2 temperature data and compare the T2 temperature data with the set value (step708). Controller602may control the control valve610based on the comparison between the T2 temperature and the set value. Where the T2 temperature is greater than the set value, controller602may decrement the Pregpressure (step710). In response to decrementing the Pregpressure, controller602may compare the Pregpressure with the Plowerlimitand based on the comparison return to step708when Pregis greater than the Plowerlimit(step712) or set Pregpressure to equal the Plowerlimitand return to step708(step714). In like regard, where the T2 temperature is less than the set value, controller602may increment the Pregpressure (step716). In response to incrementing the Pregpressure, controller602may compare the Pregpressure with the Pupperlimitand based on the comparison return to step708when Pregis less than the Pupperlimit(step718) or set Pregpressure to equal the Pupperlimitand return to step708(step720).

In various embodiments, in response selecting the T1 control temperature controller602may receive the T1 temperature data and compare the T1 temperature data with the set value (step722). Controller602may control the control valve610based on the comparison between the T1 temperature and the set value. Where the T1 temperature is greater than the set value, controller602may decrement the Pregpressure (step724). In response to decrementing the Pregpressure, controller602may compare the Pregpressure with the Plowerlimitand based on the comparison return to step722when Pregis greater than the Plowerlimit(step726) or set Pregpressure to equal the Plowerlimitand return to step722(step728). In like regard, Where the T1 temperature is less than the set value, controller602may increment the Pregpressure (step732). In response to incrementing the Pregpressure, controller602may compare the Pregpressure with the Pupperlimitand based on the comparison return to step722when Pregis less than the Pupperlimit(step730) or set Pregpressure to equal the Pupperlimitand return to step722(step734).