Cowling inlet for sideward airflow

An exemplary vertical takeoff and landing includes a rotor driven by an electric motor, a generator located in a compartment and electrically connected to the electric motor, and an inlet formed through a side of the compartment to direct sideward airflow across the generator.

BACKGROUND

Rotorcraft heat-generating components, such as gearboxes and engines, are located within a compact engine compartment. The heat-generating components may require liquid cooling systems and some may be cooled by the natural airflow that circulates through the engine compartment during flight.

SUMMARY

An exemplary apparatus includes a compartment of an aircraft, a heat-generating component located in the compartment, and an inlet formed through a side of the compartment. An exemplary vertical takeoff and landing includes a rotor driven by an electric motor, a generator located in a compartment and electrically connected to the electric motor, and an inlet formed through a side of the compartment to direct sideward airflow across the generator.

An exemplary method includes directing a sideward airflow into a compartment of an in-flight vertical takeoff and landing aircraft to cool a heat-generating component inside of the compartment, wherein the sideward airflow is directed through an inlet in a side of the compartment.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various illustrative embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. For example, a figure may illustrate an exemplary embodiment with multiple features or combinations of features that are not required in one or more other embodiments and thus a figure may disclose one or more embodiments that have fewer features or a different combination of features than the illustrated embodiment. Embodiments may include some but not all the features illustrated in a figure and some embodiments may combine features illustrated in one figure with features illustrated in another figure. Therefore, combinations of features disclosed in the following detailed description may not be necessary to practice the teachings in the broadest sense and are instead merely to describe particularly representative examples. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not itself dictate a relationship between the various embodiments and/or configurations discussed.

In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “inboard,” “outboard, “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. As used herein, the terms “connect,” “connection,” “connected,” “in connection with,” and “connecting” may be used to mean in direct connection with or in connection with via one or more elements. Similarly, the terms “couple,” “coupling,” and “coupled” may be used to mean directly coupled or coupled via one or more elements.

FIG. 1illustrates an exemplary vertical takeoff and landing (VTOL) aircraft10incorporating a cowling inlet12for sideward airflow according to an embodiment of the disclosure. VTOL aircraft10has a fuselage14and a rotor system16carried thereon. Blades18are operably associated with rotor system16for creating flight. A tail boom20includes one or more tail rotors22that may be a component of an anti-torque system24.

Tail rotor22may provide thrust in the same direction as the rotation of blades18to counter the torque effect created by blades18. Blades18rotate clockwise inFIGS. 1 and 2. In some embodiments, the main rotor blades rotate counterclockwise. Teachings of certain embodiments recognize that tail rotors22may represent one example of an anti-torque rotor; other examples may include, but are not limited to, push propellers, ducted tail rotors, and ducted fans mounted inside and/or outside the tail boom. Anti-torque system24may include two or more tail rotors arranged for example in an electric distributed anti-torque system.

Aircraft10includes a propulsion system26to drive the rotor system16and tail rotor22. The exemplary propulsion system26depicted inFIG. 1includes a gearbox28connected to blades18via main rotor mast30. One or more combustion engines32are connected to the gearbox28. In this example, propulsion system26is a hybrid propulsion system including an electric motor34to drive tail rotor22. One or more generators36are electrically connected to electric motor(s)34for example by conductors38. Generator36is driven by engine32through gearbox28inFIG. 1. In this example, generator36is connected directly to gearbox28, which is the main rotor gearbox. Generator36may be connected to the main rotor gearbox through an accessory gearbox. In some embodiments, generator36is connected directly to engine32. Propulsion system26may be a hybrid system as illustrated inFIG. 1or a traditional fuel-fired combustion system or an all-electric system.

Fuselage14includes a compartment40covered or enclosed by a cover or cowling42. Heat-generating components such as generator36and combustion engine32are located inside of compartment40. Cowling inlet12is an opening through a side of cowling42relative to the forward flight direction and directed into sideward airflow44(FIG. 2). Cowling42may include a top surface, front surface, rear surface, right side surface, and left side surface. The side surfaces extend in a generally vertical direction. Cowling inlet12may be a passive, always remaining open, or it may be selectively opened and closed. Cowling inlet12is illustrated on the right side of compartment40; however, it may be on the left side.

In some embodiments, generator36is located proximate to mast30and forward of mast30to position the generator's weight proximate the center of gravity of aircraft10and to counter the weight of engines32and motors34located aft of mast30. In the illustrated embodiments, cowling inlet12is located forward of mast30and axially aligned with generators36. In some embodiments, cowling inlet12may be positioned axially forward or aft of generators36.

FIG. 2illustrates a top view of another exemplary VTOL aircraft10according to one or more aspects of this disclosure described with additional reference to the other figures. Cowling inlet12is located in cowling42on the side of fuselage14facing sideward airflow44. Compartment40has a cowling outlet46. InFIG. 2, cowling outlet46is located on a side of compartment40opposite from inlet12. In an embodiment, cowling inlet12and cowling outlet46are axially aligned. Cowling outlet46may be located on a surface other than the side opposite from cowling inlet12. Sideward airflow44enters the compartment through open cowling inlet12and circulates out through cowling outlet46. A heat-generating component, or its cooling system, may be located in compartment40between cowling inlet12and cowling outlet46so that sideward airflow44is diverted to cool the heat-generating component. In some embodiments, cowling inlet12and cowling outlet46are not axially aligned but oriented such that sideward airflow44is diverted across the heat-generating components, or its cooling system. In some embodiments, cowling outlet46is not an opening through a side, but provided by an opening formed in another cowling surface, for example on the top surface at mast30or proximate engine exhaust48.

The maximum thrust and power required by anti-torque systems occurs in sideward flight or in hover with sideward airflow, typically limited to 35-knot sideward flight or airflow conditions. Electric anti-torque systems are sized to meet the maximum thrust required in sideward flight conditions and are therefore overdesigned for other flight conditions. For example, when aircraft10is in a cruise mode the anti-torque system may not need to be operated. Generators produce an extraordinary amount of heat and must be sized to provide the electrical power required by the motor(s) driving the anti-torque system. Generators are commonly air-cooled or liquid-cooled to prevent overheating. Air-cooled systems are generally implemented for smaller generators and liquid-cooled systems are implemented for larger generators.

Cowling inlet12is configured to harvest sideward airflow44to cool components of propulsion system26located in compartment40. In some embodiments, cowling inlet12is configured to harvest sideward airflow44to cool generator(s)36used in an electric anti-torque system24. Implementing cowling inlet12may permit using a smaller size generator, using an air-cooled generator as opposed to a liquid-cooled generator, and/or using a smaller size liquid-cooling system than would be required without cowling inlet12.

FIGS. 3-5illustrate exemplary diagrams of VTOL aircrafts10implementing cowling inlets12, which are described with additional reference to the other figures. Aircraft10includes generators36located in an compartment40covered by a cowling42. Cowling inlet12is formed through side50of cowling42oriented toward sideward airflow44. In the illustrated examples, aircraft10has an anti-torque system24using multiple tail rotors22arranged for example in an electric distributed anti-torque arrangement. Each tail rotor22includes an electric motor34and each electric motor34has an individual speed control52. Anti-torque system24includes a gearbox28connected to generators36. Generators36are electrically connected via conductors38to motors34. Generators36and motors34are connected for example to power management unit54and control computers56, which can be the flight control computer. A non-limiting example of an electric distributed anti-torque system is disclosed in U.S. Publication 2017/0349276, the teachings of which are incorporated herein by reference. AlthoughFIGS. 3-5illustrate multiple tail rotors22, aircraft10may implement a single tail rotor22.

Cowling inlet12, illustrated in theFIG. 3embodiment, is an active cowling inlet and includes a barrier58that can be moved between an open position and a closed position. Barrier58is shown in the open position inFIG. 3moved away from cowling inlet12to permit sideward airflow44to enter compartment40. Barrier58is illustrated as a planar member that may for example slide between the open position uncovering the opening and a closed position blocking the opening. Barrier58may take other forms, such as a hinged member that may pivot outward or inward from the cowling or a moveable louver. An example of an active cowling opening, cowling inlet12and/or cowling outlet46, is illustrated and described with reference toFIG. 6.

FIG. 3does not illustrate an outlet through side60of cowling42, and sideward airflow44may circulate out of compartment40through one or more outlet openings in cowling42, such as through the top or rear surface. In this example, side50is a right side relative to the direction of flight. Openings exist in the cowling for example around mast30, engine exhausts48, and vents. Cowling42may have a cowling outlet46located through side60as illustrated inFIG. 4. Generators36, illustrated inFIG. 3, are air-cooled as depicted by fins62. Generators36, in particular fins62, are positioned in a path80of sideward airflow44as it is diverted through cowling inlet12into compartment40. Cowling inlet12is axially aligned with generator36in this example to divert or direct sideward airflow44across generator36, in particular across the generator's cooling system, which are fins62in this example. In one or more embodiments, generator36is positioned in a path80between cowling inlet12and a cowling outlet46located on side60or another surface of cowling42.

FIG. 4illustrates an exemplary aircraft10implementing a passive cowling inlet12located on side50of cowling42. Passive cowling inlet12remains open and does not have an associated barrier to close the opening. In this example, a cowling outlet46is located on side60of cowling42axially aligned with cowling inlet12to promote the flow of sideward airflow44across generators36, which are positioned in path80between cowling inlet12and cowling outlet46. Although cowling outlet46is shown axially across from cowling inlet12it may be offset axially.

FIG. 5illustrates an exemplary aircraft10implementing an inlet12located on side50of cover42with a component cooling device64. In this example, generators36are liquid-cooled via heat exchangers64. In some embodiments, such as illustrated inFIG. 5, heat exchangers64are oriented generally perpendicular to path80of sideward airflow44through compartment40as directed through inlet12. In this illustrated embodiment, inlet12and outlet46are axially aligned with generator36via its cooling device, heat exchanger64. In some embodiments, outlet46may not be located on side60or not axially aligned with inlet12. In this example embodiment, inlet12and outlet46are both active openings, each having a barrier58that can be moved to change the cross-section of inlet12and outlet46. In some embodiments, inlet12and outlet46may be passive. An example of an active opening is described with reference toFIGS. 6 and 7.

FIG. 6illustrates an exemplary active opening in a compartment cover, described with reference to inlet12and with additional reference to the other figures. Inlet12is formed through side50of a compartment40. A control unit66, which may be a flight control computer, is connected to a sensor68that can measure a condition such as the velocity of sideward airflow44or a compartment40condition such as temperature. The measured temperature may be a temperature of compartment40or a temperature of a heat-generating component such as generator36. An actuator70is connected to barrier58to move it between an open position uncovering inlet12and a closed position blocking inlet12. Control unit66is connected to actuator70to control the movement of barrier58and the cross-section opening of inlet12. Inlet12may be opened and closed in response to pilot input through control unit66and or it may be opened and closed by control logic in control unit66. As will be understood by those skilled in the art with the benefit of this disclosure, an outlet may be operated in conjunction with active inlet12.

FIG. 7shows a flowchart of an example control logic72for opening and closing an opening such as inlet12and/or outlet46. It may be desired to close inlet12, and outlet46, in conditions in which an opening in the side of the covering42, e.g., fuselage, may introduce unnecessary drag. For example, in a normal cruise mode enhanced component cooling is not needed, there is not sufficient sideward airflow to be harvested, and an opening in the side of the fuselage may create unnecessary drag.

At block74, control logic72, which can be in control unit66, receives measurements of a condition from sensor68. The condition measured may be without limitation the velocity of sideward airflow44, a temperature of compartment40, or a temperature of a heat-generating component such as a generator. At block76, control logic72compares the measured condition to a trigger limit. At block78, control logic72moves barrier58to open or close inlet12in response to the comparison of the measured condition to the trigger limit. In some embodiments, an outlet46is opened and closed in conjunction with inlet12. In some embodiments, inlet12or outlet46is partially opened or closed at pilot discretion or based on control logic referencing measured conditions, such as sideward airflow velocity or generator temperature.

In an exemplary embodiment, the measured condition and the trigger limit are velocity of sideward airflow44. At block74, control logic72receives a measurement of the velocity of sideward airflow44. At block76, control logic72compares the measured velocity to the trigger limit velocity. At block78, control logic72moves barrier58from a closed position to an open position if the measured velocity is greater than the trigger limit or moves barrier58from the open position to the closed position if the measured velocity is less than the trigger limit.

The trigger limit can be selected based on various criteria. In accordance to some embodiments, the measured condition is the velocity of sideward airflow44and the trigger limit is a set at a value of approximately 35-knots or less than 35-knots. In an embodiment, the sideward airflow trigger limit is approximately 30-knots. In one embodiment, the sideward airflow trigger limit is approximately 25-knots. In one embodiment, the sideward airflow trigger limit is approximately 20-knots. In one embodiment, the sideward airflow trigger limit is approximately 15-knots.

An exemplary method includes directing a sideward airflow44into a compartment40of an in-flight vertical takeoff and landing (VTOL) aircraft10to cool a heat-generating component inside of the compartment, wherein the sideward airflow is directed through an inlet12in a side50of a cover42. An outlet46may be formed through an opposite side60of cover42. In an embodiment, inlet12is opened in response to a velocity of sideward airflow44exceeding a trigger limit velocity. In another embodiment, inlet12is opened in response to a temperature inside of compartment40. In another embodiment, inlet12is opened in response to a temperature of a component, e.g., generator36, located inside of compartment40. Opening and closing of inlet12and outlet46includes partial opening and closing to choke airflow through the orifice.

In an embodiment, an outlet46is formed through a side60of cover42and a generator36is positioned in a path80between inlet12and outlet46. Opening inlet12and outlet46, at block78, in response to a measured conditions, such as and without limitation, a velocity of the sideward airflow44, temperature of generator36, temperature in compartment40, being greater than a trigger limit and closing openings12,46in response to the measured condition being less than the trigger limit.