Patent Description:
Aircraft may include power generation using turbines in main engines. However, as a safety feature, or for other reasons, alternate power device (e.g., supplementary or backup units) may be arranged on aircraft to supply power (e.g., electric and/or hydraulic) to components of the aircraft, when needed. For example, a ram air turbine is deployable to generate power when sufficient primary power generation is not available. The ram air turbine typically includes a turbine that is deployed into an airstream along (e.g., external to) the aircraft. Rotation of the turbine drives a generator and/or hydraulic pump. The generator and/or hydraulic pump can be mounted at a pivot point of the ram air turbine that is a distance from the turbine deployed within the airstream. Accordingly, a drive arrangement including a gearbox is utilized to transfer power from the turbine to the generator and/or hydraulic pump. The drive arrangement includes a gearbox that provides a desired speed and direction for driving the generator and/or hydraulic pump. Gears, shafts, and other drive components are constrained by limitations in the desired size, weight, and power generation of the ram air turbine. However, ram air turbine systems add significant weight and when deployed cause significant drag on the aircraft. <CIT> describes an aircraft gas turbine engine comprising a generator.

According to a first aspect, a system according to claim <NUM> is provided.

According to a second aspect, a method according to claim <NUM> is provided.

It should be understood, however, the following description and drawings are intended to be illustrative and explanatory in nature and non-limiting.

As shown in <FIG>, an aircraft <NUM> typically includes one or more engines <NUM> for driving flight and powering the aircraft. The engines <NUM> are typically mounted on wings <NUM> of the aircraft <NUM>, but may be located at other locations depending on the specific aircraft configuration. In some aircraft, the engine(s) may be tail mounted, or housed within the body of the aircraft, or otherwise arranged as will be appreciated by those of skill in the art.

Each engine <NUM> of the aircraft <NUM>, regardless of location, may include one or more attached or connected generators, as appreciated by those of skill in the art. The generators may provide electrical power to various components of aircraft, as will be appreciated by those of skill in the art. In some configurations, the generators may be operably connected to an output shaft of the engine which drives a stator/rotor to generate electricity. In other configurations, a shaft from the engine may interface to a gearbox, and generators may be mounted, as an accessory, to the gearbox.

In addition to the power generated by the traditional or main engines (i.e., engines <NUM>), additional power generation systems may be arranged on an aircraft. One type of such alternative, backup, or supplemental power generation may be a generator coupled to the low spool primary fan of the engines <NUM>.

Turning now to an overview of technologies that are more specifically relevant to aspects of the disclosure, large, modern turbofan engines for aircraft include very large primary fan stages within the engine assembly. These fan stages typically operate in one of two speed ranges. These speed ranges include an active thrust speed where the engine fan is engaged and spinning at a high rate of speed. Another speed range includes a speed range referred to as wind milling when the engine has failed but the fan is still turning because the aircraft is still in flight. Aspects of the present disclosure provide for a generator coupled to the primary fan (sometimes referred to as the "low spool") that can serve in place of a ram air turbine (RAT) in a situation where the engine is in a wind milling speed range (i.e., when the engine has failed). During normal operations, the generator coupled to the primary fan generates a given normal operating voltage which typically is regulated by the magnetic field strength of a winding inside the generator. In a situation where the engine has failed, the speed of the primary fan drops significantly, but does not usually stop completely (i.e., wind milling).

In one or more embodiments, given the two speed ranges (e.g., normal operation and wind milling), a generator coupled to the low spool primary fan of a turbofan engine can provide two different voltage levels. <FIG> depicts a diagram of an exemplary turbofan engine with a generator coupled to the low spool primary fan according to one or more embodiments. The turbofan <NUM> is a type of airbreathing jet engine that is used in aircraft propulsion. The turbo portion refers to a gas turbine engine which achieves mechanical energy from combustion, and the fan, a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. The turbofan engine <NUM> includes a low spool primary fan <NUM> with airfoils (e.g., blades) that facilitate movement of air through the engine <NUM>. In addition, the airfoils can rotate responsive to airflow in the event that the aircraft is moving but the engine <NUM> is no longer working. The turbofan engine <NUM> also includes a gearbox <NUM> that can transmit power from the fan <NUM> to a generator within the gearbox <NUM>. In one or more embodiments, the gearbox <NUM> of the engine <NUM> is configured to receive and transmit rotation from the low spool primary fan <NUM> to a drive shaft. For example, the gearbox <NUM> may be configured to receive a turbine shaft driven by the rotation of the low spool primary fan <NUM> at a rotational velocity and convert the rotation to a different speed drive shaft rotation velocity. This drive shaft can be operably connected to the generator to generate power. The gear set within the gearbox <NUM> may provide increased or decreased rotational speeds for the generator depending on the specific application.

<FIG> depicts a system for dual voltage generation in an aircraft according to one or more embodiments. The system <NUM> includes a generator <NUM> which can be the generator operably connected to the low spool primary fan <NUM> (from <FIG>) and operated as described above to receive rotational speed from the fan <NUM>. The system <NUM> also includes a generator controller <NUM>, a rectifier <NUM>, a converter bypass switch <NUM>, a power converter <NUM>, and a load <NUM> being driven by the generator <NUM>. The rectifier <NUM> is electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The rectifier <NUM> can be any type of rectifier configuration including, but not limited to, half bridge or full bridge rectifier circuits. The rectifier <NUM> is configured to convert the AC voltage from the generator to a DC voltage to drive the load <NUM>. The output of the rectifier <NUM> is coupled to the converter bypass switch <NUM> which is controlled and operated by the generator controller <NUM>. The converter bypass switch <NUM> is operable to either pass the DC voltage directly to the load <NUM> or though a converter <NUM> connected to the load <NUM>. As described in greater detail below, the generator controller <NUM> operates the converter bypass switch <NUM> to either supply voltage to the converter <NUM> or bypass the converter <NUM> and supply voltage directly to the load <NUM>. In one or more embodiments, the converter <NUM> is a DC-to-DC step down converter which takes in a DC voltage and steps down (i.e., lowers) the voltage at the output of the converter <NUM>.

The system <NUM> operates through the generator controller <NUM> to supply two different voltage levels to the load <NUM> depending on the operational state of the engine. When the engine is operating, and the fan is spinning faster (e.g., <NUM>-<NUM> RPM), the generator <NUM> is regulated to produce a higher voltage (e.g., 270V DC at the output of the rectifier <NUM> or 115V AC from the generator <NUM>). However, if the engine fails, the low spool primary fan continues to spin due to the ram air pressure as the fan is still in the slip stream of the aircraft. During engine failure, the low spool primary fan is spinning at a lower speed (nominally <NUM>/<NUM>th of the speed during normal operation), also called wind milling. During wind milling, the generator <NUM> is regulated to a lower voltage (28V DC at the output of the rectifier <NUM> or 12V AC from the generator. The speed ratio can vary by engine type and also how fast the aircraft is travelling. The generator controller <NUM> can determine the operational mode of the engine (normal vs. wind milling) based on the speed of the fan and/or as reported by the engine. The full authority digital engine control (FADEC) system can report on the status of the engine. Also, the voltage of the generator <NUM> is continuously monitored. In one or more embodiments, the load <NUM> can require a 28V DC voltage and the converter <NUM> is a DC/DC converter that is configured to step down the 270V DC voltage from the rectifier <NUM> to a 28V DC voltage. During normal operation of the engine, the low spool primary fan is spinning at a high rate causing the generator <NUM> to produce a rectified voltage of 270V. The converter bypass switch <NUM> is operated by the generator controller <NUM> to allow the rectified voltage of 270V to be inputted into the converter <NUM>. The output of the converter <NUM> is the stepped down voltage of 28V and is used to drive the load <NUM>. During wind milling (i.e., engine failure), the low spool primary fan is spinning at a slower rate (<NUM>/<NUM>th) causing the generator <NUM> to produce a rectified voltage of 28V. The converter bypass switch <NUM> can be operated by the generator controller <NUM> to provide the rectified voltage of 28V directly to the load <NUM>. In one or more embodiments, the generator controller <NUM> can operate the bypass switch <NUM> based on the rotational speed of the fan in the engine by defining a threshold speed for operation. Should the rotational speed of the fan drop below the threshold speed, the generator controller <NUM> can operate the converter bypass switch <NUM> in a bypass state where the output of the rectifier <NUM> is connected directly to the load <NUM>. And if the rotational speed of the fan remains above the threshold speed (e.g., normal operation state), the generator controller <NUM> can operate the converter bypass switch <NUM> in the normal operation state by connecting the output of the rectifier <NUM> to the input of the converter <NUM> allowing the rectified voltage to be stepped down for the load <NUM>. In one or more embodiments, the generator <NUM> can be a wound field generator. The output voltage of a wound field generator may be controlled by modulating the strength of the magnetic field in the generator. The generator controller <NUM> uses energy from a small permanent magnet generator on the same shaft as the main generator to modulate the magnetic field of the main generator <NUM> (the more excitation of the field, and the faster the generator is spinning, the higher the generated voltage). The generator controller <NUM> can control the field to generate the higher voltage during the higher speed operational range of the engine. When the engine speed is not high enough, then the generator controller <NUM> will control the field to generate the lower voltage.

In one or more embodiments, the load <NUM> can require a 270V DC voltage for operation and the converter <NUM> is a boost converter that steps up the 28V DC voltage from the rectifier <NUM> to a 270V DC voltage. During normal operation of the engine, the low spool primary fan is spinning at a high rate causing the generator <NUM> to produce a rectified voltage of 270V. The converter bypass switch <NUM> is operated by the generator controller <NUM> to provide the rectified voltage of 270V directly to the load <NUM>. During wind milling (i.e., engine failure), the low spool primary fan is spinning at a slower rate (<NUM>/<NUM>th) causing the generator <NUM> to produce a rectified voltage of 28V. The converter bypass switch <NUM> can be operated by the generator controller <NUM> to allow the rectified voltage of 28V to be inputted into the converter <NUM>. The output of the converter <NUM> is the stepped up voltage of 270V and is used to drive the load <NUM>.

In one or more embodiments, the rectifier <NUM> can be optional based on the load <NUM>. The load <NUM> can be an AC load that would not require rectification of the AC voltage coming from the generator <NUM>. With an AC load as the load <NUM>, the converter <NUM> can be an AC/AC converter that is configured to either step up (boost) or step down the voltage based on the load <NUM> requirements.

As will be appreciated by those of skill in the art, the system described herein can provide power (e.g., electric) to one or more aircraft components. For example, without limitation, aircraft components that can be powered by the system described herein can include airfoil actuators, ailerons and other flight control surfaces (flaps, slats, etc.), and electrical and/or electronic components, including, but not limited to flight-critical instrumentation, navigation, heaters, and/or communication equipment.

In one or more embodiments, the generator controller <NUM> or any of the hardware referenced in the system <NUM> can be implemented by executable instructions and/or circuitry such as a processing circuit and memory. The processing circuit can be embodied in any type of central processing unit (CPU), including a microprocessor, a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like. Also, in embodiments, the memory may include random access memory (RAM), read only memory (ROM), or other electronic, optical, magnetic, or any other computer readable medium onto which is stored data and algorithms as executable instructions in a non-transitory form.

In one or more embodiments, the converter bypass switch <NUM> can be any type of switch including a one output switch, a two output switch, a combination of switches that allows for operation such that the voltage can flow in one of two directions (e.g., to the load <NUM> directly or to the converter <NUM>).

<FIG> depicts a flow diagram of a method for dual voltage power generation according to one or more embodiments of the invention. The method <NUM> includes providing a generator having an input connected to an engine to receive rotational energy proportional to a rotation speed of a fan driven by the engine and having an output through which electrical energy is output, as shown in block <NUM>. At block <NUM>, the method <NUM> includes providing a rectifier circuit having an input coupled to the output of the generator and a rectifier output that outputs rectified power. The method <NUM>, at block <NUM>, includes providing a bypass switch connected to the output of rectifier and configured to operate in a plurality of states, wherein the plurality of states includes a normal operation state where the rectified power is provided a power converter and a bypass state where the rectified power is provided directly to a load. The method <NUM> also includes determining an occurrence of an event associated with the engine, as shown at block <NUM>. And at block <NUM>, the method <NUM> includes operating the bypass switch in the bypass state based on the occurrence of the event associated with the engine.

Additional processes may also be included. It should be understood that the processes depicted in <FIG> represent illustrations, and that other processes may be added or existing processes may be removed, modified, or rearranged as far as it remains within the scope of the appended claims.

Claim 1:
A system (<NUM>) comprising:
an engine (<NUM>) including a fan (<NUM>);
a generator (<NUM>) having an input connected to the engine to receive rotational energy proportional to a rotation speed of the fan driven by the engine and having an output through which electrical energy is output;
a rectifier circuit (<NUM>) having an input coupled to the output of the generator and a rectifier output that outputs rectified power;
a power converter (<NUM>);
a load (<NUM>);
a bypass switch (<NUM>) connected to the rectifier output and configured to operate in a plurality of states, wherein the plurality of states comprises a normal operation state where the rectified power is provided to an input of the power converter and a bypass state where the rectified power is provided directly to the load;
a controller (<NUM>) configured to:
determine an occurrence of an event associated with the engine; and
operate the bypass switch in the bypass state based on the occurrence of the event associated with the engine, and wherein the occurrence of the event comprises the rotational speed of the fan being below a threshold rotational speed; and
regulate the generator to produce a first voltage in the normal operation state and to produce a second voltage lower than the first voltage in the bypass state.