Patent Application
20140002050
The present invention is generally related to electronic circuits, and more particularly, to circuitry, which may be adapted to operate in a high temperature environment of a turbine engine.
Turbine engines, such as gas turbine engines, may be used in a variety of applications, such as driving an electric generator in a power generating plant or propelling a ship or an aircraft. Firing temperatures of modern gas turbine engines continue to increase in response to the demand for higher combustion efficiency.
It may be desirable to use circuitry, such as may be used in a wireless telemetry system, to monitor operational parameters of the engine. For example, to monitor operating temperatures of components of the turbine, such as a turbine blade, or to monitor operational stresses placed upon such components during operation of the engine. Aspects of the present invention offer improvements in connection with such a circuitry.
The invention is explained in the following description in view of the drawings that show:
Example embodiments of the present invention may be directed to electronic circuitry, which, in one example application, may be used in an internal combustion engine, such as a turbine engine, instrumented with a telemetry system. This example application may allow transmitting sensor data from a movable component, such as a rotatable turbine engine blade, having certain electronic circuitry, which, for example, may operate in an environment having a temperature exceeding approximately 300° C.
For purposes of the disclosure herein, the term “high temperature” environment without additional qualification may refer to any operating environment, such as that within portions of a turbine engine, having a maximum operating temperature exceeding approximately 300° C. It will be appreciated that aspects of the present invention are not necessarily limited to a high temperature environment, since circuitry embodying aspects of the present invention may be used equally effective in a non-high temperature environment.
Power source circuitry 39 may acquire electrical power by way of one or more power-harvesting modalities, such as induced RF (radio frequency) energy and/or by harvesting thermal or vibrational power within the turbine engine. For example, thermopiles may be used to generate electricity from thermal energy, or piezoelectric materials may generate electricity from vibration of the turbine engine. For readers desirous of general background information regarding examples forms of power harvesting modalities, reference is made to U.S. Pat. No. 7,368,827, titled “Electrical Assembly For Monitoring Conditions In A Combustion Turbine Operating Environment”, the entire disclosure of which is incorporated herein by reference.
Regardless of the specific power-harvesting modality, in one example embodiment AC (alternating current) power 41 may be supplied to a rectifier 42, which converts the AC input to a DC (direct current) output, which is coupled to a voltage regulator 44, which may be configured to maintain a relatively constant DC voltage output 45, even in the presence of variation of the harvested AC input voltage. It will be appreciated that a constant voltage output may be desired to achieve a required measurement accuracy and/or stability for any given engine parameter being measured.
In one example embodiment, voltage regulator 50 may be adapted to operate in a high-temperature environment of a turbine engine. Voltage regulator 50 may include a constant current source 52, such as may include a first semiconductor switch 54 and a first resistor 56 connected between a gate terminal (G) and a source terminal (S) of first semiconductor switch 54.
In one example embodiment, a second resistor 58 may have a first lead 60 connected to the gate terminal (G) of first semiconductor switch 54 and a second lead 62 connected to an electrical ground 64. Constant current source 52 may be coupled to generate a voltage reference (Vr) across second resistor 58. A source follower output stage 66 may include a second semiconductor switch 68 and a third resistor 70 connected between electrical ground 64 and a source terminal (S) of second semiconductor switch 68. As can be appreciate in
In one example embodiment, current source 52 may further include an input stage 72, which may include a third semiconductor switch 74 having a drain terminal (D) connected to receive an input voltage (Vin) (e.g., output from rectifier 42 in
In an alternate embodiment illustrated in
In one example embodiment, semiconductor switches 54, 68, 74 and 84 may be n-channel junction gate field-effect transistor (JFET) switches and may comprise a respective high-temperature, wide bandgap material, such as SiC, AlN, GaN, AlGaN, GaAs, GaP, InP, AlGaAs, AlGaP, AlInGaP, and GaAsAlN.
As will be appreciated by one skilled in the art, high-temperature voltage regulation, as would involve zener diodes made of a high-temperature, wide bandgap material is presently not feasible, since zener diodes involving high-temperature materials are not believed to be commercially available. Moreover, p-channel SiC JFETs are presently believed to be impractical in high-temperature applications due to their relatively low-channel mobility. Accordingly, circuitry embodying aspects of the present invention, advantageously overcomes the present unavailability of zener diodes made of high-temperature, wide bandgap materials with n-channel JFETs, and thus such a circuitry may operate within the theoretical temperature limits of high-temperature, wide bandgap material JFETs (e.g., above 500° C.) and effectively provide a substantially stable voltage regulator. In one example application, a voltage regulator in accordance with aspects of the present invention may be utilized to appropriately regulate a power source in a high-temperature environment for powering load circuitry involving relatively low-voltage information signals. For example, prior to the present invention, such load circuitry would have been susceptible to measurement uncertainties resulting from power source instabilities in view of the relatively low-magnitude (e.g., a few millivolts) of the information signals, which may be generated by sensors, such as thermocouples and strain gauges.
In one example embodiment, the magnitude of the regulated output voltage Vout may be adjustable by adjusting a ratio of the respective resistance values of first and second resistors 56 and 58. Typically, the output voltage of known voltage regulators is not adjustable, and, if so desired, for known voltage regulators an operational amplifier would be involved. However, for high-temperature applications, operational amplifiers made of high-temperature, wide bandgap materials are not believed to be commercially available. Accordingly, a voltage regulator embodying aspects of the present invention in a simplified manner (e.g., with lesser active components) may be conveniently configured to adjust the magnitude of the regulated output voltage Vout, as may involve operation in a high-temperature environment. If optionally desired, a resistive temperature detector (RTD) or similar may be combined with the first and second resistors 56 and 58 to control the regulated output voltage Vout in accordance with temperature changes. It is contemplated that because of the improved stability and repeatability, which can be achieved with a voltage regulator embodying aspects of the present invention, any voltage regulation variation, which may be experienced by the voltage regulator under temperature changes would be consistently repeatable, which means any such voltage regulation variation resulting from temperature changes can be appropriately compensated using techniques well-understood by those skilled in the art.
While various embodiments of the present invention have been shown and described herein, it will be apparent that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
