Method and system for detecting an abnormal engine start

Herein provided are methods and systems for detecting an abnormal engine start of a gas turbine engine. An inter-turbine temperature of the engine is measured during engine start. The inter-turbine temperature is compared to an inter-turbine temperature threshold which depends on at least one additional parameter. An abnormal engine start is detected when the inter-turbine temperature exceeds the threshold. The at least one additional parameter may comprise engine rotational speed. The at least one additional parameter may comprise time.

TECHNICAL FIELD

The present disclosure relates generally to gas turbine engines, and more particularly to detecting an abnormal engine start.

BACKGROUND OF THE ART

When an engine starts abnormally, this may lead to distress and/or damage to the engine. To address this issue, engine control systems sometimes measure the temperature of an engine during the engine start using a temperature probe. In the event that the temperature of the engine exceeds a specific value, the engine is shut down by the engine control system.

However, the temperature probe may not be able to obtain an accurate temperature measurement until the engine is idling. As such, by the time a temperature measurement of the engine exceeds the specific value during an abnormal engine start, the engine may have already been distressed and/or damaged.

As such there is room for improvement.

SUMMARY

In one aspect, there is provided a method for detecting an abnormal engine start of a gas turbine engine. The method comprises monitoring an inter-turbine temperature of the engine during engine start; comparing the inter-turbine temperature to an inter-turbine temperature threshold which depends on at least one additional parameter; and detecting an abnormal engine start when the inter-turbine temperature exceeds the threshold.

In another aspect, there is provided a system for detecting an abnormal engine start of a gas turbine engine. The system comprises a processing unit and a non-transitory computer-readable memory having stored thereon program instructions executable by the processing unit. The program instructions executable by the processing unit are for monitoring an inter-turbine temperature of the engine during engine start; comparing the inter-turbine temperature to an inter-turbine temperature threshold which depends on at least one additional parameter; and detecting an abnormal engine start when the inter-turbine temperature exceeds the threshold.

DETAILED DESCRIPTION

FIG. 1illustrates a gas turbine engine10for which an abnormal engine start may be detected using the methods and systems described herein. Note that while engine10is a turbofan engine, the methods and systems for detecting an abnormal engine start may be applicable to turboprop, turboshaft, auxiliary power units (APU), and other types of aircraft engines.

Engine10generally comprises in serial flow communication: a fan12through which ambient air is propelled, a compressor section14for pressurizing the air, a combustor16in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section18for extracting energy from the combustion gases. Axis11defines an axial direction of the engine10.

With reference toFIG. 2, there is illustrated a flowchart of an example method200for detecting an abnormal engine start of a gas turbine engine, such as engine10ofFIG. 1. While the method200is described herein with reference to the engine10ofFIG. 1, this is for example purposes. The method200may be applied to other types of engines depending on practical implementations.

At step202, an inter-turbine temperature of the engine is monitored during engine start. The inter-turbine temperature may be monitored by obtaining temperature measurements from a temperature measurement device comprising one or more temperature sensors. With reference toFIG. 1, in some embodiments, the one or more temperature sensors may be positioned between a low-pressure turbine20and a high-pressure turbine22of the turbine section18. The location of the temperature sensors may vary depending on the practical implementation. The inter-turbine temperature may be dynamically measured in real time, or may be recorded regularly in accordance with any suitable time interval. Step202may comprises triggering measurements of inter-turbine temperature whenever method200is initiated.

Referring back toFIG. 2, at step204, the inter-turbine temperature is compared to an inter-turbine temperature threshold which depends on at least one additional parameter. The at least one additional parameter may vary depending on practical implementations. In some embodiments, the at least one additional parameter comprises engine rotational speed. In some embodiments, the at least one additional parameter comprises time.

At step206, an abnormal engine start is detected when the inter-turbine temperature exceeds the threshold. In some embodiments, when the abnormal engine start is detected, an indication of the abnormal engine start may be provided to the pilot, crew members and/or service crew.

In some embodiments, the method200comprises an optional step208of shutting down the engine10in response to detecting the abnormal engine start. For example, if an abnormal engine start is detected for a ground start, the engine10may automatically be shut down. Accordingly, the method200may be directed to a method for shutting down a gas turbine engine.

It should be appreciated that by having the inter-turbine temperature threshold which depends on at least one additional parameter, this reduces the risk of damage to the engine10which may have otherwise occurred if the inter-turbine temperature threshold was independent of additional parameters. The inter-turbine temperature threshold which depends on at least one additional parameter may be designed in a manner to reduce the risk of damage to the engine10compared to an independent temperature threshold.

In some embodiments, the inter-turbine temperature threshold depends on engine rotational speed (Ng). With additional reference toFIG. 3, an example inter-turbine temperature threshold304is illustrated that depends on the engine rotational speed. The inter-turbine temperature threshold304has a constant value308when the engine rotational speed of the engine10is within a first range310of engine rotational speeds. The inter-turbine temperature threshold304has no value when the engine rotational speed of the engine10is within a second range330of engine rotational speeds. As such, in this example, the inter-turbine temperature threshold304has a limit320based on engine rotational speed. The ranges310,330may be defined in terms of a percentage of a maximum engine rotational speed of the engine10. For example, the first range310may correspond to a range of 0% to N % and the second range330may correspond to a range of N % to 100%. Alternatively, the ranges310,330may be defined in terms of an actual engine rotational speed (e.g., in revolutions per minute).

As shown inFIG. 3, a curve302illustrates a measurement of inter-turbine temperature of the engine10as a function of the engine rotational speed. The engine rotational speed may be monitored by obtaining rotational speed measurements from a rotational speed measurement device comprising one or more sensors. The rotational speed measurement device may comprise a tachometer, revolution-counter, and/or any other suitable device. Alternatively, the engine rotational speed is provided by an engine computer or an aircraft computer.

In this example, during the engine start, the inter-turbine temperature302is compared to the inter-turbine temperature threshold304. As shown, the inter-turbine temperature302increases until a point306where it exceeds the inter-turbine temperature threshold304. Accordingly, an abnormal engine start is detected when the inter-turbine temperature302exceeds the inter-turbine temperature threshold304. In this example, the engine10is shut down in response to detecting the abnormal engine start and the curve302no longer illustrates the inter-turbine temperature after the engine10has been shut down.

In some embodiments, comparing the inter-turbine temperature302to the inter-turbine temperature threshold304comprises comparing the inter-turbine temperature302to the constant value308when the engine rotational speed of the engine is within the first range310of engine rotational speeds. For example, the engine rotational speed may be compared to an engine rotational speed threshold322for determining if the inter-turbine temperature302should be compared to the inter-turbine temperature threshold304. Accordingly, while the engine rotational speed is below the engine rotational speed threshold322, the inter-turbine temperature302may be compared to the inter-turbine temperature threshold304. In this example, the engine rotational speed threshold322is defined by an endpoint316of the first range310of engine rotational speeds.

In some embodiments, the endpoint316of the first range310of engine rotational speeds is based on a first offset312from at least one operating characteristic of the engine10. In some embodiments, the operating characteristic is an expected light-off engine rotational speed314of the engine10. By way of a specific and non-limiting example, the expected light-off engine rotational speed314of the engine10is approximately 20% of the maximum engine rotational speed. By way of another specific and non-limiting example, the expected light-off engine rotational speed314of the engine10is in the range to 15 to 25% of the maximum engine rotational speed. Other values are contemplated, depending on implementation of the engine10.

In some embodiments, the operating characteristic is an expected engine rotational speed where fuel is introduced into the engine10. By way of a specific and non-limiting example, the engine rotational speed where fuel is introduced into the engine10is approximately 15% of the maximum engine rotational speed. By way of another specific and non-limiting example, the engine rotational speed where fuel is introduced into the engine10is in the range to 10 to 20% of the maximum engine rotational speed. Other values are contemplated, depending on implementation of the engine10.

The inter-turbine temperature threshold304may be based on the expected light-off engine rotational speed314of the engine10and/or the expected engine rotational speed where fuel is introduced into the engine10. For example, the engine rotational speed corresponding to the limit320of the inter-turbine temperature threshold304may be set based on the expected light-off engine rotational speed314of the engine10and/or the expected engine rotational speed where fuel is introduced into the engine10.

In some embodiments, the inter-turbine temperature threshold304is determined based on a temperature profile324of the engine10as a function of engine rotational speed for acceptable engine starts. Acceptable engine starts may be determined as a function of various parameters, such as a range of aircraft altitudes and a range of ambient temperatures. The temperature profile324may be obtained by measuring and recording the temperature of the engine10as a function of engine rotational speed, during engine start, over a range of altitudes and a range of ambient temperatures. For example, the temperature of the engine10may be measured during engine start at a low altitude (e.g., below 1000 meters) and measured at a high altitude (e.g., above 2,400 meters). Similarly, the temperature of the engine10may be measured during engine start at a cold ambient temperature (e.g., below −30 degrees Celsius) and measured at a warm ambient temperature (e.g., above 25 degrees Celsius). Measurements at a combination of different altitudes and ambient temperatures may be done. The temperature profile324may be determined by setting a lower limit332and an upper limit334of the temperature profile324. The lower limit332and the upper limit334may be set such that the temperature measurements of the engine10for the ranges of altitudes and ambient temperatures are between the lower limit332and the upper limit334. Alternately, or in addition, the temperature profile324may be obtained by computer simulation that simulates the temperature of the engine10during start over a range of altitudes and ambient temperatures.

In some embodiments, the constant value308of the inter-turbine temperature threshold304is based on a second offset318from an acceptable temperature of the engine10prior to light-off. As illustrated, the acceptable temperature of the engine10prior to light-off may be obtained from the temperature profile324. For example, the second offset318may be from the upper limit334of the temperature profile324. Alternatively, the second offset318may be based on the lower limit332of the temperature profile324, or the second offset318may be based on an average of the upper limit334and lower limit332. By way of a specific and non-limiting example, the second offset318is set to approximately 250 degrees Celsius. By way of another specific and non-limiting example, the second offset318is set somewhere in the range of 100 degrees Celsius and 300 degrees Celsius. Other values for the second offset318are contemplated.

In some embodiments, the inter-turbine temperature threshold304is determined from the temperature profile324based on at least one of a frequency of occurrence of an abnormal engine start, tolerance of components of the engine10and at least one of the offsets312,318.

The frequency of occurrence of an abnormal engine start refers to a probability of the engine10having an abnormal engine start. The frequency of occurrence of an abnormal engine start may be determined from measuring engine starts and/or computer simulation. For example, if the frequency of occurrence of an abnormal engine start is less than 0.1%, a larger offset for the second offset318from the temperature profile324may be used compared to when a frequency of occurrence is greater than 0.1%. By way of another example, if the engine10has a frequency of occurrence less than 1%, a larger offset for the second offset318from the temperature profile324may be used compared to when a frequency of occurrence is greater than 1%. Other values are contemplated, depending on implementation of the engine10.

Tolerance of components of the engine10refers to a permissible limit of one or more components of the engine10prior to distress, damage and/or failure. The tolerance of components may be known based on the components used to build the engine10or may be determined from measurements and/or computer simulations. For example, if it is known that a certain component of the engine10may be damaged at 650 degrees Celsius and that prior to light-off an acceptable engine start would likely not exceed 200 degrees Celsius, then the second offset318may be set to 250 degrees Celsius. By way of another example, if it is known that a certain component of the engine10may be damaged at 700 degrees Celsius and that prior to light-off an acceptable engine start would likely not exceed 220 degrees Celsius, then the second offset318may be set to 300 degrees Celsius. Other values are contemplated, depending on implementation of the engine10.

While the inter-turbine temperature threshold304is illustrated as a constant value308in the first range310of engine rotational speeds, in other embodiments the inter-turbine temperature threshold304may vary in value over the first range310of engine rotational speeds.

In some embodiments, the inter-turbine temperature threshold depends on a time parameter. The inter-turbine temperature threshold may comprise one or more temperature values, each having a corresponding duration associated thereto. As such, in this example, the inter-turbine temperature threshold is exceeded if the inter-turbine temperature of the engine10exceeds a specific one of the one or more temperate values for the corresponding duration of that specific temperature value.

With reference to Table 1, an example inter-turbine temperature threshold is shown associated with corresponding durations. As shown, the inter-turbine temperature threshold is deemed exceeded when the inter-turbine temperature is measured at 500 degrees Celsius or greater for at least 30 seconds. The inter-turbine temperature threshold is deemed exceed when the inter-turbine temperature is measured at 600 degrees Celsius or greater for at least 15 seconds.

TABLE 1Inter-turbine temperature threshold based on timeTemperatureDuration500 degrees Celsius30 seconds600 degrees Celsius15 seconds

Accordingly, the inter-turbine temperature threshold may have a first minimum temperature value for a first minimum duration and a second minimum temperature value for a second minimum duration, where the first and second minimum temperature values are different from each other. The first minimum temperature value is exceeded when the inter-turbine temperature is measured at or above the first minimum temperature for at least the first minimum duration. Similarly, the second minimum temperature value is exceeded when the inter-turbine temperature is measured at or above the second minimum temperature for at least the second minimum duration. The first and second minimum durations may be different from each other. In some embodiments, the first minimum temperature value is lower than the second minimum temperature value and the first minimum duration is longer than the second minimum duration. The number of minimum temperature values may vary depending on practical implementations. For example, a single minimum temperature value having a single minimum duration may be used. In other cases, more than two minimum temperature values each having a respective minimum duration may be used.

The inter-turbine temperature threshold may comprise one or more temperature ranges, each having a corresponding duration associated thereto. As such, in this example, the inter-turbine temperature threshold is exceeded if the inter-turbine temperature of the engine10is within a specific one of the one or more temperate ranges for the corresponding duration of that specific temperature range.

With reference to Table 2, another example inter-turbine temperature threshold is shown associated with corresponding durations. As shown, the inter-turbine temperature threshold is deemed exceeded when the inter-turbine temperature is measured within a range of 500 to 600 degrees Celsius for at least 20 seconds. The inter-turbine temperature threshold is deemed exceed when the inter-turbine temperature is measured within a range of 600 to 700 degrees Celsius for at least 15 seconds. The inter-turbine temperature threshold is deemed exceed when the inter-turbine temperature is measured within a range of 700 to 800 degrees Celsius for at least 10 seconds.

TABLE 2Inter-turbine temperature threshold based on timeTemperatureDuration500 to 600 degrees Celsius20 seconds600 to 700 degrees Celsius15 seconds700 to 800 degrees Celsius10 seconds

The number of temperature ranges and the corresponding duration may vary depending on practical implementation. For example, the number of temperature ranges may be less than three (e.g., one or two) or more than three. The values for the temperature ranges may also vary depending on practical implementation.

Accordingly, comparing the inter-turbine temperature to the inter-turbine temperature threshold at204may comprise comparing the inter-turbine temperature to the inter-turbine temperature threshold for a period of time. For example, the inter-turbine temperature may be monitored and when the inter-turbine temperature exceeds a temperature value or is within a temperature range, a time counter may be started. When the time counter exceeds a corresponding duration associated with the temperature value being exceeded or the temperature range that the inter-turbine temperature is currently in, then it may be determined that the inter-turbine temperature threshold has been exceeded. The time counter may be reset when the inter-turbine temperature falls below the temperature value or falls outside of the temperature range.

In some embodiments, detecting an abnormal start of the engine10comprises detecting an abnormal engine start when the inter-turbine temperature exceeds a temperature value of the inter-turbine temperature threshold for a duration. For example, if the inter-turbine temperature is above 500 degrees Celsius for at least 30 seconds, an abnormal engine start may be detected. By way of another example, if the inter-turbine temperature is above 600 degrees Celsius for at least 15 seconds, an abnormal engine start may be detected.

In some embodiments, detecting an abnormal start of the engine10comprises detecting an abnormal engine start when the inter-turbine temperature is within a temperature range of the inter-turbine temperature threshold for a duration. For example, if the inter-turbine temperature is within 500 to 600 degrees Celsius for at least 20 seconds, an abnormal engine start may be detected. By way of another example, if the inter-turbine temperature is within 600 to 700 degrees Celsius for at least 15 seconds, an abnormal engine start may be detected.

The method200may be implemented by a control system. With reference toFIG. 4, the control system may be implemented by a computing device410, comprising a processing unit412and a memory414which has stored therein computer-executable instructions416. The processing unit412may comprise any suitable devices configured to implement the method200such that instructions416, when executed by the computing device410or other programmable apparatus, may cause the functions/acts/steps performed as part of the method200as described herein to be executed. The processing unit412may comprise, for example, any type of general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof.

The methods and systems for detecting an abnormal engine start of an engine described herein may be implemented in a high level procedural or object oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of a computer system, for example the computing device410. Alternatively, the methods and systems detecting an abnormal engine start of an engine may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems for detecting an abnormal engine start of an engine may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems for detecting an abnormal engine start of an engine may also be considered to be implemented by way of a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may comprise computer-readable instructions which cause a computer, or more specifically the processing unit412of the computing device410, to operate in a specific and predefined manner to perform the functions described herein, for example those described in the method200.