Patent Application
20180194487
Damage to a turbine can occur if it ingests debris suspended in the air flowing through the turbine. The debris suspension can erode and/or abrade the compressor blades and vanes. If the debris becomes molten due to its interaction with the turbine, it could block cooling holes and accelerate thermal fatigue of the turbine's component(s). Additionally, if the debris should solidify on the nozzle guide vanes, the gas flow path may be significantly impeded. This impediment can cause the turbine to produce less work resulting in inadequate drive to the compressor, which could result in a gas flow reversal and compressor surge.
Debris suspension clouds are often not visually perceptible by an aircraft pilot at night. The suspended particulate matter often does not have a large enough radar cross section to provide a sufficient echo for detection by onboard weather radars. During daylight, the pilot might see the debris suspension cloud but could misinterpret it as a water vapor cloud that poses no danger to the aircraft.
A debris suspension can be caused by multiple sources. For example, volcanic activity, dust, ash, sandstorm, dry environment, aircraft ground effect, air pollution, industrial chemical release, etc. Some of these sources can result in debris suspension clouds at lower altitudes and/or localized effects. Other sources (e.g., volcanic activity) can cause debris suspension clouds to rise tens of thousands of feet and to travel with prevailing winds over large swaths of the atmosphere. The size of the particles in the ash cloud will diminish in size as the cloud travels downwind.
Ingestion of debris can be an extreme safety hazard (an aircraft could lose all engine power). There can also be direct and indirect economic damages wrought by aircraft ingestion of debris. Debris can accelerate maintenance/repair schedules. An indirect cost can be the rerouting and cancellation of flights. For example, the 2010 eruption of the Icelandic volcano Eyjafjallajökull caused a significant closure of European airspace for a week. On the order of 100,000 flights were canceled with an estimated cost to the aviation industry of $2.6 billion.
Volcanic ash remains the largest source of debris suspension clouds encountered by aircraft. There are many conventional approaches to alert airborne flight crews to avoid volcanic ash clouds. For example, the International Civil Aviation Organization operates nine Volcanic Ash Advisory Centers monitoring volcanic ash plumes. This information provides only limited use to pilots and/or flight control centers. Conventional models based on prevailing wind patterns can track the likely path of the bulk of the ash/silica/ejecta, but these models are not accurate because ash scattering is highly uncertain. Thus, these models at best only approximate where the majority of the ash is likely to be going or to have gone, and leaves potentially large pockets of ejecta that might fall outside the predicted ranges/zones due to shifting winds and/or inaccuracies in flow models, particle sizes and altitude ranges.
Another conventional approach simply draws a radius around a volcanic eruption site that increases with time elapsed since eruption. Given a pre-determined confidence interval (say 95% or 99.7% for example), a traffic re-route zone can be maintained. The problem is that the circle radius can be overly large, where distance from an eruption site does not necessarily decrease the magnitude or impact of an ash ingestion event since even at a great distance, the concentration of ash could be very large, depending on dispersion patterns.
Establishing large radius keep-out zones is not a favorable outcome for a number of reasons—regions within the keep-out zone will be inaccessible entirely; flight routes that would normally traverse the keep out zone can become longer requiring more fuel; and potentially the rerouted flight path could exceed the aircraft range.
Conventional airborne monitoring approaches are directed towards examining specific operating parameters of the engine performance and identifying particulate composition and flow rate from changes in engine performance. Other approaches monitor airborne particulate matter and alert the flight crew to their presence. One conventional approach includes an infrared camera mounted on an exterior wing surface to detect volcanic ash day or night at long distances.
There is a need for a system that directly discerns an aircraft's presence in a debris suspension cloud. There is a need for this system to be installed within the aircraft, thereby eliminating the need for certification of skin-altering additions to the airframe.
Embodying systems and methods directly discerns an aircraft's presence in a debris suspension cloud. Embodying systems can include an electronic camera that provides a digital image to a signal processor that operates to detect the onset of radiant flux caused by an aircraft entering a debris suspension cloud. Embodying systems and methods can provide a near-instantaneous warning of the situation. In accordance with embodiments, system components can be located within the existing shell of the aircraft, with the camera positioned to view through an existing window or aperture—i.e., not attached to the aircraft outer skin, nor needing the creation of an optical via through the outer skin. Thus, implementing this system into new aircraft builds, and retrofit installations, should not require flightworthiness certification of the aircraft. Embodying systems and methods provide a direct discernment system that can detect the actual presence of a debris suspension cloud around and/or near a turbine without relying on the conventional approach of applying an overly-inclusive model based on a likelihood of occurrence derived from estimations of exposure.
St. Elmo's fire is a weather phenomenon in which can result from a corona discharge from a surface with a high radius of curvature, such as a pointed object, in the presence of a strong electric field. This discharge can produce a visible, light-emitting radiant flux with an observed color range of bright blue or violet.
Whether an aircraft is transiting a debris suspension cloud of volcanic ash, or non-volcanic ash, can be determinative in where the St. Elmo radiant flux manifests itself. In accordance with embodiments, this distinction can be used to identify the nature of the suspension's particulate matter.
Experiments assessing the impact of dust-laden air on turbine aircraft engines reports that an observable glow appears at the fan face of a turbofan engine, or at the compressor face of a turbojet engine. This glow is attributable to St. Elmo's fire (i.e., radiant flux), and is indicative of dust suspension in the environment.
Downward thrust of a rotary wing aircraft (e.g., a helicopter, a vertical take-off and landing (VTOL) aircraft, etc.) can generate a local debris suspension cloud. Other sources of debris suspension clouds can include air pollution, industrial chemical release, etc. The debris suspension cloud, regardless of its source, can cause an observable radiant flux generated on turbine components transiting the cloud (e.g., aircraft, wind generation plant, locomotive engine, etc.).
System 200 can include control processor 205 that executes executable instructions 215 to control other units of the system. The control processor can be in communication the components of system 200 across data/communication bus 210.
System 200 can include optical assembly 224 that can contain one or more optical lenses 226A, 226B. In accordance with embodiments, the field-of-view (FOV) of optical assembly 224 can be adjusted by position/focal control unit 228 by control of servos, encoders, and the like. Control unit 228 can change the relative position of the lenses to increase/decrease the field-of-view so that a particular portion of a turbine and/or aircraft frame can be observed by system 200. Control unit 228 can also change the position of the optical assembly so that a different portion of the turbine and/or airframe is within the FOV. Control processor 205 can control position/focal control unit 228 by executing instructions 215.
Optical assembly 224 can provide an image to optical filter 222. Optical filter 222 can be matched to pass, with minimum attenuation, at least a portion of the light spectrum emitted by the radiant flux. The optical filter would attenuate light frequencies outside the radiant flux spectrum. In accordance with embodiments, optical filter 222 can be adaptively controlled by control processor 205 to change the optical filter's band pass characteristics to match light spectrum emissions from different particulate matter (e.g., volcanic ash, pollution, ground effect dust, etc.) that could be within the debris suspension cloud. Examples of the optical filter band pass characteristics can include, but are not limited to, the maximum percent transmission at the center of the band-pass of the filter; the light frequency (wavelength) of the center of the band-pass of the filter; the width of the band-pass of the filter; the steepness of the band-pass of the filter; and the existence of undesired or desired side band pass regions of the optical filter. The optical filter may have its band pass characteristics in the ultraviolet, visible, or infrared spectral regions.
A filtered, captured image is provided to imaging device 220. Imaging device 220 can be a solid-state electronic camera that creates a digital image. This digital image can be provided to image analysis unit 230 and/or stored in memory 240.
Image analysis unit 230 can be implemented as a signal processing unit configured to detect the onset of radiant flux generation caused by entering a debris suspension cloud. In accordance with embodiments, imaging device 220 can create digital images at a predetermined (fixed or variable) rate and provide the images to the image analysis unit. Analysis of a stream of images can provide details on whether radiant flux is being generated.
The intensity of the radiant flux glow can be linked nearly linearly to the concentration of particulate matter within the debris suspension cloud. The light can also be a function of the speed of the metal component (turbine blade, wing leading edge, etc.) passing through the debris suspension cloud. The intensity of the light positively correlates with the particulate density; i.e. the denser the debris suspension the stronger the maximum light intensity.
In accordance with embodiments, the detection of increased radiant flux generation can cause the image capture rate to increase. In this manner, about instantaneous detection of the presence of a debris suspension cloud can be determined. When a debris suspension cloud is detected, and the severity of the radiant flux generation indicates a critical concentration of particulate matter (i.e., above a predetermined threshold) for turbine operation, a warning signal can be provided by input/output (I/O) port 250 to operators (flight crew, locomotive engineers, power generation personnel, etc.).
In accordance with embodiments, analysis results can be uploaded via I/O port 250 across an electronic communication network to a remote server. The data can be uploaded on a real time or near real-time basis to the remote server for storage in a data store in communication with the remote server. The remote server can execute instructions to review data records of volcanic flashes obtained from meteorological observation equipment to correlate the analysis from system 200 with known conditions. A verification report can be communicated back to the flight crew.
The optical assembly 224 (
In accordance with embodiments, the radiant flux intensity of the light produced by interaction between the debris suspension cloud and moving turbine blades (or rotary wing, or airframe surface) can be integrated to provide a parameter that can be used to determine an amount of wear. The radiant flux produced is expected to be nearly linearly linked to the debris suspension particulate matter concentration, a function of turbine blade speed, and blade composition. The quantifiable relationships are derivable from measured data produced by an experiment quantifying the intensity of glow generated by a buildup of electrostatic charge on particulate matter of the debris suspension cloud, and/or on the moving surfaces of the turbine blades.
With regard to
The infrared signature is a function of both the mass flow of particulate matter entering the engine, as well as the kinetic forces of the fan or rotor blade (which, for example, in turn is a function of physical fan/rotor speed N1, or core speed N2). Engine or application-specific curves can be derived experimentally in a test cell environment, or empirically using flight data. The rate of engine health deterioration can have a strong correlation with the mass flow of ingested particulate matter. The mass flow of ingested particulate matter may be approximated from these curves, using the infrared signature factor and the fan, rotor or core speed. The use of the proposed system and infrared signature provides an additional source of engine health data that has previously been unavailable. Embodying systems and methods improve estimations of engine deterioration rate by assessing an infrared signature and/or approximated mass flow of particulate matter integrated over time.
In accordance with embodiments, the approximation of particulate matter injection into an engine (or alternatively, particulate density in the vicinity of a rotary wing) can be refined using the fan speed, core speed, or rotor speed as appropriate. For example, the infrared signature factor increases for either a constant particulate level (constant y-axis) as the rotational speed increases, or for a constant rotational speed (constant x-axis) as the particulate level increases.
Rotor and fan blade scintillation is driven by (1) the particulate mass flow into the fan of an engine (or alternatively, particulate density in the vicinity of a rotary wing); (2) the inertial or kinetic forces (i.e., “collisional” forces) caused by the fan or rotor blades (or compressor and/or booster blades) hitting or colliding with the particulate matter; and (3) a low humidity environment. Humidity measurement at the low end of the spectrum is not very accurate; nor are humidity measurements generally available on aircrafts. Furthermore, because scintillation is likely to only occur in dry environments, the range of relative humidity experienced during scintillation is relatively narrow. Accordingly, refining the approximation of particulate matter based on humidity can be omitted.
Fan, rotor, and/or core speed are all readily available on-wing and act as a proxy for kinetic, inertial and/or collisional forces. In accordance with implementations, the physical, uncorrected fan, rotor, and/or core speed provides an improved approximation because the interaction between the fan, rotor, and/or compressor blades and the particulate matter is not dependent on how much energy was required to achieve the speed (due primarily to the effect on ambient temperatures). The interaction is primarily based on the actual kinetic energy level at the time of impact. Therefore, using a “corrected speed” could skew this approximation. Thus, given the fan, core, and/or rotor speed and the infrared signature of the scintillation, the mass flow of ingested particulate matter can be approximated.
In accordance with embodiments, optical assembly 224 can be implemented as an infrared camera. The infrared camera can be placed within a bypass duct or engine core compartment of a turbine. The infrared camera can sense compressor blade scintillation within the engine. Placement within the bypass duct or engine core would lessen the impact that visible light has on the infrared scintillation signature due to the camera being directed at an area within a generally dark compartment. In accordance with some embodiments, the image provided by the infrared camera could be used to intermittently detect the presence of ice buildup within the bypass duct in the under-cowling or other locations where ice is likely to accumulate.
In accordance with embodiments, multiple infrared cameras can be utilized, with each of the multiple infrared cameras calibrated to sense different infrared signature ranges. For example, a first infrared camera could be calibrated in a range that senses and quantifies the amount of particulate matter ingested by an engine in a “normal” or “daily” scenario. A second infrared camera could be calibrated for a much larger range to sense and quantify the amount of particulate matter ingested during a sandstorm, volcanic ash event, and\or other type of atypical or unusual situation.
The image capture device can be mounted internal to an airframe to eliminate external mounting hardware or an optical via through the airframe. The field-of-view of the image capture device is directed towards a portion of a turbine, a rotary wing, or the aircraft. Interaction between moving metal members of these components and a debris suspension cloud can cause generation of a radiant flux.
A series of digital images are captured, step 710, by the image capture device. These images can be obtained at regular and/or irregular intervals based on the concentration of particulate matter in the debris suspension cloud, the geographic location of the aircraft, and/or other considerations. The captured images can be provided to image analysis unit 230, which analyzes, step 720, the images.
If the analysis result indicates that a radiant flux is not detected, the process returns to step 710, where images are continued to be captured. If a radiant flux is detected, the intensity of the radiant flux is determined, step 725. The intensity of the light positively correlates with the particulate density—i.e. the denser the debris suspension the stronger the maximum light intensity.
The image capture rate can be adjusted, step 730, based on the radiant flux intensity. For example, if the intensity is greater than a threshold and/or is increasing compared to prior readings, then the capture rate could be increased. Otherwise, the capture rate can be decreased, until some later reading indicates an increasing concentration of particulate matter. Instruction to adjust the capture rate can be provided, step 735, by control processor 205 to the image capture device.
The concentration of particulate matter based on the intensity of the radiant flux, and/or the amount of component wear, or deterioration, based on the proportional integrated signal can be determined, step 740. If the particulate concentration, and/or the component wear (i.e., above a predetermined tolerance) is at a critical level, step 745, an alert can be provided, step 750. If not, then the process can continue capturing digital images (step 710). The alert can be in the form of a cockpit annunciator and/or display to the crew. In some implementations the alert can be transmitted to tracking stations, or broadcast to other aircraft.
Embodying systems and methods provide both safety and economic benefits, even if the system yields an acceptable number of false positives. For example, because embodying systems and methods determine flight status on actual conditions experienced by the aircraft, the number of aborted flights is reduced when compared to the conventional approach of aborting flights based on an assumptive prediction of where a debris suspension cloud might exist.
If the aircraft is not traversing a keep-out zone, at step 950 a decision is made determining whether the aircraft is proximate to a keep-out zone. The distance from the keep-out zone in determining step 950 can be predetermined by aviation authorities, the flight crew, aircraft maintenance recommendations, or by other criteria. If the aircraft is determined not to be proximate to the keep-out zone, the flight continues, step 920. If the aircraft is determined to be proximate to the keep-out zone (within the predetermined distance), the flight is aborted, step 940.
In accordance with some embodiments, a computer program application stored in non-volatile memory or computer-readable medium (e.g., register memory, processor cache, RAM, ROM, hard drive, flash memory, CD ROM, magnetic media, etc.) may include code or executable instructions that when executed may instruct and/or cause a controller or processor to perform methods discussed herein such as a method for detecting the presence of a debris suspension cloud, as described above.
The computer-readable medium may be a non-transitory computer-readable media including all forms and types of memory and all computer-readable media except for a transitory, propagating signal. In one implementation, the non-volatile memory or computer-readable medium may be external memory.
Although specific hardware and methods have been described herein, note that any number of other configurations may be provided in accordance with embodiments of the invention. Thus, while there have been shown, described, and pointed out fundamental novel features of the invention, it will be understood that various omissions, substitutions, and changes in the form and details of the illustrated embodiments, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the invention. Substitutions of elements from one embodiment to another are also fully intended and contemplated. The invention is defined solely with regard to the claims appended hereto, and equivalents of the recitations therein.
