Aircraft Engine Icing Event Avoidance and Mitigation Through Real-Time Simulation and Controls

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(12) (io) Patent No.:

United States Patent US 10,184,405 B1

(45) Jan. 22,2019

Veres et al. Date of Patent: (54) AIRCRAFT ENGINE ICING EVENT (58) Field of Classification Search CPC ... F02C 9/00; F02C 9/28; F02C 7/047; B64D AVOIDANCE AND MITIGATION THROUGH 33/02; B64D 15/20; B64D 2033/0233; REAL-TIME SIMULATION AND CONTROLS F05D 2260/81; F05D 2220/323; FO1D 25/02 (71) Applicant: The United States of America as See application file for complete search history.

represented by the Administrator of NASA, Washington, DC (US) (56) References Cited U.S. PATENT DOCUMENTS (72) Inventors: Joseph P. Veres, Olmsted Falls, OH (US); Philip C. Jorgenson, Richfield, 7,921,632 132 * 4/2011 Jacquet-Francillon ......................

OH (US) B64D 15/04 244/134 F (73) Assignee: The United States of America as 8,711,008 132 * 4/2014 Cook ..................... B64D 15/20 340/601 Represented by the Administrator of 9,221,548 131 * 12/2015 Sishtla ................... B64D 43/00 National Aeronautics and Space 9,846,230 131 * 12/2017 Finley ................... GO1S 13/953 Administration, Washington, DC(US) 2013/0008174 Al* 1/2013 Gould .................... B64D 15/20 60/779 (*) Notice: Subject to any disclaimer, the term ofthis 2013/0099944 Al* 4/2013 Hanson ................... FO1D 21/10 340/962 patent is extended or adjusted under 35 2015/0040577 Al* 2/2015 Dischinger ............... F02C 7/00 U.S.C. 154(b) by 30 days.

60/779 2016/0035203 Al* 2/2016 Rossotto ................ G08B 19/02 (21) Appl. No.: 15/474,562 701/36 2016/0041304 Al* 2/2016 Grzych .................. B64D 47/00 701/14 (22) Filed: Mar. 30, 2017 * cited by examiner Primary Examiner Michael J Zanelli Related U.S. Application Data (74) Attorney, Agent, or Firm Robert H. Earp, III; (60) Provisional application No. 62/323,158, filed on Apr. William M. Johnson 15, 2016.

(57) ABSTRACT A process for mitigating or proactively avoiding an aircraft (51) Int. Cl.

engine icing event may include detecting ice crystals in the F02C 9/00 (2006.01) atmosphere using one or more sensors on board an aircraft B64D 33/02 (2006.01) in real time. The process may also include modulating one F02C 7/047 (2006.01) or more engine operating conditions to proactively change an ice accretion location, to avoid the occurrence of an icing (52) U.S. Cl.

event. The process may further include implementing one or CPC ................ F02C 9/00 (2013.01); B64D 33/02 more modulated engine operating conditions in engine con- (2013.01); F02C 7/047 (2013.01); B64D trols software, hardware, or both.

203310233 (2013.01); F05D 22201323 (2013.01); F05D 2260181 (2013.01) 18 Claims, 7 Drawing Sheets

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US 10,184,405 B1

AIRCRAFT ENGINE ICING EVENT In one embodiment, a process may include detecting an AVOIDANCE AND MITIGATION THROUGH icing event using one or more sensors on board an aircraft REAL-TIME SIMULATION AND CONTROLS in real time. The process also includes, when the icing event is detected, modulating one or more engine operating con- CROSS-REFERENCE TO RELATED s ditions to change an ice accretion location. The process APPLICATION further includes implementing the one or more modulated engine operating conditions in engine controls software, hardware, or both.

This application claims the benefit of Provisional Appli- In another embodiment, a process for mitigating or pro- cation No. 62/323,158, filed on Apr. 15, 2016. The subject 10 actively avoiding an aircraft engine icing event may include matter thereof is hereby incorporated herein by reference in integrating one or more icing computational modules into its entirety.

engine control systems. The integrating of the one or more icing computational modules into engine control systems ORIGIN OF THE INVENTION may include detecting an existence of high altitude ice crystals in an atmosphere, by one or more sensors on board The present invention relates to aircraft engine icing an aircraft, in real time. The integrating of the one or more avoidance techniques, and more particularly, to a process for icing computational modules into engine control systems mitigating or proactively avoiding the risk of engine icing in may also include mitigating or proactively avoiding in real turbofan engines due to high altitude ice crystals without time effects of ice crystals through the engine control sacrificing fuel burn due to circumnavigating the ice crystal 20 systems by modulating one or more engine operating con- cloud.

ditions to change an ice accretion location, when ice crystals in the atmosphere are detected, and implementing one or FIELD more modulated engine operating conditions in engine con- trols software, hardware, or both.

The present invention relates to aircraft engine icing avoidance technique, and more particularly, to a process for BRIEF DESCRIPTION OF THE DRAWINGS mitigating or proactively avoiding the risk of engine icing in turbofan engines due to high altitude ice crystals without In order that the advantages ofcertain embodiments ofthe sacrificing fuel burn due to circumnavigating the ice crystal invention will be readily understood, a more particular cloud. 30 description of the invention briefly described above will be rendered by reference to specific embodiments that are BACKGROUND illustrated in the appended drawings. While it should be understood that these drawings depict only typical embodi- Often undetectable with current radar, ice crystals in ments ofthe invention and are not therefore to be considered convective storm cells can produce a phenomenon referred to be limiting of its scope, the invention will be described to as "Ice Crystal Icing" and ice can accumulate, or accrete and explained with additional specificity and detail through in turbofan engines. Ice crystals that accrete in an aircraft the use of the accompanying drawings, in which: engine system can cause serious engine operational prob- FIG. 1 is a flow diagram illustrating a process for engine lems and sometimes even catastrophic engine failures. If a icing mitigation and/or avoidance, according to an embodi- significant amount ofice were to accrete, the ice could result 40 ment of the present invention.

in a large blockage reducing the available aerodynamic area FIG. 2 illustrates a path that an ice particle follows within the compressor flow path and resulting in change of through an engine inlet, fan, low pressure compressor engine performance. Additionally, if the ice were to grow to blades, and core engine frame support strut, according to an a substantial size and shed, the ice would pose a risk of embodiment of the present invention.

catastrophic damage to the downstream engine components, FIG. 3 is a flow diagram illustrating a process for aircraft including the high-pressure compressor blades. The ice engine icing event avoidance through real-time simulation might also result in combustor flameout. To avoid ice and controls, according to an embodiment of the present accretion, the current practice is to circumnavigate, or fly invention.

around, the visible storm by a distance on the order of 100 FIG. 4 is a graph illustrating an icing wedge in three miles or more. dimensions, according to an embodiment of the present Thus, an alternative approach for detecting Ice Crystal invention.

Icing or accretion in the engines may be beneficial. FIG. 5 is a graph illustrating a rotated view of the icing wedge, according to an embodiment of the present inven- SUMMARY tion.

55 FIG. 6 is a graph illustrating an alternate rotated view of Certain embodiments of the present invention may pro- the icing wedge, according to an embodiment of the present vide solutions to the problems and needs in the art that have invention.

not yet been fully identified, appreciated, or solved by FIG.7 is a block diagram illustrating a computing system, current engine icing detection techniques. For example, according to an embodiment of the present invention.

some embodiments of the present invention generally per- 60 tain to a process for modeling engine aerothermodynamic DETAILED DESCRIPTION OF THE performance in real time, as the aircraft is flying, in any EMBODIMENTS atmospheric condition, and predict if there is a risk of ice accretion at the altitude of interest. When ice accretion is Some embodiments of the present invention generally detected, the process may alert the control system of the 65 pertain to aircraft engine icing event avoidance and mitiga- aircraft to switch into another mode to proactively mitigate tion through real-time simulation and controls to dramati- or avoid the risk of ice accretion. cally improve aviation safety and reduce operational costs.

US 10,184,405 BI

_►, Some embodiments include performing real-time analysis, the effects of the ice crystals through the controls system.

using sensors, engine system aerothermodynamic models, For example, the models may signal the control system to and the compressor flow analysis code, to determine the quickly modify the engine operating parameters such that potential and risk of ice accretion. If the risk of icing is accretion would be pre-emptively avoided before a signifi- determined, the control system is notified so the control 5 cant amount of accretion could occur. As the control system system can modify the engine operating parameters such modifies the engine parameters, the location of the potential that accretion can be proactively avoided. In addition, the ice accretion sites within the compression system would magnitude of change to the engine operating parameters move out of the icing wedge zone, thus avoiding the risk of may be small such that the change would be imperceptible accretion.

to both the pilot and passengers. This potentially enables the 10 In another embodiment, operating parameters may be pilot to safely fly through the ice crystal cloud. modulated by the control system and the real-time engine One or more embodiments may be applicable to turbofan and compressor models to mitigate the risk, such that no engines operating at altitudes exceeding 14,000 feet. In significant amount of accretion occurs for a long duration some embodiments, the approach is not only flexible and (on the order of 5-20 seconds, depending on the size of the adaptable to any turbofan engine, but also simple, low cost, 15 engine) at any specific location within the compression imperceptible engine adjustment, and improves flight safety. system. Thus, no significant amount of ice would accrete at For example, the analytics operate very quickly in real-time any one location. Therefore, any small amount ofice accre- to eliminate and/or mitigate the risk of ice accretion. Fur- tion that may occur at one location will quickly melt due to thermore, this approach may be implemented with any the fluctuating wet bulb temperatures at the location where aircraft turbofan engine and instruments, and the low-fidel- 20 icing was a risk within the compression system. The amount ity computational system is less complex than three-dimen- of thrust modification, or modulation of the engine param- sional CFD. Moreover, the risk of engine failure due to ice eters, by the control system may not be detrimental to the accretion may be eliminated and savings in fuel may be operation of the aircraft.

realized from a shorter path around a high-altitude storm In an alternative embodiment, an adequate amount of heat with convective clouds. 25 may be added to the targeted metal surfaces to avoid ice Engine Icing Mitigation and/or Avoidance Strategy accretion.

FIG. 1 is a flow diagram illustrating a process 100 for Engine System Model and Compressor Flow Analysis engine icing mitigation and/or avoidance, according to an Model embodiment of the present invention. Engine icing mitiga- The computational module may include a low-fidelity tion and/or avoidance process may involve the integration of 30 engine system model (e.g., aerothermodynamic cycle code) icing computational tools into engine controls system. This to provide the air flow, pressures, and temperatures for each process 100 may be used to mitigate the risk of an engine engine component, as well as the overall engine perfor- icing event through real-time simulation and control of the mance. The aerothermodynamic cycle code may include engine throttle setting. characteristic performance maps for each major engine At 102, the existence of high altitude ice crystals in the 35 component. The aerothermodynamic cycle code may pro- atmosphere are to be detected. The existence of ice crystals vide a bypass ratio between the air flow through the fan duct in the atmosphere can be detected by one or more of the and the air flow through the engine core for the actual engine following techniques. The first technique may include low- operating point during flight. The air flow calculated by the fidelity engine system and compressor flow analysis models aerothermodynamic cycle code and the fan rotational speed that execute in real-time as an integral part of the control 4o are provided as boundary conditions to the higher fidelity system. For example, the low-fidelity engine system and compressor flow analysis code (the "flow analysis code").

compressor flow analysis models constantly monitor and Simply put, the aerothermodynamic cycle code provides determine if the engine is operating at a nominal perfor- an engine system level model establishing performance of mance for the given atmospheric conditions and engine each major component, and provides boundary conditions to throttle setting. The low-fidelity engine system and com- 45 the compressor flow analysis code. These conditions may pressor flow analysis models can estimate whether any of include(1)engine air flow rate, bypass ratio, and core engine the compression system components are operating within flow rate; (2) fan, low pressure spool rotational speed:Nl; the "icing wedge", which indicates a risk of ice accretion. (3) high pressure spool (core engine) rotational speed:N2; High-fidelity engine system and compressor flow analysis and (4) fuel flow rate.

(CFD) tools that can run in real-time may also be imple- 50 Since the aerothermodynamic cycle code analysis lacks mented in some embodiments. the fidelity to provide the flow conditions within the stages The second technique may include an advanced on-board and blade rows, the flow analysis code is utilized to obtain external sensor and/or data monitoring system to detect the more detailed aerodynamic analysis of the engine compo- presence of ice crystals in the atmosphere. The third tech- nents. For example, the flow analysis code may compute the nique may include the controls system detecting changes in 55 flow field within the fan and compressor, as well as param- key engine parameters, which are different from the nomi- eters that indicate the risk ofice accretion. The key icing risk nal, such as the ratio of the fan speed to the core speed and parameters are as follows: the ice particle melt ratio, the an un-commanded change in fuel flow rate, indicating that static wet bulb temperature, and the ice-water flow rate to air ice crystals might be in the atmosphere. These may result in flow rate ratio (IWAR). The flow analysis code may also an un-commanded change in engine thrust. Finally, the 60 calculate the local value of relative humidity, as well as its fourth technique may include advanced ground-based radar, effects on the fluid properties of air and water vapor mixture, or satellite-based sensors, to detect ice crystals in the flight and the subsequent effects on compressor performance. The path of the aircraft. melt ratio in some embodiments refers to the local value of At 104, if ice crystals are detected and the risk of ice the liquid water to the total water ratio (ice+water) within the accretion is determined by any combination of the above 65 ice particle. For there to be a risk of ice accretion, the value techniques, the real-time engine system model and compres- of melt ratio should be greater than zero (e.g., 0.0<Melt sor flow analysis model may then be tasked with mitigating Ratio <-0.20). The ability to calculate the local relative

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humidity in each blade row is based on the initial value of humidity. Within the compressor flow analysis code, the specific humidity (mass of water/mass of air) at the engine relative humidity and the local static temperature of the air inlet, as well as the sublimation and evaporation of the are utilized to calculate the local wet-bulb temperature.

particles through the fan and low pressure compressor flow The functions described above are illustrated in FIG. 3 as path. 5 part of the detection and mitigation and/or avoidance pro- Simply put, the flow analysis code, which may include an cedure. FIG. 3 is a flow diagram illustrating a process 300 ice particle thermodynamic state analysis code (the "state for aircraft engine icing event avoidance through real-time analysis code"), may provide blade-row by blade-row com- simulation and controls, according to an embodiment of the pressor aerodynamic analysis, and enthalpy exchange present invention.

between the ice particle and air. The flow analysis code may io In FIG. 3, process 300 generally begins with detecting an also provide fluid properties of air and/or water vapor icing event at 302. This may occur by using external air data mixture, wet bulb temperature (static), IWAR, and ice par- sensor and/or instrumentation, controls monitoring engine ticle information such as temperature, melt ratio, enthalpy, parameters, advanced radar and/or satellite, or by using a evaporation, sublimation, and humidity. turbofan engine cycle code, with a compressor flow analysis In some embodiments, the state analysis code may track 15 code including an ice particle state analysis, and/or risk the heat exchange between the air and the ice particle and assessment via the icing wedge.Ificing risk is detected, then track the particle temperature, sublimation and evaporation. at 304, engine operating conditions are modulated to change Next, the state analysis code may compute the local ice the ice accretion location approximately at 5-20 second particle melt ratio (liquid to ice ratio) as the ice particle intervals, for example. At 306, the process may implement passes through the various components of the engine. In 20 the modulated engine operating conditions in the engine certain embodiments, this may begin at the engine inlet and controls software and/or hardware.

move through the fan and low pressure compressor blades For there to be a risk of ice accretion, the static wet bulb and stator vanes. The state analysis code may further cal- temperature must be within the minimum and maximum culate ice particle residence times through each component thresholds of static wet bulb temperature. This may be on the based on the air velocities through the component and the 25 order of freezing temperature (0 degree C.), to approxi- distance the particle travels. mately +3 degree Celsius above freezing (492 degree Rank- The specific humidity, the ice water content (IWC), and ine to 498 degree Rankine). Concurrently, the minimum particle diameter are specified at the inlet to the engine. The value ofIWAR must be on the order of 0.002 or greater for value for ice particle diameter can be calculated by a "break there to be a risk of ice accretion. Likewise, the state of the up model' or varied parametrically. Particle size after 30 ice particle should have some amount of liquid water breakup due to impact with the engine compression system component due to partial melting from heat transfer from the components that have been utilized in the computational air, or from other sources of liquid water. IfIWAR exceeds code may fall within a range of 1-20 microns in diameter, 0.002, then the growth rate of blockage can be nominally on and this size range generally results in a melt ratio that is the order of 0.01 cm/sec, and can vary almost linearly as a greater than zero. The non-zero melt ratio is a requirement 35 function ofIWAR. In some embodiments, blockage growth for ice to accrete onto stator vanes and metal surfaces within rate is defined as the growth rate of physical ice due to the flow path. After the flow conditions through the blade accretion, as well as the accompanying growth of the rows have been calculated by the flow analysis code, the boundary layer. If a significant amount of blockage growth static temperatures, pressures, and velocities are passed to were to occur, the blockage would result in reducing the the state analysis code to determine the rate of melting, 40 available aerodynamic area within the compressor flow path, sublimation, and evaporation, and thus, the local ice particle thus changing the performance of the engine. Additionally, melt ratio in each blade row. The calculations for sublima- if the ice were to grow to a substantial size and shed, the ice tion, melting, and evaporation may take into consideration would pose a risk of catastrophic damage to the downstream the local static temperatures, pressures, and residence times engine components, including the high pressure compressor as they traverse through the engine inlet, the fan-core and 45 blades. This might also result in combustor flameout. The low pressure compressor blade passages and gaps at the mid size of the ice particle utilized in the compressor flow span location, the gooseneck duct and the support strut analyses may be representative of the size distributions upstream of the high pressure compressor. experienced after impact with the engine components, FIG. 2 illustrates a flow 200 of an ice particle path Pl at including the spinner, fan-rotor, and LPC blading. The an engine inlet, through a typical fan 202, low pressure 50 particle size after breakup can include a large amount of compressor blades 204, and to the core engine frame support small particles on the order of from 1-20 microns in diam- strut 206, according to an embodiment of the present inven- eter. The icing wedge below showing the zone oficing risk, tion. The low pressure compressor may include one or more is defined graphically in terms of static wet bulb tempera- axial compressor stages. In FIG. 2, an illustration of ice ture, IWAR, and the blockage growth rate.

particle path Pl through the rotor blades in the relative frame 55 FIG. 4 is a graph illustrating the icing wedge, according of reference, and the stator vanes in the absolute frame of to an embodiment of the present invention. More specifi- reference, is provided. The calculations of ice particle sub- cally, graph 400 shows the the blockage growth rate (due to limation, melt, and evaporation are performed from the ice accretion and boundary layer growth) as a function of leading to the trailing edge of each rotor and stator, as well IWAR and static wet bulb temperature.

as through the axial gap between the blades. These are 60 FIG. 5 is a graph illustrating a rotated icing wedge, calculated as a function of air velocity, distance traveled and according to an embodiment of the present invention. In the residence time. The distances traveled are assumed to graph 500, the relationship between the aerodynamic block- equal the chord length of each rotor and stator, as well as the age due to the accretion ofice in the low pressure compres- gap between the rotor and stator. The amount of water sor versus the local value of static wet bulb temperature is addition to the air due to sublimation and evaporation 65 shown. More specifically, graph 500 shows the icing wedge increases the local value of specific humidity, thus together rotated to show the minimum and maximum thresholds of with the local static temperature, effecting the local relative static wet bulb temperature indicating whether there is a risk

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of ice accretion and resulting blockage growth rate. The the-shelf semiconductors such as logic chips, transistors, or limits of static wet bulb temperature that determine whether other discrete components. A module may also be imple- there is a risk of ice and boundary layer growth are nomi- mented in programmable hardware devices such as field nally between freezing temperature (0 degree Celsius) to programmable gate arrays, programmable array logic, pro- approximately +3 degree Celsius above freezing(492 degree 5 grammable logic devices, graphics processing units, or the Rankine to 498 degree Rankine). like.

FIG. 6 is a graph illustrating a rotated view of the A module may also be at least partially implemented in three-dimensional icing wedge, according to an embodiment software for execution by various types of processors. An ofthe present invention.In graph 600,icing wedge is rotated identified unit of executable code may, for instance, com- to show the blockage growth rate due to ice accretion and io prise one or more physical or logical blocks of computer boundary layer, as a function ofIWAR.This view shows the instructions that may,for instance, be organized as an object, relationship of the expected aerodynamic blockage due to procedure, or function. Nevertheless, the executables of an ice accretion, as a function of the amount of ice crystals identified module need not be physically located together, entering the engine: IWAR. Values of IWAR above 0.002 but may comprise disparate instructions stored in different can result in a risk of ice accretion, and a corresponding 15 locations which, when joined logically together, comprise blockage growth rate, if the static wet bulb temperature is the module and achieve the stated purpose for the module.

concurrently between freezing temperature (0 degree Cel- Further, modules may be stored on a computer-readable sius) to approximately +3 degree Celsius above freezing medium, which may be, for instance, a hard disk drive, flash (492 degree Rankine to 498 degree Rankine). device, random access memory (RAM), tape, or any other FIG. 7 illustrates a block diagram of a computing system 20 such medium used to store data.

700 for detecting ice and processing an icing event, accord- Indeed, a module of executable code could be a single ing to one embodiment of the present invention. Computing instruction, or many instructions, and may even be distrib- system 700 may include a bus 705 or other communication uted over several different code segments, among different mechanism configured to communicate information, and at programs, and across several memory devices. Similarly, least one processor 710, coupled to bus 705, configured to 25 operational data may be identified and illustrated herein process information. At least one processor 710 can be any within modules, and may be embodied in any suitable form type of general or specific purpose processor. Computing and organized within any suitable type of data structure. The system 700 may also include memory 720 configured to operational data may be collected as a single data set, or may store information and instructions to be executed by at least be distributed over different locations including over differ- one processor 710. Memory 720 can be comprised of any 30 ent storage devices, and may exist, at least partially, merely combination ofrandom access memory("RAM"),read only as electronic signals on a system or network.

memory ("ROM"), static storage such as a magnetic or It will be readily understood that the components of optical disk, or any other type of computer readable various embodiments of the present invention, as generally medium. Computing system 700 may also include a com- described and illustrated in the figures herein, may be munication device 715, such as a network interface card, 35 arranged and designed in a wide variety of different con- configured to provide access to a network. figurations. Thus, the detailed description of the embodi- The computer readable medium may be any available ments, as represented in the attached figures, is not intended media that can be accessed by at least one processor 710. to limit the scope of the invention as claimed, but is merely The computer readable medium may include both volatile representative of selected embodiments of the invention.

and nonvolatile medium, removable and non-removable 40 The features, structures, or characteristics ofthe invention media, and communication media. The communication described throughout this specification may be combined in media may include computer readable instructions, data any suitable manner in one or more embodiments. For structures, program modules, or other data and may include example, reference throughout this specification to "certain any information delivery media. embodiments," "some embodiments," or similar language At least one processor 710 can also be coupled via bus 45 means that a particular feature, structure, or characteristic 705 to a display 740, such as a Liquid Crystal Display described in connection with the embodiment is included in ("LCD"). Display 740 may display icing detection informa- at least one embodiment of the present invention. Thus, tion to the user. A keyboard 745 and a cursor control unit appearances of the phrases "in certain embodiments," "in 750, such as a computer mouse or a smart pen, may also be some embodiment," "in other embodiments," or similar coupled to bus 705 to enable the user to interface with 50 language throughout this specification do not necessarily all computing system 700. refer to the same group of embodiments and the described According to one embodiment, memory 720 may store features, structures, or characteristics may be combined in software modules that may provide functionality when any suitable manner in one or more embodiments.

executed by at least one processor 710. The modules can It should be noted that reference throughout this specifi- include an operating system 725 and an icing detection 55 cation to features, advantages, or similar language does not module 730, as well as other functional modules 735. imply that all of the features and advantages that may be Operating system 725 may provide operating system func- realized with the present invention should be or are in any tionality for computing system 700. Because computing single embodiment of the invention. Rather, language refer- system 700 may be part of a larger system, computing ring to the features and advantages is understood to mean system 700 may include one or more additional functional 60 that a specific feature, advantage, or characteristic described modules 735 to include the additional functionality. in connection with an embodiment is included in at least one It should be noted that some of the system features embodiment of the present invention. Thus, discussion of described in this specification have been presented as mod- the features and advantages, and similar language, through- ules, in order to more particularly emphasize their imple- out this specification may, but do not necessarily, refer to the mentation independence. For example, a module may be 65 same embodiment.

implemented as a hardware circuit comprising custom very Furthermore, the described features, advantages, and large scale integration (VLSI) circuits or gate arrays, off- characteristics of the invention may be combined in any

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suitable manner in one or more embodiments. One skilled in at least one offluid properties of air and fluid properties the relevant art will recognize that the invention can be of a water vapor mixture; practiced without one or more of the specific features or at least one of a wet bulb temperature, an ice water flow advantages of a particular embodiment. In other instances, rate, and an air flow rate; and, additional features and advantages may be recognized in 5 at least one of a thermodynamic state of an ice particle certain embodiments that may not be present in all embodi- and an estimate of a water to ice ratio of the ice ments of the invention. particle.

One having ordinary skill in the art will readily under- 7. The process of claim 1, wherein the detecting the stand that the invention as discussed above may be practiced existence ofice crystals further comprises using at least one with steps in a different order, and/or with hardware ele- io ofan on board external sensor and a data monitoring system.

ments in configurations which are different than those which 8. The process of claim 1, wherein the detecting the are disclosed. Therefore, although the invention has been existence of ice crystals further comprises using a controls described based upon these preferred embodiments,it would system to detect changes in one or more engine parameters be apparent to those of skill in the art that certain modifi- indicative of ice crystals within a given atmosphere.

cations, variations, and alternative constructions would be 15 9. The process of claim 1, wherein the detecting the apparent, while remaining within the spirit and scope of the existence ofice crystals further comprises using at least one invention. In order to determine the metes and bounds of the of an advanced ground based radar and satellite sensors to invention, therefore, reference should be made to the detect ice crystals in a flight path of the aircraft.

appended claims. 10. A process for mitigating or proactively avoiding an 20 aircraft engine icing event, comprising: The invention claimed is: integrating one or more icing computational modules into 1. A process for mitigating or proactively avoiding an engine control systems, wherein the integrating of the aircraft engine icing event, comprising: one or more icing computational modules into engine detecting an existence ofice crystals in an atmosphere, by control systems comprises: one or more sensors on board an aircraft, in real time; 25 detecting an existence of high altitude ice crystals in an when ice crystals in the atmosphere are detected: atmosphere, by one or more sensors on board an modulating one or more engine operating conditions to aircraft, in real time, wherein the detecting of the change an ice accretion location; and existence of high altitude ice crystals in the atmo- modulating, by a control system and real-time engine sphere comprises determining, by an engine system thermodynamic cycle model and compressor flow so and compressor flow analysis model, in real-time, if model, one or more operating parameters to proac- an engine is operating at a nominal performance for tively mitigate the risk of ice accretion such that no a given atmospheric condition and an engine throttle significant amount of ice accretion occurs for a 5 to system; 20 second duration at any specific location within a mitigating or proactively avoiding in real time effects compression system; and 35 ofice crystals through the engine control systems by implementing one or more modulated engine operating modulating one or more engine operating conditions conditions in engine controls to proactively mitigate the to change an ice accretion location, when ice crystals occurrence of an aircraft engine icing event. in the atmosphere are detected, and implementing 2. The process of claim 1, wherein the detecting of the one or more modulated engine operating conditions existence of ice crystals comprises determining, by an 40 in engine controls.

engine system and compressor flow analysis model, in 11. The process of claim 10, wherein the determining by real-time if an engine is operating at a nominal performance the engine system and compressor flow analysis model for a given atmospheric condition and an engine throttle further comprises system. determining if any one of compression system compo- 3. The process of claim 2, wherein the determining by the 45 nents are operating within an icing wedge, the icing engine system and compressor flow analysis model further wedge indicative of a risk of ice accretion within the comprises engine.

determining if any one of compression system compo- 12. The process of claim 11, further comprising: nents are operating within an icing wedge, the icing providing, by an aerothermodynamic module of the wedge indicative of a risk of ice accretion within the 50 engine system and compressor flow analysis model, an engine. engine system level model; 4. The process of claim 3, further comprising: establishing, by the aerothermodynamic module of the providing, by an aerothermodynamic module of the engine system and compressor flow analysis model, engine system and compressor flow analysis model, an performance of each major component of an engine; engine system level model; 55 and establishing, by the aerothermodynamic module of the providing boundary conditions to a compressor flow engine system and compressor flow analysis model, analysis module.

performance of each major component of an engine; 13. The process of claim 12, further comprising: and providing, by the flow analysis module, blade-row by providing boundary conditions to the compressor flow 60 blade-row compressor aerodynamic analysis and analysis module. enthalpy exchange between ice particle and air.

5. The process of claim 4, further comprising: 14. The process of claim 13, further comprising: providing, by the flow analysis module, blade-row by providing, by the flow analysis module: blade-row compressor aerodynamic analysis and at least one offluid properties of air and fluid properties enthalpy exchange between ice particle and air. 65 of a water vapor mixture; 6. The process of claim 5, further comprising: a wet bulb temperature and at least one of an ice water providing, by the flow analysis module: flow rate and an air flow rate; and

US 10,184,405 BI

11 12

at least one of a thermodynamic state of an ice particle and an estimate of the water to ice ratio of the particle.

15. The process of claim 10, wherein the detecting of the existence of high altitude ice crystals in the atmosphere 5 further comprises using at least one of an on board external sensor and a data monitoring system to detect presence ofice crystals in a given atmosphere.

16. The process of claim 10, wherein the detecting of the existence of high altitude ice crystals in the atmosphere io further comprises using a controls system to detect changes in one or more engine parameters indicative of ice crystals within a given atmosphere.

17. The process of claim 10, wherein the detecting of the existence of high altitude ice crystals in the atmosphere 15 further comprises using advanced ground based radar, sat- ellite sensors, or both, to detect ice crystals in a flight path of the aircraft.

18. The process of claim 10, wherein, when the existence of high altitude ice crystals in the atmosphere is detected, 20 modulating, by a control system and real-time engine ther- modynamic cycle model and compressor flow model, one or more operating parameters to proactively mitigate the risk of ice accretion such that no significant amount ofice accretion occurs for a 5 to 20 second duration at any specific location 25 within a compression system.