Document
NASA/TM—1998-208482 AIAA–98–3756
The High Stability Engine Control (HISTEC)
Program: Flight Demonstration Phase
John C. DeLaat Lewis Research Center, Cleveland, Ohio Robert D. Southwick and George W. Gallops United Technologies Corporation, Pratt & Whitney, West Palm Beach, Florida John S. Orme Dryden Flight Research Center, Edwards, California
July 1998
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NASA/TM—1998-208482 AIAA–98–3756
The High Stability Engine Control (HISTEC)
Program: Flight Demonstration Phase
John C. DeLaat Lewis Research Center, Cleveland, Ohio Robert D. Southwick and George W. Gallops United Technologies Corporation, Pratt & Whitney, West Palm Beach, Florida John S. Orme Dryden Flight Research Center, Edwards, California Prepared for the 34th Joint Propulsion Conference cosponsored by AIAA, ASME, SAE, and ASEE Cleveland, Ohio, July 12–15, 1998 National Aeronautics and Space Administration Lewis Research Center
July 1998
Trade names or manufacturers’ names are used in this report for identification only. This usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration.
Available from NASA Center for Aerospace Information National Technical Information Service 7121 Standard Drive 5287 Port Royal Road Hanover, MD 21076 Springfield, VA 22100 Price Code: A03 Price Code: A03 AIAA-98-3756 THE HIGH STABILITY ENGINE CONTROL (HISTEC) PROGRAM: FLIGHT DEMONSTRATION PHASE John C. DeLaat NASA Lewis Research Center 21000 Brookpark Road Cleveland, Ohio 44135 Robert D. Southwick, George W. Gallops United Technologies Corporation Pratt & Whitney P.O. Box 109600 W. Palm Beach, Florida 33410 John S. Orme NASA Dryden Flight Research Center Edwards, California 93523 ABSTRACT demonstration of the HISTEC technologies has significantly reduced the risk of transitioning the Future aircraft turbine engines, both commercial and technology to tactical and commercial engines.
military, must be able to accommodate expected increased levels of steady-state and dynamic engine- face distortion. The current approach of incorporating NOMENCLATURE sufficient design stall margin to tolerate these increased levels of distortion would significantly reduce Aj - Nozzle Area performance. The objective of the High Stability ACTIVE - Advanced Control Technology for Engine Control (HISTEC) program is to design, develop, and flight-demonstrate an advanced, integrated Integrated Vehicles engine control system that uses measurement-based α - Angle-of-Attack estimates of distortion to enhance engine stability. The resulting distortion tolerant control reduces the required β - Angle-of-Sideslip design stall margin, with a corresponding increase in CEDU - Comprehensive Engine Diagnostic Unit performance and decrease in fuel burn. The HISTEC concept has been developed and was successfully flight DES - Distortion Estimation System demonstrated on the F-15 ACTIVE aircraft during the EPR - Engine Pressure Ratio summer of 1997. The flight demonstration was planned and carried out in two phases, the first to show HCF - High Cycle Fatigue distortion estimation, and the second to show distortion HSCT - High Speed Civil Transport accommodation. Post-flight analysis shows that the HISTEC technologies are able to successfully estimate HISTEC - High Stability Engine Control and accommodate distortion, transiently setting the stall IDEEC - Improved Digital Electronic Engine Control margin requirement on-line and in real-time. This allows the design stall margin requirement to be ID - Inner Diameter reduced, which in turn can be traded for significantly OD - Outer Diameter increased performance and/or decreased weight. Flight PLA - Power Lever Angle Copyright 1998 by the American Institute of Aeronautics and SMC - Stability Management Control Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty-free license WACC - Calculated Total Air Flow to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are reserved by the copyright owner.
1 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics INTRODUCTION engine customers during the Advanced Control 2,3,4,5 Concepts study sponsored by NASA. The far term Background approach is to increase the amount of operational stall margin available by actively controlling the onset of Future aircraft turbine engines, both commercial and stall, otherwise know as active stall control or active 6,7,8,9,10 military, must be able to successfully accommodate stability control. The nearer term approach is to expected increased levels of steady-state and dynamic transiently increase the stall margin requirement on-line engine-face distortion. Advanced tactical aircraft are as the destabilizing effect, in this case engine face likely to use thrust vectoring for enhanced aircraft pressure distortion, is encountered. This approach, maneuverability. As a result, the propulsion system will distortion tolerant control, allows a reduction in the see more extreme aircraft angle-of-attack and sideslip required design stall margin by an amount on the order levels than currently encountered with present-day of the destabilizing impact of the distortion.
aircraft. Also, the mixed-compression inlets needed for the High Speed Civil Transport (HSCT) will likely The HISTEC Approach encounter disturbances similar to those seen by tactical aircraft in addition to planar pulse, inlet buzz, and high The distortion tolerant control approach developed for distortion levels at low flight speed and off-design the High Stability Engine Control (HISTEC) program is operation. The result of these increased levels of shown in Figure 2. The approach uses a small number distortion is generally a decrease in propulsion systems of engine-face pressure measurements to accurately performance, and more importantly, a lessening of the estimate the actual distortion present. From this stable flow range of the compressor. Current gas pressure-based distortion estimate, an onboard stability turbine engine design practice is to base fan and audit requests a time-varying stall margin requirement.
compressor stall margin requirements on the worst case The engine controller then accommodates the distortion stack-up of destabilizing factors which include external by acting upon the current stall margin requirement factors such as inlet distortion as well as internal factors supplied by the onboard stability audit. The HISTEC such as large tip clearances (Figure 1) . A stability approach includes three major elements: Engine Face audit is defined and maintained during the engine Pressure Sensors; the Distortion Estimation System development process to account for the effects of each (DES); and the Stability Management Control (SMC).
known destabilizing factor. The stability audit stacks up the worst case stall margin losses from each of the The engine face pressure sensors consist of a small known factors, adds margin for engine-to-engine number of high-response, wall static pressure variability, and ensures that fan and compressor have transducers. There are five sensors at the engine face some remaining stall margin under this worst case outer diameter (OD) and five sensors electrically stack-up. However, this approach, especially in the averaged to a single measurement at the inner diameter case of future engines with increased levels of (ID). The DES uses these high response pressure distortion, results in an increase in design stall margin measurements to calculate in real time the indicators of requirement with a corresponding reduction in type and extent of distortion.
performance and/or increase in weight.
The DES is an aircraft mounted, high speed processor NASA is currently pursuing two research approaches that estimates the amount and type of distortion present which were confirmed beneficial by NASA's aircraft and the impact of that distortion on the propulsion Reference Variability Stall Line Reynold’s # Pressure Clearance Effects Ratio Distortion Control Tolerances Controller Pressure Ratio Maximum Airflow Figure 1 - Stall Margin Requirements 2 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics Engine Face Pressure Sensors α,β F100-PW-229 Flight Control Data for Actuator Predicted Commands α, β Trim DISTORTION STABILITY MANAGEMENT Commands ESTIMATION SYSTEM CONTROL Distortion Estimates Onboard Stability Audit Engine Sensitivities Stall Margin Control Laws Figure 2 - HISTEC Distortion Tolerant Control Approach system. The DES breaks the distortion, typically a The HISTEC Program three-dimensional phenomenon, into radial, circumferential, and planar components. Each HISTEC is a five year program sponsored by NASA component is passed through an appropriate distortion Lewis Research Center in Cleveland, Ohio. Program partners include NASA Dryden Flight Research Center, sensitivity function to arrive at a fan and compressor pressure ratio surge margin debit or pressure ratio limit which accomplished the flight demonstration; Pratt & trim. Because the response of the engine and control is Whitney, which developed the technical concepts and of lower bandwidth than the distortion phenomenon and the systems for flight demonstration; Boeing (formerly McDonnell Douglas), which helped integrate the because there is an additional delay for the distortion algorithm computations, the DES also uses maneuver HISTEC systems onto the flight test vehicle; and the information from the flight control to predict angle-of- U.S. Air Force, which provided flight systems, engines, attack and angle-of-sideslip in order to anticipate high and the aircraft assets. The HISTEC program consists inlet distortion conditions. Dynamic compensation of three phases: Phase I - Algorithm Development, using the maneuver information is applied to the fan and Phase II - Concept Validation and System compressor ratio limit trims. From the measurements, Development, and Phase III - Engine/Flight and from the maneuver information, the DES Demonstration. A timeline for the program is shown in determines the effects of the distortion on the Figure 3. HISTEC Phase I "Algorithm Development", propulsion system and the corresponding engine match completed in 1994, successfully defined the point necessary to accommodate it. requirements for, and designed the algorithms necessary for the Distortion Estimation System (DES). Under The output of the DES consists of fan and compressor Phase IIA - "Concept Validation”, the integrated DES pressure ratio trim commands which are then algorithms and distortion accommodation algorithms communicated to the SMC. The SMC is contained in (High Stability Control Laws) were designed and the engine mounted Improved Digital Electronic Engine validated. This integration testing used a detailed Control (IDEEC). The SMC performs a stability audit nonlinear aero-thermal transient model of the F100- online using the trims from the DES and then PW-229 engine and an emulator of the F-15 aircraft accommodates the distortion through the production inlet which estimates engine inlet pressures based on engine actuators. The approach combining the DES and aircraft flight condition, angle-of-attack, and angle-of- SMC results in a distortion tolerant control which sideslip. The simulation testing confirmed that the enables a reduced design stall margin requirement with HISTEC system should be able to sense inlet distortion, a corresponding increase in performance and decrease determine the effect on engine stability, and in fuel burn. accommodate for distortion by maintaining adequate engine surge margin.
3 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics 1993 1994 1995 1996 1997 1998 1999 2000 Name Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Phase I Concept Feasibility Demonstrated Phase IIa Distortion Estimation System Algorithms Validated High Stability Control Laws Validated Instrumented Inlet Complete Phase IIb Prelimary Design Review Critical Design Review Distortion Tolerant Control System Demonstrated Phase III Flight Safety Board Briefing First Flight 7/15/97 Open-Loop Flight Test Complete Closed-Loop Flight Test Complete 8/26/97
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Analysis and Reporting Complete Figure 3 - HISTEC Program Timeline This paper provides a summary of HISTEC Phase IIb - the engine face pressure profile; validating the ability of Systems Development, and Phase III - Engine/Flight the DES to accurately estimate in flight the amount and Demonstration. During these final phases of the type of distortion and its impact on engine stability; and HISTEC program, the systems necessary to flight to demonstrate the ability of the SMC to conduct an demonstrate the HISTEC approach were developed and accurate on-line stability audit and provide good validated through systems testing and ground engine distortion accommodation in the stability management test. The systems were installed on the F-15 Advanced control laws. The second specific objective is to Control Technology for Integrated Vehicles (ACTIVE) augment the available database of dynamic flight aircraft at NASA Dryden and the HISTEC flight distortion data.
demonstration was accomplished in the summer of 1997. In this paper, the background and objectives for the flight demonstration are given. The HISTEC flight FLIGHT SYSTEMS DEVELOPMENT systems hardware and software are described and the efforts necessary to validate these systems are In order to accomplish the HISTEC flight discussed. An overview of the flight test planning is demonstration, systems for implementing the HISTEC given. Finally, a summary of the flight testing and flight approach on the F-15 ACTIVE aircraft were developed, test results is provided. In companion papers, the validated, and installed on the aircraft. These systems details of the effort necessary to install and demonstrate include the instrumented inlet case, the Distortion the HISTEC systems are given, and the detailed flight Estimation System hardware and software, and the test results are presented . Stability Management Control software.
Instrumented Inlet Case FLIGHT TEST OBJECTIVES The HISTEC instrumented inlet case, designed and The overall objective of the HISTEC program is to fabricated during HISTEC Phase IIa, is a production develop and flight demonstrate an advanced high F100-PW-229 fan inlet case modified to incorporate the stability integrated engine control system which uses HISTEC engine face pressure sensors (Figure 4) . The real-time, measurement-based estimation of distortion sensors which are used by the Distortion Estimation to enhance engine stability. For the flight System include five wall static pressure transducers at demonstration phase of the program, there are two the engine face outer diameter (OD) and five at the specific objectives. The first specific objective is to inner diameter (ID) electrically averaged to a single demonstrate the distortion tolerant control approach measurement. Thirty-five total pressure sensors are developed for HISTEC. This demonstration includes located on 7 inlet case struts, 5 sensors per strut, validating the ability of the measurement system to distributed radially on each strut by equal flow path provide sufficient information to the DES to reconstruct area. These research sensors provide a reference for 4 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics DES LE DAT DAT LE LE DES DES DAT LE LE DES DES LE LE DAT 67 22 8. cd r PW229 Instrumented Fan Inlet Case Forward Looking Aft Legend: DES - Dist Est System Transducers DAT - Data System Transducers LE - Vane Leading Edge Pt(5) and Tt(1) Figure 4 - Instrumented Inlet Case validating the DES sensors. For temperature processing techniques used in the DES algorithms very compensation, seven total temperature probes are well. For HISTEC the CEDU was airframe mounted.
located approximately mid-span on the same inlet struts as the total pressure sensors. Finally, wall static Pressure Sensors pressure sensors located at nine locations (5 locations Measurement the same as the DES sensors, 4 additional locations) Conversion provide additional spatial resolution for investigating if Inlet Pressure Pattern the number of DES pressure sensors is sufficient.
Pattern Distortion Estimation System (DES) Classification Spatial/Temporal Components The DES algorithms follow the basic concepts of Distortion traditional stability audit methodology (Figure 5).
Sensitivity This methodology consists of standards for Stall Pressure Ratio (SPR) measurement, pattern classification, and computation of Debit stability debits and relies on the key assumption of superposition of stability debits for individual Figure 5 - Traditional Stability Audit Methodology circumferential, radial, and planar dynamic distortion components. The DES algorithms as implemented rely Stability Management Control (SMC) on digital signal processing techniques to perform spatial transforms for classifying the amount and type of The SMC algorithms build on the bill-of-material F100- distortion present, and temporal transforms (FFT) to PW-229 control laws. For HISTEC, the SMC then obtain the frequency content of each of the spatial algorithms added an onboard stability audit to account distortion components. A detailed description of the for the destabilizing influence of distortion (as DES algorithms is contained in Reference 13 .
computed by the DES) and other factors. Advanced control laws manage the amount of stall margin The F119 Group 1 Comprehensive Engine Diagnostic remaining in the fan and high pressure compressor Unit (CEDU) was chosen during HISTEC Phase IIa (Figure 6). The SMC algorithms were incorporated from among several candidates for the DES because of into a production F100-PW-229 Improved Digital its flight-quality design and sufficient I/O and Electronic Engine Control (IDEEC). The IDEEC on throughput capability. The CEDU contains a digital the right-hand engine on the F-15 ACTIVE was signal processor which accommodated the signal replaced with the IDEEC containing the HISTEC SMC 5 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics algorithms. Communications between the IDEEC and evaluated for the correct distortion accommodation DES were accomplished through the aircraft 1553 data response to signals emulating pressure ratio trims from bus. the DES. In addition, the functioning of the onboard stability audit was evaluated. Finally, verification testing was done to ensure that production engine Fan Stall Margin functionality was maintained with the HISTEC stability Loss Due To Distortion Fan accommodation inactive. To validate the integrated Stall Margin FAN Remaining STABILITY DES and SMC, system integration testing was first From STABILITY AUDIT MANAGEMENT Distortion To conducted stand-alone using an emulator of the aircraft CONTROL Estimation Engine LAWS Compressor and its associated communications systems. Next, System Actuators Stall Margin COMP.
operation of the integrated HISTEC systems was Remaining STABILITY AUDIT Compressor verified during uninstalled ground engine testing. This Stall Margin Loss Due To Distortion was the same test that flight cleared the instrumented inlet case. Vehicle integration testing was then done using the aircraft hardware-in-the-loop bench at Figure 6 - Stability Management Control McDonnel Douglas Aircraft (now Boeing Phantom Works). Finally, installed ground testing was performed in the F-15 ACTIVE aircraft to test correct FLIGHT SYSTEMS VALIDATION integration of the HISTEC systems onto the aircraft, to verify correct operation of the flight data systems, and During the systems development phase of HISTEC to clear all HISTEC systems for flight. Detailed (Phase IIb), the design of the instrumented inlet case descriptions of the ground testing and ground test fabricated during Phase IIa was refined in response to results are provided in Reference 14 .
some minor structural deficiencies discovered during High Cycle Fatigue (HCF) testing of an inlet case strut modified and instrumented like the flight inlet case. At FLIGHT TEST resonant modes and frequencies typical of on-engine operation, minor cracking was discovered at some of Planning the sites where the research total pressure transducers are installed in the leading edge of the inlet guide vane As mentioned earlier, the overall objective of the struts. The electro discharge machining used to install HISTEC program is to develop and flight demonstrate the holes to house the HISTEC instrumentation had an advanced high stability integrated engine control produced a local through-wall heat-affected zone. The system which uses real-time, measurement-based cause of the cracking was attributed to the concentrated estimation of distortion to enhance engine stability.
stresses exceeding the capability of the locally degraded Specific objectives for the flight test included: material. Re-design and re-work of the transducer 1) Augmenting the existing databases for distortion installations alleviated the cracking problem during data by gathering inflight dynamic distortion data from HCF testing. The repair scheme was then applied to the the instrumented inlet case and engine; and 2) Flight flight inlet case. Flight clearance of the inlet case was validating a distortion tolerant engine control consisting accomplished through engine ground testing on the of the engine face pressure measurements, distortion M37 sea-level stand at Edwards Air Force Base.
estimation in the DES, and distortion accommodation in the SMC. In order to satisfy these specific objectives, Also during Phase IIb, the DES and SMC were the flight test program was divided into two phases.
incorporated into the F-15 ACTIVE aircraft flight The first phase would quantify inlet distortion at steady systems architecture, and the detailed state and transient flight conditions; correlate measured hardware/software design and implementation was inlet distortion from total pressure measurements to accomplished to incorporate the HISTEC systems onto DES pressure measurements; demonstrate acceptable the aircraft. In the DES, the executive software, DES accuracy; and define any DES software changes distortion estimation algorithms, and data required before the second phase. The second phase communication software were coded and tested. In the would then demonstrate accurate inlet distortion SMC, the onboard stability audit, stability management estimation at steady state and transient flight conditions; control laws, and modified data communications demonstrate functional engine trim capability to software were coded and tested. To validate the SMC accommodate inlet distortion; and demonstrate adequate control laws, a ground engine test was conducted on a transient aircraft angle of attack and sideslip prediction sea-level test stand at Pratt & Whitney. The SMC was based on aircraft control inputs and adequate resultant 6 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics x 10 Steady Flight 50 • Straight & level 5 Power Levels (Mil-Idle) • Alpha = -4, -2.5, 5, 10, 15, 20 deg • Beta = + and - Limit Altitude, ft 30 Transient Flight • Alpha sweeps to 25 deg at low and high rate • Beta sweeps to limit • Combination Alpha & Beta sweeps to limit Maneuver Transients • Basic fighter maneuvers • NASA defined maneuvers 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Mach Number Figure 7 - HISTEC Flight Envelope engine trim lead terms to ensure inlet distortion some negative angle-of-attack points which were accommodation. precluded due to aircraft systems problems at negative g-forces. Over 65 Gbytes of high-quality data were The HISTEC flight test envelope is shown in Figure 7 . recorded onboard the aircraft and/or telemetered to A test point matrix consisting of 106 test points at ground recording stations. All HISTEC flight research various subsonic and supersonic flight conditions was objectives were successfully accomplished. A detailed developed to carry out the two phase flight test description of the flight test execution is contained in discussed above. Flight conditions were chosen so that Reference 14 .
the majority of testing would be accomplished with inlet pressures in the middle of the transducers’ range. This inlet pressure (~13 psia) also approximates the pressure SUMMARY OF FLIGHT DEMONSTRATION on the ground where transducer calibrations were done. RESULTS Mach numbers were chosen which approximated typical stability audit points. Engine operating points were Analysis of the flight test data indicates that both the chosen to provide a variety of aiflows, which in turn Distortion Estimation algorithms and the stability provided a wide variation in distortion pressure margin management elements of the overall HISTEC control system performed as designed. Post-flight patterns. Included in the test point matrix were aircraft maneuvers to generate high levels of distortion. These analysis has been divided into three main areas. First, it was necessary to determine if the DES wall-static included steady and transient high angle-of-attack ( α ) transducers were able to reconstruct the engine face and angle-of-sideslip ( β ) flight, wind-up turns, split-S pressure profile with enough fidelity to determine the maneuvers, and take-offs. These allowed a thorough amount and type of distortion present. Second it was demonstration of distortion estimation in the first phase necessary to show that the DES is able to compute and of distortion accommodation in the second phase of distortion descriptors and apply the appropriate testing.
sensitivity functions to provide the correct stall margin pressure ratio debit to the onboard stability audit in the Demonstration SMC. And finally, it was necessary to show that the onboard audit was able to apply the distortion stability Flight testing commenced on July 15, 1997, and the first debit to the control laws in order to accommodate phase was completed after 6 flights (~7 flight hours) conditions of high distortion. A summary of the post- over a 3½ week period. The second phase, consisting flight analysis is presented here. Detailed analysis of 4 flights (~3 flight hours), was completed on August results are contained in Reference 15 .
26, 1997. Overall, the execution of the flight test was extremely successful. All test points were flown except 7 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics HISTEC Flight Test Data Analysis, flt1775 adr1023 o o 20K/.6, α =21 , β =0 , wacc=248 lb/s wacc = 100% of mil power Right Hand Engine, Aft Looking Forward DES Static Pressure Sensors Research Total Pressure Sensors Normalized Total Pressure 0.8 0.85 0.9 0.95 1 1.05 1.1 0.8 0.85 0.9 0.95 1 1.05 1.1 Figure 8 - Measurement System Results Engine Face Pressure Measurements Fourier series coefficients. As can be seen from the qualitative comparison in the figure, the pressure profiles for this high airflow, high angle-of-attack (and Figure 8 shows a comparison of the face pressure profile computed from the six DES pressure thus high-distortion) condition compare favorably. This measurements and the corresponding pressure profile indicates that the DES wall static pressure sensors are computed from the thirty-five research total pressure able to pick up the important features for estimating sensors. distortion.
The pressure profiles were calculated by first fitting Distortion Estimation Fourier series descriptors to the sensor data, similar to the calculations done in the DES. The pressure profile Next the stall margin debit due to distortion as was then back-calculated from the resulting spatial calculated by the DES in flight from the DES sensors Flight 1775 DP19, 20, 36, 23, 24 at 20K/0.6, Mil Flight 1775 DP 22: AOA sweep from 5 to 25 degrees at 20K/0.6, Mil DES ARP1420 (a) Steady angle-of-attack (b) Angle-of-attack sweep Figure 9 - Distortion Estimation Results (vertical scale omitted to protect proprietary data) 8 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics was compared to the stall margin debit calculated off- line from flight data for the 35 research sensors using the industry-standard ARP1420 methodology. In Figure 9(a) , this comparison is shown for time- averaged data for five levels of steady angle-of-attack (AOA) between approximately 5 and 23 degrees. The first important result seen in the figure is that the stall margin debit due to distortion is correctly estimated as increasing with increasing AOA. Second, the stall margin debit calculated in flight by the DES is quite similar in magnitude and slope to that computed by the ARP1420 method. In Figure 9(b) , this same comparison is made for time-history data for an AOA sweep maneuver from approximately 5 to 25 degrees.
Again the estimated stall margin debit due to distortion is correctly shown to be increasing for increasing angle Figure 10 - Split-S Maneuver of attack, and the DES in-flight results compare favorably to the ARP1420 results. The time-history data also shows that the DES signal processing Figure 11 shows the successful in-flight distortion algorithms tend to smooth the calculated stall margin accommodation during a Split-S maneuver . Figure debit. The ARP1420 method, computed at each time 11(a) shows the angle-of-attack (AOA) for the sample, shows the increased time-varying nature of the maneuver. As can be seen, close to 25 degrees AOA is distortion as the level of the distortion increases.
achieved for almost 10 seconds. Figure 11(b) shows that for this maneuver, Power Lever Angle (PLA) is Distortion Accommodation held constant. Therefore any transient in the control is due to the maneuver, and not due to an engine power The F100-PW-229 engine is designed with sufficient transient.
stall margin to operate stall-free anywhere in the F-15 flight envelope even under worst case distortion shows the desired engine pressure ratio Figure 11(c) conditions. Thus, distortion accommodation is not (EPR) limit as computed by the SMC and provided as a normally required to maintain stability. However, to request to the control's regulator logic. Figure 11(c) allow flight evaluation of the HISTEC distortion also shows the HISTEC modifier to the EPR request as tolerant control approach, a simulated stability audit computed from the stall margin debit provided by the limit was incorporated into the SMC to force control DES. For a controller without the HISTEC distortion action to downmatch the engine to accommodate for accommodation logic, since there is no engine transient, high levels of inlet distortion. This simulated audit limit the EPR limit request would remain essentially flat represents the stability limit of an advanced fan or throughout the maneuver. As shown in Figure 11(c) , compressor component designed with reduced stall early in the maneuver, while at low AOA, the EPR margin, as would be possible for an engine request remains at this nominal value. However, as incorporating the HISTEC technologies.
AOA (and thus distortion) increases, the HISTEC EPR modifier requests a lower EPR, that is increased Closed-loop operation of the complete HISTEC stability in the presence of distortion. At the end of the approach was demonstrated in flight by having the DES maneuver as AOA returns to near zero, the HISTEC and SMC accommodate the high levels of distortion EPR modifier allows the EPR request to again increase encountered during aggressive aircraft maneuvers. One to its nominal value. Figure 11(d) shows that, in such maneuver is the "Split-S" (Figure 10). During this response to the lowered EPR request at high distortion maneuver, the pilot inverts the aircraft and then pulls conditions, the SMC control laws successfully the stick back to get a sustained high angle-of-attack accommodate the distortion by opening the nozzle area (AOA) while diving towards the ground.
(Aj) to downtrim EPR.
9 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics 2 5 9 0 8 8 A n g le o f A tta c k 8 6 2 0 8 4 PL A 8 2 1 5 8 0 1 0 7 8 7 6 5 7 4 7 2 7 0 0 10 2 0 3 0 4 0 5 0 0 1 0 2 0 3 0 4 0 50 (a) (b) 0 .1 0 .0 8 0 .5 0 .4 0 .0 6 0 .3 0 .0 4 A j Co mma n d 0 .2 0 .0 2 0 .1 -0 .0 2 Co n tr o l EPR L imit -0 .1 -0 .0 4 Dis to r tio n EPR L imit -0 .2 -0 .0 6 -0 .3 -0 .0 8 -0 .4 -0 .1 -0 .5 0 10 2 0 3 0 4 0 5 0 0 1 0 2 0 3 0 4 0 50 (c) (d) Figure 11 - Fan Distortion Accommodation: 27,000ft, Mn=0.6, Split-S Maneuver to 25 degrees Angle of Attack CONCLUSIONS two phases, the first to show distortion estimation, and the second to show distortion accommodation. Post- Under the High Stability Engine Control (HISTEC) flight analysis shows that the HISTEC technologies are Program, a distortion tolerant control system has been able to successfully estimate and accommodate designed, developed, and flight demonstrated on the F- distortion, transiently setting the stall margin 15 ACTIVE aircraft. The control system uses requirement on-line and in real-time. This allows the measurement-based inlet pressure distortion estimation design stall margin requirement to be reduced, which in to enhance engine stability. Flight systems to turn can be traded for significantly increased implement the HISTEC distortion tolerant control for performance and/or decreased weight. Flight flight test were developed and validated through demonstration of the HISTEC technologies has integration testing and engine ground testing and the significantly reduced the risk of transitioning the flight demonstration was accomplished in the summer technology to tactical and commercial engines.
of 1997. The flight demonstration was carried out in 10 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics References 10. Weigl, H.J.; Paduano, J.D.; Frechette, L.G.; 1. Longley, J.P.; and Greitzer, E.M.: "Inlet Epstein, A.H.; Greitzer, E.M.; Bright, M.M.; and Distortion Effects in Aircraft Propulsion System Strazisar, A.J.: “Active Stabilization of Rotating Integration.", Cambridge University, Stall and Surge in a Transonic Single Stage Cambridge (England), 1992. Axial Compressor.” Presented at the 1997 ASME Turbo Expo, Orlando, FL., June 1997.
2. Ralph, J.A.: Advanced Control for Airbreathing Engines, Volume 1, Pratt & Whitney." NASA 11. Society of Automotive Engineers: "Gas Turbine CR 189203, July 1993.
Engine Inlet Flow Distortion Guidelines", Aerospace Recommended Practice (ARP) 1420, 3 . Bansal, Indar: “Advanced Control for 1978.
Airbreathing Engines, Volume 2, General Electric Aircraft Engines.” NASA CR 189204, 12. Southwick, R.D.; Gallops, G.W.; Larkin, L.J.; July 1993.
and Sobanski, K.J.: "High Stability Engine Control (HISTEC) Phase I: Algorithm 4. Bough, R.M.: Advanced Control for Development, Volume I: Final Report and Airbreathing Engines, Volume 3, Allison Gas Appendix A." NASA CR 198399, September Turbine." NASA CR 189205, July 1993 1995.
5. Ouzts, P.J.; Lorenzo, C.F.; and Merrill, W.C.: 13. DeLaat, John C.; Southwick, Robert D.; and "Screening Studies of Advanced Control Gallops, George W.: “High Stability Engine Concepts for Airbreathing Engines." Prepared Control (HISTEC).” Prepared for the 32nd for the 28th Joint Propulsion Conference and Joint Propulsion Conference and Exhibit, July 1- Exhibit, July 6-8, 1992, NASA TM 106042.
3, 1996, NASA TM 107272, AIAA-96-2586.
6. Bright, M.M.; Qammar, H.K.; Weigl, H.J.; and 14. Orme, J.S.; DeLaat, J.C.; Southwick, R.D.; Paduano, J.D.: “Stall Precursor Identification in Gallops, G.W.; and Doane, P.M.: “Flight Test of High-Speed Compressor Stages Using Chaotic the High Stability Engine Control (HISTEC) Time Series Analysis Methods.” Journal of System.” Prepared for the 34th Joint Propulsion Turbomachinery, Vol. 119, July 1997.
Conference and Exhibit, July 13-15, 1998, 7. Eveker, K.M.; Gysling, D.L.; Nett, C.N.; and AIAA-98-3715.
Sharma, O.P.: "Integrated Control of Rotating 15. Southwick, R.D.; Gallops, G.W.; Kerr, L.J.; Stall and Surge in Aeroengines." In Kielb, R.; Welsh, M.; DeLaat, J.C.; and Orme, proceedings: SPIE's International Symposium on J.S.: “High Stability Engine Control (HISTEC) Aerospace/Defense Sensing & Control and Flight Test Results.” Prepared for the 34th Joint Dual-Use Photonics "AeroSense", 4/17-4/21/95.
Propulsion Conference and Exhibit, July 13-15, Proceedings volume 2494.
1998, AIAA-98-3757.
8. Owen, A.K.; Braun, D.C.; Le, D.K.; and Mattern, D.L.: “Results of Forced Response Testing Using Air-Jet Injectors on an Axi- Centrifugal Gas Turbine Engine.” Presented at 33rd Joint Propulsion Conference and Exhibit, July 6-9, 1997, AIAA 97-2770.
9. Berndt, R.G.; Weigl, H.J.; Paduano, J.D.; and Epstein, A.H.: "Experimental Techniques for Actuation, Sensing and Measurement of Rotating Stall Dynamics in High Speed Compressors." In proceedings: SPIE's International Symposium on Aerospace/Defense Sensing & Control and Dual-Use Photonics "AeroSense", 4/17-4/21/95. Proceedings volume 2494.
11 NASA/TM 1998--208482 American Institute of Aeronautics and Astronautics Form Approved REPORT DOCUMENTATION PAGE OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.
2. REPORT DATE 3. REPORT TYPE AND DATES COVERED 1. AGENCY USE ONLY ( Leave blank) Technical Memorandum July 1998 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS The High Stability Engine Control (HISTEC) Program: Flight Demonstration Phase WU–523–53–13–00 6. AUTHOR(S) John C. DeLaat, Robert D. Southwick, George W. Gallops, and John S. Orme 8. PERFORMING ORGANIZATION 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) REPORT NUMBER National Aeronautics and Space Administration Lewis Research Center E–11257 Cleveland, Ohio 44135 – 3191 10. SPONSORING/MONITORING 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) AGENCY REPORT NUMBER National Aeronautics and Space Administration Washington, DC 20546– 0001 NASA TM—1998-208482 AIAA–98–3756 11. SUPPLEMENTARY NOTES Prepared for the 34th Joint Propulsion Conference cosponsored by AIAA, ASME, SAE, and ASEE, Cleveland, Ohio, July 12–15, 1998. John C. DeLaat, NASA Lewis Research Center; Robert D. Southwick and George W. Gallops, United Technologies Corporation, Pratt & Whitney, P.O. Box 109600, West Palm Beach, Florida 33410; John S. Orme, NASA Dryden Flight Research Center, Edwards, California 93523. Responsible person, J.C. DeLaat, organization code 5530, (216) 433–3744.
12b. DISTRIBUTION CODE 12a. DISTRIBUTION/AVAILABILITY STATEMENT Unclassified - Unlimited Subject Category: 07 Distribution: Nonstandard This publication is available from the NASA Center for AeroSpace Information, (301) 621–0390.
13. ABSTRACT (Maximum 200 words) Future aircraft turbine engines, both commercial and military, must be able to accommodate expected increased levels of steady-state and dynamic engine-face distortion. The current approach of incorporating sufficient design stall margin to tolerate these increased levels of distortion would significantly reduce performance. The objective of the High Stability Engine Control (HISTEC) program is to design, develop, and flight-demonstrate an advanced, integrated engine control system that uses measurement-based estimates of distortion to enhance engine stability. The resulting distortion tolerant control reduces the required design stall margin, with a corresponding increase in performance and decrease in fuel burn.
The HISTEC concept has been developed and was successfully flight demonstrated on the F–l 5 ACTIVE aircraft during the summer of 1997. The flight demonstration was planned and carried out in two phases, the first to show distortion estimation, and the second to show distortion accommodation. Post-flight analysis shows that the HISTEC technologies are able to successfully estimate and accommodate distortion, transiently setting the stall margin requirement on-line and in real-time. This allows the design stall margin requirement to be reduced, which in turn can be traded for significantly increased performance and/or decreased weight. Flight demonstration of the HISTEC technologies has significantly reduced the risk of transitioning the technology to tactical and commercial engines.
14. SUBJECT TERMS 15. NUMBER OF PAGES Aircraft engines; Engine control; Flow distortion; Stability augmentation 16. PRICE CODE A03 19. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 17. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF ABSTRACT OF THIS PAGE OF REPORT Unclassified Unclassified Unclassified NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z39-18 298-102