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NASA/TM—1998-208481 AIAA–98–3757
High Stability Engine Control (HISTEC)
Flight Test Results
Robert D. Southwick, George W. Gallops, Laura J. Kerr, Robert P. Kielb, and Mark G. Welsh Pratt & Whitney, West Palm Beach, Florida John C. DeLaat Lewis Research Center, Cleveland, Ohio John S. Orme Dryden Flight Research Center, Edwards, California
July 1998
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NASA/TM—1998-208481 AIAA–98–3757
High Stability Engine Control (HISTEC)
Flight Test Results
Robert D. Southwick, George W. Gallops, Laura J. Kerr, Robert P. Kielb, and Mark G. Welsh Pratt & Whitney, West Palm Beach, Florida John C. DeLaat Lewis Research Center, Cleveland, Ohio 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-98-3757 HIGH STABILITY ENGINE CONTROL (HISTEC) FLIGHT TEST RESULTS R. D. Southwick, G. W. Gallops, L. J. Kerr, R. P. Kielb, and M. G. Welsh Pratt & Whitney West Palm Beach, FL 33410-9600 J. C. DeLaat NASA Lewis Research Center Cleveland, OH J. S. Orme NASA Dryden Flight Research Center Edwards, CA ABSTRACT research has been demonstrated through engine testing on Joint Technology Demonstrator Engines (JTDE) The High Stability Engine Control (HISTEC) Pro- under Department of Defense sponsorship. Studies con- gram, managed and funded by the NASA Lewis ducted under P&W Independent Research & Develop- Research Center, is a cooperative effort between NASA ment (IR&D) showed potential benefit for inflight and Pratt & Whitney (P&W). The program objective is sensing of inlet distortion to enhance engine stability to develop and flight demonstrate an advanced high- management, resulting in further improvements in stability integrated engine control system that uses real- engine performance.
time, measurement-based estimation of inlet pressure distortion to enhance engine stability. Flight testing was The High Stability Engine Control (HISTEC) Pro- gram, managed and funded by NASA Lewis Research performed using the NASA Advanced Controls Tech- Center, is a cooperative effort between NASA and nologies for Integrated Vehicles (ACTIVE) F-15 aircraft at the NASA Dryden Flight Research Center. The flight P&W. Flight testing was accomplished by the NASA Dryden Flight Research Center on a highly modified test configuration, details of the research objectives, and F-15 aircraft provided by the U.S. Air Force. Boeing the flight test matrix to achieve those objectives are pre- sented. Flight test results are discussed that show the St. Louis supported HISTEC integration on the F-15 flight test aircraft. The primary objective of the program design approach can accurately estimate distortion and is to develop and flight demonstrate an advanced high perform real-time control actions for engine accommo- dation. stability integrated engine control system that uses real- time, measurement-based estimation of inlet pressure distortion to enhance engine stability. A secondary INTRODUCTION objective is to enhance the inflight dynamic distortion Future commercial and military aircraft turbine database. The three-phase HISTEC Program was initi- engines must successfully accommodate expected ated in 1993: Phase I — Algorithm Development; Phase increased levels of steady-state and dynamic inlet dis- II — Concept Validation and System Development; tortion. Advanced tactical aircraft are likely to use low 1 2 3 Phase III — Engine Test and Flight Demonstration.
observable inlets and, possibly, thrust vectoring for enhanced aircraft maneuverability. As a result, engines After the distortion estimation algorithms were will probably experience higher levels of distortion than developed in Phase I, system verification using detailed currently encountered in operational aircraft. Also, the simulations was conducted in a software environment.
mixed-compression inlets needed for the High Speed The system modeled included the distortion estimation Civil Transport (HSCT) are likely to encounter distur- system (DES) algorithms, dynamic inlet pressure inputs, bances similar to those seen by tactical aircraft, in addi- ACTIVE F-15 flight control bus, and F100-PW-229 tion to planar pulse, inlet buzz, and high distortion engine with HISTEC stability management control. Test levels at low flight speed and off-design operation. points included planned flight conditions over the HISTEC flight envelope. The model was modified in In conjunction with accommodating increased lev- the latter part of Phase II to include the flight hardware els of distortion, Pratt & Whitney (P&W) has been pur- integrated with a real-time simulation of the engine at suing controls research to help reduce compression P&W, and at Boeing St. Louis.
system design stall margin requirements from current levels. The reduced margin requirements could be Flight test was accomplished on the NASA traded off during engine design for increased engine ACTIVE F-15 aircraft. Prior to flight test, P&W con- performance and decreased weight. Some of this ducted two ground engine tests to further prove out the 1 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 system. This extensive checkout of the HISTEC sys- To improve response to rapid aircraft maneuvers in tem was instrumental in the successful flight test at a timely fashion, the DES incorporates angle-of-attack NASA Dryden during the summer of 1997. ( α ) and angle-of-sideslip ( β ) predictor algorithms sup- plied by Boeing St. Louis. The predictor algorithms use HISTEC APPROACH aircraft flight control inputs to account for the half-sec- ond delay in executing the DES algorithm.
The HISTEC concept quantifies inlet distortion characteristics and their impact on compression system Distortion Estimation System Concept stability through the DES. The DES uses six inputs of In Phases I and IIA of the HISTEC Program, P&W high response static pressure measurements near the fan developed a real-time distortion estimation algorithm face at six locations, five outer diameter (OD) and one following the basic concepts of traditional stability audit inner diameter (ID). The HISTEC implementation methodology as represented in Society of Automotive adjusts the engine operating point based on distortion Engineers Aerospace Recommended Practice (SAE inputs from the DES to maintain sufficient stall margin ARP) 1420 Gas Turbine Engine Inlet Flow Distortion through stability management control (SMC) logic.
Guidelines . This methodology consists of standards for The HISTEC approach to meet the high stability measurement, pattern classification, and computation of engine control requirements is illustrated in Figure 1.
stability debits (Figure 2). This methodology depends Pratt & Whitney developed a practical implementation on a key assumption — the superposition of individual for sensing inlet pressure distortion and a unique algo- circumferential, radial, and planar dynamic distortion rithm concept for determining distortion pattern charac- stability debits.
teristics and intensities based on inlet measurements.
The basic structure of the algorithm is consistent The DES is used in conjunction with advanced SMC with traditional inlet distortion analysis methodology algorithms designed for the F100-PW-229 improved (Figure 3). The instantaneous total pressure pattern digital electronic engine control (IDEEC). High- derived from inlet pressure sensors is categorized response pressure measurements at the engine face are according to three descriptors: circumferential and used as inputs to the DES to classify the inlet distortion radial descriptors similar to ARP 1420, and a planar pattern and debit the stall line through the use of sensi- dynamic descriptor (described in SAE Aerospace tivities derived in the frequency domain. The primary Resource Document [ARD] 50026 A Current Assess- outputs of the DES are trims, representing fan and com- pressor stall line losses, that are sent to the IDEEC as ment of Planar Waves ). The circumferential descriptor inputs to the onboard stability audit.
is obtained by spatial discrete Fourier transform (DFT) of the OD measurements. Only circumferential Modes 1 and 2 are calculated for the ACTIVE F-15 implementa- F100-PW-229 Engine Face Pressure Sensors Actuator Commands Flight Control Data Trim Stability Management Control Distortion Estimation System Commands • Onboard Stability Audit • Distortion Estimates • Stall Margin Control Laws • Engine Sensitivities 96071.cdr Figure 1. HISTEC Control Overview 2 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 Measured Peak Time Variant pattern PL = Local Pressure PL/P ss P = Steady-State Face-Average ss Sensors Pressure (PFAV ) ss Measurement Conversion Inlet Pattern Pattern Classification Spatial/Temporal Components Distortion Sensitivity Stall Pressure Ratio (SPR) Debit Circumferential P( , R, t) = θ Radial
∑
Planar 67406.cdr Figure 2. Traditional Audit Methodology tion. The temporal Fast Fourier Transform (FFT) of the Fourier analysis is an efficient means of implement- DFT circumferential components yields circumferential ing ARP 1420 methodology and lends itself to digital dynamic distortion intensity. The radial and planar dis- signal processing techniques. The impact on fan and tortion intensities and the instantaneous average pres- compressor stall pressure ratio from inlet distortion is sure at the engine inlet plane are similarly calculated, determined by applying frequency-dependent sensitivi- using a discrete sine transform (DST) of the mean of the ties to dynamic distortion components. These are OD and ID measurements. Only radial Modes 1 and 3 defined using a two-dimensional stability model similar are calculated for the ACTIVE F-15 implementation. to those described in References 7 and 8. Note that CYCLE TIMING Inlet 1 msec Logic Pressure 16 msec Logic Measurements 128 msec Logic Average Pressure Measurement Radial Distortion Engine Control IDEEC Conversion (DST) TF Low Pass Circumferential Filtered PT2 High Pass Filtered Distortion PT2 (DFT) Airflow Fan- Circumferential Radial Planar Pressure Distortion (FFT) Distortion (FFT) Distortion(FFT) Ratio Low-Rotor Speed Fan High- Fan Fan Fan Fan Fan Sensitivity Rotor Sensitivity Sensitivity Transfer Transfer Transfer Speed Flight Alpha/Beta Compressor Compressor Control Compressor Predictor Sensitivity Sensitivity Sensitivity Fan Pressure Ratio Trim Dynamic Maneuver Compressor Compensation Pressure Ratio Trim 96028.cdr Figure 3. DES Algorithm Overview 3 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 compressor inlet distortion is not directly measured by IDEEC. These additional data are calculated by the the DES. It is determined by applying a fan distortion IDEEC.
transfer function to the inlet distortion components.
Because the F100-PW-229 engine is designed with Because of computational delays and the limited enough stall margin to accommodate the worst stability response of the engine and control with this particular threats anywhere in the F-15 operational flight envelope configuration, dynamic compensation must be applied over the life of the engine, a means was devised for to fan and compressor limit trims to accommodate rapid HISTEC to demonstrate the actions of the SMC algo- aircraft maneuvers. Transient lead functions are based rithms. The objective was to functionally demonstrate on predicted (approximately 0.5 second lead time) val- the effectiveness of the algorithms in an aggressive but ues of α and β . safe manner, and with a production-like implementa- tion. This was accomplished by incorporating a simu- Stability Management Control lated stability audit limit that allowed HISTEC to operate away from the actual engine stall line, yet per- The HISTEC SMC algorithms were successfully mitted variable engine operating margins. This simu- implemented into a production F100-PW-229 engine lated audit limit represents the stability limit of a fan or control that met requirements for integration with the compressor component with reduced design stall mar- ACTIVE F-15 aircraft. The SMC algorithms consisted gin. The flexibility of the digital engine control allowed of an onboard real-time stability audit for the fan and the simulated stability limit, referred to as the technol- compressor that quantifies all destabilizing effects on ogy bias , to be readily changed between flights as stall margin, including the effects of inlet distortion desired. All compression system destabilizing influ- determined by the DES. The SMC algorithms dynami- ences, including the inlet distortion effects from the cally adjust the fan and compressor operating lines DES, are debited from the simulated stability limit to (oplines) in response to changes in instantaneous stall arrive at the stall margin remaining used by the SMC.
margin remaining from the audit.
Real-time stability audits implemented for HISTEC FLIGHT TEST PROGRAM are based on stability audit methodology used for all P&W commercial and military engines. The methodol- The flight test program was designed to methodi- ogy considers all destabilizing influences for the com- cally evaluate the HISTEC approach to high stability pression system including random variations. The engine control and to provide a significant amount of HISTEC stability audit algorithms provide the same high-quality inflight dynamic inlet distortion data.
type of stability evaluation in real time as is traditionally Together, P&W, NASA Lewis, and NASA Dryden performed off-line. Some inputs to the off-line stability defined a comprehensive test matrix that included 106 audit include additional measurements from engine flight test points. Figure 4 shows the HISTEC flight development instrumentation not available to the envelope and flight conditions, which included steady Figure 4. HISTEC Flight Envelope 4 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 flight and aggressive maneuvers up to the aircraft α , β , and g limits. NASA and P&W established success crite- ria for HISTEC DES accuracy at specific flight condi- tions. The HISTEC goal was to provide a real-time estimate of stall margin loss (SML) due to inlet distor- tion to within ±2.5 percent of the SML calculated off- line using extensive inlet research instrumentation and ARP 1420 methodology.
The HISTEC flight test matrix was accomplished in two parts. Part 1 of the flight test included an exten- sive matrix of test points to obtain the distortion data- base and determine the ability of the DES to accurately estimate SML due to inlet distortion. Although the SMC Figure 5. ACTIVE Testbed laws within the engine control were executed for evalu- ation purposes, the control did not send trim data to the HISTEC-specific instrumentation. The HISTEC DES engine for stability accommodation during Part 1. This receives six high response static pressure inputs: five is referred to as open-loop operation. At the conclusion outer diameter (OD) pressure measurements and the of Part 1, flight test data analysis was performed to (electrical) average of five inner diameter (ID) pressure determine the need to fine-tune the HISTEC algorithms measurements. Static pressure taps are located between prior to proceeding with Part 2 of flight test. Part 2 of struts on the OD and ID inlet case shrouds (Figure 6).
the HISTEC flight test program focused on closed-loop To evaluate the DES and augment the distortion operation where the control modified engine operation database, a full complement of research instrumentation to maintain engine stability based on inputs from the (for reference only) was installed in the engine inlet DES.
case. An array of 35 high-response total pressure sen- Flight Test Configuration sors was installed in the leading edges (LEs) of the inlet struts. The strut LE pressure sensors are located on 7 The HISTEC flight tests were conducted at the inlet case struts, 5 sensors per strut, distributed radially NASA Dryden Flight Research Center at Edwards Air on each strut by equal flowpath area. A total tempera- Force Base, California on the NASA ACTIVE F-15 air- ture sensor, used for temperature compensation, was craft (Figure 5). Although the aircraft was equipped installed approximately mid-span on each instrumented with thrust vectoring nozzles, they were not used during inlet strut LE. Nine additional OD pressure sensors (five HISTEC testing due to data bus constraints in accom- adjacent to the DES sensors for data recording) were modating the HISTEC control hardware.
added for a more complete circumferential mapping of The HISTEC instrumented inlet case is a modified inlet profiles.
production F100-PW-229 inlet case that incorporates Figure 6. HISTEC Instrumented Inlet Case 5 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 The DES algorithms were incorporated in a high- speed processor that calculated real-time distortion char- acteristics and intensities from the inlet pressure mea- surements. For HISTEC, the DES computer (Figure 7) was aircraft-mounted and communicated with the engine control through the aircraft flight control 1553 data communications bus. To accommodate the existing bus architecture, the DES was installed in place of Channel B of the Vehicle Management System Com- puter (VMSC). This required additional software in the DES to emulate the VMSC Channel B to prevent wrap- around failures with the aircraft flight control. Modifica- tions to the bus architecture are shown in Figure 8.
Figure 7. DES Computer Figure 8. HISTEC Bus FLIGHT TEST RESULTS the largest drift, least drift and the transducer that fell in the middle. In the table, transducers with a PTIGV The HISTEC flight test instrumentation performed header were the high-response total pressure type, exceptionally well during the flight test. All high- located in the fan inlet guide vane strut while PSW20 response pressure transducers were checked for drift was one of the high-response wall static transducers.
during testing. This was accomplished through a pre- flight engine-off data point taken at the beginning of Each day, there was also a pressure calibration data each day of testing. This information was then com- point taken at 20,000 ft, 0.6 Mach (20K/0.6), straight pared to an independent atmospheric pressure measure- and level at full power. All total pressure transducers ment, with the difference (psi) applied to the transducer were repeatable to within 2.5 percent while all static for the remainder of the day. The difference, known as pressure transducers were repeatable to within 5 per- the ambient offset, was plotted versus test day and fit cent.
with a linear least squares curve fit. The slope of the lin- ear fit is a measure of transducer drift. The slope was Stall margin loss from HISTEC was compared to always small compared to the standard error of the data that calculated using ARP 1420 methodology for all indicating that system uncertainty masked any trans- specified audit points (Figure 9). ARP 1420 is the cur- ducer drift that may have occurred. Table 1 shows the rent industry standard and is used as the baseline for slope and standard error (psi) for the transducers with comparative purposes. There is no direct comparison 6 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 Figure 11. Comparison of ACTIVE F-15 Inlet Total Pressure Patterns Using Research Instrumentation and DES Pressure Measurements 8 NASA/TM 1998--208481 American Institute of Aeronautics and Astronautics AIAA-98-3757 Figure 12. HISTEC Operation for Angle-of-Attack Sweep REFERENCES 5. Society of Automotive Engineers. Gas Turbine Engine Inlet Flow Distortion Guidelines , Aero- 1. Southwick, Robert D., George W. Gallops, Louis J.
space Recommended Practice (ARP) 1420, 1978.
Larkin, and Kurt J. Sobanski. High Stability Engine 6. Society of Automotive Engineers. A Current Control (HISTEC) Phase I: Algorithm Develop- Assessment of Planar Waves . Aerospace Resource ment, Volume I: Final Report and Appendix A , Document (ARD) 50026, 1994.
NASA CR 198399, September 1995.
7. Gong, Y., C. S. Tan, and K. A. Gordon. A Computa- 2. Orme, J. S., J. C. DeLaat, R. D. Southwick, G. W.
tional Model for Short Wavelength Stall Inception Gallops, and P. M Doane. Development and Testing and Development in Multi-Stage Compressors.
of a High Stability Engine Control (HISTEC) Sys- Paper 98-GT-476, presented at the International Gas tem. Paper AIAA-98-3715, presented at the 34th Turbine and Aeroengine Congress and Exhibition, AIAA/ASME/SAE/ASEE Joint Propulsion Confer- Stockholm, June 1998.
ence and Exhibit, Cleveland, July 1998.
8. Longley, J. P., H. W. Shin, R. E. Plumley, P. D.
3. DeLaat, J. C., R. D. Southwick, G. W. Gallops, and Silkowski, I. J. Day, E. M. Greitzer, C. S. Tan, and J. S. Orme. The High Stability Engine Control D. C. Wisler. Effects of Rotating Inlet Distortion on (HISTEC) Program: Flight Demonstration Phase.
Multistage Compressor Stability. ASME Journal of Paper AIAA-98-3756, presented at the 34th AIAA/ Turbomachinery 118, pp. 181-188, 1996.
ASME/SAE/ASEE Joint Propulsion Conference 9. DeLaat, John C., Robert D. Southwick, and and Exhibit, Cleveland, July 1998.
George W. Gallops. High Stability Engine Control 4. U. S. Patent 074431 Gas Turbine Engine Control (HISTEC). Paper AIAA-96-2586, presented at the Based on Inlet Pressure Distortion. Issued Septem- 32nd AIAA/ASME/SAE/ASEE Joint Propulsion ber 1995, assigned to United Technologies Corpo- Conference and Exhibit, Lake Buena Vista, July ration. 1996.
9 NASA/TM 1998--208481 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 High Stability Engine Control (HISTEC) Flight Test Results WU–523–53–13–00 6. AUTHOR(S) Robert D. Southwick, George W. Gallops, Laura J. Kerr, Robert P. Kielb, Mark G. Welsh, John C. DeLaat, 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–11255 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—1998-208481 AIAA–98–3757 11. SUPPLEMENTARY NOTES Prepared for the 34th Joint Propulsion Conference cosponsored by AIAA, ASME, SAE, and ASEE, Cleveland, Ohio, July 12–15, 1998. R.D. Southwick, G.W. Gallops, L.J. Kerr, R.P. Kielb, and M.G. Welsh, Pratt & Whitney, West Palm Beach, Florida 33410–9600; J.C. DeLaat, NASA Lewis Research Center; J.S. Orme, NASA Dryden Flight Research Center, Edwards, California. 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) The High Stability Engine Control (HISTEC) Program, managed and funded by the NASA Lewis Research Center, is a cooperative effort between NASA and Pratt & Whitney (P&W). The program objective is to develop and flight demon- strate an advanced high stability integrated engine control system that uses real-time, measurement-based estimation of inlet pressure distortion to enhance engine stability. Flight testing was performed using the NASA Advanced Controls Technologies for Integrated Vehicles (ACTIVE) F–15 aircraft at the NASA Dryden Flight Research Center. The flight test configuration, details of the research objectives, and the flight test matrix to achieve those objectives are presented. Flight test results are discussed that show the design approach can accurately estimate distortion and perform real-time control actions for engine accommodation.
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