Controls of Aero Gas Turbine Engines

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Controls of Aero Gas Turbine Engines

  1. 1. National Level Workshop on Recent Trends in Aerospace Propulsion Controls of Aero Gas Turbine Engines 16 February 2012 Rohan M Ganapathy Undergraduate, Dept of Aeronautical Engineering, Hindusthan College of Engineering and Technology, Coimbatore
  2. 2. Lecture flow • Controls • Requirements • Mechanical • FADEC • Integrated propulsion • Continued challenges srb-hcet-001
  3. 3. Gas Turbine Components • The basic gas turbine engine comprises of a number of main components • Intake casing • Compressor • Combustion chamber • Turbine • Jet pipe • Exhaust nozzle. • srb-hcet-002
  4. 4. Typical Gas turbine schematic
  5. 5. Fuel Supply & Engine Thrust • The fuel supply input into the engine in conjunction with the starting and ignition systems sets the gas turbine cycle into operation resulting in  Rotational speeds of engine with consequent production of thrust.  In turn, this thrust helps in forward movement of the aircraft when the engine is installed into it.
  6. 6. Control Variable : Fuel Flow • Control of fuel flow into main combustion chamber can be done in response to a number of parameters • Engine rotational speed bears a direct relationship with the turbine entry temperature and this is one of the parameters used to control fuel flow to the engine
  7. 7. Power Lever Angle – Rotational Speed
  8. 8. PLA-Rotational Speed block diagram • Outer and Inner loops • PLA demand creates N demand • N demand creates valve position demand • Valve position causes fuel flow input • Engine rotational speed results as output • Two feedback loops based on valve position and engine rotational speed sensor fed into loop
  9. 9. Requirements of Fuel Control • The control of the gas turbine rotational speed is achieved through modulation of the fuel flow by the pilot through the power lever angle (PLA) operation. • For the transient condition such as acceleration and deceleration, this quantum of fuel flow would be different.
  10. 10. Requirements of Fuel Control- [contd] • Further the fuel flow is to be made a function of altitude and forward speed depending upon the flight envelope prescribed for the engine and its corresponding aircraft installation. • Therefore, there is a basic need to control this variable called the fuel flow and this needs to be done automatically in order to minimize pilot work load.
  11. 11. Phases of engine operation • Starting • Ground idling • Acceleration , Deceleration • Slams , Chops • Shutdown • Cruising • Flight idling • Max dry , Afterburner/Reheat
  12. 12. Typical Fuel Flow Schedules
  13. 13. Typical Governor Characteristics
  14. 14. GT Control Variables • To meet increasing demands for obtaining precise performance of engine the number of control variables has increased from simple fuel control to multi controls. • Variabilility in inlet guide vanes, exhaust nozzle, stator vanes, bypass bleed, reheat fuel flow, etc., are typical control variables that have evolved over the decades.
  15. 15. Growth in Control Variables
  16. 16. Control Variables
  17. 17. Simplified fuel systems for turbo-propeller and turbo-jet engines – RR Manual
  18. 18. Mechanical Control System Configuration • Mechanical elements added to cater for above control variables • 3-Dimensional cams, spool sleeve combinations, air potentiometer networks, servo devices, moving pivots and beam governors, etc all added to make the fuel control system as a very complicated mechanical computer
  19. 19. Typical 2 spool requirements • Complete engine control considering all the control variables • Translation of fuel flow, biased w.r.t. engine intake temperature and engine intake temperature so as to control LP spool / HP spool speed • All speed governing of spool speeds biased w.r.t. engine intake temperature
  20. 20. Typical 2 spool requirements (contd) • Rising idle speed characteristics to prevent flameout • Prescription of Ndot control • Scheduling Exhaust nozzle area, Afterburner fuel flow, Inlet Guide Vanes and Stator vanes as a functions of PLA • Ensuring engine safety by limiting values of Spool speeds, TET, JPT, Pressure Ratio, etc.
  21. 21. Typical 2 spool requirements (contd) • Ensuring performance of engine control systems under extremes of environments in relation to Temperature, Vibration, EMI, Nuclear exposure, Dust, Fire, etc • Ensuring data transfer between engine/airframe and airframe/engine • Ensuring high reliability levels of system so that MTBF is quite high • Ensuring system architecture is fault tolerant
  22. 22. Typical Flight Envelope
  23. 23. Typical Limiter
  24. 24. Evolution of [FADEC] system • Basic hydromechanical elements/devices enjoyed high reliability • Initial Trimming controls through electrical/electronic means deployed in the nature of limited authority trim on the basic system • Early engines like Spey, Pegasus, RB211 • These trimming systems offered redundancy in the sense that adequate safety was assured even after failures of the main control function
  25. 25. FADEC System (contd) • With suitable packaging of electronic components/circuits supervisory sort of electronic control system was configured • This system improved performance when it was operated and its failure would not hazard engine/airframe mission • The disadvantage was that the complicated heavy hydromechanical system had to be carried and the supervisory authority system could not achieve the full performance potential
  26. 26. FADEC System (contd) • The Analog computer and controller [ used in the Olympus 593 of the Concorde] had its attendant problems with environment effects and temperature changes • The digital computer outpaced the analog computer in terms of capability to store huge amounts of data, functional insensitiveness to environmental effects and temperature
  27. 27. RHMPDV IHPP DECU FSP MECU RHFCU Compressor VG Main Burners Reheat burners Nozzle actuators Fuel in Manual Fuel Control Linkage Engine & System Feed back PLA Demonstrator Engine with Digital Controller
  28. 28. FADEC System (contd) • The digital computer provided the basic ability and flexibility for quick changes especially during development through the embedded software changes • With advances in electronic components/circuits and their improvement in reliability coupled with packaging heralded the beginning of the full authority digital engine control[ FADEC]
  29. 29. FADEC System (contd) • With need to build in defined control laws, redundancy management, mission requirements, precise engine operation with optimum fuel burn, health monitoring and diagnostics, the FADEC system is a fairly standard system in gas turbine engines, Civil and Military [ Pegasus, M88, Trent 1000,etc] • A fully integrated flight propulsion control system is available in many aircraft/engine flight systems today [ LCA]
  30. 30. CVG CONTROL MAIN FUEL CONTROL REHEAT FUEL CONTROL NOZZLE CONTROL DECU LANE 1 DECU LANE 2 ALTERNATORIGNITION BOX ENGINE & FEED BACK SENSORS ENGINE & FEED BACK SENSORS 28 V AIRCARFT BATTERYMISSION COMPUTER 1553 B BUS 1553 B BUS PLA EFI COCKPIT CONTROLS ENGINE AIRFRAME Demonstrator Engine Twin Lane Digital Controller Block Diagram
  31. 31.  Modeling  System Identification  Linear design  Non Linear – Non Real Time Simulation  Hardware in the Loop Simulation  Engine Test Control System Evolution
  32. 32. ENGINE / SYSTEM SIMULATION SYSTEM IDENTIFICATION ARX / IT / BJ / CO Input Output ENGINE TRANSFER FUNCTION (Estimated) ENGINE / SYSTEM TEST DATA SYSTEM IDENTIFICATION ARX / IT / BJ / CO Input Output ENGINE TRANSFER FUNCTION (Evaluated) Validation R(s) C(s) = G(s) System Identification
  33. 33.  Classical design technique.  Piecewise linearisation at various speeds (80%, 85%, 90%, 94% & 98% NH) and flight conditions: T1 K P1 psia Alt Km MNo Condition 240 3.715 11 0.42 ISA+15 288 14.700 0 0.00 ISA 315 12.676 6 0.98 ISA+15 350 13.952 11 1.59 ISA+15 380 28.302 3 1.30 ISA+15 Linear Design
  34. 34.  Each of the following control loop is designed to have desired response: • Metering Valve position loop • NHdot acceleration • NL speed control • VG control • Nozzle control • Reheat fuel control • Backup fuel override schedule control  In addition following control loops are designed at appropriate conditions: • NH at idle • Limiter control loops – NH , P3, P3/P1, T6 Linear Design
  35. 35. Response of NL for Step input in PLA 0 5 10 15 20 25 30 0 0.2 0.4 0.6 0.8 1 1.2 Response of NL for Step input in PLA Time (sec) NL
  36. 36. 0 5 10 15 20 25 30 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Time (sec) NH 0 5 10 15 20 25 30 -1 0 1 2 3 4 5 6 7 Time (sec) P3 0 5 10 15 20 25 30 -2 0 2 4 6 8 10 12 14 16 Time (sec) T4 0 5 10 15 20 25 30 -2 0 2 4 6 8 10 12 Time (sec) T6 Response of Engine Parameters for Step Input in PLA T4 NH T6 P3
  37. 37. • All the models of the Engine and control system subsystems • Controller gains and lead compensation parameters obtained in the Linear design at various speeds and flight conditions are scheduled. • Integrated simulation study carried out for: 1. Small inputs & steady state performance study. 2. Large input slam/chop performance study 3. Study the efficiency of control logics incorporated 4. Assurance of controller stability and transient capability at all operating points Non Linear – Non Real time Integrated Simulation
  38. 38. Engine Speed response for PLA slam (Idle to Max dry)
  39. 39. Test Description Standard Temperature testing – Hot MIL-E-5007 E Temperature testing – Cold MIL-E-5007 E Room temperature endurance MIL-E-5007 E Pressure testing fatigue proof and ultimate pressure test ACJ-E-640 & JAR-E-640 Low lubricity fuel test MIL-E-5007 E Humidity MIL-STD-810D Fungus MIL-STD-810D Salt mist MIL-STD-810D Sand and dust MIL-STD-810D Contaminated fuel MIL-E-5007 E Icing MIL-STD-810D Explosion proof / explosive atmosphere MIL-STD-810D Sustained acceleration test MIL-STD-810D Functional shock MIL-STD-810D Vibration test MIL-STD-810D Fire test MIL-E-5007 E Simulated operational test MIL-E-5007 E QUALIFICATION TESTS
  40. 40. Intelligent Gas Turbine Engines • Intelligent Propulsion Systems lay greater emphasis on aircraft safety, enhanced performance and affordability, need to reduce the environmental impact of aircrafts • This calls for the increased efficiencies of components through active control, advanced diagnostics and prognostics integrated with intelligent engine control and distributed control with smart sensors and actuators
  41. 41. Intelligent Gas Turbine Engines[contd] • Actively Controlled Components will mitigate challenges related inlet flow distortion and separation and noise; compressor aerodynamic losses and surge and stall; combustion instabilities, uneven temperature distribution, and pollution emission; turbine aerodynamic losses and leakages, high cycle fatigue, and limited airfoil durability, jet noise, emission and signature
  42. 42. Intelligent Gas Turbine Engines[contd] • Intelligent Control and Health Monitoring with advanced model-based control architecture overcomes the limitations of state-of-the-art engine control and provides the potential of virtual sensors • “Tracking filters” are used to adapt the control parameters to actual conditions and to individual engines. Currently, health monitoring units are stand-alone monitoring units. Integration of both control and monitoring functions is possible • Adaptive models open up the possibility of adapting the control logic to maintain desired performance in the presence of engine degradation
  43. 43. Intelligent Gas Turbine Engines[contd] • Distributed Engine Control using high temperature electronics and open systems communications will reverse the growing trend of increasing ratio of control system weight to engine weight and also will be a major factor in • Challenges for implementation include need for high temperature electronics (located on or close to the sensing element), development of simple, robust communications (simplifying and reducing the wiring harness), and power supply for the on-board distributed electronics
  44. 44. Intelligent Gas Turbine Engines[contd] • Sensors mainly require higher operational temperatures. Some progress can be made by changing the packaging and/or design of the current sensors, but sensor for locations close to the engine combustion chamber or afterburner do not exist. There is also a need for smart sensors, which would enable future distributed control architecture. • Actuator requirements are addressed for three common actuation functions, namely: Micro flow manipulation; Large-scale flow switching; and Mechanical manipulation.
  45. 45. I G T Engines-Key Enabling Technologies • Increased efficiencies of components through active control • Increased overall engine gas-path performance and extended “on wing” life of the engine through • Model-based control and health monitoring • Reduced weight ratio of control system to engine through distributed control with smart sensors.
  46. 46. I G T Engines-Key Enabling Technologies[contd] • Active Component Control that can help to meet future engine requirements by an active improvement of the component characteristics. • The concept is based on an intelligent control logic, which senses actual operating conditions and reacts with adequate actuator action.
  47. 47. I G T Engines-Key Enabling Technologies[contd] • Active control addresses the design constraints imposed by unsteady phenomena like • Inlet distortion, compressor surge, combustion instability, flow separations, vibration and noise, which only occur during exceptional operating conditions.
  48. 48. I G T Engines-Key Enabling Technologies[contd] • Inlet: Active Inlet Control, Active Noise Suppression, Active Noise Cancellation • Compressor: Active Surge Control, Active Flow Control, Active Clearance Control, Active Vibration Control • Combustor: Active Combustion, Instability Control • Turbine: Active Clearance Control, Cooling Air Control, Active Flow Control
  49. 49. I G T Engines-Key Enabling Technologies[contd] • Nozzle: Active Noise Control, Adaptive Nozzles, • Thrust Vectoring, Active Core Exhaust Control, • Afterburner Stability Control • Significant efforts in research and development remain to implement these
  50. 50. I G T Engines-Key Enabling Technologies[contd] • Intelligent Control and Health Monitoring concepts using advanced model-based Multi Input Multi Output (MIMO) control architecture, where all available control actuators are manipulated in a coordinated manner. • Can provide outputs for which sensors are not available, i.e. virtual sensors.
  51. 51. I G T Engines-Key Enabling Technologies[contd] • Adaptive models adapt the control logic to maintain desired performance in the presence of engine degradation or accommodating any faults in a way such as to maintain optimal performance • The Model Predictive Control (MPC) is an emerging approach, which solves a constrained optimization problem online to obtain the “best” control action, based on a tracked engine model, constraints, and the desired optimization objective.
  52. 52. I G T Engines-Key Enabling Technologies[contd] • The implementation of distributed engine control is not without significant challenges, including needs for high temperature electronics, development of simple, robust communications, and power supply for the on-board electronics • A need for on-board electronics located on or close to the sensing element or the actuator, such that network communications can be enabled and the wiring harness required for communications between sensors and actuators and the engine controller can be substantially reduced.
  53. 53. I G T Engines-Key Enabling Technologies[contd] • The standard GTE Gas Path Sensors are designed and packaged according to the specifications driven by the certification reqmts. • Written by the GTE manufacturers following guidelines of MIL-STD 810F for tailoring sensors’s environmental design and test limits to the conditions that the specific sensor will experience throughout its service life • Present sensors with integrated electronics are limited to environment conditions within –65 C to +115 C.
  54. 54. I G T Engines-Key Enabling Technologies[contd] • Micro-Electro Mechanical Systems (MEMS) is a good candidate to address the need for high- temperature operation and for new types of sensors, including smart sensor capabilities. Silicon-on-Insulator (SOI) provides some advantages (with potential operational temperatures of 300ºC); the semiconductor SiC (up to 500 C) and the ceramic material SiCN (up to 1700 C) are explored for even higher temperatures.
  55. 55. I G T Engines-Key Enabling Technologies[contd] • Generic actuator requirements for three common actuation functions : • Flow manipulation (of the boundary layer by either mechanical effects or aerodynamic means with blowing or sucking air); • Large scale flow switching (valves with applications to stall/surge control, bleed flows, cooling flows,other); and • Mechanical manipulation (intakes, variable guide vanes and nozzles).
  56. 56. I G T Engines-Key Enabling Technologies[contd] • Emerging technologies for actuation systems would include: • Electroactive materials, including piezoelectric ceramics and Electro Active Polymers (EAPs) • Shape memory materials • Magnetic strained materials (providing magnetostrictive effects) • Magnetic Shape Memory (MSM) or Ferromagnetic Shape Memory (FSM) materials and Microsystems, micromachines and MEMS
  57. 57. THANK YOU

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