CFM REGULATION THE POWER OF FLIGHT

Transcription

1 CFM REGULATION 1

2 CFM56-3 2

3 Speed Governing System Fuel Limiting System VBV VSV N1 Vs P Idling System HPTCCV N1 Vs Z N1 Vs T Main Tasks Additional Tasks Corrections MEC PMC CFM 56-3 ENGINE OPERATIONAL CONTROL 3

4 ENGINE OPERATIONAL CONTROL TheCFM56-3 engine control system consists of both: HYDRO MECHANICAL UNIT ELECTRONIC UNIT 4

5 HYDRO MECHANICAL UNIT MEC Main Engine Control Automatically schedules: WF ( Fuel Flow ) N2 VBV ( Variable Bleed Valve ) VSV ( Variable Stator Vane ) HPTCCV ( High Pressure Turbine Clearance Control Valve ) 5

6 ELECTRONIC UNIT PMC Power Management Control Provide FAN scheduling N1 6

7 CONTROL SYSTEM SCHEMATIC 7

8 CONTROL SYSTEM SCHEMATIC (Cont d) N1 Fan Speed N2 Core Speed WF Fuel Flow TMC Torque Motor Current PS12 Fan Inlet Static Air Pressure PS3 Compressor Discharge Pressure CBP Compressor Bleed Pressure T12 Fan Inlet Total Air Temperature T2.5 HPC Inlet Air Temperature T2 Fan Inlet Temperature TC1 Turbine Clearance Control 5Th Stage TC2 Turbine Clearance Control 9Th Stage TC3 Turbine Clearance Control Timer Signal 8

9 ENGINE STATIONS 25 HP Compressor Inlet 12 Secondary Flow Inlet 3 HP Compressor Discharge 2 Primary Flow Inlet Stage 2 LPT Inlet 9

10 MEC OIL/ FUEL HEAT EXCHANGER MEC FUEL PUMP 10

11 MEC OPERATION MEC is an Hydro mechanical device using fuel pressure to work. A device monitors fuel pressure at low flow conditions for MEC servo operation. FUEL PUMP BYPASS LP STAGE VALVE MEC Fuel Metering System FUEL FUEL FUEL PUMP HP STAGE METERING VALVE SHUT-OFF VALVE PRESSURISING VALVE 11

12 MEC PURPOSE TheMEC s job is divided in 2 tasks: MAIN TASKS: Speed governing system Fuel limiting system Idling system ADDITIONAL TASKS: Control functions to optimise engine performance VBV VSV HPTCCV 12

13 SPEED GOVERNING SYSTEM MEC SPEED GOVERNING SYSTEM N2 demand PS12 FMV Wf T2 N2 actual Fuel 13

14 FUEL LIMITING SYSTEM During transient operation, the speed governing system could change the fuel flow beyond the safe limits. The purpose of the fuel limiting system is to define and impose correct engine fuel flow limits during rapid transients: ACCELERATIONS DECELERATIONS STARTS 14

15 FUEL LIMITING SYSTEM (Cont d) SPEED GOVERNING SYSTEM MEC FUEL LIMITING SYSTEM T2.5 PS3 N2 CBP N2 demand PS12 + / - FMV Wf T2 N2 actual Fuel 15

16 IDLING SYSTEM HIGH IDLE: Used only when anti-icing is selected or if a flying aircraft has flaps configuration > 15. It is optimised to provide rapid recovery of takeoff thrust if required. LOW IDLE: Ground idle: Flight idle: Provide adequate taxi thrust while minimising noise, fuel consumption and braking effort Scheduled to minimise fuel consumption. 16

17 IDLING SYSTEM (Cont d) DESIRED SPEED SETTING MEC AIRCRAFT CONFIGURATION PLA IDLE Yes / NO FUEL LIMITING SYSTEM T2.5 PS3 N2 CBP N2 demand PS12 +/ - FMV Wf T2 N2 actual Fuel 17

18 MEC ADDITIONAL TASKS VBV SYSTEM VBV system positions 12 valves by hydraulic pressure acting upon a fuel gear motor. The fuel pressure is scheduled by the MEC. VBV feedback cable is positioned to provide the MEC with a current VBV position to compare with the desired position. 18

19 MEC ADDITIONAL TASKS (Cont d) VBV SYSTEM (Cont d) 19

20 MEC ADDITIONAL TASKS (Cont d) VBV PURPOSE As the Compressor is optimised for ratings close to maximum power engine operation has to be protected during deceleration or at low speed: Without VBV installed: At Deceleration or Low speed Booster Outlet Airflow much more than Booster Pressure Ratio LPC stall margin reduced To re-establish a suitable mass flow VBV are installed on the contour of the primary airflow stream between booster and HPC to download booster exit. With VBV installed: At Deceleration or Low speed VBV fully open Booster Pressure Ratio but same Booster Outlet Airflow Plenty of LPC stall margin 20

21 MEC ADDITIONAL TASKS (Cont d) VBV PURPOSE (Cont d) B O O S T E R P R E S S U R E R A T I O TYPICAL LPC FLOW CHART STALL REGION IDLE 4 BOOSTER OUTLET AIRFLOW Efficiency MCT LOW EFFICIENCY REGION Maxi Efficiency Design Point ISO N1 Line VBV Operation Acceleration Schedule If VBV not closed Deceleration Schedule If VBV not open Operating Line Low speed or Deceleration VBV OPEN High speed or acceleration VBV CLOSED 21

22 MEC ADDITIONAL TASKS (Cont d) VSV SYSTEM VSV system changes the angle of the HP Compressor IGV and N 1,2 and 3 stator stages according to the MEC computation. MEC directs a resulting high pressure fuel flow to the dual VSV actuators. The actuators mechanically position the VSV. A feedback cable provides the VSV position to the MEC. A comparison is performed between schedule requirements and actual VSV position to determine the need to continue actuator control or not. 22

23 MEC ADDITIONAL TASKS (Cont d) VSV SYSTEM (Cont d) 23

24 MEC ADDITIONAL TASKS (Cont d) VSV SYSTEM (Cont d) 24

25 MEC ADDITIONAL TASKS (Cont d) VSV PURPOSE The Compressor is optimised for ratings close to maximum power. Engine operation has to be protected during deceleration or at low speed. VSV system position HPC Stator Vanes to the appropriate angle of incidence. VSV (3) - VSV optimise HPC efficiency. - VSV improve stall margin for transient engine operations. IGV ROTOR VSV 1 IGV (Inlet Guide Vane) ROTOR STAGE Etc 25

26 MEC ADDITIONAL TASKS (Cont (Cont d) C O M P R E S S O R P R E S S U R E R A T I O VSV PURPOSE (Cont d) TYPICAL HPC FLOW CHART STALL REGION IDLE 4 COMPRESSOR OUTLET AIRFLOW MCT LOW EFFICIENCY REGION Efficiency Maxi Efficiency Design Point ISO N1 Line VSV Operation Acceleration Schedule If VSV not open Deceleration Schedule 4 Operating Line Low speed or Deceleration VSV CLOSED High speed or acceleration VSV OPEN 26

27 CLEARANCE CONTROL Operating tip clearance in the core engine are of primary importance. They determine: Steady state efficiencies: Fuel consumption Transient engine performance: Peak gas temperature Compressor stall margin 27

28 CLEARANCE CONTROL (Cont d) Clearance Control in the CFM56 engine is accomplished by a combination of 3 mechanical designs: Passive control: Using materials in the compressor aft case with low coefficient of thermal expansion. Forced cooling: Using Low Pressure Booster discharge cooling air for compressor and turbine. Automatic control: HPTCC VALVE and HPTCC TIMER are used to control the tip clearance between HPT blades and stationary tip shrouds. 28

29 HPTCCV ACTUATION Automatic Control is using Bleed Air from 5 Th and 9 Th stages of HPC to either cool or heat the HPT shroud. N2 > 95 % YES / NO AIR FROM 5 Th STAGE HPTCC MEC HPTCC TIMER VALVE HPT SHROUD AIRCRAFT ON THE GROUND YES / NO AIR FROM 9 Th STAGE 29

30 HPTCCV ACTUATION (Cont d) During flight: - Air selection is determined by fuel pressure signals sent from the MEC to the TIMER. - The TIMER sends fuel pressure signals without change to actuate the HPTCC VALVE. - The selected bleed air is ducted to a manifold surrounding the HPT SHROUD. 30

31 HPTCCV ACTUATION (Cont d) During takeoff: - The TIMER overrides the normal MEC operation of the valve. - It is sequencing a transient air schedule over a specified time period to maintain a more nearly constant HPT blade tip clearance during the period of HPT Rotor/Stator thermal stabilisation. - This maintain Turbine efficiency and decreases transient EGT overshoot. - A lockout valve permits the TIMER to actuate only once per engine cycle. ( i.e. from start to shut down) 31

32 HPTCCV ACTUATION (Cont d) 32

33 HPTCCV ACTUATION (Cont d) The TIMER SEQUENCE: - Starting Reference Point is when the engine reach 95 % N2. - Then: 0 to 8 s No air 8 to 152 s 5 Th stage air 152 to 182 s 5 Th + 9 Th stage air 33

34 HPTCCV ACTUATION (Cont d) NO TIMER TIMER STATOR Ø ROTOR Ø CLEARANCE with TIMER No Air 5Th stage Air 5+9Th stage Air 0 s 8 s 152 s 182 s CLEARANCE without TIMER 34

35 PMC INPUT POWER COCKPIT SW: PMC On / Off PS12 INPUT SIGNALS: N1, T12, PLA OUTPUT SIGNALS: FOR MEC TORQUE MOTOR MONITOR CONNECTION 35

36 PMC PURPOSE In a high bypass engine, total thrust is more accurately controlled by controlling N1 speed. FAN is 80% of the POWER! This is accomplished by varying N2 speed to reach the accurate N1 speed. 36

37 PMC OPERATION The main goal of the PMC is to make pilot s job more comfortable. PMC is performing automatically 3 corrections: N1 Vs ALTITUDE N1 Vs PRESSURE N1 Vs TEMPERATURE 37

38 PMC OPERATION (Cont d) N1 Vs ALTITUDE As the altitude is increasing, if you want to keep a steady thrust %, you need to increase N1. N1 STEADY THRUST % Z PMC ON PMC increase N1 PLA remain unchanged. PMC OFF The PILOT must increase N1 PLA change. 38

39 PMC OPERATION (Cont d) N1 Vs PRESSURE As the pressure is decreasing, if you want to keep a steady thrust %, you need to increase N1. N1 STEADY THRUST % PMC ON PMC increase N1 PLA remain unchanged. P PMC OFF The PILOT must increase N1 PLA change. 39

40 PMC OPERATION (Cont d) N1 N1 Vs TEMPERATURE MAX THRUST T At takeoff, to get the max thrust (flat rated thrust) as temperature increases, N1 and EGT must also increase. But mechanical limitations impose a limit which is a temperature called: Corner Point or Flat Rated Temperature. Beyond it: EGT CORNER POINT TEMPERATURE PMC ON PMC is limiting N1 and EGT T PMC OFF The PILOT must limit N1 and EGT 40

41 PMC OPERATION (Cont d) PMC efficiency start at 50% N1 and is fully efficient at or above 70% N1. PMC trims MEC to maintain the commanded thrust Schedule N1 is compared to actual N1.The error signal generates from the PMC an Output Current (TMC) to a torque motor mounted on the MEC. The torque motor changes Fuel Flow (Wf). N2 and N1 change. 41

42 PMC OPERATION (Cont d) N1 / Z CORRECTION N1 / P CORRECTION N1 / T CORRECTION ACTUAL N1 SCHEDULE N1 PMC TORQUE MOTOR PMC on / off ENGINE Wf MEC PLA 42

43 THE END THANKS FOR YOUR ATTENTION! 43