THE POWER
OF FLIGHT
CFM56-3 REGULATION
1
RXCF 04/02/2006
THE POWER
OF FLIGHT
CFM56 - 3
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RXCF 04/02/2006
Speed Governing System
Fuel Limiting System
Idling System
Main Tasks
VBV
N1 Vs P
VSV
HPTCCV
Additional Tasks
MEC
N1 Vs Z
N1 Vs T
Corrections
PMC
CFM 56 - 3
ENGINE OPERATIONAL CONTROL
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RXCF 04/02/2006
THE POWER
OF FLIGHT
THE POWER
OF FLIGHT
ENGINE OPERATIONAL
CONTROL
• The CFM56-3 engine control system
consists of both:
HYDRO MECHANICAL UNIT
ELECTRONIC UNIT
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RXCF 04/02/2006
THE POWER
OF FLIGHT
HYDRO MECHANICAL UNIT
•
MEC Ì Main Engine Control
Automatically schedules:
– WF ( Fuel Flow ) N2
– VBV ( Variable Bleed Valve )
– VSV ( Variable Stator Vane )
– HPTCCV ( High Pressure Turbine Clearance
Control Valve )
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RXCF 04/02/2006
THE POWER
OF FLIGHT
ELECTRONIC UNIT
• PMC Ì Power Management Control
– Provide FAN scheduling
N1
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RXCF 04/02/2006
CONTROL SYSTEM SCHEMATIC
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RXCF 04/02/2006
THE POWER
OF FLIGHT
CONTROL SYSTEM SCHEMATIC
THE POWER
OF FLIGHT
(Cont’d)
N1
ÖFan Speed
N2
ÖCore Speed
WF
ÖFuel Flow
TMC
ÖTorque Motor Current
PS12
ÖFan Inlet Static Air Pressure
PS3
ÖCompressor Discharge Pressure
CBP
ÖCompressor Bleed Pressure
T12
ÖFan Inlet Total Air Temperature
T2.5
ÖHPC Inlet Air Temperature
T2
ÖFan Inlet Temperature
TC1
ÖTurbine Clearance Control 5Th Stage
TC2
ÖTurbine Clearance Control 9Th Stage
TC3
ÖTurbine Clearance Control Timer Signal
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RXCF 04/02/2006
THE POWER
OF FLIGHT
ENGINE STATIONS
25
12
HP Compressor Inlet
Secondary Flow Inlet
3
2
HP Compressor Discharge
Primary Flow Inlet
49. 5
Stage 2 LPT Inlet
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RXCF 04/02/2006
THE POWER
OF FLIGHT
MEC
OIL/ FUEL
HEAT
EXCHANGER
MEC
FUEL PUMP
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RXCF 04/02/2006
THE POWER
OF FLIGHT
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
METERING
SHUT-OFF
HP STAGE
VALVE
VALVE
PRESSURISING
VALVE
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RXCF 04/02/2006
THE POWER
OF FLIGHT
MEC PURPOSE
• The MEC’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
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RXCF 04/02/2006
SPEED GOVERNING SYSTEM
THE POWER
OF FLIGHT
MEC
SPEED
GOVERNING
SYSTEM
N2 demand
PS12
FMV
T2
N2 actual
Wf
Fuel
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RXCF 04/02/2006
THE POWER
OF FLIGHT
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
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RXCF 04/02/2006
THE POWER
OF FLIGHT
FUEL LIMITING SYSTEM (Cont’d)
MEC
T2.5
FUEL
PS3
SPEED
GOVERNING
LIMITING
SYSTEM
N2
CBP
SYSTEM
N2 demand
PS12
+/T2
N2 actual
FMV
Wf
Fuel
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RXCF 04/02/2006
THE POWER
OF FLIGHT
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:
Provide adequate taxi thrust while minimising
noise, fuel consumption and braking effort
•Flight idle:
Scheduled to minimise fuel consumption.
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RXCF 04/02/2006
THE POWER
OF FLIGHT
IDLING SYSTEM (Cont’d)
MEC
DESIRED
SPEED
T2.5
FUEL
PS3
AIRCRAFT
CONFIGURATION
LIMITING
PLA IDLE
Yes / NO
SYSTEM
SETTING
N2
CBP
N2 demand
PS12
+/T2
N2 actual
FMV
Wf
Fuel
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RXCF 04/02/2006
MEC ADDITIONAL TASKS
THE POWER
OF FLIGHT
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.
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
VBV SYSTEM (Cont’d)
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
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
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
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
1
Acceleration Schedule
5
If VBV not closed
3
Deceleration Schedule
4
If VBV not open
2
Operating Line
Efficiency ↓↓
Maxi
Efficiency
Design Point
3
MCT
STALL
REGION
ISO N1 Line
2
4
VBV
Operation
5
IDLE
1
BOOSTER OUTLET AIRFLOW
• Low speed or Deceleration
LOW EFFICIENCY
REGION
⇒ VBV OPEN
• High speed or acceleration
⇒ VBV CLOSED
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
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.
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
VSV SYSTEM (Cont’d)
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
VSV SYSTEM (Cont’d)
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
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)
IGV
- VSV optimise HPC efficiency.
ROTOR
- VSV improve stall margin for
transient engine operations.
VSV 1
Etc …
ROTOR
STAGE
IGV (Inlet Guide Vane)
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RXCF 04/02/2006
MEC ADDITIONAL TASKS (Cont’d)
THE POWER
OF FLIGHT
VSV PURPOSE (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
TYPICAL HPC FLOW CHART
1
Acceleration Schedule
Efficiency ↓↓
2
If VSV not open
Maxi
Efficiency
Design Point
3
Deceleration Schedule
4
Operating Line
2
1
MCT
STALL
REGION
ISO N1 Line
VSV
Operation
4
• Low speed or Deceleration
3
IDLE
COMPRESSOR OUTLET AIRFLOW
LOW EFFICIENCY
REGION
⇒ VSV CLOSED
• High speed or acceleration
⇒ VSV OPEN
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RXCF 04/02/2006
CLEARANCE CONTROL
THE POWER
OF FLIGHT
• 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
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RXCF 04/02/2006
CLEARANCE CONTROL (Cont’d)
THE POWER
OF FLIGHT
• 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.
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RXCF 04/02/2006
HPTCCV ACTUATION
THE POWER
OF FLIGHT
• Automatic Control is using Bleed Air from 5Th and 9Th stages of
HPC to either cool or heat the HPT shroud.
AIR
FROM
5Th
STAGE
N2 > 95 %
YES / NO
MEC
HPTCC TIMER
AIRCRAFT
ON THE
GROUND
YES / NO
HPTCC
VALVE
HPT SHROUD
AIR
FROM
9Th
STAGE
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RXCF 04/02/2006
HPTCCV ACTUATION (Cont’d)
THE POWER
OF FLIGHT
• 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.
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RXCF 04/02/2006
HPTCCV ACTUATION (Cont’d)
THE POWER
OF FLIGHT
• 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)
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RXCF 04/02/2006
HPTCCV ACTUATION (Cont’d)
THE POWER
OF FLIGHT
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RXCF 04/02/2006
HPTCCV ACTUATION (Cont’d)
THE POWER
OF FLIGHT
• The TIMER SEQUENCE:
- Starting Reference Point is when the engine reach 95 % N2.
- Then:
0 to 8 s
⇒ No air
8 to 152 s
⇒ 5Th stage air
152 to 182 s
⇒ 5Th + 9Th stage air
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RXCF 04/02/2006
HPTCCV ACTUATION (Cont’d)
NO TIMER
THE POWER
OF FLIGHT
TIMER
STATOR Ø
ROTOR Ø
CLEARANCE with TIMER
No Air
0s
5Th stage Air
8s
5+9Th stage Air
152 s
182 s
CLEARANCE without TIMER
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RXCF 04/02/2006
PMC
INPUT POWER
THE POWER
OF FLIGHT
COCKPIT SW:
Ö PMC On / Off
PS12
INPUT SIGNALS:
Ö N1, T12, PLA
OUTPUT SIGNALS:
Ö FOR MEC TORQUE MOTOR
MONITOR CONNECTION
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RXCF 04/02/2006
PMC PURPOSE
THE POWER
OF FLIGHT
• 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.
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RXCF 04/02/2006
PMC OPERATION
THE POWER
OF FLIGHT
• 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
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RXCF 04/02/2006
PMC OPERATION (Cont’d)
THE POWER
OF FLIGHT
N1 Vs ALTITUDE
• As the altitude is increasing, if you want to keep a steady thrust
%, you need to increase N1.
PMC ON
PMC increase N1
N1
⇒ PLA remain unchanged.
STEADY
THRUST %
PMC OFF
The PILOT must increase N1
⇒ PLA change.
Z
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RXCF 04/02/2006
PMC OPERATION (Cont’d)
THE POWER
OF FLIGHT
N1 Vs PRESSURE
• As the pressure is decreasing, if you want to keep a steady thrust %,
you need to increase N1.
N1
PMC ON
PMC increase N1
STEADY
THRUST %
⇒ PLA remain unchanged.
PMC OFF
The PILOT must increase N1
⇒ PLA change.
P
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RXCF 04/02/2006
PMC OPERATION (Cont’d)
N1 Vs TEMPERATURE
N1
• At
MAX
THRUST
T
EGT
THE POWER
OF FLIGHT
CORNER POINT
TEMPERATURE
T
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:
PMC ON
PMC is limiting N1 and EGT
PMC OFF
The PILOT must limit N1 and EGT
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RXCF 04/02/2006
PMC OPERATION (Cont’d)
THE POWER
OF FLIGHT
• 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).
Ì N2 and N1 change.
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RXCF 04/02/2006
PMC OPERATION (Cont’d)
N1 / Z
CORRECTION
N1 / P
CORRECTION
THE POWER
OF FLIGHT
N1 / T
CORRECTION
SCHEDULE
N1
ACTUAL
N1
PMC
ENGINE
Wf
TORQUE
MOTOR
PMC on / off
MEC
PLA
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RXCF 04/02/2006
THE POWER
OF FLIGHT
TH E
E ND
THANKS FOR YOUR
ATTENTION !
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RXCF 04/02/2006