How does an aircraft engine Produce electricity ? System Description, Operation, Components Location.
Hello everyone, welcome to my new technical blog .
This blog is for training purpose only .
Today we will discuss about how does an A320 aircraft engine produce electricity.
As we know A320 aircraft is having 2 engine and Each engine (HP rotor) controls its related Integrated Drive Generator (IDG) through the accessory gearbox. The drive speed changes in relation to the engine rating.
The IDG supplies 115/200 VAC, 3-phase, 400 Hz power to the engine and aircraft, at the Point of Regulation (POR).
The IDG has two parts:
· The drive with the Constant Speed Drive (CSD) and,
· The generator.
The hydromechanical CSD with its servo-valve operate the AC generator at constant speed.
Component Location :
A. IDG System Control
(1)The IDG is installed on the rear left side of the engine main gearbox.
(2)The IDG Quick-Attach-Detach (QAD) adapter is installed on the IDG mounting pad on therear left side of the main gearbox.
(3)The IDG power-cable disconnect-block is attached to the IDG housing at the 10o'clockposition.
(4)The IDG power cables are connected, at one end, to the lower IDG power-cable disconnect-block attached to the IDG. The other end of the IDG power cables is connected to the upperIDG power-cable disconnect-block installed on the left pylon above the diffuser case.
(5)The IDG fuel/oil heat-exchanger is installed at the 9 o'clock position on the High PressureTurbine (HPT) case.
(6)The IDG fuel/oil heat-exchanger pressure-sensor is installed below the IDG fuel/exchanger.
(7)The IDG oil/oil heat-exchanger is at the 9 o'clock position on the diffuser case.
IDG and Generator Control Unit (GCU)
In flight, the IDG supplies AC power (115 VAC/400 Hz) to the aircraft with its two units:
·The CSD unit
The engine-driven CSD unit changes the input speed (XX - XX rpm) from the main gearbox into aconstant rotational speed of 24000 rpm.The constant 24000 rpm speed from the CSD unit is transmitted to the generator which supplies ACpower (115 VAC/400 Hz) to the aircraft.
(2)The GCU, installed in the maintenance equipment center, is used to control the voltageand frequency. It is also used to prevent the electric-power generation channel from theovercurrent. The GCU receives an input speed signal from the IDG speed sensor.
(a)Each GCU controls its related IDG:
·GCU1 controls IDG1.
·GCU2 controls IDG2.
(b)The primary functions of the IDG regulation and protection are:
·The regulation of the generator voltage at the POR
·The regulation of the generator speed·The monitoring and protection of the system.
(3)The IDG oil-cooling system lubricates the IDG and decreases its temperature. The systemcontrols the IDG oil temperature with a heat movement between the IDG oil, the engine oil,and the engine fuel. The IDG oil-cooling system operates independently from the engine oilsystem.
(a) The IDG oil-cooling system is a passive system. It has two sections:
· An oil/oil heat-exchanger
· A fuel/oil heat-exchanger
. The oil flows out of the IDG to the core of the oil/oil heat exchanger where the heat from the IDG oil is transmitted to the engine oil. This usually occurs in hot conditions when the engine is at idle and the generator oil system is hotter than the engine oil system.
(4) In normal conditions, the heat is transmitted to the IDG oil from the engine oil. Then, the oil flows downstream to the IDG fuel/oil cooler to decrease the temperature of the IDG. An IDG fuel/oil-cooler bypass-valve keeps the IDG oil temperature to a minimum. To keep the IDG-oil maximum temperature, the IDG oil flows continuously through the fuel/oil heat exchanger.
Generator Control Unit :
(1) Input data
Each GCU receives the signals that follow from its related IDG:
· Oil inlet temperature
· Oil outlet temperature
· Low oil pressure
· Clogged filter indication
· PMG 3-phase output voltage
· CT 3-phase signal.
(2) Output data
Each GCU supplies the output analog data that follow to the System Data Analog Converter (SDACs), through the an ARINC 429 link:
· IDG oil-output temperature
· IDG oil-inlet temperature
· AC load at the POR
· AC frequency (phase A)
· AC voltage (phase A) at the POR.
It also supplies the SDACs with the discrete information that follows through an ARINC 429 link:
· Overload warning
· Generator fault
· IDG disconnect status
· IDG-disconnect pushbutton position
· IDG oil-outlet overheat
· IDG-oil low pressure
· GEN pushbutton-switch position
· Clogged filter information
· Low oil-level indication
· IDG oil-outlet temperature-advisory.
Component Description :
(1)The IDG has the components that follow:
- Electrical circuit ·
Terminal block with a terminal block cover · Electrical connectors A, B and C.
· Oil replenishing circuit
· Oil drainage circuit
· Oil level sight-glass
· Oil scavenge filter-element
· Oil charge filter-element
· Vent valve
· IDG reset ring.
(3)Inspection · Clogging indicator of the oil scavenge filter on the IDG oil-out line.
· Oil-in port
· Oil-out port.
(B) The IDG has a CSD unit and a generator installed in a magnesium-cast housing. The speed conversion components are the gear differential and the hydraulic trim unit. The engine gearbox supplies the variable-speed shaft power to the IDG input shaft, which is directly connected to the carrier shaft of the differential.
The IDG CSD unit has a disconnect mechanism to disengage the input shaft attached to the main gearbox.
The disconnection is necessary to prevent internal mechanical damage if a failure of the IDG oil-cooling system occurs. IDG servo valve
Generator speed control
· A system with a servo valve in the IDG and an electronic control circuit in the GCU control the generator speed.
This system sets the position of the wobbler of the variable displacement hydraulic-unit.
Electronic control circuit
· The electronic control circuit monitors the generator PMG frequency and compares it with a reference source. If there is an error signal, the control circuit causes the servo valve to increase or decrease the control piston pressure as necessary to set the generator frequency back to 400 Hz.
The IDG has the components that follow: Internal components connected to connector A
· The PMG stator
· Three current transformers
· Disconnect solenoid
· The charge pressure switch.
Internal components connected to connector B
· The main exciter
· The oil-in and oil-out temperature bulbs
· The oil level sensor
· The clogged filter indicator.
Internal components connected to connector C
· The servo valve.
The IDG drive splines are lubricated by the engine oil-cooling system, which supplies a stream of oil to the center of the shaft. Oil from the shaft goes through the splines and is released into the gearbox cavity through radial holes in the shaft.
IDG cooling and lubrication system:
· The oil goes into the IDG at the opposite side of the drive end through the DPI filter and then goes to:
· The differential gear
· The input seal
· The charge pump
· The generator stator and rotor.
The oil supplied to the differential gear also cools the PMG stator by spraying and lubricates the disconnect spline.
The input housing has rectangular grooves around the main generator stator core in which oil flows to cool the stator and keep a low IDG surface temperature. The charge pump draws in the oil flow at its suction port and increases its pressure.
The oil that goes into the rotor cools the components that follow:
· The exciter and main generator rotors
· The exciter and main generator windings
· The diodes.
Then, this oil goes directly to the deaerator or to the IDG sump where it is scavenged and pumped to the deaerator. The oil is deaerated and before it goes to the supply pump. There it runs through the scavenge filter into the external system lines for cooling.
(8) IDG sensors and protective components:
(a)IDG oil filter Differential Pressure Indicator (DPI):
· The scavenge filter has an oil filter DPI. The indicator shows when it is necessary to replace the oil filter elements.
· The sensing device for the oil filter DPI is automatically inhibited during cold oil-running conditions. This prevents unwanted operation because of a high oil viscosity.
· It is necessary to replace the two filters elements when the DPI is extended.
(b)IDG automatic and manual thermal :
disconnect-mechanism 1 2 The manual disconnect mechanism has a solenoid, a spring-loaded disconnect plunger, a cam shaft and a reset ring. The crew pushes the IDG pushbutton switch when the IDG FAULT legend comes on. When activated, the IDG cannot be connected again in flight. At an IDG oil temperature of 199 deg.C (390.2 deg.F), an automatic thermal disconnect-mechanism disconnects the IDG.
(c)IDG charge-oil pressure-switch :
· The switch is usually closed when the IDG is stop and open when the IDG operates correctly.
· The charge switch operates when the engine is at the normal operating speed. When the IDG charge pressure decreases to a minimum safe value, it transmits a signal to the GCU. The IDG FAULT legend comes on the ELEC panel. At the same time, the IDG LOW OIL PR caution message is shown on the upper Electronic Centralized Aircraft Monitoring (ECAM) Display Unit (DU). Clogged-filter indicator · The clogged filter indicator is in the IDG scavenge oil system. If the scavenge filter is clogged, the indicator will send a ground signal to the GCU. · The GCU transmits a status signal to the ECAM system. The ECAM generates an IDG MINOR FAULT warning with a related IDG CLOGGED FILTER message through the Centralized Maintenance System (CMS).
(d)Remote Oil Level Sensor (ROLS) :
· The ROLS uses a thermal dispersion method to monitor the IDG oil level and find if a sensor is wet or dry. If a sensor is dry, an "ELEC IDG 1 (2) OIL LO LVL" ECAM warning is shown on the upper ECAM DU with a related "LOW OIL LEVEL/IDG1 (2) (E1 (2)-4000XU)" message through the CMS.
(e)IDG oil-out and oil-in temperature sensor :
· The oil-out and oil-in temperature sensors of the IDG are sensed by the GCU to do the ECAM oilout temperature and delta (oil-out minus oil-in) temperature reporting.
The oil temperature sensors are thermistor components and have a nominal resistance of 100 +10 ohms -10 ohms at ambient IDG case temperature.
(a) IDG oil pressure filling
· A quick-filling coupling is installed on the transmission casing for pressure filling.
The oil pumped into the IDG, through the pressure fill port, flows through the filter and then through the external oil circuit and into the IDG case.
· The air that is in the circuit is pushed out by the oil and released through the open overfill-drain port. When the oil level in the IDG sump become stable at the top of the open overfill standpipe, the level in the IDG system is correct.
NOTE: Motoring is not necessary for oil level check or oil replenishment. Vertical oil-level sight-glass Different colors (red, yellow, green), related to the oil level, show when the oil servicing of the IDG is necessary.
IDG reset ring A mechanical reset ring is installed on the IDG. The handle is used to connect the drive again while the engine is stopped and stationary on the ground.
The IDG is an Line Replaceable Unit (LRU).
IDG Fuel/Oil Heat-Exchanger:
◆The IDG fuel/oil heat-exchanger controls the supply oil temperature to the IDG.
It is installed downstream of the IDG oil/oil heat-exchanger.
◆The IDG fuel/oil heat exchanger transfers heat from the IDG oil to the engine fuel. The cooled IDG oil is sent to lubricate and cool the IDG.
◆The IDG fuel/oil heat-exchanger has internal tubes through which the engine fuel flows. These tubes go through the IDG oil core which has baffles to increase the surface area for heat transfer.
◆The IDG fuel/oil heat-exchanger includes an oil bypass valve that helps to keep the IDG-oil minimum temperature: The oil from the IDG that is not cooled is mixed with the cooled oil from the IDG fuel/oil heat-exchanger.
◆The oil bypass valve is a viscosity control valve that operates independently from the Electronic Engine Control (EEC) (passive operation).
◆At engine start-up, when the IDG oil temperature is low, the valve is in the full bypass position.
◆At moderate temperatures, the valve controls the oil flow. In this position, the valve mixes the oil from the IDG that is not cooled and the cooled oil from the fuel/oil heat-exchanger. Then it sends the oil back to the IDG.
◆At the high limit of the IDG-oil temperature range, the valve is in non-bypass (full cooling) position and 100 percent of the IDG oil flows through the fuel/oil heat-exchanger.
◆The IDG fuel/oil heat-exchanger is a LRU.
IDG Power Cables:
(1) Four IDG power cables supply IDG-generated 115VAC/400 Hz power to operate the aircraft electrical systems.
(2) The IDG power cables are connected independently (not as a bundle) to terminal blocks at each end.Line blocks and clamps hold the cables in position along the left side of the engine core.
(3) The IDG power cables are LRUs.
IDG QAD Adapter:
(1) The IDG QAD adapter is used for quick replacement of the IDG.
(2) The IDG QAD adapter-kit,includes a gasket for the main gearbox mounting-pad ,
and has the components that follow:
(a)QAD ring - mates with the IDG input flange. (b)QAD ring lugs - mate with the IDG input-flange lugs.
The IDG is correctly installed when the white open-position marks on the IDG and QAD ring align. In this position, the locator pin on the IDG is aligned with the locator hole in the QAD ring.
(c. Tension bolt - tightened to engage the IDG flange lugs into the QAD ring until the ring turns into the locked position.
(3) The IDG QAD adapter is an LRU.