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Introduction:
Efforts to design a working gas turbine engine had been under way for year's prior world war II. Engineers eventually succeeded in placing a few engines in combat aircraft briefly during the closing stages of the war.
The war effort had brought about many advances in gas turbine technology, which could now be used for commercial aircraft design.
Turbine engines offered many advantages over reciprocating engine and airlines were interested.
Increased reliability, longer mean times between overhaul, higher airspeeds, ease of operation at high altitudes and a high power to engine weight ratio made turbine power very desirable.
ENGINE COMPONENTS:
Within every gas turbine engine there are seven basic sections.
1. AIRINLET
2. COMPRESSOR SECTION
3. COMBUSTION SECTION
4. TURBINE SECTION
5. EXHAUST SECTION
6. ACESSORY SECTION
7. SYSTEM NECESSARY FOR STARTING, LUBRICATION, FUEL SUPPLY AND AUXILIARY PURPOSES SUCH AS ANTIICING, COOLING AND PRESSURERATION;
Sometimes you hear about additional terms include cold section and hot section.
The engine\'s cold section includes the air inlet duct and the compressor section.
The hot section, on the other hand, includes the combustion and exhaust section.
PURPOSE OF THE ENGINE COMPONENTS:
The AIRINLET to a turbine engine has several functions, one of which is to recover as much of the total pressure of the free air stream as possible and deliver this pressure to the compressor.
There are two different types of COMPRESSOR SECTIONS.
A single-spool ... and a multi-spool compressor.
A single-spool compressor consists of one rotor assembly and stators with as many stages as necessary to achieve the desired pressure ratio and all the airflow from the intake passes through the compressor.
The multi-spool compressor consists of two or more rotor assemblies, each driven by their own turbine at an optimum speed to achieve higher-pressure ratios and to give greater operating flexibility.
This trend is taken a stage further with the high bypass ratio turbo-fan.
The COMBUSTION CHAMBER has the difficult task of burning large quantities of fuel, supplied through the fuel spray nozzles, with extensive volumes of air.
Within the minimum loss in pressure and with the maximum heat release for the limited spacer available this task must be accomplished.
The temperature rise to the range between 850 to 1700deg.C.
Three main types of combustion chamber are in use for gas turbine engines.
1. MULTIPLE COMBUSTION CHAMBER
2. TURBO-ANNULAR CHAMBER
3. ANNULAR CHAMBER
The turbine has the task of providing the power to drive the compressor and accessories and, in the case of engines, which do not make use solely of a jet for propulsion, of providing shaft power for a propeller or rotor.
The typical exhaust section extends from the rear of the turbine section to the point where the exhaust gases leave the engine.
The components include the exhaust cone, exhaust duct or tailpipe and exhaust nozzle.
OPERATION:
The fan -, booster rotor and the low-pressure-compressor rotor are on the same low-pressure shaft (N1).
The fan increases the speed of air.
A splitter fairing divides the air into these two air flows:
*Primary
The primary airflow goes into the core of the engine.
The booster increase the pressure of this air and sends it to the HPC (high pressure compressor).
*Secondary
The secondary airflow goes in the fan duct. it supplies approximately
80% of the thrust during take-off.
*HPC
The HPC rotor and the HPT rotor are on the same high-pressure shaft (N2).
The HPC is, it depends in the built up, a nine-stage compressor. It increases the pressure of the air from the LPC and sends it to the combustor. The HPC also supplies bleed air for the aircraft pneumatic system and the engine air system.
*COMBUSTOR
The combustor mixes air from the compressors and fuel from the fuel nozzles. This mixture of air and fuel burns in the combustion chamber to make hot gases. The hot gases go to the HPT.
*HPT
The HPT changes the energy of the hot gases into a mechanical energy. The HPT uses this mechanical energy to turn the HPC rotor and the accessory drive.
*LPT
The LPT changes the energy of the hot gases into a mechanical energy.
The LPT uses this mechanical energy to turn the fan and the booster rotor.
*ACCESSORY DRIVE
The accessory drive has these components:
-Inlet gearbox
-Radial drive shaft
-Transfer gearbox
-Horizontal drive shaft
-Accessory gearbox (AGB)
The N2 shaft turns the AGB through these shafts and gearboxes.
The AGB holds and operates the airplane accessories and the engine accessories.
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