3601654_saif_mark - SAIF ALMEHREZI 1 Gas Turbine Engine...

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SAIF ALMEHREZI 1 Gas Turbine Engine Basics Task 1 1. Turbo Jet Engine Air Inlet Combustion Chambers Turbine Propelling Nozzle Compressor Cold Section Hot Section As shown above, the Turbojet engine is comprised of the compressor, combustion chambers, turbine and exhaust. The compressor is designed to direct intake air into the combustion chamber at a high velocity, while the combustion chamber is equipped with the fuel nozzles and igniters for combustion of the mixture (NASA 3). The expanding gases are used to turn the turbine, which helps to keep the engine in operation as it drives the compressor through the shaft (FOPPGS 1). Finally, the accelerated gases moving through the engine nozzle is used to provide thrust, which drives the aircraft. n c = T 2 – T 1 T 2a – T 1 INTAKE COMPRESION COMBUSTION EXHAUST
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SAIF ALMEHREZI 2 and n 4 = T 3 – T 4a T 3 – T 4 Apply the steady flow energy equation to get the equation: v 2 0 - v 2 1 = 2( h 1 – h 0 ) Change in kinetic energy and change in enthalpy: v 2 0 = 2 c p ( T 1 – T 0 ) Work output from the turbine balances the work input into the compressor, hence equating change in enthalpy results in: c p ( T 2a – T 1 ) = c p ( T 3 – T 4a ) T 2a – T 1 = T 3 – T 4a [ c p is constant] Airflow through the nozzle: v 2 5 = 2 c p ( h 4a – h 5 ) Since velocity is constant, v 4 = v 1 ≡ 0 Therefore, exit velocity at the nozzle: v 2 5 = 2 c p ( T 4a – T 5 ) Thrust, F = mv c - mv = m(v c – v) 2. Turboprop Engine Intake Prop Gearbox Compressor Turbine Exhaust
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SAIF ALMEHREZI 3 Shaft Combustion Chamber According to relevant sources, a turboprop engine is a turbine that drives a propeller via a reduction gear as shown in the above diagram (NASA 4). As such, the exhaust gases drive the power shaft, which in turn drives the reduction gear assembly through a shaft as shown (Husain 98; Sickle 205). The reduction gearing is essential because optimum propeller performances in these engine designs are reached at slower speeds than the engines’ operating revolution per minute. At slow airspeeds, these engine designs are fuel efficient and operate effectively (FOPPGS 1). Total Thrust = Nozzle thrust + Propeller thrust (Ganesan 225) = m a ( c j – c i ) + m a c i = m a (√2Δh noz n noz – c i + √n T Δh T n tr ) Where, Δh noz = enthalpy drop in the nozzle h T = enthalpy drop in the turbine n tr = transmission efficiency of the propeller and gears n T = turbine efficiency n noz = nozzle efficiency m a = mass flow rate in turbine
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SAIF ALMEHREZI 4 3. Turbofan high bypass engine High-pressure Fan High-pressure Shaft High-pressure Compressor Turbine Low-pressure Low-pressure Shaft Combustion Low-pressure Nozzle Compressor Chamber Turbine 2-spool high bypass engine with unmixed exhaust Turbofan engines were developed to incorporate some of the best features that exist in the already mentioned engines (FOPPGS 1). For example, these engines have been designed to
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3601654_saif_mark - SAIF ALMEHREZI 1 Gas Turbine Engine...

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