JNTU
JNTU B.Tech III AIRCRAFT PROPULSION Previous Question Paper (March - 2021 - R18)
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Explain various components of an aircraft gas turbine engine and their functionality with the help of a neat diagram.
Answer
A gas turbine engine operates on the Brayton cycle and consists of several primary components:
- Inlet/Intake: Guides incoming air into the engine with minimal pressure loss and ensures uniform flow distribution to the compressor.
- Compressor: Increases the pressure and temperature of the incoming air. It can be axial or centrifugal, providing high-pressure air to the combustion chamber.
- Combustion Chamber: Fuel is injected and burned in the high-pressure air, significantly increasing the gas temperature and internal energy.
- Turbine: Extracts energy from the high-velocity, high-temperature exhaust gases to drive the compressor and accessories via a shaft.
- Exhaust/Nozzle: Accelerates the remaining gas energy to produce thrust by expanding it to ambient pressure.
Diagram description: The flow path starts at the inlet, moves through the compressor stages, enters the combustor, passes through the turbine stages, and exits through the nozzle.
What do you understand by Propulsive Efficiency? Enumerate the purpose of an aircraft gas turbine nozzle.
Answer
Propulsive Efficiency is defined as the ratio of the useful propulsive power developed by the engine to the total kinetic energy power supplied to the propulsive jet. It represents how effectively the kinetic energy of the exhaust is converted into useful work to move the aircraft.
Where V_a is the aircraft velocity and V_j is the jet exit velocity.
The primary purposes of an aircraft gas turbine nozzle are:
- To accelerate the gas stream to high velocities to generate the required thrust according to Newton's Second and Third Laws.
- To expand the high-pressure gases from the turbine exit down to ambient pressure.
- To provide the correct flow area to control the mass flow rate through the engine and ensure proper back-pressure for the turbine.
- In military applications, to provide vectoring capabilities or infrared signature reduction.
Draw a Schematic diagram of Ramjet engine and describe its operation. What are its advantages and disadvantages?
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A Gas turbine plant operates on the Brayton cycle between Tmin = 300 K and Tmax = 1073 K. Find the maximum work done per kg of air, and the corresponding cycle efficiency.
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Describe a procedure to carry out parametric cycle analysis of a turbo-fan engine, taking its component losses into account.
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An aircraft propeller flies at speed of 440 km/h. The diameter of the propeller is 4.1 m and the speed ratio is 0.8. The ambient conditions of air at the flight altitude are T = 255 K and P = 0.55 bar. Calculate the thrust obtained by the propeller engine.
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The stagnation temperatures at the inlet and exit of a combustion chamber are 600 K and 1200 K, respectively. If the heating value of fuel is 44 MJ/kg and specific heat at constant pressure for air and hot gases are 1.005 kJ/kg-K and 1.147 kJ/kg-K respectively, calculate the fuel air ratio.
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Explain the thrust vectoring phenomenon. Write a short note on diffuser losses and methods of mitigation.
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What is combustion loading parameter? Explain in brief about the process of ignition occurring inside a combustion chamber.
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Discuss in detail the total pressure losses associated with the design of a by-pass duct combustion chamber.
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Define degree of reaction. Discuss in brief about the Rotating Stall and Surging? Explain their consequences.
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Derive Euler’s energy equation for a turbo-machine and explain its physical meaning with a velocity diagram at rotor blade exit.
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What do you mean by multi-spooled turbines? Explain the relation between compressor pressure ratio and mass flow rate.
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Explain various methods of turbine blade cooling with the help of neat sketches.
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Write a note on ‘Engine thrust ratings’ bringing out clearly its significance in ensuring satisfactory engine life.
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Discuss briefly the contingencies experienced due to fuel injection inside combustors.
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