Gas Turbine Engine Fundamental & Theory .pptx

Fundamental of GTE

1. GAS TURBINE ENGINE MODULE 15.1 FUNDAMENTALS Issue: 01 Revision: 00 Module 15.1 1

2. 15.1 FUNDAMENTALS 15.1.1 Potential energy, kinetic energy, Newton’s laws of motion, Brayton cycle 15.1.2 The relationship between force, work, power, energy, velocity, acceleration 15.1.3 Constructional arrangement and operation of turbojet, turbofan, turboshaft , turboprop. Issue: 01 Revision: 00 Module 15.1 Page No: 2

3. 15.1.1 Potential energy, kinetic energy, Newton’s laws of motion, Brayton cycle. Issue: 01 Revision: 00 Module 15.1.1 Page No: 3 Energy is used to perform useful work. In the gas turbine engine this means producing motion and heat. Recall the law of Conservation of Energy: “Energy can neither be created nor destroyed. It can only be changed from one form to another” . The two forms of energy which best describe the propulsive power of the jet engine are potential and kinetic energy.

4. Potential energy Potential energy (PE) is stored energy. PE = Weight x Height If weight of an aircraft W is 20,000 lbs and height H is 5 feet above the ground, Its PE = 20,000 x 5 = 100,000 foot.lbs Issue: 01 Revision: 00 Module 15.1.1 Page No: 4 The energy stored in an object derived from its position or condition. An aircraft in flight has potential energy due to its mass, height and velocity. Fuel has potential energy which is released during combustion.

5. Kinetic Energy Issue: 01 Revision: 00 Module 15.1.1 Page No: 5 The energy possessed by a body because of its motion. The kinetic energy of an object depends on its mass and velocity. Potential energy is released as kinetic energy. When the aircraft lands - its potential energy is converted into kinetic energy - its kinetic energy is converted into heat by the brakes. The potential energy of fuel is released as kinetic energy during combustion. The formula for kinetic energy is: Kinetic Energy = ½ mass x velocity 2 KE = ½mv 2

6. Issue: 01 Revision: 00 Module 15.1.1 Page No: 6 LAWS OF THERMODYNAMICS The laws of thermodynamics describe the processes of heat and work in a system. There are two laws of thermodynamics that explain the internal cycle of events of the gas turbine engine, they are: The first law deals with the conservation of energy. The second deals with heat transfer.

7. Issue: 01 Revision: 00 Module 15.1.1 Page No: 7 The first law of thermodynamics states that: “Energy cannot be created or destroyed but can be changed in form.” In a gas turbine engine, the mass air flow is first heated by compression Then heated by combustion with the addition of fuel. The velocity of the mass airflow increases due to expansion. Some heat is converted into work to rotate the turbine. Heat energy is changed to thrust and the gases are cooled as they pass through the turbine section and out the jet nozzle.

8. Issue: 01 Revision: 00 Module 15.1.1 Page No: 8 The second law of thermodynamics states that in a heat engine : “Temperature differences between systems in contact with each other tend to even out and that work can be obtained from these differences, but that loss of heat occurs, when work is done”. Heat cannot flow from a cooler body to a hotter body. It must flow from hotter toward cooler. There is always heat loss to the surrounding air or structure. Therefore, NO heat engine is 100% efficient.

9. Newton’s Laws of Motion First Law A body at rest tends to remain at rest, and a body in motion tends to continue in motion in a straight line unless caused to change it’s state by an external force. Second Law The acceleration of a body is directly proportional to the force causing it, and inversely proportional to the mass of the body. Issue: 01 Revision: 00 Module 15.1.1 Page No: 9

10. F = ma where F = force, m = mass, a = acceleration Example of Newton’s 2 nd Law is : A propeller accelerates a large mass of air, but it’s velocity is low. A turbojet engine imparts a relatively small mass of air, but the acceleration that has taken place within the engine is large. Newton’s 2 nd Law deals with acceleration and it explains the thrust produced by a turbine engine. Issue: 01 Revision: 00 Module 15.1.1 Page No: 10

11. Newton’s 2 nd law Issue: 01 Revision: 00 Module 15.1.1 Page No: 11 Propeller - moves LARGE MASS of air at low velocity Jet - moves small mass of gas at HIGH VELOCITY

12. Third Law For every action there is a equal and opposite reaction. A turbojet engine accelerating a mass of air backward creates an equal amount of force pushing the aircraft forward. Issue: 01 Revision: 00 Module 15.1.1 Page No: 12

13. Newton’s 3rd law Issue: 01 Revision: 00 Module 15.1.1 Page No: 13 FORWARD MOVEMENT (REACTION) ACCELERATION OF MASS AIR (ACTION)