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JET PROPULSION Part 1 The Compressor. The principle of jet propulsion was demonstrated by Hero of Alexandria as long ago as the first century AD. However,

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Presentation on theme: "JET PROPULSION Part 1 The Compressor. The principle of jet propulsion was demonstrated by Hero of Alexandria as long ago as the first century AD. However,"— Presentation transcript:

1 JET PROPULSION Part 1 The Compressor

2 The principle of jet propulsion was demonstrated by Hero of Alexandria as long ago as the first century AD. However, the jet engine, as we know it, did not become a practical possibility until 1930 when Sir Frank Whittle patented the design of his first reaction motor suitable for aircraft propulsion. Introduction

3 The gas turbine engine, commonly referred to as the ‘jet’ engine, is an internal combustion engine which produces power by the controlled burning of fuel. In both the gas turbine and the motor car engine air is compressed, air is compressed, fuel is mixed with it, and the mixture is burnt. The heat which results produces a rapid expansion of the gas and this is used to do work. Introduction

4 COMPRESSOR TURBINE COMBUSTIONCHAMBER The compressor, situated at the front of the engine, is driven by the turbine, and performs two functions - it draws air into the engine and it compresses it before delivering it into the combustion chamber. The Compressor

5 Whenever air is forced into a smaller space, two things happen – The Pressure of the trapped air Increases, The Temperature of the trapped air Increases. A jet engine compressor is a constant flow of air, constantly being compressed. The Compressor

6 The Compressing Action consists of taking a quantity of air, and forcing it into a smaller space. This square represents a quantity of air This square represents the same quantity of air but squeezed into a smaller volume LET’S SEE HOW THIS IS DONE Compressor Operations

7 The Compressing Action consists of taking a quantity of air, and forcing it into a smaller space. Compressor Operations PUSH BACK SQUEEZE PUSH BACK SQUEEZE The air is pushed and squeezed into ever smaller spaces.

8 The Compressing Action consists of taking a quantity of air, and forcing it into a smaller space. This is why compressors are shaped the way they are Compressor Operations PUSH BACK BIG AT FRONT SMALL AT REAR SQUEEZE

9 BIG AT FRONT SMALL AT REAR Compressor Operations Compressors have a series of ‘stages’, each stage giving a small pressure rise over the previous stage.

10 Compressor Operations Each stage consists of a Rotor Blade to the front and a Stator Vane to the rear. FRONTREAR FIRSTSTAGE SECONDSTAGE THIRDSTAGE FOURTHSTAGE FIFTHSTAGE ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR

11 Compressor Rotor Blades are aerofoil sections producing lift, while rotating like propellers. As the blades rotate they force air to the rear, they do the ‘pushing’ back. Compressor Operations FRONTREARROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR

12 FRONTREAR The Stator Vanes are fixed to the engine casing, in clusters, or a complete ring. The vanes do the ‘squeezing’ or compressing of the forced back air. ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR

13 Compressor Operations FRONTREAR Each stage produces a small pressure rise which factored for the number of stages, would produce an overall pressure rise, known as the ‘Pressure Ratio’. Pressure ratios around 26:1 are common. (meaning pressure is 26 times ambient) ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATORFIRSTSTAGE SECONDSTAGE THIRDSTAGE FOURTHSTAGE FIFTHSTAGE

14 Due to the operating nature of the compressor, the airflow does not travel straight through it. The rotor blades push the air around the engine, whereas the stator vanes straighten it out. COMPRESSOR ROTO BLADE COMPRESSOR STATOR VANE CLUSTER CLUSTER The Compressor

15 Many modern engines have more than one compressor, because a high degree of compression requires a large number of compressor rows or ‘stages’. Each stage has an optimum speed for best efficiency – the smaller the blades the higher the speed. The Compressor

16 If all the stages are on the same shaft, only a few of them will be operating at their optimum speed. This is overcome by dividing the compressor into 2 or 3 parts, each rotating at its optimum speed. By this means, compression ratios up to 30:1 can be achieved, resulting in extremely high efficiency and very low specific fuel consumption. The Compressor

17 Check of Understanding When air is forced into a smaller space, what two things happen? Pressure Decreases Temperature Increases Pressure Increases Temperature Decreases Pressure Decreases Temperature Decreases Pressure Increases Temperature Increases

18 What does each stage of a compressor consist of? Rotor vanes and Stator blades Rotor vanes and Compressor blades Rotor blades and Compressor vanes Rotor blades and Stator vanes Check of Understanding

19 Which of the following statements is not true? Rotor blades rotate Stator vanes are like aerofoils Stator vanes are fixed to the engine casing Rotor blades force air backwards Check of Understanding

20 A compressor produces an overall pressure rise, What is this known as? Pressure increment Pressure angle Pressure ratio Pressure increase ratio Check of Understanding

21 What is the result of a high Pressure Ratio? Low specific fuel consumption High thrust to weight ratio High combustion ratio Low fuel temperatures Check of Understanding

22 Each stage of a compressor has an optimum speed for best efficiency. Which of the following applies? The smaller the vane the slower the speed The smaller the blade the higher the speed The smaller the vane the higher the pressure The smaller the blade the lower the pressure Check of Understanding

23 JET PROPULSION End of Presentation


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