# JET PROPULSION Part 1 The Compressor.

## Presentation on theme: "JET PROPULSION Part 1 The Compressor."— Presentation transcript:

JET PROPULSION Part 1 The Compressor

Introduction 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 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, 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.

The Compressor 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. COMBUSTION CHAMBER COMPRESSOR TURBINE

The Compressor 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.

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

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

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

Compressor Operations
Each stage consists of a Rotor Blade to the front and a Stator Vane to the rear. FIRST STAGE SECOND STAGE THIRD STAGE FOURTH STAGE FIFTH STAGE ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR FRONT REAR

Compressor Operations
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. ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR FRONT REAR

Compressor Operations
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 FRONT REAR

Compressor Operations
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) FIRST STAGE SECOND STAGE THIRD STAGE FOURTH STAGE FIFTH STAGE ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR ROTOR STATOR FRONT REAR

The Compressor 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 ROTO BLADE STATOR VANE CLUSTER STATOR VANE CLUSTER

The Compressor 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 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.

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

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

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

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

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

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

JET PROPULSION End of Presentation