INTRODUCTION
Application of the Gas laws in the gas turbine Engine
Gases behave differently from the other states of matter which are solids and liquids
We treat it differently on how they work
Gases don’t have fixed volume or shape, they are entirely molded by the container which are held.
There are three variables in which we can measure gas;
1) Pressure
2) Temperature
3) Volume
Gases behave differently from the other states of matter which are solids and liquids
We treat it differently on how they work
Gases don’t have fixed volume or shape, they are entirely molded by the container which are held.
There are three variables in which we can measure gas;
1) Pressure
2) Temperature
3) Volume
The combined gas laws
combining the two laws, we can determine what happens to the gases inside and engine when running where temperature, velocity and temperature are changing constantly.
Duct Design – the changes in pressure and velocity are done by the different shaped passages or ducts through where the air must pass before it leaves the engine. This duct design is vital, as the efficiency with which the changes from kinetic to pressure energy and vice versa occur are reflected in the overall efficiency of the engine.
Divergent duct – will increase the pressure of the air after it leaves the final stages of the compressor before it then enters the combustion chamber. Increase in pressure, temperature and decrease in velocity
Convergent duct - A duct which decreases in the direction of fluid flow and where velocity increases but temperature and pressure decrease. Converting some of the considerable pressure energy of the gas stream into kinetic energy will increase the efficiency with which we can instruct a turning effect upon the turbine and its shaft.
Divergent duct – will increase the pressure of the air after it leaves the final stages of the compressor before it then enters the combustion chamber. Increase in pressure, temperature and decrease in velocity
Convergent duct - A duct which decreases in the direction of fluid flow and where velocity increases but temperature and pressure decrease. Converting some of the considerable pressure energy of the gas stream into kinetic energy will increase the efficiency with which we can instruct a turning effect upon the turbine and its shaft.
Airflow through a pure turbo-jet engine
Single spool axial flow compressor turbo-jet engine
When a compressor and turbine are joined on one shaft, it is called a ‘spool’
This type of engine was considered the most useful where a high forward speed was the main aim.
This was used in fighter jets.
They are issues with the control of the smooth flow of air through the engine when it's in rotated speed range.
From the compressor, the air is fed into the combustion chambers and then fuel is added to result an ignition, as a result the increase in temperature causes a substantial increase in volume.
The energy needed to drive the compressor is now extracted from the stream as it passes through the turbine, the remaining energy in the gas stream acts as thrust as the gases pass to the atmosphere from the end of the jet pipe.
Single spool axial flow compressor turbo-jet engine
When a compressor and turbine are joined on one shaft, it is called a ‘spool’
This type of engine was considered the most useful where a high forward speed was the main aim.
This was used in fighter jets.
They are issues with the control of the smooth flow of air through the engine when it's in rotated speed range.
From the compressor, the air is fed into the combustion chambers and then fuel is added to result an ignition, as a result the increase in temperature causes a substantial increase in volume.
The energy needed to drive the compressor is now extracted from the stream as it passes through the turbine, the remaining energy in the gas stream acts as thrust as the gases pass to the atmosphere from the end of the jet pipe.
Airflow through a turbo-prop engine
A centrifugal compressor and axial flow compressor are turbo-prop engine.
The output from a turbo-prop engine is the sum of the shaft horse power developed at the turbine, and the residual jet thrust.
S.H.P at turbine + residual jet thrust = equivalent shaft horsepower (equivalent shaft horsepower)
The difference between the turbo jet and the turbo prop in using the generated power is thar, in the turbo jet, all of the energy that remains after the compressor has been powered and used as thrust.
Turbo jet
Energy to drive compressor = 50% the rest is used as thrust.
Turbo prop
energy to drive compressor and propeller = 95%
Only a small amount is available as thrust (residual thrust only)
A centrifugal compressor and axial flow compressor are turbo-prop engine.
The output from a turbo-prop engine is the sum of the shaft horse power developed at the turbine, and the residual jet thrust.
S.H.P at turbine + residual jet thrust = equivalent shaft horsepower (equivalent shaft horsepower)
The difference between the turbo jet and the turbo prop in using the generated power is thar, in the turbo jet, all of the energy that remains after the compressor has been powered and used as thrust.
Turbo jet
Energy to drive compressor = 50% the rest is used as thrust.
Turbo prop
energy to drive compressor and propeller = 95%
Only a small amount is available as thrust (residual thrust only)
Airflow through a turbo- shaft engine
this type of engine can be thought of as a turbo prop engine where the propeller has been replaced by a shaft
This engine can be used in applications where a compact supply of electrical power is required. The output shaft is attached to an alternator. (A.P.U)
Most turbo- shaft engines incorporate a free power turbine. A free power turbine is a turbine, which does not connect to any of the compressors. This gives it a wide range speed of operating.
This type are shorter, stiffer, and lighter engine, but needs centrifugal compressor to be used in the high pressure stage. This throws the air out radially so that it can enter the combustion chamber in the correct direction.
This is similar to the turbo jet engine but to the point where it leave the first stage turbine. The first stage turbine converts sufficient energy from the gas stream to the drive the compressor, and the free power turbine coverts any remaining to mechanical energy.
this type of engine can be thought of as a turbo prop engine where the propeller has been replaced by a shaft
This engine can be used in applications where a compact supply of electrical power is required. The output shaft is attached to an alternator. (A.P.U)
Most turbo- shaft engines incorporate a free power turbine. A free power turbine is a turbine, which does not connect to any of the compressors. This gives it a wide range speed of operating.
This type are shorter, stiffer, and lighter engine, but needs centrifugal compressor to be used in the high pressure stage. This throws the air out radially so that it can enter the combustion chamber in the correct direction.
This is similar to the turbo jet engine but to the point where it leave the first stage turbine. The first stage turbine converts sufficient energy from the gas stream to the drive the compressor, and the free power turbine coverts any remaining to mechanical energy.
Airflow through a low by pass ratio engine
By-pass ratio: the ratio of the amount of air which is by-passed around the core of the engine, to the amount of air which passes through the hot core
An engine with a by-pass ratio of about 1 or 2:1 is considered to be a low by-pass ratio engine
An engine with a by-pass ratio of around 5:1 is considered to be a high by-pass ratio engine.
Airflow through a high by pass ratio (turbo-fan) engine.
This has a high propulsive efficiency = 83%
The air enters the intake and passes immaditely into the low pressure compressor. It is then pressure before it splits to go either through the bypass duct air into the intermediate pressure compressor.
The thrust depends on the by-pass airflow, which has a high mass and relatively low velocity, hence its high propulsive efficiency.
The air passes through the hot core has a large energy added in the combustion chambers, but this energy is require to drive all of the compressors, which includes the fan.
By-pass ratio: the ratio of the amount of air which is by-passed around the core of the engine, to the amount of air which passes through the hot core
An engine with a by-pass ratio of about 1 or 2:1 is considered to be a low by-pass ratio engine
An engine with a by-pass ratio of around 5:1 is considered to be a high by-pass ratio engine.
Airflow through a high by pass ratio (turbo-fan) engine.
This has a high propulsive efficiency = 83%
The air enters the intake and passes immaditely into the low pressure compressor. It is then pressure before it splits to go either through the bypass duct air into the intermediate pressure compressor.
The thrust depends on the by-pass airflow, which has a high mass and relatively low velocity, hence its high propulsive efficiency.
The air passes through the hot core has a large energy added in the combustion chambers, but this energy is require to drive all of the compressors, which includes the fan.