Turbine Assembly
The first of a turbine assembly is the nozzle guide vane, which directs the air axially onto the blades of a rotor section.
Gearboxes are used to operate accessories, or to power propellers or rotors.
The energy in the gas stream flowing takes several forms; Heat energy, potential energy and kinetic energy.
The conversion of this energy into mechanical energy tells us that its value will be reduced as the gas stream passes through the turbine. However, the velocity of the gas in the combustion chamber is lower than the eventual velocity of the gas when it reaches the exhaust unit.
Gearboxes are used to operate accessories, or to power propellers or rotors.
The energy in the gas stream flowing takes several forms; Heat energy, potential energy and kinetic energy.
The conversion of this energy into mechanical energy tells us that its value will be reduced as the gas stream passes through the turbine. However, the velocity of the gas in the combustion chamber is lower than the eventual velocity of the gas when it reaches the exhaust unit.
Stresses in the Turbine
the blade tips travel around 1,500 feet per second and at the same time the temperature of the gases driving the turbine can reach around 1,700C. The speed of gases come close to the speed of sound. No matter what the material is, the temperature and the speed limits of the engine and therefore a blade will have a finite life before stresses/failure occurs.
Turbine Blade Materials
Early gas turbine engines were made of high temperature steel. Next advance in technology was use of nickel bade alloys.
Turbine Stage
the compressor adds energy to the gas stream by increasing its pressure. that energy is then extracted in the turbine by it reducing the pressure of the gases flowing through it and then there's a drop in pressure energy occurs both as it is converted into kinetic energy in the nozzle guide vanes, and also converted into mechanical energy in the turbine blades.
Free Turbine
A free Turbine is a turbine which is not connected to the compressor, it is connected only either the propeller or to the rotor reduction gear. As it doesn't have a compressor, allows free turbine to seek its own optimum design speed.
the blade tips travel around 1,500 feet per second and at the same time the temperature of the gases driving the turbine can reach around 1,700C. The speed of gases come close to the speed of sound. No matter what the material is, the temperature and the speed limits of the engine and therefore a blade will have a finite life before stresses/failure occurs.
Turbine Blade Materials
Early gas turbine engines were made of high temperature steel. Next advance in technology was use of nickel bade alloys.
Turbine Stage
the compressor adds energy to the gas stream by increasing its pressure. that energy is then extracted in the turbine by it reducing the pressure of the gases flowing through it and then there's a drop in pressure energy occurs both as it is converted into kinetic energy in the nozzle guide vanes, and also converted into mechanical energy in the turbine blades.
Free Turbine
A free Turbine is a turbine which is not connected to the compressor, it is connected only either the propeller or to the rotor reduction gear. As it doesn't have a compressor, allows free turbine to seek its own optimum design speed.
Blade Shape
nozzle guide vanes are of aerofoil shape and the space between two nozzle guide vanes forms a convergent duct Loses in the turbine - the turbine is a very efficient mechanical device but however there's around 8% energy loss in turbine.
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Multi Spool Engines
It is more effective to have an increase in the number of stages which comprise the turbine and this allows in power output with a reduction in turbine diameter. The efficiency of the turbine blade increases as its rotational speed increases. |