PRINCIPLES OF NAVAL ENGINEERING 



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Figure 23-9. — Can-annular combustion chamber. 



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material used, the means provided for cooling 

 the bearings and highly stressed parts, and the 

 higher ratio of blade length to wheel diameter 

 which is required to accommodate the large 

 gas flow. 



The turbine section of a gas turbine engine 

 is located directly behind the combustion cham- 

 ber outlet. The turbine consists of two basic 

 elements, the stator and the rotor . Part of a 

 stator element is shown in figure 23-10; a rotor 

 element is shown in figure 23-11. 



The stator element is referred to by various 

 names, including turbine nozzle vanes and tur - 

 bine guide vanes . The vanes of the stator ele- 

 ment serve the same purpose as the nozzles 

 in an impulse steam turbine or the stationary 

 blading in a reaction steam turbine— that is, 

 they convert thermal energy into mechanical 

 kinetic energy. The vanes of the stator element 

 are contoured and set at such an angle that 

 they form a number of small nozzles which 

 discharge the gas as extremely high speed jets. 

 As in the case of the nozzles (or stationary 

 blading) of steam turbines, the increase in 



velocity may be equated with the decrease in 

 thermal energy. The vanes of the stator element 

 direct the flow of gas to the rotor blades at the 

 required angle while the turbine wheel is rotat- 

 ing. 



The rotor element of the turbine consists 

 of a shaft and a bladed wheel or disk. The wheel 

 is attached to the main power transmitting shaft 

 of the gas turbine engine. The jets of combus- 

 tion gas leaving the vanes of the stator element 

 act upon the turbine blades and cause the turbine 

 wheel to rotate at a very high rate of speed. 

 The high rotational speed imposes severe cen- 

 trifugal loads on the turbine wheel, and at the 

 same time the very high temperatures result in 

 a lowering of the strength of the material. 

 Consequently, the engine speed and temperature 

 must be controlled to keep turbine operation 

 within safe limits. Even so, the operating life 

 of the turbine blading is accepted as the govern- 

 ing factor in determining the life of the gas 

 turbine engine. 



The turbine may be of the single-rotor type 

 or of the multiple-rotor type. Either single-rotor 



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