Chapter 23. -GAS TURBINE 



COMBUSTION 

 CHAMBER 

 HOUSING 



COMBUSTION 



CHAMBER 



LINER 



COMBUSTION 



CHAMBER 



COVER 



COMBUSTION 



CHAMBER 

 INLET DUCT 



147.142 



Figure 23-8,— Elements of tubular or can-type combustion chamber. 



Since each of the combustion chambers has its 

 own separate burner, each one operating inde- 

 pendently of the others, there must be some way 

 to spread the flames during starting. This re- 

 quirement is met by interconnecting all the 

 chambers so that, as the flame is started by the 

 spark ignition plugs in the lower chambers, the 

 flame passes through the interconnector tubes 

 and ignites the combustible mixture in the ad- 

 jacent chambers. Once ignition is obtained, the 

 spark igniters are automatically cut off. 



The annular combustion chamber is more 

 efficient than the can-type chamber. Although 

 details of design may vary, the annular com- 

 bustion chamber consists essentially of a single 

 chamber which completely surrounds the engine. 

 Fuel enters the combustion chamber through a 

 series of nozzles which are mounted equidistant 

 from each other on a ring at the front end of the 

 combustion chamber; because of this arrange- 

 ment, the flame is distributed evenly around the 

 entire circumference of the combustion cham- 

 ber. Diffusion of air and an efficient flame 

 pattern are maintained by means of rows of 

 holes which are punched in the outer liner or 

 basket of the combustion chamber. 



The can-annular combustion chamber com- 

 bines features of both the can-type chamber 

 and the annular chamber. The can-annular 

 chamber allows an annular discharge from the 

 compressors, from which the air flows to indi- 

 vidual burners where the fuel is injected and 

 burned.- The can-annular combustion chambers 

 are arranged radially around the axis of the 

 engine— the axis in this instance being the rotor 



shaft housing. Figure 23-9 shows the arrange- 

 ment of can-annular combustion chambers. 



The can-annular combustion chambers are 

 enclosed by a removable steel shroud which 

 covers the entire burner section. This feature 

 makes the burners readily accessible for any 

 required maintenance. 



The can-annular combustion chambers are 

 interconnected by means of projecting flame 

 tubes. These flame tubes facilitate starting, 

 as previously described in connection with the 

 can-type combustion chamber. 



Each of the can-annular combustion cham- 

 bers contains a central, bullet-shaped, perfo- 

 rated liner. The size and shape of the holes are 

 designed to admit the correct quantity of air 

 at the required velocity and angle. Cutouts are 

 provided in two of the bottom chambers for the 

 installation of the spark igniters. 



Each can-annular combustion chamber re- 

 ceives fuel through duplex nozzles installed at 

 the forward end of the chamber. Guide vanes 

 around the fuel nozzles direct the primary air 

 and cause it to enter the combustion chamber 

 with a swirling motion which mixes the fuel 

 and air and thus leads to even and complete 

 combustion. 



Turbine 



In theory, design, and operating character- 

 istics, the turbines used in gas turbine engines 

 are quite similar to the turbines used in a 

 steam plant. The gas turbine differs from the 

 steam turbine chiefly in the type of blading 



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