DOC AIRBUS | AMM A320FCOMBUSTION SECTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The combustion section includes the diffuser and combustion group, the No. 4 bearing section and the turbine nozzle assembly.
The combustion section has four primary functions:
** ON A/C NOT FOR ALL The combustion section includes the diffuser and combustion group, the No. 4 bearing section and the turbine nozzle assembly.
Combustion SectionThe combustion section has four primary functions:
- straighten the flow of air from the HP compressor,
- change the flow of air characteristics to get the best speed and pressure for combustion,
- mix fuel with the air and supply ignition to make the fuel burn,
- hold the No. 4 bearing in position.
2. Diffuser Case and Combustor Assemblies
A. Diffuser Case
The diffuser case is a main structural part of the engine. The diameter of the diffuser section is larger at the rear than at the front. This diametral difference decreases the speed of the air and changes the energy of the speed into pressure. The diffuser case has 20 mounting pads, where the fuel injectors are installed, two mounting pads where the ignitor plugs are installed and six borescope bosses located around the case.
The diffuser case is a one piece casting whose outer and inner walls form the contour for diffusing and guiding air around the combustor. The inner wall is supported by twenty hollow struts at the front of the case. These struts provide passage for service plumbing to the No. 4 bearing compartment and other areas. A double seal consisting of brush and knife edge seals is bolted at the front inner diameter of the case. These seals align with sealing surfaces on the HP compressor rotor rear shaft. The seals prevent leakage of HP compressor discharge air into the diffuser case. An exit stator, bolted at the same location, straightens air for entry to the diffuser portion of the diffuser case prior to entering the combustion chamber.
The diffuser case is a main structural part of the engine. The diameter of the diffuser section is larger at the rear than at the front. This diametral difference decreases the speed of the air and changes the energy of the speed into pressure. The diffuser case has 20 mounting pads, where the fuel injectors are installed, two mounting pads where the ignitor plugs are installed and six borescope bosses located around the case.
The diffuser case is a one piece casting whose outer and inner walls form the contour for diffusing and guiding air around the combustor. The inner wall is supported by twenty hollow struts at the front of the case. These struts provide passage for service plumbing to the No. 4 bearing compartment and other areas. A double seal consisting of brush and knife edge seals is bolted at the front inner diameter of the case. These seals align with sealing surfaces on the HP compressor rotor rear shaft. The seals prevent leakage of HP compressor discharge air into the diffuser case. An exit stator, bolted at the same location, straightens air for entry to the diffuser portion of the diffuser case prior to entering the combustion chamber.
B. Combustor
The combustor is an annular type combustor which consists of an outer liner assembly and an inner liner assembly.
Each liner assembly is comprised of a liner shell and mechanically attached segments which form the inner wall of the combustion chamber. Air which surrounds the combustor is used in the combustion process for dilution and exit temperature profile control of the combustion gases and for cooling of the combustor walls. The front of the combustor outer liner assembly is secured to the diffuser case outer wall by five combustion chamber retaining bolts. A seal is provided at the transition from the rear of the combustor outer liner to the turbine nozzle guide vanes. The rear of the combustor inner liner assembly is bolted to the stage 1 HP turbine blade cooling duct. The front lip of the combustor inner liner forms a seal with the inner diameter of the combustor hood.
The combustor is an annular type combustor which consists of an outer liner assembly and an inner liner assembly.
Each liner assembly is comprised of a liner shell and mechanically attached segments which form the inner wall of the combustion chamber. Air which surrounds the combustor is used in the combustion process for dilution and exit temperature profile control of the combustion gases and for cooling of the combustor walls. The front of the combustor outer liner assembly is secured to the diffuser case outer wall by five combustion chamber retaining bolts. A seal is provided at the transition from the rear of the combustor outer liner to the turbine nozzle guide vanes. The rear of the combustor inner liner assembly is bolted to the stage 1 HP turbine blade cooling duct. The front lip of the combustor inner liner forms a seal with the inner diameter of the combustor hood.
3. Turbine Nozzle Assembly
A. General
The stage on the turbine nozzle assembly consists of an outer ring, 40 cobalt alloy vanes, an inner combustor liner-assembly and the stage 1 HP turbine blade cooling duct assembly.
The vane pairs are retained at the outer end by a support ring which is bolted to the rear outer flange of the diffuser case. The outer ends of the vane pairs are retained such that the vanes may slide radially under thermal growth. Each vane is cooled by air which enters at the outer and inner ends and exits through airfoil holes into the primary gas path. The vanes are bolted to the 1 HP turbine blade cooling duct assembly at the inner end. the cooling duct directs and meters HP compressor air to the stage 1 HP turbine blades.
The stage on the turbine nozzle assembly consists of an outer ring, 40 cobalt alloy vanes, an inner combustor liner-assembly and the stage 1 HP turbine blade cooling duct assembly.
The vane pairs are retained at the outer end by a support ring which is bolted to the rear outer flange of the diffuser case. The outer ends of the vane pairs are retained such that the vanes may slide radially under thermal growth. Each vane is cooled by air which enters at the outer and inner ends and exits through airfoil holes into the primary gas path. The vanes are bolted to the 1 HP turbine blade cooling duct assembly at the inner end. the cooling duct directs and meters HP compressor air to the stage 1 HP turbine blades.
4. No.4 Bearing Compartment Assembly
A. General
The No. 4 bearing compartment consists of front and rear walls which attach to the No. 4 bearing support assembly. The bearing support assembly, in turn, is bolted to the diffuser case rear inner flange. The compartment walls are surrounded by a cooling duct which is itself insulated by a heatshield. The compartment walls also provide support for the carbon seals. The No. 4 bearing compartment service tubes connect to the front wall and supply the compartment with oil and cooling air. 12th stage compressor air is directed through an external air-to-air heat exchanger and carried by service tubes to the bearing compartment cooling duct. Discharge of this relatively cool air into the region of the carbon seals reduces ingestion of hot diffuser air into the bearing compartment. The No. 4 bearing is a roller bearing which is secured to the bearing support assembly by a ring nut and lock. Rotor support is transmitted through the bearing and bearing support to the diffuser case inner wall.
The No. 4 bearing compartment consists of front and rear walls which attach to the No. 4 bearing support assembly. The bearing support assembly, in turn, is bolted to the diffuser case rear inner flange. The compartment walls are surrounded by a cooling duct which is itself insulated by a heatshield. The compartment walls also provide support for the carbon seals. The No. 4 bearing compartment service tubes connect to the front wall and supply the compartment with oil and cooling air. 12th stage compressor air is directed through an external air-to-air heat exchanger and carried by service tubes to the bearing compartment cooling duct. Discharge of this relatively cool air into the region of the carbon seals reduces ingestion of hot diffuser air into the bearing compartment. The No. 4 bearing is a roller bearing which is secured to the bearing support assembly by a ring nut and lock. Rotor support is transmitted through the bearing and bearing support to the diffuser case inner wall.