DOC AIRBUS | AMM A320FTURBINE SECTION - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The turbine section consists of the HP and LP turbine modules.
The HP turbine uses combustion gases to drive the HP compressor and the accessory gearbox, and provides a gas stream to the LP turbine in order to drive the LP compressor and the fan through the LPT shaft.
** ON A/C NOT FOR ALL The turbine section consists of the HP and LP turbine modules.
Turbine Section AssemblyThe HP turbine uses combustion gases to drive the HP compressor and the accessory gearbox, and provides a gas stream to the LP turbine in order to drive the LP compressor and the fan through the LPT shaft.
2. HP Turbine Section
A. General
The HP Turbine Rotor and Stator Assembly provides the rotational driving force for the HP compressor and accessory gearbox by extracting energy from the hot combustion gases. It consists of a Stage 1 Turbine Rotor Assembly ; a HP Turbine Case and Vane Assembly ; a Stage 2 HPT Airseal ; and a Stage 2 Turbine Rotor Assembly.
The HP Turbine Rotor and Stator Assembly provides the rotational driving force for the HP compressor and accessory gearbox by extracting energy from the hot combustion gases. It consists of a Stage 1 Turbine Rotor Assembly ; a HP Turbine Case and Vane Assembly ; a Stage 2 HPT Airseal ; and a Stage 2 Turbine Rotor Assembly.
(1) Stage 1 turbine rotor assembly
The Stage 1 Turbine Rotor Assembly consists of a nickel alloy Stage 1 Turbine Hub, 64 air cooled nickel alloy, single crystal Stage 1 HPT Blades and the Stage 1 HPT Airseals (Inner and Outer). The stage 1 Turbine Rotor Assembly is splined to the HP compressor rear shaft. (Ref. 72-41-00). The blades fit into axial slots in the hub and are held in place at the front by the Stage 1 Airseal (Outer). This airseal is locked to the hub to prevent axial and circumferential movement. The rear of the blades is secured by 64 Stage 1 HPT Air Seals (Rear); each held in place by the Stage 2 HPT Airseal. The Stage 1 HPT Airseal (Inner) is located at front of the Stage 1 Turbine Hub and is held in place at the inner diameter by a tight fit at the front of the hub. The Stage 1 HPT Inner and Outer Airseals control leakage of Stage 1 HPT Blade cooling air from the cooling duct. (Ref. AMM D/O 72-40-00-00).
The Stage 1 Turbine Rotor Assembly consists of a nickel alloy Stage 1 Turbine Hub, 64 air cooled nickel alloy, single crystal Stage 1 HPT Blades and the Stage 1 HPT Airseals (Inner and Outer). The stage 1 Turbine Rotor Assembly is splined to the HP compressor rear shaft. (Ref. 72-41-00). The blades fit into axial slots in the hub and are held in place at the front by the Stage 1 Airseal (Outer). This airseal is locked to the hub to prevent axial and circumferential movement. The rear of the blades is secured by 64 Stage 1 HPT Air Seals (Rear); each held in place by the Stage 2 HPT Airseal. The Stage 1 HPT Airseal (Inner) is located at front of the Stage 1 Turbine Hub and is held in place at the inner diameter by a tight fit at the front of the hub. The Stage 1 HPT Inner and Outer Airseals control leakage of Stage 1 HPT Blade cooling air from the cooling duct. (Ref. AMM D/O 72-40-00-00).
(2) HP turbine case and vane assembly
The HP Turbine Case and Vane Assembly consists of a nickel alloy HP Turbine Case Assembly, 19 nickel alloy Stage 2 HPT Ring Segment and Vane Clusters (two vanes per cluster) and the Stage 1 and 2 HPT Duct Segments (19 each stage). Each vane cluster is attached to the HP Turbine Case Assembly at the outer diameter by tongue-and-groove joints. The 2nd Stage Vane Clusters consist of individual air cooled vanes which are paired by riveting one of the airseal ring segments of the Stage 2 Airseal to the inner diameter of the vanes. These airseal segments form the static part of the Stage 2 HPT Airseal which is used to control leakage past the Stage 2 Vane airfoils. The Stage 1 and 2 Duct Segments are held by tongue-and-groove joints to the HP Turbine Case, and Stage 2 HPT Ring Segment and Vane Clusters. Their construction provides a ceramic seal surface that is designed to wear away when contacted by the abrasive tips on the blades.
The HP Turbine Case and Vane Assembly consists of a nickel alloy HP Turbine Case Assembly, 19 nickel alloy Stage 2 HPT Ring Segment and Vane Clusters (two vanes per cluster) and the Stage 1 and 2 HPT Duct Segments (19 each stage). Each vane cluster is attached to the HP Turbine Case Assembly at the outer diameter by tongue-and-groove joints. The 2nd Stage Vane Clusters consist of individual air cooled vanes which are paired by riveting one of the airseal ring segments of the Stage 2 Airseal to the inner diameter of the vanes. These airseal segments form the static part of the Stage 2 HPT Airseal which is used to control leakage past the Stage 2 Vane airfoils. The Stage 1 and 2 Duct Segments are held by tongue-and-groove joints to the HP Turbine Case, and Stage 2 HPT Ring Segment and Vane Clusters. Their construction provides a ceramic seal surface that is designed to wear away when contacted by the abrasive tips on the blades.
(3) Stage 2 HPT air seal
The nickel alloy Stage 2 HPT Airseal is located between the Stage 1 and 2 Turbine Rotor Assemblies and is held in place by tight fitting diameters between the rotors. The Stage 2 Airseal also acts as a spacer for proper axial positioning of both rotors.
The nickel alloy Stage 2 HPT Airseal is located between the Stage 1 and 2 Turbine Rotor Assemblies and is held in place by tight fitting diameters between the rotors. The Stage 2 Airseal also acts as a spacer for proper axial positioning of both rotors.
(4) Stage 2 turbine rotor assembly
The stage 2 Turbine Rotor Assembly consists of a nickel alloy Stage 2 Turbine Hub, 72 air cooled nickel alloy, single crystal Stage 2 HPT Blades and a Stage 2 HPT Blade Retaining Plate. The Stage 2 Turbine Rotor Assembly is also splined to the HP compressor rear shaft.
The blades fit into axial slots and are held in place at the front by the rear of the Stage 2 HPT Airseal. They are retained at the rear by the Stage 2 HPT Blade Retaining Plate which is locked to the hub.
The stage 2 Turbine Rotor Assembly consists of a nickel alloy Stage 2 Turbine Hub, 72 air cooled nickel alloy, single crystal Stage 2 HPT Blades and a Stage 2 HPT Blade Retaining Plate. The Stage 2 Turbine Rotor Assembly is also splined to the HP compressor rear shaft.
The blades fit into axial slots and are held in place at the front by the rear of the Stage 2 HPT Airseal. They are retained at the rear by the Stage 2 HPT Blade Retaining Plate which is locked to the hub.
C. Cooling
All of the HPT airfoils are cooled by secondary air flow.
The first stage HPT blades are cooled by the HPC discharge air which flows through the first stage HPT duct assembly. The velocity of the air increases to the outside between the turbine front hub and the first stage HPT (front outer) air seal into the blade root, thus providing (once the speed is converted back into pressure) the pressure differential required to ensure cooling air flow.
The second stage vane clusters are cooled by tenth stage compressor air supplied externally. Air flows into the case and through the center of each vane and then outward into the turbine area and the gaspath. Some of this air is used for cooling of the second stage HPT air seal.
Second stage HPT blade cooling air is a mixture of HPC discharge air and tenth stage compressor air. This air moves through holes in the first stage HPT (front inner) air seal and the turbine front hub into the area between the hubs. The air then goes into the second blade root and out the cooling holes.
All of the HPT airfoils are cooled by secondary air flow.
The first stage HPT blades are cooled by the HPC discharge air which flows through the first stage HPT duct assembly. The velocity of the air increases to the outside between the turbine front hub and the first stage HPT (front outer) air seal into the blade root, thus providing (once the speed is converted back into pressure) the pressure differential required to ensure cooling air flow.
The second stage vane clusters are cooled by tenth stage compressor air supplied externally. Air flows into the case and through the center of each vane and then outward into the turbine area and the gaspath. Some of this air is used for cooling of the second stage HPT air seal.
Second stage HPT blade cooling air is a mixture of HPC discharge air and tenth stage compressor air. This air moves through holes in the first stage HPT (front inner) air seal and the turbine front hub into the area between the hubs. The air then goes into the second blade root and out the cooling holes.
D. Clearance Control
The abradable duct segments and abrasive blade tips, along with active clearance control, keep tight blade tip clearances for better performance.
The abrasive/abradable system makes tight clearances by letting the parts rub. The abrasive decreases blade tip wear during rub.
Active clearance control tubes around the turbine case supply fan discharge air to cool the surface of the case during climb and cruise-power operation.
Cooling results in shrinkage of the case and decreased blade tip clearances.
The abradable duct segments and abrasive blade tips, along with active clearance control, keep tight blade tip clearances for better performance.
The abrasive/abradable system makes tight clearances by letting the parts rub. The abrasive decreases blade tip wear during rub.
Active clearance control tubes around the turbine case supply fan discharge air to cool the surface of the case during climb and cruise-power operation.
Cooling results in shrinkage of the case and decreased blade tip clearances.
3. Low Pressure Turbine Section
A. General
The five stage Low Pressure Turbine (LPT) extracts energy from the gas stream delivered from the HP Turbine in order to provide a mechanical drive through the LPT shaft to the LP Compressor and the Fan. Exhaust gas from the LPT passes through a nozzle to provide propulsive thrust.
Seal clearance and LPT case heat expansion are controlled by an external Active Clearance Control (ACC) System. Fan discharge air is directed externally to the LPT case via the ACC tubes. This controls the heat expansion of the LPT case and optimizes the seal clearances.
The five stage Low Pressure Turbine (LPT) extracts energy from the gas stream delivered from the HP Turbine in order to provide a mechanical drive through the LPT shaft to the LP Compressor and the Fan. Exhaust gas from the LPT passes through a nozzle to provide propulsive thrust.
Seal clearance and LPT case heat expansion are controlled by an external Active Clearance Control (ACC) System. Fan discharge air is directed externally to the LPT case via the ACC tubes. This controls the heat expansion of the LPT case and optimizes the seal clearances.
(1) General
The LPT module is attached at the rear flange of the HP turbine module.
The five principal elements of the LP Turbine Module are:
The LPT module is attached at the rear flange of the HP turbine module.
The five principal elements of the LP Turbine Module are:
- LPT case, vanes and static seals,
- Five stage LPT rotor,
- LPT shaft,
- Turbine Exhaust Case (TEC) and No. 5 bearing assembly,
- Active Clearance Control System.
(2) LPT case, vanes and static seals
The LP Turbine case, stator vanes and seals are the static parts of the LP turbine assembly.
This assembly consists of five stages of vanes, static airseals, and diffuser inner and outer segments assembled in a casing.
The LP Turbine case is machined from six rolled rings circumferentially welded together.
It features rails on its inner wall surfaces for vane and seal hook attachments. The rails are scalloped to reduce weight and to improve response time to Active Clearance Control cooling.
The material of the LP turbine case is high heat resistant nickel alloy (INCO 718).
Two boroscope ports are provided at the left and right side of the LP turbine case. These ports enable inspection of LP Turbine rotor blades stage 3 and also HP Turbine rotor blades stage 2 through the stage 3 vane platform. Each port is sealed by a plug which incorporates features to prevent incorrect installation.
The LP Turbine stator vanes are made of nickel alloy and are brazed into clusters of three vanes each. Stages 3 to 5 have an aluminized coating, while stages 6 and 7 are uncoated. Stages 3, 4, 5 and 7 vane clusters are retained on hook attachments of the LPT case at the front of the outer platform and by the outer static seal segments at the rear of the outer platform. Stage 6 is retained similarly at the front and by the stage 7 vanes at the rear.
Vane segments of stages 3, 4 and 5 have slots at the inner and outer platform mating faces in which the sealing strips are located.
The outer static stages 3, 4, 5 and 7 rotor seals are separate seal segments with brazed in honeycombs installed in the LPT case. The honeycomb seal for the stage 6 rotor is brazed to the inner diameter of the stage 6 vane outer platform rear lip and the front lip of stage 7 vane.
The inner static interstage seals on stages 4 to 7 are abradable honeycomb segments which are brazed to the vane cluster inner platforms.
The stage 3 seals are separate honeycomb rings brazed on a nickel alloy ring which is bolted to the stage 3 vane clusters.
The diffuser duct inner segments are attached to the arrangement of stage 3 vane clusters.
All segments have a seal lip at the leading edge to provide a circumferential sealing of the potential leakage path between HP Turbine exit and LP Turbine inlet.
The diffuser duct outer segments are installed on hook attachments of the LP Turbine case inner wall. All diffuser segments have an aluminized coating.
An internal cooling air flow from the HP Turbine cooling system is supplied to the front section of the LP Turbine case inner wall hook attachments up to the outer static seal segments stage 3 where it exhausts into the gas stream.
The LP Turbine case, stator vanes and seals are the static parts of the LP turbine assembly.
This assembly consists of five stages of vanes, static airseals, and diffuser inner and outer segments assembled in a casing.
The LP Turbine case is machined from six rolled rings circumferentially welded together.
It features rails on its inner wall surfaces for vane and seal hook attachments. The rails are scalloped to reduce weight and to improve response time to Active Clearance Control cooling.
The material of the LP turbine case is high heat resistant nickel alloy (INCO 718).
Two boroscope ports are provided at the left and right side of the LP turbine case. These ports enable inspection of LP Turbine rotor blades stage 3 and also HP Turbine rotor blades stage 2 through the stage 3 vane platform. Each port is sealed by a plug which incorporates features to prevent incorrect installation.
The LP Turbine stator vanes are made of nickel alloy and are brazed into clusters of three vanes each. Stages 3 to 5 have an aluminized coating, while stages 6 and 7 are uncoated. Stages 3, 4, 5 and 7 vane clusters are retained on hook attachments of the LPT case at the front of the outer platform and by the outer static seal segments at the rear of the outer platform. Stage 6 is retained similarly at the front and by the stage 7 vanes at the rear.
Vane segments of stages 3, 4 and 5 have slots at the inner and outer platform mating faces in which the sealing strips are located.
The outer static stages 3, 4, 5 and 7 rotor seals are separate seal segments with brazed in honeycombs installed in the LPT case. The honeycomb seal for the stage 6 rotor is brazed to the inner diameter of the stage 6 vane outer platform rear lip and the front lip of stage 7 vane.
The inner static interstage seals on stages 4 to 7 are abradable honeycomb segments which are brazed to the vane cluster inner platforms.
The stage 3 seals are separate honeycomb rings brazed on a nickel alloy ring which is bolted to the stage 3 vane clusters.
The diffuser duct inner segments are attached to the arrangement of stage 3 vane clusters.
All segments have a seal lip at the leading edge to provide a circumferential sealing of the potential leakage path between HP Turbine exit and LP Turbine inlet.
The diffuser duct outer segments are installed on hook attachments of the LP Turbine case inner wall. All diffuser segments have an aluminized coating.
An internal cooling air flow from the HP Turbine cooling system is supplied to the front section of the LP Turbine case inner wall hook attachments up to the outer static seal segments stage 3 where it exhausts into the gas stream.
(3) Low Pressure Turbine rotor
The low pressure turbine rotor is a bolted configuration consisting of 5 disks and associated blades and rotating airseals. All these LPT rotor disks are manufactured of high heat resistant nickel alloy (INCO 718). The LP turbine shaft is bolted to the rotor at the stage 6 disk.
The axial positioning of the rotor drum is achieved by selection of an appropriate adjusting washer fitted between the LP Turbine shaft front end washer location and the LP Compressor stub shaft.
All rotating airseals are attached to the forward flange of the appropriate disk, and seal the potential leakage path between each rotor stage by means of coated seal fins which mate with the relevant static airseal.
The turbine blades are installed in fir tree type retaining slots. The blades are held in position on the disks by retention lugs on the blade root and the rear face of the rotating airseals. The LPT blades are solid and have inner and outer shrouds. The outer shroud seals of the LP turbine blades have interlocking notches to dampen vibration and prevent untwist. Over-tip leakage is minimized by two circumferential knife-edge seals which mate with the outer static airseals. The blades are made of nickel alloy. The stage 3 turbine blades have an aluminized coating ; the remaining turbine blades are uncoated.
The low pressure turbine rotor is a bolted configuration consisting of 5 disks and associated blades and rotating airseals. All these LPT rotor disks are manufactured of high heat resistant nickel alloy (INCO 718). The LP turbine shaft is bolted to the rotor at the stage 6 disk.
The axial positioning of the rotor drum is achieved by selection of an appropriate adjusting washer fitted between the LP Turbine shaft front end washer location and the LP Compressor stub shaft.
All rotating airseals are attached to the forward flange of the appropriate disk, and seal the potential leakage path between each rotor stage by means of coated seal fins which mate with the relevant static airseal.
The turbine blades are installed in fir tree type retaining slots. The blades are held in position on the disks by retention lugs on the blade root and the rear face of the rotating airseals. The LPT blades are solid and have inner and outer shrouds. The outer shroud seals of the LP turbine blades have interlocking notches to dampen vibration and prevent untwist. Over-tip leakage is minimized by two circumferential knife-edge seals which mate with the outer static airseals. The blades are made of nickel alloy. The stage 3 turbine blades have an aluminized coating ; the remaining turbine blades are uncoated.
(4) Low Pressure Turbine shaft
The Low Pressure Turbine Shaft joins the LP Turbine assembly with the LP Compressor and the Fan. The shaft is bolted to the LP turbine at the LPT rotor disk stage 6 and extends forward through the engine. On the front end, the shaft is attached to the Low Pressure Compressor rotor stub shaft by means of a spline coupling. The shaft is secured to the LP compressor stub shaft by the front lock nut. The LP Turbine shaft is supported at the rear end by the No. 5 bearing, which is located in the Exhaust Case and on the front end by the No. 2 bearing which is a part of the intermediate module.
The Low Pressure Turbine Shaft joins the LP Turbine assembly with the LP Compressor and the Fan. The shaft is bolted to the LP turbine at the LPT rotor disk stage 6 and extends forward through the engine. On the front end, the shaft is attached to the Low Pressure Compressor rotor stub shaft by means of a spline coupling. The shaft is secured to the LP compressor stub shaft by the front lock nut. The LP Turbine shaft is supported at the rear end by the No. 5 bearing, which is located in the Exhaust Case and on the front end by the No. 2 bearing which is a part of the intermediate module.
(5) Turbine Exhaust Case (TEC) and No. 5 bearing assembly
The Turbine Exhaust Case serves to straighten the turbine exhaust gases, provides structural support for the No. 5 bearing and incorporates the rear mount lugs. The struts incorporate provision to sense exhaust gas temperature and pressure.
The Turbine Exhaust Case is constructed of stainless steel (Greek Ascoloy) and is fabricated as a concentric inner cone and outer duct joined together by 13 welded radial struts. Thermal incompatibilities are minimized by matching the case thermal growth to that of the support struts.
The inner cone extension of the case provides support for the No. 5 bearing, with loads transmitted from the bearing through the struts to the outer case structure. Pressure and scavenge oil tubes for the No. 5 bearing are located within the case struts at the 4 and 8 o'clock locations respectively.
The No. 5 bearing compartment outer wall is an integral part of the Exhaust Case. It is sealed at the back by a cover and at the front by a plug in the LPT shaft. The compartment is sealed from the LP Turbine cavity air by a two element radial carbon seal. The carbon elements are contained in a housing assembly and seal against the No. 5 bearing compartment outer wall and the seal housing walls. The outer walls and cap are fully insulated thermally to minimize compartment temperature.
The No. 5 bearing inner race is secured on the shaft by an interference fit and is secured against the seal assembly by a coupling nut. The outer race which has shoulders to guide the rollers is loosely fitted in the bore of the bearing support. Pressurized oil is supplied between the support and the bearing outer race, and with tight control of shoulder tolerance, forms the damper squeeze film.
Oil enters the No. 5 bearing compartment through a tube within the exhaust case strut at the 4 o'clock location and into a nozzle attached to the compartment wall. The nozzle directs a jet of oil into a passage to feed the squeeze film damper described above. The nozzle directs a second jet of oil to lubricate the bearing rollers through holes in the LPT shaft and internal passages in the bearing inner race.
Oil is scavenged through a tube from the bottom of the compartment through the strut at the 8 o'clock location to the scavenge pump. This line is insulated within the TEC. Venting of this compartment is not necessary.
The Turbine Exhaust Case serves to straighten the turbine exhaust gases, provides structural support for the No. 5 bearing and incorporates the rear mount lugs. The struts incorporate provision to sense exhaust gas temperature and pressure.
The Turbine Exhaust Case is constructed of stainless steel (Greek Ascoloy) and is fabricated as a concentric inner cone and outer duct joined together by 13 welded radial struts. Thermal incompatibilities are minimized by matching the case thermal growth to that of the support struts.
The inner cone extension of the case provides support for the No. 5 bearing, with loads transmitted from the bearing through the struts to the outer case structure. Pressure and scavenge oil tubes for the No. 5 bearing are located within the case struts at the 4 and 8 o'clock locations respectively.
The No. 5 bearing compartment outer wall is an integral part of the Exhaust Case. It is sealed at the back by a cover and at the front by a plug in the LPT shaft. The compartment is sealed from the LP Turbine cavity air by a two element radial carbon seal. The carbon elements are contained in a housing assembly and seal against the No. 5 bearing compartment outer wall and the seal housing walls. The outer walls and cap are fully insulated thermally to minimize compartment temperature.
The No. 5 bearing inner race is secured on the shaft by an interference fit and is secured against the seal assembly by a coupling nut. The outer race which has shoulders to guide the rollers is loosely fitted in the bore of the bearing support. Pressurized oil is supplied between the support and the bearing outer race, and with tight control of shoulder tolerance, forms the damper squeeze film.
Oil enters the No. 5 bearing compartment through a tube within the exhaust case strut at the 4 o'clock location and into a nozzle attached to the compartment wall. The nozzle directs a jet of oil into a passage to feed the squeeze film damper described above. The nozzle directs a second jet of oil to lubricate the bearing rollers through holes in the LPT shaft and internal passages in the bearing inner race.
Oil is scavenged through a tube from the bottom of the compartment through the strut at the 8 o'clock location to the scavenge pump. This line is insulated within the TEC. Venting of this compartment is not necessary.
C. Active Clearance Control System
The ACC system uses air to control the tip clearances of the LP turbine blades.
The ACC system uses air to control the tip clearances of the LP turbine blades.