1.7.2 System Components Description-9HA GT Inlet Air System

2.0 System Component Description

2.1 Filtration

Insect screen : made of steel/steel panels which have to be removed for winter season, avoid mosquitos to reach filtration stages ad to quickly clogged them.

Weather Hoods: Six hoods protect the filter housing intake. Each hood is made of a painted carbonn steel sub structure covered by cladding sheets. Lifting lugs and water draining gutter and pipes are fitted with each hood.

Coalescer Stage: Composed of an arrangement of support holding frames. AISI type 304L, fitted with water draining gutters and pipes. This frames support the 576 coalescer panels made of fiberglass fiber packaged in a plastic frame used for water droplet removal.

Pre Filter and High Efficiency Filter (HEF) Stage: Composed of a V shape support holding frame arrangement, made of AISI 304L. Each horizontal row of holding frames is inclined of 10 degree to evacuate water captured in the filter elements. Gutters and drain pipes enable water draining outside of the filter housing. Holding frame arrangement is designed to support 512 pocket type pre filters and 512 HEF cells. Pre filters are reverse installed against the front face of HEF cells and maintained by a stainless steel wires basket. Pre Filters efficiency class G4 (EN779) are made of synthetic fibers, a plastic header fitted with a gasket for sealing when installed against HEF. HEF efficiency class F9 are of made of fiber glass media, a plastic frame fitted with a gasket for sealing when installed in the support frame.

2.2 Closing Flap

Enable to close and to isolate the inlet air path from the cold ambient conditions during GT stop periods.

2.3 Anti Icing / Heater

Water/Air heat exchanger is used to prevent frost or ice forming on the filtration stages and other stiffeners, silencer baffles are located int he air path during icing events. Exchanger system is also used to heat ambient air, to follow the minimum air temperature(-29 degree Celsius) admissible at compressor intake (heater function).

2.4 Bleed Heating

Hot air extracted from the GT compressor when required by the bleed heating function (guarantee of NOx emission, protect IGV against icing) is dispatched in the filter housing by the bleed heating(IBH) manifold. The IBH manifold is composed stainless steel acoustical nozzlws through the filter housing air path.

2.5 Implosion Doors

Implosion door equipped with electro magnetsm limit swictches, heating gaskets open (2300 Pa) to prevent from inlet system implosion in case of high high pressure drop level reached during shutdown period.

2.6 Inlet Duct and Silencer

Inlet duct and silencer system is composed of one Elbow, one silencer section, one extraction joint and one support structure.
The elbow and the silencer duct structure are made of stiffened carbon steel sheets protected against corrosion by a painting system.
Noise reduction is achieved by an arrangement of parabllel baffles, Baffles are made of stainless steel type AISI 304L structure and perforated sheets which protect the acoustic cushions made of mineral wool and fiber glass fabric.
As additional acoustic treatment, inlet duct walls are externally insulated with mineral wool and cladding.

2.7 Inlet Plenum

Inlet plenum is composed of a casing structure in several parts; a cone, a support structure. Casing structure and cone are made of stiffened carbon steel protected against corrosion by a painting system.
The plenum is fitted with pressure, temperature and dew point measurement connections. A drain connection located in the plenum floor enables washing water evacuation.

1.7.1 Gas Turbine 9HA Air Inlet System

1.0   System Description

1.1    Main Function

The main function of the system are:

·         To remove water and dust particles from the atmosphere air sucked by the gas turbine compressor(air filter housing)

·         To covey filtered air towards the inlet plenum and to reduce gas turbine compressor noise(inlet duct and silencer).

·         To collect and distribute filtered air to the GT compressor intake.

 The inlet & exhaust system is an open loop where:

·         The air filter housing function is the removal of contaminants from the ambient air sucked by the FT compressor. Clean air is required by the combustion, the hot parts s cooling air system and to avoid corrosion, erosion and fouling of mechanical components such as compressor sand turbine blades.

·         Insects screen enables to catch big amount of insect which could clogged very quickly the pre filters stages, and so avoid frequent maintenance of pre filtration stages.

·         Inlet weather hoods and coalesce stage are used to remove water droplets. Dust Particles are removed by pre filter and high efficiency filtration cells.

·         A closing flab enables inlet system closing in case of long FT stop period to avoid very cold air circulation through compressor and Gas turbine.

·         Anti-icing protection of the inlet system components is ensured by a water/air heat exchanger. Exchanger also enables to guarantee the minimum ambient air temperature (-29 C) required at the compressor.

·         A bleeding heating manifold with acoustical nozzles dispatches air extracted from compressor in GT part load, to protect IGV stages from icing and to respect Nox level.

·         The mechanical security of the inlet system ducting and housing is insured by pressure drop monitoring which controls a GT Run Back in case of high pressure drop level reached and by implosion doors’ opening.

·         The air inlet duct system including the inlet silencer is used to convey atmospheric filtered air towards the inlet plenum. Inlet silencer enables to attenuate noise generated by the GT compressor.

·         The inlet plenum collects the atmospheric air and allow the inlet compressor feeding with a homogeneous distribution.

1.2    Components of Air intake System.

GE Code	Function
Weather Hoods	Protect filter housing against rain water from entering into the intake system.
Closing Flap	Close inlet system to avoid cold air circulation during GT stop period.
Water/Air Heat Exchanger	Operates as Anti icing system to protect filters against frost and as heater to guarantee min. required Temp. At compressor inlet.
AIBH manifold	Dispatch air extracted from GT compressor in the inlet system to cover the BH functions.
Pre filter and high efficiency stage	Remove dust particles from ambient air sucked by GT compressor.
Inlet silencer	Drive filtered ambient air towards the inlet plenum. Reduce noise coming from GT compressor.
Inlet plenum	Collect and distribute air to the GT compressor intake (IGV).

 

1.6.0 GT 9HA Bearings

General

The 9HA.01 gas turbine unit has two double tilting pad journal bearings which support the gas turbine rotor and two self-equalizing tilting pad thrust bearings to maintain the rotor-to-stator axial position. These bearings are incorporated in the inlet casing and exhaust frame which are supplied oil from the main lubricating oil system.

Lubrication

The main turbine bearings are pressure-lubricated with oil supplied, from the oil reservoir. Oil feed piping where practical, is run within the lube oil drain lines, or drain channels, as a protective measure. In the event of a supply line leak, oil will not be sprayed on nearby equipment, thus eliminating a potential safety hazard.

The oil flows through branch lines to an inlet in each bearing housing. When the oil enters the housing inlet, flows into an annulus around the bearing. From the annulus, the oil flows through machined holes or slots to the bearing rotor interface.

Lubricant Sealing

Oil on the surface of the turbine shaft is prevented from being spun along the shaft by oil seals in each of the bearing housings. These labyrinth seals are assembled at the extremities of the bearing assemblies where oil control is required. A smooth surface is machined on the shaft and the seals are assembled so that only a small clearance exists between the oil seals and the shaft. The oil seals are designed with tandem rows of teeth and an annular space between them. Pressurized sealing air is admitted into this space to prevent lubrication oil reservoir is vented to atmosphere after passing through an oil vapor extractor.

Load Coupling

A rigid, hollow coupling connects the forward compressor rotor shaft to the generator. A bolted flange connection forms the joint at each end of the coupling.

1.5.0 Turbine Section (GE 9HA Details)

Turbine

5.1 Turbine Section

The turbine section is the area in which energy in the form of high temperature pressurized gas, produced by the compressor and combustion sections, is converted to mechanical energy. The 4^th stage axial flow turbine consist of the rotor, casing, exhaust frame, exhaust diffuser, buckets, nozzles and shrouds.

5.2 Turbine Rotor

A) Structure

The turbine rotor assembly consists of the aft turbine shaft, the first-, second-, third-, and fourth-stage turbine wheel assemblies with spacers and turbine buckets.

Concentricity control is achieved with mating rabbets on the turbine wheels, wheel shaft, and spacers. The wheels, spacers and aft shaft are held together with 5 sets of bolts that pass through each of the wheels and mating up with bolting flanges on the shafts and spacers. Selective positioning of rotor members is performed to improve balance the assembly.

B) Wheel Shafts

The aft shaft of the turbine rotor includes the NO.2 bearing journal.

C) Wheel assemblies

Spacers between the first and second, the second and third and between the third and fourth-stage turbine wheels determine the axial position of the individual wheels. These spacers carry the flow path seals. Near flow path seals are attached to the spacers using circumferential dovetails and serve to protect the rotor surface from hot gas path temperatures. The 1-2 spacers forward and aft faces include radial slots for cooling air passages.

Turbine buckets are assembled in the wheels with fir-tree-shaped dovetails that fit into matching cut-outs in the turbine wheel rims. All three turbine stage buckets are precision investment-cast. The shank on these buckets effectively shields the wheel rims and bucket dovetails from the hot gas path temperatures while mechanically damping bucket vibrations. Stage three and four buckets are further aided in damping vibration with interlocking shrouds at the buckets tips. These shrouds increase the turbine efficiency by minimizing tip leakage. Radial teeth located on the bucket shrouds mate with stepped surfaces on the stator hardware create labyrinth seals against gas path leakage around the bucket tips.

The increase in size of the buckets from the first to the fourth stage is necessitated by the pressure reduction resulting from energy conversion in each stage, requiring an increased annulus area to accommodate the gas flow.

D) Cooling

The turbine rotor is cooled to maintain reasonable operating temperatures and, therefore, assure a longer turbine service life. Cooling is accomplished by means of a positive flow of cool air extracted from the compressor and discharged radially outward through a space between turbine wheel and the stator, into the main gas stream. This area is called wheelspace.

E) Wheel space

Each turbine wheel has a forward and aft wheelspace that needs to be purged to prevent the hot gas air path from permeating these cavities. By maintaining these cavities purged, the integrity of the turbine structure will be maintained.

The first-stage forward wheelspace is cooled by compressor discharge air. An inducer at the inner flowpath efficiently pre-swirls the extraction air, which is then passed through holes in the midshaft and 0-stage spacer. Inducer air then flows through the first-stage forward wheelspace and is routed through the first stage bucket, is discharged into the main gas stream aft of the first-stage nozzle.

All other wheelspaces are purges with 10^th stage compressor extraction air (taken form the inner diameter flowpath at stage10), which flows through the rotor bore, up through passages in the turbine wheels, and into the turbine flow path.

5.3 Buckets

Air is introduced into each first-stage and second-stage bucket through a plenum at the base of the bucket dovetail. it flow through precision cast serpentine passages and is introduced into the flow path through a series of cooling holes on the airfoil surface, tip and trailing edge.

Unlike the first-stage buckets, the third-stage buckets are cooled with machined internal air passages that travel the entire length of the foil. This cooling air enters cavity in tip shroud before exiting into the main gas stream. Air is introduced, like the first and second-stage, with a plenum at the base of the bucket dovetail.

The holes in the first, second, and third stage buckets are spaced and sized to obtain optimum bucket cooling while minimizing the compressor extraction air.

The Fourth-stage buckets are not internally air cooled. The tips of these buckets, like third stage buckets, are enclosed with interlocking by tip shrouds that are designed to minimize tip leakage and dampen the mechanical vibration of these long arifoils.

5.4 Near Flow path seals

a. Near flow path seals are installed using dovetail mounting in the 1-2, 2-3, and 3-4 spacer. These replaceable seals provide protect the turbine rotor wheelspaces from hot gas path temperature. Sealing teeth on this part mate with honeycomb attached to the power nozzles to isolate turbine stages.

5.5 Structure

The casing area of the turbine section is composed of six major elements. These are the:

a.       Inner turbine shell

b.      Outer turbine shell

c.       Nozzles

d.      Diaphragms

e.      Shrouds

f.        Exhaust Frame

The Inner turbine shell makes up a portion of the gas path annulus and supports the power nozzle assemblies and shrouds. The inner turbine shell is encased and supported by the outer turbine shell. The outer turbine shell also provides a pressure barrier structural strength to the gas turbine. Cooling air extracted from the compressor flows to static hot gas path components though the outer turbine shell. The inner turbine shell is allowed to ‘float ‘slightly within outer turbine shell for improved performance from bucket tip clearance control. The inner and outer turbine shells are split horizontally to provide access for servicing internal components

The exhaust frame supports the rotor at the aft bearing, makes up the outer wall of the gas-path annulus, and supports the exhaust diffuser. It is split horizontally to facilitate servicing.

           

      Inner Turbine Shell

The inner turbine shell controls the axial and radial positions of the shrouds and nozzles. It determines turbine clearances and the relative positions of the nozzles to the turbine buckets. This positioning is critical to gas turbine performance.

The inner turbine shell is cooled during operation by air flowing from the 8^th and 11^th stage compressor extraction air. After cooling the inner turbine shell, 8^th and 11^th stage air is directed to the third and second-stage nozzles respectively for cooling.

The center-line of the inner turbine shell is aligned to the rotor center-line during assembly and is supported by ledges in the outer turbine shell.

   

       Outer Turbine Shell

The outer turbine shell is bolted to and aft end of the compressor discharge casing. It supports the inner turbine shell, provides structural strength to the gas turbine, makes up the outer pressure boundary, and provides a connection point for compressor extraction piping.

 Nozzles

In the turbine section there are four stages of stationary nozzles which direct the high-velocity flow of the expanded hot combustion gas against the turbine buckets causing the turbine rotor to rotate. Because of the high pressure drop across these nozzles, there are seals at both the inside and the outside diameters to prevent loss of system energy by leakages. Since these nozzles operate in the hot combustion gas flow, they are subjected to thermal stresses in addition to gas pressure loading.

       First-Stage Nozzle

    The first-nozzle receives the hot combustion gases from the combustion system via the transition pieces. The transition pieces are sealed to both the outer and inner sidewalls on the entrance side of the nozzle.

      The 9HA.01 gas turbine first-stage nozzle contains a forward and aft cavity in the vane and is cooled by a combination of film, impingement and convection techinques in both the vane and sidewall regions.

      The nozzle segments, each with a single airfoil, are supported at the inner diameter by a horizontally split retaining ring which is supported by the aft end of the compressor discharge casing. They are supported at the outer diameter by the first stage shroud.

    Second-Stage Nozzle

    Air exiting from the first stage buckets is again expanded and redirected against the second-stage turbine buckets by the second-stage nozzle. This nozzle is made of cast segments, each with two airfoil. The male hooks on the entrance and exit sides of the outer sidewall fit into female grooves on the aft side of the first-stage shrouds and on the forward side of the second-stage shrouds to maintain the nozzle concentric with the turbine shell and rotor. This close fitting tongue-and-groove fit between nozzle and shrouds acts as an outside diameter air seal. The second-stage nozzle is cooled with 11^th stage extraction air.

        Third-Stage Nozzle

     The third-stage nozzle receives the hot gases as it leaves the second-stage buckets, increase its velocity by pressure drop, and directs this flow against the third-stage buckets. The nozzle consists of cast segments, each with one airfoil. It is held at the outer sidewall forward and aft sides in grooves in the turbine shrouds in a manner similar to that used on the second-stage nozzle. The third stage nozzle is cooled by 8^th stage compressor extraction air.

       Fourth-Stage Nozzle

      The fourth-stage nozzle receives the hot gas as it leaves the third-stage buckets, increases its velocity by pressure drop, direct this flow against the fourth-stage buckets. The nozzle consists of cast segments, each with three airfoils. It is held at the outer sidewall forward and aft sides in grooves in the turbine shrouds in a manner similar to that used on the second-stage nozzle. The fourth-stage nozzle is uncooled.

    Diaphragm

Attached to the inside diameter of the second third, and fourth –stage nozzle segments are the nozzle diaphragms. These diaphragms deter air leakage past the inner sideall of the nozzles and the turbine rotor The high/low, labyrinth seal teeth are machined into the inside diameter of the diaphragm. They mate with opposing sealing lands on the turbine rotor. Minimal radial clearances between stationary parts (diaphragms and nozzles) and the moving rotor are essential for maintaining low inter-stage leakage, this result in higher turbine efficiency.

   Shrouds

Unlike the compressor blading, the turbine buckets tips do not run directly against an integral machined surface of the casing but against thin walled segments mounted female grooves located in the turbine shell. The shrouds primary function is to provide a cylindrical surface to minimize bucket tip clearance leakage.

The turbine shrouds’ secondary function is to provide a high thermal resistance between the hot gases and the comparatively cool turbine casing. By accomplishing this function, the turbine casing cooling load is drastically reduced, the turbine casing diameter is controlled, the turbine casing roundness is maintained, and important turbine clearances are assured.

The first stage stationary shroud segments are in low pieces. The gas-side inner shrouds is separated from the supporting outer shroud to allow for expansion and contraction and thereby improve low-cycle fatigue life. The inner shroud is cooled b impingement, film, and convection.

He shroud segment are maintained in the circumferential position by radial pins from the inner turbine shell. Joints between shroud segments are sealed by fixable metal seals.

  Exhaust Frame

Gases exhausted from the fourth turbine stage enter the diffuser where velocity is reduced by diffusion and pressure is recovered. The exhaust frame is bolted to the aft end of the turbine casing. Structurally, the frame consists of an outer cylinder and an inner cylinder interconnected by the radial struts. The No. 2 bearing is supported from the inner cylinder.

Exhaust frame radial struts cross the exhaust gas stream. These Struts position the inner cylinder and No. 2 bearing in relation to the outer casing of the gas turbine. The struts must be maintained at a constant temperature in order to control the center position of the rotor in relation to the stator. This temperature stabilization is accomplished by protecting the struts from exhaust gas with an airfoil shaped metal firing that forms an air space around each strut. Off-base blowers provide cooling air flow through the No. 2 bearing tunnel and then to the fourth-stage aft wheelspace and air space of the struts.

Removable trunnions on the sides of the exhaust frame are used with similar trunnions on the inlet casing to lift the gas turbine when it is separated from its base.

The exhaust diffuser located at the aft end of the turbine is bolted to the exhaust frame. At the exit of the diffuser, the gases are directed into the exhaust plenum.

 .

1.4.0 DLN-2.6 + Combustion System

4.0 DLN-2.6 + Combustion System

The combustion system is a reverse-flow design with 16 combustion chambers arranged around the periphery of the compressor discharge casing. Combustion chambers are numbered counter-clockwise starting with the chamber just left of the chamber at top dead center when looking aft end. This system also includes the fuel nozzles, a spark plug ignition system, flame detectors, and crossfire tubes.

High pressure air from the compressor discharge is directed around the aft end of the transition piece. Most of the compressor discharge air enters the holes in the aft end of the transition piece to cool the transition piece and for annulus between the flow sleeve and liner, through holes in the aft end of the flow sleeve. This air passes through the quaternary fuel ring and then enters the combustion zone through the cap assembly for proper fuel combustion. Fuel is supplied to each combustion chamber through six nozzles designed to disperse and mix the fuel with the proper amount of combustion air (and to the quaternary ring at during baseload operation). Hot gases, generated from burning fuel in the combustion chambers, flow through the impingement cooled flow sleeve and transition piece to the turbine.

4.1 Combustor Configurations for Fuel Type:

Dual Fuel
This configuration is capable of operation on either natural gas or liquid fuel. The fuel type can be changed gas to liquid to gas while the GT is operating.

Gas Fuel Only
The fuel nozzles feed only natural gas to the combustion system, with no provision for liquid fuel operation.

Liquid fuel only
The fuel nozzles feed only liquid fuel and water into the combustion system, with no provision for gas fuel.

·         On gas fuel, the combustor operates on 6 fuel nozzles per combustor, where the number of fuel nozzles fueled increases as the GT load increases. One nozzle is fueled from FSNL to low load; three nozzles are fueled from low load to intermediate load; and six nozzles are fueled plus the quaternary fuel circuit from intermediate load to baseload. Emissions complaint operation required all fuel circuit to be fueled and GT firing temperature to be above a threshold temperature.

·         On oil operation, this combustor operated in diffusion amide across the entire load range, with only the outer 5 fuel nozzles fueled. Water injection is also injected by the fuel nozzles into the combustor for NOx reduction.

4.3 Outer Combustion chambers and Flow Sleeves

The outer combustion chamber, or casing, acts as the pressure vessel for the combustor. They also provide flanges for the fuel nozzle-end cover assemblies, crossfire tube flanges, spark plugs, flame detectors and false start drains. The flow sleeve forms an annular space around the cap and transition piece assemblies that directs the combustion and cooling into the forward end of the combustor fuel nozzle jet.

4.4 Cap, Flow Sleeve, and Transition Piece Assemblies

The combustion flow sleeves and transition pieces are passively cooled on their outside with air directed by the impingement sleeve to the forward end of the combustor and fuel nozzle inlet. Ridges on the liner outer surface augment the cooling effectiveness. The inner surfaces of the transition piece and flow sleeve have thermal barrier coating to reduce metal temperatures and thermal gradients. The aft end of the transition piece transforms the combustor annular flow into  flow profile to be fed into the Stage 1 Turbine Nozzle. The Cap has six burner tubes that engages each of the six fuel nozzles. The cap is cooled by effusion cooling passages.

4.5 Fuel Nozzle End Covers

There are six fuel nozzles assemblies in each combustor. They arranged with 1 located in the center and five arranged around the outer edge. Each fuel nozzle premixes the inlet air and gas fuel, and then forwards this mixture to the combustor reaction zone for burning. The outer fuel nozzles contain a liquid fuel and water passage down the center of the fuel nozzle for operation on oil, where oil and water is injected directly into the combustor. Water is injected into the reaction zone when the combustor is to be operated within emissions compliance on oil fuel.

4.6 Quaternary Fuel Ring

Each combustion chamber contain a Quaternary fuel ring located between the combustion casing and the CDC. Fuel is instructed at intermediate load and above.

4.7 Crossfire Tubes

All combustion chambers are interconnected by crossfire tubes to provide means for ignition of the chambers without ignitors. The outer chambers are connected with an outer crossfire tube and the combustion liners are connected by the inner crossfire tubes.

4.8 Spark Plugs

The combustor is ignited with two spark plugs that are positioned within the combustor downstream of a fuel nozzle. Once the combustor is ignited, the pressure from the combustor forces the ignitor tip to retract from the combustor for continous operation. These spark plugs receive their energy from high energy-capacitor discharge power supplies. Once the combustor chamber is ignited with the spark plug, the remaining chambers are ignited by the flame passing through the crossfire tubes that interconnect the reaction zone of the remaining chambers.

4.3 Flame Detectors

A flame monitoring system is used consisting of 4 flame detectors. The signals from the flame detectors are sent to the control system which uses an internal logic system to confirm whether the combustors are ignited or extinguished.

 

 

1.3.2-GE 9 HA Compressor and Turbine Design

3.3 Casings of Compressor

The casing area of the compressor section is composed of three major sections. These are the:

·         Inlet casing

·         Compressor casing

·         Compressor discharge casing

These casings, in conjunction with the turbine casing, form the primary structure of the gas turbine. they support the rotor at the bearing points and constitute the outer wall of the gas path annulus. All of these casings are split horizontally to facilitate servicing.

3.3.1 Inlet Casing

The inlet casing is located at the forward end of the gas turbine. its primary function is to uniformly direct air into the compressor. the inlet casing also support the No.1 bearing assembly. The No.1 bearing assembly housing is a separate component assembled into the inner bellmouth. The upper half bearing housing is flanged and bolted to the lower half bearing housing. The inner bellmouth is positioned to the outer bellmouth by nine air foil-shaped radial struts. The struts are cast into the support which is bolted and doweled to this inlet casing.

The inlet casing lower half is equipped with two large integrally cast trunnions which are used to lift the gas turbine.

Variable inlet guide vanes (VIGV) are located at the aft end of the inlet casing and are mechanically positioned, by a control ring and vane arm arrangement connected to an actuator drive and linkage arm assembly. The position of these vanes has a effect on the quantity of compressor inlet air flow.

3.3.2 Compressor Casing

The compressor casing contains the variable stator vane stage 1 through stage 3 and the fixed stator stage 4 through stage 8. Each stage of variable stator vanes is mechanically positioned, by a control ring and vane arm arrangement connected to an actuator drive through a torque tube and linkage arm assembly. The positioned of these vanes has an effect on the quantity and efficiency of the compressor air flow.

The aft end of the compressor casing contains extraction ports to permit removal of 8^th stage compressor air. This bleed air is used for turbine static hardware cooling functions and is also used for pulsation control during start up and shutdown.

3.3.3 Compressor Discharge Casing

The compressor discharge casing (CDC) is the final portion of the compressor section and is the longest single casting. The CDC is situated at the gas turbine midpoint, between the forward and aft supports, and is, in fact, is the keystone of the gas turbine structure. the CDC contains the final compressor stages 9-14, and contains extraction ports to permit removal of 11^th stage compressor air used for turbine static hardware cooling functions.

The CDC and its components form the flow path surfaces of the compressor diffuser, and join the compressor and turbine casings. The CDC also provides support for the combustion casings, transition piece support bracket and the inner support of the first stage turbine nozzle.

The compressor discharge casing consists of two cylinders, one being a continuation of the compressor and the being an inner cylinder that surrounds the compressor rotor. The two cylinders are concentrically positioned by twelve radial struts.

A dual-path diffuser is formed by the tapered annulus between the outer cylinder and inner cylinder of the discharge casing and a third member which splits the compressor flow into two steams. The diffuser converts some of the compressor exit velocity into added static pressure for the combustion air supply.

3.3.4 Blading

The compressor rotor and stator blades are air foil shaped and designed to compress air efficiently at the high blade tip velocities. The blades are attached to the compressor wheels by dovetail arrangements. The dovetails are very precise in size and position to maintain each blade in the desired position and location on the wheel.
The compressor stator blades are air foil shaped and are mounted by similar dovetails into ring segments stage 4 through stage 14 stage 14 and exit guided vane. The ring segments are inserted into circumferential grooves in the casing and are held in place with locking keys. The variable inlet guide vane and variable stator vanes stage 1 through stage 3 are mounted through Trunnion holes in the casing walls and secured with a vane arm and nut assembly.

1.3.1-GE 9 HA Compressor and Turbine Design

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GE 9 HA Compressor and Turbine Design

1.0  Introduction

1.1 General

The 9HA is a single-shaft gas turbine designed for operation as simple cycle unit or in a combined steam and gas turbine cycle. The gas turbine assembly contains six major section or groups

1. Air Inlet
2. Compressor
3. Combustion system
4. Turbine
5.  Exhaust gas system
6.   Support systems

This section briefly describes how the gas turbine operates and the interrelationship of the major components.

1.2 Gas Path Description

The gas path is the path by which gases flow through the gas turbine from the air inlet through the compressor, combustion section and turbine, to the turbine exhaust.

When the turbine starting system is actuated, ambient air is drawn through the air inlet plenum assembly, filtered and compressed in the multi-stage, axial-flow compressor. For pulsation protection during startup, compressor bleed valves are open and the variable inlet guide vanes (VIGV) and variable stator vanes (VSV) are in the closed position. When the high-speed relay actuates, the bleed valves begin operation automatically and VIGV and VSV actuators energize to position the VIGV and VSV for normal Turbine operation. Compressed air from the compressor flows into the e spaces between the outer combustion casing and the combustion liners and enters the combustion zone through metering holes in each of the combustion liners.

Fuel from an off-base source is provided to flow lines each terminating at the primary and secondary fuel nozzles in the end cover of the separate combustion chambers.

Options:

On liquid fuel machines, the fuel s controlled prior to being distributed to the nozzles to provide an equal flow into each liquid fuel distributor valve mounted on each end cover and each liquid fuel line on each secondary nozzle assembly.

On gas-fuel machines the fuel nozzles are the metering orifices which provide the proper flow into the combustion zones in the chambers.

The nozzles introduce the fuel into the combustion zone within each chamber where it mixes with the combustion air and is ignited by one or more of the spark plugs. At the instant when fuel is ignited in the one combustion chamber flame is propagated, through connecting crossfire tubes, to all other combustion chambers where it is detected by four primary flame detectors, each mounted on a flange provided on the combustion casings.

The combustion hot gases flow through the flow sleeves and transition pieces and into the four-stage turbine section. Each stage consists of a row of fixed nozzles and a row of turbine buckets.

In each nozzle row, the kinetic energy of the jet is increased, with an associated pressure drop, which is absorbed as useful work by the turbine rotor buckets, resulting in shaft rotation used to turn the compressor and generator rotor to generate electrical power.

After passing through the fourth-stage buckets, the gases are directed into the exhaust diffuser. The gases then pass into the exhaust plenum and are introduced to atmosphere through the exhaust stack or go to HRSG in combined cycle mode.

2.0 Base and Supports

2.1   Turbine Base

The base that support the gas turbine is a structural steel fabrication of welded steel beams and plate. Its prime function is to provide a support upon which to mount the gas turbine.

Lifting trunnions and support are provided, two on each side of the base in line with the two structural cross members of the base frame. Machines pads on each side on the bottom of the base facilitate its mounting to the site foundation. Two machines pads, atop the base frame are provided for mounting the aft supports

2.2   Turbine Supports

 The 9HA.01 has rigid leg-type supports at the compressor end and supports with top and bottom pivots at the turbine end. The support legs maintain the axial and vertical positions of the turbine, whole two gib keys coupled with the turbine supports legs maintain its lateral position. One gib key is machined o the lower half of with exhaust frame. The other gib key is machined on the lower half of the compressor inlet casing. The key fit into guide block which are welded to the cross beams of the turbine base. The keys are held securely in place in the guide blocks with bolts that bear against the keys on each side. The key-and-block arrangement prevents lateral or rotational movements of the turbine while permitting axial and radial movement resulting from thermal expansion.

3.0 Compressor Section

3.1 General

The axial-flow compressor section consists of the compressor rotor and the compressor casing. Within the compressor casing are the variable inlet guide vanes, the variable stator vanes, the various stages of rotor and stator blading, the exit guide vanes and the compressor exit diffuser.

In the compressor, air is confined to the space between the rotor and stator where it is compressed in stages by a series of alternate rotating (rotor) and stationary (stator) air-foil-shaped blades. The rotor blades supply the force needed to compress the air in each stage and the stator blades guide the air so that it enters the following rotor stage at the proper angle. The compressed air exits through the compressor discharge casing to the combustion chambers. Air is extracted from the compressor for turbine cooling and for pulsation control during startup.

3.2 Rotor

The compressor portion of the gas turbine is an assembly of wheels, a speed ring, a forward stub shaft (FSS), Tie bolts, the compressor rotor blades, and a mid-shaft.

The first three wheels have slots broached around their periphery. The rotor blades and spacers are inserted into these slots and held in axial position by a ring on the forward side of each wheel. Wheels stages 4 through stage 14 have a circumferential position using blade-locks positioned at several circumferential locations on each wheel. The wheels are assembled to each other with mating rabbets for concentricity control and are held together with tie bolts. Selective positioning of the wheels is made during assembly to reduce balance correction. After assembly, the rotor is dynamically balanced.

The FSS is machined to provide the thrust collar, which carries the forward and aft thrust loads. The FSS also provide the journal for the NO. 1 Bearing, the sealing surface for the No.1 bearing Oil seals and the compressor low pressure air seal.

The Mid shaft provides the sealing surface for several high-pressure air seals, locations of balance weight grooves the compressor-to-turbine marriage flange. Axial holes pass through the aft end of the Mid Shaft to supply the first stage bucket cooling air compressor 14^th stage.

1.2.2- 9HA GE Gas Turbine Lubrication Oil System

9 HA GE Gas Turbine Lubrication Oil System

2.4 Heat Exchanger and Filters:

The lubricant oil heat exchangers(LOHX-1 and LOHX-2) connect o the parallel lubricant filters(LF3-1 and LF3-2) This design is provided so that filters not in service can be changed without taking the turbine out of service.

Filter housings and heat exchangers are self-venting. A sight glass is located in the vent line from e filter and heat exchanger. When the heat exhanger and filter housing are full, oil will be visible in this sight glass.

By means of the manually-operated three-way transfer valve, one filter can be put into service as the second is taken out, without interrupting the oil flow to the main lube oil header. The transfer of operation from one filter to the other should be accomplished as follows:

1.           Close the drain valve of the filter. Open the filter valve and fill the standby filter until a solid oil flow can be seen in the flow sight in filter vent pipe. This will indicate a “filled” condition.
2.            Operate the transfer valve to bring the standby filter into service.
3.          Close the filler valve.                                                                                                                   

This procedure simultaneously brings the reserve heat exchanger into service.

Note

Only one heat exchanger is intended to be in service at one time. After transfer, the operator must verify that the cooling water isolation butterfly valves to/from the heat exchanger not in service are closed. Do not leave all four cooling water isolation valves open.

2.5 Seal Oil

The seal oil to the generator bearing is normally supplied by the lubricating system by the lubricating system through a separate line directly to the generator in the event of low lube system pressure or lube system shutdown for service one of two seal oil pumps supply the oil required to seal in the generator hydrogen. Under normal circumstances the AC motor driven pump would serve this function however if this AC motor should fail or if AC power is lost the emergency DC motor is activated and drives the seal oil pump in piggyback AC/DC motor configuration separated AC and DC pumps). The AC motor includes a heater to prevent condensation in the motor. The seal oil pumps circulate oil through filter. Differential pressure switch provides a high differential pressure alarm signal across the filter. The filter element should be replaced near or at the alarm set point.

2.6 Optional Devices

Pressure transmitters

The lubrication module may include the following additional pressure transmitters (indication only) when selected by a customer as an option;

1.      Differential pressure transmitters which provide remote monitoring capability of differential pressure across oil filters.

2.       Pressure transmitter which provides remote monitoring capability of bearing header pressure.

3.       Pressure which provides remote monitoring capability of tank oil level.

These transmitters are indication only devices. They do not alarm or trio the machine in case of failure, low pressure, level etc.

Lube Oil Conditioner

The lube oil system may also include a lube oil conditioner when selected by a customer as an option. The lube oil conditioner is a stand-alone, kidney-loop lube oil conditioning skid designed specifically to remove particulate contamination (from 0.2 to 2 microns in size). Particulate contamination in this size range is the precursor to varnish formation and accumulation. The implementation of lube oil condition together with monitoring and maintenance of the lubrication oil additive package will help prevent the formation and accumulation of varnish and therefore varnish related turbine trips due to sticking hydraulic servo valves etc.) The lube oil condition skid is a standalone customer located skid with all function controlled by an onboard PLC there is no interface to MK VI control system.

Oil entering the Lube oil conditioner skid is monitored for temperature via thermocouple LT-LC. The oil then passes through the pump and into the pre-filter which is monitored for pressure by transducer. The oil then passes into the charging/mixing vessel, which is monitored for pressure by a transducer. Next, the oil moves to the final canister, containing the post-filter which is monitored for pressure by transducer. Finally, oil exiting the skid is monitored for pressure by transducer. All of these devices communicate solely with the PLC onboard the Lube Oil Conditioner Skid.