GAS TURBINE

GE F404-IN20

By: Manu Khurana SELE

• First Indigenous Fighter Plane

• Turbofan GE F404-IN20

• Based on same basic principles

Panipat Refinery

• 5 GAS Turbines of 30.77 MW each

• 3 Steam Turbines of 25 MW each

• 2 feeders from HPGCL for emergency power

• 1 PNCP interconnecting Feeder of 50 MVA capacity.

GAS TURBINE SUMMARY DATA :

• FRAME - 6

• MAKE – BHEL/GE

• TYPE - MS 6000, SINGLE SHAFT DESIGN

• BASE LOAD CAPACITY – 30.77 MW

• GENERATOR CAPACITY: 38.625 MVA

• FUEL – ( NAPHTHA,HSD & RLNG )

• RATED SPEED – 5133 RPM

• COMPRESSOR – AXIAL FLOW TYPE, 17 STAGES

• AIR HANDLING CAPACITY 400 T/HR , COMP RATIO 11:1

• TURBINE – 3 STAGES

Basic Diagram

COMP TURB

COMB

FUEL LOAD

How A Gas Turbine Works

Basic principle of Operation

A gas turbine operates by: 1. Continuously drawing in fresh air - Point 1, 2. Compressing this air to a higher pressure - Point 2 3. Adding and burning fuel in the compressed air to increase its energy level. 4. Directing the high pressure high temperature air to an expansion turbine - Point 3 - that converts the gas energy to the mechanical energy of a rotating shaft. 5. The resulting low pressure, lower temperature gases are discharged to atmosphere or HRSG – Point 4

Co- Generation Configuration

Brayton+Rankine Cycle

Major Components

• Air Inlet – filters and directs the air into to the compressor. • Compressor – axial flow. Draws air in and compresses it to a higher

pressure and temperature. Consists of rotor assembly, stator casings, rotating and stationary blades.

• Combustors – multiple combustion chambers where fuel and air are mixed and burned to provide the heat energy to the turbine. Directs the combustion gases to the

TURBINE SECTION • Turbine – converts the hot gas kinetic energy into rotational shaft power. • Exhaust – directs the high temperature, low pressure, gases to

atmosphere or to a • heat recovery steam generator (HRSG) • Auxiliary Support Systems: Controls, Lubrication Oil, Hydraulics, Cooling

and Sealing Air and others required for the operation, control and protection of the turbine.

Major Sections and Components

Air Inlet system

• Filters

• Coolers (if provided)

• Duct/Silencer

• Inlet air heating manifold (if provided)

• Trash Screen

• Plenum – directs air to the inlet bellmouth casing

Inlet air filters

Evaporative Cooler (GT-3) •Efficiency improvement

•Increased Baseload

•Increased Humidity

•Maintaining Water Quality

Casings

• Structural pressure vessel and backbone of the turbine supporting the bearings, rotor and stationary components. Constitute the outer wall of the air/ gas-path annulus

• Sections split at horizontal and vertical joints to facilitate maintenance.

• Inlet (Bellmouth)

• Compressor (17 stage axial)

• Compressor Discharge

• Turbine Shell

• Exhaust Frame

• Exhaust Diffuser

Casings

Inlet Casing

Discharge casing

Compressor

discharge casing

IGV • IGV permits fast, smooth

acceleration of the turbine

without compressor surge.

• A hydraulic cylinder mounted

on a base cross member

actuates the IGV through a

large ring gear and multiple

small pinion gears.

• Gear & Rack Material: Stainless

steel IGV Material: Cr-Ni-Cd ,C-450

Compressor •Rotor - bolted design of individual stage wheels/disks and stub shafts as a bolted assembly. Forward stub shaft contains the #1 bearing rotor journal, thrust (bearing) collar and 60 tooth speed ring. Rotor blades attached via slots in the outside diameter or each wheel. • Inlet guide vanes – variable IGVs direct the air onto the first row of rotating • Blades - Limit amount of entering air during startup and shutdown to prevent surge/pulsations. Control air flow during turbine operation to help control exhaust temperatures. On startup & shutdown the VIGV’s are closed – 26 to 30 degree angle when below approximately 80% speed. Full Open position is typically 84 to 89 degree angle

Compressor

• Each rotating row of blades (airfoils) increases the velocity of the incoming air raising its kinetic energy. Attach to rotor via dovetail fits.

• The stationary row of blades (vanes) act as diffusers converting the kinetic energy to a pressure increase and guides the air onto the next stage of rotating blades. Mounted to the casings inside diameter.

• Extraction ports for pulsation protection with compressor bleed valves and for cooling/sealing air supply.

Combustion Section

• Combustion chambers.

• Fuel nozzles.

• Cross -fire tubes.

• Transition pieces.

• Combustion liners.

• Spark plugs (2 nos. at no.1&10)

• Flame detectors (4 nos at no 2,37&8)

Combustion Chambers

Reverse Flow type Combustors

Air flow through the chambers is on the outside of the liners and is counter flow in relation to the hot gas flow . Serves to cool the liners and transition pieces and preheats the air to be used for combustion

Fuel Nozzles

• Serves to inject fuel, atomizing air and gas fuel into each chamber. Fuel and air are mixed at the fuel nozzle tip

Combustion liner

• located with each chamber. Contains the combustion flame. Have cooling and mixing holes to enhance the fuel combustion reaction and to cool (dilution air) the combustion gases prior to entering the transition piece and turbine section. Liners are cooled with the compressor discharge air flowing on the outside and for some designs the inside diameter is cooled via slots in the liner walls

• Material : Hastelloy X

• Crossfire tubes: Interconnect the individual chambers to facilitate lighting of each chamber at initial ignition at 1 or 2 chambers.

• Flow Sleeve – located inside each chamber. The liners are located inside the flow sleeves. Flow sleeves direct compressor discharge air along the outside of the liners. Provides insulation barrier between the liner and combustion chamber.

• Transition Piece and seals – directs the combustion gases from the liner to the first stage turbine nozzle. Quantity – 1 per chamber.

• Spark plug – igniters – quantity 2. Electric arc igniter used to ignite the fuel at startup. Once flame is established these shut off. Power supplied from igniter transformers at 15,000 to 20,000 volts. Need only 1 to light off (fire) the turbine.

• Flame detectors – UV. Detect the presence of flame in the monitored chambers. Typically 4 are used per unit. Primary function is for startup and shutdown to indicate flame. Also used for flameout protection during full operation. Need at least 2 out of 4 functional to operate the turbine.

Temperature and Pressure profile

1400-1900 C 1100-1300 C

Turbine Section-Hot Gas Path

• 3 stages of stationary nozzles and rotating buckets.

• Buckets (Stage 1, 2, 3) – convert the high velocity (kinetic) energy from the nozzles into rotational mechanical shaft energy. Buckets are attached to the turbine wheels via a dovetail (fir tree) fit.

• Stationary Nozzles (Stage 1, 2, 3) – convert the high pressure gases into high velocity (kinetic) energy jets that impinge on the turbine buckets

Nozzle

Bucket

Turbine Assembly

Blade material

• Owing to high temp , The need for better materials spurred in the field of alloys and manufacturing techniques, One of the earliest of these was Nimonic ( 50% nickel and 20% chromium with additives such as titanium and aluminium. )

• The development of superalloys in the 1940s and new processing methods such as vacuum induction melting in the 1950s greatly increased the temperature capability of turbine blades.

• Further processing methods like hot isostatic pressing improved the alloys used for turbine bladoften use nickel-based superalloys that incorporate chromium, cobalt, and rheniumes and increased turbine blade performance. Modern turbine blades.

• A major breakthrough was the development of directional solidification (DS) and single crystal (SC) production methods. These methods help greatly increase strength against fatigue and creep by aligning grain boundaries in one direction (DS) or by eliminating grain boundaries all together (SC).

• Another major improvement to turbine blade material technology was the development of thermal barrier coatings (TBC). Where DS and SC developments improved creep and fatigue resistance, TBCs improved corrosion and oxidation resistance, both of which become greater concerns as temperatures increased.

• The first TBCs, applied in the 1970s, were aluminide coatings. Improved ceramic coatings became available in the 1980s.

• Another strategy to improving turbine blades and increasing their operating temperature, aside from better materials, is to cool the blades. There are three main types of cooling used in gas turbine blades; convection, film, and transpiration cooling. While all three methods have their differences, they all work by using cooler air (often bled from the compressor) to remove heat from the turbine blades.

• The blades are coated with the TBC they will have, and then cooling holes are machined as needed, which gives further higher temperature sustenanace, thus creating a complete turbine blade.

Turbine Blade Material

• Stage#1 Nozzle: FSX 414 + Cooling

• Stage#2 Nozzle : GTD 222 +Cooling

• Stage#3 Nozzle : GTD 222

• Stage#1 Bucket: DS- GTD111+ 16 Cooling Holes

• Stage#2 Bucket: INCO 738 + 6 Cooling Holes

• Stage#3 Bucket : INCO 738

Bearings

• Journal - supports rotor

• Thrust – bears axial load

Cutaway view of Accessory gear

Cooling and Sealing Air

• Bearing cooling and sealing

• Cooling of internal turbine parts subjected to high temprature.

• Cooling of turbine outer shell and exhaust frame

• Pulsation protection

• Providing air supply for air operated valves

• Providing air for auxiliary requirements