Briefly explain a GT (Full speed no load condition). Stop igniters, flame detectors .
igniters, flame detectors .By nipping Simple cycle operation: When GT
A marine gas turbine is a type of command is given from panel. Fuel up trouble at very beginning have alone is operated, it is known as
engine used to propel marine vessels, supply is reduced automatically and significant effect on reliable simple cycle operation.
such as ships and submarines. It then GT start coasting down .As the continuous service of the Simple cycle efficiencies are very
operates on the principle of converting speed come down to around 60% or engine.2.Baroscopic inspection. low, normally of the order of 30% to
the energy of combusted fuel into below the fuel is shut of completely. Inspection of turbine internals using a 33%. Combined cycle concept: A
mechanical power. GT coasts to rest. At zero speed, the baroscope. Access holes for combined cycle Down stream of GT is
Compressor: Air is compressed by a ratcheting starts automatically now. borescope provided in GT for inserting placed an HRSG to operate a steam
series of rotating blades within the (This means turning gear is on) optical borescope probe on a non- turbine plant to produce power .
compressor section. The compressor Ratcheting is stopped after GT is operating gas turbine for visual Overall efficiency of this plant is of
increases the pressure and density of cooled down (Wheel-space observation of stationary and rotating the order 42% to 47%. Co-generation
the air before entering the combustion temperature <80 degree C). parts with out removing casing upper plant: In a cogeneration plant HRSG
chamber. The auxiliary lube oil pump starts part. steam is utilised not for steam turbine
Combustion Chamber: The automatically during shut down cycle Running inspection consists of the operation ; but utilised for process
compressed air enters the combustion and runs until cool down is completed observations made during the engine in requirements like desalination plant or
chamber, where it is mixed with fuel, service. Operating data recorded and chemical process plants .plant
typically liquid or gaseous. The fuel- Lubrication system evaluated periodically. A few efficiency of the order 75% to 85%.
air mixture is ignited, creating a high- Major lubricating system parts- A parameters typical running inspection Energy Efficient Facilities:
temperature and high-pressure gas. majority of the parts listed are to focus on are as given below: Exhaust Regenerator, Intercooler, Reheater.
Turbine: The hot, high-pressure gas normally found in the lubrication temperature, wheel space temperature, Regenerator: In order to achieve fuel
flows through a series of turbine system of most gas turbine engines exhaust plenum- duct leaks. vibration economy, hot gases from turbine
blades. The expanding gas causes the Lubricating oil reservoir MOP-Main ,fuel flow ,fuel nozzle pressure, fuel oil exhaust is used to pass through a heat
turbine blades to rotate rapidly. The oil pump (driven from accessory leaks Bearing Lubricating oil pressure exchanger to raise the compressed air
turbine extracts energy from the gas, gear).AOP-Auxiliary oil pump(driven , lubricating oil leaks. IGV position, temperature thus recovering heat from
converting it into mechanical power. by motor).EOP-Emergency oil pump air inlet filter differential pressure. exhaust thus bringing down the fuel
Shaft: The rotating turbine is ((driven by DC motor). Scavenger Shut down inspection are performed consumption. This increases the
connected to a shaft, which transmits pump(s)also often provided in return at pre planned specific intervals by efficiency by 20-30%. Intercooler:
the mechanical power to the line. shutting down the gas turbine. CI - Intercooler is used to improve the
propulsion system. In marine In a typical gas turbine lubrication COMBUSTION INSPECTION, HGP- efficiency of the gas turbine which
applications, the shaft is usually system, a pressurized system or pump HOT GAS PATH INSPECTION, MI- increases the net work output by
connected to a propeller or water jet circulates the lubricant oil among the MAJOR INSPECTION providing inter coolers between
system, generating thrust to propel the different components that are required Combustion inspection: (After stages. As air temperature reduces air
vessel. to be lubricated and cooled, while a completion of 8000 fired hours[after density increases by which enable the
The sketch shows the general layout scavenging system returns the oil back every 1 year period)) include Fuel compressor to produce the desired
of the marine gas turbine, including to the storage tank.The lubricating nozzles, combustion liners and discharge pressure by doing less work.
the compressor, combustion chamber, requirements for the gas turbine are transition pieces are removed for Reheater: High-pressure gases from
turbine, and shaft. furnished by a common forced-feed inspection and repairs/replacement. the primary combustion chamber
Advantages of GT as Marine lubrication system. Lubricating fluid is HGP (After 24000 fired hours [after enters the high-pressure stage of the
Engine circulated to a] the turbine bearings, every 3 years]) Whole the casing is gas turbine where energy is extracted
High power to weight ratio/less generator bearings] the reduction gear horizontally split and the top half can and the temperature and the pressure
weight. It is compact and hence system (load gearbox), accessory gear be lifted up removing all bolts for drops. The cooler gases exiting this
occupies less space. Ability for quick system (accessory gearbox). access to internal parts. Inspect rotor high pressure stage then enters a
start and reliable operation. High- Branches: a] a branch taken as control blades &stator blades opening turbine secondary combustion chamber called
speed engine. GT package is easy to oil b] a branch taken as coupling oil to casing top cover ALONE during HGP the reheat combustor where additional
shift and to install. Less pollution as lubricate couplings] a branch taken as inspection. fuel is burnt to raise the temperature
only clean fuel fired. Less cooling suction for hydraulic oil pump d] MAJOR INSPECTION (After 48000 of the gases again. These gases then
water requirement Bearing oil lines to bearings are fired hours[after every 6 years]) enters the second stage of turbine
Disadvantages of GT as Marine provided with orifices and oil pressure Apart from combustion and hot gas where, due to the increased
Engine around 12 to 15 kgcm2 maintained, path inspection, the whole casing temperature more energy can be
Capital cost high. Operating cost high. upper part is removed including both extracted.
Maintenance cost high. Strict Liquid Fuel Oil System compressor & turbine for inspection, Features of Aero Derivative
maintenance schedules. High speed Fuel trip valve is open and fuel is rotor removal, repair or replacement of Combustion Chamber:
engine. [Double reduction load gear available at main fuel pump suction. internal parts. Primary air [combustion air]: Air is
box provided to drive propeller]. Open Pump supply fuel at high discharge introduced around the let of fuel.
cycle efficiency is only around 35%. pressure through HP filter to Flow Two-spool split shaft Marine GT Burns approximately at stoichiometric
Complex in design and manufacturing. divider- [refer line diagram]Fuel pump Consist of low pressure compressor ratio during rapid combustion
Not economical for marine use. bypass valve regulates the amount of driven by the low pressure turbine , generating very high temperature.
Start-up procedure of GT fuel input to the turbine combustion high pressure compressor driven by Secondary air :[INTERMEDIATE
GT is put on ratcheting (on turning chamber by varying amount of the high pressure turbine, combustor, AIR] [ for completing combustion]:
gear). Starting device is energized and bypassed fuel. If bypass valve closes, and free power turbine. This Secondary air introduced through
connected to turbine to bring it up to more fuel goes to the combustors & configuration of GT operates at a holes in this zone to supplement the
firing speed or cranking speed, which vice versa. Flow divider: Flow divider higher efficiency as:. Low-pressure combustion process and ensure
is 20% of normal speed. Fuel is supply oil to all combustion chambers compressor run at lower rpm complete combustion. Dilution Air
injected and ignited at 20% normal at equal pressure and equal quantity. compressor consume less power to [to bring down temperature ]:
speed. After a short warm up period, high pressure fuel oil pushes the gears produce desired compression ratio. Additional air is fed for diluting and
additional fuel is supplied and the unit inside the flow divider. since all gears This design allows higher cooling the exit gases from
is accelerated to self-sustaining speed. are mounted on same shaft, all gears compression ratio to operate combustor.
50% speed. At this speed the starting rotate at same RPM and the flow is efficiently over the entire speed range. Low weight and small frontal area.
device automatically get divided equally among all gears . Both LP & HP compressors operate at Less pressure loss. Ability to
disengaged.[jaw clutch disengages]. their own optimum speed. withstand high temperature and
Under the control of GT control INSPECTION IN GT corrosive conditions for long life.
system, the speed accelerate and Stand By Inspection, Running Facilities to enhance performance of Serviceability/ easy access for
reaches full speed. Now the machine is Inspection, Shut Down Inspection. GT maintenance. Ability to provide
ready to take up load.GT load can be Stand by Inspection: Pertaining to Two ways to enhance performance: Uniform temperature distribution in
varied from control panel as per visual inspection and maintenance By heat recovery and Incorporating turbine inlet. Stable operation across a
demand. during unit shut down. It energy efficiency facilities. wide operating range. Complete
Shut Down Sequence of GT includes:1.Cleaning up, attending to Heat Recovery: Simple Cycle combustion of fuel in the space of
GT drive load is brought to zero and leaks, filter changing, checking of lube Operation, Combined cycle operation, combustion chamber. Low emission.
disengaged.GT now running at FSNL oil and fuel oil piping ,checking Co-generation plant.
Briefly Explain GT Two-spool split shaft Marine GT
Aero Derivative GT
Performance Enhancement of A GT
Fuel Oil System
Lubrication System
