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Gas turbine power plant

Gas turbine engines derive their power from burning fuel in a combustion chamber and using the fast flowing combustion gases to drive a turbine in much the same way as the high pressure steam drives a steam turbine.
The gas turbine is the engine at the heart of the power plant that produces electric current. A gas turbine is a combustion engine that can convert natural gas or other liquid fuels to mechanical energy. This energy then drives a generator that produces electrical energy.
In a gas turbine, gas is ignited under pressure and combustible high-pressure, high-temperature gases are produced. The combustible gases power a turbine, which in turn powers a generator. In a boiler power plant, electricity is generated by heating water to produce steam which, via a turbine, powers a generator.

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Gas turbine power plant

  1. 1. Combustion and Power Generation Dr. O.P. TIWARI H.O.D, Mechanical Engg. S.R.I.M.T S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,LkoDEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T, Lko
  2. 2. Power Plant Engineering Classification of Power Plants Steam (Thermal) Power Plant Hydro Electric Power plant Nuclear power Plant Gas Turbine Power Plant Diesel Power Plant S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  3. 3. Gas Power Plant • A gas power plant uses gas turbine as the prime mover for generating electricity. • It uses natural gas or kerosene or benzene as fuel. • Gas plant can produce only limited amount of the electricity. •Efficiency of the plant is only 35% S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  4. 4. Layout of the Gas turbine Power plant S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  5. 5. 5 Types of Gas Turbine Plants • Simple Cycle – Operate When Demand is High – Peak Demand – Operate for Short / Variable Times – Designed for Quick Start-Up – Not designed to be Efficient but Reliable • Not Cost Effective to Build for Efficiency • Combined Cycle – Operate for Peak and Economic Dispatch – Designed for Quick Start-Up – Designed to Efficient, Cost-Effective Operation – Typically Has Ability to Operate in SC Mode S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  6. 6. 6 Gas Turbine Basic Components Compressor Compressor Turbine Section Power Turbine Section S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  7. 7. Basic Components S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  8. 8. Basic Components • Compressor – Draws in air & compresses it • Combustion Chamber – Fuel pumped in and ignited to burn with compressed air • Turbine – Hot gases converted to work – Can drive compressor & external load S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  9. 9. Basic Components • Compressor – Draws in air & compresses it • Combustion Chamber – Fuel pumped in and ignited to burn with compressed air • Turbine – Hot gases converted to work – Can drive compressor & external load S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  10. 10. Basic Components • Compressor – Draws in air & compresses it • Combustion Chamber – Fuel pumped in and ignited to burn with compressed air • Turbine – Hot gases converted to work – Can drive compressor & external load S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  11. 11. Compressor • Compressor types 1.Radial/centrifugal flow compressor 2.Axial flow compressor 3.Supplies high pressure air for combustion process S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  12. 12. Compressor • Radial/centrifugal flow – Adv: simple design, good for low compression ratios (5:1) – Disadv: Difficult to stage, less efficient • Axial flow – Good for high compression ratios (20:1) – Most commonly used S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  13. 13. Compressor • Controlling Load on Compressor – To ensure maximum efficiency and allow for flexibility, compressor can be split into HP & LP sections – Vane control: inlet vanes/nozzle angles can be varied to control air flow • Compressor Stall – Interruption of air flow due to turbulence S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  14. 14. Use of Compressed Air • Primary Air (30%) – Passes directly to combustor for combustion process • Secondary Air (65%) – Passes through holes in perforated inner shell & mixes with combustion gases • Film Cooling Air (5%) – Insulates/cools turbine blades S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  15. 15. Blade Cooling S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  16. 16. Gas Turbine Combustion F/A – 0.01 Combustion efficiency : 98% S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  17. 17. Combustion Chambers • Where air & fuel are mixed, ignited, and burned • Spark plugs used to ignite fuel • Types – Can: for small, centrifugal compressors – Annular: for larger, axial compressors (LM 2500) – Can-annular: rarely used S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  18. 18. GAS TURBINES • Invented in 1930 by Frank Whittle • Patented in 1934 • First used for aircraft propulsion in 1942 on Me262 by Germans during second world war • Currently most of the aircrafts and ships use GT engines • Used for power generation • Manufacturers: General Electric, Pratt &Whitney, SNECMA, Rolls Royce, Honeywell, Siemens – Westinghouse, Alstom • Indian take: Kaveri Engine by GTRE (DRDO) S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  19. 19. Turbines • Consists of one or more stages designed to develop rotational energy • Uses sets of nozzles & blades • Single shaft – Power coupling on same shaft as turbine – Same shaft drives rotor of compressor and power components S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  20. 20. Turbines • Split Shaft – Gas generator turbine drives compressor – Power turbine separate from gas generator turbine – Power turbine driven by exhaust from gas generator turbine – Power turbine drives power coupling S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  21. 21. Dual Shaft, Split Shaft S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  22. 22. Gas Turbine Systems • Air System – Air intakes are located high up & multiple filters – Exhaust discharged out stacks • Fuel System – Uses either DFM or JP-5 • Lubrication System – Supply bearings and gears with oil S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  23. 23. Brayton Cycle(working cycle) 1-2: Compression 2-3: Combustion 3-4: Expansion through Turbine and Exhaust Nozzle 4-1: Atmospheric Pressure) S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  24. 24. s T 1 4 2' 3 2 4' 3' 3'' v P 1 4 2 3 Closed Brayton cycle (cont.) QH QL s=const QH QL p=const S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  25. 25. Efficiency of a Brayton cycle 1st law for this cycle: W Q QH L  energy conversion efficiency is:     useful work heat input W Q Q Q QH H L H            1 1 4 1 3 2 Q Q mC T T mC T T L H P P          1 1 1 1 4 1 2 3 2 T T T T T T S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  26. 26. Efficiency of a Brayton cycle (cont.) for an isentropic process:  P P V V k 1 2 2 1 T T P P P P T T k k k k 2 1 1 2 1 3 4 3 4 1                 in case of an ideal gas: T T T T 3 2 4 1              1 11 2 1 2 1 T T P P k k PV P V T T1 1 2 2 1 2 Pv constk  S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko So…
  27. 27. Efficiency of a Brayton cycle (cont.) isentropic pressure ratio       1 1 2 1 1 P P k k 0 10 20 30 40 50 60 0 5 10 15 Pressure ratio Thermalefficiency% Example S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  28. 28. PRINCIPLE OF OPERATION • Intake – Slow down incoming air – Remove distortions • Compressor – Dynamically Compress air • Combustor – Heat addition through chemical reaction • Turbine – Run the compressor • Nozzle/ Free Turbine – Generation of thrust power/shaft power S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  29. 29. 29  The energy contained in a flowing ideal gas is the sum of enthalpy and kinetic energy.  Pressurized gas can store or release energy. As it expands the pressure is converted to kinetic energy. Principles of Operation • Open Cycle Also referred to as simple cycle) Link to picture S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  30. 30. heat exchanger Closed Brayton cycle 2 1 4 turbinecompressor Wnet QH QL heat exchanger 3 S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  31. 31. 31 Thermodynamic Fundamentals • Pressure Ratio & CT Components S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  32. 32. COGENERATION • Decentralized combined heat and power production-cogeneration is a very flexible and efficient way of utilizing fuels. • Cogeneration based on biomass is environmentally friendly, and all kinds of biomass resources can be used. • Cogeneration plants can be used in all situations where a given heat demands exists. • COGENERATION TECHNOLOGIES • Gas Engines. • Gas Turbines. • The Stirling Engine. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  33. 33. Brayton cycle with regeneration turbine exhaust compressor air intake combustion chamber fuel Wnet regenerator x 1 2 3 y regenerator S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  34. 34. Modified Brayton cycle turbines exhaust compressors combustion chamber regenerator 9 8 1 5 6 7 10 fuel air intake 2 3 intercooler 4 S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  35. 35. Modified Brayton cycle • multi-stage compression with intercooling • multi-stage expansion with reheat s T 3 8 4 7 1 6 5 2 9 10 S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  36. 36. AUXILIARY SYSTEMS • Auxiliary systems are the backbone of the gas turbine plant. Without auxiliary system, the very existence of the gas turbine is impossible. 1.STARTING SYSTEMS : Two separate systems-starting and ignition are required to ensure a gas turbine engine will start satisfactorily. • Types of Starter :-The following are the various types of gas turbine starter. • (a) Electrical :-(i) A.C. and (ii) D.C. • A.C. cranking motors are usually 3 phase induction types rated to operate on the available voltage and frequency. • D.C. starter motor takes the source of electrical energy from a bank of batteries of sufficient capacity to handle the starting load. Engaging or disengaging clutch is used. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  37. 37. • (b) Pneumatic or Air Starter :-Air starting is used mostly as it is light, simple and economical to operate. As air starter motor has a turbine rotor that transmits power through a reduction gear and clutch to the starter output shaft that is connected to the engine. • (c) Combustion Starter. It is in every respect a small gas turbine. It is a completely integrated system which incorporates a planetary reduction gear drive with over-running clutch. • (d) Hydraulic Starting Motor. It consists of a hydraulic starter motor for main engine, an accumulator, a hydraulic pump motor for auxiliary power unit (A.P.U.). • 2 .IGNITION SYSTEMS :-Ignition system is utilized to initiate spark during the starting. Once it starts, the combustion is continuous and the working of ignition system is cut-off automatically . • The following are the types of ignition system. 1. Capacitor discharge system. (a) High tension system and (b) Low tension system. 2. Induction system. 3. A. C. power circuits. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  38. 38. LUBRICATION SYSTEM • Elements of Lubrication System:-The following are the elements of lubrication system of a gas turbine • 1. Oil tank, • 2. Oil pump • 3. Filter and strainer, • 4. Relief valve, • 5. Oil cooler, • 6. Oil and pipe line, • 7. Magnetic drain plug, • 8. By-pass, valve, and • 9. Warning devices. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  39. 39. Fig:-Lubrication System for gas turbine S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  40. 40. CONTROL OF GAS TURBINES • The purpose of gas turbine controls is to meet the specific control requirements of users and safe operation of the turbine. There are basically two types of controls. They are as follows:- • (A) Prime control and • (B) Protection control 1.PRIME CONTROL • The objective of the prime control is to ensure the proper application of the turbine power to the load. • The users of the gas turbines have specific control requirements according the use of gas turbines . The requirements might be to control: • (1) The frequency of an a.c. generator, • (2) The speed of a boat or ship, • (3) The speed of an aircraft, • (4) The capacity or head of a pump or compressor, • (5) The road speed of a vehicle. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  41. 41. Fig-prime control (hydro-mechanical) S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  42. 42. 2.PROTECTIVE CONTROLS:- The objective of the protective control is to ensure adequate protection for the turbine in preventing its operation under adverse conditions. Basically, the protective control is of two types:- • 1. Shutdown control and • 2. Modulating control • 1. Shut Down Control The shut down type control detects a condition which can cause a serious malfunction and actuate the shut-off valve to stop the turbine following are the various types of shut down controls. • (a) Turbine over temperature, • (b) Turbine over speed, • (c) Low lube oil pressure, • (d) High lube oil temperature, and • (e) excess vibration. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  43. 43. • (2) Modulating Controls • The purpose of modulating control is to sense an impending malfunction or a condition, which could adversely affect turbine life and make some modification to the operating condition of the turbine in order to alleviate the undesired conditions. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  44. 44. Engine Power Transfer • Turbojet • Thrust provided by reaction against expansion of exhaust gases • Turbofan • Thrust provided by reaction against expansion of large volumes of air • Marine systems • Thrust provided by turbine • SCRAMjet/RAMjet S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  45. 45. 45 Combustion Turbine Fuels • Conventional Fuels – Natural Gas – Liquid Fuel Oil • Nonconventional Fuels – Crude Oil – Refinery Gas – Propane • Synthetic Fuels – Chemical Process – Physical Process S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  46. 46. Emission in Gas Turbines •Lower emission compared to all conventional methods (except nuclear) •Regulations require further reduction in emission levels S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  47. 47. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  48. 48. What is the CCGT? A combined cycle gas turbine power plant, frequently identified by CCGT shortcut,is essentially an electrical power plant in which a gas turbine and a steam turbine are used in combination to achieve greater efficiency than would be possible independently. The gas turbine drives an electrical generator.The gas turbine exhaust is then used to produce steam in a heat exchanger (steam generator) to supply a steam turbine whose output provides the means to generate more electricity. However the Steam Turbine is not necessarily, in that case the plant produce electricity and industrial steam which can be used for heating or industrial purpose. S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  49. 49. 49Picture courtesy of Nooter/Eriksen How does a Combined Cycle Plant Work? S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  50. 50. 50 Combining the Brayton and Rankine Cycles • Gas Turbine Exhaust used as the heat source for the Steam Turbine cycle • Utilizes the major efficiency loss from the Brayton cycle • Advantages: – Relatively short cycle to design, construct & commission – Higher overall efficiency – Good cycling capabilities – Fast starting and loading – Lower installed costs – No issues with ash disposal or coal storage • Disadvantages – High fuel costs – Uncertain long term fuel source – Output dependent on ambient temperature S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  51. 51. 51 Combined Cycles Today• Plant Efficiency ~ 58-60 percent – Biggest losses are mechanical input to the compressor and heat in the exhaust • Steam Turbine output – Typically 50% of the gas turbine output – More with duct-firing • Net Plant Output (Using Frame size gas turbines) – up to 750 MW for 3 on 1 configuration – Up to 520 MW for 2 on 1 configuration • Construction time about 24 months • Engineering time 80k to 130k labor hours • Engineering duration about 12 months • Capital Cost ($900-$1100/kW) • Two (2) versus Three (3) Pressure Designs – Larger capacity units utilize the additional drums to gain efficiency at the expense of higher capital costs S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  52. 52. 52 Combined Cycle Efficiency • Simple cycle efficiency (max ~ 44%*) • Combined cycle efficiency (max ~58-60%*) • Correlating Efficiency to Heat Rate (British Units)  = 3412/(Heat Rate) --> 3412/ = Heat Rate* – Simple cycle – 3412/.44 = 7,757 Btu/Kwh* – Combined cycle – 3412/.58 = 5,884 Btu/Kwh* • Correlating Efficiency to Heat Rate (SI Units)  = 3600/(Heat Rate) --> 3600/ = Heat Rate* – Simple cycle – 3600/.44 = 8,182 KJ/Kwh* – Combined cycle – 3600/.58 = 6,207 KJ/Kwh* • Practical Values – HHV basis, net output basis – Simple cycle 7FA (new and clean) 10,860 Btu/Kwh (11,457 KJ/Kwh) – Combined cycle 2x1 7FA (new and clean) 6,218 Btu/Kwh (6,560 KJ/Kwh) *Gross LHV basis S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  53. 53. 53 Gas Turbine Generator Performance Factors that Influence Performance – Fuel Type, Composition, and Heating Value – Load (Base, Peak, or Part) – Compressor Inlet Temperature – Atmospheric Pressure – Inlet Pressure Drop • Varies significantly with types of air cleaning/cooling – Exhaust Pressure Drop • Affected by addition of HRSG, SCR, CO catalysts – Steam or Water Injection Rate • Used for either power augmentation or NOx control S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  54. 54. Advantages and Disadvantages • Lower emission levels • Great power-to-weight ratio compared to reciprocating engines. • Smaller than their reciprocating counterparts of the same power. • Expensive: – high speeds and high operating temperatures – designing and manufacturing gas turbines is a tough problem from both the engineering and materials standpoint • Tend to use more fuel when they are idling • They prefer a constant rather than a fluctuating load. That makes gas turbines great for things like transcontinental jet aircraft and power plants, but explains why we don't have one under the hood of our car. S.R.I.M.T
  55. 55. Needs for Future Gas Turbines • Power Generation – Fuel Economy – Low Emissions – Alternative fuels • Military Aircrafts – High Thrust – Low Weight • Commercial Aircrafts – Low emissions – High Thrust – Low Weight – Fuel Economy Half the size and twice the thrust Double the size of the Aircraft and double the distance traveled with 50% NOx S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  56. 56. Ongoing Research • Effect of inlet disturbances • Combustion in recirculating flows • Spray Combustion –Needs and Challenges –Controlled atomization –Emissions in spray combustion S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko
  57. 57. THANK YOU S.R.I.M.T DEPARTMENT OF MECHANICAL ENGG. S.R.I.M.T,Lko

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