Gas Turbine Combustion Systems

About me 2007-Present Solar Turbines Inc., Caterpillar Company 2002-2007 Ph.D. Combustion Science, MAE, UCSD 2000-2002 General Electric Global Research Center 1998-2000 M.S., Aerospace Engineering, Indian Institute of Technology & University of Stuttgart

Motivation to study about Industrial Gas Turbines What does combustor do? Types of combustors Design requirements Introduction to combustion chemistry Alternative fuels, pollutants, oscillations Challenges related with variable load conditions

Energy Outlook Report US DOE

Trend of world’s energy consumption (Data from US Department of Energy) 1 Quadrillion = 1015, 1 BTU = 1.055x103 J 1 Quadrillion BTU = 45M Tons Coal or 1T ft3 Natural Gas or 170M Barrels of crude oil 1 Barrel crude oil = 42 gallon = 6.1 GJ of energy World’s energy requirement can largely be classified into Electric power, transportation energy

Trend of world’s electricity consumption (Data from US Department of Energy) *Organization of economic cooperation and development Major sources of electricity production Fossil fuels: Coal, gasoline, diesel, natural gas and other petroleum products Alternative sources of energy: Wind turbines, solar panels, hydroelectric, nuclear, geothermal, tidal, and list goes on… Alternative fuels: Ethanol, bio-diesel, biomass, coke oven gas, syngas, municipal waste, landfill gases, anything rotting…

Gas turbines industry is going to stay in business for a long time There is a very well established energy infrastructure based on fossil fuels in US and across the globe. The world’s proven fossil fuel reserves and lifetimes The advantage of alternative fuels is that the existing infrastructure can be used. Gas turbines industry is going to stay in business for a long time

About Solar’s Gas Turbines

How does this story relate with Gas Turbines Combustion systems? “Strictly speaking, energy is not “consumed”, but rather is converted into different forms.” Various types of engines are used to achieve this objective. Types of engines Power generation: Gas Turbines, Steam Turbines, Nuclear, Hydro Transportation : diesel, gasoline, aircraft engines (based on gas turbine cycles) Steam turbines are similar to gas turbines but they have different principles of operation. Nuclear power plants use nuclear energy to make steam which rotates the steam turbines.

Gas Turbines find their applications in electric power generation, mechanical drive systems, supply of process heat and compressed air, pump drives for gas or liquid pipelines jet propulsion, land and sea transport (infancy state) Industrial turbines or prime movers

Solar Turbines Incorporated, a subsidiary of Caterpillar Company is a world leading producer of mid-range (1 MW – 25 MW) industrial gas turbines for use in power generation, natural gas compression, and pumping systems. There are 12,500+ engines installed in 102 countries Solar ranks as one of the 50 largest exporters in the United States

Our units are used for power generation, gas compression, and mechanical drive applications Power generation is the production of electrical energy whether for stand-by or base load power applications. Gas compression applications include gathering (at the well head), transmission (pipeline), re-injection (storage), and pressure boost (compression). Mechanical drive applications are units sold as prime-movers for non-Solar packaged driven equipment, whether generators, compressors, or pumps

Harbor Drive Facility

Gas Turbines OEMs

Output 1.2 MW Thermal Eff. 24.5% Output 4.6 MW Thermal Eff. 29.9% Output 7.7 MW Thermal Eff. 34.8% Output 11.2 MW Thermal Eff. 33.9% Output 15.3 MW Thermal Eff. 35.7% Thermal Eff. 39.5%

Latest addition… Output 22.3 MW Thermal Eff. 40%

Two Shaft Turbine Engine Power Generation Single Shaft Turbine Engine Output Shaft Power 3)Expansion (Turbine) 2) Combustion 1) Compression Two Shaft Turbine Engine Output Shaft Power Mechanical Drive

Simplistic Gas Turbines working principles 1-2 Isentropic compression (in a compressor) 2-3 Constant pressure heat addition (in a combustor) 3-4 Isentropic expansion (in a turbine) 4-1 Constant pressure heat rejection

Power generation for gas fields in Siberia Petrobras, offshore Brazil, Power generation and crude oil production Natural gas transmission, Desert environment

Solar’s presence in San Diego two, soon to be three, Titan 130's at UCSD two Taurus 60's at SDSU some recuperated Saturns at landfills in San Marcos and Santee a Saturn genset at the Hotel Del a Mercury 50 at the VA hospital two Mercurys at Qualcomm two Centaur 40s at the Balboa Naval Hospital a Taurus 60 at the Children's Hospital

List of companies and their products

Difference between Heavy Duty and Aeroderivative Turbines

Evolution of products : Uprates

Performance of Gas Turbines is limited by Component efficiencies Turbine working temperature Current state of the art Pr = 35/1 components = 85-90% TIT = 1650 K

What makes Gas Turbines attractive for Industrial prime movers? Advantages Very high power-to-weight ratio, compared to reciprocating engines Smaller than most reciprocating engines of the same power rating Fewer moving parts than reciprocating engines Low operating pressures High operation speeds Low lubricating oil cost and consumption High reliability Goes for 30-50K hours before first overhaul. Usually runs for 100K-300K hours (10+ years) life cycle Disadvantages Cost is much greater than for a similar-sized reciprocating engine since the material must be stronger and more heat resistant. Machining operations are more complex Usually less efficient than reciprocating engines, especially at idle Delayed response to changes in power settings These make GT less suitable for road transport and helicopters

Some Basics

Gas Turbine components Inlet system Collects and directs air into the gas turbine. Often, an air cleaner and silencer are part of the inlet system. It is designated for a minimum pressure drop while maximizing clean airflow into the gas turbine. Compressor Provides compression, and, thus, increases the air density for the combustion process. The higher the compression ratio, the higher the total gas turbine efficiency . Low compressor efficiencies result in high compressor discharge temperatures, therefore, lower gas turbine output power. Combustor Adds heat energy to the airflow. The output power of the gas turbine is directly proportional to the combustor firing temperature; i.e., the combustor is designed to increase the air temperature up to the material limits of the gas turbine while maintaining a reasonable pressure drop.

Gas Producer Turbine Expands the air and absorbs just enough energy from the flow to drive the compressor. The higher the gas producer discharge temperature and pressure, the more energy is available to drive the power turbine, therefore, creating shaft work. Power Turbine Converts the remaining flow energy from the gas producer into useful shaft output work. The higher the temperature difference across the power turbine, the more shaft output power is available. Exhaust System Directs exhaust flow away from the gas turbine inlet. Often a silencer is part of the exhaust system. Similar to the inlet system, the exhaust system is designed for minimum pressure losses.

What drives Research and Development work in Gas Turbines? In 1950’s component efficiencies In 1990’s emissions In 21st century it is emissions and alternative fuels Nature of application and location are always the factors

Simplistic Gas Turbines working principles 1-2 Isentropic compression (in a compressor); h2-h1 = mCp(T2-T1) 2-3 Constant pressure heat addition (in a combustor); h3-h2 = mCp(T3-T2) 3-4 Isentropic expansion (in a turbine); h3-h4 = mCp(T3-T4) 4-1 Constant pressure heat rejection

mFqRcomb (min+mF)CpTout minCpTin Gas Turbine Shaft power 

Consider Centaur and Mercury Known P ratio = 10 TIT = 1350 K Compressor Eff. = 0.86 Turbine Eff. = 0.89 Heat exchanger effectiveness = 0.8 Ambient temperature and pressure, 300 K, 1 bar Specific heat Cp = 1.005 kJ/Kg-K Specific heat ratio  = 1.4 Calculate (a) Compressor outlet temperature (b) Turbine out temperature (c) Compressor work (d) Turbine work (e) back work ratio (f) Efficiency for ideal, actual, and recuperator engine

First Law: Stagnation enthalpy Compressor work Turbine work Heat input For isentropic process

Thermal Efficiency Net work out

Equipment efficiencies 3 T 4 2 4’ 2’ 1 S Process 1-2’ and 3-4’ ideal Process 1-2 and 3-4 actual

Heat exchanger effectiveness Recuperator 3 T Heat exchanger effectiveness 5 4 2 4’ 2’ 6 1 S

Variation of Cp with temperature