Combustion System Fundamentals
Modern gas turbines that use a wide variety of gaseous and liquid fuels must operate within a series of constraints, with NOx and CO emissions being the most notable. The formation of NOx compounds is dependent on the temperature of the reaction in the combustor. If fuel and air are allowed to mix in a stoichiometric proportion (a balanced chemical reaction), they will burn in a diffusion flame, similar to the flame of a candle, near the highest possible temperature of the reaction. A consequence of burning fuel at a high flame temperature is the production of a large amount of NOx. However, if extra air is introduced into the reaction, the resulting lean mixture burns with a lower flame temperature and the reaction generates significantly lower levels of NOx. This is known as lean combustion. In addition to developing combustion technologies that reduce emissions, GE’s advanced gas turbine combustion systems mitigate the potential risk of combustion dynamics while simultaneously meeting other key operability requirements. The overall system configuration is based on a balance of parameters that require a deep domain expertise in fuel and combustion technology.
Premixed Combustion Systems Multiple combustion systems are available for application across
GE’s gas turbine portfolio. Since we introduced our dry low NOx (DLN) systems in the 1970s, development programs have focused on evolutionary systems capable of meeting the extremely low NOx level requirements of current and future regulations, while providing customers with a range of operational and fuel flexibility options. Our DLN combustion systems are available for all heavy duty gas turbines:
• The DLN1 and DLN1+ combustion systems are available on E-class gas turbines.
• The DLN2 family of combustion systems (DLN2.5, DLN2.6, DLN2.6+, DLN2.6+AFS) is available on F- and H-class gas turbines.
• The DLE (dry low emissions) combustion system is available on LM, TM, and LMS series aeroderivative gas turbines.
DLN1/DLN1+ The DLN1 and DLN1+ combustion systems are proven technology platforms that help power plant operators meet increasingly strict environmental standards, while providing operational and fuel flexibility.
• Globally, more than 870 E-class gas turbines have an installed DLN1 or DLN1+ system.
• The DLN1+ combustion system has been in operation for more than 28 million hours, including more than 730,000 fired hours.
• The DLN1+ system delivers NOx emissions of 5 ppm or less for GE’s 6B, 7E and 9E gas turbines.
• These systems are highly fuel flexible and capable of operating on a wide variety of gas fuels, including gases with high ethane and propane content, as well as distillate oil and other liquid fuels.
• These systems are available in gas-only or dual fuel configurations.
DLN2 The DLN2 family of combustion systems enables GE’s F- and H-class gas turbines to reduce NOx emissions while extending outage intervals. GE’s DLN2.6+ combustion system, which is the base combustion configuration on the 7F, 9F and HA gas turbines, has been installed globally on more than 75 gas turbines and has accumulated over 1.6 million fired hours.
• Globally, more than 1,150 gas turbines have an installed DLN2 system.
• Units with these systems have accumulated more than 50 million operating hours, displaying proven operational experience in providing customers with a multitude of benefits, including increased operational and fuel flexibility, reduced emissions, extended intervals, and higher performance while maintaining life cycle costs.
• DLN2 units can operate on a wide variety of gas and liquid fuels.
• These systems are available in gas-only and dual fuel configurations.
DLE GE’s DLE combustion technology achieves NOx emissions of 15 ppm without water or steam injection.
• DLE technology is installed on more than 950 gas turbines globally.
• Units with these systems have accumulated more than 21 million operating hours; displaying proven operational experience in providing customers with a multitude of benefits, including increased operational and fuel flexibility, reduced emissions, extended intervals, and higher performance while maintaining life cycle costs.
• DLE units can operate on a wide variety of gas and liquid fuels.
• These units are available in gas-only, liquid-only, and dual fuel configurations.
Advanced Liquid Fuel Technology
The use of distillate fuel continues to be an important fuel option for many global power plants. For some plants, distillate fuel is the only option as natural gas is not available, while for many other power plants across the globe distillate fuel oil #2 is the backup fuel of choice. Traditional liquid fuel systems inject water to meet NOx emission levels for global, regional and/or national environmental regulations. The use of diluent has an impact on overall cycle efficiency and power plant economics. GE is developing a liquid fuel technology that dramatically reduces, if not completely eliminates, the amount of water injection required to meet NOx emissions.
Images from combustion testing in GE’s Gas Turbine Technology Lab
Natural gas flame
Advanced technology distillate oil flame
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