Peter Berenbrink

Suppression of Dynamic Combustion Instabilities by Passive and Active Means

In the gas turbine industry, lean premixed combustion is a state-of-the-art technology for the reduction of NOx emissions. Due to the ever increasing reaction densities and turbine inlet temperatures in modern gas turbines, the combustors reveal an increased tendency to form dynamic combustion instabilities.This paper reports on the use of passive and active methods for the suppression of combustion oscillations in heavy-duty gas turbines featuring lean premixed combustion:Modifications of the burner exit nozzle are implemented in order to avoid fluiddynamic feedback and to change the acoustic behavior of the flame.An asymmetric circumferential distribution of flames with different thermoacoustic responses serves to avoid or at least attenuate the self-excitation within the combustor in multiburner systems.In some applications, these methods are successfully coupled with an active system for the suppression of combustion instabilities (AIC) to further extend the operation envelope.Field demonstrations in different Siemens gas turbines serve to demonstrate the benefit and flexibility of these measures for practical gas turbine combustion systems.Copyright

Burner Development for Flexible Engine Operation of the Newest Siemens Gas Turbines

The newest Siemens gas turbine family has already been well received by the market. Nevertheless, the market drives continuing development of the family and the combustion system. Central focus is put on further increasing reliability and component lifetime and on increased inspection cycles, as well as increasing the engine power output and efficiency, which is directly linked to higher turbine inlet temperatures. Increasing attention, however, is given to the flexibility concerning fuel quality and according fluctuations. Additionally, more and more strict emission requirements must be considered. This paper especially reports on demonstration of the capability of the Siemens gas turbines with an annular combustion system to fulfil the requirements for the highest operational flexibility. Thus, the combustion system has been tested and qualified for the highest operating flexibility with special fuel requirements such as burning Naphtha, Light Oil #2 and Natural gas with an extremely wide range of heating values as well. Also special operation modes such as fuel changeover, fastest load changes for island grid operation, frequency response and load rejection require this highly flexible combustion system without any hardware exchange. In different frames when fired with natural gas, base load is reached with the NOx emissions ranging well below 25 ppmvd, confirming the high potential of this advanced hybrid burner. In liquid fuel operation, dry NOx emissions of 75ppmvd were demonstrated but by injecting fuel / water emulsion NOx emissions were reduced to below 42 ppmvd with different liquid fuel qualities. Combustion dynamics, unburned Hydrocarbons, CO and soot emissions remained always below the required limits.Copyright