Philipp Brunner

Development of the Sequential Combustion System for the ABB GT24/GT26 Gas Turbine Family

The 60Hz, 165MW gas turbine GT24 and the 50Hz, 240MW gas turbine GT26 are the first two members of ABB’s Sequential Combustion System gas turbine family. These turbines are designed to offer increased output at up to 4% efficiency advantage over today’s engines. Whereas the first combustor is based on the proven EV-combustor technology, an extensive research and development program has been carried out in developing the lean premixed, self-igniting second combustor.This paper reports the basic research work concerning the lean premixing burners with self-ignition. The development of the burner and the combustor was based on wind tunnel and water channel experiments, CFD-calculations and combustion tests at atmospheric and high pressure.Moreover an innovative cooling technology was developed to fullfill all conditions of the self-igniting premix combustor requiring minimal cooling air consumption. Special attention was paid both to a low sensitivity of the cooling effectiveness to variations of the imposed boundary conditions and to a robust hardware construction.Tests of real engine parts at real engine conditions will be demonstrated in detail. Finally the paper demonstrates the potential of the sequential combustion system to reach single digit NOx levels by unveiling the results of the extensive testing program.Copyright

Vortex Generators in Lean-Premix Combustion

A novel fuel-air mixing technique on the basis of vortex generators has been developed and successfully implemented in the worlds first lean-premix reheat combustor of ABBs GT24/GT26 series industrial gas turbines. This technique uses a special arrangement of delta-wing type vortex generators to achieve rapid mixing through longitudinal vortices, which produce low pressure drop and no recirculation zones along the mixing section. In this paper, after a short introduction to the topic, the motivation for utilizing vortex generators and the main considerations in their design are explained. A detailed analysis of the flow field, pressure drop and the strength of the vortices generated by a single vortex generator are presented as one of the three main geometrical parameters is varied. The results obtained through water model tests indicate that an optimum vortex generator geometry exists, which produces the maximum circulation at a relatively low pressure drop price. Moreover, the axial velocity distribution along the mixing section stays uniform enough to assure flash-back free operation despite the elevated inlet temperatures encountered in a reheat combustor. After selecting this optimized geometry, the process of the arrangement of multiple vortex generators in an annular combustor segment is described. The optimum arrangement presented here is suitable both for gaseous and liquid fuel injection, since it requires only one injection location per combustor segment.

Field Experience of the Sequential Combustion System for the GT24/GT26 Gas Turbine Family

The first units of the Sequential Combustion System gas turbine family are in commercial operation. The first gas turbine GT24 (60Hz, 165MW-class) started the commercial operation, while the first GT26 (50Hz, 265MW-class) demonstrates its performance at the GT test facility. More engines are presently in the commissioning phase or will be in the near future. These turbines are designed to offer increased output at high GT efficiency. To acheive this, the sequential combustion system, a reheat process with two combustors, has been developed. Whereas the first combustor is based on the proven EV-combustor technology, extensive research and development efforts have been carried out in developing the lean premixed self-igniting second combustor (SEV).This paper is a follow-up of the ASME paper 96-GT-315, which described the basic research work concerning the lean premixing SEV-burners with self-ignition. The present paper reports the experience gained during commissioning of the first engines.The performance of the two combustors, as well as the measured emissions, are discussed and compared with the expected values and rig test results.Finally, the potential of the sequential combustion system to reach low NOx levels is demonstrated by unveiling the results of the extensive testing program during the commissioning phase.Copyright