Uwe Gruschka

CFD Prediction of Partload CO Emissions Using a Two-Timescale Combustion Model

Todays and future electric power generation is characterized by a large diversification using all kind of sources, including renewables resulting in noncoherent fluctuations of power supply and power usage. In this context, gas turbines offer a high operational flexibility and a good turn down ratio. In order to guide the design and down select promising solutions for improving partload emissions, a new combustion model based on the assumption of two separate timescales for the fast premixed flame stabilization and the slow post flame burnout zone is developed within the commercial computational fluid dynamics (CFD) code ANSYS CFX. This model enables the prediction of CO emissions generally limiting the turn down ratio of gas turbines equipped with modern low NO x combustion systems. The model is explained and validated at lab scale conditions. Finally, the application of the model for a full scale analysis of a gas turbine combustion system is demonstrated.

CFD-analysis of reacting flow in an annular combustor

Computational Fluid Dynamics (CFD) is increasingly applied in industry due to its capability to provide early detailed information of different technical design variants. Three examples of CFD analysis are outlined in this paper. In the first, the non-reacting flow through the hybrid burner is investigated. At the burner outlet a quite good agreement between measurements and predictions of the swirl flow have almost been found. Deviations are found near the burner axis for the swirl velocity component which can be explained by a weak turbulence representation of the k-e model. In the second example, the reacting flow of the premixed flame in the annular combustor has been analysed. Special emphasis has been put on the convective wall heat transfer. It has been pointed out that the purge air discharged through the gaps between the tiles significantly reduces the convective wall heat load. In the third example, the reacting flow of the diffusion flame in the annular combustor has been investigated using three different flame models. It could be shown that the calculated convective wall heat load does not depend on the formulation of the flame model.

V64.3A Gas Turbine Natural Gas Burner Development

From the very first beginning of the V64.3A development the HR3 burner was selected as standard design for this frame. The HR3 burner was originally developed for the Vx4.2 and Vx4.3 fleet featuring silo combustors in order to mitigate the risk of flashback and to improve the NOx-emissions (Prade, Streb, 1996). Due to its favourable performance characteristics in the Vx4.3 family the advanced HR3 burner was adapted to the Vx4.3A series with annular combustor (hybrid burner ring – HBR). This paper reports about the burner development for V64.3A gas turbines to reach NOx emissions below 25 ppmvd and CO emissions below 10 ppmvd. It is described how performance and NOx emissions have been optimised by implementation of fuel system and burner modifications. The development approach, emission results and commercial operation experiences as well are described. The modifications of the combustion system were successfully and reliably demonstrated on commercially running units. NOx emissions considerably below 25ppmvd were achieved at and above design baseload. An outlook to further steps of V64.3A burner development in the near future will be given in this paper.Copyright