Superior fuel and operational flexibility of sequential combustion in Ansaldo Energia gas turbines

Abstract

The increasing use of renewables for energy production is also accompanied by an increasing need for flexible power production, while aiming at carbon free emissions. The potential solutions of energy storage of excess generation from renewables through hydrogen production and precombustion carbon capture are gaining momentum. Both scenarios require gas turbines capable of operation with hydrogen-based fuels. At the same time, the composition of natural gas considered for use within gas turbines is becoming significantly more variable due to increased use of liquefied natural gas and a wider range of gas sources and extraction methods. Fuel flexibility, both in terms of the amount of hydrogen and higher hydrocarbons is therefore of utmost importance in modern gas turbine development. This paper provides an overview of key steps taken in the design and development of an operation concept, leveraging the advantage of the GT36 Constant Pressure Sequential Combustion system (CPSC)a premixed low emission reheat combustion technology, characterised by an extremely broad fuel range capability, composed of two combustion stages in series. The results presented in this paper clearly show that the complementarity behaviour of first and second combustion stagesextensively proven for fuels containing high concentrations of higher hydrocarbonscan be extended to hydrogen. Ultimately, this allows the achievement of ultra-low emissions at full combustor exit temperature maintaining the power and efficiency performance of F and H class engines. Recent validation performed at the high pressure combustion facility at DLR-Cologne, proved fuel flexibility with minimal or no de-rating with hydrogen contents from 0 to 50% in volume, without any modification of the standard GT36 hardware. Based on the current studies, the flexibility of the GT36 CPSC system is envisaged to enable a further increase in hydrogen content allowing this H class engine to be operated with 100% hydrogen.

Effect of Mixing on the Anchoring and Combustion Regimes of Pure Hydrogen Flames in Sequential Combustors

“…The GT36 machines are based on a can combustor layout for best upgradability, faster serviceability and maintenance; instead of a high pressure turbine, the hot gases from the first stage are diluted with air from the compressor [4]. Sequential combustion systems as deployed in the GT26 and GT36 engines and the corresponding advantages for fuel flexibility and hydrogen combustion at low emissions are thor- oughly described in [5][6][7][8][9]. While sequential combustors are particularly suited for the combustion of hydrogen-based fuels, there are knowledge gaps regarding the understanding of the combustion regime transitions, when the hydrogen fuel fraction and the thermo-chemical condition of the vitiated flow entering the sequential stage are changed.…”

Effect of plasma-flow coupling on the ignition enhancement with non-equilibrium plasma in a sequential combustor

“…Sequential combustion at constant pressure is a substantial technological breakthrough in the field of ground-based gas turbines for a power generation, as it significantly improves the operational and fuel flexibility [1,2]. In this combustor architecture, the hot products from the first stage operated at lean conditions are diluted with air and flow through the sequential stage in which sequential fuel is injected.…”

“…Furthermore, as indicated in [2], it is foreseen that 100% H 2 combustion can be achieved without derating the performances of the gas turbine with this concept. However, further technology development is required to attain this goal, especially when fast transients of the operating conditions are considered.…”

Numerical study of ignition and combustion of hydrogen-enriched methane in a sequential combustor

“…A new type of combustor architecture for heavy duty gas turbines has emerged recently: the Constant Pressure Sequential Combustor (CPSC) [1]. This technology is a step forward in the design of operationally-and fuelflexible [2,3] gas turbines that can cope with both the intrinsically intermittent nature of renewable energy production and with the increasing demand in the power generation sector to burn different fuel blends, and in particular blends incorporating a large amount of sustainably produced hydrogen. The CPSC concept consists of two technically premixed flames burning in series.…”