Fuel injection method

Method for fuel injection in a sequential combustion system comprising a first combustion chamber and, downstream thereof, a second combustion chamber, in between which a premixing chamber having a longitudinal axis comprising at least one vortex generator, as well as downstream of the vortex generator a mixing section and a fuel lance having a vertical portion and a horizontal portion parallel to the longitudinal axis provided within said mixing section is located, wherein the fuel has a calorific value of 5-20MJ/kg and wherein in said mixing section the fuel and an oxidizing stream coming from the first combustion chamber are premixed to a combustible mixture, the method comprising:

• injecting the fuel in such a way that the residence time of the fuel in the mixing section is reduced in comparison with a radial injection of the fuel from the horizontal portion of the fuel lance, wherein an angle between a fuel jet injected from the horizontal portion of the fuel lance and the longitudinal axis is between 10 and 85 degrees, with respect to the longitudinal axis of the premixing chamber, wherein hot gases entering the premixing chamber are swirled upstream of the fuel lance by the at least one vortex generator and wherein the mixing section is situated downstream of the fuel lance and upstream of the combustion chamber respective of a cross-sectional jump of the combustion chamber.