A combustion device for an electricity production or energy cogeneration apparatus, said apparatus comprising a gas turbine, in particular a micro gas turbine supplied by said device, the combustion device being suitable for a flameless combustion regime, and comprising: - an outer tube ; - a combustion tube forming a combustion zone for flameless combustion of a mixture of oxidizing air and fuel, the combustion tube being concentric with the outer tube , in communication with fuel-injection means and air-injection means arranged at a first end of the combustion tube , referred to as a front end, and which is closed by an end wall at a second end of the combustion tube, referred to as a rear end, said end wall being integral with and sealed to said combustion tube ; - the fuel-injection means comprising at least a first orifice , referred to as a fuel-injection orifice; - the air-injection means comprising at least a second orifice , referred to as an air-injection orifice; - means for discharging combustion gases; - a closure wall covering the front end of the combustion tube and connected to the air-injection and fuel-injection means, - the combustion tube being substantially a cylinder with a single internal volume configured to allow the combustion gases to recirculate in the flameless combustion regime, - the means for discharging the combustion gases comprising at least one opening arranged at the front end of the combustion tube , which is substantially cylindrical in shape, said opening being delimited on one side by an end of the longitudinal cylindrical wall of the combustion tube proximal to the closure wall and on the other side by said closure wall , with the flow and evacuation of combustion gases being ensured between said longitudinal wall and the external tube ; characterized by a tubular sleeve arranged concentrically between the combustion tube and the outer tube , connected to the closure wall and positioned facing the opening of the evacuation means so as to form an annular combustion zone , to extend a residence time of the combustion gases exhausted via the opening . - an outer tube ; - a combustion tube forming a combustion zone for flameless combustion of a mixture of oxidizing air and fuel, the combustion tube being concentric with the outer tube , in communication with fuel-injection means and air-injection means arranged at a first end of the combustion tube , referred to as a front end, and which is closed by an end wall at a second end of the combustion tube, referred to as a rear end, said end wall being integral with and sealed to said combustion tube ; - the fuel-injection means comprising at least a first orifice , referred to as a fuel-injection orifice; - the air-injection means comprising at least a second orifice , referred to as an air-injection orifice; - means for discharging combustion gases; - a closure wall covering the front end of the combustion tube and connected to the air-injection and fuel-injection means, - the combustion tube being substantially a cylinder with a single internal volume configured to allow the combustion gases to recirculate in the flameless combustion regime, - the means for discharging the combustion gases comprising at least one opening arranged at the front end of the combustion tube , which is substantially cylindrical in shape, said opening being delimited on one side by an end of the longitudinal cylindrical wall of the combustion tube proximal to the closure wall and on the other side by said closure wall , with the flow and evacuation of combustion gases being ensured between said longitudinal wall and the external tube ; <EOS>