An essentially tube shaped combustion apparatus for providing a homogeneous combustion of liquid fuels, comprising: a combustion chamber having a plurality of reaction zones (A, B, C), one of which is an injection zone, wherein mixing and evaporation takes place, the other being staged homogenous combustion zones (B, C) for staged homogeneous combustion of evaporated fuel and air, the injection zone being separated from the zone by means of a flow constriction plate for recirculation of hot combustion products into the injection zone; and staged homogeneous combustion zones (B, C) being separated from each other by means of a primary mixing plate; and a high pressure nozzle adapted to inject the fuel into the injection zone of the combustion chamber where the fuel is mixed with air which in operation is continuously introduced axially to the combustion chamber; wherein a radial swirler, comprising a swirler base and swirler elements (4b, 4c) provided as blades protruding inwards in the combustion chamber at an angle and disposed along a circle concentric with the periphery of the swirler base, for mixing fuel and air configured to operate at a swirl number between 0.6-2.5 in combination with the flow constriction plate, where the size of the constriction is such that the ratio of the open diameter (D e) of the constriction to the diameter of the tube shaped combustion apparatus is <0.7, characterized in that, the constriction plate is placed at a distance L1 from the swirler base so that L1/D e > 1; the primary mixing plate being placed downstream from the constriction plate at a distance from the constriction plate so that the ratio L2/L1<1 to allow for maximum mixing in the homogeneous combustion process; and by a secondary mixing plate for reducing the total length of the reactor through increased homogenization and in that the constriction plate is provided with a truncated cone protruding from said plate towards nozzle. a combustion chamber having a plurality of reaction zones (A, B, C), one of which is an injection zone, wherein mixing and evaporation takes place, the other being staged homogenous combustion zones (B, C) for staged homogeneous combustion of evaporated fuel and air, the injection zone being separated from the zone by means of a flow constriction plate for recirculation of hot combustion products into the injection zone; and staged homogeneous combustion zones (B, C) being separated from each other by means of a primary mixing plate; and a high pressure nozzle adapted to inject the fuel into the injection zone of the combustion chamber where the fuel is mixed with air which in operation is continuously introduced axially to the combustion chamber; wherein a radial swirler, comprising a swirler base and swirler elements (4b, 4c) provided as blades protruding inwards in the combustion chamber at an angle and disposed along a circle concentric with the periphery of the swirler base, for mixing fuel and air configured to operate at a swirl number between 0.6-2.5 in combination with the flow constriction plate, where the size of the constriction is such that the ratio of the open diameter (D e) of the constriction to the diameter of the tube shaped combustion apparatus is <0.7, characterized in that, the constriction plate is placed at a distance L1 from the swirler base so that L1/D e > 1; the primary mixing plate being placed downstream from the constriction plate at a distance from the constriction plate so that the ratio L2/L1<1 to allow for maximum mixing in the homogeneous combustion process; and by a secondary mixing plate for reducing the total length of the reactor through increased homogenization and in that the constriction plate is provided with a truncated cone protruding from said plate towards nozzle.