A method and device for controllably combusting combustible material, including a combustion device (10) comprising an elongate combustion tube (12) having an inlet section (14) including an inlet for combustible material, an ignition section (16), including an igniter (20) displaced along a length of the tube from the inlet section to ignite the combustible material, and at least one energy extraction device (32) operatively coupled to the combustion tube and configured to extract energy from combustion of the combustible mixture.