A pulse detonation engine for the combustion of a mixture of biogas and hydrogen, comprising a valve assembly and a combustion chamber connected to the valve assembly, the combustion chamber comprising a detonation initiation means and a first flue gas outlet, characterised in that the valve assembly comprises: a. a suction diffuser for supplying combustion air, wherein the suction diffuser is in the shape of de Laval nozzle with a variable, converging-diverging circular cross-section and extends along the direction of a longitudinal axis, wherein the circular cross-section of the suction diffuser is narrower in a central portion thereof than in an end portion thereof facing the combustion chamber; b. a fuel supply tube for supplying fuel, extending through the centre of the suction diffuser in the direction of the longitudinal axis and leading to the combustion chamber; c. a baffle arranged outside the fuel supply tube and co-axially relative to the longitudinal axis, wherein the baffle is in the shape of a cone or a truncated cone, the base of which is oriented towards the end portion of the suction diffuser; d. an air curtain arranged outside the fuel supply tube and adjacent to the end portion of the suction diffuser and to the base of the baffle such that it is arranged perpendicular to the longitudinal axis, wherein the air curtain comprises perforations (31, 32) for air supply; e. a support plate arranged outside the fuel supply tube and at a distance from the air curtain in the direction of the longitudinal axis such that it is arranged perpendicular to the longitudinal axis, wherein the side of the support plate adjacent to the air curtain is of a concave shape or of a shape narrowing towards the circumference of the support plate; and f. a valve arranged outside the fuel supply tube and between the air curtain and the support plate such that it is arranged perpendicular to the longitudinal axis, wherein the valve is in the shape of an n-polygon or a circle with an opening for the fuel supply tube in the centre and with a circular base around the perimeter of the opening, wherein the valve is divided from a circumferential part towards the circular base into n shutters of an essentially trapezoidal shape, each short base of said trapezoids being firmly or integrally connected to the circular base and each long base of said trapezoids forming the circumferential part of the valve, wherein the shutters of the valve are bendable such that in a closed position of the valve, the shutters are adjacent to the air curtain, thus overlapping the perforations (31, 32) and blocking air supply into the combustion chamber as well as expansion of flue gases into the suction diffuser, and in an open position of the valve, the shutters are adjacent to the support plate, thereby leaving the perforations (31, 32) open and allowing air to flow into the combustion chamber. a. a suction diffuser for supplying combustion air, wherein the suction diffuser is in the shape of de Laval nozzle with a variable, converging-diverging circular cross-section and extends along the direction of a longitudinal axis, wherein the circular cross-section of the suction diffuser is narrower in a central portion thereof than in an end portion thereof facing the combustion chamber; b. a fuel supply tube for supplying fuel, extending through the centre of the suction diffuser in the direction of the longitudinal axis and leading to the combustion chamber; c. a baffle arranged outside the fuel supply tube and co-axially relative to the longitudinal axis, wherein the baffle is in the shape of a cone or a truncated cone, the base of which is oriented towards the end portion of the suction diffuser; d. an air curtain arranged outside the fuel supply tube and adjacent to the end portion of the suction diffuser and to the base of the baffle such that it is arranged perpendicular to the longitudinal axis, wherein the air curtain comprises perforations (31, 32) for air supply; e. a support plate arranged outside the fuel supply tube and at a distance from the air curtain in the direction of the longitudinal axis such that it is arranged perpendicular to the longitudinal axis, wherein the side of the support plate adjacent to the air curtain is of a concave shape or of a shape narrowing towards the circumference of the support plate; and f. a valve arranged outside the fuel supply tube and between the air curtain and the support plate such that it is arranged perpendicular to the longitudinal axis, wherein the valve is in the shape of an n-polygon or a circle with an opening for the fuel supply tube in the centre and with a circular base around the perimeter of the opening, wherein the valve is divided from a circumferential part towards the circular base into n shutters of an essentially trapezoidal shape, each short base of said trapezoids being firmly or integrally connected to the circular base and each long base of said trapezoids forming the circumferential part of the valve, wherein the shutters of the valve are bendable such that in a closed position of the valve, the shutters are adjacent to the air curtain, thus overlapping the perforations (31, 32) and blocking air supply into the combustion chamber as well as expansion of flue gases into the suction diffuser, and in an open position of the valve, the shutters are adjacent to the support plate, thereby leaving the perforations (31, 32) open and allowing air to flow into the combustion chamber.