A constant-volume combustion system for a turbomachine comprising: a plurality of combustion chambers distributed in an annular manner about an axis (XX') defining an axial direction (DA), each combustion chamber comprising an intake port and an exhaust port , a selective closure member rotationally movable about the axis with respect to the combustion chambers, the selective closure member comprising a ferrule facing the intake and exhaust ports of the combustion chambers, the ferrule containing on a first annular section at least one intake aperture intended to cooperate with the intake port of each combustion chamber during the rotation of the selective closure member and on a second annular section at least one exhaust aperture intended to cooperate with the exhaust port of each combustion chamber during the rotation of the selective closure member, each intake aperture and each exhaust aperture extending over a determined length in a circumferential direction with respect to the axis, characterized in that each intake aperture and each exhaust aperture are segmented by at least one segment extending in each aperture in the axial direction (DA), in that each segment extends only in the thickness of the wall of the ferrule of the selective closure member, and in that the selective closure member further comprises a wall extending from the internal face of the ferrule in a radial direction (DR) and separating the first and second annular sections of the ferrule, said wall containing at least one bypass aperture extending over an angular area located outside the angular areas over which extend said at least one intake aperture and said at least one exhaust aperture , said at least one bypass aperture being angularly segmented by at least one segment extending in a radial direction with respect to the axis (XX'). a plurality of combustion chambers distributed in an annular manner about an axis (XX') defining an axial direction (DA), each combustion chamber comprising an intake port and an exhaust port , a selective closure member rotationally movable about the axis with respect to the combustion chambers, the selective closure member comprising a ferrule facing the intake and exhaust ports of the combustion chambers, the ferrule containing on a first annular section at least one intake aperture intended to cooperate with the intake port of each combustion chamber during the rotation of the selective closure member and on a second annular section at least one exhaust aperture intended to cooperate with the exhaust port of each combustion chamber during the rotation of the selective closure member, each intake aperture and each exhaust aperture extending over a determined length in a circumferential direction with respect to the axis, characterized in that each intake aperture and each exhaust aperture are segmented by at least one segment extending in each aperture in the axial direction (DA), in that each segment extends only in the thickness of the wall of the ferrule of the selective closure member, and in that the selective closure member further comprises a wall extending from the internal face of the ferrule in a radial direction (DR) and separating the first and second annular sections of the ferrule, said wall containing at least one bypass aperture extending over an angular area located outside the angular areas over which extend said at least one intake aperture and said at least one exhaust aperture , said at least one bypass aperture being angularly segmented by at least one segment extending in a radial direction with respect to the axis (XX'). <EOS>