Housing structure for a turbomachine, turbomachine and method for cooling a housing portion of a housing structure of a turbomachine

A housing structure for a turbomachine, wherein the housing structure surrounds annularly, at least partially, a main flow channel of the turbomachine, in which rotating blades and guide vanes are arranged, and to delimit the turbomachine with respect to the surroundings, wherein the housing structure comprises an outer housing wall, which is formed by at least one housing part, and an inner wall, and at least one cooling air channel, which extends, at least partially, in a volume between the housing wall and the inner wall, for cooling a housing portion to be cooled of the housing wall,

• wherein the housing wall delimits the turbomachine with respect to the surroundings,
• wherein the inner wall is arranged in the radial direction inside of the housing wall and spaced apart from the housing wall in the radial direction, and bounds, at least partially, the main flow channel together with the rotating blades and the guide vanes arranged therein,
• wherein, in relation to a main flow direction, with which a main flow passes through the main flow channel, the housing portion to be cooled has an upstream end and a downstream end,
• wherein the cooling air channel has a cooling air channel inlet for feeding cooling air into the cooling air channel and a cooling air channel outlet for discharging cooling air from the cooling air channel, and
• wherein the cooling air channel has at least one portion, in which cooling air that is conveyed to the cooling air channel via the cooling air channel inlet flows in the direction of the upstream end of the housing portion to be cooled, wherein the cooling air channel inlet is arranged in the region of the downstream end of the housing portion to be cooled or is arranged downstream of said end.