In cooperation with Purdue University, a subsonic turbine for a rotating detonation test rig was developed. This work is focused on the design of the stator. The test rig is equipped with a cooling jacket downstream of the combustion chamber. This component consists of several slots, where cooling mass flow is added to the main stream, building a cooling film that protects the walls from high temperatures. As part of the project, this component is analyzed and the cooling mass flow needed is determined with computational fluid dynamic simulations.