PURPOSE: To prevent hot gas from directly jetting against a wall surface of a housing by a method wherein a guide member for changing the direction of flow of hot gas flowing from a branch pipe is installed inside the housing of hot gas.

CONSTITUTION: A guide member 31 is supported inside a housing 5. A plate 33 is integrally formed at an upper part of the guide member 31 through a shaft 32. A groove 34 to which the plate 33 is loosely fitted is formed at an inner circumferential surface of a flat surface 5A of a housing 5. After ignition at a combustion device, jet hot gas driving a turbine is made to flow from the branch pipe 15 into the housing 5, strikes the guide member 31 to change the flow at nearly perpendicular direction and further flows toward openings at both ends of the housing 5. The gas flow does not directly impinge the inner circumferential surface of the housing 5, so that the temperature difference between the inner circumferential surface and the outer circumferential surface of the housing 5 is not increase and then it is possible to prevent a local heat stress from being generated at the housing 5. Although the housing 5 and the guide member 31 have different coefficients of thermal expansion, the plate 33 is fitted to the groove 34 with a predetermined clearance being left therein and then the variation in size caused by expansion is accommodated.