Turbine scroll part structure
In a turbine scroll part structure of a radial turbine, a flow passage 3 of a connecting part between an exhaust gas inlet into a turbine housing 5 and a scroll part 1 is offset along an axis line L 1 of a rotating shaft of a turbine rotor in an amount H, and a cut-out portion P is formed in a tongue portion 2 , which separates the flow passage 3 from a blade side passage 4 through which the exhaust gas flows toward blades 6 , for the exhaust gas to flow from the flow passage 3 into the blade side passage 4.
1. A turbine scroll part structure of a radial turbine configured to rotate a turbine rotor by introducing exhaust gas from a spiral scroll part formed inside a turbine housing radially toward blades of the scroll part to exert a force on the blades, then discharging the gas in an axial direction, wherein
a flow passage of a connecting part between an exhaust gas inlet into the turbine housing and the scroll part is offset along an axis line of a rotating shaft of the turbine rotor, whereby a wall surface exposed to external air is formed in a vicinity of a tongue portion that separates the flow passage from a blade side passage through which the exhaust gas flows toward the blades, so that heat in the vicinity of the tongue portion is dissipated from the wall surface.
2. The turbine scroll part structure according to claim 1 , wherein the wall surface has an axial length changing in accordance with an amount of the offsetting and the offset amount of the flow passage is gradually decreased toward a distal end of the tongue portion.
3. The turbine scroll part structure according to claim 1 , wherein the flow passage is offset by deforming only an inner circumferential side of the spiral shape.
4. The turbine scroll part structure according to claim 1 , wherein, with reference to a line connecting an axis center of the turbine scroll part and the distal end of the tongue portion, the flow passage is offset around the axis center in an amount gradually decreasing toward a distal end of the tongue portion where the offset amount is zero, from an angular position at an angle of substantially 45° toward an exhaust gas inlet side.