Two-stage supercharging device
A two-stage supercharger for an engine having a radial high-pressure turbine and an axial low-pressure turbine. The high-pressure turbine has a spiral housing with an exhaust-gas inlet connected to an exhaust line and via which exhaust-gas flows from the engine to the high-pressure turbine. A partial flow of the exhaust-gas flows past the high-pressure turbine in a bypass unit and is adjustable by a shut-off valve. The bypass unit includes a branch line and an annular duct housing integral with the spiral housing. The branch line branches off the exhaust-gas inlet at a point where the shut-off valve is arranged and issues into a duct of the annular duct housing. The partial flow flows through the branch line into the duct and an axially arranged annular gap into an exhaust-gas duct. The partial flow merges with a main exhaust-gas flow from the high-pressure turbine and flows into the low-pressure turbine.
1. A two-stage supercharging device for an internal combustion engine, comprising:
a radial high-pressure turbine with a spiral housing and a high-pressure turbine wheel;
an axial low-pressure turbine having a low-pressure turbine wheel,
wherein the spiral housing comprises an exhaust gas inlet connector, which is connected to an exhaust gas line, via which a primary exhaust gas stream flows from the internal combustion engine to the high-pressure turbine,
wherein the high-pressure turbine and the low-pressure turbine are mounted opposite each other on an axis, and an exhaust gas outlet of the high-pressure turbine is connected fluidically via an exhaust gas channel to an exhaust gas inlet of the low-pressure turbine;
a bypass device that conducts a secondary exhaust gas stream split off from the primary exhaust gas stream around the high-pressure turbine, the bypass device includes a branch line and a ring channel housing, wherein the ring channel housing forms a ring channel, and the branch line opens out into the ring channel, wherein the secondary exhaust gas stream branches off from the primary exhaust gas stream upstream of the high-pressure turbine wheel of the high-pressure turbine, and the ring channel is arranged around the exhaust gas channel downstream from the high-pressure turbine and is connected fluidically to the exhaust gas channel so that the primary exhaust gas stream leaving the high-pressure turbine recombines in the exhaust gas channel with the secondary exhaust gas stream from the bypass device, so that the combined stream flows into the low-pressure turbine; and
a shut off valve is installed in the bypass device,
wherein the spiral housing of the high-pressure turbine and the ring channel housing are formed as only a single piece
wherein a radially outer wall of the ring channel housing is extended to form a connecting flange for a compensator, which is connected to the axial turbine.
2. The supercharging device according to claim 1 , wherein the spiral housing and the ring channel housing are connected to each other at facing surfaces by a common wall area.
3. The supercharging device according to claim 1 , wherein the ring channel defines two circumferential directions, has a largest cross section in an orifice area of the branch line, and, proceeding from the orifice area, the cross section decreases in both circumferential directions of the ring channel to a point on the ring channel located opposite the orifice area of the branch line.
4. The supercharging device according to claim 1 , further comprising a flow guide surface for the primary exhaust gas stream leaving the high-pressure turbine integrated into a component forming the ring channel and the spiral housing.
5. The supercharging device according to claim 1 , wherein the ring channel has an annular gap open toward the low-pressure turbine, and the ring channel is connected fluidically to the exhaust gas channel via the annular gap.
6. The supercharging device according to claim 5 , wherein an outside diameter of the annular gap and an inside diameter of the exhaust gas channel are equal in size to an outside diameter of the low-pressure turbine wheel of the low-pressure turbine.
7. The supercharging device according to claim 1 , wherein the spiral housing of the high-pressure turbine is an integral part of the branch line.
8. The supercharging device according to claim 7 , wherein the branch line branches off from the exhaust gas inlet connector of the spiral housing and is an integral part of the spiral housing.
9. The supercharging device according to claim 8 , wherein the shutoff valve is installed in the branch line.
10. The supercharging device according to claim 9 , wherein the shutoff valve has a flap located in a wall of the exhaust gas inlet connector in an area of a branching point of the branch line and, in a closed state the flap forms a wall for the exhaust gas stream conforming to a contour of the wall of the exhaust gas inlet connector.