Multi-stage turbocharging assembly

1. A multi-stage turbocharging assembly, comprising

a high-pressure stage comprising a high-pressure turbine coupled with a high-pressure compressor;

a low-pressure stage comprising a low-pressure turbine coupled with a low-pressure compressor; and

a casing enclosing the high-pressure stage and the low-pressure stage, wherein the casing is a single unit;

wherein the casing comprises a flow optimized passage between a high-pressure turbine outlet of the high-pressure turbine and a low-pressure turbine inlet of the low-pressure turbine.

2. The multi-stage turbocharging assembly of claim 1 , wherein the casing comprises at least one of:

a first flange for connecting a silencer, an inlet casing, or an inlet pipe to a low-pressure compressor inlet,

a second flange for connecting an inlet casing or inlet pipe to a high-pressure compressor inlet of the casing,

a third flange for connecting an exhaust gas outlet for providing exhaust gas from the low-pressure turbine to the outside of the casing, and

a fourth flange for connecting an exhaust gas inlet for providing exhaust gas from an engine towards the high-pressure turbine inside the casing.

3. The multi-stage turbocharging assembly of claim 1 , wherein the casing comprises an inner casing and an outer casing, wherein an intermediate space is provided between the inner casing and the outer casing, and wherein the intermediate space is configured for providing a coolant.

4. The multi-stage turbocharging assembly of claim 3 , wherein the casing comprises a coolant inlet for providing coolant into the intermediate space and a coolant outlet for removing coolant from the intermediate space.

5. The multi-stage turbocharging assembly of claim 3 , wherein the intermediate space is a continuous space provided around the high-pressure stage and the low-pressure stage.

6. The multi-stage turbocharging assembly of claim 1 , wherein the casing is an integrated single piece structure of casted material.

7. The multi-stage turbocharging assembly of claim 1 , wherein the high-pressure stage is arranged below the low-pressure stage.

8. The multi-stage turbocharging assembly of claim 1 , wherein the high-pressure stage is configured to have an inversed or same rotational direction compared to a rotational direction of the low-pressure stage during operation of the multi-stage stage turbocharging assembly.

9. The multi-stage turbocharging assembly of claim 1 , wherein the casing comprises at least one of:

a low-pressure compressor outlet for providing low-pressure air to an intercooler, and

a high-pressure compressor outlet for providing high-pressure air to a charge air cooler.

10. The multi-stage turbocharging assembly of claim 1 , wherein the casing comprises at least one of an air-wastegate for providing a device for limiting the charge air pressure, and an exhaust gas wastegate ( 185 , 186 , 187 , 188 ) for providing a device for limiting the charge air pressure.

11. The multi-stage turbocharging assembly of claim 1 , wherein the casing comprises a by-pass system for providing a device to change the operating point in the compressor map.

12. The multi-stage turbocharging assembly of claim 1 , wherein the casing provides elements which assure the containment safety.

13. The multi-stage turbocharging assembly of claim 1 , wherein the casing has surfaces that are in contact with at least one of air and exhaust gas and the surfaces are at least one of treated and designed in such a way, that the casings are consisting of at least two different materials.

14. The multi-stage turbocharging assembly of claim 1 , wherein the low-pressure stage is arranged below the high-pressure stage.

15. The multi-stage turbocharging assembly of claim 1 , wherein the high-pressure stage is configured to have a same rotational direction compared to a rotational direction of the low-pressure stage during operation of the multi-stage turbocharging assembly.