Shrouded impeller made by additive manufacturing and including voids in the hub and in the shroud

1. A closed turbocompressor impeller, said closed turbocompressor impeller comprising:

a hub having an outer surface comprising a top portion and a bottom portion;

a set of blades provided on said hub;

a shroud provided on top of the blades; and

a sealing surface for a back seal provided at a back side of the closed turbocompressor impeller,

wherein said hub is provided with a part with a first internal cavity, wherein said first internal cavity is in fluid communication with a back part of the impeller, or with an inlet of the impeller, or with an arbitrary location in the impeller channels that extend between the blades, wherein said first internal cavity has a sloping top wall with respect to a central axis of the impeller, said sloping top wall forming the bottom portion of the outer surface of the hub and extends from the top portion towards the sealing surface at the back side of the closed turbocompressor impeller, wherein said top portion and the bottom portion of the outer surface of the hub are configured to be exposed to the outlet pressure during operation, and

wherein the shroud comprises a second internal cavity, and wherein the second internal cavity is in fluid communication with the inlet of the impeller.

2. The closed turbocompressor impeller according to claim 1 , wherein the second internal cavity is provided in a front part of the shroud at the inlet.

3. The closed turbocompressor impeller according to claim 1 , wherein the impeller is further provided with channels that are designed such that they enable the removal of unmelted metal powder.

4. The closed turbocompressor impeller according to claim 1 , wherein the impeller is further provided with pressure equalization channels that are designed such that they provide a corresponding pressure in the first and second internal cavity.

5. The closed turbocompressor impeller according to claim 1 , wherein the impeller is made by means of one or more additive manufacturing techniques.

6. The closed turbocompressor impeller according to claim 5 , wherein the impeller is made of metal.

7. The closed turbocompressor impeller according to claim 5 , wherein the impeller is made as a single component.

8. The closed turbocompressor impeller according to claim 1 , wherein a maximum value of an angle between the sloping top wall and the central axis of the impeller is 45°.

9. The closed turbocompressor impeller according to claim 1 , wherein said first internal cavity is separated from said second internal cavity, said first internal cavity is provided with a first channel, and said second internal cavity is provided with a second channel.

10. A method for manufacturing a closed turbocompressor impeller with a hub and a shroud by additive manufacturing, wherein this method comprises a step of:

providing one or more internal cavities in the hub and/or the shroud by additive manufacturing, wherein a first internal cavity is brought in fluid communication with a back part of the impeller, or with an inlet of the impeller, or with an arbitrary location in the impeller channels that extend between the blades, and a second internal cavity is brought in fluid communication with the inlet of the impeller, and

forming a sloping top wall on the first internal cavity with respect to a central axis of the impeller, wherein said sloping top wall forms a bottom portion of an outer surface of the hub and extends from a top portion of the outer surface of the hub towards a sealing surface for a back seal provided at a back side of the closed turbocompressor impeller, wherein said top portion and the bottom portion of the outer surface of the hub are configured to be exposed to the outlet pressure during operation.

11. The method according to claim 10 , wherein the impeller is constructed in layers, whereby the method further comprises the steps of:

manufacturing the impeller whereby an intermediate support lattice is incorporated between the shroud and the hub;

removing of excess metal powder; and

removing of the intermediate lattice support structure.

12. The method according to claim 11 , wherein the method further comprises the step of processing the impeller on its outer surface.