Multi-stage electric centrifugal compressor

A multi-stage electric centrifugal compressor, comprising:

• a rotational shaft;
• a low-pressure-stage impeller disposed at one end of the rotational shaft;
• a high-pressure-stage impeller disposed at another end of the rotational shaft;
• a high-pressure-stage housing accommodating the high-pressure-stage impeller;
• an electric motor configured to drive the low-pressure-stage impeller and the high-pressure-stage impeller;
• and
• a connecting pipe for supplying a compressed gas compressed by the low-pressure-stage impeller to the high-pressure-stage housing,
• wherein the high-pressure-stage housing has a high-pressure-stage inlet opening that opens in a first direction intersecting an axis of the rotational shaft,
• wherein the connecting pipe includes a high-pressure-stage-side connection portion connected to the high-pressure-stage inlet opening, and
• wherein a flow path cross-section perpendicular to an extending direction of an axis of the high-pressure-stage-side connection portion has a longitudinal direction along a direction perpendicular to the axis of the rotational shaft, and includes concavely curved portions formed at both ends in the longitudinal direction of the flow path cross-section of the high-pressure-stage-side connection portion.