Centrifugal compressor

A centrifugal compressor provided with an impeller which is configured to have a plurality of blades arranged at a predetermined interval in a circumferential direction of a hub rotating together with a rotation shaft,

• wherein a blade angle relative to a meridian plane on a shroud side of the blade distributes to have a minimum value at a position between a leading edge of the blade and a midpoint of a camber line on the shroud side, and a maximum value at a position between the midpoint of the camber line on the shroud side and a trailing edge of the blade;
• wherein the blade angle of the blade relative to the meridian plane on a hub side distributes so as to have a maximum value at a position between a leading edge and a midpoint of a camber line on the hub side;
• wherein if a blade loading at an arbitrary point of the camber line on the shroud side is a derivative of a product of a circumferential average absolute velocity Cθ and a radius r differentiated with respect to a camber line length x as shown by the following formula,
• ⅆ
• (
• r
• ·
• C
• θ
• )
• ⅆ
• x
• where, r is a radius from an axis center of the rotation shaft at an arbitrary point of the camber line on the shroud side, Cθ is a circumferential average absolute velocity of a working fluid flowing in a passage formed in the impeller, and x is a camber line length which is a length measured along the camber line on the shroud side from the leading edge to the arbitrary point of the camber line on the shroud side,
• then the blade angle on the shroud side distributes such that the blade loading has a minimum value at the leading edge, increases from the minimum value along the camber line on the shroud side and reaches a maximum value, and decreases from the maximum value toward the trailing edge along the camber line on the shroud side, while maintaining a magnitude of the minimum value of the blade loading so that a reversed flow of the working fluid at the leading edge is suppressed;
• wherein a distribution of the blade loading along the camber line on the shroud side has an inflection point at which a rate of rise of the blade loading changes or has a folding point where a rate of rise of the blade loading discontinuously increases at a position between a minimum point of the minimum value of the blade loading and a maximum point of the maximum value of the blade loading, the position being between the leading edge and the midpoint of the camber line on the shroud side;
• wherein the blade loading at the inflection point or the folding point is not more than ⅓ of the maximum value of the blade loading;
• and
• wherein the inflection point is a throat position of the blade.