Abstract: A turbofan includes a circular end plate, a ring-shaped shroud facing the end plate, and a plurality of blade members disposed between the end plate and the shroud. An annular portion of a space between the end plate and the shroud where the blade members are disposed is a pressure-increase flow path. The turbofan causes air to flow from an inner peripheral side to an outer peripheral side of the pressure-increase flow path. A cross-sectional area of the pressure-increase flow path increases gradually from an upstream end toward a downstream end of the pressure-increase flow path.

Abstract: A turbofan includes a circular end plate, a ring-shaped shroud facing the end plate. and a plurality of blade members disposed between the end plate and the shroud. An annular portion of a space between the end plate and the shroud where the blade members are disposed is a pressure-increase flow path. The turbofan causes air to flow from an inner peripheral side to an outer peripheral side of the pressure-increase flow path. A cross-sectional area of the pressure-increase flow path increases gradually from an upstream end toward a downstream end of the pressure-increase flow path.

Abstract: In a centrifugal fan, when an angle defined by a tangential line to a camber line at an intersection point between the camber line and an arc around a rotation axis, and a tangential line to the arc at the intersection point on a blade cross section passing a front edge and a rear edge of a blade is a blade angle, the blade has at least one of a decreasing shape and a fixed shape. The decreasing shape is such that the blade angle decreases as the intersection point is shifted toward the rear edge on the camber line on a front edge side portion of a shroud side blade cross section. The fixed shape is such that the blade angle is fixed, even if the intersection point is shifted toward the rear edge on the camber line on the front edge side portion of the shroud-side blade cross section.

Abstract: In a centrifugal fan, when an angle defined by a tangential line to a camber line at an intersection point between the camber line and an arc around a rotation axis, and a tangential line to the arc at the intersection point on a blade cross section passing a front edge and a rear edge of a blade is a blade angle, the blade has at least one of a decreasing shape and a fixed shape. The decreasing shape is such that the blade angle decreases as the intersection point is shifted toward the rear edge on the camber line on a front edge side portion of a shroud side blade cross section. The fixed shape is such that the blade angle is fixed, even if the intersection point is shifted toward the rear edge on the camber line on the front edge side portion of the shroud-side blade cross section.