FLOW DUCT OF AN AXIAL-FLOW HYDRAULIC MACHINE

摘要

FLOW DUCT OF AN AXIAL-FLOW HYDRAULIC MACHINE A B S T A C T The flow duct of an axial-flow hydraulic machine is defined by a casing of which the internal surface is of a complex geometrical form. The casing defines an inflow or inlet portion, a portion accommodating the blase system, adjoining the inflow portion, and an outflow or outlet portion directly adjoining the portion accommodating the blade system, downstream thereof. The inner surface defining the inflow portion is made in the form of at least one truncated rectangular pyramid wit the greater cross-section facing the inlet, the cross-section perpendicular to the axis of the flow duct being of substantially rectangular form with rounded-off corners, the rounding radius of these corners increasing to the value of the radius of the circle defining the cross-section of the inlet of the portion accommodating the blade system. The last-- -mentioned portion has circular form of its cross-sections perpendicular to the axis of the flow duct. The internal surface defining the outflow portion is made in the form of as at least one truncated rectangular pyramid its the greater cross -section facing the outlet, the cross-sections perpendicular to the axis of the flow duct being of a substantially rectangular form with rounded-off corners with the rounding radius. decreasing lengthwise of the outflow portion from the value of the radius of the circle defining the outlet cross-section of the portion accommodating the blade system. An axial-flow turbine of the capsule type with the flow duct according to the present invention and an adequately developed blade system with 16 wicket gates of a height equalling 0.4 of the runner diameter, the latter being of a four-blade type, 7.5 m in diameter, operated t a 35 feed head, offers as much as 94.3% efficiency.