Patent ID: 6062819
Filing Date: 2000-05-16
Classification: F04D

Abstract:
A turbomachine having an impeller with a plurality of blades supported by a hub on which said blades are circumferentially spaced and covered by a shroud surface which forms an outer boundary to flow of fluid in a flow passage defining a flow direction between two adjacent blades, characterized in that:said impeller has a configuration such that one of a reduced static pressure difference .DELTA.Cp and a relative Mach number difference .DELTA.M between the hub and the shroud on the suction surface of the blade shows a decreasing tendency along the location of non-dimensional meridional distance m toward the impeller exit and is selected to be not less than a specified value which is dependent on a specific speed Ns of the turbomachines, herein specific speed Ns is defined as Ns=NQ.sup.0.5 /H.sup.0.75, where N is the rotational speed in revolution per minutes, Q is the flow rate at an impeller inlet in cubic meter per minutes, and H is the head in meter representing fluid energy which is imparted to the fluid by the turbomachine;said decreasing tendency of .DELTA.Cp for the turbomachine handling incompressible fluid is arranged such that the reduced static pressure difference between a minimum value .DELTA.Cpm of reduced static pressure difference .DELTA.Cp and a value .DELTA.Cp.sub.m-0.4 of reduced static pressure difference .DELTA.Cp at the location corresponding to non-dimensional meridional distance M.sub.m-0.4 obtained by subtracting non-dimensional meridional distance 0.4 from non-dimensional meridional distance M.sub.m representing said minimum value .DELTA.Cpm is selected to benot less than 0.20 at said specific speed Ns of not more than 280,not less than 0.28 at said specific speed Ns of not more than 400, andnot less than 0.35 at said specific speed Ns of not more than 560; andsaid decreasing tendency of .DELTA.M for the turbomachine handling compressible fluid is arranged such that relative Mach number difference between a minimum value .DELTA.Mm of the relative Mach number difference .DELTA.M and a value .DELTA.M.sub.m-0.4 of the relative Mach number difference .DELTA.M at the location corresponding to non-dimensional meridional distance M.sub.m-0.4 obtained by subtracting non-dimensional meridional distance 0.4 from non-dimensional meridional distance M.sub.m representing said minimum value .DELTA.Mm is selected to be not less than 0.23 at said specific speed of not more than 488.