This figure, taken from Mayer and Paynter (1994), depicts experimental sonic mass flow coefficient data (Qsonic) as a function of the ratio of plenum static pressure (pplenum) to local boundary layer total pressure (pt plenum). The first set of data, obtained by McLafferty and Ranard (1958), is for a bleed hole angle of 20° relative to the local flow velocity. The second set of data, obtained by Syberg and Hickox (1972), is for a bleed hole angle of 90°. Both sets of data show a decrease in Qsonic as the pressure ratio increases. The values for Qsonic are generally larger, indicating fewer losses, for flows with a lower local boundary layer edge Mach number.
Last updated 31 Oct 2011