INTERNAL HYDRAULIC LOSS IN A SEALLESS CENTRIFUGAL GYRO PUMP

A new index ''loss factor Z'' defined by Eq. 1 was introduced as the a bsolute expression of the mock loop resistance for testing a nonpulsat ile pump. Z = 2g/gamma DELTAP/Q2 (1) where gamma is specific gravity o f the fluid, g is the acceleration of gravity, DELTAP is total pressur e head, and Q is flow. Z is expected to be constant, regardless of the pumping parameters. Z values obtained in the same mock loop but with different rotary blood pumps were almost identical and were defined as Z0. New methods of analysis of the flow-restrictive conditions of var ious rotary blood pumps are proposed in this paper: namely, differenti al loss factor DELTAZ, and loss factor sensitivity partial derivative Z/partial derivative A. The proposed Z-Q curves demonstrated better pe rformance mapping than the conventional DELTAP-Q curves. DELTAZ is the difference between the Z-Q curves of two different pumps. A is a desi gn parameter of the pump; therefore partial derivative Z/partial deriv ative A is a quantitative expression of the effect of the design chang e on the hydraulic performance. These various indices were used to ana lyze the internal hydraulic loss of a centrifugal pump (Gyro pump). Th e relationship between its gap size (rotor casing) and hydraulic perfo rmance was assessed quantitatively by these indices. In this paper, th e derivation processes and above-mentioned indices are described.