INTERNAL HYDRAULIC LOSS IN A SEALLESS CENTRIFUGAL GYRO PUMP

A new index ''loss factor Z'' defined by Eq. 1 was introduced as the absolute expression of the mock loop resistance for testing a nonpulsatile pump. Z = 2g/gamma DELTAP/Q2 (1) where gamma is specific gravity of the fluid, g is the acceleration of gravity, DELTAP is total pressure 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 various rotary blood pumps are proposed in this paper: namely, differential loss factor DELTAZ, and loss factor sensitivity partial derivative Z/partial derivative A. The proposed Z-Q curves demonstrated better performance mapping than the conventional DELTAP-Q curves. DELTAZ is the difference between the Z-Q curves of two different pumps. A is a design parameter of the pump; therefore partial derivative Z/partial derivative A is a quantitative expression of the effect of the design change on the hydraulic performance. These various indices were used to analyze the internal hydraulic loss of a centrifugal pump (Gyro pump). The relationship between its gap size (rotor casing) and hydraulic performance was assessed quantitatively by these indices. In this paper, the derivation processes and above-mentioned indices are described.