Correlation and prediction of efficiency of centrifugal pumps due to tip clearance effects

A wide range of specific speeds (n, = 17-80), based on five centrifugal pumps, was experimentally analysed to study the performance deterioration associated with tip clearance effects. Consequently and systematically, an empirical expression was developed that pre-dicted the efficiency deterioration as a function of speciJlc speed and t i p clearance within a fairly good margin. Key words: specific speed, tip clearance effects, centrifugal impellers, turbomachinery NOTATION area width absolute velocity impeller diameter pump head speed (r/min) specific speed = (nQ'")/H3'" non-dimensional specific speed power flowrate radius tangential velocity clearance elasticity efficiency clearance ratio = 6/b, slip factor density flow coefficient head coefficient Subscripts 1 at pump inlet 2 at pump exit m meridional opt optimun u tangential