Laser Velocimeter Measurements in a Centrifugal Flow Pump

Abstract

A laser velocimeter was used to measure velocities within the impeller and volute of a centrifugal pump. Measurements were made at four circumferential and eight radial positions. Flow rates ranged from 40 to 105 percent of design flow. Blade-to-blade profiles for the four circumferential positions indicate the flow is circumferentially asymmetric around the pump even at the design flow. Blade-to-blade profiles show normal blade loading for 90 percent of the impeller, with reverse and zero loading occurring in the outer 10 percent of the impeller for design flow. Reversed blade loading over greater portions of the impeller is seen at off-design flow. At 40 percent of design flow, recirculating flow within the impeller was found. Axial traverses across the impeller show the radial velocity profile skewed toward the hub surface at the inlet and away from the hub surface at the exit. The stagnation point on the tongue moved from the outside to the inside as the flow rate was increased from 40 to 105 percent of design. Values for slip range from 0.96 to 0.71 from the inlet to the exit.

Laser Velocimetry Measurements in a Double Volute Centrifugal Pump

“…On the contrary, measurements by Miner et al (1989) showed incipient recirculation in the single volute at design flow in the proximity of the tongue, and extensive recirculation for 40% design flow at window 6.…”

“…First, the flow was assumed to be uniform over eight equal sized sectors (defined as Distribution 1). Second, experimental investigations, such as those performed by Brownell and Flack (1984) and Miner et al (1989), are indicative of narrower regions of recirculation in the proximity of the tongue. Because the influence of the cutwaters is localized and less than 1/8 of the exit flow area is affected, each of the sectors near the cutwaters were considered to encompass only 1/16 of the area, which is consistent with the observations of Brownell and Flack and Miner et al, while 'the adjacent sectors were considered as 5/32 of the area (Distribution 2).…”

“…20, where slip factor values calculated from data by Miner et al (1989) Busemann (1928) and Wiesner (1967) for this pump geometry are 0.76 and 0.80, respectively. Miner et al (1989) calculated the slip factor for the single volute geometry using an average radial velocity, Cr (averaged circumferentially and axially), in place of Q/2"rrrb. The value of slip factor using this method was within 5% of the value reported in this paper.…”

“…The pump used for this study is documented in Hamkins and Flack (1987), Miner et al (1989) indicated that the flow was swirl free three diameters upstream at shut off conditions. The second flow straightener, 9 pipe diameters upstream of the orifice meter, conditions the flow for the orifice plate.…”

Optical PIV and LDV Comparisons of Internal Flow Investigations in SHF Impeller

“…A number of authors have treated this kind of problem like Miner et al [1] for the case of volute. Liu et al [2], Inoue and Cumpsty [3], and Arndt et al [4] have been concerned with the influence of vaned diffuser.…”