The effects of air-water two phase flow on the performance of a centrifugal pump
Department of Mechanical Engineering
Master of Science
Raco, Roland J.
Jacobs, Robert M.
Centrifugal pumps --Testing.
This study investigates the performance of a 1-inch long 4-vane open impeller centrifugal pump under two phase flow conditions. The paddle wheel pump, as branded by its manufacturer the Worthington Corporation, had a specific speed of 3400 (based on gallons per minute, feet of water and revolutions per minute) corresponding to a 7-inch impeller diameter. A 1/8-inch perforated steel pipe carried the compressed air to within four inches of the impeller eye where the air was injected into the water stream (See figures 18 and 20).
The three variable inputs were, water flow rate, pump speed and air flow rate. The output parameters measured were discharge, suction pressure, and torque. While measuring the outing parameters, various combinations of the input variables were employed in order to find the maximum air-water volumetric ratio at which water flow stopped and the discharge head dropped to zero.
At the pump speeds and air flow rates ranging from 1500 PPM to 3500 PPM and from 1.72 x 10-3 cubic feet/second to 2.65x10-3 cubic feet/second respectively, it was found that increasing the water flow rate from zero capacity to a certain limit resulted in an increase of the discharge head (See figure 1 to 5). This limiting capacity varied from 40 to 60 per cent of the pump's design capacity (35 GPM at 3500 RPM and 220 feet of water). A further increase of the water flow rate beyond the limiting capacity resulted in a quick drop of the discharge head. This characteristic behavior of the head-capacity curve was particularly noticeable at the higher air flow rates which ranged from 1.72x10-3 cubic feet/second to 2.65 x 10-3 cubic feet/second. It was also observed that at a given pump speed, increasing the volumetric air flow rate caused the head-capacity curve to peak at a lower discharge pressure. Finally, increasing the air content caused a shift in the efficiency curves such that peaked at a lower efficiency value as well as a lower flow capacity.
njit-etd1968-005 (89 pages ~ 6,704 KB pdf)
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Created August 9, 2006