Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Casing having tangential inlet or outlet
Patent
1996-09-09
1998-08-25
Kwon, John T.
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Casing having tangential inlet or outlet
415203, 416223B, F04D 2944
Patent
active
057977240
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an impeller and volute for a centrifugal slurry pump, and to a centrifugal slurry pump incorporating said impeller and volute.
BACKGROUND OF THE INVENTION
Throughout this specification the term "centrifugal slurry pump" is intended to denote any centrifugal pump that can be used to pump slurries or other liquids containing abrasive solids in suspension.
Centrifugal pumps generally comprise an impeller mounted on a rotatable shaft and enclosed by a volute. The impeller includes an intake opening formed coaxially with the rotatable shaft and an outlet opening extending about the periphery of the impeller. A plurality of blades extend generally radially between the intake opening and the outlet opening with the region between adjacent blades defining respective blade passages through which the liquid to be pumped can flow. A liquid discharge opening is formed in the casing which usually extends along an axis generally perpendicular to the rotatable shaft. As the impeller rotates, it imparts kinetic energy to the liquid within the impeller and causes it to move in the direction of rotation and radially outward. The liquid is then carried to the discharge outlet. The area of the volute increases toward the discharge outlet, causing the kinetic energy of the liquid to be converted to pressure energy. At a given rotational speed, a centrifugal pump will operate at peak efficiency only at certain conditions of flow rate, pressure and shaft speed as determined by its design, and in particular, the combined geometry of the impeller and casing.
When designing centrifugal slurry pumps the geometry of the volute and impeller are critical in determining the efficiency and wear characteristics of the pump. The choice of design geometry is often influenced by a desire to lower flow velocity through the blade passages of the impeller and the volute. However, as the volute is widened to decrease flow velocity the pump efficiency decreases due to hydraulic losses arising from boundary layer separation, turbulence and recirculation flows. Therefore, there is a need to carefully balance the requirements of operating efficiency and wear rate in the design of slurry pumps. Hitherto, in order to obtain a satisfactory balance between the competing requirements of efficiency and wear, slurry pumps have generally been constructed to have a hydraulic efficiency of between 5% to 15% below the theoretically achievable efficiency as determined by specific speed/efficiency charts. For slurry pumps of specific speed 22 to 30 and flow rates greater than 100 liters/sec, the theoretically achievable efficiency is typically in the order of 80% to 85%.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a combination of impeller and volute for a centrifugal slurry pump of a configuration which, when in use, assists in increasing the efficiency and/or wear resistance of the centrifugal slurry pump.
According to the present invention there is provided an impeller adapted for rotatable mounting within a volute of a centrifugal slurry pump, the impeller comprising:
an intake opening formed coaxially with an axis of rotation of the impeller;
an outlet opening extending about the periphery of the impeller; and, opening and the outlet opening, the region between adjacent blades defining respective blade passages through which a slurry is caused to flow upon rotation of said impeller, the width of each blade passage measured along a line perpendicular to a meridional flow streamline of the slurry progressively narrowing in a direction toward the periphery of the impeller, said impeller being dimensioned relative to said volute so that, the ratio of the blade passage width (b1) measured at the entry of the blade passage to the blade passage width (b2) at the periphery of the impeller is in the range of 1.5 to 1.7;
the ratio of the diameter (D2) of the impeller and the blade passage width (b2) at the periphery of the impeller is in the range of 9.3 to 10.2; and,
the
REFERENCES:
patent: 4872809 (1989-10-01), Addie et al.
Bremer Jeff
Liu Wen Jie
Kwon John T.
Vortex Australia Proprietary, Ltd.
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