流体力学与传热（伍钦）08-9chapter2-2.pptVIP

End suction/ Top discharge The suction nozzle is located at the end of and concentric to, the shaft while the discharge nozzle is located at the top of the case perpendicular to the shaft. This pump typically has lower NPSHr because the liquid feeds directly into the impeller eye. Top suction/ Top discharge nozzle The suction and discharge nozzles are located at the top of the case perpendicular to the shaft. Rotating Components 1. Impeller The impeller is the main rotating part that provides the centrifugal acceleration to the fluid. Impellers of pumps are based on the number of points that the liquid enter the impeller and also on the amount of webbing between the impeller blades. Single-suction: a) Single-suction b) Double- suction ? Based on suction type A single-suction allows the liquid to enter the center of the blades from only one direction. Double-suction: Liquid inlet to the impeller symmetrically from both sides. A common type uses a double-suction impeller , which accepts liquid from both sides ? Based on mechanical construction Impeller can be open, semi-open, or closed. The open impeller consists of only blades attached to a hub. No shrouds or wall to enclose the vanes. The semi-impeller is constructed with a circular plate (the web) attached to one side of the blades. Open and semi-open impellers are less likely to clog, but need manual adjustment to the volute or back-plate to get the proper impeller setting and prevent internal re-circulation. Vortex pump impellers are great for solids and stringy materials but they are up to 50% less efficient than conventional designs. The closed-impeller has a circular plate attached to both sides of the blades. Enclosed impellers are also referred to as shroud impeller. shrouded 2.???Shaft The basic purpose of a centrifugal pump shaft is to transmit the torques encountered when starting and during operation. Definition of Important Terms The key performance paramet