river dredge pump job description

Lab Report 1 Centrifugal Pump

Introduction

The centrifugal pump is one of the most prevalent radial-flow turbo machines. An impeller attached to a rotating shaft and a stationary casing surrounding the impeller make up the two major parts of this kind of pump. The fluid gains energy from the moving blades. As the fluid moves from the eye to the periphery of the blades, pressure and absolute velocity both rise. The fluid flowing from the impeller into the casing around the impeller converts the kinetic energy into additional pressure rise.

The real performance of a centrifugal pump cannot be predicted entirely theoretically due to the overall complexity of flow through a centrifugal pump. Pump tests are used to experimentally determine the actual pump performance, and the results are displayed as pump performance curves. Typically, performance metrics are presented as plots of head rise, efficiency, and power vs flow rate for a given pump shape and operating speed. The engineer in charge of integrating pumps into a certain pipe flow system will find this information to be of the utmost value.

Theory

The pump head rise can be expressed using the energy equation as h2=(p2−p1)/ρg+(z2−z1)+(V22−V12)/2g. Typically the differences in elevations and velocities (between inlet and outlet) are so small so that hp=(p2−p1)/ρg. The power Pf, gained by the fluid is given by the equation Pf=ρgQ hp. The pump overall efficiency η is the ratio of power actually gained by the fluid to the shaft power supplied Ẇshaft as given by the equation η = Pf/ Ẇshaft. Where Ẇshaft the shaft power, is the product of the Torque applied to the shaft and the angular velocity, ω Ẇshaft = Tshaft(t). Where ω = 2πN/60