"EXPERIMENTAL AND THEORETICAL INVESTIGATION ON THE PERFORMANCE OF CENTRIFUGAL PUMP IN CONJUNTION WITH INDUCER"

Abstract

The introduction chapter (1), shows the general outlines for the description of the centrifugal pump as a rotodynamic pump that uses a rotating impeller to increase the velocity of the fluid, and are used for large discharge through smaller heads, the vast majority of pumping applications involved positive displacement pumps . The working principle of centrifugal pump, a centrifugal pump works by the conversion of the rotational kinetic energy, typically from an electric motor or turbine, to an increased static fluid pressure. This action is described by Bernoulli's principle . The rotation of the pump impeller imparts kinetic energy to the fluid as it is drawn in from the impeller eye (centre) and is forced outward through the impeller vanes to the periphery. As the fluid exists the impeller, the fluid kinetic energy (velocity) is then converted to (static) pressure due to the change in area the fluid experiences in the volute section. Typically the Volute shape of the pump casing (increasing the volume), or the diffuser vanes, which serve to slow the fluid, converting to kinetic energy into flow work, are responsible for the energy conversion. The energy conversion results in an increased pressure on the downstream side of the pump, Causing flow.

centrifugal water Pumps are classified as following ways: A) On the basis of the head. B) On the basis of the type of casing. C) On the basis of number of stages. D) On the basis of the direction of flow through impeller. E) On the basis of the number of entrance to the impeller. F) On the basis of the liquid handled. G) On the basis of the specific speed. H) On the basis of the position of impeller. Centrifugal slurry Pumps have much in common ; they are varied to meet special requirements & particular needs of each Service: 1) Petroleum industry. 2) Chemical industry. 3) Paper industry. 4) Water supply. 5) Sewage & pump services. 6) Irrigation, Drainage & flood control. 7) Mining & Construction.

Multiphase fluid systems used in centrifugal slurry pumps contain more than one phase, and at least one of them being a fluid. The disperse phase may consist of solid particles, gas bubbles, or liquid droplets when the continuous phase is a liquid. The dynamics of multiphase systems comprises of mass, energy, charge and momentum transports in these systems. Multiphase systems might have gas-solid particles, gas-liquid droplets, liquid-gas bubbles, liquid-liquid droplets, and liquid-solid particles. There are two methods of approach to the dynamics of multiphase systems: Firstly, Considering the dynamics of single particles and then extending it to a multiphase system in an analogous fashion. Secondly, Investigating the continuum mechanics of single-phase fluids, then using a similar way to explain what happens in the presence of particles. In the hydraulic transportation of settling solids in horizontal pumps, the transport velocities smaller than the suspending velocity are used at most of the time to be more economical. Slurry flow in pumps is different from the homogeneous liquid flow in several aspects: - For the latter case, the nature of the flow depends on the physical properties of the fluid, - For the former case two different types of flow affect the system: (I) Homogeneous slurries: these slurries have uniform solid particle distribution in liquid medium size of the particles is very small (fine) and solid concentration is high . (II) Heterogeneous slurries: distribution of the solid particles is not uniform. A pump equipped with an inducer may operate at 1/2 to 1/3 the NPSHR levels of a non-inducer version of the same pump; using inducers (helical – axial) may improve the centrifugal pump performance by Increasing efficiency head and decreasing brake power. Inducers have been developed to improve the required net positive suction head requirements (NPSHR). The inducer mounts on the threaded area of the rotor assembly (taking the place of the impeller nut) and operates as a low (NPSHR) axial flow impeller in series with the main pump impeller. The inducer can be added to any of the standard models by removing the impeller nut and replacing it with the inducer. This feature will achieve field reduction of the (NPSHR). There are two types of inducers: 1) Axial Inducer: this type of inducer reduces the (NPSHR) of the pump throughout the entire operating range. 2) Helical Inducer: A helical inducer will lower the (NPSHR) more than an axial inducer for a specific flow-rate, but care must be taken that the flow remains within the operating rang of the inducer. Centrifugal pump impellers often have a suction specific speeds of about 8000 to 12000, use of inducers can increase (S) to a range of 15000 to 35000. this typically allows lower flow pumps to operate at 11000 rpm with the same NPSH, which would be required at 3600 rpm without inducer, or reduce (NPSHR) of all pumps to less than half at the same speed. The historical review chapter (2), in this chapter the author has collected available research works and experimental works closed to the idea of his thesis work. He ordered and arranged these works with respect to its time date (From ancient to recent). All collected works were published and licened from either universities or institutes (as master thesis or Ph.D. thesis).