1. Introduction

The most common fault in a submerged pump is due to waste clogging. This phenomenon causes not only motor overload but also serious damage to a pump system. Hence, this type of pump requires unique design features for preventing losses in performance due to factors such as waste clogging, damage, and failure, unlike general submerged pumps.

Representative types of submerged pumps for wastewater treatment consist of the crushing type and flow-path-securing type. A crushing-type pump mostly crushes and transfers foreign substances with a disintegrator installed in front of the impeller. However, as such types of pumps require the installation of an additional crusher, large-sized solid particles cannot be

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

driven perfectly along the flow path. Moreover, it has a complex structure, high cost, low capacity, and frequent replacement cycle. On the other hand, as a single-channel pump is a representative case of a flow-path-securing type, it has different mechanism features compared with general pumps pressurized by multiblades. A single-channel impeller has one free annulus passage and does not have multiple blades. Further, it is driven by the centrifugal force generated from the rotating annulus passage [1]. Therefore, a single-channel pump is very robust, especially against failure and damage due to waste clogging.

Because of these advantages, the demand for single-channel pumps has increased rapidly in recent times in the field of wastewater treatment. Nevertheless, only a few studies have been published on the design of a single-channel pump [1–4]. To the best of the author's knowledge, the lack of studies can be attributed to the difficulties in establishing a theoretical design methodology, manufacturing, and especially, solving the balancing problem related to the fluid-induced vibration between the impeller and volute of a single-channel pump. In fact, because the mass distribution of a single-channel impeller is not rotationally symmetric, it is difficult to stabilize the fluid-induced vibration between the impeller and volute. Furthermore, unsteady radial forces, which rotate at a frequency generally determined by the rotating speed, are generated in the single-channel impeller [5]. These unsteady sources are generated by the interaction between the rotating impeller and volute, and these adversely affect the overall performance of a single-channel pump, especially its life expectancy and durability.

Over the past several years, there has been growing interest on the effects of unsteady dynamic radial forces due to impeller-volute interaction in centrifugal pumps [6–8]. However, no systematic studies on single-channel pumps have yet been attempted, except for several concepts and patents. To this end, this work presents a state-of-the-art design technique for a singlechannel pump for wastewater treatment based on a theoretical approach and threedimensional steady and unsteady numerical analyses. Moreover, advanced multidisciplinary numerical design optimization techniques are introduced and discussed in detail to simultaneously improve hydraulic efficiency and reduce the flow-induced vibration due to the impeller-volute interaction in a single-channel pump. The objective of this chapter is to provide practical guidelines for optimizing the design of a single-channel pump with the proposed design approach.

> and does not contain multiple blades. Further, the impeller is driven by the centrifugal force generated from the rotating annulus passage. Thus, the internal flow distribution in the crosssectional area of the impeller and volute is changed proportionally with the theta angle position in order to maintain a constant flow velocity. Figures 2 and 3 show the distribution of internal flows in the cross-sectional area of the impeller and volute generated from the Stepanoff theory. In the authors' previous work, for example, the reference volume flow rate

State-of-the-Art Design Technique of a Single-Channel Pump for Wastewater Treatment

http://dx.doi.org/10.5772/intechopen.75171

185

When the distribution of internal flows in the cross-sectional area is determined according to the theta angle, the shape of the area should be defined. This shape is very important for deciding the hydraulic performance and size of solid matter in a single channel. In the previous work, the authors proposed a novel design method for defining the cross section of the

/min and 10 m, respectively, with a rotational

and total head at the design point were 1.42 m3

Figure 2. Cross-sectional area distribution and definition of the impeller [10].

Figure 1. Three-dimensional shape of a single-channel pump [10].

speed of 1760 rpm [11].
