Experimental and numerical study of transient flow in a centrifugal pump during startup

Abstract

Transient characteristics and flows in a centrifugal pump during its starting period were experimentally and numerically investigated. The two-dimensional particle image velocimetry technique was used to capture transient flow evolutions in the pump's diffuser. A new dynamic slip region method that combines the dynamic mesh method with the non-conformal grid boundaries is proposed to resolve the transient flows caused by the started impeller. Numerical self-coupling was realized by establishing a circulation pipe system along with the pump model equivalent to the experimental pump system. Numerical and experimental results agree well in both explicit characteristics and internal transient flow structures, confirming the validity of the proposed method. Analysis of the instantaneous flow in the impellers indicates that for the early stage of the startup, the transient vortex evolution between blades is the main reason for the transient head coefficient being lower than the steady state value. The reversed flow at the blade inlet is a less important reason for this effect. In later stages, the weakening of the intensity of the spatial vortex visible on S 2m and the main flow stream are the main reasons for the explicit performance slowly rebounding to the steady value.

Numerical Simulation of the Transient Process of Power Failure in a Mixed Pump

“…The grid independence and temporal test have been done in former studies [8] and here is a brief introduction. The mesh information is listed in Table 2.…”

“…There are two mathematical models, (8) and (9), to simplify the transient process. In this case, the initial rotational speed is 1500 r/min.…”

“…According to the simulation result, halfspeed time is 0.32038 s. This theoretical result is taken as theory model 1. And in physical model calculated by (8), is 0.28224 s. It is taken as theory model 2. These three results are all shown in Figure 6.…”

“…CFD technology had been successfully used in the transient calculation of pumps during starting and stopping periods [6][7][8][9]. With this method, not only the external characteristic but also the internal flow field could be obtained clearly.…”

Investigation of Transient Flow in a Centrifugal Charging Pump during Charging Operating Process

“…The model can be applied for analyses of purely unsteady cases where the pump dynamic characteristics show considerable departure from their steady-state characteristics. Li et al [7,8] used computational fluid dynamics to study the three-dimensional unsteady incompressible viscous flows in a centrifugal pump during rapid starting period (0.12 s). The rotational speed variation of the field around the impeller was realized by a dynamic slip region method, which combined the dynamic mesh method with nonconformal grid boundaries.…”