Abstract
To study the reasons for the low efficiency of jet centrifugal pumps (JCPs) and the mechanism of unsteady flow characteristics under multiple conditions, taking a JET750G1 JCP as the object, three-dimensional steady and unsteady numerical calculations of the model pump were carried out using the k–ω turbulence model. The transient fluctuation characteristics of the flow field in the major flow passage components and the spatial and temporal evolution laws of vortices in the rotor–stator cascades were analyzed. The accuracy of the numerical method was verified by experiments. The results show that there are various scales of flow distortion phenomena in the chamber of the JCP, such as eddies, blockage of the flow passage, recirculation, secondary flow, and circulation, which not only cause great hydraulic loss, but also destroy the flow stability, symmetry, and balance in the other flow passage components. This is an important reason for the obviously lower efficiency of a JCP compared to a general centrifugal pump. The spatial and temporal evolution laws of vortices in the rotor–stator cascades are mainly related to the relative positions of the impeller blades and guide vane blades. The formation mechanism of the unsteady flow field fluctuation characteristics of JCPs is mainly related to the number of blades in the rotor–stator cascades and the operation parameters of the pump. The fluctuation intensity of the flow field inside the impeller and guide vane is obviously greater than that in the other flow areas, reflecting that the rotor–stator interaction is the decisive factor affecting the unsteady flow characteristics of a JCP under multiple conditions.
Highlights
The flow passage components of a jet centrifugal pump (JCP) have relatively more complex internal flow, which leads them to have shortcomings such as low efficiency, easy cavitation, and high noise
The main results are as follows: (1) Under multiple operating conditions, various scales of flow distortion phenomena occur in the JCP chamber, such as eddies, blockage of the flow passage, recirculation, secondary flow, and circulation, which cause great hydraulic loss, and destroy the flow stability, symmetry, and balance of the other flow passage components’ flow fields
(2) The spatial and temporal evolution laws of vortices in rotor–stator cascades are mainly related to the relative positions of impeller blades and guide vane blades; the scale of vortices is related to the structures of the impeller blade and guide vane blade, and to their matching relationship
Summary
The flow passage components of a jet centrifugal pump (JCP) have relatively more complex internal flow, which leads them to have shortcomings such as low efficiency, easy cavitation, and high noise. The reasons for the low efficiency and the formation mechanism of the unsteady flow characteristics of the pump are analyzed with respect to the flow pattern, distribution characteristics of the time-averaged flow field and fluctuation intensity, spatial and temporal evolution process of vortices in the rotor–stator cascades, and pressure fluctuation characteristics in the major flow passage components. This provides a theoretical basis for the design and optimization of JCPs with high efficiency and low energy consumption
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