Analysis On Internal Flow Characteristics In Stator And Rotor Cascades Of The Screw Mixed Flow Pump And Retrofit Design For The Stator

A built-in propulsion pump was designed for certain pump-jet propulsion based on the momentum theorem and the design principle of vane pump in this paper. In order to make the pump present a good performance, the screw mixed-flow impeller with the effect of screw propulsion and the space guide vane with the effect of expansion pressure and axial drainage are used as the main flow components in the pump. Considering that the pump have some hydraulic performance and structural characteristics of both screw pump and mixed-flow pump, thus its proposed name is called screw mixed-flow pump.The screw mixed-flow pump is mainly composed of a screw mixed-flow impeller and a new type of space guide vane, so the matching efficiency between the impeller and the space guide vane is crucial to the performance of the pump. Therefore, the CFD technology was applied in this paper for the numerical simulation of the internal flow field of the screw mixed-flow pump. The external performance and internal flow characteristics of the pump was obtained and then remodeling the stator cascade based on its internal flow characteristics in the stator and rotor cascades and the initial structure. To some extent, the performance of the pump has been improved by the retrofit design for the stator. The concrete work and conclusions are as follows:First of all, the current research status of design theory and internal flow characteristics of several type of pump associated with the screw mixed-flow pump at home and abroad was systematically summarized. Meanwhile, the background and significance to carry out the research of the internal flow and stator cascade modification in the screw mixed-flow pump were explained. Then according to the water-jet propulsion performance parameters given by user and working conditions, the screw mixed-flow pump for the propeller was designed. And then according to the pump structure parameters, the three-dimensional calculation model of the pump was created by using Pro/E and the model mesh generation was completed by using ICEM. Finally, the steady flow field of the model pump was numerically calculated with Fluent 15.0 and the external performances and the internal flow field structure of the pump were analyzed.Research indicates that the structure and hydraulic performance of the pump are practicable, but the internal flow disorder in the stator cascade resulted from the poor design of space guide vane, and directly resulting in the model pump efficiency decrease. The pump simulation efficiency is about 75% and a little lower than the design efficiency that is 80% at design condition, so it is needed to redesign the space guide vane.Consequently, the retrofit design for the space guide vane has been carried out based on the above model pump external performances and the stator cascade flow characteristics. The relationship between internal flow characteristics and flow losses was comparatively analyzed in the stator cascade of the model pump under the conditions of three group guide vane profiles and 3/5/7/9 guide vanes. Finally, the optimized static cascade matched well with rotor cascade under the design flow rate was searched out with the best guide vane profile and reasonable guide vanes. The matching between stator and rotor cascades and the internal flow field structure and the external performance of the screw mixed-flow pump have been improved after the space guide vane retrofitting.The research will provide some reference for the design and optimization of screw mixed-flow pump and space guide vane.