Research on blade tip clearance cavitation and turbulent kinetic energy characteristics of axial flow pump based on the partially-averaged Navier-Stokes model

To reveal the cavitation forms of tip leakage vortex(TLV)of the axial flow pump and the flow mechanism of the flow field,this research adopts the partially-averaged Navier-Stokes(PANS)model to simulate the cavitation values of an axial flow pump,followed by experimental validation.The experimental result shows that compared with the shear stress transport(SST)k-ωmodel,the PANS model significantly reduces the eddy viscosity of the flow field to make the vortex structure clearer and allow the turbulence scale to be more robustly analyzed.The cavitation area within the axial flow pump mainly comprises of TLV cavitation,clearance cavitation and tip leakage flows combined effect of triangular cloud cavitation formed.The formation and development of cavitation are accompanied by the formation and evolution of vortex,and variations in vortex structure also generate and promote the development of cavitation.In addition,an in-depth analysis of the relationship between the turbulent kinetic energy(TKE)transport equation and cavitation patterns was also conducted,finding that the regions with relatively high TKE are mainly distributed around gas/liquid boundaries with serious cavitation and evident gas-liquid change.This phenomenon is mainly attributed to the combined effect of the pressure action term,stress diffusion term and TKE production term.

Experimental and numerical investigations of cavitation evolution in a high-speed centrifugal pump with inducer

Along with the anti-cavitation performance,the high speed and the high power density,are the main trends in the development of centrifugal pumps.At present,the most effective method is to install an inducer in front of the impeller.However,the tip leakage of the inducer results in the vortex cavitation at the blade leading edge of the inducer,and the cavitating flow inside the inducer seriously interferes with the hydraulic behavior of the inducer as well as the impeller with the development of the cavitation,thus to badly affect the operational reliability of the high-speed centrifugal pump.In the present paper,the cavitating flow in a high-speed centrifugal pump with an inducer is investigated by numerical simulations and visual experiments for different cavitation numbers.A typical evolution process of the cavitation is shown,including the inception,the development and the deterioration.A general description of the pump head-drop phenomenon is made through the study of the local and global flow fields,and the relationship between the vapor distribution and the static pressure distribution along the inducer is determined to describe the evolution of the cavitation.This paper intends to provide the foundation for studying the overall cavitation state of a high-speed centrifugal pump,and designing the inducer with a better cavitation resistance.

Filament geometrical model and nozzle trajectory analysis in the fused deposition modeling process

The geometrical model of the filament during the fused deposition modeling (FDM) process was firstly proposed based on three different models, tractrix, parabola, and catenary. Comparing with the actual measured filament curves on the Stratasys 1600 FDM machine, it is indicated that the tractrix model had the best agreement with the actual measured curves. With the analytical simulation, the nozzle trajectories in the straight-line deposition road, circle road, and arbitrary continuous curve road were deduced, according to the traxtric based geometrical model of the filament.