Study On The Unsteady Characteristics Of Solid-Liquid Two-Phase Flow In Rotor-Stator Cascades

The mutual interference between the stator and rotor in the hydraulic machinery is the main reason for the induced vibration, noise and low efficiency of the hydraulic machinery. Particles makes flow field structure of hydraulic machinery more complex, increasing the rotor-stator cascades wear, reducing the energy of the fluid when the moving medium is sand water. Therefore, the research on the flow characteristics of the solid-liquid two-phase fluid in rotor and stator cascades can provide reference and basis for the optim ization design of the solid-liquid two-phase flow hydraulic machine.Stokes number is a com prehensive dimensionless parameter including particle density, particle size, fluid characteristic velocity, characteristic length and fluid viscosity. Use it to def ine the inte raction mechanism of particle and coherent structure.Based on large eddy simulation and Mixture model, take a centrifugal pump with vane as the research object.The design para meters of head is 29.3m, flow rate is 45.7m3/h. Simulated the solid-liquid two-phase flow under different particle density ρd=950kg/m3, ρd=1650kg/m3, ρd=2650kg/m3 and dif ferent particle size d=0.016 mm, d=0.026 mm, d=0.036 mm.Came to the following conclusions:1. With the inc rease of particle density, the head and ef ficiency of the model pump appeared in a small range. Under different particle density, pressure value in the impeller gradually increased from the inlet to the outlet and showed a ladder distribution with the a cting law of the cen trifugal pumps. The suction side of the impeller inlet appears area of negative pressure, and the pressure value decreases with the increase of the particle density. Under the design condi tion, the flow in m ost of the flow channel is sm ooth. With the increa se of particle density, the num ber of vortices in the flow channel increases, and the flow instability is enhanced. When the particle density is larger, the solid volume in the inlet of pressure side of the blade is gradually decreased, while the so lid volume of the suction surface remains constant and remains the original solid concentration.2. When the St number is much less than 1, the particle dispersion mechanism is the same in the flow field. Lar ge eddy plays a lead ing role in the dispersion of particles.3. The monitoring point on the outlet of the impeller and the middle of the guide vane appears of high-frequency pressure pulsation, monitoring points on the outlet of the guide vane and on the volute and the volute tongue appears of low-frequency pulsation. With the increase of particle density, the pressure fluctuation characteristics of the rotor-stator cascade a re enhanced. The m ain factors for the generation and evolution of the eddy in the stator and rotor cascades are strong shear action of the rotor and lar ge inverse pressu re gradient. With the inc rease of particle density, the number of high ener gy vortex in the flow channel increases, which increas es the complexity of the flow in the flow passage. The increase of particle density delays the process of vortex merging and splitting.4. The head and ef ficiency decrease with the increase of the particle size. The pressure values gradually increased along the inlet to the outlet of the impeller under different particle sizes, pressure value in the sam e position of the g uide vane decreases with the increase of particle size. When the particle size increases, the sand volume fraction of the inlet become larger, most of the solid particles are gathered at the inlet of the i mpeller and the pressure surf ace of the m oving blade. With the increase of particle size, the volume fraction of the particle in the same position of the blade wall increases.5. When the St number is less than 1, th e change of St number does not change the dispersion mechanism of large eddy in the dispersion of particles in the flow field. Consistent with the study of density variation.6. The generation and distri bution of vortex are consistent with the dif ferent particle densities. The change of particle size has no effect on the distribution, energy size and structure of the vortex.