Study On Deformable Solid Two-phase Flow And Forward-extended Double-blade Sewage Pump

The deformable solid two-phase flow, the performance changes of sewage pump delivering solid two-phase fluid, the design and performance characteristic of forward-extended double blade sewage pump were studied in this paper. By using of Lagrange method, it analyzed deformability of deformable solid and gave out the general constitutive equation of deformable solid. The turbulent equations for sparse deformable solid two-phase flow were developed. Analyzing experiment data from almost all related public literatures, it gave out the formulation to prediction the performance change of sewage pump delivering solid two-phase fluid. It also studied the performance characteristic of forward extended double blade sewage pump and its hydraulic design in the view of theory and experiment. Finally the two-phase flow within the impeller of forward-extended double blade sewage pump was stimulated. The main works are as following:(1) The main difference between deformable solid and other solid is that it not only moves, but also deforms while flowing. So it is difficult to describe its movement. After simply introducing the equations of particle solid two-phase flow, the paper focused on the deformable solid two-phase flow. By using of Lagrange method, the paper analyzeddeformability of deformable solid and gave out the differentiating number G_t.The general constitutive equation of deformable solid considering time effect and spatial effect was developed, then its approximate constitutive equation was discussed. Transient local equations for deformable solid two-phase flow based on two-fluid model were developed. Neglecting collision item, analyzing the stress and the momentum transfer of the interface, the volume averaging turbulent equations for sparse deformable solid two-phase flow was given out which can be applied to numerical stimulation of this type of two-phase flow.(2) For the purpose of studying the performance change of pump delivering solid two-phase flow, the velocity and stress of two-phase flow within impeller were analyzed. It concluded that whether the density of solid is larger than liquid or not, V_u of solidphase is smaller than that of liquid phase, and the total head of pump when delivering two-phase flow is smaller that when delivering single liquid phase at the same flow rate.(3) The data concerned with performance changes of pump delivering solid two-phase fluid from almost all the public literatures was concentrated. According to the data, the formulation on the head reduce of pump delivering solid two-phase was developed by using multiple variable linear regressive method. The difference between the formulation and others is that it considers the effect of pump typical configuration. The calculation results of the formulation and other formulations, the test results were compared. It illustrates that the formulation of this paper is more accurate than others.(4) The power and efficiency change of pump delivering solid two-phase fluid were discussed. Formulations for predicting the power and efficiency change were recommended.(5) Based on the one dimension theory, it studied the hydraulic design of forward-extended double blade sewage pump. In the case of double blades, the slipping coefficient of impeller is much larger than general centrifugal impeller. So the diameter and breadth of impeller should be augmented. Attention should be paid to the deference of wreathing angle and stagger angle between the two streamlines of back shroud and forward shroud. As for the hydraulic design of volute, its basic circle and tip area may be larger than others. As an example, two different hydraulic designs of this kind of impeller with the same axial section and different streamlines of blade for the same performance parameters were given out to show the specialty of its design.(6) The flow within the two designed impeller was stimulated with standard k-εmodel, SIMPLE arithmetic and standard well function. Analyzing the simulation result, the head and efficiency of impeller were predicted(7) By the test of hydraulic performance and the passage capacity, the performance curves (head, efficiency and power curve), the capacity of particle solid and fiber of the two different impeller and impeller of which the blade inlet even three times incised were gained. The hydraulic test shows that the performance of two different impellers meet the requirements of standard JB/T8857-1999《centrifugal sewage submersible pump model and performance parameters》, the efficiency of one of them is very close to general water pump. But the efficiency of two impelles is obviously different, forward extending inlet of blade has little influence on the hydraulic performance. The passage capacity test shows that impeller with double forward-extended blades features better capability for particle solid to pass and better anti-winding ability.(8) Compared the result of numerical simulation of the flow within impeller with the test result, it concluded that the result of numerical simulation is some higher, but the both are consistent in the view of changing trend of performance curve for the same impeller and the compare of the performance of different impeller. So numerical simulation is reliable to some extent, and is helpful for optimizing hydraulic design of pump.(9) The reasons for better passage capability of forward-extended double blade sewage pump are that: (a) with double blades, the larger tunnel of impeller avail for particle solid to pass through. (b) Forward extending blade can slightly enhance the center pressure and turbulence of impeller inlet. Then the anti-winding ability is improved. (c) The angle between the inlet of blade and shroud is obviously different from other centrifugal impeller, which enhance its anti-winding ability.(10) Simulating the solid-liquid two-phase flow within the double forward-extended double blade impellerwith mixture model. For bettering calculation, self-adapting technology was used. The boundary condtion defined as following: Velocity inlet and outflow, non-slip well boundary for liquid phase but velocity formulation coming from literatures concerned well boundary for solid phase. The pressure distribution of the mixture, the velocity distribution and the turbulent kinetic energy distribution of liquid phase and solid phase, the track of solid phase flow were given out. The calculating result shows that the total head of forward-extended double blade sewage pump delivering the mixture of solid-liquid two phase is lower than delivering liquid single phase, the turbulent kinetic energy in the vicinity of inlet hub of impeller is large which is helpful for fiber to pass the impeller.