Liu Xiaobing

Numerical analysis of solid–liquidtwo-phase turbulent flow in Francis turbine runner with splitter bladesin sandy water

As the key component of a hydroelectric power generation system, hydraulic turbine plays a decisive role in the overall performance of the system. There are many sandy rivers in the world, and turbines working in these rivers are seriously damaged. Therefore, the research of flow in sandy water has great theoretical significance and practical value. Based on the specific hydrological conditions of a hydropower station, the solid–liquid two-phase flow in the whole flow passage of a Francis turbine with splitter blades in sandy water was numerically studied. A geometric model of the whole flow passage of the Francis turbine was established on the basis of given design parameters. The solid–liquid two-phase turbulent flows in Francis turbine runner under three different loads were numerically analyzed by using this model. The three different loads are as follows: Condition 1: single unit with 1/4 load, Condition 2: single unit with 1/2 load, and Condition 3: single unit with full load. The distributions of pressure and sand concentration on the leading side and the suction side of the runner blades, as well as the velocity vector distribution of water and sand on the horizontal section of the runner, were obtained under different load conditions. Therefore, the damages to various flow passage components by sand can be qualitatively predicated under various conditions. To guarantee the safety and stability of the unit, the adverse conditions shall be avoided, which can provide certain reference for plant operation.

LTCC Microwave Filters Based on BZN Ceramics

Green sheets of BZN-based ceramics were formed using tape casting technique and a gold conductive paste was used as the inner electrode. The green chips were sintered at about 950°C. The multilayer filter is composed of two coupled stepped-impedance stripline resonators, and the input/output ports of the filter are implemented with coupling capacitors to resonators. The admittance matrix for equivalent circuit of the filter was obtained from the four-port coupled-line parameter matrix. The LTCC microwave filter was designed at center frequency of 1.8 GHz. The dimensions of the experimental filter are 4 mm × 3.8 mm × 1.6 mm.

Predictive Analysis of The Damage to Axial-Flow Pump's Impeller in Sandy Water

With the use of RNG k-e turbulence model, SIMPLEC algorithm and CFD software, the turbulent flow in an axial flow impeller was numerically simulated in the clear water (single-phase) and the sandy water (solid-liquid two-phase) conditions. The distributions of solid concentration, velocity and pressure on the impeller of an axial flow pump were analyzed at the same particle diameter but different volume concentrations in sandy water. And these distributions were comparatively analyzed under the clear water and the sandy water conditions. According to the simulation results, the axial pump impeller will be damaged more easily and quickly in sandy water than in clear water. And the area more prone to damage on the axial flow impeller is predicated. The predicted vulnerable parts in an axial flow impeller are consistent with that in actual projects. This study shows that the numerical simulation results are the same as the actual situation, and it has guiding significance for the wear design of the axial flow pump. DOI: http://dx.doi.org/10.5755/j01.mech.24.3.13854

SEISMIC ANALYSIS OF NUCLEAR POWER PLANT CANNED MOTOR PUMP UNIT BASED ON INTEGRAL CALCULATION METHOD

The canned motor pump is a device in one of the most important loops in the nuclear power plant system and key technology research project, of which the seismic requirements shall be checked by Category A. It is required that the structural integrity and electric drive assembly performability of the unit can be ensured during or after operating basic earthquake (OBE) or safe shutdown earthquake (SSE). The author uses Ansys software workbench module to carry out appearance-based three-dimensional modeling, finite element meshing, intrinsic mode analysis, and carry out structural overall element analysis and calculation considering dead weight load and earthquake spectrum load. The results show that the unit major structure rotary and static parts, gear system, bearing parts, bolt and screw strengths meet the requirements and the structure maintains integrity, the relative deformation of the unit rotary and static parts shall be less than the specified value of gap among them, so as to keep the performability and not interfere with the operation. The appearance–based seismic analysis method not only can ensure the calculation accuracy, but also can greatly reduce the workload in calculation and checking, has a certain learning value.

The Structure and Dielectric Properties of Na Doped Bi2O3-ZnO-Nb2O5 Ceramics

The effects of substituting Na+ for Bi3+ on the sintering properties, the microstructure and the dielectric properties of Bi2(Zn1/3Nb2/3)2O7 -based ceramics were investigated. The results reveal that the sintering temperature of (Bi2−xNax)(Zn1/3Nb2/3)2O7 (x = 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5 and 0.6 mol) ceramics decrease from 1000°C to 880°C, the phase structure of ceramics are still single β-phase with x ≤ 0.2 mol and α-phase was observed as x > 0.2 mol. The density of (Bi2−xNax)(Zn1/3Nb2/3)2O7 ceramics decreased with an increase in x. The dielectric relaxation was observed at −30 ∼+130°C when Na ion content reached 0.375 mol. Dielectric relaxation behavior of (Bi2−xNax)(Zn1/3Nb2/3)2O7 ceramics resulted from the defect dipole because of the valence difference between Na+ and Bi3+.

Dielectric Properties of Ba(Ti0.9Zr0.1)O3 Ceramics Co-Doped with Bi and Cu

Ba0.98Bi0.02(Ti0.9Zr0.1)1−xCuxO3 (x = 0, 0.01, 0.02, 0.03 mol) ceramics were prepared by a solid state processing. X-ray diffraction analysis indicates that all of the ceramics samples have tetragonal crystal structure. The dielectric constants as a function of temperature at different frequencies show that all of the ceramics have relaxor behavior. But the dielectric dispersion is weak for x = 0.01 and strong for x = 0 and 0.03. The relaxor characteristics were discussed using random field model and Lorenz formula in BBTZC ceramics.