Applied Mechanics and Materials Vols. 405-408

Abstract: In this paper, the structural safety of the Niuwan Bridge subjected to vessel collision is investigated by the large-scale commercial finite element software ANSYS. A whole FEM model is built and a reasonable analysis and illustration for taking the value of vessel-collision forces is presented. Additionally, under the premise of reasonable simulation of the boundary conditions, the effects of the support abutments, the prestress and the carloads are considered. The analysis results have certain reference values for the anti-collision and reinforcement of bridges.

Abstract: Mixed-flow pump is one of the most widely used general machinery, it is necessary to study the efficiency of the mixed-flow pump. In this paper, we have made a test on a mixed-flow pump model. After testing we got the conclusion that the mixed flow pump efficiency analysis of experiments in 6 different blade angle of operation, through the analysis of the status, to this model the suitable angle is-4 °.

Abstract: Aiming at some boiler tubescrack in a power plant, the element composition and the valence of elements in corrosion products on the outer surfaces of the boiler tubes were analysed by Scanning Electron Microanalyzer (SEM) and X-ray Photoelectron Spectroscopy (XPS), and the corrosion reason and mechanism of the outer surfaces of the boiler tubes were studied.The results showed as follows. (1)The content of element S in the corrosion products on the outer surfaces of the fire side boiler tubes was bigger than that in the corrosion products on the outer surfaces of the back side boiler tubes and the corrosion of the outer surfaces of the fire side boiler tubes was more serious than that of the outer surfaces of the back side boiler tubes. (2) the element S in the corrosion products existed in the form of sulfate (SO₄^2-), because the valence of S in the corrosion products on the outer surfaces of the fire side boiler tubes and the back side boiler tubes was +6, not-2. (3) the element Fe in the corrosion products on the outer surfaces of the fire side boiler tubes and the back side boiler tubes existed in the form of Fe₃O₄, Fe₂O₃ or Fe₂(SO₄)₃. (4) The corrosion of the boiler tubes was induced by sulphate under high temperature, and aggravated with the temperature of the outer surfaces of the boiler tubes elevated.

Abstract: The flow around four cylinders in a square configuration with a spacing ratio 4 and Reynolds number of 200 are investigated using lattice Boltzmann method for angles of incidence α=0 and 45º, respectively. The results show that no biased flow occurs and the flow pattern is symmetrical at α=0, and the vortex shedding exists after the upstream cylinders which is completely different from the experimental results. It is hard to explain the discrepancy at present. The phenomenon of vortex shedding in-phase observed in the experiment reappears in the numerical simulation at α=45º.

Abstract: The curve of flow-head is one of the most important indicators to assess water pump performance. While it is difficult to get measured data in real condition and the data is very limited. The method of pump data mining based on support vector machine (SVM) is built due to its superiority in dealing with small sample event. The method is aimed at finding out the unknown data between measured data and drawing more accurate flow-head curve. It was found that the model of pump data mining based on SVM is much better than neural network when their curves are compared.

Abstract: According to the shape of 3-arcs blade the distribution function equations on 3-arcs blade surface were deduced and the hydraulic characteristics on blade surface were analyzed. Based on the establishment of relative velocity and pressure equations, the step change equations of relative velocity and pressure on blade surface were also deduced on connected line which was formed by the intersection of two cambered surfaces, and the reason and the relationships between control parameters were revealed. The step change value of relative velocity is equal to diameter difference of two intersect arc cylinders. The step change value of pressure is concerned with the position coordinates of initial origin of two intersect arc cylinders. Calculation example confirmed that the step changes of relative velocity and pressure will appear on intersection of two cambered surface.

Abstract: The overhang steel liner is designed for the asymmetry circumfluence hole in the differential surge chamber of Jinping II hydropower station, which is subjected to high hydrodynamic loads resulting from hydraulic transient processes. The maximum external water pressure on the overhang steel liner is about 40-50m head larger than the internal water pressure. Thus its thickness depends on the compressive resistance stability, which is studied in this paper by both the finite element method (ANSYS buckling analysis) and the critical external pressure formula of steel penstocks adopted in the design specification (Mises formula). The stability analysis of the overhang steel liner shows that the circular tube scheme is superior to the semicircle tube scheme and its wall thickness should be 24mm for safety reason. Comparative analysis between ANSYS and Mises formula shows that it is feasible to analyze the compressive resistance stability of overhang steel liner by using Mises formula if the length is considered in an appropriate manner.

Abstract: The cartridge style pilot relief valve is widely used in construction machinery field owning to its compact structure. The damping orifice is variable, which improves the stability and impact resistance. What more, the valve can realize filling oil. This article tells the principle of the valve, and analyses its dynamic performance by power bond graph method and AMESim software, which concludes how the parameters impact on its dynamic performance, such as the main valve spool damping coefficient, damping orifice diameter, the pilot spring stiffness and so on.

Abstract: Air-water flows are of importance for all the areas related to fluid mechanics. Especially, although kinematic investigations of the multi-phase flows have been conducted for a long time, velocity measurements are still considered as a very challenging part. This study introduces an imaging technique applying shadowgraphy and coupled fiber optic probes for velocity measurements of air bubbles. The fiber optic probes apply optical fibers to the well-known intrusive phase detection probe with a shape to reduce flow disturbance. The present method is used for bubble plume measurements and obtained velocity result is discussed. Finally, the velocities are compared to examine the reliability of the methods.

Abstract: The core of energy efficiency assessment (EEA) among energy consumers is to establish an integrated assessment model. In the paper, first, EEA process was described, and an assessment methodology based on gray relational analysis was introduced. Afterwards, a motor driving pump system was further studied as a typical example. By sorting pump-related standards and literatures, three indexes were chosen to form an assessment model for pump station, which were motor efficiency, unit energy consumption and pump efficiency, respectively. According to grey relational analysis, the operating data of one pump station in 24 hours a day was calculated and evaluated, and the result shows the feasibility of this EEA methodology for various energy systems, which provides a fresh idea for comprehensive evaluation of energy efficiency.