Advanced Materials Research Vols. 694-697

Abstract: A new type of similarity subgrid-scale (SGS) model which based on energy and dissipative scale isotropy assumption is presented. This model combines the advantages of traditional Smagorinsky SGS model with similarity SGS model. And a two-dimensional shear layer flow is simulated using refined grid result as a standard and comparing witch LES method including multiple SGS models. The results indicate that the result of SIM model much approximates to refined grid result than other SGS models.

Abstract: In order to ensure the normal operation of the hydraulic system, the faults must be found and eliminated promptly and accurately. Most of the faults of hydraulic system don’t happen suddenly. generally, there are signs such as noise, vibration, lash, pollution and leakage etc.. If these phenomena can be found, controlled and eliminated promptly and properly, the system faults can be reduced accordingly. This paper introduces several common faults of hydraulic system and the elimination methods. which the hydraulics technicians can refer to.

Abstract: With the rapid development of computer, computer simulation is a reasonable way to study the maneuverability of a ship. The accuracy of ship motion mathematical model has a great effect on research results. The resistant coefficient is a crucial parameter to ship models rapidity. Hence, it is significant and practical to research how to calculate a precise resistant coefficient. This paper introduces the theoretical calculation of ship resistance coefficient and methods to get ships hydrodynamic force based on CFD theory. With the commercial CFD software Fluent, we make numerical calculation for sailing ship based on turbulence theories, and get the ships resistant coefficients of MMG (usually called Maneuvering Model Group) model. Instead of making traditional model-scale numerical calculation, we made full-scale distributed numerical calculation with high-performance computers. After comparing the calculation results with the real ships resistant coefficients, which were obtained by actual host power and ships velocity, there is a conclusion. The calculation results are very close to the real ships resistant coefficients, since the Reynolds number and the Froude number of calculation model are almost equal to those of the real ship. Computer simulations of ships circle turning were made respectively with the resistant coefficients we got and previous estimation formula of MMG model. The simulation result of calculated resistant coefficients was closer to real ships circle turning.

Abstract: Elec-pump (electric-hydraulic-pump) is a highly integrated combination of electric motor and hydraulic pump, which has smaller size, lower noise and vibration, better heat elimination, and has broad application prospects. In this paper, an elaborately parameterized model of the axial piston Elec-pump is built for the mechanical and hydraulic joint simulation by using the simulation software AMESim and ADAMS. The joint model is composed of the electromagnetic drive model, hydraulic model, the mechanical dynamics model and the mechanical hydraulic interface. The joint simulation shows how the rotor centroid pulsation affects the output pressure of Elec-pump at different outlet pressures. The results depicts that, due to the rotor centroid pulsation, the outlet pressure pulsation rate becomes more than doubled at the revolution of 7000rev/min.

Abstract: The motion track of desulfurized fly ash in flue gas was simulated by means of Fluent software. The abrasion and deposition of desulfurized fly ash to inner surface and other internals inside of dense flow absorber were studied. The results show that, under the simulated condition, the flue gas streamline is uniform inside of dense flow absorber which is installed with the equipment of baffle plates and four-layer delta wing plates. The desulfurized fly ash could be distributed uniformly and the pressure loss is approximately 340Pa. The abrasion rate of desulfurized fly ash to No.1 baffle plate is higher and the distribution is relatively concentrated, however, the abrasion rate of desulfurized fly ash to other layers of baffle plate and delta wing plate is lower and the distribution is relatively uniform. Besides, the abrasion rate of the dense flow absorber top and the A-convex surface is higher as well. Most desulfurized fly ash deposits on the bottom of ash hopper and some deposits on parts of baffle plates and delta wing plates. The deposition rate of B-convex surface is higher than that of A-convex surface. In reality, the highly corrosive parts inside of dense flow absorber should adopt wear-resistant materials. Meanwhile, water content of desulfurized fly ash should be controlled to avoid hardening of desulfurized fly ash which is deposited.

Abstract: In order to follow the technical progress in the filed of aeronautics and astronautics, a numerical investigation into flow characteristic of two-phase flow under high gravity (hi-g) condition is performed. Using the CFD code CFX, the two-phase flow in orthogonal pipe under high gravity condition has been evaluated, and the effects of hi-g on two-phase flow characteristic have been analyzed. Compared with the static condition, the flow pattern, volume fraction, velocity and pressure distributions, pressure drop through the pipe are quite different under hi-g, depending on the magnitude and direction.

Abstract: Blade element momentum (BEM) theory is used to design the tidal stream turbine in this paper. ANSYS-CFX and numeca are used to predict the hydrodynamic performance of the turbine. The power coefficient of the turbine obtained by CFD is 39.36% at the design tip speed ratio. A 300mm diameter scale turbine has been built, and the tests were carried out in the circulating water channel, the power coefficient can reach 40.5% at the design tip speed ratio. Through the comparisons between experimental results and CFD results, it proves the application of the numerical method for blade design, and the distributions of the pressure and axial velocity near the blade are analyzed at the end of the paper.

Abstract: This paper presents the numerical predictions of 3D CFD rotor computations of an 800mm diameter model of marine current turbine (MCT). In the paper CFD is applied to a rotor at stationary hydrodynamic conditions Simulations from the numerical prediction are compared with experimental measurements of the model of MCT which is experimented on in a cavitation tunnel and a towing tank. The experimental data includes measurements of power and thrust generated by the turbine, in both a cavitation tunnel and a towing tank, for a series of blade pitch settings and speeds. The numerical predictions show similar results and provide a satisfactory representation of the experimental turbine performance.

Abstract: Various flow bifurcations are investigated for two dimensional combined mixing and separating geometry. These consist of two reversed channel flows interacting through a gap in the common separating wall filled with porous media of Newtonian fluids and other with unidirectional fluid flows. The Steady solutions are obtained through an unsteady finite element approach that employs a Taylor-Galerkin/pressure-correction scheme. The influence of increasing inertia on flow rates are all studied. Close agreement is attained with numerical data in the porous channels for Newtonian fluids. Keywords: mixing-separating geometry, flow bifurcation, porous media, finite element method, Newtonian fluid.

Abstract: The steam jet vacuum refrigerant device works through the water three state physical change processes, and translates potential energy of low-pressure and low-grade steam into kinetic energy as power source, makes low temperature water above 0°C by water as refrigerant and coolant. The design principle of the device follows the first, the second law of thermodynamics and flow continuous law of hydromechanics, the device adopts installation method of air bridge type, waste heat of steam pressure during 0.05~0.3MPa is source of power,the system adopt 3 effect instead of traditional 2 effect in order to achieve the purpose of energy saving operation, COP value of the refrigerating system is greater than 0.8, refrigerating output of single sets is more than 6000kw. The device is consists of evaporator, the main ejector, the main condenser, auxiliary ejector, auxiliary condenser, water jet and gas-distributing cylinder. And application directions of the type device are studied.