Advanced Materials Research Vols. 860-863

Abstract: This paper describes experimental study and numerical simulation of series pulsed nozzle. The simulation of internal flow field in nozzle with different cavity length was carried out by using CFD. The influence of chamber length on the velocity distribution and the axial velocity was analyzed. The simulation results indicate that there is a optimum rang of cavity length producing the maximum outlet velocity. The dynamic pressure of pulsed jet was also studied by using SD150 test system. The effect law of chamber length on the impact pressure of pulsed jet was analyzed. The experimental results show that the peak of hitting power reaches the maximum within a certain range of cavity length. Simulation results are in agreement with Experimental results.

Abstract: The 3-D turbulent particulate-liquid two-phase flow equations are employed in this study. The computing domain is discretized with a full three-dimensional mesh system of unstructured tetrahedral shapes. The finite volume method is used to solve the governing equations and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that the sand erosion rate on pressure side is more than on the suction side of the blade. The maximum value of sand volume fraction and the maximum value of sand erosion rate are at same location.

Abstract: It is well known that the hydraulic drag force on objects cant be ignored in computing the movement of objects in water. And the drag forces on sphere and cuboids have long been studied. While in hydraulic engineering, objects with regular tetrahedron shape are widely used to form the foundation and temporary dam for they can interlock each other to obtain a compacted integral. In this article the vertical hydraulic drag force on regular tetrahedron is studied by indoor experiments, the relation of the vertical hydraulic drag coefficient and the vertical velocity is proposed. And the max vertical speeds of different materials are deduced. The result is helpful to compute the movement of regular tetrahedron in water and estimate the impact effect on the groundwork.

Abstract: The aerodynamic forces of two typical iced conductor models are obtained by high frequency balance technique in wind tunnel test. The effects of wind directions and turbulence intensity on aerodynamic forces coefficients are discussed. An analytical expression for predicting the galloping instability trends in arbitrary directions is derived. An aerodynamic model considering the dynamic swing is developed according to the quasi-steady theory. Galerkins procedure is employed to discrete the governing equations of transmission line, which is modeled as a suspended homogeneous elastic cable having a small equilibrium curvature and neglecting the shear deformation. The forth order Runge-Kutta method are applied to obtained the approximate numerical results of iced transmission line galloping.

Abstract: The olivary flowmeter, a new type of differential pressure flowmeter, was presented. Its pressure loss was explored through experimental research. The experimental medium is diesel. In the condition of the same effective area of circulation, the pressure loss of the olivary and the orifice plate flowmeter was compared. As a result, the pressure loss of the olivary flowmeter is 14.9% of the orifice plate flowmeter at most, 7.2% on average. The olivary flowmeter can reduce energy consumption.

Abstract: The normal operation of the hydropower station is seriously affected by the vibration problems. This paper is about how to analysis and improve the hydraulic vibration problem by an example of a low head Francis turbine in the southwest of China with higher head. The models was built by using UG and analysed by CFD numerical analysis software to simulate the vibration conditions with air-water two-phase flow. With the reason was found by the the result of numerical calcuate, air compensation method was put out to improve the vibration condition and the optimal volume of the compensative air was calcuated to verify the solution method.

Abstract: A low head hydropower station is in the southwest of China, its Francis turbine ran well at a rated power and rated net head, but the turbine produced severe abnormal vibration and noise at higher head than the rated head, full load and overload. By analyzing, characteristic points on vibration conditions are inside the area of channel vortices on runner performance curve. CFD analysis indicates that unstable vortices exist between runner blades. The two results demonstrate that the vibration and noise of Francis turbine are caused by runner channel vortices at higher head than the rated head, full load and overload.

Abstract: With the development of oil storage tank is towards large-scale, boilover is becoming a greater threat to surroundings. The main damage form of boilover is high-temperature thermal radiation and boil-over in oil tank fires. Among them, boil over can cause great casualties and property losses, and easy to cause the disaster spread. This article first analyzes the influence factors of boilover and the intensity, then further creates radius calculation model for boilover. By calculating and analyzing the boilover radius of tank with different sizes and oils stored, the accuracy of model is verified. The results also indicate that the model is effective and the calculating error is fairly small when the tank diameter is less than 10m, otherwise is suitable for simple estimate only. The influence of water content in oil and the viscosity on boilover radius is non-linear, and there is a maximum.

Abstract: The fan pump hydraulic system of amphibious assault vehicle is prone to fault , an pump leakage model is established by principal component regression. This new modeling strategy can effectively extract on the components which have a strong explanatory role of the dependent variable, it achieves regression modeling in multiple arguments correlation conditions, and allows the inclusion of all the original variables. This model get rid of drawback that the least squares regression can not effectively identify and eliminate the influence of the multiple relativity among factors.

Abstract: The numerical simulation of internal flow field of a mixed-flow fan was carried out on the star-CD platform. Three-dimensional steady turbulent flow is calculated using the standard k-ɛ turbulence model, and the pressure distribution, velocity distribution and other important flow phenomenon inside the fan are obtained. The number of meshes has important influence on the result, meanwhile, fan inlet, impeller, outlet interact with each other. The results of numerical simulation can accurately analyze the fan flow field. The results of numerical simulation can accurately analyze the fan flow field structure, and provide guidance for further optimization and improvement of the fan.