Advanced Materials Research Vols. 945-949

Abstract: Through the Rough Model Method (RMM) an explicit calculation is proposed to solve the complex problem of the design of a pressurized trapezoidal shaped conduit characterized by three linear dimensions. Firstly, the method is applied to a rough model of the same shape in order to establish the equations governing its geometric and hydraulic characteristics. These equations are then secondly used to easily deduce the required linear dimensions of the current conduit by introducing a non-dimensional correction factor. The application of the obtained relationships requires only a strict minimum of data. All relationships provided in this article are applicable to the entire domain of the turbulent flow. Practical examples are taken to enable the hydraulic engineer to better understanding the advocated method and to observe the facility with which design of such a geometric profile can be performed.

Abstract: Catalytic converter is an important device of automobile engine exhaust system. Based on Hydromechanics, the relational mathematical models of catalytic converter simulation are established and the parameters are calculated. Making use of CFD numerical simulation method, a simulation is set up for the internal flow field of catalytic converter original model using fluent software. From the simulation, the internal flow characteristic is understood. On the basis of this, through the optimization idea adding a guiding device in inlet cone of catalytic converter, the uniformity of velocity of flow is improved. The simulation analysis show that the flow uniformity for internal flow field can be improved observably in the structural optimization, the increasing degree of pressure loss is with little range. A new idea and reference may be offered for improving flow uniformity of a catalytic converter.

Abstract: Under reduced or micro gravity, bubble dynamic behaviors in liquid melts or liquid solutions are important and common problems on optimizing many processes in space science and technology. Due to limited availability experiments under reduced or micro gravity condition, the studies in this area is still quiet fragmentary. For this reason, we develop two pairs of Helmholtz-Maxwell (H-M) coils, which can produce a uniform gradient magnetic field for the ferrofluid filled in a closed Hele-Shaw cell, so as to achieve reduced or micro gravity condition. Afterwards, we establish the multi-physics mathematic model to calculate the magnetic field and the gravity compensation rate, which shows a 30mm×40mm well-distributed region for 90% gravity compensation rate exists.

Abstract: Molecular dynamics method is applied to study the influence of velocity on the properties of fluid film in wedge nanochannel. Studies have shown that: in wedge nanochannel the impact of velocity of solid wall on the maximum pressure in the simulation region is limitation. After the pressure in the simulation region reaches the maximum, it is not increase with the velocity of lower solid wall rising. Due to molecules accumulation the average number of molecules in the simulation region enhance with the velocity of solid wall rising.

Abstract: Cavitation is one of the most important aspects that need to be considered while designing centrifugal pumps, since it is a major contributor to failure and inefficiency. In order to study the cavitating performance in high-speed centrifugal pumps under low flow rates, the pump named IN-32-32-100 with two different impellers was investigated based on numerical and experimental methods. The impeller case 1 is the impeller with six blades. The impeller case 2 is the impeller with four long and four splitter blades. The research results show that the cavities of two impellers occur at the impeller inlet. The region of developed cavities extends and the volume fraction in the blade passages gradually increases with the decrease of inlet total pressure at the flow rate of 0.5Q_d. The cavities distribute asymmetrically in each blade passage and the vapor fraction of one blade passage is significantly larger compared with them of blade passages. The inner flow of the pump can be effectively improved with more uniform pressure distribution by applying splitter blades. The critical cavitation number of the impeller case 1 and impeller case 2 corresponding to the sudden head-drop point are 3.2m and 3.55m, respectively. Compared with impeller case 2, cavitating performance of the pump with impeller case 1 is better. The numerical results agree well with the experimental data, which shows that the numerical method in the present study can to some extent accurately predict the cavitating development inside the high-speed centrifugal pump.

Abstract: By analyzing the pavement hydraulic power generation system working principle and accumulator mathematical model, full account of the system actual operating conditions, use Matlab/Simulink software simulation the accumulator working process, obtain accumulator absorbs shock pressure effect with accumulator body parameters and working parameters relationship.

Abstract: Airfoil has great influence on the performance of axial fan. In order to study performance of axial fan. Four kinds of airfoils have been applied to optimize the impeller of axial fan. The 3D internal flows of the axial fan under different operating conditions were simulated based on a steady numerical method in ANSYS CFX 14.5. The results show that the curve of total pressure of the fan with LS airfoil blades is slightly steeper, and that of the fan with CLARK-Y(C=11.7%) (C is the blade thickness ratio) airfoil blades is relatively flat. The total pressure of the axial fan with CLARK-Y(C=11.7%) blades is highest among others. While achieving the highest efficiency in all the operating conditions except the lowest flow rate. Moreover, the blades loading of the CLARK-Y(C=11.7%) airfoil blades fan is entirely more uniform than that in others. The turbulent kinetic energy distribution on the leading edge of blades shows that the axial fan with CLARK-Y(C=11.7%) airfoil blades fan can improve the turbulent kinetic energy effectively.

Abstract: The complicated cavitating flow inside diesel nozzles has long been concentrated on. Based on the visualization experimental system, cavitating flow characteristic inside transparent nozzles with different length-diameter ratios was investigated in this paper. Experimental results showed that the cavitation is easier to occur for diesel than for biodiesel, and the longer the length of the orifice is, the harder the cavitation and hydraulic flip phenomenon to occur. Discharge coefficient of diesel was higher than that of biodiesel in single-phase flow region, while got much smaller than that of biodiesel in the cavitating flow and hydraulic flip regions.The spray cone angle of diesel was larger than biodiesel in cavitating flow regime, and got much smaller with the increasing of the length-diameter ratios under the same level of injection pressure in diesel and biodiesel fuels.

Abstract: As cavitation inside diesel nozzles can improve the spray characteristics, it has long been a hot issue. And together with the increasing attention of biodiesel, it is essential to identify the difference of cavitating flow characteristics between diesel and biodiesel. What’s more, the hydraulic flip phenomenon and cavitating flow with decreasing injection pressure hasn’t been studied. Based on this, cavitating flow inside transparent nozzles of diesel and biodiesel fuels with increasing and decreasing injection pressure was investigated in this paper. Experimental results showed that are quite different from the disappearance of it and it is harder to disappear. Biodiesel and longer nozzle orifices were hard for the hydraulic flip phenomenon to occur, and the disappearance of hydraulic flip phenomenon has great influence on the spray cone angle and the discharge coefficient.

Abstract: Calculation of a centrifugal water oil separator is shown. The separator represents alternative method of purifying water of oil inclusions and sludge (at a concentration up to 12%). The problems of creating a computational mesh, defining boundary conditions, separation two phases of oil-water emulsion and efficiency of separation are considered.