Study on Numerical Simulation of Mold Filling and Heat Transfer in Die Casting Process

A 3-D mathematical model considering turbulence phenomena has been established based on a computational fluid dynamics technique, so called 3-D SOLA-VOF (Solution Algorithm-Volume of Fluid), to simulate the fluid flow of mold filling process of die casting. In addition, the mathematical model for simulating the heat transfer in die casting process has also been established. The computation program has been developed by the authors with the finite difference method (FDM) recently. As verification, the mold filling process of a S-shaped die casting has been simulated and the simulation results coincide with that of the benchmark test. Finally, as a practical application, the gating design of a motorcycle component was modified by the mold filling simulation and the dies design of another motorcycle component was optimized by the heat transfer simulation. All the optimized designs were verified by the production practice.

Numerical Study of Fluid Dynamics and Heat Transfer Induced by Plasma Discharges

A numerical investigation is conducted to explore the evolution of a plasma discharge and its interaction with the fluid flow based on a self-consistent fluid model which couples the discharge dynamics with the fluid dynamics.The effects of the applied voltage on the distribution of velocity and temperature in initially static air are parainetrically studied.Furthermore,the spatial structure of plasma discharge and the resulting force contours in streamwise and normal directions are discussed in detail.The result shows that the plasma actuator produces a net force that should always be directed away from the exposed electrode,which results in an ionic wind pushing particles into a jet downstream of the actuator.When the energy added by the plasma is taken into account,the ambient air temperature is increased slightly around the electrode,but the velocity is almost not affected.Therefore it is unlikely that the induced flow is buoyancy driven.For the operating voltages considered in this paper,the maximum induced velocity is found to follow a power law,i.e.,it is proportional to the applied voltage to the 3.5 power.This promises an efficient application in the flow control with plasma actuators.

THE STUDY ON THE MASS TRANSFER MECHANISM OF EUROPIUM ION THROUGH LIQUID SURFACTANT MEMBRANES

The transfer of trivalent europium ion in a liquid surfactant membrane system is investigated in order toclarify the characteristics of liquid membrane separation process and the availability of this technique forrecovering trivalent lanthanides and actinides.A layered structure model for the emulsion globule is sug-gested.The equations describing the relationship among the effective membrane thickness,the time andother factors are derived and verified experimentally.Results show that under certain conditions the decreas-ing concentration of europium ion in the external phase is proportional to the square root of the time,the acidity of the internal phase and the carrier concentration in the membrane phase.The membrane phase consists of kerosene（solvent）,Span-80（surfactant）and di-（2-ethylhexyl） phosphoricacid（HDEHP,carrier）.The internal phase is dilute nitric acid and the external phase is aqueous solu-tion containing Eu（NO3）3.The mass transfer rate of europium in this system is high and the recovery ofeuropium may be more than 99%.

STUDIES ON HEAT TRANSFER OF FLUID OSCILLATED WITHIN PIPES

This paper is a brief summarization of research achievements about enhanced heat transfer of a fluid oscillated within pipes. Analytical solutions, numerical results and dimensional analyses are summarized and compared with experimental data in the paper. Also, the mechanism of enhanced heat transfer is discussed. It is considered that increase in the effective area of heat conduction and increase in temperature gradient are the main reasons of enhanced heat transfer.

Studies on Solid-Liquid Phase Transfer Equilibrium of Onium Salts(Ⅱ)

The present paper contains the effects of the ammonium ion, counter ion, solvent and anion being transferred on the solid-liquid phase transfer equilibrium constant of quaternary ammonium salts. The most striking difference between solid-liquid and liquid-liquid phase transfer equilibriums is that the length of alkyl chain shows a large effect on the latter but little on the former This means that the chain length affects only the hydrophobicity, rather than the lipophilicity.Keywords Quaternary ammonium salt, Phase transfer catalysis, Equilibrium constant, Hydrophobicity, Lipophilicity

Study on three level system population transfer

Stimulated-Raman-adiabatic-passage (STIRAP) process provides an effective technique to transfer electron population from an initial state (e.g. ground state) to excited final state for both atoms and molecules. In this paper, we present the results of the study on electron population transfer in three level system. We have analyzed the effects of various conditions on the transfer process, such as the time delay of the two laser beams, two-photon off-resonance, one-photon off-resonance and the change of relative laser intensity. The numerical result is compared with experiment, and the reasons for the effects are also given.

Study on the vibrational energy transfer in beam-plate coupled structure

In this paper, a beam-plate coupled structure is discussed. The derivation of exact expressions for power transfer and numerical computation are carried on. It is found that the SEA techniques may be appropriate for strong coupled structures and that the general SEA result provides good agreement with the exact calculation when modal overlap is high. The derived formula is applied to predict the coupling loss factor and vibrational energy of substructures. The agreement between the estimated and measured results presents quite well in most cases.

Studies on the synthesis of amino acids XII.Solid-liquid phase transfer catalytic dicondensation of 1,4-diacety1-2,5-piperazinedione with aldehydes

3,6-Diarylidene-2,5-piperazinediones(2)and 3-alkylidene-6-arylidene-2,5-piperazfnediones (6)were synthesized from diacetyl-2,5-piperazinedione(1)under solid-liquid phase transfer catalytic conditions.2 could be easily convered to a-amino acid by reducing with zinc powder and hydrolyzing with concentrated hydrochloric acid.The effect of different phase transfer catalysts and reaction con- ditions were studied.