a b s t r a c tThe L-shaped junctions in running and gating systems used in aluminum gravity casting have been investigated. Using computational modeling, a guideline for constructing two geometries of L-junctions was developed. The sequential filling profile of liquid metal along L-junction was confirmed by real-time X-ray video of an aluminum alloy sand casting. The change of flow direction through L-junctions can yield a high coefficient of discharge Cd, without entrapping detrimental oxide film defects because of the smooth flow, minimizing surface turbulence. A short "clear-up" time, the duration of filling a component, of L-shaped junction is also achieved. For the necessary of future application of this junction, its dimensionless equivalent lengths (L E /D) and loss coefficient K were estimated. The main aim of this work was to eliminate the trial and error approach as designing a multiple-gate system. From the guideline of L-junction, the two junctions can be assembled into a complex multiple-gate runner system. In this novel design of multiple-gate system, uniform distribution of flow through each gate into a mould cavity has been demonstrated. A high Cd value was also predicted.
A novel runner system design, named a Vortex-Gate, has been explored for aluminium gravity casting. Using this design, the velocity of flow of the liquid metal was controlled below the critical velocity and, at the same time, a high flowrate was maintained. The flow behaviour achieved did not appear to generate either bifilm or bubble defects. The 'virtual' experiment using a computational modelling package, and the 'physical' experiment, a real-time X-radiography study, were found to be in reasonable agreement.
In gravity casting, the quality of an aluminum alloy casting relies on, among other things, the design of the runner system in which the ingate velocity into the mold cavity should be controlled to stay under a critical velocity (close to 0.5 m/s). In this study, a diffuser was proposed to reduce the velocity of liquid metal to below this critical value, while the flow rate remained almost unchanged. Flow separation and dead zones in the diffuser design were avoided. A computational modeling package and a real casting experiment (water analogy method) were employed for exploring and verifying the new design. The efficiency of the diffuser was quantified by the measurement of coefficient of discharge C d . For this new diffuser, the pressure recovery coefficient C p and the loss coefficient K L were also estimated.
The overflow fusion process was an important method for the manufacture of glass sheet that
is currently used for the production of TFT/LCD display devices. The design of forming apparatus
was critical for very high surface quality of glass to allow the successful application of
semiconductor type material. However, there is only a little of researches had been presented in the
literatures, because of difficulties and expansions in experiments. In this study, a numerical model
for simulation of molten glass flow through the isopipe during overflow fusion process was carried
out. The effect of temperature of forming apparatus and of molten glass on the flow patterns during
overflow fusion process was investigated. It was found that the stability and flatness of sheet glass
was influenced strongly by the temperature of forming apparatus and molten glass. A precise
control of overflow temperature and temperature distribution of isopipe was needed for maintaining
a stable flow and uniform thickness.
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