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在类合金(NH4Cl-H2O溶液)定向凝固晶体生长实验装置上,利用30μm煤粉作示踪粒子,再现糊状区内微通道流以及通道出口处的流体流动,并测算了各处流体的瞬时速率.分析认为:凝固初期,糊状区内固相体积分数较大,内部流体流动受阻;随着固相体积分数减少,糊状区孔隙率增大,流体充分发展;当平均固相体积分数降至0.42,接近最小值0.38时,当量雷诺数达到临界值(247),糊状区内形成微通道;随着通道宽度逐渐扩大,液相区内热流体进入微通道.微通道内稀冷液体向上流,浓热液体向下流,促使通道内溶液再结晶.
In the experiment of directional solidification crystal growth of the alloy (NH4Cl-H2O solution), 30μm pulverized coal was used as tracer particles to reproduce the flow of microchannel flow in the mushy zone and the exit of the channel, Instantaneous rate.The analysis shows that the volume fraction of solid phase in the mushy zone is large and the internal fluid flow is blocked in the early stage of solidification.The porosity of the mushy zone increases with the decrease of the volume fraction of the solid phase, When the fraction decreases to 0.42 and reaches a minimum value of 0.38, the equivalent Reynolds number reaches a critical value (247), forming microchannels in the mushy zone; as the channel width gradually expands, the thermal fluid in the liquid zone enters the microchannels Liquid upflow, hot liquid downflow, prompting the channel recrystallization of the solution.