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等直 收缩 扩张 等直 (SCDS)变截面微管道主要应用于微型空间推进器和微型气体涡轮机等微器件中 ,研究其内流动特性对指导上述两种微器件的设计和性能的提高具有非常重要的意义 .采用硅微加工技术在硅片上制作出矩形截面三维SCDS微管道 ,喉部宽度为 16 μm ,深度为 2 0 μm ,收缩比为 1 6 2 5∶1 实验测量了不同进出口压比条件下微管道内氮气的流量特性 .实验设定进出口压比值范围为 1 0— 4 0 ,由此出口体积流量范围为 0— 0 12mL s,流动的特征雷诺数小于 35 0 在实验研究的基础上 ,采用有限体积法对其内部流动特性进行了数值模拟 ,数值模拟结果与实验结果相符合 .数值模拟结果发现两点不同于常规流动的特异现象 :其一为最早出现声速点不在最小截面喉部附近 ,而是移到出口截面附近 ,即声速点的位置发生变化 ;其二为在进出口压比达到 4 0时 ,SCDS微管道内部流场才出现声速点 ,即临界压比值 (这里将管道内部首次出现声速点时对应的当地点压力与进口压力的比值定义为临界压比 )发生变化 .将其原因归结为表面效应 (表面积与体积比值S V)的影响 ,并进一步研究了这两点特异现象与S V值之间的关系 .
Straight Straightening and Scaling Straight Section (SCDS) Micro-sectioned micro-pipes are mainly used in micro-space propeller and micro-gas turbine and other micro-devices. It is very important to study the internal flow characteristics to guide the design and performance improvement of the above two micro-devices .Through the micro-fabrication of silicon micro-fabrication technology, a three-dimensional rectangular cross-section SCDS microchannel was fabricated on a silicon wafer with a throat width of 16 μm, a depth of 20 μm and a shrinkage ratio of 1 6 2 5:1. Than the conditions of micro-pipeline nitrogen flow characteristics.Experiment set the pressure ratio of the import and export of the range of 1 0- 4 0, thus export volume flow range of 0- 0 12mL s, the characteristic flow Reynolds number is less than 35 0 in the experimental study The numerical simulation results agree well with the experimental results by using the finite volume method.The numerical simulation results show that the two phenomena are different from the normal phenomenon of flow: one is the earliest point of sound velocity is not the smallest Section near the throat, but moved to the vicinity of the exit cross section, ie the location of the sonic velocity point. The second one is that when the pressure ratio at the entrance and exit reaches 40, the SCDS micro-pipe The velocity field appeared at the flow field, that is, the critical pressure ratio (where the ratio of the local pressure to the inlet pressure corresponding to the first sound velocity point in the pipeline is defined as the critical pressure ratio) is attributed to the surface effect (surface area And the volume ratio of SV), and further study the relationship between these two specific phenomena and the SV value.