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1、南京理工大学 硕士学位论文 临界流流量计的研究与设计 姓名：杨启超 申请学位级别：硕士 专业：工程热物理 指导教师：陈少松 20080609 AbstractThe critical flow meter is applied to flow measurement, flow control and calibration of flow meter. There are far-ranging studies for it with the methods Abstract临界流流量计的研究与设计of theory and experiment for a long time at hom
2、e and abroad. Recently, along with the development of computer technology, the numerical simulation of critical flow meter is being more attentioned. And with regard to the secondary instrument of critical flow meter, the intelligent flow display instrument which is based on single-chip is being app
3、lied more and more.This study includes three parts. Initially, numerical simulation research for critical flow nozzle with software FLUENT was carried out, it mostly contains the influence of structured parameters on the actual flow and the influence of the expansion segment on the critical back pre
4、ssure ratio.Then, according to the result as above, the figure structure and assembly method of critical flow nozzle were designed. The relationship between the discharge coefficient and the Reynolds number was calculated with software FLUENT. And curve formula was given.Thirdly, secondary instrumen
5、t of critical flow meter based on MCS51 single-chip was designed. This equipment is made up of temperature sensor, pressure sensor, A/D converter, single-chip, fluid display screen and around circuit, with the functions of date collection, flow calculation and flow display.The results of numerical s
6、imulation indicate: the radius of convergence arc and the lengths of throat column influence the actual flow obviously, not other parameters; The critical pressure ratio will enhance with the increase of expanding segments length, decrease with the increase of expanding angle. The test of the second
7、ary instrument of critical flow meter which was designed in this article indicates that it can complete the functions requested, and the tolerance can be accepted.Key word： critical flow nozzle, numerical simulation, discharge coefficient, critical back pressure ratio, secondary instrument 图表目录图 1.1
8、.1.1 拉瓦尔喷管的流动特性 .1图 2.1 临界流文丘里喷嘴基本结构图 .8图 2.1.1 计算参考模型 .8图 2.2.1 喷嘴收敛段圆弧半径与喷嘴流量的关系 .10图表目录临界流流量计的研究与设计图 2.2.2 喷嘴收敛段圆弧角度与喷嘴流量的关系 .10图2.2.3喷嘴喉部圆柱段长度与喷嘴流量的关系.10图2.2.4喷嘴扩张段长度与喷嘴流量的关系. 图2.2.5喷嘴扩张半角与喷嘴流量的关系.图 2.2.6 圆柱段边界层增长示意图.图2.2.7不同收敛段圆弧半径的边界层示意图图2.2.8r=0.2d的速度矢量图 .图2.2.9r=2.0d的速度矢量图.图2.3.1.1喷嘴流量与压力比的关
9、系曲线.图2.3.2.1喷嘴扩张段长度与临界背压比的关系.14图 2.3.2.2 喷嘴扩张半角与临界背压比的关系 .14图 2.3.2.3 不同扩张半角的边界层分离 .15图3.1.1喷嘴及上游管道的结构 .16图3.2.2.1喷嘴流出系数和喉部雷诺数的关系.18图4.1.1流量计二次仪表总体结构图 .20图图4.2.1 80C51单片机的基本组成单片机的基本组成.21图4.2.2单片机外围及按键接口电路 .22图图4.3.1.1Ptl00测温电路测温电路.23表4.3.1.1测温电路输出电压和温度及阻值的对应关系.24图4.3.1.2输出电压和温度的关系图.24图图 4.3.3.1 INA1
10、22 结构图结构图.26图 4.3.3.2 温度测量信号放大电路 .26图4.3.3.3压力测量信号放大电路.27图图 4.3.4.1 AD7706 内部结构内部结构 .28图图 4.3.4.2 AD7706 弓弓I脚图脚图.28图图4.3.4.2 AD7706与单片机连接图与单片机连接图.29图图 4.3.4.3 AD7706 接口接口 电路图电路图.30 图图 4.4.1 SMC1602A 液晶液晶30表表 4.4.1 SMC1602A 接口说明接口说明.31图图4.4.2 SMC1602A与单片机连接图与单片机连接图 .31图5.1.1 二次仪表软件程序流程图.33图5.2.1参数设置程序流程图 .34表表5.3.1.1 AD7706通信寄存器通信寄存器.35表表5.3.1.2 AD7706设置寄存器设置寄存器.35表表5.3.1.3 AD7706时钟寄存器时钟寄存器.36表表 5.3.2.1 SCON 寄存器寄存器 .36图表目录临界流流量计流量计的研究与设计VII图图5.3.2.1写数据流程图写数据流程图.38图图5.3.2.2读数据流程图读数据流程图.38图图5.3.3.1 AD7706数据转换流程图数据转换流程图.40表表5.4.1.1空气的空气的C.值值 .41表表5.5.1.1 SMC1602A状态字
