【作者】 王刚；

【导师】 王超； 崔广伟；

【作者基本信息】 天津大学 ， 控制工程（专业学位）， 2017， 硕士

【摘要】 音速喷嘴作为一种传统的流量传感器,ISO9300标准已被广泛采用。但是,由于其运行机理非常复杂,目前仍存在很多尚未解决的问题。本文以音速喷嘴温度分布特性为切入点,以传热传质过程为研究对象,围绕“热效应”以及“凝结”现象展开了一系列深入研究。其中“热效应”主要涉及“传热问题”,而“凝结”兼具“传热”和“传质”特性。主要研究工作及成果如下:针对“热效应”传热过程,首先分析了热效应基本原理,涉及热边界层和热膨胀特性。接着以音速喷嘴的管壁温度分布为主要研究对象,建立了管壁动态温度分布采集系统,并利用克里金插值算法得到了喷嘴轴向截面处的温度分布,发现实验中观测到的音速喷嘴管壁最大温降达到了16.5℃。随后建立了基于流固耦合的传热与流体流动数值模型,结合仿真与实验结果,发现“激波分离”现象在分离点后方的壁面附近制造了一片回流区,对管壁起到了“加热”作用,因此管壁温度呈现中间低两端高的趋势。据此,将音速喷嘴管壁分为三个区域,分别是前加热区、冷却区和后加热区,分界点分别为喉部和激波分离点。最后,对激波特性展开研究。结果表明,随着喷嘴压力比增大,激波向喷嘴出口处移动,其位置比理论值更靠近喉部。针对“凝结”传热传质过程,首先建立了含湿气体凝结稳态模型,分析了喷嘴入口相对湿度、温度以及压力对凝结起始点和强度的影响,得到了凝结稳态分布规律。接着建立了考虑粘性的水蒸汽非稳态自发凝结模型,得到了自激振荡频率和流量变化与入口过冷度的关系,并根据凝结产生气动激波的运动规律将凝结自激振荡现象分为三种不同的模式,定量地分析了凝结“非稳态”对流场、质量流量和流量稳定性造成的影响。本研究中自激振荡对流量影响的修正系数最小为0.988,即流量变化量最大为1.2%,需要加以重视。同时,建立了音速喷嘴凝结流实验平台,基于此平台得到了一系列稳态和非稳态实验结果,进一步验证了理论和仿真成果。更多还原

【Abstract】 The sonic nozzle is one of the traditional flow sensors with corresponding ISO9300 standard.As the mechanism of the sonic nozzle is complicated,there are still many problems to be solved.In this paper,in-depth study on the heat and mass transfer characteristics of the “thermal effect” and “condensation phenomenon” of the sonic nozzle was carried out started from the temperature distribution.The “thermal effect” is mainly related to “heat transfer”,and “condensation phenomenon” has the characteristics of “heat transfer” and “mass transfer”.The main research work and results in this paper are as follows:In view of heat transfer process of the “thermal effect”,the basic principle of thermal effect was analyzed firstly,including the thermal boundary layer and thermal expansion properties.Then the dynamic wall temperature distribution was obtained,and temperature distribution of nozzle axial cross-section was interpolated by the Kriging interpolation algorithm.It was found that the temperature distribution is similar “U” with high in amphi and low in middle.The maximum observed temperature drop of the sonic nozzle wall was up to 16.5℃.Then the numerical model was established based on the fluid-structure interaction heat transfer and fluid flow.Combining the simulation and the experiment results,it was found the shock wave separation made a backflow zone,which would heat the wall in the rear of the separation point.Thus,the sonic nozzle wall is divided into three regions,front heating zone,cooling zone and rear heating zone respectively,and the cut-off points are the throat and shock wave separation point respectively.At last,the characteristics of the shock wave were the studied.It was shown that with the nozzle pressure ratio increases,the shock wave moves to the nozzle outlet and the location is closer to the throat than the theoretical value.In view of the heat and mass transfer process of “condensation”,the steady state moisture condensation model was established firstly.The effects of relative humidity,temperature and pressure of the nozzle inlet on the condensation onset point and intensity were analyzed.Secondly,the unsteady state spontaneous condensation viscous model of water vapor was established.The relationship of supercooling degree of inlet with the frequency of self-excitation oscillation and the variation of flow rate were studied.According to the motion mode of aerodynamic shock wave generated by condensation,the condensation self-excited oscillation can be divided into three different modes.The influence of condensation “unsteady state” on flow field,flow rate and stability was analyzed.In this study,the minimum correction factor of the influence of the self-excitation oscillation on the flow rate is 0.988,that is,the maximum variation of flow rate is 1.2%.In addition,the experiment platform for the condensation was set up.Some results of steady and unsteady condensation were obtained which verified the theoretical and simulation results.更多还原