【作者】 张晶；

【导师】 赵力；

【作者基本信息】 天津大学 ， 动力工程（热能）（专业学位）， 2016， 硕士

【摘要】 在有机工质热力循环系统中,气液两相工质的分离往往是必不可少的,因此气液分离器在热力循环中具有广泛应用价值及重要性。在众多不同结构、不同原理的气液分离器中,T形管相比其他气液分离器具有结构简单,紧凑性强,易与系统集成,成本低廉等优势,并已被证明其有效性,因此是一种较有前景的分离装置。本文以T形管内有机工质气液两相分离作为研究对象,旨在了解并建立T形管内相分离相关理论以及数学模型,明确T形管作为气液分离器的分离性能,研究T形管相关参数对T形管相分离性能的影响。因此本文从数值模拟及实验研究两个角度对T形管内有机工质相分离进行研究与分析。由于T形管内相分离受入口流型的影响很大,因此本文首先对一种特定的流型----环状流在T形管前端的直管段内的流动情况进行了数值模拟建模工作,模型考虑环状流中液滴的夹带和沉积作用,利用CFD方法对直管内环状流动进行数值模拟工作;随后,本文接着对顺流型T形管内有机工质环状流相分离建立了数学模型进行数值模拟工作,模拟中利用欧拉模型对气液两相流进行描述,同时考虑相间阻力的作用;然后,本文又针对作为有机工质气液分离器的竖直撞击型T形管的相分离性能进行了实验研究。实验工质为R134a和R245fa,实验中利用高速摄影仪拍摄了T形管上出口流型,获得了上出口雾状流到搅混流的流型转变界线,与此同时实验研究了不同T形管入口干度以及入口质量流量对出口参数、气相分离效率、液相分离效率的影响;最后,本文尝试推断了竖直撞击型T形管内有机工质相分离的相关理论及数学模型。全文主要结论如下:(1)直管内环状流数值模型能够较好的预测环状流相关参数以及各参数随入口参数的变化趋势。(2)顺流型T形管的相分离数值模型能够对T形管侧管液相质量流量比LF在0.2到0.6之间的工况给出较好的分离参数预测值。(3)对于顺流型T形管相分离而言,有机工质间的差异以及饱和温度的变化对相分离参数的影响较小;T形管入口质量流速对相分离参数的影响较大。(4)对竖直撞击型T形管内有机工质气液分离效率进行的实验研究中发现:T形管入口处于小流量及小干度情况下,T形管上出口处于雾状流流型,当入口流量及入口干度增大到一定程度后,T形管上出口由雾状流转变为搅混流;基本上,T形管液相分离效率随入口干度的增大而逐渐减小,同时入口质量流量越大,液相分离效率越低;T形管上出口流型对液相分离效率起到了决定性作用,当处于雾状流时,T形管液相分离效率几乎均在90%以上。更多还原

【Abstract】 Gas-liquid separator is of importance and widely-used in the thermodynamic cycle since it is always requisite.Among the different types of gas-liquid separators,T junction is much simpler,compacter,more integrated and cheaper compared with other separators.What’s more,the effectiveness of the T junction has already been proved.Therefore,it is a promising separating device.In the paper,gas-liquid two-phase separation in the T junction is regarded as the study object,which is aimed at understanding and establishing the phase-separation theory and numerical model in the T junction,making the T junction phase-separation efficiency clear,and studying the influence of the T junction parameters on the phase-separation efficiency.Thus,the investigation and analysis of the T junction phase-separation for the organic working fluid are unfolded based on the numerical study and experimental exploration.Because of the significant influence of the inlet flow pattern on the T junction phase-separation,this paper firstly conducts a numerical simulation of a specific flow pattern----annular two-phase flow which always takes place in the straight pipe before T junction.The entrainment and deposition process of the droplets in annular flow is considered in the CFD model of the annular flow.Secondly,the numerical model of the annular two-phase flow separation for the organic working fluid in the run-type T junction is established in this paper.The numerical simulation is conducted,in which the Eulerian model is applied to describe the gas-liquid two-phase flow and the interfacial drag is taken into account.Thereafter,the experimental investigation of the phase-separation performance in the vertical impact T junction which is used as a gas-liquid separator is conducted.The working fluids that are studied in the experiment are R134 a and R245 fa.The high-speed camera is employed to shoot the flow pattern in the upper outlet of the vertical impact T junction in order to obtain the transition line of the flow pattern from mist flow to churn flow.In the meanwhile,the influence of the inlet quality and inlet mass flow rate of the T junction on the outlet parameters,vapor separation efficiency and liquid separation efficiency are studied and analyzed.At last,the attempt of building the phase-separation theory and mathematical model of the vertical impact T junction for the organic working fluid is put forward in this paper.The main conclusions of the whole paper are presented below:(1)The numerical model of the annular flow in the pipe could well predict the flow pattern of the annular flow and the variation trends of the parameters along with inlet parameters.(2)The simulation of the phase-separation of the annular flow in the run-type T junction is capable of prediction for the side-arm take-offs in the range of theLF between 0.2 and 0.6.(3)For the phase-separation of the run-type T junction,the difference of the working fluid and the change of the saturated temperatures have a little effect on the side-arm take-offs.However,the inlet mass flow rate of the T junction has a significant effect on it.(4)It is found in the experiment that the upper outlet of the vertical impact T junction is in mist flow when the inlet quality and inlet mass flow rate are relatively small.Instead,the upper outlet of the T junction changes into churn flow from mist flow when the inlet quality and inlet mass flow rate increase to some degree.Basically,the liquid separation efficiency of the T junction decreases with the rise of the inlet quality.And the liquid separation efficiency becomes lower with the increase of the inlet mass flow rate.The flow pattern of the upper outlet is critical to the liquid separation efficiency.It is proved that the liquid separation efficiency is almost up to 90% when the upper outlet is in mist flow.更多还原