微细通道高粘流体降压流动沸腾机理及气液两相流动结构研究

The journal bearing, valve and hydraulic equipment were widely applied in many kinds of industrial areas, such as energy, petrochemical, aerospace, precision machinery etc. As we known, micro/mini channels will be formed in these devices. The high viscosity fluid flowing in these channels will boiling during the depressurization process and form gas-liquid two phase flow. It will lead to pressure pulsation, cavitation erosion, make noises and so on. But, it has the potential value such enhancing the ability of heat transfer etc.The research is still insufficiency. Based on the recent development and research focuses, in this proposal, we target to investigate the high viscosity fluid flow boiling induced by depressurization(BIDP,Boiling induced by depressurization) and gas-liquid two phase flow in the micro/mini channels. The two phase flow structure, bubble formation and evolution process, temperature field etc are explored by the high speed camera, infrared thermal imaging camera in this proposal. Based on the experimental results, we will establish the flow pattern map and criterion; we will analyse the nucleation mechanism of BIDP and we will improve nucleation condition model of BIDP.The bubble dynamic 3D CFD model will be set up to anlyse the bubble dynamic behavior characteristics.According to the equation of state, the transient temperatrue,bubble volumn and pressure derivation model will be discussed. It can be used to develop a nonintrusive face measurement method of pressure field.In comparison with flow boiling induced by heat flux, the boiling region and the key point calculating criterion of BIDP will by researched.The research results of this proposal can be applied in the improvement of lubrication theory, the design of hydraulic system,the mechanism of reduce noise theory and so on.

能源石化、航空航天、精密机械等行业中广泛应用的滑动轴承、阀门、液压设备等部件存在着微细量级流道。其中工作的润滑油等高粘流体会由于压力降低产生沸腾及气液两相流现象。一方面产生压力脉动、材料剥蚀、噪音等不利影响；另一方面又具有强化传热等潜在利用价值。相对于流体受热，降压过程相关研究尚不充分。本项目拟从实验、理论研究与数值模拟三方面对微细通道高粘流体降压流动沸腾及气液两相流现象进行深入研究。采用高速摄像、红外热成像等手段研究两相流型及其转换、气泡形成及演化过程、流场内温度、压力分布特性。以实验数据为基础建立流型图及判别准则；分析降压沸腾核化机理，对气泡生成的热力学条件进行修正，建立气泡动力学三维CFD模型；构建气液两相流区瞬时温度、气泡体积与压力的映射模型及压力非侵入式面测量原理模型；确立降压流动沸腾分区及关键点的量化计算准则。项目成果可应用于润滑理论改进、液压系统设计、减噪抑噪原理等研究中。

能源石化、航空航天、精密机械等行业中广泛应用的滑动轴承、阀门、液压设备等部件存在着微细量级的通道。其中工作的润滑油等高粘度流体会由于压力降低产生沸腾及气液两相流现象，一方面产生压力脉动、材料剥蚀、噪音等不利影响；另一方面又具有强化传热等潜在利用价值。本项目从实验、理论研究与数值模拟三方面对降压过程微细通道内高粘流体沸腾及气液两相流现象进行深入研究，整体上达到了既定的研究目标。.考虑到高粘流体的粘性与温度之间的敏感性，课题组通过实验研究，建立了实际油品的温粘特性关联式。由于高粘流体经常处于流动状态，其中溶解裹挟的空气成分为不凝结气体，影响润滑油理化特性及传热传质特性，考虑到“含气量”实际物理意义、使用场合的目的及测试手段的可操作及一致性，课题组以全空气析出量作为“含气量”表征方法并改进了相应实验技术，建立了全空气析出量与测试压力之间相应的关联式。.建立了考虑表面张力及粘性的空泡演化模型，研究了初始空泡半径、粘性及表面张力对线性、周期变化的压力场对空泡演化特性及溃灭压力的影响。.建立了无限宽渐缩-渐扩微细通道库特流气液两相流分析模型，分析了喉部比、壁面速度等因素对流道内流体流型、流动状态的影响。发现流道内空化-动压效应互相耦合，互相影响。壁面速度是影响流道内流型分布、压力分布等特性的关键因素，其影响是非单调的，具有分段性。.建立了三维渐缩-渐扩微细通道（滑动轴承间隙流场）两相库特流求解模型。在此基础上全面分析了工质性质、运行条件、以及轴承的结构参数对流道内的相态、流型、压力分布的影响，在此基础上建立了滑动轴承“动压-空化”反馈耦合模型。NCG能改变“动压”和“空化”之间耦合反馈关系，.在气泡破裂的声学特征提取检测技术方面，根据初步的实验数据可看出：汽泡的突然破裂会激励出共振压力波、产生“N”形声波及喷射波，引起的基底薄板的振动峰值略滞后于声信号出现的峰值；气泡破裂时其声压及振动信号出现相应峰值。声压级最低峰值与汽泡几何形状有关。