【作者】 代玉强；

【导师】 胡大鹏；

【作者基本信息】 大连理工大学 ， 化工过程机械， 2010， 博士

【摘要】 天然气处理、输运过程中常采用节流制冷工艺,这会导致压力能的巨大浪费。国内油、气田的生产实践表明,基于振荡流动过程的高效气波技术装备,如气波制冷机,在天然气制冷、深冷工艺中具有优越性。但在高压、大膨胀比场合效率降低,设备积液导致制冷失效,气流脉动诱发振荡管强烈震动。原因在于,其振荡管一端封闭,滞留气中的凝液难以排出；用于散热的振荡管较长,刚性低,易震动。两端开口振荡管结构能将管内大部分滞留气排出,可提高带液操作能力,减轻设备震动问题。目前,这种双开口结构仅见于气波增压技术,如何利用其进行制冷是一个全新的课题。本文对双开口管转子内气流的非定常流动行为和热效应进行研究,探讨其实现膨胀制冷的机理及应用技术,对丰富和完善气波制冷技术资料有重要意义。论文通过气动力学研究、宏观热力分析和实验研究三种手段,对以该转子为主要部件的气波制冷机的实现技术进行了如下几方面的工作：(1)系统研究了理想气体和高压真实气体在转子通道内的非定常流动,及所形成气体波的运行特性,揭示了双开口振荡管实现的热分离效应规律。鉴于气波机械多用于天然气及高压气处理,本文实现了复合AGA8、BWRS等状态方程的多维流体计算技术,能够对近气液平衡线的多组分气体流动问题进行分析。在此基础上,研究了理想和真实气体的非定常流动,探讨了真实气体产生的各种波的发生、反射、透射等运行规律,得到了真实气体效应对工作点偏离的影响规律,精确确定了实现连续冷热分离的工作波图。利用特征线方法,给出了该制冷机的结构参数(如管长和端口布置)匹配条件；考虑真实气体效应,完成了决定制冷机生产能力的高压端口喷嘴的设计。在上述研究基础上,提出一种外循环耗散式的气波制冷机(Aggregated Thermal Dissipation Gas Wave Refrigerator, AWR),并获国家发明专利(CN200810011257.1)。(2)在深入研究转子通道内气流的非定常流动行为和热分离原理基础上,将制冷机内部工作过程,分为驱动气流的膨胀过程和循环气流的压缩过程两部分,两股气流通过体积功交换能量,提出了完整的制冷机热力学模型。从宏观角度,对制冷性能进行预测,获得了影响制冷机内部过程的热力效率的主要因素。分析后发现,压比小于10时,激波本身的非等熵性对绝热效率影响微小,而进、出端口的非均匀混合、泄漏的影响较大。(3)对气体流动控制方程的时间、空间离散格式进行了对比评价,表明用AUSM系列格式加限制器离散对流项、用中心差分离散扩散项,以及用双时间步格式离散非稳态项,可适用于求解转子通道内部任意气体的全速流动。通过建立单通道和多通道多周期气动分析数值模型,并施加合适的初边条件,对转子通道内流场和端口匹配进行了数值分析。研究了接触面扭曲的产生原因及影响,发现缩短通道开启时间、拓宽高压端口宽度,可增加压缩气流的做功能力,降低接触面前后流体的能量损失。实验测试也证明,膨胀制冷效率能相对提高5%。(4)建立了处理量3×104Nm3/d的压缩空气制冷实验系统,干空气实验膨胀比可达10,带液实验膨胀比可达3。通过对高压端口温度和压力、低温端口压力等的调节,研究了AWR制冷机各端口的热力状态、设备能量交换性能、增压性能、制冷性能以及循环流率比的关系,对制冷样机的结构参数和操作参数的进行了优化匹配研究。研究发现,过程效率的降低主要受驱动、被驱气流的掺混和泄漏,以及受质量交换引起的能量损失、通道与端口连通或关闭过程造成的流动不均损失等影响。高温端口开启时刻对设备制冷性能具有重要影响,用于制冷时,应避免反射激波返回驱动气流中。通过实验,使制冷机的等熵效率已达69%。带液运行实验发现,在过饱和含液量7%重量浓度下,机器的运行性能并未明显降低。更多还原

【Abstract】 There is a huge waste of pressure energy in natural gas processing and transport area by using throttling refrigeration process. Based on the unsteady flow theory, high efficiency wave equipments such as gas wave machines have huge advance in such processes. Many practical applications of gas wave machines in domestic oilfield show that when operating under high pressure and large expansion ratio conditions these machines have the problems of vibration induced by pulsing gases and refrigeration performance reduction by liquid accumulation, which adversely affect the operation stability and reliability. The main reason is that the rest gases in the unilateral closed pulse tubes cannot empty intirely, and the long pulse tubes vibrate with small stiffness. Bilateral opened pulse tube rotors used for superchargers and gas engines formerly has double sided open structures, which has no problem of vibration or liquid accumulation. At the time being, how to use wave rotor in expansion refrigeration area is a novel project.A study on the flows and refrigeration principles of bilateral opened pulse tube has made in this dissertation. It is of great importance for enrichment and improvement of gaswave refrigeration theory. This research has presented a detailed implementation of technology of gaswave refrigeration from aspects of gas dynamics analysis, thermodynamic analysis and experimental evaluation and validation.(1) The unsteady flow and gasdynamic wave’s propergation properties has studied in detail. In addition, the thermal separation effects in rotor passages have explored. Used for processing of high-pressure natural gases, wave refrigerators often operate in the nonideal thermodynamic regions. A real gas dynamic computational fluid dynamic (CFD) model coupled with equations of state like AGA8, BWRS, etc has established for discussing the flow patterns of of unsteady flows, which can calculate the flow of low heat capacity natural gases located in vicinites of gas-liquid equilibrium line. Based on this, the origination, reflection and refraction rules of various arbitrary gasdynamic waves in rotor passages have explored. The influence of real gas effect on offset-design of the refrigerators has acquired. A corrected wave diagram based on real gas models has ascertained which has laid a theoretical foundation of performance assessments and designs of wave rotor refrigerator.Based on the above studies, a novel novel refrigerator named Aggregated Thermal Dissipation Gas Wave Refrigerator (AWR) has proposed. The AWR now has the Chinese Patent (CN200810011257.1). Design scheme based on method of characteristics for key structure parameters matching condition like port timing layout has worked out.Taking real gas effect into account, area design method of high-pressure port has realized.(2) A novel thermodynamic analytical model for AWR has established based on the following assumptions:there is no mass transfer across contact face, which separates the inner whole process into expansion process of driving gases with compression one of driven gases; the two streams directly exchanger energy though volume work. This performance assessment model shows the main contributing factors of inner thermal processes. Studies on main factors of expansion and compression processes have indicates that when expansion ratio bellows 10, the inner non-isentropic characteristics of shockwaves are nonsignificant while other factors such as non-uniform mixing in ports and leakages (including mass transfers of driving and driven streams) are of concernment.(3)Comparison evaluations of numerical discrete schemes for control equations show that the density based model with AUSM series schemes and appropriate limiters to discrete advection items, center difference schemes to discrete vicious items and dual-time step scheme to discrete unsteady items is applicable to full speed interior flows of real gases in wave rotors. Mono-pipe and multi-pipe numerical model and initial-boundary conditions have been set up to simulate the flows and port timing analysis of AWR. Particular reasons and solutions of shockwave and contact face distortions has indicated that short opening time and wide high pressure port will get higher refrigeration performance. Moreover, experimental results have verified that wide high-pressure (HP) port and appropriate incidence angle can improve about five percents of expansion efficiency relatively, with higher compression efficiency at the same time.(4)A dry-air refrigeration test rig of AWR with expansion ratio less than 10 and a fluidic test rig less than 3 have built. A number of experiments on axial-flow AWR prototypes by adjusting temperature and pressure of high temperature (HT) port and pressure of low temperature (LT) port has performed to get thermal states of other ports. Relations of exchanging work, supercharging and refrigerating performances and circulation flux ratio show that expansion efficiency are affected by mass transfer (mainly gas mixing and leakages) and energy exchange (losses from mass transfer and non-uniformity flows in ports) between driving and driven flows. The following conclusions from laboratory studies are fruitful: location of HT port has important influence on the refrigeration performance, and a reflected shockwave compression process may not feasible for rotors used for refrigeration.In lab, the isentropic efficiency of AWR now can get 69%. Actual liquid experiments show that AWRs have excellent fluidic operation performance:the refrigeration properity remains almost unchanged even if AWR operates with 7% liquid ratio.更多还原