【作者】 刘培启；

【导师】 胡大鹏；

【作者基本信息】 大连理工大学 ， 化工过程机械， 2009， 博士

【摘要】 气波制冷机作为一种膨胀制冷设备,具有制冷量大、运行周期长、节能、操作维修方便、带液运行能力强等特点。已应用于油田气轻烃回收、天然气脱水、化工厂尾气回收或废气净化等领域。但目前国内外气波制冷机相关的报道较少,相关报道多以针对性较强的实验研究为主,缺少系统和深入的理论及实验研究,气波制冷机的性能有待于进一步提高。据此,本文建立了完善的气波制冷机实验平台,并结合数值分析方法,对气波制冷机振荡管内波系运动和传热行为进行研究,以探寻提高气波制冷机性能的途径。通过研究振荡管内波系的运行状况,确定了气波机实现极值等熵制冷效率的操作条件,并给出了极值射流频率的预测方法:通过研究振荡管内传热行为,确定了振荡管的壁温分布及其随各参数的变化规律,提出了对冲型均直振荡管:通过研究对冲型均直振荡管的性能,对该振荡管的结构进行有效地改进,确定了性能更佳的对冲型阻尼振荡管:通过研究不同参数条件下采用对冲型阻尼振荡管气波机的制冷性能,掌握了该气波制冷机的运行规律。本论文的主要研究工作及所形成的主要结果与结论如下:(1)设计加工了气波实验整机和多管系气波实验机,建立了边界条件可灵活改变的气波制冷机实验平台,减小了实验机与工业机之间的差异,可较好地完成振荡管内瞬态压力、振荡管外壁温度、机器制冷性能及其结构优化等实验工作。采用滑移网格技术,建立了多管、多周期的数值分析模型,并加入实验测得的管壁温度,避免了振荡管的初始和边界条件不准确的问题,克服了振荡管内非定常传热达到热平衡状态所需计算时间长、累计误差大的缺点,此数值模型经实验验证与实验结果吻合良好。(2)对振荡管内波系运行状况和传热行为进行了模拟计算,并借助于实验手段,对一端封闭的均直振荡管内流动进行了深入研究。研究发现:管内激波与喷嘴结构之间存在最优匹配关系是振荡管制冷性能存在极值现象的主要原因;数值分析能够理想地预测气波制冷机的极值射流频率。激波扰动能够引起管内气体与管壁之间的传热量迅速增加,是影响振荡管壁温分布的主要因素;由于膨胀波的作用,使振荡管内激波扰动存在一定的范围,该扰动范围能够诱发振荡管壁温出现跳跃和封闭端回升现象。(3)通过振荡管壁温分布的分析发现,波系对冲有利于管内气体能量的外输耗散,据此提出了对冲型均直振荡管结构。研究表明:该振荡管能够加强管内波系能量的消耗,改善振荡管壁温分布,使振荡管的管长利用率和制冷性能均得到提高。对冲型均直振荡管中有透射激波到达管入口端,使其制冷性能存在较明显的极值现象。两对冲型均直振荡管内波系运行状况存在差异,当来自于第一振荡管的透射激波到达第二振荡管入口时,第二振荡管入口处于被喷嘴前沿封闭的状态是对冲型均直振荡管实现极值等熵制冷效率的条件。(4)在确定了截面突扩结构——激波吸收腔的削弱激波性能随结构参数变化规律的基础上,结合激波吸收腔直径对气波制冷机体积的影响,提出了串联吸收腔结构。研究表明:串联吸收腔能够吸收入射激波能量,并将其反射为膨胀波,消除了反射激波对振荡管制冷性能的不利影响,机器制冷性能得到了提高;反射膨胀波能够引发二次入射激波,使反射膨胀波与喷嘴结构之间存在一定最优匹配关系,由于二次入射激波较弱,反映到制冷性能上,串联吸收腔振荡管效率曲线平坦:反射膨胀波到达振荡管入口时,振荡管入口处于封闭状态是串联吸收腔振荡管实现极值等熵制冷效率的条件。(5)综合对冲耗散和阻尼吸收不同的两种削弱激波强度的思想,提出了对冲型阻尼振荡管结构。研究表明:该振荡管克服了对冲型均直振荡管内波系运行状况存在差异的缺点,吸收了对冲型均直振荡管和串联吸收腔的优点。与一端封闭的均直振荡管相比。振荡管的管长利用率和制冷性能均得到提高,等熵制冷效率提高可达15%以上,其中极值制冷效率点提高5%左右。对冲型阻尼振荡管中的阻尼腔结构能将入射激波反射为膨胀波,使振荡管制冷性能和流量曲线均变得较平坦,提高了振荡管变工况的工作能力。对冲型阻尼振荡管实现极值等熵制冷效率的条件为:反射膨胀波到达振荡管入口时,振荡管入口处于封闭状态。(6)分别对膨胀比、压力值、喷嘴宽度和喷嘴射流角度等参数对对冲阻尼型气波制冷机制冷性能的影响进行了实验研究,并对其影响机理进行了分析,掌握了对冲阻尼型气波制冷机的运行规律,为其工业应用提供了基础保障。更多还原

【Abstract】 Gas Wave Refrigerator(GWR),a kind of gas expansion refrigeration equipment,has many features such as high throughput,long operation period,low cost,easy operation,simple maintenance and good anti-erosion against drops or particles.At present,GWR has already been used in light hydrocarbon recovery from oil-field gas,natural gas dehydration,chemical plant exhaust or waste gas purification,scientific research,etc.However,little research work on GWR has been done,and the previous work focused only on the experimental research for some special cases.A systemically theoretical and experimental research has not been reported, and the performance of GWR needs to be improved for enlargement of application area.This dissertation is aimed to explore a method for improvement of GWR performance.An experimental platform and a numerical model are established to study the wave motion and heat transfer behavior inside oscillating tube.By the study on the wave motion inside oscillating tube,the operational conditions when GWR achieves the extreme refrigeration efficiency are determined,and a prediction method for extreme jet flow frequency is put forward.By the study on the heat transfer behavior inside oscillating tube,the tube wall temperature distribution and its parameter influences are obtained,and Intersection Oscillating Tube(IOT) is proposed. By the study on IOT performance,IOT structure is effectively improved,and Intersection Damp Oscillating Tube(IDOT) is determined because of its better performance.By the study on parameter influences on the refrigeration performance of GWR with IDOT,the operation principles of this GWR are obtained.The main research work and achievements are as following.(1) Two experimental machines,60-tube whole machine and multi-tube series machine, are designed and produced.The GWR experimental platform with changeable boundary conditions is set up.Thus,it is possible to complete many experimental works on oscillating tube,such as the inner transient pressure,the outer wall temperature,the refrigeration performance and the structure optimization.Besides,the differences between experimental GWR and industrial GWR can be reduced.A numerical model of GWR is set up using sliding mesh technique,and the tube wall temperature distribution which is obtained from experiments is considered.This model can complete the multi-period computation,and simulate the influence of the adjacent oscillating tubes.It can overcome the disadvantages of the conventional model such as inaccurate initial conditions and inaccurate boundary conditions,and make up for the deficiency of long computing time and big accumulated error for oscillating tube to achieve thermal equilibrium. The numerical model is verified by experiments and it is in good agreement with the experimental results.(2) The flow inside the oscillating tube is investigated by the numerical and experimental study on wave moving status and heat transfer process.The results show that,the existence of extreme refrigeration performance is mainly because of the optimal match relation between shock wave and nozzle structure.The numerical analysis can ideally forecast the extreme jet frequency of GWR.As the shock wave disturbance inside oscillating tube can cause the rapid increase of gas temperature and heat flow rate of the inner wall,it is considered as the main influencing factor of the wall temperature distribution.As there is a disturbance range for shock wave inside oscillating tube,the jumping and rebound phenomena appear in the tube wall temperature distribution.(3) By analyzing the wall temperature distribution of oscillating tube,the intersection dissipation phenomenon of waves has been detected under the higher order extreme jet frequency.Then,Intersection Oscillating Tube(IOT) is put forward and its internal flow and refrigeration performance are studied.The results show that the utilization ratio and refrigeration performance of oscillating tube have been enhanced by using IOT.As IOT can not eliminate the shock wave,there are still the obvious extreme phenomena in refrigeration performance.When the second oscillating tube of lOT achieves the optimal match relation between shock wave and nozzle structure,the extreme isentropic refrigeration efficiency appears.(4) The structural parameter influences on weakening-wave performance of the expansion chamber(a sudden-expansion structure) are investigated.Then the oscillating tube with series expansion chambers is proposed considering the effect of chamber diameter on the GWR volume,and its internal flow and refrigeration performance are studied.The results show that, series expansion chambers can absorb the injected shock waves,and the reflected waves are expansion waves.Therefore,the refrigeration performance of oscillating tube is enhanced and its change range with jet frequency becomes small.For the reflected expansion waves can cause the second injected shock waves,there is the optimal match relation between the reflected expansion waves and nozzle structure,leading to the slight extreme phenomena in refrigeration performance of oscillating tube with series expansion chambers.The oscillating tube inlet has already been closed by the nozzle forehead when the reflected expansion waves get to the inlet, which is the condition for oscillating tube with series expansion chambers to achieve the extreme isentropic refrigeration efficiency(5) IDOT is put forward by combining two weakening-wave methods,intersection dissipation and damp absorption,and its internal flow and refrigeration performance are studied. The results show that IDOT has the merit of IOT and oscillating tube with series expansion chambers,makes up for the deficiency of IOT in match relation.Comparing with the straight oscillating tube,the utilization ratio and refrigeration performance of IDOT are enhanced,the increase of isentropic refrigeration efficiency may reach above 15%to the most and the peak efficiency has increased more than 5%.The refrigeration performance and the throughput of IDOT are both more stable because the reflected wave is expansion wave.The extreme isentropic refrigeration efficiency of IDOT can be achieved if its inlet has already been closed by the nozzle forehead when the reflected expansion wave gets to the inlet.(6) The influences of some parameters,including expansion ratio,pressure value,nozzle width and nozzle jet angle,on the refrigeration performance of GWR with IDOT are investigated,and the influence mechanisms are analyzed.Furthermore,the operation law of GWR with IDOT is found,and its industrial application is guaranteed.更多还原