【作者】 张仲；

【导师】 胡大鹏；

【作者基本信息】 大连理工大学 ， 化工过程机械， 2011， 硕士

【摘要】 在工业生产中,旋转式气波制冷机作为一种膨胀制冷设备,具有处理量寺、成本低、运转平稳、操作维护方便、使用寿命长、节能和能够适应气液两相流等优点。但也存在一些问题,如设备体积庞大、振荡管利用率低、震动剧烈,并且研究表明随着射流频率的变化,旋转式气波制冷机的等熵制冷效率出现大幅度波动,不利于其稳定运行。针对这些问题,本文采用实验与数值模拟相结合的方法,对旋转式气波制冷机关键部件——振荡管结构进行了改进,提出了突扩连通结构振荡管。获得了突扩连通结构振荡管内波动瞬态压力、壁温、射流频率、膨胀比、出口压力等参数对振荡管制冷性能的影响,了解了传热行为和内部波系流动的规律,寻找出提高旋转式气波制冷机制冷效率的途径。本文主要工作和研究结论如下：(1)建立了旋转式气波制冷机的实验平台和完善的测最系统。同时采用滑移网格技术建立了与真实情况比较接近的多管、多周期的,能够模拟振荡管与喷嘴渐开渐闭过程的数值模拟模型。在模型中1的振荡管管壁上,通过自定义程序(LDF)，加入实验测得的壁温,避免了振荡管边界条件不准确的问题,节省了模拟计算的时间,克服了累积误差大的缺点。经验证,此模型能够很好的对实验机进行数值模拟。(2)在各种操作条件下,对一端封闭均直振荡管内部波系运动和传热进行了分析和研究。(3)突扩连通结构,能够吸收振荡管中入射激波的能量,将入射激波的反射波变为膨胀波,有利于提高振荡管的制冷效率。突扩连通结构的振荡管等熵制冷效率随射流频率的变化也呈现“马鞍状”,也有极值现象。突扩连通结构的振荡管等熵制冷效率明显的要比一端封闭的均直振荡管制冷效率要高,可提高10%以上。(4)突扩连通结构振荡管直管段与一端封闭均直振荡管壁温分布趋势基本相同。随膨胀比增加,振荡管入口端壁温降低,末端壁温升高。在同样温差条件下,突扩连通结构的表而散热量更多,即突扩连通结构能够向外界环境中散发出更多的热量。从而说明了突扩连通结构具有更好的制冷性能。封闭端突扩连通结构振荡管内的入射激波的运行过程和一端封闭均直振荡管内的入射激波运行过程相同。但两种振荡管内激波扰动范围各不同,封闭端突扩连通结构振荡管的激波扰动范围明显较小。加入连通腔后,内部的压力波振荡幅度明显的减弱。(5)对突扩连通结构振荡管进行强制集中换热,在相同条件下,降低换热器中介质温度,有利于气波制冷机的效率提高。更多还原

【Abstract】 In industry, as a kind of gas expansion refrigeration equipment,Gas Wave Refrigerator(GWR) has good features, such as high throughput, low cost, smooth operation under different conditions easy operation, simple maintenance, long operating life and can be used in gas-liquid two-phase flow. But. it also has some disadvantages, for example, large sized, low utilization rate of oscillating tube,intense vibration. And the investigation indicated that the isentropic refrigeration of the Gas Wave Refrigeration undulate consumingly with the changing of the jet flow frequency, and that is not helpful of the smooth operation. Aiming at these shortcomings, the method of combination of experimental and numerical simulation was adopted by this paper to improve the structure of the oscillating tube which is key components of rotating Gas Wave Refrigerator, and a sudden-expansion structure was proposed. The parameters, such as transient pressure, outer wall temperature, expansion ratio, exit pressure, frequency and inner wave motion, how to affect the refrigeration capability was acquired,realized the operation rules of the GWR.Analyzed and studied the effect of on the refrigeration performance,acquired the operation rules of the GWR. This paper sought the way in which can elevate the isentropic refrigeration efficiency of GWR.The main research and achievements are as following:(1) The reasonable experiment device and measure system were set up to ensure accomplish large of experimental works concerning GWR. Using sliding mesh technique, making a model can complete the multi-period computation and simulate the influence between adjacent oscillating tubes. This model can conquer the shortcoming of old model. There are a number of disadvantages in old model. For example, inaccurate initial conditions and boundary conditions. By solving the problems of long computing time and large accumulated error, this paper adopted the Used Define Function (UDF). UDF can join tube wall temperature distribution which is obtained from experiments in this model. By analyzing the results of experiments and numerical,this model was in good agreement with the experiment.(2) In the kind of operating condition,analyzing and researching the process of the internal flow and heat transfer of one-end-closed oscillating tube.(3) A sudden-expansion structure oscillating tube can absorb the energy of shock wave and become reflected wave into expansion wave. So it is helpful of improving the refrigeration capability. This structure oscillating also presents the "saddle shape’", and also has extremum phenomenon. The isentropic refrigeration efficiency of sudden-expansion structure oscillating is more than one-end-closed oscillating tube and can improve the efficiency to 10% or more.(4) A sudden-expansion structure and one-end-closed structure has the same trend on the wall temperature. With the expansion ratio increases,inlet temperature of oscillating lower, and the end rise.Because in the same condition,a sudden-expansion structure has more superficial heat dissipating capacity,it sends out more quantity of heat. These prove that this structure has greater refrigeration capability.(5) During wave motion,the process of incident shock wave is the same in sudden-expansion structure and one-end-closed structure.But in two kinds of oscillating tubes, the shock wave disturbance scope is respectively different.The scope of sudden-expansion structure is obviously smaller. Add the connectivity chamber, the oscillation amplitude of internal pressure wave obvious weakening.(6) When mandatory centralized heat transfer, reducing heat exchanger medium temperature helps the improvement of refrigeration capability in the same condition.更多还原