太阳能制冷用小型喷射器的性能及其优化研究

1、太阳能制冷用小型喷射器的性能及其优化研究        【中文摘要】随着能源的不断消耗,环境污染的不断加重,全球正面临着一场能源短缺和生活环境恶化的危机。世界各国对能源的公道有效利用和环境保护也越来越关注。在我国的能源消耗结构中,制冷空调的能源消耗占到了总能耗的20%左右,其制冷剂泄漏也导致了温室效应及臭氧空洞等环境题目。因此,制冷空调的节能环保就显得非常的必要,而太阳能喷射式制冷正是这样一个节能环保的制冷方式。喷射器作为太阳能喷射式制冷的核心部件,有着简单、稳定可靠的优点;但同时,喷射器内部的活动过程复杂,喷射器

2、理论大多是基于某些特定用途喷射器的性能变化规律的回纳总结,设计分析一般都是建立在一维分析基础上的半经验公式。对于太阳能制冷用小型喷射器的研究,还少见有报道,其性能变化规律及结构优化的研究就显得非常有意义。本文在上届同学的研究基础上,对实验台进行了完善,通过进一步的实验,并与数值模拟相结合的方法,深进的分析了各运行参数及结构参数对太阳能喷射制冷用小型喷射器的性能的影响,回纳总结出了一个新的参数以更加简便的分析喷射器的性能,优化了喷射器的结构,对进步喷射器效率及完善喷射器理论作出了贡献,有切实的重要意义。具体的研究工作有:(1)在喷射制冷用喷射器的理论基础上,建立了一套模拟太阳能喷射制冷用喷射器性

3、能表现的实验台。利用蒸汽发生器替换太阳能加热装置,产生工作流体。通过调节蒸汽发生器的加热量、引射进口的阀门和喷射器出口的阀门开度来改变整个实验系统中工作流体、引射流体和喷射器出口混合流体的工况,研究增压太阳能喷射制冷用小型喷射器的性能表现。(2)通过分析大量的实验数据,总结了运行参数对喷射器性能的影响。在不同喷射器结构和运行参数的条件下,具体的分析了工作流体压力、引射流体压力、喷射器出口压力对小型蒸汽喷射器性能的影响规律。同时,引进膨胀比和压缩比这两个无量纲参数,分析它们对喷射器性能的影响规律,并通过这两个无量纲参数分析了工作流体压力、引射流体压力和喷射器出口压力之间的耦合影响。(3)由实验数

4、据所表现出的规律,回纳出了一个组合参数B=(P_c-P_e)P_e/P_p2(k-1)(k为水蒸汽尽热指数,本文中取1.3),使得固定结构喷射器的喷射系数只与工作流体压力和无量纲参数B相关,即u=u(P_p,B)。这样,关于运行参数对喷射器性能影响的分析及运行参数优化的过程可以大大简化。同时,通过对实验数据的分析,得出了组合参数对喷射器性能的影响规律。(4)利用实验的方法分析了喷嘴距和等截面混合段长度这两个结构参数对喷射器性能的影响规律。根据喷射器结构的可变化情况,不断改变喷嘴距和等截面混合段长度的尺寸大小,对不同结构下喷射器的性能表现进行了实验研究。通过实验研究发现,喷嘴距和等截面混合段长度

5、对喷射器性能的影响很大,且这两个结构参数都有一个最优的取值。(5)建立了公道可行的蒸汽喷射器数值模拟模型,以进一步对喷射器的性能表现规律进行研究。根据已有的经验,建立了喷射器的二维轴对称模型,并结合实验结果选择公道的求解方法和求解模型,对喷射器的性能及内部活动现象进行了计算分析。(6)具体分析了喷射器的一些结构对喷射器性能的影响规律。研究中充分利用了商用模拟计算软件FLUENT及其前处理软件GAMBIT的灵活性、可重复性和低本钱性等优点,不断调整喷射器各结构的外形和尺寸,模拟了不同结构下喷射器的性能表现,得到了各部分结构对喷射器性能的影响规律和最优的结构型式。总之,不论是喷射器的运行参数还是结

6、构参数,对其性能均有较大的影响。本文通过实验的方法,具体的研究了运行参数对喷射器性能的影响规律,并回纳总结了新的无量纲参数,减少了影响喷射器性能的运行参数个数,简化了喷射器性能分析的过程,对喷射器理论的发展有一定的指导意义。同时,对喷射器的结构进行了实验和模拟相结合的研究,得出了结构参数对喷射器性能的影响规律和最优的结构,对喷射器的结构设计有一定的参考意义。');【Abstract】 With the unceasing energy consumption and increasing environment pollution, the world is facing a cris

7、is of energy shortage and environment deterioration.The rational and efficient energy using and environment protection are getting more and more concern in each country.In our country's energy consumption structure,the proportion of refrigeration and air-conditioning is about 20%,and the refrige

8、rant leak has led to the green house effect,ozone layer hole and other environmental problems. Therefore,it is very necessary to conserve the energy and protect the environment of refrigeration and air-conditioning.And solar jet refrigeration has that function.There are many advantages on ejector as

9、 the core component of the solar jet refrigeration, for example:*,stable and reliable.However,the inside flow of the ejector is complex;most of the ejector theories are only a sum-up which are based on the performance disciplinarian of some certain ejectors;the design and evaluation of an ejector us

10、ually are based on 1-D analysis until now.And the study of small-scale ejector of solar jet refrigeration is rare at the same time.Therefore,it is the very significant for the study of performance disciplinarian and structure optimization of the small-scale ejector.In this *,many relations between e

11、jector performance and operating parameters or ejector structures are mastered,a new parameter is summarized to analyze the ejector performance *r,and the ejector structure is optimized through analyzing the experiment and simulation results.The main work and results of this * are given as follows:(

12、1) set up an experiment system which is used to simulate the performance of ejector of solar jet refrigeration based on the ejector theory,and the performances of small-scale ejector of solar compression-enhanced jet refrigeration have been studied through changing the operating parameters and eject

13、or structures.(2) Sum up the relationships between the ejector performances and operating parameters according to the analysis of a mass of experiment data,the operating parameters include motive fluid pressure,the suction fluid pressure,the discharging fluid pressure,expansion ratio and compression

14、 ratio.And analyze the coupling influence among the motive fluid pressure,the suction fluid pressure and the discharging fluid pressure through the two dimensionless parameters-expansion ratio and compression ratio.(3) Sum up a combination parameter B=(P_c-P_e)P_e/P_p2(k-1) (k=1.3,is the adiabatic i

15、ndex of vapor),thus the entrainment ratio of fixed structure ejector only rely on the motive fluid pressure and combination parameter,viz.u-u (P_p,B).At the same time,relationship between the ejector performance and combination parameter is also found through the analysis of experiment data.(4) Anal

16、yze the relationship between the ejector performance and structure-nozzle space, length of unchangeable mix-section-by the use of experiment method,which shows that the nozzle space and length of unchangeable mix-section have a great impact on ejector performance,and that the two structure parameter

17、s have optimization size.(5) Select a turbulence model which is suitable for ejector numerical simulation for further study of ejector performance,and analyze the ejector performance and internal supersonic flow by solving the 2-D axial symmetrical model of ejector.(6) Analyze the relations between

18、the ejector performance and some structure parameters in detail. And find the optimization structure by tentative simulation of different shape and size of ejector taking advantages of the flexibility,easy repetition,and low cost of numerical simulation.In a word,both operating parameters and structure parameters of ejector have great impacts on ejector performance.In this *,a detailed study of the relationship between