1、太陽能制冷用小型噴射器的性能及其優化研究        【中文摘要】隨著能源的不斷消耗,環境污染的不斷加重,全球正面臨著一場能源短缺和生活環境惡化的危機。世界各國對能源的公道有效利用和環境保護也越來越關注。在我國的能源消耗結構中,制冷空調的能源消耗占到了總能耗的20%左右,其制冷劑泄漏也導致了溫室效應及臭氧空洞等環境題目。因此,制冷空調的節能環保就顯得非常的必要,而太陽能噴射式制冷正是這樣一個節能環保的制冷方式。噴射器作為太陽能噴射式制冷的核心部件,有著簡單、穩定可靠的優點;但同時,噴射器內部的活動過程復雜,噴射器

2、理論大多是基于某些特定用途噴射器的性能變化規律的回納總結,設計分析一般都是建立在一維分析基礎上的半經驗公式。對于太陽能制冷用小型噴射器的研究,還少見有報道,其性能變化規律及結構優化的研究就顯得非常有意義。本文在上屆同學的研究基礎上,對實驗臺進行了完善,通過進一步的實驗,并與數值模擬相結合的方法,深進的分析了各運行參數及結構參數對太陽能噴射制冷用小型噴射器的性能的影響,回納總結出了一個新的參數以更加簡便的分析噴射器的性能,優化了噴射器的結構,對進步噴射器效率及完善噴射器理論作出了貢獻,有切實的重要意義。具體的研究工作有:(1)在噴射制冷用噴射器的理論基礎上,建立了一套模擬太陽能噴射制冷用噴射器性

3、能表現的實驗臺。利用蒸汽發生器替換太陽能加熱裝置,產生工作流體。通過調節蒸汽發生器的加熱量、引射進口的閥門和噴射器出口的閥門開度來改變整個實驗系統中工作流體、引射流體和噴射器出口混合流體的工況,研究增壓太陽能噴射制冷用小型噴射器的性能表現。(2)通過分析大量的實驗數據,總結了運行參數對噴射器性能的影響。在不同噴射器結構和運行參數的條件下,具體的分析了工作流體壓力、引射流體壓力、噴射器出口壓力對小型蒸汽噴射器性能的影響規律。同時,引進膨脹比和壓縮比這兩個無量綱參數,分析它們對噴射器性能的影響規律,并通過這兩個無量綱參數分析了工作流體壓力、引射流體壓力和噴射器出口壓力之間的耦合影響。(3)由實驗數

4、據所表現出的規律,回納出了一個組合參數B=(P_c-P_e)P_e/P_p2(k-1)(k為水蒸汽盡熱指數,本文中取1.3),使得固定結構噴射器的噴射系數只與工作流體壓力和無量綱參數B相關,即u=u(P_p,B)。這樣,關于運行參數對噴射器性能影響的分析及運行參數優化的過程可以大大簡化。同時,通過對實驗數據的分析,得出了組合參數對噴射器性能的影響規律。(4)利用實驗的方法分析了噴嘴距和等截面混合段長度這兩個結構參數對噴射器性能的影響規律。根據噴射器結構的可變化情況,不斷改變噴嘴距和等截面混合段長度的尺寸大小,對不同結構下噴射器的性能表現進行了實驗研究。通過實驗研究發現,噴嘴距和等截面混合段長度

5、對噴射器性能的影響很大,且這兩個結構參數都有一個最優的取值。(5)建立了公道可行的蒸汽噴射器數值模擬模型,以進一步對噴射器的性能表現規律進行研究。根據已有的經驗,建立了噴射器的二維軸對稱模型,并結合實驗結果選擇公道的求解方法和求解模型,對噴射器的性能及內部活動現象進行了計算分析。(6)具體分析了噴射器的一些結構對噴射器性能的影響規律。研究中充分利用了商用模擬計算軟件FLUENT及其前處理軟件GAMBIT的靈活性、可重復性和低本錢性等優點,不斷調整噴射器各結構的外形和尺寸,模擬了不同結構下噴射器的性能表現,得到了各部分結構對噴射器性能的影響規律和最優的結構型式。總之,不論是噴射器的運行參數還是結

6、構參數,對其性能均有較大的影響。本文通過實驗的方法,具體的研究了運行參數對噴射器性能的影響規律,并回納總結了新的無量綱參數,減少了影響噴射器性能的運行參數個數,簡化了噴射器性能分析的過程,對噴射器理論的發展有一定的指導意義。同時,對噴射器的結構進行了實驗和模擬相結合的研究,得出了結構參數對噴射器性能的影響規律和最優的結構,對噴射器的結構設計有一定的參考意義。');【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