本文關(guān)鍵詞：離心泵作液力透平的能量轉(zhuǎn)換特性及葉輪優(yōu)化研究　出處：《蘭州理工大學(xué)》2016年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 離心泵作液力透平 能量轉(zhuǎn)換 遺傳算法 神經(jīng)網(wǎng)絡(luò) 優(yōu)化

【摘要】：在石油化工、煤化工、海水淡化等許多流程工業(yè)中,存在有大量的高壓液體,高效回收利用這部分液體壓力能具有重要的現(xiàn)實(shí)意義和經(jīng)濟(jì)價(jià)值。液力透平是回收利用液體壓力能的一種裝置,其中泵反轉(zhuǎn)作液力透平是目前廣泛應(yīng)用的機(jī)型。從有關(guān)文獻(xiàn)及生產(chǎn)實(shí)際中發(fā)現(xiàn),目前泵反轉(zhuǎn)作液力透平普遍存在能量轉(zhuǎn)換效率不高的問題,這與泵用作液力透平時其內(nèi)部能量轉(zhuǎn)換特性認(rèn)識不足有較大關(guān)系。為此,論文以離心泵反轉(zhuǎn)作液力透平為研究對象,采用數(shù)值計(jì)算與實(shí)驗(yàn)相結(jié)合的方法對液力透平外特性進(jìn)行了研究,通過實(shí)驗(yàn)結(jié)果驗(yàn)證了本文數(shù)值計(jì)算策略的準(zhǔn)確性;采用數(shù)值計(jì)算的方法研究了液力透平葉輪及蝸殼內(nèi)的能量轉(zhuǎn)換特性,為后續(xù)優(yōu)化設(shè)計(jì)提供參考依據(jù);建立了基于代理模型和智能優(yōu)化算法的液力透平優(yōu)化系統(tǒng);在上述的基礎(chǔ)上對液力透平葉輪進(jìn)行了優(yōu)化研究。本文的主要研究內(nèi)容分為以下3部分:1.空離心泵作液力透平的內(nèi)部能量轉(zhuǎn)換特性研究基于CFD技術(shù),通過對液力透平葉輪不同徑向位置流體所具有的能量、各區(qū)域輸入的凈能量、各區(qū)域傳遞給葉輪的能量、能量損失及蝸殼不同截面位置流體所具有能量、各區(qū)域能量損失等能量特征的分析,對液力透平葉輪和蝸殼內(nèi)流體能量的傳遞與變化過程進(jìn)行了研究。結(jié)果表明:對于葉輪,流體對葉輪做功主要表現(xiàn)為壓力做功,做功的關(guān)鍵區(qū)域在葉輪的中前部,葉輪葉片后部區(qū)域在小流量工況對葉輪做功相對較少,而在大流量工況不僅對葉輪不做功,而且還消耗葉輪的機(jī)械能;葉輪整體能量轉(zhuǎn)換效率不高。對于蝸殼,蝸型段內(nèi)靜壓能沿流向基本呈線性減小的趨勢,而動壓能則沿流向呈現(xiàn)出波動現(xiàn)象;蝸殼收縮管段內(nèi)靜壓能和動壓能沿流向的變化均比較規(guī)律;蝸殼中能量損失主要在喉部之后的下游區(qū)域。2.空離心泵作液力透平葉輪優(yōu)化系統(tǒng)的建立通過研究液力透平內(nèi)部能量轉(zhuǎn)換特性,為液力透平的優(yōu)化設(shè)計(jì)提供了參考依據(jù),但在優(yōu)化設(shè)計(jì)時還需確立具體的優(yōu)化設(shè)計(jì)方法。本文對液力透平葉輪幾何參數(shù)進(jìn)行優(yōu)化時,其目標(biāo)函數(shù)是由液力透平的水力性能參數(shù)構(gòu)成,而液力透平葉輪幾何參數(shù)與其水力性能間的隱式關(guān)系極其復(fù)雜,因此采用傳統(tǒng)的優(yōu)化方法很難實(shí)現(xiàn),然而智能優(yōu)化算法中的遺傳算法是通過模仿自然界的選擇與遺傳機(jī)理來尋求目標(biāo)函數(shù)最優(yōu)解的方法,能有效地以概率的形式進(jìn)行全局尋優(yōu),且對所求優(yōu)化問題沒有過多的數(shù)學(xué)要求,因此,本文選用遺傳算法對液力透平的幾何參數(shù)進(jìn)行優(yōu)化。但在尋優(yōu)過程中,液力透平水力性能的CFD數(shù)值計(jì)算無疑是非常耗時的,因此本文還引入了非線性映射能力較強(qiáng)的GA-BP神經(jīng)網(wǎng)絡(luò)代替在尋優(yōu)過程中獲取液力透平性能參數(shù)的CFD數(shù)值計(jì)算,這樣便形成了一種以GA-BP(Genetic Algorithm-Back Propagation)神經(jīng)網(wǎng)絡(luò)與遺傳算法相結(jié)合的優(yōu)化設(shè)計(jì)方法。最后,將優(yōu)化過程中涉及到的各種技術(shù)通過程序控制,建立起本文的優(yōu)化系統(tǒng)。3.離心泵作液力透平的葉輪優(yōu)化設(shè)計(jì)通過對離心泵用作液力透平時葉輪軸面流動特點(diǎn)的分析,發(fā)現(xiàn)液力透平葉輪流道面積變化規(guī)律與其內(nèi)部流動規(guī)律匹配性較差。針對于此,采用本文建立的優(yōu)化系統(tǒng)對葉輪軸面投影圖進(jìn)行了優(yōu)化設(shè)計(jì)。優(yōu)化時以控制葉輪軸面形狀的1?、2?、1R、2R和3R為設(shè)計(jì)變量,以液力透平在最優(yōu)工況下的水力效率為目標(biāo)函數(shù),壓頭為性能約束條件進(jìn)行優(yōu)化,優(yōu)化后液力透平性能較之前得到較大的改善。通過對離心泵反轉(zhuǎn)作液力透平時葉輪內(nèi)能量轉(zhuǎn)換特性的分析,發(fā)現(xiàn)葉輪能量轉(zhuǎn)換效率不高。在離心泵用作液力透平的葉輪內(nèi),能量轉(zhuǎn)換的核心是葉片,因此離心泵用作液力透平的葉片有待優(yōu)化改進(jìn)。鑒于此,采用已建立的優(yōu)化系統(tǒng)對該模型的葉片型線進(jìn)行了優(yōu)化設(shè)計(jì)。優(yōu)化時采用三次非均勻B樣條曲線參數(shù)化葉片型線,以控制葉片形狀的控制點(diǎn)參數(shù)為設(shè)計(jì)變量,液力透平在最優(yōu)工況附近三個工況點(diǎn)的水力效率為目標(biāo)函數(shù),三個工況點(diǎn)下的壓頭為約束條件對葉片型線進(jìn)行優(yōu)化,優(yōu)化后液力透平的效率在指定的三個工況下分別得到了較大的提升,同時滿足初始設(shè)定的壓頭約束,說明優(yōu)化后葉片能量轉(zhuǎn)換能力增強(qiáng),同時表明采用該優(yōu)化方法對液力透平葉片型線優(yōu)化的可行性。通過對優(yōu)化后液力透平葉輪的內(nèi)流場分析,發(fā)現(xiàn)葉輪流道內(nèi)仍存在較大的漩渦區(qū)域,采用增加葉片數(shù)的方法來進(jìn)一步改善液力透平葉輪的性能。研究發(fā)現(xiàn):葉輪葉片數(shù)的適當(dāng)增加可以改善葉輪的內(nèi)部流場,增強(qiáng)葉輪的做功能力,有利于液力透平效率的提升,但葉片數(shù)過多的增加,在葉輪出口產(chǎn)生較為嚴(yán)重的葉片排擠現(xiàn)象,同時,流體與葉片接觸的總表面積會增大,導(dǎo)致流體與葉片表面的摩擦損失增大,反而不利于葉輪性能的提升。針對液力透平葉輪葉片增加過多時在葉片出口處造成嚴(yán)重排擠以及壁面摩擦損失增大的問題,可以采用添加分流葉片的方法來進(jìn)一步解決。
[Abstract]:In many petrochemical industries, such as petrochemical industry, coal chemical industry, seawater desalination and so on, there are lots of high-pressure liquids. It is of great practical significance and economic value to recycle and utilize this part of liquid pressure efficiently. The hydraulic turbine is a device for the recovery and utilization of the pressure energy of the liquid, in which the pump is reversed as a hydraulic turbine, which is widely used at present. From related literatures and production practice, it is found that pump inverting hydraulic turbine generally has low energy conversion efficiency, which is related to insufficient understanding of the internal energy conversion characteristics of pump when used as hydraulic turbine. Therefore, the centrifugal pump reversal for hydraulic turbine as the research object, using the method of numerical simulation and experiment of combining the characteristics of hydraulic turbine are studied, the experimental results verify the accuracy of the numerical calculation method; studied by numerical simulation method of hydraulic turbine impeller and volute energy conversion characteristics, provide a reference the basis for the subsequent optimization design; a hydraulic turbine optimization system and intelligent agent model based on optimization algorithm; optimization study of the hydraulic turbine impeller on the basis of the above. The main content of this paper is divided into the following 3 parts: the study of the internal energy conversion characteristics of hydraulic turbine for 1. air centrifugal pump based on CFD technology, based on hydraulic turbine impeller at different radial positions of fluid energy, regional input, regional net energy transferred to the impeller energy, energy loss and different volute section position the fluid has energy, the regional energy loss characteristics of energy analysis of fluid energy hydraulic turbine impeller and volute transfer was studied and the process of change. The results show that: for the impeller, the impeller fluid pressure work mainly for work in key areas of work in front of the impeller, the impeller blades of the rear area in the small flow condition of impeller is relatively small, and in the large flow condition not only on the impeller does not work, but also consume the mechanical energy of the impeller impeller; the overall energy conversion efficiency is not high. For the volute, worm in static pressure along the flow direction can basically showed a trend of linear decrease, while showing a wave phenomenon and moving along the direction of pressure pipe; the volute systolic pressure energy and dynamic pressure variation along the flow direction are law; energy loss in the downstream area in the main volute throat after. The establishment of optimization system for 2. air centrifugal pump as a hydraulic turbine impeller provides a reference for optimizing design of hydraulic turbine by studying the internal energy conversion characteristics of hydraulic turbine, but in the optimization design, we need to establish a specific optimization design method. The hydraulic turbine impeller geometry parameters were optimized in this paper, the objective function is composed of the hydraulic performance parameters of hydraulic turbine, hydraulic turbine impeller and the implicit relationship between the geometric parameters and the hydraulic performance is extremely complex, so the use of traditional optimization methods is very difficult to achieve, but intelligent genetic algorithm optimization algorithm is to seek a method the optimal solution of the objective function through the imitation of a natural selection and genetic mechanism, can effectively in the form of probability for the global optimization, and to solve the optimization problem does not require too much, so the geometric parameters of mathematics, genetic algorithm to optimize the hydraulic turbine. But in the process of optimization, numerical calculation of hydraulic turbine hydraulic performance of the CFD is very time-consuming, CFD numerical calculation this paper also introduces the GA-BP neural network strong nonlinear mapping ability instead of hydraulic turbine performance parameters obtained in the optimization process, thus forming a GA-BP (Genetic Algorithm-Back Propagation) optimization the design method of combining neural network and genetic algorithm. Finally, various technologies involved in the optimization process are controlled through program, and the optimization system of this paper is established. 3., the impeller optimization design of centrifugal pump as a hydraulic turbine. Through the analysis of the flow characteristics of the impeller on the axial surface of the centrifugal pump as a hydraulic penetration, it is found that the variation rule of the flow path area of the hydraulic turbine impeller has poor matching with its internal flow rule. In view of this, the optimization system of the axial plane of the impeller is optimized by the optimization system established in this paper. In optimization, we take 1, 2, 1R, 2R and 3R as the design variables to control the impeller shaft surface. The hydraulic efficiency of the hydraulic turbine is optimized under the optimal working condition as the objective function, and the pressure head is optimized by performance constraints. After optimization, the performance of the hydraulic turbine has been greatly improved. Through the analysis of the energy conversion characteristics in the impeller of the centrifugal pump, it is found that the energy conversion efficiency of the impeller is not high. As the centrifugal pump is used as the impeller of the hydraulic turbine, the core of the energy conversion is the blade, so the centrifugal pump is used as the blade of the hydraulic turbine to be improved. In view of this, the optimized design of the blade profile of the model has been carried out with the established optimization system. The three non uniform B spline curve parameters of blade profile optimization, in order to control the blade shape parameters as design variables, the hydraulic efficiency of hydraulic turbine in three operation points near optimal conditions for target function, optimize the head three operating point under the constraint conditions of the blade type line. After optimizing the efficiency of hydraulic turbine in three specified working conditions were improved obviously, while satisfying the constraint set initial pressure head, that leaves the energy conversion ability after optimization, also shows that the optimization method is feasible in hydraulic turbine blade profile optimization. Through the analysis of the flow field of the optimized hydraulic turbine impeller, it is found that there are still larger vortices in the impeller passage, and the number of blades is added to further improve the performance of the hydraulic turbine impeller. It is found that the proper increase of impeller blades can improve the impeller's internal flow field and enhance the impeller's work capacity, which is conducive to the improvement of hydraulic turbine efficiency, but the number of blades is increased.
【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TH311

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