两相流超音速流动、激坡及其应用研究

从两相流体的音速特点出发，研究两相超音速流动，分析超速流动导致的激波状况，并利用两相激波加速凝结和增压的特点，设计了增压换热器。两相流的音速受其压缩性的影响而呈现出与单相流不同的特点，其较小的音突起独两相超音速流动更易实现。两相流激波与前马赫数密切相关，波后汽相凝结、压力升高，利用该特点设计的汽水直接接触式热器，具有高效换热和增压的特点。     

超音速分离管中水蒸气凝结相变的数值研究

基于超音速分离管中混合气体流动属于伴随凝结相变的可压缩、跨音速的特点,建立了考虑传质效应与非平衡凝结过程的数学模型,并采用数值方法对伴随水蒸气凝结的超音速分离管中的流动进行分析研究。以空气、水蒸气及液态水为流动介质,采用两相流动中的VOF模型结合凝结相变模型以及组分传输模型,研究不同进出口参数及不同水蒸气含量对凝结流场的影响。研究结果表明,所建立的分离管内部非平衡凝结相变模型可以较好的再现超音速流中的凝结成核及液滴生长过程;数值计算结果表明,入口压力、温度及水蒸气含量对分离管内流动凝结过程有直接且重要的影响。因此在进行超音速分离管设计时,考虑温度压力参数的同时,考虑水蒸气含量对分离管性能的影响也是非常重要的。     

水蒸气跨音速流动中非平衡现象的数值模拟

研究了水蒸气跨音速流动过程中的非平衡相变及凝结冲波现象,揭示了气动激波与非平衡凝结流动之间相互作用的非定常流动规律。采用欧拉形式的控制方程求解两相凝结流动,建立了二维可压缩守恒型计算模型对水蒸气跨音速非平衡流动进行了数值模拟．捕获到了凝结冲波现象,揭示了凝结冲波的非平衡热力学机理,并探讨了尺度效应对两相非平衡流动的影响。研究了凝结冲波与气动激波之间的不同热力学特性和形成机理,并探讨了气动激波与非平衡凝结流动之间相互作用的非定常流动规律。     

叶栅内凝结激波与气动激波干涉的数值研究

对自发凝结两相流动中凝结激波与气动激波之间的干涉进行了数值研究,气相采用N-S方程,液相凝结过程应用构造的多阶复合参数进行积分求解.模拟得到的数值纹影图显示了不同出口马赫数情况下汽轮机叶栅中过热蒸汽流动和自发凝结流动激波系的分布.结果表明:凝结激波会影响气动激波的强度和出口气流角,消弱气动激波在吸力面反射引起的边界层分离现象,增强尾迹的强度,并影响相关损失的产生.     

关于汽轮机内湿蒸汽两相凝结流动的研究进展

汽轮机内的湿蒸汽非平衡凝结流动会导致机组效率降低和叶片水蚀损坏。由于两相流动远比单相流动复杂,通过实验难以测量其凝结特性。对此,通过分析国内外湿蒸汽两相流理论和实验研究现状,总结了现有的3种研究方法,并指出研究中存在的问题,讨论了两相流凝结机理及其求解方法,阐述了几种湿蒸汽测量方法优点及不足之处。分析指出:凝结相变过程十分复杂,传热传质在微米级水平发生,因此,有必要发展一种考虑两相间耦合的凝结模型。结合两相流数值研究的现状,对汽轮机两相流数值的求解方法进行阐述。湿蒸汽两相流研究为汽轮机通流部分设计和改造提供了理论参考。     

汽与水两相流在热力工程的应用

汽、水两相流体的可压缩性大大超过蒸汽或水的可压缩性，因此汽、水两相流的音速小到5－10米／秒，当汽、水混合物的流速为超音速时遇到的阻力，则产生压力跳跃（激波），因此两相流通过某一装置时，其出口的混合物压力大大超过被引射的流体入口压力，既加热又增加，在热力工程中有很大用途，如热水采暖及热水供应，既不要循环水泵，又不要汽水热交换器，节电又节约燃料，减少基建投资，节省建筑面积，易操作，寿命长，又不结水垢，其噪声与水泵相似，又改善了环境质量。     

喷管内水蒸气凝结相变的数值模拟研究

引入水蒸气真实气体物性,考虑相变、速度滑移等影响因素,建立了超音速水蒸气非平衡凝结流动数值模型,通过与实验数据对比,验证了模型的正确性。随后对喷管内水蒸气超音速流动进行了数值模拟研究,清晰的捕捉到了"X型"凝结激波,并对其形态形成原因进行了分析。通过与理想蒸汽模拟对比,结果表明:水蒸气的非平衡凝结会形成凝结激波现象,导致流场中压力和温度突然升高,速度骤然降低;随后对非平衡凝结现象发生后,液滴半径、液滴数和湿度的增长趋势进行了计算分析。发现在喉部下游0.1 m处,液滴数由0突跃至1014数量级,表明水蒸气发生非平衡凝结,极短时间内产生了大量凝结核,液滴半径和湿度也在短时间内迅速增加。     

考虑两相流音速时气固两相流激波研究

1引言超音速冷喷涂(CSC),又称为冷空气动力学喷涂(CGDS),是一种新型的喷涂表面沉积的方法[1~3]。在超音速冷喷涂中,喷涂粉末与气体混合后,在缩放流道内形成超音速流动,与基板碰撞后喷涂粒子在基板上沉积。由于两相介质是超音速流动,此时气固两相流激波起着至关重要的作用。气固     

湿蒸汽非均质高速凝结流动的数值研究

基于冠状成核机理,建立了湿蒸汽两相非均质凝结流动数值模型,对缩放喷管、汽轮机叶栅和汽轮机级内湿蒸汽两相非均质凝结流动进行了数值模拟．结果表明：与自发凝结相比,非均质凝结流动中杂质颗粒改变了凝结过程;杂质颗粒减小了喷管中凝结激波强度,改变了汽轮机叶栅中的压力分布,降低了蒸汽过冷度,减少了不平衡热力学损失;在汽轮机级内,非均质凝结流动的动、静叶进、出口汽流角接近过热蒸汽流动的动、静叶进、出口汽流角,其动叶前压力高于过热蒸汽的动叶前压力,但级反动度偏离过热蒸汽流动数值．     

汽液喷射器特性研究的进展与现状

介绍了汽液喷射器的特点、实际应用及其性能研究的意义.对影响喷射性能的结构参数和状态参量进行了分析讨论,根据汽液喷射器的实验理论研究整理了一些与喷射性能有关的主要结果.论述了凝结激波产生的机理及对汽液喷射器出口压力提高的作用,在此基础上阐述了升压的原理及特点.针对经验模型在处理汽液喷射器内复杂的两相流动及相变中存在不足,提出利用直接接触凝结理论求解通用两相流控制方程,并对求解的一些关键问题,如采用平均凝结换热系数计算相间质量传递及利用汽羽确定各相体积分数等进行详细论述.     

Effect of Nonequilibrium Homogenous Condensation on Flow Fields in a Supersonic Nozzle

INTRODUCTIONManystudies[1-131onthecondensationshockwaveoccurringinthecaseoftheraPidexPansionofmoistairorsteaminasupersonicnozzlehavebeenper-formed,andthecharacteristicsofcondensationshock'wavehavenearlybeenclarilied.Acondensationshockwavealsooccursinthebladepassageinasteamturbinel14,15]andsuchacondensationshockwavinteractswiththeboundarylayeronthesurfaceoftheblade.Thus,thefiowinthebladepassageofthesteamturbinewiththecondensationshockwavehasnotyetbeenclariliedl16'17].InthepreseDtstudythee…     

Passive Control of Transonic Flow Fields with Shock Wave Using Non—equilibrium Condensation and Porous wall

When non-equilibrium condensation occurs in a supersonic flow field, the flow is affected by the latent heat released. In the present study, in order to control the transonic flow field with shock wave, a condensing flow was produced by an expansion of moist air on a circular bump model and shock waves were occurred in the supersonic parts of the fields. Furthermore, the additional passive technique of shock / boundary layer interaction using the porous wall with a cavity underneath was adopted in this flow field. The effects of these methods on the shock wave characteristics were investigated numerically and experimentally. The result obtained showed that the total pressure loss in the flow fields might be effectively reduced by the suitable combination between non-equilibrium condensation and the position of porous wall.     

Passive Control of Steady Condensation Shock Wave

IntroductionA rapid expansion of moist air or steam in asupersonic nozzle gives rise to nonequilibriumcondensation phenomena. Thereby, the nozzle flow isaffected by the latent heat released by condensation ofwater vapouf, and if the heat released exceeds a certainquantity, a condensation shock wave will occur[1-4].Many works for the passive contfol of shockboundary layer interaction using the porous wall with aplenum underneath have been repofted on the applicationof the technique tO tfansonic…     

Study of the Unsteady Condensation of Moist Air in Shock Tube

The major flow physics of the unsteady condensation in the subsonic flows induced by the unsteady expansion waves in shock tube was studied in this paper. The unsteady condensation phenomenon was analyzed by using the two-dimensional, unsteady, Navier-Stokes equations, which were fully coupled with a droplet growth equation. The third-order TVD MUSCL scheme was applied to solve the governing equation systems. The computational results were compared with the previous experimental data. The time-dependent behavior of unsteady condensation of moist air in shock tube was investigated in details. The results show that the major characteristics of the unsteady condensation phenomenon in shock tube are very different from those in the supersonic wind tunnels.     

Effect of nonequilibrium condensation of moist air on transonic flow fields

luttoductionMany studies on condensation occwhng in the caseof the rapid expansion of moist air mr steam in asupersonic nozzle have been performed experimentallyand numerically, and the characteristics of condensationhave been nearly clchfiedll4]. Schnerr et al.[5] and lriya atal.le] investigated the effect of condensation on thestrength of shock wave on suiface of wing, drag and liftnumerically. However, the. effect of condensation on theshock wave on s~e of wing and talulences behindshock wa…     

Control of transonic flow fields using local occurrence of non-equilibrium condensation

Control of supersonic flow fields with shock wave is important for some industrial fields. There are many studies for control of the supersonic flow fields using active or passive control. When non-equilibrium condensation occurs in a supersonic flow field, the flow is affected by latent heat released. Many studies for the condensation have been conducted and the characteristics have been almost clarified. Further, it was found that non-equilibrium condensation can control the flow field. In these studies, the condensation occurs across the passage of the flow field and it causes the total pressure loss in the flow field. However, local occurrence of non-equilibrium condensation in the flow field may change the characteristics of total pressure loss compared with that by the condensation across the passage of the nozzle and there are few for researches of locally occurred non-equilibrium condensation in supersonic flow field. The purpose in the present study is to clarify the effect of local occurrence of non-equilibrium condensation on the transonic flow field in a nozzle with a circular bump. As a result, local occurrence of non-equilibrium condensation reduced the shock strength and total pressure loss in the transonic flow field by flowing the moist air from trailing edge of the circular bump to the mainstream.     

Passive control of unsteady condensation shock wave

IntroductionIn the case of moist air or steam rapidly expanding ina supersonic nozzle, nollequilibrium condensation occursin the flow field and the flow will be affected by thelatent heat leleased by condensationll-4]. Thereby, if theheat exceeds a certain quantity, the flow will becomeunstable and oscillations of a periodic flow occurs[5-91. Forthe unsteady condensation shock wave, it is blown thatthere are three types of oscillationslg]. These types aredescribed below:1. Mode l: A condensat…     

Visualiztion of Unsteady Gas／Vapor Expansion Flows

INTRODUCTIONReleaseoflatentheataftercondensationofpureva-porsorinvaPor/carriergasmixturesleadstocomplexdynamicalinteractionsoftheflowwiththephasetran-sitionprocess.Infastexpansionflowstheformationoftheliquidphaseisdominatedbyhomogeneouscon-densation.If,asinmanyinternalflowsofwatervapor,thecoolingrateoftheexpansion-dT/dtisoftheor-der1"/ps,heterogeneouscondensationeffectscanbeneglected.TyPicalwatervaporcontentsinthesupplyleadtotransoniccondensationonsetMachnumbers,wheretheflowisnearthemaxi…     

Effect of Axisymmetric Sonic Nozzle Geometry on Characteristics of Supersonic Air Jet

The effect of nozzle geometry on sonic line and characteristics of supersonic air jet was studied. Computational fluid dynamics was applied in this study. The axisymmetric nozzle geometries investigated were two different contour converging nozzles, two different conically converging sharp-edged nozzles and a sharp-edged orifice. The results show that the supersonic jet structure, sonic line and streamlines in supersonic jet are strongly influenced by the nozzle geometry, and the total pressure loss increases with the increase of Mach disk diameter. The present numerical simulation is an effective tool to evaluate compressible flows in supersonic air jet.     

Effect of Non-Equilibrium Condensation of Moist Air on Unsteady Behaviour of Shock Waves around a Circular Arc Blade

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan,compressorblades and butterfly valves,and this often causes serious problems such as the aeroacoustic noise,the vibration.In the transonic or supersonic flow where vapour is contained in the main flow,the rapid expansion of the flowmay give rise to a non-equilibrium condensation.However,the effect of non-equilibrium condensation on thetransonic internal flows around the airfoil has not yet been clarified satisfactorily.In the present study,the effectof non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc bladewas investigated numerically.The results showed that in the case with non-equilibrium condensation,frequenciesof the flow oscillation became smaller than those without the non-equilibrium condensation.