结构参数变化对内混式喷嘴雾化性能的影响作用

通过对比6种结构参数不同的环形内混式喷嘴的雾化平均直径的变化规律,研究了喷嘴结构变化对雾化性能的 影响规律。结果表明,混合腔宽度、内喷嘴缩进长度、出口流程均对喷嘴雾化性能造成明显影响,而不同的混合腔长度、 气体及液体的喷入方式则基本上不影响雾化性能。     

石灰浆液喷嘴雾化特性

石灰浆液雾化喷嘴是烟气喷雾干燥净化系统的关键设备.利用Win212-2型激光粒度分析仪,对外混及内-外混相结合双流体石灰浆液喷嘴的雾化特性进行了试验研究,分析了气液质量比、石灰浆液浓度等参数对雾化粒径分布和雾化角的影响规律.结果表明,气液质量比增大,浆液液滴平均直径减小,但当气液比增大到一定值后,粒径变化趋于平缓;浆液浓度增加,液滴平均直径增加;气液质量比增加,雾化角减小.     

双路离心式喷嘴的实验与数值模拟

通过实验与数值模拟方法开展了双路离心式喷嘴的研究。实验测量了喷嘴主、副油路在不同压力下的雾化锥角与流量特性,拍摄了喷嘴在典型工况下的喷雾场照片。数值模拟采用VOF(Volume-of-Fluid)两相流模型来模拟喷嘴内气液两相流流动,较好地模拟出喷嘴内的空气涡与喷雾锥角,所得到喷雾锥角与实验结果吻合较好。通过实验与数值模拟相结合的方法验证了双路离心式喷嘴的雾化性能,从而为双路离心喷嘴的设计和性能预测提供了理论基础。     

水煤浆外混式气动雾化机理研究

本文从理论角度,通过分析浆-气交界面上Kelvin-Helmholtz不稳定波波幅增长和破碎过程,建立数学模型LFB,对水煤浆外混式气动雾化的机理和液雾特性给出定性及定量的描述;利用Malvern 2600/3600激光粒度仪对外混式双旋流水煤浆气动雾化喷嘴的喷雾进行了测量,初步证实了理论预测的结果以及该理论模型的合理性。     

液体物性对雾化射流液雾粒径的影响

对不同液体在空气中湍动雾化射流的气液两相流场进行了数值模拟.建立了一次雾化的一维模型,分析了粘度、表面张力和气液质量流量比对液雾粒径的影响趋势,采用基于粒子追踪法的二次雾化三维模型,分析了物性和各种工况对液雾粒径沿轴向分布的影响程度.计算结果和已公开发表的实验数据进行比对,得到了较好的吻合,在此基础上,分析了影响气泡雾化喷嘴雾化质量的主要因素.     

旋流多级气动喷嘴设计和喷雾特性研究

本文针对可调加热器用燃烧室的需要，设计了两种新型旋流多级气动雾化喷嘴，并对雾化性能进行了实验研究，探讨了影响喷雾特性的主要因素，评价了喷雾场．研究了最佳喷嘴结构形式，在模拟工况下雾化性能良好，适合小流量燃烧室工作需要，ＳＭＤ接近 ２５ μｍ．     

水煤浆多级气动喷嘴的喷雾特性研究

本文研究了一种多级气动喷嘴对水煤浆燃料的喷雾特性。采用实验的方法研究了水煤浆性质（动态表面张力和表观粘度）、喷嘴操作工况和喷嘴几何结构对射流雾化细度的影响,给出喷嘴雾炬轴向粒度分布,并对相关结果进行了分析。     

高温横流燃气喷雾掺混的数值研究

高温高压条件下受限空间内旋流喷雾与横向气流的掺混规律尚不清楚,本文对圆形通道内高温燃气与旋流喷雾掺混蒸发过程进行了三维数值模拟,探究流场特征与掺混规律,研究增强流场掺混效果的方法。研究结果表明,四喷嘴周向均匀布置可以使雾化液滴群较均匀的充满掺混空间。相邻喷嘴中间区域液滴群浓度较高,气相温降较大。靠近壁面区域出现多组小尺度的旋涡对结构,小尺度涡结构的发展是促进掺混蒸发过程的主要方式。喷嘴雾化锥角、轴向倾角、切向倾角影响雾化液滴滞留时间及喷雾轴向贯穿深度,进而对掺混效果有较大影响,选择适中的喷嘴雾化角及入射角有利于流场掺混均匀。     

空气雾化喷嘴喷雾特性实验研究

基于在低温环境下使用空气雾化喷嘴进行喷雾结冰实验的实际需求,在喷嘴投入使用前,标定了日本雾的池内公司生产的BIMJ 7004型空气雾化喷嘴的喷雾特性,包括各工况下的压缩空气流量、水流量,喷雾锥角和液滴群中值体积直径(MVD),并重点探究了环境温度对MVD的影响。实验结果表明,喷嘴喷雾的MVD受喷嘴气路和水路入口压力的影响最大,且基本不受环境温度的影响,即在0²0℃的环境温度下,喷雾距离D=0.8 m时,喷雾中心线处的液滴蒸发对MVD的影响很小。     

烧原油高效燃烧器的研究

本文讨论了用于油田加热炉的一种烧原油高效燃烧器的设计，论述了Ｙ型蒸汽雾化喷嘴、正交蒸汽雾化喷嘴和高压离心喷嘴的具体设计结果。该燃烧器对原油加温并采用内、外双漩流器组织燃烧，明显提高了燃烧效率。最后还指出了这种燃烧器的开发与应用前景。     

Experimental study of air dilution in oxy-liquid fuel flames

The influence of oxidizer dilution in oxy-liquid ethanol flames is experimentally investigated by using a coaxial air-assisted injector positioned in a vertical combustion chamber. This study accounts for the influence of a two-phase mode since two different injector geometries are used: for the first configuration, a vaporization mode is observed at nominal power in oxy conditions, while for the second one, a brush mode is observed. Dilution with air is applied by keeping oxidizer velocity constant. Flame structure is observed through CH emission: dilution leads to an increase in the flame diameter, and collective effects of two-phase combustion are encouraged. The effect of dilution on oxy flame stability is also studied: for a given oxygen mass fraction in the oxidizer, the oxidizer flow rate is increased until extinction occurs. Dilution leads to a less stable flame, which may be essentially explained by the decrease in laminar flame speed with dilution. For high oxidizer dilution levels, the change in flame structure might be another parameter to consider. Finally, species concentrations are measured using a standard gas sampling technique. NO and CO evolutions with dilution are different between both two-phase combustion regimes. An empirical approach based on thermal NO mechanism and CO oxidation reaction enables one to explain the evolutions for brush mode. For vaporization mode, the residence time in burned gases is also to be considered.     

用于高平均功率FEL的DC-SC光阴极注入器

 为获得用于高平均功率自由电子激光（FEL）的高平均流强电子束，设计了一种新型的DC-SC光阴极注入器。该注入器由皮尔斯直流引出结构、1+1/2超导腔和同轴功率耦合系统组成，可以提供高品质、CW模式或高占空比的电子束。对DC-SC光阴极注入器进行了优化设计和束流动力学研究。模拟和优化结果表明DC-SC光阴极注入器完全可以用于高平均功率自由电子激光。模型腔实验验证了理论模拟的可靠性。     

Design and charge injection characteristics of an electrostatic dielectric liquid pulsed atomizer

An automotive fuel injector has been retrofitted with novel electrostatic components in order to improve the primary atomization and dispersion characteristics of the device. A specific design variant is presented and discussed outlining how a conventional fuel injector may be modified to house electrostatic components. With 2 bar gauge injection pressure and an electrical power of 2 mW, the injector can successfully supply intermittently charged fuel, containing spray specific charge levels up to ～1.4 C/m³. Root mean square (RMS) spray specific charge and RMS total current vs. voltage curves are presented as a function of voltage pulse and solenoid valve frequencies for both low and high flow-rate operation. The fuel injector was able to operate in a stable manner at pulse train frequencies up to 20 Hz and the charge injection mechanism was identical to previous steady voltage and pulsed voltage steady flow systems. An optimal synchronization between the high voltage (HV) pulse frequency and solenoid valve frequency has been determined, allowing for the prevention of electrical breakdown events within the inter-electrode gap over a negative voltage ranging from 0 to 4.5 kV.     

燃油粒度对两相PDE爆震波速的影响

两相爆震燃烧的研究近来取得了较大的进步,但是仍有很多问题需要解决,诸如燃油的喷射、雾化和蒸发,燃油和氧化剂的混合,两相可爆混合物的短距离起爆等等．本文利用激光喷雾粒度分析仪分别就直射喷嘴与气动喷嘴研究了汽油的雾化情况,随着汽油流量的增加,两种喷嘴的雾化变化趋势相反．结合汽油、空气PDE模型机多循环爆震试验,发现汽油的粒度对模型机的爆震波速有较大的影响,粒度减小,波速增大,同时波速具有循环效应．     

Experimental analysis and theoretical lift-off criterion for H2/air flames stabilized on a dual swirl injector

Stabilization mechanisms of partially premixed H₂/air flames on a coaxial dual swirl injector are investigated at atmospheric conditions. Hydrogen is injected through a central duct, and the air by the outer annular channel. Both channels are swirled and two stabilization modes are observed depending on the geometrical configuration of the injector and on the operating conditions. In certain regimes, the H₂/air flame stabilizes on the injector lips as a diffusion flame. For other operating conditions, the flame is lifted from the injector and burns mainly in partially premixed regime leading to limited NOx emissions. PIV measurements in cold flow conditions and direct observations of the flame indicate that the flame stabilization mode is mainly controlled by the inner hydrogen swirl level, the injector recess and the hydrogen velocity. For a given air flowrate, a minimum hydrogen velocity to lift the flame is determined for each combination of inner swirl level and injector recess. Assuming the flame close to the injector lips behaves like an edge flame, a model for flame stabilization based on the triple flame speed and the location of the stoichiometric mixture fraction line is built. According to this model, the flame is anchored to the injector if the triple flame can propagate to the inner injector lips, i.e., if the velocity along the stoichiometric line is lower than the triple flame speed. The model is tested using hydrogen diluted with argon and air diluted with nitrogen. Two cases producing predicted opposite trends are verified. First, the stoichiometric line is moved in the direction of lower velocity zone keeping the triple flame speed constant in order to anchor a lifted flame. Next, the stoichiometric line is kept constant and the triple flame speed is reduced in order to lift an anchored flame. The mechanisms driving flame stabilization are discussed.     

PDA and Neural Network Investigation of Swirl Spray Interaction Phenomena

Experiments are performed to investigate the atomization characteristics of mixed‐interaction regions of sprays of two swirl injectors installed side by side. Both droplet size and velocity distributions on a plane perpendicular to the axes of the injectors are measured using a PDA system. As a result of the interaction phenomenon, a region of secondary atomization is identified that differs significantly from the hollow region spray of a single swirl injector. A neural network algorithm is used to reconstruct the entire spray field for both droplet size and velocity distribution in extrapolation regimes for injector spacing as well as three dimensional spatial coordinates. Excellent agreement between the predicted values and the measurements is obtained. It is observed that points on the extrapolation regime of the neural network can be predicted with an accuracy of 93 % using a training data set with less than 50 % of the number of data points to be predicted. The results indicate the capability of performing design‐ and optimization studies for pressure‐swirl injectors, with sufficient accuracy, by applying a modest amount of data in conjunction with an overall optimized value for the width of the probability.     

用于高平均功率自由电子激光器的DC–RF超导腔注入器

北京大学超导加速器实验室提出了新型DC?RF超导腔注入器的设计方案.该注入器由皮尔斯引出结构、1+1/2超导腔组成,可以提供高品质的、CW模式或高占空比(1%以上)的电子束.对该注入器进行了分析计算和设计研究,通过改变超导腔首腔腔形以增加聚焦效果,采取措施缩短阴极到超导腔的距离,从而有效地抑制束流发射度的增长.用PARMELA对该注入器进行束流动力学研究,以确定皮尔斯引出结构的形状以及超导腔的同步相位.计算结果表明这种用于高平均功率自由电子激光的注入器的设计方案是可行的.     

2MeV注入器绝缘支撑设计与实验

 针对更高能量注入器的技术要求，在现有的2MeV注入器阴阳极头部分别设计出了尼龙材料的分层径向匀场环绝缘支撑结构。实验结果显示，在保证可靠绝缘的基础上，改善了阴阳极间的机械对中性能，提高了束、场、机械三轴的同一性，为2MeV注入器实验平台各项技术指标的提高奠定了基础。     

Numerical simulation and investigation of working process features in high-duty combustion chambers

Basic concepts of a numerical simulation method of two-phase turbulent flows with combustion are stated. Results of computations in gas generators and combustion chambers of liquid-propellant rocket engines operating on oxygen and methane are presented. Features of the processes of evaporation, mixture, flow, and combustion of the propellant within chambers with tree types of injectors, i.e., coaxial-jet gas-liquid, liquid-liquid monopropellant and bipropellant impinging-jets, are studied.