应用于喷雾降尘的喷嘴设计浅析

根据粉尘粒度及雾化效果参数,综合匹配喷嘴结构参数与喷雾压力,设计了旋流片结构的二次雾化喷嘴。     

气—液两相流旋流喷嘴雾化特性研究

液体的有效雾化是当前气液两相流研究中的重要课题,这其中雾化喷嘴的选择能很大程度影响雾化效果。通过查阅大量文献,对不同类型的气液两相流旋流喷嘴的结构、工作原理以及影响雾化效果的各个因素(包括:喷嘴结构、压缩空气压力以及气液比)做出了论述。在实验中采用压缩空气作为雾化介质,利用lyc2000激光粒度仪测量了不同情况下的喷雾特性参数如油雾粒径、油雾浓度等。同时对气液两相流旋流喷嘴雾化特性进行分析,并做了图表分析和曲线拟合。     

某型涡喷发动机回流式喷嘴性能测试与分析

根据回流式喷嘴的工作原理和结构特点,进行燃油喷嘴性能的测试,通过调节工作压力观测燃油雾化状况,并测试喷嘴的雾化角和流量数据。对测试数据进行分析处理,优化调整喷嘴结构参数,使喷嘴的性能参数满足发动机运行的需求,并核定发动机燃油供给系统的工作压力范围。优化的结果能提升涡喷发动机的综合性能,使发动机运行于良好状态。     

组孔式喷嘴雾化与蒸发特性研究

采用KIVA-3软件对收缩型喷孔、平行型喷孔和扩张型喷孔三种组孔式喷嘴在柴油机缸内条件下的雾化与蒸发特性进行了多参数模拟研究。模拟结果表明,与传统喷嘴相比,三种组孔式喷嘴喷雾空间变大,喷雾贯穿距离更长,燃油蒸发量减少,三种组孔式喷嘴燃油蒸发相差很小。组孔喷雾贯穿距离比单喷孔大,主要是由于组孔式喷嘴的油束碰撞从而使得油滴直径增加所致。与平行型组孔喷嘴相比,收缩型和扩张型组孔喷嘴的燃油分布区域更广。发动机缸内初始压力和初始温度对组孔喷嘴蒸发影响不大。     

油雾润滑系统雾化器结构优化设计及性能试验

针对目前油雾润滑系统存在的油雾输送距离短、油雾含量调节困难等问题,对雾化器结构进行优化设计。采用Spey双路离心喷嘴替代目前常用的文丘里管喷嘴,采用PLC原油雾润滑控制系统进行改进;通过试验研究润滑油黏度、温度和空气温度、压力等参数对雾化效果的影响,并确定最佳雾化工艺参数,从而保证了雾化油气中油滴直径分布在1~5μm之间,油雾传送距离达到120 m以上,较好地解决了目前石油化工装置用油雾润滑系统存在的问题。     

两相脉冲爆震发动机的燃油喷射、混合及其雾化研究

两相爆震燃烧近来得到了广泛的重视和关注,但在它走向应用之前仍有很多问题需要解决。燃油的喷射、混合和雾化对两相爆震燃烧的影响就是其中之一。本文利用激光喷雾测量仪分别就直射喷嘴与气动喷嘴研究了汽油的喷射雾化与混合雾化,得到了汽油的雾化粒度与供油量、供气量间的关系。利用CFD程序对混合室中油、气的混合特性进行了模拟,结果与试验结果非常吻合。结合脉冲爆震发动机模型机多循环爆震试验,发现汽油的粒度大小对脉冲爆震模型机的油气当量比、燃油填充比有显著的影响。     

不同喷口扩张比下离心喷嘴雾化特性研究

为研究喷口扩张比对航空发动机离心喷嘴雾化特性的影响,对多种结构离心喷嘴开展试验研究。用工业相机捕捉油雾场形态;用多普勒激光粒度仪测量喷嘴出口液膜速度、雾化粒径;结合数值模拟得到的液膜流动情况,对雾化性能进行详细分析。研究结果表明：随着喷口扩张比的增加,雾化锥角增大,雾化粒径减小,液膜轴向速度减小;当扩张比一定时,不同压差下雾化锥角基本一致;喷嘴下游存在三个流动区域,分别为燃油射流区、射流内侧空气区及射流外侧空气区,射流内侧形成对称的空气涡;在扩张段处液膜与壁面之间会形成分离区,当扩张比较大时,液膜可绕过分离区重新靠近壁面,且扩张比越大,液膜与壁面贴合程度越高。     

气液同轴离心式喷嘴雾化性能及优化设计研究

以气液同轴离心式喷嘴为研究对象,采用了一种优化后的代理模型和多目标优化算法对该喷嘴关键几何结构参数进行优化设计,得到了一个在低压状态下雾化性能更佳的新结构喷嘴.采用计算流体力学(Computational fluid dynamics,CFD)对喷嘴进行流场分析,并用试验验证了CFD数值模拟的准确性.基于改进鲸鱼算法(...     

单进口压力漩流喷嘴雾化半角仿真计算研究

在分析单进口喷嘴与多进口喷嘴内部流场特点的基础上,针对航空发动机单进口喷嘴流场空间上不对称,时间上不稳定的特点,采用空间各点平均和多时间点平均的方法改进雾化半角的计算方法,给出了一种计算单进口小型压力漩流喷嘴雾化半角的数学模型。在判断喷嘴内部流场状态的基础上,采用CFD流体仿真软件计算喷嘴内部流动参数,得到喷嘴出口速度分布,结合改进的雾化半角计算方法,总结喷嘴结构尺寸对雾化半角的影响规律。计算结果表明:雾化半角随出口长度、漩流室长度的增加而减小,随出口外倒角的增加而增加,但是各参数对雾化半角的影响存在不同的特点:当出口长度较小时增加出口长度雾化半角迅速减小,而当出口长度较大时这种减小趋势较缓慢;漩流室长度对雾化半角的影响基本呈线性;出口倒角在10°～20°之间时对雾化半角的影响较大。     

车灯清洗器新型喷嘴的数值研究

由于清洗器喷嘴几何尺寸相对较小,传统的扇形喷嘴结构对车灯的清洗效果不理想。根据车灯清洗要求,研制了一种实现重点清洗和辅助清洗功能相结合的新型喷嘴。并采用数值分析方法对其进行了仿真研究,应用VOF方法对喷嘴内部流场和外部雾化特性方面进行了气液两相流动计算,仿真结果表明新型喷嘴能够获得较大的雾化角,具有较大的轴向和径向动量,提高清洗效果。并与实验结果做了比较,二者吻合较好,为此方法应用到喷嘴设计提供了依据。     

The effect of spray characteristics on the etching of invar alloy with FeCl3 solution

The objective of this study was to investigate the significant characteristics in the sprays of industrial etching nozzles for the sake of process design. The experiment was carried out with different spray pressures and industrial nozzles in the spray etching. Characteristics of the spray, such as the axial velocity and the Sauter mean diameter (SMD), were obtained through the Phase-Doppler Anemometer (PDA). The impact force was calculated through the spray characteristics. It was found that liquid with higher spray pressure resulted in a smaller SMD, higher droplet velocity, and greater impact force. The depth of etching was increased in the case of higher spray pressure. When the spray angle oscillated between 20° and −20°, the effect of etching remained constant. The relationships between the spray characteristics and the etching characteristics were analyzed. The depth of etching had significant, positive correlations with the axial velocity and the impact force. Four liquids of different kinematic viscosities were used to reveal the effects of the kinematic viscosity on the spray characteristics. The results indicated that a lower viscosity of the spray yielded a higher etching rate than a higher viscosity of the liquid. The results clearly show that the characteristics of the spray etching are strongly related to the spray characteristics with the spray conditions.     

Swirl effect on the spray characteristics of a twin-fluid jet

In the liquid fuel combustion chamber, employed fuel must be atomized before being injected into the combustion zone. Therefore, the complete fuel atomization is the most important condition for the combustion efficiency. The atomization quality strongly affects the combustion performance, exhaust pollutant emissions, and flame stability. Therefore, the whole process of spray atomization is of fundamental significance. During past decades many experimental and theoretical studies in this field have been carried out and some improved results have been obtained. Two-phase atomizers, having a variety of advantages such as spray uniformity, appreciable atomization, and smaller SMD with an increase of ambient gas, are considered to be applied in various industrial processes. The purpose of present study is to investigate the mean velocity, turbulence shear stress, turbulence intensity, mean drop size distribution, and droplet data rate in a two-phase swirling jet using PDPA systems.     

离心式喷嘴雾化特性的数值模拟

采用数值模拟的方法,对航空发动机的燃油喷嘴进行研究,模拟不同情况下喷嘴内部的气液两相的流动状况,得到了流量与压力和喷雾锥角的关系,计算结果和试验数据吻合较好,为离心喷嘴的设计和试验提供了可靠的数值计算模型。     

Effect of nozzle geometry for swirl type twin-fluid water mist nozzle on the spray characteristic

Experimental investigations on the atomization characteristics of twin-fluid water mist nozzle were conducted using particle image velocimetry (PIV) system and particle motion analysis system (PMAS). The twin-fluid water mist nozzles with swirlers designed two types of swirl angles such as 0°, 90° and three different size nozzle hole diameters such as 0.5mm, 1mm, 1.5mm were employed. The experiments were carried out by the injection pressure of water and air divided into 1bar, 2bar respectively. The droplet size of the spray was measured using PMAS. The velocity and turbulence intensity were measured using PIV. The velocity, turbulence intensity and SMD distributions of the sprays were measured along the centerline and radial direction. As the experimental results, swirl angle controlled to droplet sizes. It was found that SMD distribution decreases with the increase of swirl angle. The developed twin-fluid water mist nozzle was satisfied to the criteria of NFPA 750, Class 1. It was proven that the developed nozzle under low pressures could be applied to fire protection system.     

Atomization characteristics of intermittent multi-hole diesel spray using time-resolved PDPA data

The intermittent spray characteristics of a multi-hole diesel nozzle with a 2-spring nozzle holder were investigated experimentally. Without changing the total orifice exit area, the hole number of the multi-hole nozzle varied from 3 (d_n=0.42 mm) to 5 (d_n=0.32mm). The time-resolved droplet diameters of the spray including the SMD (Sauter mean diameter) and the AMD (arithmetic mean diameter), injected intermittently from the multi-hole nozzles into still ambient air, were measured by using a 2-D PDPA (phase Doppler particle analyzer). The 5-hole nozzle spray shows the smaller spray cone angle, the decreased SMD distributions and the small difference between the SMD and the AMD, compared with that of the 3-hole nozzle spray. From the SMD distributions with the radial distance, the spray structure can be classified into the three regions : (a) the inner region showing the high SMD distribution; (b) the mixing flow region where the shear flow structure would be constructed; and (c) the outer region formed through the disintegration processes of the spray inner region and composed of fine droplets. Through the SMD distributions along the spray centerline, it reveals that the SMD decreases rapidly after showing the maximum value in the vicinity of the nozzle tip. The SMD remains the constant value near the Z/d_n=166 and 156.3 for the 3-hole and 5-hole nozzles, which illustrate that the disintegration processes of the 5-hole nozzle spray proceed more rapidly than that of the 3-hole nozzle spray.     

A study of the relation between nozzle geometry,internal flow and sprays characteristics in diesel fuel injection systems

This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed : one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.     

An investigation on effect of geometrical parameters on spray cone angle and droplet size distribution of a two-fluid atomizer

A visual study is conducted to determine the effect of geometrical parameters of a two-fluid atomizer on its spray cone angle. The liquid (water) jets exit from six peripheral inclined orifices and are introduced to a high speed gas (air) stream in the gravitational direction. Using a high speed imaging system, the spray cone angle has been determined in constant operational conditions, i.e., Reynolds and Weber numbers for different nozzle geometries. Also, the droplet sizes (Sauter mean diameter) and their distributions have been determined using Malvern Master Sizer x. The investigated geometrical parameters are the liquid jet diameter, liquid port angle and the length of the gas-liquid mixing chamber. The results show that among these parameters, the liquid jet diameter has a significant effect on spray cone angle. In addition, an empirical correlation has been obtained to predict the spray cone angle of the present two-fluid atomizer in terms of nozzle geometries.     

喷射压力对生物柴油混合燃料喷雾特性的影响

基于KH-RT液滴破碎模型对定容燃烧弹内生物柴油-正丁醇混合燃料的喷雾贯穿距离、喷雾锥角、索特平均粒径、速度场以浓度场进行数值模拟,通过定容燃烧弹试验台架获取的生物柴油-正丁醇混合燃料的喷雾特性对数值模型进行验证,结果表明:随着喷射压力的增加,BD70N30混合燃料的喷雾贯穿距和喷雾锥角增加;索特平均粒径降低;雾束中心...     

Characteristics of a liquefied butane spray

The characteristics of a butane spray from pintle-type injector were studied by droplet velocity and diameter measurements and high speed photography. The accumulator type injector operated off a common rail fuel supply system operated at 13 MPa, and was controlled by a high-speed solenoid valve. Injection was carried out in a chamber at ambient temperature and at the pressure above (0.37 MPa) and below (0.15 MPa) the fuel vapor pressure. Two component phase/Doppler particle analyzer and traverser were used to obtain the droplet diameter and the velocity at numerous locations in the spray. The entire injection event was analyzed as a time-average and also subdivided into three temporal intervals. A, B, and C. The high-speed photographs showed a narrower cone angle during the quasi-steady spray period at the 0.37 MPa chamber pressure compared to the 0.15 MPa case.     

A study on the characteristics of soot formation and oxidation in free fuel droplet array

In this study, it was attempted to obtain the fundamental data for the formation and oxidation of soot from a diesel engine. Combustion of spray injected into a cylinder is complex phenomenon having physical and chemical processes, and these processes affect each other. There are many factors in the mechanism of the formation and oxidization of soot and it is necessary to observe spray combustion microscopically. In order to observe with that view, free fuel droplet array was used as an experimental object and the droplet array was injected into an atmospheric combustion chamber with high temperature. Ambient temperature of the combustion chamber, interdroplet spacing, and droplet diameter were selected as parameters, which affect the formation and oxidation of soot. In this study, it was found that the parameters also affect ignition delay of droplet. The ambient temperature especially affected the ignition delay of droplet as well as the flame temperature after self-ignition. As the interdroplet spacing that means the local equivalence ratio in a combustion chamber was narrow, formation of soot was increased. As diameter of droplet was large, surface area of the droplet was also broad, and hence evaporation of the droplet was more active than that of a droplet with relative small diameter.