气泡雾化喷嘴雾化特性实验

利用Malvern2600/3600型激光散射粒度仪对三种不同结构的气泡雾化喷嘴的雾化特性进行了实验研究，并进行了理论分析。实验发现影响喷嘴雾化特性的主要因素有空气注入压力、空气注入截面积、气液质量流量比、出口截面积和液体流量。提高空气注入压力和气液质量流量比、增大空气注入截面积可改善雾化效果，出口截面积和液体流量的增大则降低雾化质量。三种喷嘴中，A型更适合于工业应用。     

气泡雾化喷嘴雾化的特性实验

利用Malvern 2600/3600型激光散射粒度仪对三种不同结构的气泡雾化喷嘴的雾化特性进行了实验研究，并进行了理论分析。实验发现：影响喷嘴雾化特性的主要因素有空气注入压力、空气注入截面积、气液质量流量比、出口截面积和液体流量。提高空气注入压力和气液质量流量比、增大空气注入截面积可改善雾化效果，出口截面积和液体流量的增大则降低雾化质量。三种喷嘴中，A型更适合于工业应用。     

结构及运行参数对内混喷嘴压力的影响研究

在内混式介质雾化喷嘴的设计计算中，通常近似将混合室内压力与雾化介质进口压力之比看作为临界压比，这种近似与实验结果有较大差别。实验研究结果表明，内混式喷嘴混合室内压力并不等于雾化介质进口压力与临界压比之积，而与喷嘴的结构特性及运行参数密切相关。本文以压缩空气和变压器油为工质对内混式介质雾化喷嘴混合室内压力特性进行了实验研究，获得了该类喷嘴混合室内压力与结构及运行参数间的实验关系式（1）、式（2），可供工程设计及运行参考。     

新型气体雾化燃油喷嘴的实验研究

对新型气体辅助雾化喷嘴特性进行了初步实验研究。利用马尔文粒度分析仪测量喷嘴在不同工况下达到的雾化粒度。实验结果表明雾化压力和气液流量比对雾化粒度有明显影响 ,而喷嘴直径几乎对之无影响 ,液体流量测量结果说明喷嘴的流量系数很低。此项研究为燃油喷嘴的开发、设计和运行调节提供了一定的理论依据     

气液两相内混式喷嘴混合室内压力特性的实验研究

在内混式介质雾化喷嘴的设计计算中,有些文献[1]近似将混合室内压力与雾化介质进口压力之比看作为临界压比,这种近似与实验结果有较大差别。研究结果表明,内混式喷嘴混合室内压力并不等于雾化介质进口压力与临界压比之积,而与喷嘴的结构特性及运行参数密切相关。以压缩空气和变压器油为工质对内混式介质雾化喷嘴混合室内压力特性进行了实验研究,获得了该类喷嘴混合室内压力与结构及运行参数间的实验关系式,可供设计使用部门参考。     

_旋转型气_液雾化喷嘴_流量特性的实验研究

在对各种气动喷嘴及其雾化机理分析的基础上提出了一种新型的雾化喷嘴——“旋转型气-液雾化喷嘴”，其气液比在热态实验时为4％～6％(用压缩空气雾化)，并对其流量系数进行了系统的研究。主要考虑了喷嘴的结构参数、气液比(ALR)和液体粘度等因素对流量系数的影响。通过实验测量与拟合，最后得到了喷嘴的流量系数的表达式，可以用来指导喷嘴的设计。     

基于“液包气”雾化的脱硫喷嘴特性实验

在一种内置拉法尔气体喷管两相流“液包气”喷嘴的设计基础上,搭建了多相雾化实验台,进行了喷嘴雾化性能实验,研究了气液质量比（训）对喷嘴雾化颗粒粒径分布均匀性、索特尔平均雾化直径、雾化角等性能指标的影响,推导出“液包气”喷嘴液气压力比和气液质量比的经验公式及适用范围,得到了内置拉法尔喷管两相流“液包气”喷嘴气液质量比的临界点为0．057．结果表明：液气压力比随着硼的增大而减小;当w=0．057时,液气压力比为0．92;气体流量系数与气液质量比呈反比关系;“液包气”喷嘴单相雾化效果远差于两相时的雾化效果,且随着喷嘴液相压力的提高,雾化效果变好,但压力对雾化效果的影响越来越弱．     

气泡雾化喷嘴流量特性的实验研究

两种不同结构形式的气泡雾化喷嘴 ,通过实验对其流量特性和混合室内的流型进行了研究。分析实验现象和实验数据发现 :喷嘴混合室内的流型取决于混合室直径 Dc、气液质量流量比ALR、注气孔截面积 A2 及气压 P2 、液压 P1 等参数 ;喷嘴的流量特性则主要受注气孔截面积 A2 、喷嘴出口截面积 A及运行压力等参数影响 ;流量系数 CD 与参数 X呈线性关系。另外 ,通过理论分析推导出喷嘴临界流量公式 :Ml=μAcaρa ( 1 ALR) ALR,且计算值与实验点符合良好。     

燃油喷嘴气液两相流雾化特性研究

以空气,水为工质,利用马尔文粒度分析仪对气液两相流雾化器喷嘴的雾化特性进行了详细的实验研究。测量了气,液两相流不同入口压力比条件下通过喷嘴后形成的液体雾化粒子的粒径分布,详细讨论分析了气,液两相压力及进气,进液方式对喷雾效果的影响,得出了喷嘴雾化过程中气液两相流量与气液两相压力之间的规律和 化原则,并对喷嘴的雾化机理进行了探讨。     

低压力大流量喷嘴液膜射流破裂长度

对脱硫塔内用低压力大流量喷嘴的液膜破裂长度进行了实验研究，采用影像法考察了速度、喷嘴出口缝隙高度等对液膜长度的影响．结果表明：在无外界强烈扰动情况下，液体流量超过一定值时，其产生的液膜将发生随机性破裂，且液膜外边界变得模糊；通过实验考察了Re数、We数和Oh数对喷嘴液膜射流破裂长度的影响，在此基础上提出了适合脱硫塔中喷嘴的液膜射流破裂长度的关联式．     

Study for the Gas Flow through a Critical Nozzle

In the present study, computational work using the axisymmetric, compressible, Navier-Stokes equations is carried out to predict the discharge coefficient and critical pressure ratio of gas flow through a critical nozzle. The Reynolds number effects are investigated with several nozzles with different throat diameter. Diffuser angle is varied to investigate the effects on the discharge coefficient and critical pressure ratio. The computational results are compared with the previous experimental ones. It is known that the discharge coefficient and critical pressure ratio are given by functions of the Reynolds number and boundary layer integral properties. It is also found that diffuser angle affects the critical pressure ratio.     

选择性催化还原系统防沉积物堵塞喷嘴设计与喷射特性分析

针对选择性催化还原系统产生的沉积物易造成喷嘴堵塞,引起喷嘴管路背压过高及雾化喷射不均匀等问题,设计并研制了一种防沉积物堵塞喷嘴。该喷嘴通过调节喷嘴芯与螺套的锁紧量调定喷嘴的稳定喷射压力,并通过对喷嘴芯的最大开度进行机械限位,有效避免了尿素雾化喷射不均匀及NH 3逃逸等问题。对喷嘴的起闭特性与孔口径向截面的流量特性进行了理论分析,结果表明:当喷嘴因沉积物造成堵塞时,喷嘴芯开度随压力升高而增大,喷嘴孔口径向截面面积及截面质量流量也随之增大,有效提高了喷嘴内部沉积物的排出率,并降低了孔口外部沉积物的凝结风险。采用流体仿真软件Fluent对喷嘴的喷射特性进行了数值模拟,进一步探究了不同喷嘴芯开度及锥度角对喷嘴孔口径向截面面积、截面速度分布及截面流量特性的影响。最后,通过试验验证了喷嘴的喷射效果与开启压力精度。试验结果表明:采用该喷嘴后,喷嘴雾滴分布均匀,雾化效果良好,且在各稳定喷射压力下喷嘴均可以稳定开启,开启压力精度为±5%。     

Experimental study of flow regime characteristics in diesel multi-hole nozzles with different structures and enlarged scales

The internal flow of diesel nozzles has a strong influence on the subsequent spray and atomization characteristics. A flow visualization experiment system equipped with enlarged transparent nozzles was set up to investigate the effect of different nozzle structures and different nozzle enlarged scales on cavitating flow and subsequent spray characteristics. Significant parameters of internal flow including critical pressure of cavitation inception, critical pressure of hydraulic flip, discharge coefficient, Reynolds number, flow rate and cavitation distribution were fully investigated during the experiments. Experimental results show that the nozzles with small length/diameter ratios at the same orifice diameter were more inclined to cavitate and had higher discharge coefficient than that of nozzles with large length/diameter ratios. Cavitating flow in nozzles with different sac volume structures may incur different spray characteristics in the near-nozzle field and it is the internal cavitating flow that induces the asymmetry of subsequent spray. The investigations indicate that the critical pressure of hydraulic flip and discharge coefficient of nozzles under different needle lifts were quite different even under the same boundary conditions and the nozzle flow characteristics have been greatly influenced by the hydraulic flip phenomenon. Two types of cavitation were observed in nozzles with different scaled-up times and the string cavitation was found in three times scaled-up nozzle, while the cloud cavitation bubbles were appeared in five and eight times scaled-up nozzles. A kind of hysteretic cavitation phenomenon was also observed in the experiment and then was analyzed in this paper.     

Characteristics of flame stability and gaseous emission of biocrude-oil/ethanol blends in a pilot-scale spray burner

A burner system with capacity of 30,000 kcal/h was designed for the combustion of biocrude-oil and ethanol blends. An air atomizing spray nozzle with larger fuel orifice was adopted to prevent nozzle clogging, with swirl flow introduced to the combustion air for flame stabilization. Biocrude-oil was prepared from the fast pyrolysis of woody biomass and was blended with ethanol to improve flame stability and ignition characteristics. At various mixing ratios of biocrude-oil and ethanol, flame stability was determined, and gaseous emissions of CO and NO were measured. It was found that stable combustion could be achieved with up to 90 vol% of biocrude-oil. CO emissions of biocrude-oil/ethanol blends were smaller than those of pure ethanol, whereas CO concentration increased significantly in case of pure biocrude-oil due to incomplete combustion. Pollutant NO emission increased slightly with the biocrude-oil mixing ratio. The biocrude-oil burner in this study could provide a design database for industrial burner development.     

A Study of the Gas Flow through Air Jet Loom

Air jet loom,as one of the shuttleless looms,transports a yarn into warps using viscosity and kinetic energy of anair jet.Performance of this picking system depends on the ability of instantaneous inhalation/exhaust,configura-tion of nozzle,operation characteristics of a check valve,etc.In the recent past,many studies have been reportedon the air jet discharged from a nozzle exit,but studies for understanding the flow field characteristics associatedwith shear layer and shock wave/boundary layer interaction in the nozzle were not conducted enough.In this pa-per,a computational study was performed to explain the flow field in the air jet nozzle with an acceleration tubeand validated with previous experimental data available.The results obtained from the computational study showthat,in the supersonic flow regime,the flow field depends significantly on the length of acceleration tube.Asnozzle pressure ratio increases,drag force acting on the string also increases.For a longer acceleration tube,thetotal pressure loss is large,owing to the frictional loss.     

Flow characteristics of hydrogen gas through a critical nozzle

Critical nozzles are widely used in the flow measurement and can be used for mass flow-rate measurement of hydrogen gas. The effect of real gas state equation on discharge coefficient of hydrogen gas flow through a critical nozzle was investigated. The real gas critical flow factor was introduced which considers the effect of the real gas on discharge coefficient. An analytic solution of real gas critical flow factor of hydrogen gas calculated from the modern equations of state based on Helmholtz energy, over a wider range of temperature 150–600 K and pressure up to 100 MPa was presented. An accurate empirical equation for real gas critical flow factor was determined by the nonlinear regression analysis. The equation was in good agreement with the high-pressure hydrogen gas experimental data by Morioka and CFD solutions by Nagao and Kim. Using this equation, the discharge coefficient can be directly and accurately calculated. It indicates that the discharge coefficient of hydrogen gas should be comprehensively taken into consideration with stagnation temperature, stagnation pressure and nozzle throat diameter. A lot of detailed results about the effect of real gas state equation were obtained.     

A Study of Under-expanded Moist Air Jet Impinging on a Flat Plate

When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is under-expanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with non-equilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics are not known satisfactorily. In the present study, the effect of the non-equilibrium condensation on the under-expanded air jet impinging on a vertical flat plate is investigated numerically in the case with non-equilibrium condensation, frequency of oscillation for the flow field becomes larger than that without the non-equilibrium condensation, and amplitudes of static pressure become small compared with those of dry air. Furthermore, the numerical results are compared with experimental ones.