大液气质量流量比双通道气流式喷嘴雾化滴径

在气流式雾化过程的有限随机分裂模型基础上,结合液滴分裂时间和液滴运动规律,分析了大液气质量流量比同轴双通道气流式喷嘴的雾化过程,得到了Sauter平均直径（SMD）的一般表达式.实验结果表明,得到的SMD的关系式的形式是合理的,通过实验确定相关模型参数后,可以用来预测大液气质量流量比条件下同轴双通道气流式喷嘴的雾化性能.     

气流式雾化过程的有限随机分裂模型

滴径分布是描述喷嘴雾化性能的一个重要指标.从液滴分裂的自相似性出发,提出了描述气流式雾化过程的液滴有限随机分裂模型.实验和模拟计算结果表明,该模型能较好地模拟三通道喷嘴气流式雾化过程的平均滴径和滴径分布的非线性关系.     

压力旋流喷嘴雾化滴径分布的模型预测和实验

利用激光片光荧光诱导技术（PLIF）测得不同液体流量下的压力旋流喷嘴雾化滴径分布,用平均粒径约束的三参数最大熵模型对雾化滴径分布进行预测。将理论预测分布与实验结果进行拟合,得到广义伽玛参数α随着液体流量变化的一般表达式。用拟合模型对粒径分布的特点和规律进行总结,结果表明：拟合模型能很好地预测粒径的数量分布,且不受小液滴的影响;随着液体流量的增加,液滴粒径分布范围逐渐变窄,峰值液滴粒径呈线性减小趋势,峰值液滴百分数呈线性增加趋势。     

转炉一次除尘新OG系统高效喷淋塔喷嘴雾化特性的模拟

利用离散相模型对转炉一次除尘新OG系统高效喷淋塔内喷嘴的雾化特性进行模拟,分析了喷射角度、喷射压力、喷射流量及喷嘴水平间距等因素对雾化场索太尔平均直径(SMD)和蒸发效率的影响. 结果表明,在一定范围内随喷射角度增加,液滴在雾化场中的覆盖面增大,液滴驻留时间变长,蒸发效率增加,雾化场SMD减小,喷射角度大于60o时,SMD值减小缓慢. 随喷射压力增大,液滴蒸发效率增加,雾化场SMD减小,压力大于1.0 MPa时对SMD的影响较小. 随喷射流量增加,液滴蒸发效率减小,雾化场SMD增加,流量小于0.15 kg/s时,SMD增加幅度偏小. 两喷嘴水平间距越大,液滴分布面积越大,但对雾化场SMD影响较小. 在一定条件下,喷嘴间距约为800 mm时,截面速度分布较均匀.     

空气雾化喷嘴的液滴雾化性能实验研究

采用LSA-Ⅲ型激光粒度仪对一种常用的小流量空气雾化喷嘴的液滴雾化性能进行实验研究。实验主要测定了不同气液比、气相压力和液相压力情况下沿喷雾轴向不同位置处的液滴粒径分布。测定结果表明气液比和气相压力对雾化液滴粒径影响均较大,其中气相压力影响最大,气液比其次,液相压力影响最小。在本实验测定条件下,经过喷嘴雾化后在轴向100、200、300、400和500 mm位置处液滴的表面积平均直径（SMD）和体积平均直径（D43）出现波动性变化。通过对实验测得液滴粒径分布数据的分析,可以得到Rosin-Rammler分布函数中的特征参数和n,为定量计算液滴粒径提供理论基础。     

双通道气流式喷嘴雾化特性实验研究

以清水和空气为实验介质,对同轴双通道气流式喷嘴雾化特性进行了实验研究,分析了喷淋量对雾化角及径向流通量分布的影响,分别考察了气速和喷嘴轴向位置对液滴索特平均直径(SMD)的影响。研究结果表明,喷嘴径向流通量分布随着雾化气量的升高而趋于集中,当气体流量高于1500 L/min时,雾化角随着气量升高而降低;喷口处气速与喷嘴轴向位置均是影响液滴SMD与粒径分布的重要因素,液滴SMD随着气速增大逐渐减小,当气速超过150 m/s时其下降趋势变缓,粒径分布均匀度显著提高;随着喷嘴轴向距离增大液滴SMD逐渐减小,当距离大于300 mm时其变化不再显著,但粒径分布均匀度显著提高。     

内混式扇形喷嘴雾化特性及液滴直径拟合的研究

对一种新型的内混式空气雾化喷嘴进行了测量和研究,其目的是探索新型内混式喷嘴在添加空气助力下增强混合改善雾化质量的应用性能。试验采用4组不同几何结构参数的内混式空气雾化扇形喷嘴,通过马尔文激光粒度分析仪测量不同气压、不同水流量等工况参数下雾化液滴索特平均直径(SMD)D32和雾化角等雾化性能参数,对试验结果作对比分析,并拟合了喷嘴液滴直径的准则关系式。分析试验结果,得出空气助力可以明显改善液滴雾化质量的结论。     

采用高压静电雾化法制备W/O乳化液的实验研究

采用静电雾化方法进行了W/O玉米油乳化液制备的实验研究,在雾化流量2.8~15 mL/min、电极施加电压5.2~11 kV的条件下,用Winner99颗粒图像测试仪测试了所制乳化液的离散相滴径,分析了施加电压及雾化流量对平均滴径及滴径分布的影响. 结果表明,静电雾化法可制备离散相滴径比搅拌法更均匀的乳化液,离散液滴平均滴径约为28 mm且绝大多数液滴直径为20~40 mm,其稳定性明显优于搅拌法所制乳化液. 乳化液离散相滴径与施加电压及雾化流量密切相关,电压增大、雾化电流增大,乳化液离散相滴径急剧减小,滴径分布变窄. 流量增大,单位时间内液滴携带及输运的电量增大,故雾化电流增大;但液滴荷积比随流量增大而减小,故滴径变大,滴径分布变宽. 高电压、低流量有助于获得稳定性更好的乳化液.     

大容量蒸汽雾化油喷嘴的结构特点及冷态试验

简述了大容量蒸汽雾化油喷嘴的结构特点,对大容量蒸汽雾化喷嘴的雾化特性和流量特性进行了试验研究.特别是通过激光全息摄影,得到了T型喷嘴和Y型喷嘴的雾化场液滴尺寸的数量级,为喷嘴设计提供了依据.     

三通道气流式喷嘴内粘性流体雾化过程

研究了粘性流体在三通道气流式喷嘴的雾化过程,考察了三通道喷嘴雾化性能的影响因素。实验及数值模拟结果表明,当其他条件不变时,雾化滴径随液体粘度的约0.088次方单调增大,随液体流量的约0.37次方单调增大,随一、三通道气量比α的增加,呈现先增后减的非单调变化趋势,在α≈0.22时Sauter平均直径SMD达到最大值。     

Influence of Atomizing Parameters on Droplet Properties in a Pulse Combustion Spray Dryer

A pulse combustor employed in a spray-drying system offers a new approach for liquid atomization that yields high-quality powders at low cost. Using a pulse combustion atomizer, there is no need for any form of nozzle dispersion and its atomization mechanism differs from those of conventional atomizers, such as rotary atomizers and pressure and pneumatic nozzles. In this work, based on the analysis of atomization mechanism, experiments of unsteady pulsating atomization were carried out in an experimental system of a Helmholtz-type pulse combustor. An optical analyzer was used for measuring the mean diameter of atomized droplet and droplet distribution. The effects of liquid feed rate, air flow oscillatory frequency, and liquid viscosity on atomized droplet size and size distribution were investigated and analyzed. The results indicate that the uniform droplet size distribution can be obtained under the conditions of a low feed rate, high-frequency pulsating flow, and moderate viscosity. The range of the droplets' Sauter mean diameter (SMD) is between 50 and 80 µm. The pulsating air flow from the pulse combustor can be used to atomize liquid or slurry without a nozzle and the atomizing quality can meet the requirements of spray drying.     

Influence of Atomizing Parameters on Droplet Properties in a Pulse Combustion Spray Dryer

A pulse combustor employed in a spray-drying system offers a new approach for liquid atomization that yields high-quality powders at low cost. Using a pulse combustion atomizer, there is no need for any form of nozzle dispersion and its atomization mechanism differs from those of conventional atomizers, such as rotary atomizers and pressure and pneumatic nozzles. In this work, based on the analysis of atomization mechanism, experiments of unsteady pulsating atomization were carried out in an experimental system of a Helmholtz-type pulse combustor. An optical analyzer was used for measuring the mean diameter of atomized droplet and droplet distribution. The effects of liquid feed rate, air flow oscillatory frequency, and liquid viscosity on atomized droplet size and size distribution were investigated and analyzed. The results indicate that the uniform droplet size distribution can be obtained under the conditions of a low feed rate, high-frequency pulsating flow, and moderate viscosity. The range of the droplets' Sauter mean diameter (SMD) is between 50 and 80 µm. The pulsating air flow from the pulse combustor can be used to atomize liquid or slurry without a nozzle and the atomizing quality can meet the requirements of spray drying.     

Prediction of droplet size distribution in sprays of prefilming air-blast atomizers

Droplet size distribution is a crucial parameter of atomization process besides droplet mean diameter. In this paper, the finite stochastic breakup model (FSBM) of prefilming air-blast atomization process has been proposed according to the self-similarity of droplet breakup. There are four parameters in FSBM, which are the initial droplet diameter D₀, the maximum stable droplet size D_c, the minimum mass ratio of a sub-droplet to the mother droplet a, and the droplet breakup probability P(D). The simulation results of droplet size distribution with this model agreed well with the experimental results of prefilming air-blast atomizers. With this model, the nonlinear relationship between the mean droplet diameters and droplet size distribution of the air-blast atomization process can be predicted exactly.     

Predictive models for characterizing the atomization process in pyrolysis of methyl ricinoleate

Pyrolysis of methyl ricinoleate(MR) can produce undecylenic acid methyl ester and heptanal which are important chemicals. Atomization feeding favors the heat exchange in the pyrolysis process and hence increases the product yield. Herein, predictive models to characterize the atomization process were developed. The effect of spray distance on Sauter mean diameter(SMD) of atomized MR droplets was examined, with the optimal spray distance to be 40–50 mm. Temperature mainly affected the physical properties of feedstock, with smaller droplet size obtained at increasing temperature. In addition, pressure had significant influence on SMD and higher pressure resulted in smaller atomized droplets. Then, a model for SMD prediction, combining temperature, pressure, spray distance, and structural parameters of nozzle, was developed through dimensionless analysis. The results showed that SMD was a power function of Reynolds number(Re), Ohnesorge number(Oh), and the ratio of spray distance to diameter of swirl chamber in the nozzle(H/dsc), with the exponents of -1.6618,-1.3205 and 0.1038, respectively. The experimental measured SMD was in good agreement with the calculated values, with the error within ±15%. Moreover, the droplet size distribution was studied by establishing the relationship between the standard deviation of droplet size and SMD. This study could provide reference to the regulation and optimization of the atomization process in MR pyrolysis.     

同轴四通道喷嘴气流式雾化特性影响因素研究

提出一种新型同轴四通道喷嘴——由内到外采用气-液-气-液设置,最外环液体可以将合成气和氧气隔离,大幅降低喷嘴出口温度,可望延长气化炉中喷嘴使用寿命。为研究喷嘴雾化效果的影响因素,以水和空气为介质,利用马尔文激光粒度分析仪对同轴四通道喷嘴的气流式雾化液滴索特平均直径进行实验研究。发现对雾化效果影响程度从大到小依次为通道三、通道四、通道二和通道一;增大通道二、四液量分配比可以降低雾化粒径;增大外环液膜厚度会增大雾化粒径;通道一、三气量分配比对雾化颗粒的影响是非单调性的,雾化粒径先增大后减小。基于实验结果进行数值分析,拟合获得了同轴四通道喷嘴雾化液滴粒径关系式。     

HAN基液体推进剂喷雾场液滴尺寸分布的简化模型

为了建立HAN基液体推进剂喷雾场液滴尺寸分布的简化模型,基于最大熵原理,在质量守恒与概率和为定值的约束条件下,用拉格朗日因子法则推导了液滴尺寸分布函数,将该函数应用于HAN基液体推进剂模拟工质喷雾场液滴尺寸的预估;采用相位多普勒粒子动态分析仪(PDA)测量了HAN基液体推进剂模拟工质在1.8~2.6MPa喷射压力下对撞式喷嘴雾化液滴尺寸分布;通过最小二乘法优化Nukiyama-Tanasawa分布函数式中的q值对数目微分分布进行了修正,拟合得到q值与喷射压力p之间的函数关系为q(p)=-0.344p2+1.525p+1.268。结果表明,计算得出的液滴尺寸数目微分分布与HAN基液体推进剂喷雾场实测数据变化趋势相符,表明建立的液滴尺寸分布模型是合理的。     

旋流压力式喷嘴低压喷淋液滴粒径的实验研究

以自来水为喷淋介质,对旋流压力式喷嘴低压喷淋液滴粒径进行了测试,分析了压力、喷孔直径和喷嘴流量对液滴索特平均直径(d_(SMD))的影响规律,研究了旋流压力式喷嘴液滴尺寸的分布规律。采用跨径(K)和均匀度指数(N)来揭示喷嘴低压喷淋质量。实验结果表明,d_(SMD)较大,超过250μm；d_(SMD)随喷孔直径增大而增大,随压力和喷嘴流量增大而减小；喷淋液滴尺寸分布均匀性较好,K小于0．65,N大于4。实验结果可以为旋流压力式喷嘴设计和改进提供重要的实验依据。