【作者】 刘庆磊；

【导师】 董玉平；

【作者基本信息】 山东大学 ， 机械设计及理论， 2013， 硕士

【摘要】 在生物质焦油、重油催化裂解等具有巨大潜力和广泛应用的能源利用技术研究中,高粘度液体进料喷嘴的研究是一个热点问题,对于焦油等液体燃料而言,喷嘴技术是进料技术的核心,喷嘴性能好坏直接影响反应结果及喷嘴自身的使用寿命,关系到反应过程能否正常稳定运行。多年来关于雾化机理和理论的研究都仅停留在针对某一种物质进行冷态实验得出的半经验公式,未有实质性突破。迫切需要相关雾化机理的研究和相适应雾化进料喷嘴的研发。本文首先对生物质焦油等四种液体进行了粘温特性实验,焦油粘度从12.6mPa·s降低到2.7mPa·s,从中得出了计算方便的四种液体的粘温特性经验公式；在对旋流喷嘴的设计计算方法进行了研究和总结的基础上,结合设计要求和进料喷嘴应满足的性能,根据反应器的结构尺寸和工作条件设计了不同雾化锥角和工作压力下针对生物质焦油的6种不同结构参数的喷嘴。通过在降粘基础上的雾化实验研究发现,粘度降低和压力升高使雾滴的平均粒径变小,而其大小分布范围逐渐变小,液滴尺寸分布变得均匀,焦油粘度对雾化质量的影响可以用昂色格数Z来总结；液滴平均喷射轴向速度随加热温度的升高即液体工质粘度的降低和压力的升高而增加；雾化锥角的实验值全部小于设计值,而且雾化锥角随着压力的升高而逐渐增大,并接近设计值；粘度越大,雾化锥角越小,粘度对雾化锥角的影响并不明显。由实验得到本文工作条件下所设计的最佳结构喷嘴,并实现液滴SMD为35.5μm,满足设计要求。在对喷嘴内部流场的数值模拟研究后发现,液体从喷嘴入口进入旋流腔后速度变大,在进入旋流室后,其速度又逐渐变大直至进入喷孔后速度有所减小,内部流场符合旋涡运动理论,旋流室自由涡区和强制涡区之间存在一个过渡区,但在喷孔处并不存在过渡区；喷孔内径向速度为正值,而旋流室内径向速度为负值,且每个截面上径向速度分布并不均匀；在强制涡内部接近轴心处压力为负值并形成空气锥；越靠近轴心处静压越小,动压与速度的分布状态相似,总压在强制涡区域沿径向分布近似呈二次曲线,在半自由涡区域近似呈对数分布；旋流腔的入口处和喷孔近壁面处湍流动能损耗为主要能量损失来源,液体在旋流室内温度几乎不变,而在喷孔内越接近轴心处温度越低。在实验的基础上对旋流雾化的半经验公式进行了总结分析,提出了SMD预测方程,与实验结果拟合良好,最后在实验数据的基础上得到了以生物质焦油为液体工质的2#和6#喷嘴在设计操作条件下雾化平均液滴直径SMD与温度r之间的拟合方程；本研究实现了高粘液体的雾化,并对解释旋流雾化流场及旋流喷嘴设计的进一步优化、雾化质量的提高提供了理论依据和实验数据。更多还原

【Abstract】 In the field of energy technology research with huge potential and wide application such as catalytic cracking of biomass tar and heavy oil, the feed nozzle for the high viscosity liquid is a hot issue. For tar and other liquid fuel, nozzle is the core of feed technology, the quality of nozzle performance directly affect the reaction results and its own lifespan of nozzle as well as related to the stability of reaction process operation of the project. Atomization mechanism and the atomizing feed nozzles adapted are of urgent need to be researched and developed.Firstly, viscosity-temperature characteristics empirical formula of the four liquid, including biomass tar were obtained through viscosity-temperature characteristic experiment, the viscosity of tar dropped from12.6to2.7mPa·s.6nozzles with different structural parameters, atomizing cone angle and pressure for biomass tar were designed according to the design and performance requirements.Experimental study about swirl nozzle atomization characteristics was carried out to find that reduced viscosity and the increased pressure made average particle size of the droplet become small, and its size distribution range gradually change narrow, the droplet size distribution becomes uniform. The influence of tar viscosity on the quality of atomization can be summarized with cell number Z. The average axial velocity of jet droplet increased with the increase in pressure and decrease in viscosity of the working fluid, all of the experimental values of the spray cone angle were smaller than the design value, and the atomizing cone angle gradually increased as the pressure increased, and tend to close to the design value. The greater the viscosity, the smaller the angle of the spray cone, the influence of viscosity on the spray cone angle is not obvious. It can conclude by experiments that the nozzle6#is with the best structure designed under the conditions of this work, which generated droplets with SMD as small as35.5μm, meeting the requirement.It was found through the numerical simulation of the flow field inside the velocity of the liquid got larger when into the vortex chamber, and its speed gradually got larger in the swirl chamber until into the orifice, where its speed decreased. The internal flow field was in accordance with the swirling motion theory and there is a transition zone between the free vortex region and the forced vortex zone of the swirl chamber, but the transition region did not exist in he injection hole. The radial velocity of the nozzle hole was positive, and that in the swirl chamber was negative, and the radial velocity of each cross-section was not evenly distributed. Air cone was formed close to the axis because of the negative pressure inside the forced vortex. The closer to the axis, the smaller static pressure was, distribution of dynamic pressure was similar to the speed. The distribution of total pressure in the forced vortex region was like a quadratic curve, and logarithmic in semi-free vortex region. Turbulent kinetic energy loss at entrance of the vortex chamber and region near the wall of nozzle was the main energy loss sources. The liquid temperature in the swirl chamber is almost unchanged, while the closer to the axis, the lower temperature was in nozzle hole.Prediction equation for SMD was proposed and it fitted well with the experimental results. Fitting equation for SMD and T of2#and6#nozzle under given operating conditions was obtained on the basis of experimental data. This study accomplished atomization of highly viscous liquid and will provide theoretical basis and experimental data for further optimization of swirl nozzle and improvement of the atomization quality.更多还原