INFLUENCE OF LADDER TYPE ACCELERATING SECTION ON ATOMIZATION CHARACTERISTICS OF PRESSURE SWIRL ATOMIZER
LiuZhaomiao1,*,, WangKaifeng1, WangZhilin1, ZhengHuilong2, ZhangTan2, KangZhenya2 1 College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology, Beijing 100124, China2 Key Laboratory of Science and Technology on Precision Manufacturing Technology, Beijing Precision Engineering Institute for Aircraft Industry Aviation, AVIC, Beijing 100076, China 文献标识码:A
关键词:旋流式喷嘴;阶梯型加速段;索特尔平均直径;雾滴速度;喷雾锥角 Abstract Swirl atomizer inner core is the most important swirling component of the pressure swirling atomizer, the geometric topology of the swirl atomizer inner core directly affects the spray characteristics of pressure swirling atomizer.The current smooth acceleration section of the swirl atomizer inner core has lower flow efficiency.In order to reduce the energy loss, the swirl atomizer core accelerating section with ladder type has been designed to make spray medium pre-swirl and enhance the swirl strength in this paper, the lower part rotates 15° relative to the upper part, and the direction of the rotation is the same as the direction of the swirling slots of the atomizer. Spray flow rate, spray Sauter mean diameter(SMD), spray cone angle and droplet velocity were experimentally investigated by making use of particle dynamics analysis system(PDA) and charge coupled device experimental system(CCD) before and after the structure improvement of the acceleration section, and the axial and radial distributions of SMD and droplet velocity were also analyzed. Under the pressure ranges from 0.08 MPa to 0.46 MPa, the ladder type acceleration section has the better pre-swirl effect. The flow characteristics of the atomizer were increased by 48% to 51.8%; the axial and radial velocity of the spray were increased by 31.4% to 32.8% and 1.6% to 16.8%, respectively.The spray cone angle was reduced by 4.21° to 6.57°, and the SMD at downstream of the spray was decreased by 9.2% under higher pressure conditions.Compared with the smooth accelerating section, the application of ladder type accelerating section is beneficial to improve the quality of atomization.
Keywords:pressure swirl atomizer;ladder type accelerating section;Sauter mean diameter;spray droplet velocity;spray cone angle -->0 PDF (13190KB)元数据多维度评价相关文章收藏文章 本文引用格式导出EndNoteRisBibtex收藏本文--> 刘赵淼, 王凯峰, 王治林, 郑会龙, 张谭, 康振亚. 阶梯型加速段对旋流喷嘴雾化特性的影响[J]. 力学学报, 2018, 50(3): 570-578 https://doi.org/10.6052/0459-1879-18-006 LiuZhaomiao, WangKaifeng, WangZhilin, ZhengHuilong, ZhangTan, KangZhenya. INFLUENCE OF LADDER TYPE ACCELERATING SECTION ON ATOMIZATION CHARACTERISTICS OF PRESSURE SWIRL ATOMIZER[J]. Chinese Journal of Theoretical and Applied Mechanics, 2018, 50(3): 570-578 https://doi.org/10.6052/0459-1879-18-006
实验喷嘴结构及其喷雾介质流动过程如图2和图3所示, 喷嘴由进液段、加速段、旋流段、收缩段组成.喷雾介质由进液段进入喷嘴, 在加速段受流通面积减小作用完成初始加速, 经旋流段获得足够的周向速度后注入收缩段形成稳定旋流, 最终从喷嘴出口喷出.实验采用水做喷雾介质, 出口为环境大气. 显示原图|下载原图ZIP|生成PPT 图3实验喷嘴喷雾介质流向示意图 -->Fig.3Flow direction of spray medium of experimental atomizer -->
为研究喷嘴A和喷嘴B雾滴速度的径向分布规律, 选取捕获粒子数5000以上测量点进行分析, 径向分布测量截面距喷嘴出口距离分别为20, 40, 60, 80 mm. 喷嘴A和喷嘴B雾滴轴向速度的径向分布关系曲线如图6所示.与文献[27?29]的研究结果相同, 雾滴在靠近喷嘴出口处具有较大的初始速度, 在距离喷嘴出口较近的20 mm 截面上轴向速度具有比较明显的双峰分布特征, 径向分布在距离轴线20 mm 至25 mm区域内.在距离喷嘴出口20 mm 至60 mm 范围内, 随着喷雾的展开, 雾滴轴向速度逐渐转变为三峰分布, 径向分布范围增大至40 mm 至45 mm区域内, 雾锥边缘的喷雾介质与周围空气摩擦作用加强, 雾滴动能急剧减小, 雾滴轴向速度峰值快速衰减近50%并远离雾场轴线;雾锥轴线附近区域由于径向和切向速度分量较小, 雾滴轴向速度衰减不明显, 虽轴向距离的增加逐渐形成新的峰值.在距离喷嘴出口60 mm 至80 mm 范围内, 由于雾滴速度的减小, 空气对雾滴的阻力减小, 雾滴速度仅小幅衰减, 分布曲线较为平滑, 分布范围增长不明显. 喷嘴A和喷嘴B雾滴径向速度的径向分布关系曲线如图7所示.与轴向速度相比, 各测量点雾滴的径向速度数值较小, 正反向峰值位置与轴向速度的峰值位置基本一致. 测量截面距离喷嘴喷口从20 mm增加到80 mm, 径向速度正反向峰值受环境空气摩擦衰减60%左右, 峰值位置逐渐远离雾场轴线. 显示原图|下载原图ZIP|生成PPT 图6轴向速度径向分布曲线 -->Fig.6Axial speed distribution in radial direction under same dorsal pressure difference -->
背压差0.32 MPa时, 喷嘴A达到额定压力, 与相同压力条件下喷嘴B相比, 轴向速度峰值减小19.3%至22.9%, 20 mm截面径向速度增大44.7%,80 mm截面径向速度增大7.7%; 径向分布范围更广.喷嘴A 和喷嘴B的轴向速度在距离出口20 mm截面上均有较明显的双峰分布特征, 在距离出口40 mm截面上喷嘴A轴向速度的双峰分布特征消失, 喷嘴B轴向速度依然为双峰分布.背压差0.46 MPa时, 喷嘴B达到额定压力, 雾场雾滴轴向速度的最大值与最小值分别比喷嘴A 增大32.8%与31.4%, 20 mm截面径向速度增大1.6%, 80 mm截面径向速度增大16.8%;雾场径向分布范围与喷嘴A 相比较小, 轴向速度在距离出口20 mm和40 mm截面上有较为明显的双峰分布特征.离心作用使喷雾发散成空心锥形, 在喷雾中轴线及附近区域形成负压区, 负压区抽吸小粒径雾滴进入此区域并使雾滴向喷嘴出口处回流, 部分液滴因回流产生负向速度, 使轴线及附近位置的测量点平均速度较低, 因此在喷雾的回流区域喷雾轴向速度会呈现双峰分布.相比于喷嘴A, 喷嘴B的阶梯型加速段除使喷雾介质获得初始加速外还起了导流作用, 喷雾介质以与旋流槽旋向相同的流向注入旋流槽, 提升了旋流的强度, 使雾滴的径向速度衰减放缓, 旋流作用距离加长. 背压差为0.46 MPa时, 喷嘴B径向速度更大且衰减较慢, 轴向速度的双峰效应保持至距离喷嘴出口40 mm 截面, 对雾滴的抽吸作用更明显, 回流区面积更大. 显示原图|下载原图ZIP|生成PPT 图7径向速度径向分布曲线 -->Fig.7Radial speed distribution in radial direction under same dorsal pressure difference -->
为研究喷嘴A和喷嘴B喷雾SMD的径向分布规律, 选取捕获粒子数5000以上测量点进行分析, 径向分布测量截面距喷嘴出口距离分别为20, 40, 60, 80 mm. 由图10可知, 不同截面上, SMD的径向分布均为双峰分布;测量截面距离喷嘴出口20 mm 时, SMD峰值距离喷雾轴线10 mm 至15 mm, 测量截面距离喷嘴出口增大到80 mm时, SMD峰值距离喷雾轴线增大至45 mm;随截面轴向距离增大, 喷雾SMD峰值逐渐远离雾场轴线.分布特点与文献[33]的研究结果基本一致. 显示原图|下载原图ZIP|生成PPT 图10SMD径向分布曲线图 -->Fig.10SMD distribution in radial direction under same dorsal pressure difference -->
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