| 离轴全息成像测量三维气动旋流低温雾化场 |
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| 引用本文： | 宋阁,赵越,汪磊,刘涛,吴迎春,林文辉,吴学成.离轴全息成像测量三维气动旋流低温雾化场[J].实验流体力学,2022,36(2):21-29. |
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| 作者姓名： | 宋阁 赵越 汪磊 刘涛 吴迎春 林文辉 吴学成 |
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| 作者单位： | 1.中国航发湖南动力机械研究所，株洲 412002 |
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| 基金项目： | 国家自然科学基金（52006193）；国家科技重大专项（2017-V-0016-0069，J2019-III-0006-0049）；国家重点研发计划（2020YFA0405700，2020YFB0606200） |
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| 摘 要： | 为研究低油温工况下气动旋流雾化喷嘴近场雾化特性，建立了25 kHz皮秒脉冲激光离轴全息系统，对1 kPa气压、0.03 MPa油压和–40～28 ℃油温工况下喷嘴下游30 mm内近场雾化过程进行了三维可视化测试。实验获取了包含非球形液滴的近喷嘴雾化场清晰图像，记录了液膜袋状破碎与液丝分解等典型雾化动态过程。通过颗粒识别与定位，获取了雾化场中尺寸30～1500 μm的液滴粒径及三维位置，统计得到雾化场索特平均直径（SMD）的三维分布信息。研究发现:在气压1 kPa、油压0.03 MPa工况下，液滴粒径主要分布在200 μm以内，其中30～40 μm粒径占比最高，均在15%以上；三维粒径分布表现为雾锥中央粒径较大，边缘区域粒径较小；油温降低对雾化效果恶化显著，使雾锥体积缩小、雾化液滴密度降低且均匀性下降；油温从28 ℃降至–20 ℃时，下游截面中心粒径从300 μm左右增大至450 μm以上，局部大于650 μm；–40 ℃时，喷嘴下游出现大型液柱与多枝状液膜、液丝结构，燃油分解破碎距离进一步延长。实验结果证实了高速离轴全息技术在低油温工况下喷嘴近场雾化特性三维可视化诊断中的可行性，获取的雾化场三维参数可为喷嘴结构设计优化及雾化模型研究提供数据参考。
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| 关 键 词： | 离轴数字全息 旋流雾化 粒径 三维 低温 |
| 收稿时间： | 2021-10-25 |
Measurement of 3D airblast swirl atomization field at low temperature with off-axis holography |
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| Affiliation: | 1.AECC Hunan Aviation Powerplant Research Institute, Zhuzhou 412002, China2.State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China |
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| Abstract: | A 25 kHz picosecond pulsed digital off-axis holography system is applied to measure the near-nozzle atomization characteristics of an airblast swirl atomizer under low oil temperature conditions. Experiments are carried out for the near-nozzle atomization process 30 mm down-stream from the nozzle exit under air pressure of 1 kPa and oil pressure of 0.03 MPa. The oil temperature varies from –40 ℃ to 28 ℃. It is found that the atomization field in the near-nozzle region contains non-spherical droplets. Typical dynamic processes of atomization such as the breakup of films and filaments are visualized with clear images. The sizes and three-dimensional（3D） positions of droplets ranging from 30 to 1500 μm are obtained through particle identifica-tion and locating, thereafter statistics on 3D distribution of Sauter Mean Diameters（SMD） is obtained. It is found that under conditions of oil pressure of 0.03 MPa and air pressure of 1 kPa, the droplet diameter is mainly distributed within 200 μm, and droplets with size range 30–40 μm account for the largest proportion, above 15%. The 3D droplet size distribution is expressed as a cone where the central droplet size is larger than that on the edge; the decrease of oil temperature significantly deteriorates the atomization effect, which reduces the volume of the spray cone, and the density and the uniformity of atomized droplets; With oil temperature decreasing from 28 ℃ to –20 ℃, the central droplet diameter of the downstream cross-section increases from about 300 μm to over 450 μm and can be locally larger than 650 μm; with the oil temperature of –40 ℃, a large liquid core with multi-branched liquid films and filaments appears downstream of the nozzle, resulting in a longer breakup distance. The experimental results also demonstrate that the high-speed digital off-axis holography is a powerful tool for three-dimensional visualization and diagnostics of near-nozzle atomization under low oil temperatures conditions. This work can provide reference data for optimization of the nozzle structure design and the demonstration of the atomization model. |
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