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Experimental study on the droplet characteristics in the spray tip region: comparison between the free and impinging spray
Experimental Thermal and Fluid Science ( IF 2.8 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.expthermflusci.2020.110288
Cheng Zhan , Hongliang Luo , Feixiang Chang , Keiya Nishida , Youichi Ogata , Chenglong Tang , Zehao Feng , Zuohua Huang

Abstract In this work, we compared the microscopic characteristics of the free and impinging spray tip using double-pulse laser particle image analysis technique. Droplet population density, diameters, and velocities were experimentally resolved for both the free and impinging spray at three spray tip penetration positions (STP = 32,37 and 42 mm) under three injection pressures (10, 20 and 30 MPa). Results showed that firstly, wall impingement will delay the arrival timing of the spray tip at a specific spray tip penetration location. The droplets were less populated in the impinging spray compared to the free spray especially at downstream positions. The population density between the impinging and the free spray is more profound at higher injection pressure. Secondly, for fixed injection pressure, more small droplets are observed in upstream region after impingement, while this effect becomes weak at downstream positions. The droplet diameter distribution of the impinging spray is less sensitive to the increase of injection pressure, compared to the free spray. Sauter mean diameter significantly reduces at higher injection pressure for both the free and impinging spray. Finally, the smaller droplet velocity was observed in the impinging spray due to the dissipation of spray momentum during interaction with the wall plate. Based on the droplet size and velocity, gas phase Weber number was further calculated. Compared to the free spray, the Weber number distribution of droplets in the impinging spray concentrates in significantly smaller values at all injection pressures and observation locations.

中文翻译:

喷头区域液滴特性的实验研究:自由喷雾与撞击喷雾的比较

摘要 在这项工作中,我们使用双脉冲激光粒子图像分析技术比较了自由和撞击喷嘴的微观特征。在三种喷射压力(10、20 和 30 MPa)下,在三个喷嘴尖端穿透位置(STP = 32,37 和 42 mm)的自由和撞击喷雾的液滴种群密度、直径和速度通过实验解决。结果表明,首先,壁面撞击会延迟喷嘴到达特定喷嘴穿透位置的时间。与自由喷雾相比,撞击喷雾中的液滴较少,尤其是在下游位置。在更高的注射压力下,撞击和自由喷雾之间的人口密度更大。其次,对于固定注射压力,撞击后在上游区域观察到更多的小液滴,而在下游位置这种影响变弱。与自由喷雾相比,撞击喷雾的液滴直径分布对注射压力的增加不太敏感。对于自由喷雾和撞击喷雾,Sauter 平均直径在较高的注射压力下显着减小。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。而这种影响在下游位置变弱。与自由喷雾相比,撞击喷雾的液滴直径分布对注射压力的增加不太敏感。对于自由喷雾和撞击喷雾,Sauter 平均直径在较高的注射压力下显着减小。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。而这种影响在下游位置变弱。与自由喷雾相比,撞击喷雾的液滴直径分布对注射压力的增加不太敏感。对于自由喷雾和撞击喷雾,Sauter 平均直径在较高的注射压力下显着减小。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。与自由喷雾相比,撞击喷雾的液滴直径分布对注射压力的增加不太敏感。对于自由喷雾和撞击喷雾,Sauter 平均直径在较高的注射压力下显着减小。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。与自由喷雾相比,撞击喷雾的液滴直径分布对注射压力的增加不太敏感。对于自由喷雾和撞击喷雾,Sauter 平均直径在较高的注射压力下显着减小。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。最后,由于在与壁板相互作用期间喷雾动量的耗散,在撞击喷雾中观察到较小的液滴速度。根据液滴尺寸和速度,进一步计算气相韦伯数。与自由喷雾相比,撞击喷雾中液滴的韦伯数分布在所有注射压力和观察位置都集中在显着较小的值。
更新日期:2021-02-01
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