Dynamic Characteristics of the Droplet Impact on the Ultracold Surface under the Engine Cold Start Conditions

IF 1 4区工程技术 Q4 MECHANICS Fluid Dynamics Pub Date : 2024-07-05 DOI:10.1134/s0015462824600068

S. Jin, W. Zhang, Z. Guo, Y. Yuan, Z. Shi, Y. Liu, J. Yan

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Abstract

The impact of liquid droplets on the ultracold surface affects significantly the cold start performance of internal combustion engines but the splash and spreading characteristics after impacting on the ultracold surface are not clearly understood. Therefore, droplets with various physical parameters impacting on the Al–Si alloy surface have been selected for the study under various surface temperatures (–40°C ≤ \(~{{T}_{s}}~\) ≤ 25°C) and droplet impact velocities (0.96 m/s ≤ \(~{{V}_{0}}~\) ≤ 3.52 m/s). The ultracold surface (\({{T}_{s}}\) = –40°C) is beneficial for corona splash, and droplets with the higher Oh number impacting on the ultracold surface easily produce corona splash as the main splash pattern. The ultracold surface assisted in enhancing the stability of the levitated lamella formation, and avoided the effects of rough surfaces, so the upper splash criterion is established to predict the transition from spreading to splash. The decreasing surface temperature reduces the maximum spreading diameter (\({{{{\beta }}}_{{{\text{max}},{\text{lt}}}}}\)) of low solidification point droplets (ethanol, n-propanol, and winter diesel). Based on the assumptions of qualitative temperature, the empirical correlation of the \({{{{\beta }}}_{{{\text{max}},{\text{lt}}}}}\) is created for the T_s from 25 to –40°C.

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发动机冷启动条件下液滴撞击超冷表面的动态特性

摘要液滴撞击超冷表面对内燃机的冷启动性能有很大影响，但液滴撞击超冷表面后的飞溅和扩散特性尚不清楚。因此，我们选择了不同物理参数的液滴在不同表面温度（-40°C ≤ \(~{{T}_{s}}~\) ≤ 25°C）和液滴撞击速度（0.96 m/s ≤ \(~{{V}_{0}}~\) ≤ 3.52 m/s）下撞击铝硅合金表面进行研究。超冷表面（\({{T}_{s}}\) = -40°C）有利于电晕飞溅，欧姆数较高的液滴撞击超冷表面时容易产生电晕飞溅，这是主要的飞溅模式。超冷表面有助于提高悬浮薄片形成的稳定性，避免粗糙表面的影响，因此建立了上飞溅准则来预测从扩散到飞溅的过渡。表面温度的降低减小了低凝固点液滴（乙醇、正丙醇和冬柴油）的最大铺展直径（\({{{{\beta }}}_{{text/{max}},{text{lt}}}}}/）。根据定性温度假设，为 25 至 -40°C 的 Ts 创建了 \({{{{\beta }}}_{{text{max}},{\text{lt}}}}}\) 的经验相关性。

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来源期刊

Fluid Dynamics MECHANICS-PHYSICS, FLUIDS & PLASMAS

CiteScore

1.30

自引率

22.20%

发文量

审稿时长

6-12 weeks

期刊介绍： Fluid Dynamics is an international peer reviewed journal that publishes theoretical, computational, and experimental research on aeromechanics, hydrodynamics, plasma dynamics, underground hydrodynamics, and biomechanics of continuous media. Special attention is given to new trends developing at the leading edge of science, such as theory and application of multi-phase flows, chemically reactive flows, liquid and gas flows in electromagnetic fields, new hydrodynamical methods of increasing oil output, new approaches to the description of turbulent flows, etc.