热表面上附壁燃料液滴蒸发特性实验

Experiments on the evaporation characteristics of sessile fuel droplets on hot surfaces

泄漏或溢出的液体燃料接触到热表面会引起火灾。为减少此类火灾事故,该文研究了燃料液滴在热表面上的蒸发模式和传热机制。利用玻璃恒温加热板模拟热表面实验,研究了乙酸、乙醇、丙酮、乙酸乙酯、正庚烷和环己烷的热蒸发行为。采用红外成像技术和体积估计法分析实验数据,揭示了不同液滴表面的各种热流型和形成机理。乙酸和乙醇液滴表面观察到热流波(hydrothermal waves, HTWs)和Bénard-Marangoni(B-M)流胞;丙酮和乙酸乙酯液滴表面观察到环状热流型;正庚烷液滴表面没有发现明显热流型,而环己烷液滴表面发现了双涡轮热流型。发现分子间氢键的形成和断裂与HTWs和Marangoni流胞的形成有关,液滴的蒸发速率主要由饱和蒸气压决定。实验结果表明:热流型对蒸发速率具有明显促进作用。

[Objective]The primary aim of this research is to address the critical issue of potential fires arising from fuel spillage on hot surfaces.This work is vital owing to the inherent risks associated with such scenarios,particularly in industrial environments where accidental contact between flammable liquids and hot surfaces can lead to disastrous outcomes.A comprehensive understanding of the evaporation patterns and heat transfer mechanisms of fuel droplets on heated surfaces is imperative for mitigating these fire hazards.[Methods] By undertaking this investigation,the goal is to provide valuable insights that can inform safety protocols,design considerations,and risk assessment strategies in various industries dealing with flammable substances.Glass heating substrates serve as the foundation for the investigations,allowing us to simulate real-world scenarios in which fuel droplets come into contact with hot surfaces.To maximize the infrared transmittance of the glass,we increase the transmittance film on the quartz glass to 93%-96%.This study encompasses a range of representative fuels,including acetic acid,ethanol.acetone,ethyl acetate,n-heptane,and cyclohexane,to ensure a comprehensive understanding of the diverse fuel properties.In experimental analysis,we employ state-of-the-art infrared imaging technology in conjunction with a robust volume estimation method.This combination of tools enables us to precisely observe and measure the evaporation behavior of the selected fuel droplets.[Results] This study had yielded innovative and noteworthy results that significantly contributed to the current body of knowledge in this field.Unique thermal patterns on the surfaces of different fuel droplets were observed,providing a detailed understanding of the evaporation process.Hydrothermal waves(HTWs)and Benard-Marangoni(B-M)cells were identified on acetic acid and ethanol droplets,representing a novel finding with implications for the broader understanding of thermal dynamics on liquid surfaces.A particular highlight was the identification of a previously unreported double-vortex thermal pattern on the surface of cyclohexane droplets.This discovery added a layer of complexity to the existing literature,highlighting the complexity and diversity of thermal behaviors in the context of fuel evaporation on heated surfaces.It founded that the contact angle exhibited minimal variation,generally staying within a range of 1o degrees for all six fuels.Consequently,when evaluating the droplet volume using the volume estimation method,it became clear that the liquid was not significantly influenced by changes in the contact angle,and such variations didn't affect the primary results.[Conclusions] In conclusion,this research illuminates the intricate interplay between fuel droplets and hot surfaces,providing crucial insights for fire prevention strategies and safety measures.The observed thermal patterns,including the novel double-vortex pattern,provide a deeper understanding of the underlying mechanisms governing fuel evaporation.This knowledge is instrumental in refining safety protocols,designing effective preventive measures,and informing future research in the broader field of fire safety and risk management.The findings of this investigation underscore the need to consider specific fuel properties and surface characteristics when developing targeted safety strategies for industries dealing with flammable substances.In the future,the goal is to integrate these insights into practical applications,potentially enhancing the safety and resilience of industrial processes involving flammable liquids.