Dynamics of gasoline fuel direct injections

了解导致液体燃料雾化和蒸发的机理是设计高效和清洁燃烧系统的关键一步。绝大多数燃油喷雾研究的重点是稳态雾化过程，并基于液滴是完美球形的假设，尽管这种喷雾可能包含很大比例的韧带和变形的液滴。在微观尺度上缺乏关于瞬时雾化和混合过程(即在喷射开始和结束期间)的信息，阻碍了精确发动机模拟工具的开发和验证。例如，燃油喷射结束后，喷油器喷嘴内的残余燃油通过惯性和毛细作用排出。这些不受控制的燃料排放事件可能会带来几个问题。过量的燃料由于其体积大、移动缓慢且通常局限于表面的性质而可能发生不完全燃烧。这不仅对排放和性能有负面影响，而且不完全燃烧的副产品被认为与喷油器尖端碳质沉积的增长有关。众所周知，这些沉积物的积累会导致喷油器过早故障，从而导致功率输出和发动机寿命的减少。随着现代多重喷射策略带来越来越多的瞬时喷射阶段，喷射后排放对现代发动机来说越来越成问题。

Understanding the mechanisms that lead to the atomisation and evaporation of liquid fuels is a key step towards the design of efficient and clean combustion systems. The vast majority of fuel spray research is focused on steady-state atomisation processes and based on the assumption that droplets are perfectly spherical, even though such sprays can contain a large proportion of ligaments and deformed droplets. The lack of information about transient atomisation and mixing processes (i.e. during start and end of injection) at the microscopic scale inhibits the development and validation of accurate engine simulation tools. For example, after the end of fuel injection, residual fuel present inside the injector's nozzle is discharged through inertia and capillarity. These uncontrolled fuel discharge events can present several problems. The excess fuel can undergo incomplete combustion due to its large, slow moving and often surface-bound nature. Not only does this have a negative effect on emissions and performance, but the by-products of incomplete combustion are thought to be implicated in the growth of carbonaceous deposits on the tips of fuel injectors. Accumulation of these deposits is known to lead to premature fuel injector failure that can lead to reductions in power output and engine lifetime. With modern multiple-injection strategies giving rise to an increased number of transient injection phases, post-injection discharges are increasingly problematic for modern engines