Experimental and theoretical investigation of transient fluid dynamic phenomena in the vicinity of automotive fuel injectors

了解导致液体燃料雾化和蒸发的机制是设计高效清洁燃烧系统的关键一步。绝大多数燃料喷雾研究都集中在稳态雾化过程上，并基于液滴是完美球形的假设，即使这种喷雾可能包含大部分的韧带和变形液滴。在微观尺度上缺乏关于瞬态雾化和混合过程（即在喷射开始和结束期间）的信息抑制了精确的发动机模拟工具的开发和验证。例如，在燃料喷射结束之后，存在于喷射器的喷嘴内的残余燃料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存在几个问题。过量的燃料由于其体积大、移动缓慢且通常与表面结合的性质而可能经历不完全燃烧。这不仅对排放和性能有负面影响，而且不完全燃烧的副产物被认为与燃料喷射器尖端上的碳质沉积物的生长有关。已知这些沉积物的积累会导致燃料喷射器过早失效，这会导致功率输出和发动机寿命的降低。随着现代多次喷射策略引起瞬态喷射阶段数量的增加，后喷射排放对于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