In this study, the influence of intake-generated swirl and tumble flow on fuel–air mixing and combustion is investigated in a spray-guided stratified-charge direct-injection spark-ignited engine. Previously, it was demonstrated that the introduction of a combined swirl–tumble flow recovered combustion stability, which was otherwise lost when increasing the engine speed from 1000 to 2000 rpm. However, the improved combustion came at the expense of elevated engine-out soot emissions. Here, high-speed combustion luminosity and PIV measurements at 2000 rpm confirm that soot incandescence is more prevalent with high swirl and tumble. The application of high-speed infrared (IR) gasoline-vapor imaging introduced here provides unique insights, revealing that operation with a combination of swirl and tumble generates an asymmetric fuel distribution that spatially correlates with highly luminous sooting combustion. The IR fuel-vapor imaging technique collects line-of-sight mid-infrared thermal emission from the CH stretch band of the heated fuel near a wavelength of 3.4 µm. The IR images resolve the penetrating vapor plumes distinctly, demonstrating that the 3.4 µm band is suitable for quantitative measurements of vapor penetration during injection. After injection, the IR images provide a qualitative description of fuel-vapor spread without combustion. It is found that the no-swirl case has a symmetric fuel-vapor development during the latter part of the compression stroke. In contrast, for operation with strong swirl and tumble, vapor rotation and the development of an asymmetric and non-uniform fuel-vapor distribution is observed. PIV measurements reveal that the swirl flow dominates the vapor rotation, while the tumble flow appears to be a major reason for the asymmetric fuel-vapor distribution.

在这项研究中，研究了在喷雾引导分层充气直喷火花点火发动机中进气产生的涡流和滚流对燃料-空气混合和燃烧的影响。以前，已经证明引入涡流-滚流组合可恢复燃烧稳定性，否则当发动机转速从1000 rpm提高到2000 rpm时，燃烧稳定性会丧失。但是，改善的燃烧是以增加发动机排出的烟尘排放为代价的。在这里，高速燃烧的发光度和2000 rpm的PIV测量结果证实，高涡流和滚落时，烟尘白炽度更为普遍。此处介绍的高速红外（IR）汽油蒸气成像技术的应用提供了独特的见解，揭示了结合涡流和滚流的运行会产生不对称的燃料分布，该分布在空间上与高光度的烟ot燃烧相关。红外燃料蒸气成像技术从C收集视线中红外热辐射加热的燃料的H拉伸带在3.4 µm的波长附近。红外图像清楚地分辨了穿透的蒸气羽流，表明3.4 µm谱带适合定量测量注射过程中的蒸气渗透。喷射后，IR图像定性描述了没有燃烧的燃油蒸气扩散。可以发现，在压缩冲程的后半段，无涡壳产生了对称的燃油蒸气。相反，对于具有强烈旋涡和滚降的运行，观察到蒸汽旋转以及燃料蒸汽分布不对称和不均匀的发展。PIV测量表明，涡旋流主导着蒸汽的旋转，而滚流似乎是造成燃料-蒸汽分布不对称的主要原因。