Characteristics of Early Flame Development in a Direct-Injection Spark-Ignition CNG Engine Fitted with a Variable Swirl Control Valve

A similarly accessed engine is also reported elsewhere [6,17]. [...]a camera endoscope of type AVL KARL STORZ M00060 30° (KARL STORZ, Mittelstr. 8, 78532 Tuttlingen, Deutschland) was attached to the imaging device, inserted into the cylinder, and steered 30° to image the vertical in-cylinder plane view on the CCD camera, as shown in Figure 1 and Figure 2. A rise in engine speed can increase the in-cylinder turbulence intensity, which promotes the degree of flame wrinkledness [11]. [...]the wrinkle level of the early flames shown in Figure 7 could be the result of the tradeoff between the mixture leanness and the level of turbulence created due to engine speed variations. The intake flow structures of the different induction cases shown in Figure 10 revealed the formation of large and strong swirling cores in the medium- and high-swirl inductions, which led to a lower rate of breakdown of the large-scale flow structures during the compression stroke. [...]large-scale flow structures dominated the flow at the time of ignition near the spark plug, which resulted in a higher flame distortion. x- and y-directions in Figure 10 represent the distance from the center of the cylinder. [...]of ignition, the flow near the spark center was dominated by small-scale eddies that had a lower capacity for distorting the early flame. 3.3.