An Experimental Investigation Into Characteristics Of Tumble Flow In A Four-Valve Gasoline Engine

In the internal combustion(IC) engine, the air flow determined by the intakeports in the cylinder directly affects the combustion characteristics, thereby affectingthe engine power, economy and emissions. It is an efficient and widely used methodto develop IC engine that evaluating the ports by the flow parameters such as tumbleratio, swirl ratio,flow coefficient and acquired by the steady flow test rig. Nowadays,there are several evaluation method of steady flow including Ricardo, FEV, AVL andSwRI methods, but not a full and fair standard, especially for the tumble test andevaluation.Compared with other measurement methods, there is an abrupt rise for tumblestrength measurements with direct test method at a certain valve lift condition and themeasurements are relatively larger. In view of the above, an investigation intocharacteristics of in-cylinder tumble flow in a four-valve gasoline engine is presented.The experimental works were carried out on an in-house steady flow test rig bycombining necessary optical accesses and visualization devices for directly exploringin-cylinder air motion. PIV was employed for evaluating effects of various geometryparameters on flow field and microstructures, in order to acquire the uniform tumbletest method conductive to guide the development and performance evaluation ofports.The results show that large-scale counterclockwise tumble flows can be formedand the slope ratio of tumble ratio curve has apparent increase, when the valve haveadequate opening. The in-cylinder flow field is very sensitive to the in-cylindergeometry in different in-cylinder position, the small blow hole, which leads to squishflow motion,will accelerate the tumble flow;on the other side,the large blow hole willrestrain the tumble flow.The most affected area is the one near the blow hole wherethe tumble ratio can increase up to2.77with cylinder A, of which the blow hole area is1/4of the buttom area of the cylinder. From the results, it also suggests that theevolution of in-cylinder tumble flow is basically dominated by the conservation ofangular momentum, while the change of in-cylinder geometry can always result insome difference on tumble ratio.