동일 압축비를 갖는 디젤엔진 연소실의 형상변경에 따른 압축말기 유동 비교

A numerical study of the air motion during the compression stroke has been done. The piston bowl shape was chosen as the parameters while the compression ratio was fixed. About twenty different shapes of piston bowl were designed in order to see the effect of piston bowl diameter, reentrant angle and the pip height. For the typical heavy duty engine of 130 mm bore, bowl diameters were varied from 60 to 100 mm. The combined effects of reentrant ratio and pip height were also examined; varying d₁/d₂ from 0.7 to 1.0 and 1/h from 0.4 to 1.0. It was shown that the bowl diameter played a key role in determining the swirling air motion near TDC. The reentrant type bowl promoted turbulence intensity and retained high swirl flow even after TDC. On the other hand, the flow structure was less affected by the pip. The effect of IVC swirl on the tumble flow structure near TDC was discussed.