Mixing Enhancement by a Bump Ring in a Combustion Chamber for Compound Combustion

Effect of distributions of fuel concentration and temperature on ignition processes in diesel PCCI combustion

“…But the in-cylinder mean temperatures in all test PCCI combustion are much lower than that of conventional combustion. As given by Su et al [3][4][5]7], for all test cases, NO emissions are very low, while CO and uHC emissions are very high. But the phenomenon may be practically good enough in organizing low engine-out emissions combustion, if combining PCCI combustion with lean diffusion combustion (LDC) [2][3][4][5][6], which was a kind of two stage combustion.…”

“…Looking at the calculated values of HðfÞ in case 1, case 2 and case 4, the intake pressure increases from 0.132 MPa to 0.163 MPa and 0.184 MPa, which result in increased ununiformity. This may be explained by the effect of spray confinement due to the increase of in-cylinder pressure [3][4][5][6] which results in short penetrations. 4.2 Effect of mixture stratification on ignition process Figure 5 shows the history of the in-cylinder temperature and equivalence ratio distribution for case 1 and case 5.…”

“…1-exhaust gas analyzer; 2-Bosch smoke meter; 3-single cylinder exhaust port; 4-pressure controlling valve; 5-EGR pipe; 6-controlling valve; 7-common rail injector; 8-single cylinder inlet port; 9-air tank; 10-pressure control valve; 11-air compressor; 12-common rail; 13-fuel pump; 14-control system; 15-exhaust pipe In order to understand the homogeneity of the mixture organized by multi-pulse injection in the cylinder at a certain crank angle, the fuel/air equivalence ratio frequency gðfÞ was used in Ref. [5] which manifested the fuel mass fractions at a certain interval of fuel/air equivalence ratio. The equivalence ratio frequency gðfÞ was very directly perceived in graphical analysis, but it was hard to be perceived in computer fluid dynamics (CFD) modeling.…”

“…In the studies of Su et al [2][3][4][5][6][7], it was found that premixed diesel combustion by early multi-pulse injection could not avoid fuel and temperature stratification, but was characterized by much lower overall local fuel/air equivalence ratio compared with conventional diesel combustion. It was also found that the ignition, the heat release and the emissions were influenced by different stratification.…”

“…In this paper, the characteristic-time combustion model is used to simulate the roles of various stratifications of fuel and temperature prepared by multi-pulse injection strategy proposed Refs. [2][3][4][5][6][7].…”