One of the proposed concepts for spark ignition engines is advanced port fuel injection(APFI),which suggests using two port injectors for each cylinder.In this research,we numerically examine the capabilities of this ...One of the proposed concepts for spark ignition engines is advanced port fuel injection(APFI),which suggests using two port injectors for each cylinder.In this research,we numerically examine the capabilities of this concept in reducing fuel consumption and increasing engine performance.The results demonstrated that the use of this concept is very effective due to the use of two injectors and the possibility of reducing the spraying time and bringing the injection start time closer to the air inlet valve opening time.The maximum amount of fuel film formed on the walls is reduced by about 75%,naturally,which leads to better and more homogeneous fuel distribution inside the combustion chamber and increases combustion efficiency.The results showed that under the same boundary conditions and engine operating point,the use of two port injectors for each cylinder leads to an increase of more than 20%of the maximum combustion chamber pressure and about 4%combustion efficiency.On the other hand,fuel film formation becomes worse in cold conditions.So in this study,the capabilities of this concept in cold conditions were investigated too.Investigations have shown that the advanced port fuel injection,unlike conventional engines,is almost insensitive to inlet temperature changes.展开更多
In this study,we considered the wetting phenomenon on a general substrate from a new viewpoint of continuum mechanics.The analyses first show how the Wenzel and the Cassie models deviate the practical results in some ...In this study,we considered the wetting phenomenon on a general substrate from a new viewpoint of continuum mechanics.The analyses first show how the Wenzel and the Cassie models deviate the practical results in some special substrates,and then elucidate the mechanism of the triple contact line(TCL) moving.Based upon variational theory of the total free functional dealing with the movable boundary condition,we show that the macroscopic contact angle(MCA) expression is the corresponding transversality condition.It manifests that the MCA depends only on the chemical and geometric property at the TCL,and is not affected by the gravity of the droplet and the contact area beneath the liquid.Our continuum model also shows the exploration of the pinning effect on a sharp wedge or the interface between two different phases.This investigation will help designing super-hydrophobic materials for novel micro-fluidic devices.展开更多
文摘One of the proposed concepts for spark ignition engines is advanced port fuel injection(APFI),which suggests using two port injectors for each cylinder.In this research,we numerically examine the capabilities of this concept in reducing fuel consumption and increasing engine performance.The results demonstrated that the use of this concept is very effective due to the use of two injectors and the possibility of reducing the spraying time and bringing the injection start time closer to the air inlet valve opening time.The maximum amount of fuel film formed on the walls is reduced by about 75%,naturally,which leads to better and more homogeneous fuel distribution inside the combustion chamber and increases combustion efficiency.The results showed that under the same boundary conditions and engine operating point,the use of two port injectors for each cylinder leads to an increase of more than 20%of the maximum combustion chamber pressure and about 4%combustion efficiency.On the other hand,fuel film formation becomes worse in cold conditions.So in this study,the capabilities of this concept in cold conditions were investigated too.Investigations have shown that the advanced port fuel injection,unlike conventional engines,is almost insensitive to inlet temperature changes.
基金supported by the National Natural Science Foundation of China(Grant Nos.10802099,11272357 and 11102140)the Doctoral Fund of Ministry of Education of China(Grant No.20110141120024)+2 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2009AQ006)the Opening Project of State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology)(Grant No. KFJJ12-11M)the support from the Brain Korea 21 Program at Seoul National University
文摘In this study,we considered the wetting phenomenon on a general substrate from a new viewpoint of continuum mechanics.The analyses first show how the Wenzel and the Cassie models deviate the practical results in some special substrates,and then elucidate the mechanism of the triple contact line(TCL) moving.Based upon variational theory of the total free functional dealing with the movable boundary condition,we show that the macroscopic contact angle(MCA) expression is the corresponding transversality condition.It manifests that the MCA depends only on the chemical and geometric property at the TCL,and is not affected by the gravity of the droplet and the contact area beneath the liquid.Our continuum model also shows the exploration of the pinning effect on a sharp wedge or the interface between two different phases.This investigation will help designing super-hydrophobic materials for novel micro-fluidic devices.
