The modeling of inlet and exhaust systems of internal combustion engine is very important in order to evaluate the engine performance.This paper presents new pressure losses models which can be included in a one dimen...The modeling of inlet and exhaust systems of internal combustion engine is very important in order to evaluate the engine performance.This paper presents new pressure losses models which can be included in a one dimensional engine simulation code.In a first part,a CFD analysis is made in order to show the importance of the density in the modeling approach.Then,the CFD code is used,as a numerical test bench,for the pressure losses models development.These coefficients depend on the geometrical characteristics of the junction and an experimental validation is made with the use of a shock tube test bench.All the models are then included in the engine simulation code of the laboratory.The numerical calculation of unsteady compressible flow,in each pipe of the inlet and exhaust systems,is made and the calculated engine torque is compared with experimental measurements.展开更多
This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered wi...This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.展开更多
文摘The modeling of inlet and exhaust systems of internal combustion engine is very important in order to evaluate the engine performance.This paper presents new pressure losses models which can be included in a one dimensional engine simulation code.In a first part,a CFD analysis is made in order to show the importance of the density in the modeling approach.Then,the CFD code is used,as a numerical test bench,for the pressure losses models development.These coefficients depend on the geometrical characteristics of the junction and an experimental validation is made with the use of a shock tube test bench.All the models are then included in the engine simulation code of the laboratory.The numerical calculation of unsteady compressible flow,in each pipe of the inlet and exhaust systems,is made and the calculated engine torque is compared with experimental measurements.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50537020 and 50528707)
文摘This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.
