The components of combustion chamber (cylinder head-cylinder liner-piston assembly-oil film) were taken as a coupled body.Based on the three-dimensional heat transfer numerical simulation of the coupled body,a coupled three-dimensional calculation model for in-cylinder working process and the combustion chamber components was built with domain decomposition and boundary coupled method,which implements the coupled three-dimensional simulation of in-cylinder working process and the combustion chamber components.The model was applied in the influence investigation of the space non-uniformity in heat transfer among combustion chamber components on the generation of in-cylinder emissions:NOx.The results showed that the heat transfer space non-uniformity of combustion chamber components directly influences the formation of in-cylinder NOx.The main area being influenced was the accessory area on the wall,while the influence on the generation of NOx in the central area couold be omitted.
Combustion chamber components (cylinder head-cylinder liner-piston assembly-fuel film) were treated as a coupled body. Based on the three-dimensional numerical simulation of heat transfer of the coupled body, the multi-dimensional simulation computation coupling flow and solid on working process and combustion chamber components of internal combustion engine was performed using Discrete Transfer Radiation Model (DTRM) radiation heat transfer model, zoning solution method and boundary coupling method. The simulation was applied to the influence investigation of the space non-uniformity in radiation heat transfer among combustion chamber components on the generation of in-cylinder soot emissions. The results show that the space non-uniformity in heat transfer among the combustion chamber components has great influence on the generation of in-cylinder NOx emissions. The difference value of total soot in cylinder when exhaust valves are opened is 1.3% (no radiation), 0.8% (radiation). So the effect of radiation heat transfer space non-uniformity of combustion chamber components on total soot production can be ignored. While in local area radiation heat transfer space non-uniformity has certain effect on soot production inside whole combustion chamber space, and has less effect on soot production in the area near the wall of combustion chamber components.
Lü JiZu1, BAI MinLi2 & LI XiaoJie1 1 State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116023, China
An innovative flat heat pipe radiator was put forward,and it has the features of high efficiency of heat dissipation,compact construction,low thermal resistance,light weight,low cost,and anti-dust-deposition. The thermal analysis of the flat heat pipe radiator for cooling high-power light emitting diode (LED) array was conducted. The thermal characteristics of the flat heat pipe radiator under the different heat loads and incline angles were investigated experimentally in natural convection. An electro-thermal conversion method was used to measure the junction temperature of the LED chips. It is found that the integral temperature distribution of the flat heat pipe radiator is reasonable and uniform. The total thermal resistance of the flat heat pipe radiator varies in the range of 0.38-0.45 K/W. The junction temperatures of LED chips with the flat heat pipe radiator and with the aluminum board at the same forward current of 0.35 A are 52.5 and 75.2 oC,respectively.
Combustion chamber components(cylinder head,cylinder liner,piston assembly and oil film) are treated as a coupled body.Based on the three-dimensional numerical simulation of heat transfer of the coupled body,a coupled three-dimensional calculation model for the in-cylinder working process and the combustion chamber components was built with domain decomposition and boundary coupling method,in which the coupled three-dimensional simulation of in-cylinder working process and the combustion chamber components was adopted.The simulation was applied in the influence investigation of the space non-uniformity in heat transfer among combustion chamber components on the generation of in-cylinder emissions.The results show that the space non-uniformity in heat transfer among the combustion chamber components has great influence on the generation of in-cylinder NOx emissions.The heat transfer space non-uniformity of combustion chamber components has little effect on soot formation,and far less effect on soot formation than on NOx.Under two situations of different wall temperature distributions,the soot in cylinder is different by 1.3% when exhaust valves are open.
To make heat conduction equation embody the essence of physical phenomenon under study,dimensionless factors were introduced and the transient heat conduction equation and its boundary conditions were transformed to dimensionless forms.Then,a theoretical solution model of transient heat conduction problem in one-dimensional double-layer composite medium was built utilizing the natural eigenfunction expansion method.In order to verify the validity of the model,the results of the above theoretical solution were compared with those of finite element method.The results by the two methods are in a good agreement.The maximum errors by the two methods appear when τ(τ is nondimensional time) equals 0.1 near the boundaries of ξ =1(ξ is nondimensional space coordinate) and ξ =4.As τ increases,the error decreases gradually,and when τ =5 the results of both solutions have almost no change with the variation of coordinate ξ.
