The Optimization Analysis Of Heavy Duty Diesel Engine Pre-heater

With the application of renewable energy, the research to engine cold start becomes more and more, especially for heavy vehicles. Sometimes the diesel engine could not start in the cold winter. What’s more, in the process of engine cold start, the pollutants can be up to 60%-80% of the whole stage. The vehicle pre-heater, as the main technological mean of improving the engine cold start, is gradually widely used. Therefore, in the paper, through theoretical analysis, experimental test and numerical simulation, the structural characteristics, combustion characteristic and heating characteristics of the diesel engine pre-heater are studied.At first, the pre-heater works is analyzed. From the analysis, it is shown that the pre-heater work process covers the mixture combustion of fuel and air, and the fluid flow and heat transfer between the high temperature gas and the cooling liquid. The paper combined the chemical kinetics and the mass and heat transfer theories, defined the boundary conditions of CFD simulation.Secondly, through the fuel pre-heater bench experiment, the boundary conditions of CFD simulation are attained and the data needed in the theoretical calculation of the pre-heater are gotten such as environment temperature, pre-heater exhaust gas composition, exhaust gas temperature and the import and export water temperature. Meanwhile, the combustion efficiency and heat transfer efficiency of the old and new pre-heater is calculated by the British BS845 standard. The importance of pre-heater structure to the pre-heater’s efficiency is put forward. At the same time, the flow characteristics and combustion characteristics are analyzed by the CFD simulation. The structure improvement and design direction of pre-heater is put forward. The experiment results and the simulation results are compared, and the simulated error is calculated.Then, the spoiler is applied to the combustion chamber of the pre-heater to improve the pre-heater structure. Through the CFD simulation, it is shown that the spoiler can improve the pre-heater efficiency, and there are two parameters which decide the spoiler characteristic, namely the reentrant diameter of the pre-heater and the distance between the spoiler and the bottom of the heat exchange tube. Through the CFD simulation, it is shown that the pre-heater can obtain the maximum efficiency when the reentrant diameter is 70 mm, and the distance is 60 mm. The efficiency will increase by 17.58%.It is shown that the fuel consumption of diesel engine will be reduced by 5%-6% when the diesel temperature increases to 56℃-75℃ through the literature. Therefore, the equipment to warm up the oil pipeline is designed, namely through taking advantage of liquid coolants of pre-heater to heat the oil pipeline. Meanwhile, It is proved that this idea is reasonable through the theoretical calculation and simulation analysis.Finally, the article discusses the effect of pre-heater to crew comfort. A device is designed for warming up the crew capsule, the cockpit and engine with using pre-heater, and the device is also carried on the installation and the control system developed. Meanwhile, the original car heating system is test by vehicle trial and the device is also simulated by CFD software. Through the simulation and experiment, the device designed in this paper, can greatly improve the crew comfort greatly.