| The locomotive powered by internal combustion engine is one of the main railway traction powers. With the development of technology and the increase of the railway transportation tasks, high reliable internal combustion engines are urgently required. The surface temperature of the exhaust pipe is very high, undoubtedly, this is a great threat to the safety of locomotive. Therefore, in this paper through numerical and experimental methods, a new type of heat insulating exhaust pipe is developed to reduce the outer surface temperature of the exhaust pipe, and then lower the fire disaster possibility of the locomotive caused by the high temperature of the exhaust pipe outer surface.Internal combustion engine exhaust pipe is mainly composed of the exhaust manifold, the exhaust branch pipe and the corrugated pipe. In general, the outer surface temperature of the exhaust pipe reaches as high as600℃during working condition, once the fuel or lubricating oil pipe near the exhaust pipe leaks due to the unpredicted reasons, the fuel or lubricating oil will split and spray on the surface of the exhaust pipe with high temperature, in this case, the locomotive will be on fire easily and immeasurable loss is caused. This paper designs a new type of heat insulation exhaust pipe by using3D design software SolidWorks according to the structure and size of the exhaust pipe of the internal combustion engine firstly. The new type of exhaust pipe is consisted of three layers with thin-wall steel tube, the gap of each two layers is vacuum, in addition, the heat insulation sandwich structure, which is a mixture of the economical and applicable aluminum acid salt cement and the high temperature refractory material, is used in the structure of the flange. Then simulation is conducted by using the finite element analysis software ANSYS to study the temperature field of flange under different structures, and the influence of different structures and material thermal conductivities to temperature field of flange is analyzed. Finally, by using the network approach of the radiation heat transfer, the radiation heat of the two-layer and three-layer exhaust pipe models are calculated. The calculation results reveal that different surface conditions of the exhaust pipe have great influence on the temperature of the outer surface.Based on the above analysis and design, several new types of heat insulation exhaust pipe are designed, and the test equipment is built to measure the surface temperature of the new exhaust pipe. Meanwhile, the thermal conductivity of the insulation material is measured by the quasi-steady state method, and the value is0.362W/(m.K). The surface emissivity of the exhaust pipe is measured by the comparison method, which is0.7. The temperature of the exhausted gas, the outer surface of the new type exhaust pipe and the insulation flange are measured by using nickel chrome-nickel silicon thermocouple. When the engine is operating stably, by measuring the temperature of exhaust gas and the outer surface of the exhaust pipe under different revolving speed and power values, it is show that the temperature of the outer surface of the heat insulation exhaust pipe is60%lower than that of the exhaust gas, while as compared to the temperature of the general exhaust pipe, it is30%～50%lower, with the increase of the engine power, the temperature of the outer surface of the insulated exhaust pipe increases more slowly than the exhaust and general exhaust pipe, therefore, the insulated exhaust pipe performs well in heat insulating. This indicates that the heat insulation exhaust pipe designed in this paper has high efficiency and practicability in reducing the outer surface temperature of exhaust pipe of the internal combustion engine and improving the environment of the power room, thus it will laid a good foundation for researchers to develop new types of low temperature exhaust pipe. |
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