Research On Multi-field Coupling Simulation Of Piston Temperature For Natural Gas Engine

Nowadays, with the requirements of environment protection and emission control regulations, low emission for engine is required urgently besides good economy and high power performance. As a kind of alternative fuel, natural gas has lots of advantages including large quantity of resource, good completeness of combustion and low emission, so it has been widely used in engine. The thermal load in natural gas engine is higher than other types and this character will affect its working reliability and limit its potential to strengthen. During heat transfer processes in engine, the piston components can transfer30%to40%of the total released heat, so the pistons will bear tremendous thermal stress. The main factors that affect the thermal stress are piston temperature and temperature gradient distribution, thus research and analysis on natural gas engine piston’s temperature field is necessary.A vehicle natural gas engine was taken as the research object in this thesis. On the basis of former researches and the actual structure of the given piston, the piston temperature storage and testing system was designed, reliability experiment and error calibration for the system was also completed. And a contrast test using hardness plug was designed. At the same time, the piston’s temperature field multi-field coupling simulation models including processes in cylinder, components solid heat transfer, cooling water flow heat transfer were established for accurate description of the heat transfer process of piston. By the simulation results the analysis on temperature field was finished.The reliability experiment and error calibration results indicate that the designed system can satisfy the requirements of measurement. The simulation results indicate that the maximum temperature and temperature gradient in the piston are relatively high; the temperature at the first ring groove is close to the limit working temperature of lubricating oil, when the engine is working under long period and high load operation or frequent start conditions, faults may occur due to high thermal load. The reasonable methods to solve this problem are mainly through organizing the combustion in better way, optimizing the piston structure; strengthen the heat transfer character of the cooling liquid and some other ways to lessen the thermal load of the pistons in natural gas engine.