Research On Thermal Load Of The Cylinder Head Based On The Optical Fiber Thermometry

The engine develops in the direction of high power density, low fuel consumption, low emissions and high reliability due to the influences of environmental and economic factors, so the explosion pressure, thermal load and stress level of the engine increase, which put forward a test to the reliability of the engine components. Cylinder head is one of the diesel engine components which are most prone to failure. Research on thermal load of the cylinder head is of great significance.In this paper, the research on thermal load of the cylinder head of the226B four-cylinder diesel engine is conducted through the test combined with numerical simulation.In the test, temperature measurement of10points in5small load conditions is conducted through the methods of thermocouple thermometry and optical fiber thermometry. The10points are located on the wall of the cooling water-jacket and the wall which is7mm away from the firedeck. At the same time, the relevant data of cooling water, inlet and exhaust are measured.In the study on the temperature field of the cylinder head, numerical simulation method is used, considering of the heat transfer between the solid walls of the cylinder head and its contact components. The boundary conditions of gas side are obtained by the simulation of thermodynamic cycle and the combustion in the cylinder. The dimensionless distribution of the heat transfer coefficient, which is used in the finite element simulation,is obtained by the function of wall mapping. Then the heat transfer coefficient of gas side in different working conditions is obtained by using the average heat transfer coefficient of thermodynamic cycle and the dimensionless distribution of the heat transfer coefficient. The boiling heat transfer is considered in the numerical simulation of the cooling water-jacket, and the results are the lateral boundary conditions combined the boundary conditions of gas side to proceed the finite element coupling simulation. In the meantime, the heat transfer coefficient of cooling water-jacket is revised many times, which can improve the accuracy of numerical simulation.In this paper, the temperature field of the cylinder head and the wall temperature distribution of the cooling water-jacket are obtained by numerical simulation. Some conclusions are conducted by comparing the results of the test and the simulation. Firstly, the optical fiber thermometry can be applied on the temperature measurement of the engine cylinder head. Secondly, the method, which obtains the boundary conditions of gas side by the dimensionless distribution of heat transfer coefficient on the firedeck, can improve the accuracy and efficiency. At last, using the thermal power of the cooling water-jacket to estimate the accuracy of the numerical simulation, the thermal load of the cylinder head can be effectively evaluated by the method of combining test with numerical simulation.