Study Of Predicted Temperature Model Of Fire Surface In Strengthened Diesel Engine

Because of the need of social development and construction of national defense, strengthened diesel engine is getting more and more intensive. As a result, the thermal load of the cylinder head is becoming higher and higher, and heat cracking of fire surface is frequently occurred. The reliability and durability of cylinder head is a growing problem. It is urgent to realize the real-time monitoring and cooling optimization of the temperature field of fire surface. The temperature of fire surface is hard to measure, but the outside temperature is easy to measure and monitor. Therefore, we can establish the links between the temperature of fire surface and outside temperature through the mathematical model. So the temperature of fire surface can be speculated by measuring the outside temperature and we can monitor it in real time. It is important to improve the durability and reliability of strengthened diesel engine.This paper is devote to the temperature field distribution of cylinder head and the establishment of thermal network model by combination of experiment, numerical simulation of fluid-solid coupling and mathematical modeling of thermal network. The main contents and conclusions are as follows:Firstly, carry on the thermal load test of cylinder head. The operating conditions are 2100 r/min, 1900 r/min, 1700 r/min, 1500 r/min and 1300 r/min engine speed under full load. We can measure the temperatures of 21 specific points and other operating parameters of cylinder head and cooling system under each condition.Next, use AVL_FIRE to do numerical simulation of fluid-solid coupling of cylinder head and cooling water jacket. The data of the simulation are compared with the data of the thermal load test. It is indicated that the errors between the temperatures of the simulation and temperatures of the test are all below 5%. It is believed that both the data are reliable and they can be used to establish thermal network models.Then, finish the work of establishing a thermal network model with the data under the engine speed from 2100 r/min to 1500 r/min. Choose three different heat transfer paths and do the calculation. It shows that the overall heat transfer of the cylinder head is stable and the fluctuation is quite small under different conditions. Carry on the calibration with the data under the engine speed 1300 r/min according to the relational formulas. We can find that the regressions of the calculated values and the simulation values are quite good and all the errors are very small. Besides, the data utilization ratio is higher and anti-interference ability is stronger in the scheme of three.Finally, broaden the thermal network model at the basis of the existing model. Choose the scheme of integrated heat transfer path to do the calculation. It shows that the regressions of the calculated values and the simulation values of the broadening model are still good. On the other hand, the temperature field distribution of the cylinder head is more perfect and the measuring points are easier to measure. What's more, the stability is enhanced.