| The calculation of piston temperature field is an important part in the research of piston working reliability. As the most effective way to reduce the temperature of piston, the piston oil-inject shaking cooling can provide a more accurate third type boundary condition to obtain more accurate temperature distribution of the piston by analyzing its process of flow and heat transfer, thus supply the oil-inject shaking cooling with more rational design and evaluation basis. Using piston ISLe375with cooling cavity as the object of study, the experiment is conducted and measure the total cooling injected oil and the oil quantity out of the cooling cavity with different oil-inject pressure on the base of which the computational model of the piston oil-inject shaking cooling is established in this paper and simulate the flow distribution characteristics and shaking cooling heat transfer of the cooling oil in the cooling cavity of piston both in steady state and transient processes using the CFD software Fluent. By comparison, the experimental results and simulation results match well. And in the end, the temperature field of piston ISLe375is calculated taking advantage of the CFD transient results.The main contents of this paper include four aspects as follow:(1)Firstly, build the experimental platform for piston oil-inject measurement under steady state. Secondly, for ISLe375piston, the total amount of oil injected and out of the cooling cavity in a certain period of time under different injection pressure is measured. Then, analyze the relationship between the oil amount out of the cooling cavity and the piston locations as well as the change in the oil amount out of the cooling cavity owing to the different oil-inject pressure.(2)In the case of numerical simulation, firstly, establish the steady model of the piston oil-inject cooling and steady state and obtain the quantity of both the total oil injected and oil out of the cooling cavity under the experimental conditions. Verify the correctness of the steady simulation by means of compare the simulation results with the experimental results. Secondly, analyze the volume fraction and the flow characteristics of cooling oil in the cooling cavity with different piston locations and are discover the coordination relationship between the nozzle and the cooling cavity. Besides, different oil-inject angles are simulated and its effect on the results.(3) However, the actual work of the piston is not static, so it is better to simulate the transient process according to the movement characteristics of the piston. Simulate the fill rate of the cooling oil in cooling cavity, the instantaneous oil mass flow of the import and export of the cooling gallery and the shaking cooling heat transfer situation at different moments in the whole cycle with different injection speed, injection angles and piston speed using dynamic grid. The transient results are also compared with the steady results and by analyzing the relationship between the oil-inject speed, angles, piston speed and the heat transfer coefficient.(4) The temperature field distribution of piston without any cooling method is obtained using FEA software, and then temperature field distribution of piston with oil-inject shaking cooling is simulated by projecting heat transfer coefficient and oil temperature simulated in CFD calculation as the third boundary conditions on the finite elements besides the gas temperature and the heat transfer empirical formula of the other wall of the piston. The heat transfer coefficient and oil temperature on the cooling cavity wall are the average values of time and space. Then compare the different between two pistons, thus analyzing the meaning of the oil-inject shaking cooling in the change of temperature field of piston. |
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