Research On Boiling Heat Transfer Model Of Engine Cooling Water Chamber

Internal combustion engine is one of the most common machinery.The engine will be highly fortified and own high power density as the improvement of dynamic performance and increasingly strict emission regulations.It will inevitably result in an increase in outbreak of cylinder head thermal load and explosion pressure.The heat transfer ability of the cooling system is also facing a huge challenge.There is a certain degree of boiling heat transfer phenomenon in the cylinder head water jacket.It can strengthen the ability of heat transfer.How to reasonable use of boiling heat transfer's high heat transfer capability is the key to realize precise cooling of the internal combustion engine cooling system.It also is the future trend of the development of internal combustion engine cooling system.In order to better use of the it's boiling heat transfer capability,the boiling phenomenon needs to be studied experimentally.Combined with CFD numerical analysis,the boiling heat transfer model applicable to the internal combustion engine cooling system is obtained.But the cylinder head water jacket structure complexity and variability of boiling heat transfer.So the conventional experimental methods cannot work.We can study the influence of different factors on the boiling heat transfer based on bench test of equivalent cross section channel.Combined with single phase homogeneous flow boiling heat transfer model,the numerical simulation of engine cooling system is made.In this paper,we can study the boiling heat exchange phenomenon and the application of single-phase homogeneous flow boiling model in the following aspects:1)It is the most direct and effective way to study boiling phenomena through simple channels.In this paper,we can learn the boiling heat transfer through the establishment of the boiling heat transfer in a rectangular cross section channel,horizontal heating test bench.Study the influence of work stress,mainstream medium flow rate and temperature on the boiling heat transfer with cast iron heating metal material on the basis of electromagnetic induction.The starting point of boiling point is lower when the increase of medium velocity,the lower the main body temperature and the higher the working pressure.2)Based on the single phase convective heat transfer model,the bubbles and liquid medium as a kind of mixed phase.The concept of bubble share was introduced to reflect the intensity of boiling and the distribution of bubbles.Based on the conservation law of mass,the equation of gas rate control is deduced,and the equation is solved by combining the single flow control equation.The existing classical boiling heat exchange experience formula is compared with the experimental data of boiling bench.The Franz progressive model was modified according to the data of boiling bench test.The applicability of the model in the numerical calculation of engine cooling system is greatly improved.3)With Duets226-B diesel engine as the test object,the engine running test was carried out under rated conditions.The temperature of fire surface of cylinder head,the inside of the cylinder head and the water jacket's bottom of cylinder head was measured by thermocouple method and hardness plug method.Then we can analyze the temperature field distribution of cylinder head,and the comparison basis is provided for the simulation calculation of engine cooling system.4)In order to investigate the effect of boiling phenomenon on the heat transfer of medium in cylinder head,the engine cooling system is simulated based on the fluid-solid coupling algorithm.Comparison of simulation results and cylinder head temperature test data,the simulation results are closer to the experimental data when considering the boiling heat exchange.The relative error of the temperature of the cylinder cover is 37%lower than that of the boiling heat exchange.The relative error of the internal temperature of the cylinder cover at 7mm from the fire surface was 37%lower than that of the boiling heat exchange.The accuracy of different boiling models is compared and analyzed by using the simulation results in Fu Song's thesis.The results show that the accuracy of Franz model is higher than that of the Rohsenow model.