CFD Analysis Based On Different Cooling Medium Of Water Jacket Flow Field Of Diesel Engine

With more and more attention of low carbon environmental problem, it is significance toimprove engine performances for development of Diesel Engine Industry and the emissionstandard，national economic construction and national defense. The structure design of thecooling water，the selection of the cooling medium, the speed of flow velocity, the size of thepressure, the quality of the heat exchanger and the distribution of flow field inside the wholewater jacket affected engine cooling system working ability, thus affecting the whole engineperformance and the whole car performance. The selection of cooling fluid is also important,the engine cooling effect is different because of different cooling fluid have different physicalcharacteristics. Adding a suitable coolant for cooling can prolong the service life of the engine,improve the power and the combustible mixed gas quality, increase the torque, reduce fuelconsumption, reduce the repair and replacement.In this paper, first,building three-dimensional model according to the certain the12Vtype diesel engine cooling water jacket drawings and mesh. Then select four kinds of coolingfluids with MEG and MPG respectively as basic solution, including one kinds of watercoolant50﹪H2O+50﹪MEG and three anhydrous coolant50﹪H2O+50﹪MEG、50﹪MEG+50﹪MPG、25﹪MEG+75﹪MPG和75﹪MEG+25﹪MPG，the physical parametersof cooling liquid was calculated by ASPEN PLUS simulation software. At90℃aim at thewater coolant and anhydrous coolant effect of the cooling fluid to use CFD technology tosimulate engine cooling of water jacket. Through the comparison of the simulated results ofwater coolant and anhydrous cooling fluid and their physical properties comparison analysisfound that anhydrous coolant in practical application can not only meet the coolingrequirements of the engine, but also improve its durability, fuel economy. Then according to the numerical simulations analysis of different proportion of components in the anhydrouscoolant on the cooling effect of the engine at50℃、70℃、90℃、100℃temperatures. Basedon the above, this article draws the following conclusion：（1）The anhydrous coolant compaired to water coolant,its flow rate and average heattransfer coefficients were less than water coolant in the water jacket, but its average value andin the high heat load of key parts of the distribution are basically meet reference values of thedomestic and foreign water jacket CFD simulation calculation. Therefore, according to theanhydrous coolant and water coolant heat physical differences, the use of anhydrous coolantis helpful to improve the durability of the engine and fuel economy performance.（2）The analysis found that，due to the viscosity of propylene glycol is far lower thanthat of ethylene glycol in100-120℃, it can increase the flow rate of the anhydrous coolant andimprove the cooling jacket cooling effect by increasing ratio of propylene glycol. Butconsidering the ethylene glycol freezing point is-13.2℃, and its thermal conductivity higherthan that of propylene glycol. So in order to reduce the coolant freezing point both do notaffect the cooling liquid cooling effect on the premise, we should based on the actual engineworking environment to confect the coolant.（3）Through the analysis of the simulation of anhydrous coolant at50℃、70℃、90℃、100℃found that, because the Surface coefficient of heat transfer of a cooling liquid changesare mainly affected by the cooling fluid viscosity and thermal conductivity, and the twofactors will change as the temperature changes, so that surface heat transfer coefficientchanges in two cases when the temperature change：（a）low temperature, thermal conductivityof cooling liquid has dominant effection on its surface heat transfer coefficient, surface heattransfer coefficient decreased with the increase of temperature.（b）At higher temperatures,viscosity of cooling liquid has dominant effection on its surface heat transfer coefficient,surface heat transfer coefficient increase with the increase of temperature..