Experimental Study On The Effect Of Anhydrous Cooling Medium On The Performance Of Internal Combustion Engine

With the rapid development of internal combustion engine in the direction of high combustion temperature,high cylinder pressure and high power density,the cooling and heat dissipation of the whole engine,especially the combustion chamber components,are facing great challenges.In recent years,scholars around world have found that the new type of anhydrous cooling medium has the characteristics of high boiling point,long service life,cavitation prevention and good heat transfer performance,which can meet the working requirements of internal combustion engine for cooling medium.It is a key step to study that the physical properties,heat transfer characteristics and different components of new anhydrous cooling medium and its influence on the performance of internal combustion engine.Therefore,this thesis adopts the method of experimental research to develop a new type of anhydrous cooling medium with propylene glycol as the base liquid and ethylene glycol and glycerol as the mixture liquid.It measures the thermal properties of different components of cooling medium and tests the heat transfer characteristics.It studies the influence of temperature on the thermal properties of different components of cooling medium,which provides physical guidance for the study of the heat transfer characteristics of anhydrous cooling medium.The influence of the different component cooling mediums on the heat transfer characteristics provides a theoretical basis for the application of anhydrous cooling medium in internal combustion engines.First of all,three new anhydrous cooling medium with volume fraction of 75% propylene glycol-25% glycerol(cooling medium I),75% propylene glycol-25% glycol(cooling medium II)and 100% propylene glycol(cooling medium III)guided by the performance requirements of internal combustion engine for cooling medium were prepared.The thermophysical properties of the prepared cooling medium were measured and evaluated.The results show that : compared with the conventional cooling medium,the boiling point(≥ 150 ℃)of the new anhydrous cooling medium is higher,and it has excellent anti-boiling performance;the thermal conductivity and specific heat capacity of the conventional cooling medium at the same temperature are 1.5 times and 1.2 times of the new anhydrous cooling medium respectively;the density difference of the different cooling mediums at different temperatures is small,which is 0.02 g/cm3.At high temperature,the viscosity difference of different cooling mediums is relatively small.At low temperature,the viscosity of cooling medium I is too large to meet the performance requirements of internal combustion engine.Therefore,the main research object is cooling medium II and cooling medium III,and more in-depth research is carried out.A test platform for simulating the cooling water flow channel of internal combustion engine under the guidance of the research on the thermophysical properties of the new anhydrous cooling medium was built to measure and analyze the parameters such as heat flow density,heating wall temperature,etc.and to explore the influence of inlet flow rate,inlet temperature and different components of cooling medium on the heat transfer characteristics.The test results show that: the relationship between the heat flux density and the wall temperature is basically positive linear.When the wall temperature increases,the heat flux density increases.The lower the inlet temperature is,the higher the heat flow density will be at the same wall temperature.The heat flow density of conventional cooling medium and anhydrous cooling medium will increase by about 30% and 10% respectively for each 10 ℃ lower inlet temperature.Most importantly,due to the high boiling point physical properties of the anhydrous cooling medium,it still maintains a good single-phase convective heat transfer at a high wall temperature of 160 ℃,which can meet the heat dissipation requirements of the internal combustion engine running under continuous and heavy load conditions,which is incomparable to the conventional cooling medium.Secondly,the diesel engine performance test system was built.The operating temperature,exhaust emissions,fuel consumption and other parameters of the diesel engine were compared and analyzed.The impact of different cooling media on the performance of the diesel engine has been explored.The test results show that: when the circulating temperature of cooling water tank of diesel engine test bench is set at 80 ℃,the outlet temperature of cooling liquid using conventional cooling medium,cooling medium II and cooling medium III is 82.1 ℃,81.14 ℃ and 80.77 ℃,respectively,and the average temperature of lubricating oil rises by 5 ℃.When the circulating temperature of cooling water tank of diesel engine test bench is set at 95 ℃.The outlet temperature of 3 kinds of cooling medium are equal,so as the lubricating oil temperature.Compared with the conventional cooling medium,the smoke,CO and HC emissions of the diesel engine using the new type of anhydrous cooling medium are reduced to some extent.Especially in the case of higher smoke,CO and HC emissions,the reduction effect is more significant.The NOx emissions increase about 30% when the cycle temperature of the cooling water tank of the test bench is set at 95 ℃ and under the condition of large load,and the other conditions increase less.In terms of fuel consumption,the 2 new types of anhydrous cooling media used in the diesel engine have achieved the effect of reducing fuel consumption compared with the conventional cooling media.When the cycle temperature of cooling water tank in the test bench is set at 95 ℃,the weighted average fuel consumption of cooling medium III used in the diesel engine is 3.11% lower than that of conventional cooling medium.