Design And Research Of Adjustable Reed Intercooler For Diesel Engine Based On CFD Technology

Turbocharging has been widely used in the fields of automobile,ship,and aviation.Its main function is to increase the engine intake volume by compressing air,so that the engine power can be increased greatly.However,after the supercharging,the air temperature will also rise,which limits the increase of the engine's charging efficiency,causes the engine to burn too high and increases the emission of nitrogen oxides.In order to solve a series of problems caused by rising air temperature after pressurization,intercooling technology came into being.Although the current intercooling technology is rather mature,the ordinary intercooler will still be used if the engine is at the start or idle speed,which will make the temperature of air entering the engine cylinder too low.Too low intake air temperature will extend the combustion preheating time,which is not conducive to combustion and will also reduce the engine power.So in order to ensure that the cylinder can obtain a rather stable intake air temperature under different working conditions,a reed intercooler with adjustable cooling area is proposed.This paper selected aluminum,air-cooled,tube-fin and wave finned intercooler as the research subjects.According to the 2D drawings provided by a company and the 3D modeling software solidworks2016,the model of the ordinary intercooler was established.By using related knowledge of mechanics of materials,the specific design position and size of the reed were calculated,and the model of reed half-opened intercooler with adjustable cooling area has been simplified.The hypermesh software was used to divide the 3D mesh,and then CFD(Computational Fluid Dynamics)technology was used to solve smooth core tube and the ribbed core tube under high working conditions in the fluent of the intercooler and got the pressure,temperature,speed and other cloud maps.Taking the temperature drop as the main heat-transfer assessment criteria,the flow field analysis showed that the heat transfer effect of the ribbed core tube is better than the smooth core tube,and the ribbed core tube was determined as the structural basis of a new adjustable reed intercooler design.The flow field analysis was carried out by using four new schemes:the new intercooler reed is full-opened and half-opened under different working conditions,and the cooling efficiency and pressure loss check were performed.It was concluded that under low working conditions,the reed is full-opened(simulating the ordinary intercooler),and the over-cooling problem occurred at the exit.After taking the reed half-opened optimization scheme,the cooling efficiency and pressure loss both met the calibration standard.In the case of the intercooler outlet temperature has been improved,effectively avoiding the problem of over-cooling;if the reed is half-opened under high working conditions,there will be a lack of heat exchange and cooling.To achieve the best cooling,the full-opened reed can be used.Since the reed opening angle can be changed according to the working condition,it can ensure that the temperature of the engine discharging the intercooler(entering the cylinder)under different working conditions can be maintained within a reasonable range,so as to avoid over-cooling under low working condition and the insufficient cooling under high working condition.Furthermore,it can ensure the smooth operation of the combustion and maximize the momentum and economy of the diesel engine as much as possible.Finally,the matching calculation of a certain type of diesel engine intercooling system was conducted.The thermodynamic calculations were carried out for the full-opened and half-opened of the intercooler reed under high and low conditions.The final result indicated that the selection is reasonable.