Performance Simulation Of Diesel Engine Based On Miller Cycle And Research On Piston Heat Load

As a power plant,diesel engine plays a very important role in the development and construction of the society by virtue of its own power,wide coverage,high efficiency of heat energy utilization,and good stability and reliability.However,with the gradual shortage of oil resources,the atmospheric environment in which people are living is deteriorating,and the use and improvement of diesel engines will also face a difficult situation.It is always the research direction of experts and scholars to improve the thermal efficiency of diesel engine and reduce the emission index of diesel engine.The Miller cycle has emerged as the times require.Miller cycle based on the Otto cycle,through the early intake valve closing time and delayed intake valve closing time,these two forms of action,let the diesel engine generate a new working cycle mode.Compared with the traditional diesel engine,a Miller cycle model under the actual compression stroke is shortened,resulting in expansion ratio is greater than the compression ratio,the mixed gas expansion work can further enhance the release,the thermal efficiency of the diesel engine;on the other hand the Miller cycle,reduce the cylinder temperature and pressure,temperature to reduce NO_x emissions of diesel engine play a significant role in reducing pressure,ensure the stability of working process of diesel engine.Based on the parameters of DK-28 diesel engine and the requirements of setting up the AVL_BOOST software,a diesel engine simulation model is set up in this paper.The influence of the Miller cycle mode on the performance of the diesel engine is simulated by changing the intake gate lift curve to change the closing time of the inlet valve in the AVL_BOOST software.With 10 degrees CA as the interval,under 50%and 25%two working conditions,6 sets of 12 sets of Miller cycle modes were set up to calculate the influence of intake valve delay closing angle on diesel engine power,average effective pressure,effective fuel consumption rate,cylinder temperature and cylinder pressure.And the calculation results are calculated at the top of DK-28 diesel engine piston 50%working condition and 25%Miller cycle model under boundary conditions by using AVL_BOOST simulation,calculated with empirical formula of the piston side and the inner cavity of the piston boundary condition,loading the ANSYS software to calculate import,steady-state temperature field and stress field simulation results of piston.The simulation software of the AVL_BOOST engine is combined with the ANSYS finite element analysis software.By the performance simulation of AVL_BOOST 50%and 25%operating conditions of diesel engine cycle model calculation results show that the Miller Miller cycle to enhance the thermal efficiency of diesel engine;reduce the temperature and pressure inside the cylinder;50%under the condition of DK-28 diesel engine Miller cyclic model of optimum intake gate delay angle is 30 degrees CA;25%cases.40degrees CA.By ANSYS finite element simulation of the 50%conditions and 25%under the condition of steady temperature of diesel engine piston Miller cycle mode distribution,thermal stress distribution of the deformation force distribution and heat with the Miller cycle delay the intake valve closing angle,the maximum temperature of the piston,the heat should be decreased and the maximum thermal deformation the amount of.The change trend of piston temperature is generally started from the top of the piston to the piston skirt position decreased gradually,the highest temperature in the combustion chamber at the top,the lowest temperature at the bottom end of the piston skirt piston;the overall thermal stress is small,the distribution of thermal stress is gradually decreased from the piston the position of the head to the piston skirt part of the piston is located on the edge of the top surface of the trend;the maximum thermal deformation of the piston,and the deformation from the top of the piston to the piston skirt is gradually reduced,is located in the inner end of the piston pin minimum thermal deformation.