| As an important power source of transportation vehicles,diesel engines are of great significance for their performance simulation and analysis.In previous research,simulation is mostly used in single academic field,that is,only the thermodynamic system or dynamic system is studied,while the diesel engine,as a complex power machine integrated by multiple systems,its thermal system and power system are mutually boundaryd and affect each other.The simulation study of a single system cannot fully reflect the working process and overall performance of the diesel engine,and the real-time performance is poor,which is not conducive to the research and design of the diesel engine.Therefore,it is necessary to establish a thermodynamic coupling model of the diesel engine to study the performance of the diesel engine to improve its reliability and reduce costs.In this paper,on the basis of simplifying the model of each component of the diesel engine,according to the simulation methods of text modeling and modular modeling,and using the multi-domain unified modeling language Modelica,a simulation model including the thermodynamic system and dynamic system of the diesel engine is established directly in an integrated environment library.The sub-models are connected to realize the coupling of the thermodynamic system and the dynamic system by Modelica’s own real number interface,self-built gas interface and numerical conversion model.The steady-state simulation and dynamic simulation are performed by the coupled model to verify its correctness.In addition,the quantitative analysis method was used to study the influence of parameters such as injection start angle,compression ratio and valve lift on power and emissions performance of diesel engine on the coupled model,including power,in-cylinder pressure,exhaust temperature and fuel consumption rate.The results show that the maximum pressure in the cylinder decreases and the phase corresponding to the maximum pressure increases,with the increase of injection starting angle.The maximum burst pressure and the maximum temperature in the cylinder increases,and the temperature of exhaust manifold decreases,with the increase of compression ratio.The maximum burst pressure in the cylinder decreases and the fuel consumption rate increases,with the increase of valve lift.As the result,the injection starting angle can be reduced,the compression ratio can be increased and the valve lift can be reduced to improve the dynamic performance of diesel engine.The injection starting angle can be reduced and the compression ratio can be increased to improve its emission performance.In order to study the interaction of various factors,the orthogonal experimental analysis method is adopted.The results show that the biggest factor affecting the power of diesel engine is the lift of exhaust valve,followed by the compression ratio,and finally the injection starting angle.The biggest factor affecting the cylinder pressure is the lift of exhaust valve and the smallest is the injection starting angle.And the most important factor affecting the pre vortex temperature is the compression ratio,followed by the lift of exhaust valve,and finally the injection start angle.As the result,the valve lift has the greatest impact on the power performance,and the compression ratio has the greatest impact on the emission performance of diesel engine.Finally,the optimal parameter combination is determined by genetic algorithm. |
