Modeling And Simulation Analysis Of Thermal-dynamic Coupling Of Diesel Engine Based On Modelica Language

The diesel engine is a kind of thermal machine that realizes the efficient conversion of fuel chemical energy to mechanical energy.The thermodynamics and dynamics are coupled and the process is extremely complicated.At present,ordinary commercial software can only simulate these two processes separately,can not achieve diesel thermodynamic coupling,and the openness of commercial software is very low.In the joint simulation of large power plants,diesel engines are only one of them.Taking into account these factors,this paper builds a diesel engine thermodynamic system,a dynamics system model library and its coupling model based on the multi-domain unified language Modelica on the Mworks platform.Based on this,the diesel engine thermodynamics and dynamics are jointly simulated and analyzed.Firstly,according to the actual structure of the diesel engine,the diesel engine is divided into several interconnected and independent sub-modules(intake and exhaust pipes,turbochargers,etc.according to different systems(in-cylinder process,intake and exhaust system,crank-link mechanism,etc.).Injector,piston,connecting rod,etc.).Based on the internal differential equation of the diesel engine components on the Modelica compiler simulation platform Morks,a model library based on the Modelica language was established.Taking the TBD620 single-cylinder diesel engine and the TBD620V12 diesel engine as an example,according to its actual physical structure,sub-modules are selected from the established diesel engine model library,and these modules are connected to each other by interfaces to external air source temperature,pressure and combustion chamber.The wall temperature is used as the boundary condition,the diesel engine size structure parameters are set up to establish the diesel engine simulation model,and the simulated pressure results under different loads are compared with the experimental values to prove the correctness of the built diesel engine model;thermodynamic module and power The data transmission between the modules is carried out through the interface,such as pressure change and speed change,so as to realize the joint simulation,and the performance parameters such as the rotational speed,piston displacement and reciprocating inertial forceof the diesel engine from start to steady time are obtained,and they are respectively stable.The thermodynamic performance and dynamic performance of the diesel engine were analyzed.The dynamic simulation of diesel engine load characteristics was carried out by using the established co-simulation model.The diesel engine was analyzed from the sudden increase and decrease of the diesel engine from 25% to 100% load.The characteristic parameters vary with time.On the basis of the built diesel engine model,different diesel engine compression ratios,fuel injection advance angles and gas distribution phases are selected for optimization.Taking the 1800 rpm condition as an example,after optimizing the compression ratio,the fuel consumption rate decreased by 1.48%,and the effective power increased by 2.21%.After optimizing the fuel injection advance angle,the fuel consumption rate decreased by 1.61%,and the effective power increased.2.63%;after optimizing the intake cam offset angle,the fuel consumption rate decreased by 0.4%,the effective power increased by 0.62%;after optimizing the exhaust cam offset angle,the fuel consumption rate decreased by 0.4%,and the effective power increased.0.62%.