Study On The Working Performance Characteristics And Operating Mechanism Of A Free Piston Natural Gas Engine

In order to alleviate the increasingly tense energy and environmental pollution problems,researchers from various countries have also carried out research on new power plants while optimizing the combustion emissions of traditional engines.Natural gas burns cleanly,can effectively reduce the greenhouse effect,and has a lower cost.Compared with gasoline and diesel,it has its own unique advantages.Free-piston linear engine is a kind of power output device proposed in recent years.Because it does not have a crank-link mechanism,it has much less friction loss than traditional engines,but there are still few free-piston engines that use natural gas as fuel.Therefore,this paper combines natural gas fuel and free-piston engines,and uses numerical simulation methods to explore the performance characteristics of free-piston linear natural gas engines.The main work of this article is : According to the operating characteristics of the twostroke free-piston engine,the thermodynamic model and the dynamic model were established,and a simulation model were established by the Simulink software.After simplified calculation of the dynamic model,the operating characteristics of the free-piston engine nature gas were analyzed.Obtain the initial motion law of free piston through dynamic and thermodynamic equations,three-dimensional simulation model was established,generated the moving mesh model with the piston motion law by FIRE software.After multiple coupling iterations of the three-dimensional simulation and dynamic equations,A more accurate piston motion were obtained,and the combustion heat release process of a free piston natural gas engine was simulated and analyzed based on this piston motion.Finally,the established model were used to study the effect of different parameters on the free-piston natural gas engine.The analysis results show that the motion process of the free-piston natural gas engine system is a single-degree-of-freedom variable-damped forced vibration.The acceleration of the piston motion is about twice that of the traditional natural gas engine.Free-piston natural gas engines have lower in-cylinder pressure,indicated thermal efficiency,and temperature than traditional natural gas engines;however,NO and Soot emissions have a huge advantage over traditional natural gas engines.The Ignition delay period of a free-piston natural gas engine is not much different from that of a conventional engine.The rapid combustion period is slightly shorter,and the after-combustion period is very long.There is a serious after-combustion phenomenon.The peak pressure and maximum displacement of the free piston natural gas engine increase with the increase of the piston mass,the peak velocity and the piston operating frequency decrease with the increase of the piston mass,the peak pressure in the cylinder,the peak velocity,the maximum displacement of the piston and the piston operation the frequency increases with the increase of the equivalence ratio,and decreases with the increase of the load.