Study On Combustion And Emission Characteristics Of A Small Rotating Internal Combustion Engine

In the context of today’s energy problems and environmental problems,as a power device on small and medium-sized aircraft,the engine’s own thermal efficiency,emissions,weight,volume and other problems limit the practical performance of small and medium-sized aircraft.Therefore,it is urgent to develop energy power with high power-to-weight ratio,less exhaust emission pollution,and small proportion of space.On this basis,a small rotating internal combustion engine was proposed.Small rotating internal combustion engines have the characteristics of simple structure,small size and high power density,which are very suitable for small and medium-sized aircraft,low-power power generation and individual combat equipment.The specific work of this article is as follows:(1)According to the working environment and working principle of the small rotating internal combustion engine,the overall structure of the internal combustion engine was designed,and a solid prototype was produced.The contour line of the inner groove wheel mechanism controlling the intake is studied,a mathematical model is established,and the optimal stroke angle of the inner groove wheel is found by comparing and analyzing the speed and acceleration changes of the inner groove wheel mechanism at different stroke angles,and finally the contour line of the inner groove wheel is generated by fitting the curve.In addition,a set of direction conversion devices was designed to solve the problem of inconsistent running direction of the output shaft of small rotating internal combustion engines.(2)In order to make the ignition system better match the internal combustion engine and achieve accurate ignition at high speed,the ignition system was optimized and an experimental platform was built to verify the reliability of the ignition system.At the same time,the CFD model was preprocessed,boundary conditions and meshing were set,and the appropriate turbulence model and combustion model were selected according to the working characteristics of the internal combustion engine to establish the mathematical model,and the relevant parameters were set,and the grid independence was verified.(3)Through the study of the flow field,combustion and emission characteristics of small rotating internal combustion engines,it is found that the intake form has a great influence on the cylinder smoothness of rotating internal combustion engines.The vortex formed by the end cover inlet air in the middle of the combustion chamber can fully mix the fuel and air in the cylinder,and the mixture is evenly distributed in the combustion chamber to effectively promote the spread of flame.The end cover inlet combustion initially produces a flame group in the center of the combustion chamber,under the condition of high pressure,the turbulent flame velocity increases,the flame quickly spreads to the entire combustion chamber,at this time the pressure in the cylinder is higher than the surrounding intake structure,the heat release is increased by 4.3%relative to the surrounding intake structure,and the total amount of HC and CO produced is 26.8%and 15.7%less,respectively.It can be seen that the end cover intake structure is more fully burned and the exhaust emission is cleaner,which meets the requirements of small and medium-sized aircraft.(4)Through the study of turbulent kinetic energy,combustion heat release,peak temperature and pressure in the cylinder,fuel consumption rate and emission characteristics of small rotary internal combustion engine,it is found that with the increase of ignition advance angle,the turbulent kinetic energy decreases,the turbulent kinetic energy at the ignition advance angle of 5° is significantly higher than the turbulent kinetic energy at the ignition advance angle of 7°,the peak pressure in the cylinder is increased by 2.3%compared with other schemes,the fuel consumption rate is high,and the combustion is more complete.In addition,the amount of CO and HC generated when the ignition advance angle is 5° in terms of emission characteristics should be reduced by 35%and 35.3%,respectively,indicating that the mixture burns more fully in the combustion chamber,and it can be seen that the performance of the internal combustion engine is best when the ignition advance angle is 5°.