The Study Of The Test Methods Used On The Premixed Turbulent Combustion In Engine's Cylinder

The motion state of working fluid in engine's cylinder has an important impact on the formation speed and quality,the ignition and combustion process of the mixture.It has an important influence on the engine power,economy and characteristics of emission.In order to ulteriorly improve the performance of the engine,it is necessary to know the law of the flow field and combustion.The visualization of the motion state of working-fluid and combustion in the cylinder is the most direct and effective means to understand the law of the fresh flow,the formation and development of the flame,and the formation of pollutants.This paper aimed at realizing the visualization of the turbulent premixed combustion in the engine's cylinder,and an optical engine based on the XF 250 motorcycle engine was designed and made for the study of visual test method of the turbulent combustion in the engine's cylinder,and then the optical engine test bench was built.On the basis of this optical engine's bench,the combustion process of images in the cylinder was acquired by the high speed camera system named FASTCAM-ultima-512,then the different speeds of combustion sequence diagram were drawn respectively.The result shows that the gasoline with some engine oil can enhances the flame luminosity when it is in combustion,which can realize the visualization of the turbulent premixed combustion in the gasoline engine's cylinder.According to the combustion sequence diagrams of different speeds conditions,the core disappeared quickly,but not developed into flame fronts immediately.The core drift to somewhere with the turbulent in the cylinder,which leads to the position in which the obvious flame front formed is not around the spark plug or the cylinder center.In order to enough time to completely burn the fuel in the cylinder,the advance of ignition is varied with the increase of the speed.Although the high speed can improve the intensity of turbulence in the cylinder,which accelerates the mixture formation,high speed sharply shorten the time of the mixing.It leads to the result that the mixture cannot mix evenly without enough time.Furthermore,it causes the combustion's deterioration or misfire.In addition,the turbulent in the cylinder of the optical engine was tested on the compressing condition by the high-speed camera system and the Schlieren system designed by ourselves,and the sequence diagram of the turbulent in the cylinder was drawn.The results show that the Schlieren system can be used on the test of the turbulent field visualization in cylinder,and the turbulent state of the working-mixture in the cylinder is very complex.With the piston to the TDC,the working-mixture is compressed continuously in the cylinder,the turbulent state has become more intense,and the density gradient is bigger.Before TDC,it leads to cylinder flow test of Schlieren images become clearer with increasing of the crank angle,and the flow state is more complex.The Schlieren images of the flow field test become gradually fuzzy with increasing crank angle after TDC.