Diagnosis Mechanism Of Mesoscopic-scale Tomography Image For Airflow Field In Internal Combustion Engine

Diagnosis technology of intake flow field is one of the most effective ways to support improvement of the research level of internal combustion engine high-efficiency clean combustion of fossil energy and the development of turbulence experiment technology based on space-time multi-scale dynamics.The problem is that the existing optical engine and numerical simulation research methods are difficult to acquire the thermodynamic information and multi-dimensional dynamics information of the intake flow field in the cylinder of the internal combustion engine which is a closed confined space in a non-destructive,real-time,and real way.A mesoscale-based tomographic image diagnosis principle and method of the intake flow field of an internal combustion engine is proposed.This has important academic value and significant practical significance to promote the rapid development of the strategic industry of made in China 2025.The main research contents of the paper are as follows:1.In-cylinder intake flow field information and its numerical simulation analysis of internal combustion engine.The thermodynamic information and the multi-dimensional kinematics information of the intake flow field are analyzed.On this basis,the in-cylinder intake system model of single-cylinder diesel engine based on AVL-Fire is established,and the intake flow field is simulated and analyzed in different speed.The variation law of thermodynamic state parameters such as density,pressure,and temperature in the in-cylinder intake flow field of steady and unsteady state at different crank angles and positions are obtained.Besides,the evolution of vortex,tumble,turbulent during the intake flow process is obtained.2.Research on the measurement of tomography image and diagnosis methods of cylinder intake flow field.Aiming at the problem that it is difficult to acquire the thermodynamic and the multi-dimensional kinematics information of the gas micro-cluster in a closed space of an internal combustion engine cylinder really and non-destructively,the interaction law between high-energy X-rays and the intake system of an internal combustion engine and the mechanism of signal generation in tomographic images are analyzed.The influencing factors of the tomographic image signal and noise are analyzed.A single-source tomography imaging method for the steady-state flow field is discussed,and the tomographic image reconstruction method for the intake system is studied.The principle and method of tomographic image diagnosis for the intake system of an internal combustion engine based on mesoscale are proposed.With this method,the thermodynamic and multi-dimensional kinematics information of the in-cylinder intake system can be obtained and diagnosed in a non-destructive and real-time way.3?Research on feature measurements and identification mechanism in tomographic image for weak intake gas.According to the features of the intake gas in cylinder showed in tomographic image is weak signal,an information enhancement based maximum mutual information for weak gas in tomographic image which includes geometry space information and gray scale information is pointed out.The feature recognition method of intake vortex tomography image based on K-means clustering is studied.The measurement of the vortex core,the direction of rotation and the streamline of the intake vortex in the cylinder is realized.The multi-object segmentation method based on maximum between-cluster variance is used to identify the features of in-cylinder intake gas micro-cluster in mesoscale which includes structure,area,density and distribution.4.Experimental study on the diagnosis of steady-state intake flow field tomography image in diesel engine cylinder.A single cylinder diesel engine has been taken as object and single-source tomographic experimental system includes 4MeV high energy X-ray based on linear accelerator is designed.The results show that the gas density distribution and the motion features obtained by tomographic images of in-cylinder intake flow in steady state are similar to its numerical simulation characteristics.The structure of micro-cluster in mesoscale includes loop chain,random conformation and star topology,and flow pattern includes vortex and turbulent is the results of micro-cluster interaction.