Piston Ring Dynamics Analysis And Structure Optimization Based On Blow-by

Blow-by in crankcase is one of the most important indicators that affect the engineperformance, fuel economy and emission, for a long time, researchers has adopted variousmeasures to limit blow-by to meet increasingly stringent performance requirements andemissions standards. Factors that affect engine running gas are complex, Test the blow-by byusing the traditional method, and research the influence of structure parameters and thedynamic of piston and piston ring to the blow-by is influenced by many limitations such astesting accuracy, time and cost, can’t meet the requirements of modern structure optimizationof piston and piston ring.The influence of blow-by to the performance of engine and the ways of blow-by areresearched in this paper, using AVL Glide piston friction pair, fully considered the influenceof working conditions in cylinder, piston stiffness, radial deformation of piston under thermalloads and radial deformation of cylinder liner under thermal coupling condition to dynamicsof piston and piston rings. On the basis, the blow-by and friction loss are analyzed, providingan effective method for optimal design of piston ring structure, and using the orthogonaldesign to optimize the structure. The following research works are carried out in this paper:(1) The dynamics of piston rings and blow-by theoretical analysis. The dynamics modelof piston ring and ideal gas adiabatic flow model are established, researching the stressconditions and dynamics behavior of piston ring, on the basis the ways of blow-by of pistonrings are analyzed.(2) Research for the boundary conditions of calculating piston and cylinder liner radialdeformation. AVL Boost model was set up to calculate boundary conditions in cylinder,thermal and mechanical loads theory of piston and cylinder liner were analyzed.(3) Piston friction model was set up. Piston stiffness matrix was calculated, andboundary conditions such as thermal and mechanical load of piston and cylinder liner. Theradial deformation of piston and cylinder liner under thermal-mechanical coupling conditionswere calculated by using ANSYS. According to these datas, the piston friction pair was established, and analyzing the blow-by and the dynamics and tribological state of the pistonring.(4) Analyzing the factors that affect the friction loss and blow-by. Analysing a maturediesel engine as an example, AVL Glide friction pair model was established, the influence ofpiston closed gap，radial elastic, the radial and axial clearance between piston and ring, andsome other important structure parameters of piston and ring to blow-by and friction loss.And according to the dynamics data of first and second ring, the methods of controllingblow-by were analyzed.(5) Optimizing the piston ring structure according to the conclusion obtained above, aorthogonal test was designed, with the orthogonal table, the blow-by and friction loss werecalculated and evaluated, the optimal design of structure of piston ring are obtained.