Research On Non-Circular Of Cylinder Liner In I.C.Engine

It is common that the cylinder liner is non-circular when engine is firing or not, and this has great influence on engine's performance including power, economy, environmental protection and durability. Because of the analytic difficulty coming from the complexity of engine body structure, variety of the static and dynamic relationship between components,forces and heats, the researchers can only use some experimental formulas in engine design, and this block our understanding of its forming theory and process. It is an important work for the researcher to reduce the negative effects from the non-circular of the cylinder liner. The main tasks of this paper are not only to comprehensive assess each factor according to numerical simulating results, but also to calculating deformation and non-circular of the cylinder liner caused by multiple factors. We also study the piston ring conformability, oil film thickness between piston ring and cylinder liner along circumferential direction and oil consumption considering non-circular of cylinder liner.At the beginning of this dissertation, the present status of the joint bolts preloading model, dynamical calculation of crankshaft are reviewed. Using pressure-time data from engine test , the deformation and non-circular of the cylinder liner are numerical calculated in rated and maximum torque condition considering influence of all mechanical factors including joint blot preloading, piston thrust force and gas pressure on engine block-equal stiff head model. Each mechanical factor is comprehensive assessed after discussion of the deformation results.Secondly, using traditional thermal boundary conditions, the temperature distribution, thermal deformation of the block-equal stiff head simulating mode and distortion of the cylinder liner are calculated and analyzed. The influence of each traditional thermal factor to distortion of cylinder liner is discussed.Thirdly, based on conjugate heat transfer theory, considering influence of coolant flow, the temperature distribution of cylinder block-cooling water coupling model and thermal deformation of the cylinder liners was calculated with the help from the calculating results of CFD analysis for the whole cooling water system. The flow and pressure field of the whole cooling system, the temperature distribution of the coupling model and thermal deformation of the cylinder liners were demonstrated, which showed that the temperature and thermal deformation had remarkable changes along axial and circumferential direction, and these also provided theoretical evidence for failure simulation and optimization design of diesel engine.Fourthly, the temperature of multiple key dots in the cylinder inner surface of machined dry liner engine under different working conditions are measured using thermocouple sensors and thermal tour detector in order to verify simulation models that are used in traditional thermal analysis and fluid-solid couple analysis. The characteristics of temperature distribution and the changing relation between working temperature of cylinder liner and working condition—speed and torque—are studied. By comparison to the test results, it shows that the fluid-solid coupled analysis method is reasonable and efficient.Fifthly, considering multiple causing factors including mechanical and thermal load, the more reasonable distortion of the cylinder liner is examined in real condition, thus provided a kind of more accurate and high efficiency means to evaluate the performance of the piston-piston ring-cylinder liner set.Sixthly, a computational model for examining the conformability of piston ring to deformed cylinder is developed. This computational model incorporates Fourier Fat Transfer that is used to fit and analysis the deformed cylinder bore data and algorithm method that is used to calculating the curvature change of the ring between free state and mounted state. The contact pressure between ring and bore through an engine cycle is calculated, and the seal of the ring is also assessed.Seventhly, in order to predict the effect of cylinder deformed on oil consumption, a simple and easy technique to calculate the film thickness in deformed cylinder is developed. The model takes into account of the ring tension, gas pressure and film support pressure and their interactions to calculate the deformation of the ring in the cylinder using the theorem of the three moments. The film thickness along both circumferential and axial direction through whole engine cycle is calculated and evaluated in the end.Eighthly, a model that used the oil film thickness obtained from the above chapter to calculate the amount of oil transported to combustion chamber by passing between ring and cylinder is proposed. The model takes into account of three major part of oil passing to the chamber, including the amount of oil scraped by ring through whole engine cycle, the amount of oil thrown by inertial force, the amount of oil pushed by reversed gas pressure during certain crank angels. The amount of oil transportation in the deformed cylinder is calculated and is compared with the one in the round cylinder.Finally, essential work and some certain innovative points of this dissertation are summarized. Some suggestions for the future research on this field are presented by the author.