By an iteration method, the influence of oil film inertia on piston skirt lubrication in a high speed engine is investigated. By alternately solving the Navier-Stocks equations and the Reynolds equation, the new itera...By an iteration method, the influence of oil film inertia on piston skirt lubrication in a high speed engine is investigated. By alternately solving the Navier-Stocks equations and the Reynolds equation, the new iteration method can trace the variations of velocity field and pressure field with time. Based on this, the mixed-lubrication model suitable for the piston skirt of high engines is proposed. By introducing the inertia coefficient, the new lubrication model includes the inertia term in oil film. The model can be also used to solve for the lubrication performances of a piston skirt in low or medium speed engines and for lubrication problem in general excluding the inertia term of oil film , when the inertia coefficient is put equal to zero. The calculation results show that the influence of oil film inertia on the friction force increases with the ratio of the piston skirt's length to its diameter, the inertia coefficient and the eccentricities of the lower and the upper piston skirt, with other conditions kept constant, while the influence of it on the load capacity of oil film is small.展开更多
To eliminate the defects during piston skirt isothermal forming process,simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA.D...To eliminate the defects during piston skirt isothermal forming process,simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA.Deformation pattern,metal flow and influence of process parameters were concluded.The prediction load value with a relative error of 4.98% is more accurate to the testing one than that from the empirical formula whose relative error is up to 50.8%.Finally,based on the simulation results,an improved process at 300 ℃ and 0.005-0.05 s-1 was verified without any defects by the physical try-out.展开更多
Based on the rigid-plastic theory, the finite element method (FEM) equation which incorporates the influence of impact load and volume force is presented. The hammer forging theory for simulation is also given. On the...Based on the rigid-plastic theory, the finite element method (FEM) equation which incorporates the influence of impact load and volume force is presented. The hammer forging theory for simulation is also given. On the basis of technological analyses, the piston skirt forging processes of LD11 aluminium alloy are simulated under both mechanical pressure forging and hammer forging conditions. By comparison with the metal flow, fibre flow lines, distributions of strain and temperature of the two forging methods, practical forging was carried out and the product quality was controlled. The deformation pattern of the piston skirt forging process was determined by comparing the simulation results with the practical forging results.展开更多
A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers th...A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers the surfaceroughness and profile. The corresponding computer program can be used to calculate oscillatory motion of piston during the entire trajectory, which has the excellent convergence.In addition, a set of equipment, which adopt the laser induced fluorescent method, was developed to measure the oil film thickness between the piston and the bore.展开更多
基金National Natural Science Foundation of China (Grant No. 59990472)
文摘By an iteration method, the influence of oil film inertia on piston skirt lubrication in a high speed engine is investigated. By alternately solving the Navier-Stocks equations and the Reynolds equation, the new iteration method can trace the variations of velocity field and pressure field with time. Based on this, the mixed-lubrication model suitable for the piston skirt of high engines is proposed. By introducing the inertia coefficient, the new lubrication model includes the inertia term in oil film. The model can be also used to solve for the lubrication performances of a piston skirt in low or medium speed engines and for lubrication problem in general excluding the inertia term of oil film , when the inertia coefficient is put equal to zero. The calculation results show that the influence of oil film inertia on the friction force increases with the ratio of the piston skirt's length to its diameter, the inertia coefficient and the eccentricities of the lower and the upper piston skirt, with other conditions kept constant, while the influence of it on the load capacity of oil film is small.
文摘To eliminate the defects during piston skirt isothermal forming process,simulations under different process parameters such as the deformation temperature and friction factor were analyzed with the rigid-plastic FEA.Deformation pattern,metal flow and influence of process parameters were concluded.The prediction load value with a relative error of 4.98% is more accurate to the testing one than that from the empirical formula whose relative error is up to 50.8%.Finally,based on the simulation results,an improved process at 300 ℃ and 0.005-0.05 s-1 was verified without any defects by the physical try-out.
文摘Based on the rigid-plastic theory, the finite element method (FEM) equation which incorporates the influence of impact load and volume force is presented. The hammer forging theory for simulation is also given. On the basis of technological analyses, the piston skirt forging processes of LD11 aluminium alloy are simulated under both mechanical pressure forging and hammer forging conditions. By comparison with the metal flow, fibre flow lines, distributions of strain and temperature of the two forging methods, practical forging was carried out and the product quality was controlled. The deformation pattern of the piston skirt forging process was determined by comparing the simulation results with the practical forging results.
文摘A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers the surfaceroughness and profile. The corresponding computer program can be used to calculate oscillatory motion of piston during the entire trajectory, which has the excellent convergence.In addition, a set of equipment, which adopt the laser induced fluorescent method, was developed to measure the oil film thickness between the piston and the bore.
