Diesel Engine Piston Assembly Dynamics Influencing Factors

Taking the piston components of 2D25 horizontal two cylinder diesel engine as the research subject in this paper, the dynamic analysis has been done by means of AVL EXCITE Piston & Rings software, and it consists of three parts, piston second-order movement, the oil consumption of the engine and the crankshaft blow-by gas.For the analysis of piston second-order movement, research has been done on several parts such as cylinder matching clearance, the position of middle convex point of the skirt, the oval of skirt, the offset of piston pin and the structure of piston head. Different programs were brought forward facing each factor, and the maximum striking energy, the friction loss was compared among different programs, finally coming to the best program. From several aspects such as tangential elasticity of the piston ring, ring back clearance, open clearance, the cross section of the first ring and scraping oil edge offset, the affecting laws of each factor were analyzed for the oil consumption quantity of the engine, coming to the reasonable program. And the blow-by gas was analyzed by means of the aspects of the ring grooves, the thickness of cylinder, and "three clearances" of rings.The research results indicate that:(1) On the basis of other parameters that are from original program for the engine keeping invariant, the cylinder matching clearance decreasing 0.02mm, middle convex point moving down 5mm, the maximum striking energy of piston will declines 28% but the friction loss power increasing 2.7% only. If the piston head adopting oval and tapered design (the tapered increasing 0.1mm, the oval taking 0.13mm), the maximum striking energy of piston will declines 13%.(2) The factors that affect oil consumption significantly are ring tangential elasticity, the cross section of the first ring and the open clearance of the second ring. When the tangential elasticity of the three rings takes 75N,60N,75N respectively, oil consumption declines 4.7% while friction power loss increasing 2.8%, which is the most reasonable program among the elasticity programs. When the first cross section adopts the improvement asymmetric barrel design, the oil consumption declines 6.3%, also the oil consumption declining when the second ring open clearance increases, and when the second ring open clearance increases 0.2mm, the oil consumption declines 8.2%.(3) The chamfering of piston ring grooves has overwhelming effect on the blow-by gas quantity. The chamfering of the grooves is bigger than 0.2mm, the quantity of blow-by gas increasing rapidly. Taking each factor into consideration competitively, the chamfering of first ring and second ring both taking 0. lmm is more reasonable. The C-balance settings adopted reasonably can decline blow-by gas quantity remarkably. For example, when the open clearance of first ring takes 0.35mm, the second takes 0.7mm, and the oil ring takes 0.35mm, the quantity of blow-by gas decreases 27.1%.