The Research Of Kinematic And Dynamic Characters Of Opposed Piston Engines

With the development of technology, more and more attention is put on noise, vibration and harshness (NVH) character of mechanisms. Several new types internal combustion engines resuscitate to fulfill the requirements. The main idea of this thesis is researching the kinematic, structure and dynamic characters of Opposed Piston Engines (OPEs), and analyses their application prospect explicitly.The research process consisted three portions. Firstly, the basic constraint loads were solved, using theoretical physic analysis technology. The fundamental parameter, which was critical in the following structure design, was determined. Secondly, a4stroke diesel engine Wartsila6L20was chosen as the referenced type, a prototype of V type OPEs was designed, named6V20-OP. By using the multi-body dynamics software ADAMS, its constraint behaviors and output performance was researched in consideration of crankshaft flexibility. Lastly, for the main bearings span with a relative large distance, finite element method (FEM) was used to evaluate the crankshaft stress and strain situation.The main works and concludes of this paper are as follows:1. The analysis of OPEs basic dynamic and load obtained their equations related to several fundamental structure and motion parameters. Thanks to the opposed pistons, OPEs’piston speed is low, and crank radius is a quarter of stroke. Combustion forces only excite relatively low side loads and act none load on main bearings, which only bear the imbalance inertia and centrifugal forces.2. Based on the relationship between each structure parameters, draw on traditional criteria for the structural design of reciprocating diesel engine, the crank-piston system of a6cylinders V type OPE was designed. Its pistons, connecting rod, crankshaft and connections fulfill assembly and movement requirements. In the absence of cylinder head assemblies (cylinder recharging realized by pistons switch cylinder air ports), OPEs possess a relatively simple structure, which helped to reduce the overall quality.3. The simulation processed in ADAMS using rigid&flex coupling method revealed several inherent characteristics of OPEs.(1) Compare to4-stroke engines obtain the same power,6V20-OP engine suffers relatively small forces on its crankshaft main bearings and outer skeleton.(2) The combustion pressure of6V20-OP is lower to6L20, lead to a relative quiet running performance.(3) Crankshaft main bearings loads equivalent small portion of combustion pressure. The maximum value is only27%of peak explosion pressure.4By using FEM software ANSYS, crankshaft transient dynamic analysis was carried out. Although main bearings span distance is large, it comes out the deformation of crankshaft is acceptable, because the gas force tend to. self-balance. The maximum tress of crankshaft is an exciting155.7MPa which result from an un-optimized structure.The study shows that OPEs possess dynamic advantages to conventional engines, especially NVH performance is significantly better than that of4-stroke engines. If progress is obtained on combustion and exhaust, OPEs will have a bright application prospect.