Abstract
For the opposed-piston and opposed-cylinder (OPOC) diesel engine with higher power density, recently it has drawn even more attentions than ever in several developed countries, such USA and Germany, et al, which is regarded as a technical innovation to further reduce emission, and decrease fuel consumption, attributed to outstanding thermal efficiency and engine package downsizing. To explore the interrelation of this special crank system in concept design stage, the multi-body dynamics and durability of the piston-opposed crankshaft system was investigated. Firstly the optimized function model of the unique crankshaft system in an OP2S (Opposed-piston two stroke) engine was established. Then it was to figure out the influence of all structural design parameters on OPE crankshaft averaged output torque, respectively. The calculated results show that the initial crank angle difference between inner crank web and outer crank web was the most critical contributor to elevate the averaged torque output than other structural parameters. The parametric 3D model of crankshaft system was refreshed automatically based on the optimized variables. Finally an OPE crankshaft prototype was manufactured and bend fatigue experiment was carried out in a relevant laboratory to obtain the material S-N Curve. The HCF (High Cycle Fatigue) result was indicated that the minimum safety factor on crank journal fillets can reach relevant estimation criterion without crankshaft failure occurring for an engine speed sweep.
Highlights
It is well known that the in-line or V type of IC engine has already occupied the majority of market share and widely applied in many machinery industries
When the initial crank angle difference between inner crank web and outer crank web is set to ∆CA = 0, just as shown in Figure 10, the axis offset of crankshaft will impose a little effect on averaged torque output in a OPE diesel engine relative to the parameter of ∆CA
The crankshaft system with opposed piston layout has the possibility to counteract the forces along the cylinder axis direction, because the movement direction of both pistons always remains opposite, and reverse forces impose on each crankshaft journal by respective connecting rods
Summary
It is well known that the in-line or V type of IC engine has already occupied the majority of market share and widely applied in many machinery industries. As the time passing, for increasingly stricter emission regulations and higher fuel economy requirement, the conventional IC engine has suffered many new challenges from energy crisis and environmental pollution problems, because there is only a small margin to further enhance power performance but needs to maintain relatively lower fuel consumption and emission level based on present technologies. It becomes more urgent than ever to seek a technical breakthrough in IC engines. The crankshaft durability analysis is performed for the speed sweep based on measured data input in this paper
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