A mixed-lubrication model considering the oil supply was developed. The elastoplastic model was applied in the asperity contact simulation. The oil-film thickness at the ring-cylinder liner interface was determined using a mass conservation algorithm. The modeling results were compared with experimental results for verification on a reciprocating wear tester. It is found that, under the fully flooded condition, the results of the Greenwood-Trip model and the current model in the middle of the stroke are in accordance with the experimental results, but the results of the current model at the ends of the stroke are closer to the experimental results than the Greenwood-Trip model results are. Under the starved-lubrication condition, the friction coefficient of the current method is closer to the experimental result than that of the Greenwood-Trip model in the entire stroke. Therefore, the model developed in this study is appropriate for mixed lubrication under the fully flooded condition and the starved-lubrication condition. Furthermore, the model was applied to the ring pack of a diesel engine to study the effect of the oil supply on the tribological performance. The results show that the frictional forces under the 1 mm oil supply condition are far larger than those under the sufficient oil supply condition in the middle of the stroke, and so the increase in the frictional force may be used to identify scuffing failure in future studies if the relationships between the frictional forces and the measured vibration signals of the engine are obtained.

No abstract

No abstract

No abstract

No abstract

No abstract

In this article, a coupling model of shafting torsional vibration with advanced injection angle is proposed to study the effect of advanced injection angle on shaft torsional vibration. Using Simulink, a model shaft system of a 4190ZL_C medium-speed diesel engine is created to study the effect. The proposed coupling model, the traditional simulation method and the test are conducted on the torsional vibration of the 4190ZL_C medium-speed diesel engine, separately. The results show that the spectrum from the coupling vibration model is more abundant than from the traditional vibration model. Hence, considering the effect of advanced injection angle on shaft torsional vibration, the proposed coupling model can improve the modeling accuracy of shaft torsional vibration. It provides a new approach in engine design.

In this article, a mixed lubrication model considering the oil supply quantity and a friction model under dry running condition were developed, in which an elasto-plastic contact model was employed in calculation of asperity contact forces and friction forces instead of the assumption of pure elastic contact. This model was verified to be suitable for calculating the friction forces of piston ring under different conditions on a reciprocating wear tester. The friction forces of piston ring pack were considered as an excitation source to calculate the crankshaft torsional vibration besides the exciting torques of gas pressure in the combustion chamber and inertia forces of reciprocation components. Furthermore, an experiment on a refitted single-cylinder air compressor was conducted to validate the change rule of torsional amplitudes under normal and scuffing failure conditions. The results showed that the friction forces between piston rings and cylinder liner in the mid-strokes under starved lubrication and dry running conditions increase obviously compared with those under fully flooded lubrication condition. It is reasonable to ignore the exciting torques due to friction forces of piston ring pack for calculating crankshaft torsional vibration under normal condition, and the torsional amplitudes at 2.0 order frequency increase obviously under slight and serious scuffing failure conditions. The result of experiment on a refitted single-cylinder air compressor also agrees with the above conclusion about torsional vibration. So, the change in torsional amplitude at 2.0 order frequency can be used as a referenced rule to identify scuffing failure for diesel engine through analyzing the signals of torsional vibration.