Search

The connecting rod small-end bearing system is one of engine's rotating friction pairs under the most severe condition. Significant deformation, high temperature, and the coupling action of multi-bearing tribology and multi-body dynamics make the simulation challenging. This study develops a new tribo-dynamics model considering deformation and thermal effects for the small-end bearing system. A full-scale engine test is conducted, and the predicted severe wear position is consistent with the experimental one. Results show the axial uneven wear and temperature rise happens in the bearing lower surface after considering elastic deformation and thermal effects. The piston pin is decelerated to stop nearly and then accelerated by the friction torque during compression and work strokes that differs from the simplified rigid model. • A new tribo-dynamics model for engine small-end bearing considering elastic deformation and thermal effects is established. • The predicted wear position is consistent with the experimental one by a full-scale test. • The axial uneven wear and temperature distribution happen after bearing deformation and thermal effects are considered. [ABSTRACT FROM AUTHOR]

The hermetic rotary compressor's bearings, including the thrust bearing, the main and sub bearings, work together under high ambient pressure. The thrust bearing works under light axial loads, but sever wear is found, which may be related to the crankshaft's misalignment and deformation and the high ambient pressure. To investigate this phenomenon, a complete coupled journal-thrust bearing model is constructed. The bearing forces are calculated with the mixed elastohydrodynamic model under high boundary pressure. The effects of the deformations and ambient pressure on the bearing performance are investigated. Results show that ignoring the crankshaft deformation makes the simulation underestimate the thrust bearing wear, and the high ambient pressure is the leading cause of the thrust bearing wear. • A complete coupled journal-thrust bearing model is constructed considering 5° of freedom of the crankshaft. • A new method to calculate the deformation of shafts supported by journal bearings is introduced. • The effects of high ambient pressure on the thrust bearing wear are investigated. [ABSTRACT FROM AUTHOR]

Robust and accurate measurement techniques are essential to studying the piston-assembly friction of Internal Combustion (IC) engines. Based on the instantaneous Indicated Mean Effective Pressure (IMEP) method, this paper develops an improved measurement technique to evaluate the piston-assembly friction in engines. Wireless telemetry technology is employed in the measurement of connecting rod axial force, which greatly minimizes the engine modifications and enhances the measurement stability compared to the conventional wired way. The measurement system, which is composed of computer, data acquisition system, sampling trigger apparatus and sensors, is exploited with special attention given to the sampling synchronization of signal channels including cylinder pressure, connecting rod force and crank angle position. Engineering implementations are carried out on a four-stroke gasoline engine under motored condition. The measurement results are compared with numerical results from a newly developed numerical coupling model system, and it shows that the two agree well. In addition, the piston-assembly friction under different engine speeds and inlet lubricant temperatures are also measured, and analyses indicate that these results are in good correlation with the well-known Stribeck curve. This improved measurement technique provides an accurate and reliable option for the friction evaluation of piston-assembly components in engine designs. [ABSTRACT FROM AUTHOR]

• Measurement of piston-assembly friction under fired conditions is implemented. • The wireless IMEP method is applied to obtain the piston-assembly friction. • A measurement system is modified to meet the demands of an online test. • The lubrication and dynamic models are built for piston rings and piston skirt. • The measured results are compared with the numerical simulations. Reliable and accurate measurement of piston-assembly friction is urgently required in the field of internal combustion engines. With few modifications to the engine, an improved wireless instantaneous indicated mean effective pressure (IMEP) technique for measuring piston-assembly friction under fired conditions is first presented in this paper. The piston-assembly friction is obtained indirectly by measuring the cylinder pressure, the connecting rod force, the crank position and the engine speed under various conditions. A measurement system, mainly including a wireless rechargeable telemetry module, a data acquisition system and three typical sensors, is modified for an online test. After the in-situ measurement and the simulations, it is found that the simulation results generally coincide with the measured data. Though the current measurement technique still suffers from challenges in signal synchronization, noise control and system reliability, it can be applied for the direct performance evaluation of piston assembly in the future. [ABSTRACT FROM AUTHOR]