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Mobility method is used to analyze the steady-state performance of crankshaft and connecting rod bearings which are subjected to loads whose magnitude and direction both vary in time. The steady-state characteristics include journal center orbit, minimum film thickness, maximum film pressure, effective temperature, flow through the bearing, etc. To extract the stiffness and damping coefficients over the load cycle, linear analysis method based on a short-bearing approximation is employed. In addition, the oil flow through the main and connecting rod bearings is investigated. Sufficient lubrication conditions for these bearings are discussed. This combined analysis is supported by numerical simulations. The case studies are based on AlliedSignal's two-cylinder truck air brake compressor, TU-FLO 550, which illustrate the entire approach.

Lubricating oil consumption (LOC) is a direct source of hydrocarbon and particulate emissions from internal combustion engines. LOC also inhibits the lifetime of exhaust aftertreatment system components, preventing their ability to effectively filter out other harmful emissions. Due to its influence on piston ring- bore conformability, bore distortion is arguably the most critical parameter for engine designers to consider in prevention of LOC. Bore distortion also has a significant influence on the contact forces between the piston ring and cylinder wall, which determine the wear rate of the ring and cylinder wall and can cause durability issues. Two drivers of bore distortion: thermal expansion and head bolt stresses, are routinely considered in conformability and contact analyses. Separately, bore distortion/vibration due to piston impact and combustion/cylinder pressures has been previously analyzed in wet liner engines for coolant cavitation and noise considerations.

Internal combustion (IC) engines still power most of the vehicles on road and will likely to remain so in the near future, especially for heavy duty applications in which electrification is typically more challenging. Therefore, continued improvements on IC engines in terms of efficiency and longevity are necessary for a more sustainable transportation sector. Two important design objectives for heavy duty engines with wet liners are to reduce friction loss and to lower the risks of cavitation damages, both of which can be greatly influenced by the piston-liner clearance and the design of the piston skirt. However, engine design optimization is difficult due to the nonlinear interactions between the key design variables and the design objectives, as well as the multi-physics and multi-scale nature of the mechanisms that are relevant to the design objectives.