Lubrication analysis in the design of reciprocating machinery

This dissertation presents the results of comprehensive modeling of lubrication behavior of two major lubricated components in reciprocating machinery, i.e., journal bearings and piston ring pack. The inverse problem of dynamically loaded journal bearings is solved by using generalized Reynolds equation coupled with a complete mass conservative cavitation boundary conditions, described by Jacobsson-Floberg and Olsson (JFO) cavitation theory. The undertaken approach imposes the conservation of mass at the moving cavitation boundaries and within the cavitated zone. In the course of modeling, the new modified Thomas algorithms have been developed, which fully utilize zero terms in the solution matrix, and thus greatly reduce computational time. The developed, numerically efficient NO model was tested against the well-known mobility method. It was found that mobility method overestimates minimum film thickness and underestimates such bearing parameters as lubricant flow rate and power loss, which is still acceptable for most industrial applications. However, for the journal bearings with time-dependent feed pressure and predominant starvation effects, the mobility method can generate large, not acceptable errors.; A novel analytical model was developed to study piston ring pack lubrication phenomena. The proper treatment of cavitation was obtained by taking into account the complete mass conservation of the lubricant and introducing a strategy that defines a transition between the enclosed and open cavitation patterns. It was found that starvation and cavitation reduce the effective load region of the ring significantly. The lower rail of the oil control ring has a great effect on the performance of the complete ring pack. Consequently, any measures to enhance the lubrication in the rail result in a reduction of power loss and increase an upward oil transport of the complete ring pack.; The developed models and techniques for journal bearings and piston ring pack were verified in a case study of commercial air brake compressor, and based on comparison with widely published results.