NUST Institutions Library Catalogue Search for 'an:"119876"'

Modeling Unsteady Squeeze Behavior Based Piston Lubrication In Engine Start-Up Conditions /

. 140p. ;

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Modeling the Non-Newtonian Engine Oil Behavior in 1st Compression Ring Lubrication /

. 114p. ; , Advancements in engine design have necessitated use of synthetic, multi-grade engine lubricants to reduce engine friction and wear and enhance its operational life. The modern multi-grade oils exhibit the non-Newtonian characteristics which are beneficial for an effective lubrication of the engines and industrial machinery. In the internal combustion engines, the piston ring assembly is a crucial component of the power plant. In the four stroke cycle the 1st compression ring is an important part of the piston ring pack which sustains the main combustion thrust directly. It is vulnerable to all forms of dynamic loads during the extreme and unusual engine operating conditions. When an engine starts up, the 1stcompression ring is most vulnerable to wear due to the absence of a fully established Elastohydrodynamic Lubricating (EHL) film. In this context, the viscoelastic behavior of anon Newtonian lubricant may contribute towards preventing wear of the interacting surfaces of the top ring and the cylinder liner. Role of oil behavior to minimize adhesive wear of piston skirt and liner surfaces during engine start up conditions under ideal conditions have yet to be properly modeled and thoroughly investigated. This calls for proper investigative research to model rheological behavior of non-Newtonian engine lubricants with particular focus on initial engine start up conditions. This research work will numerically model the hydrodynamic and Elastohydrodynamic Lubrication (EHL) of the 1st compression ring by considering the Newtonian and Non-Newtonian lubricant characteristics for comparative analysis. The secondary dynamics of the piston will be incorporated in the models at the different engine startup speeds, lubricant viscosities and radial clearances for optimum solutions. 30cm..

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Analysis of Existing Assembly Line for Manufacturing of Wheeled Security Vehicle (Mohafiz-II) in APC Factory and Propose a Re-configured Assembly Path /

By ATTIQUE, USMAN . , Assembly line of Wheeled Security Vehicle (MUHAFIZ) has been studied to analyze and evaluate the present system of manufacturing the vehicle with a view to balance the assembly line, eliminate wastes, reduce balance delay, increase production rate and improve line efficiency through a novel approach of coding into Tomlab(optimization software).To achieve optimized result, precedence among tasks was carefully determined. Next the grouping of tasks was done by assigning optimal number of operators with parallel consideration of space constraint. Tomlab code was then run on this carefully calculated grouping of tasks in line with precedence relations. Substantial increase in line efficiency with far better balanced station times were achieved by the adopted methodology. The approach can be applied at line balancing problems ranging from few to hundreds of work elements to achieve minimum cycle time with far less computational effort. SIMUL-8 has been used as simulation software to validate the optimization achieved through Tomlab since implementation was only possible after validating the results. By using SIMUL-8, visual model of the system/process can be drawn directly on the computer screen. Whole technique resulted in 62% reduction in assembly time, 70% reduction in idle time, 58% reduction in cycle time and 11% reduction in number of operators. Line efficiency was increased from 45% to 73%. 30cm..

Place Hold on Analysis of Existing Assembly Line for Manufacturing of Wheeled Security Vehicle (Mohafiz-II) in APC Factory and Propose a Re-configured Assembly Path /