Modeling and Simulation of 1𝑠���𝑡��� Compression Ring Dynamics in High Torque Low-Speed Diesel Engine

Abstract

In this modern age , engine design requires improved fuel economy, reduction of exhaust carbon emissions, enhanced recyclability, increased operating life and freedom of generating hazardous substances. To meet these demands engine design manufacturers make it confirm that piston ring design must minimize the friction loss due to direct dry contact and lubricant internal resistance, oil consumption loss due oil transport to combustion chamber side, wear loss due to direct contact between ring and liner. Before mentioned requirements can be achieved if ring dynamics is properly implemented within groove. Proper selection of groove side clearance decreases the gas blow-by effect. Implementation of fully flooded conditions at inlet and outlet of region ring-liner interface develops hydrodynamic lubrication to avoid adhesive wear and dry contact. In the absence of fully flooded lubrication within the ring-liner interface increases the chance of dry contact within ring-liner interface which results in sequential change in lubrication regimes of boundary, mixed, hydrodynamic in a diesel engine. This sequential change in lubrication regimes prone to friction loss, power loss, hence enhanced the wear phenomenon. Studies have shown that cylinder is not in perfect circular shape due to mechanical loadings, thermal distortion, wear, high combustion gas pressure and manufacturing error. Distorted cylinder liner results in lower magnitude of minimum oil film thickness in circumferential cylinder side, which results in enhanced oil consumption due to oil transport to combustion chamber side and ultimately decreases overall power. In this research work, ring dynamics in radial and axial direction, gas flow model and piston secondary motion was analyzed in high torque low speed diesel engine. Parametric study is conducted for clearance in radial direction, clearance in axial direction, engine speed and degree of distortion in non-circular cylinder liner. Results showed that gas flow rates are sensitive to ring groove clearances. It was also observed that piston tilt has crucial effects on oil film thickness and hydrodynamic pressure and ring hydrodynamic friction force. Results showed that parabolic ring running face profile is best suited for improved lubricating film thickness profile and performance. It was also observed that with increase in engine speed, film thickness profile improves and proper hydrodynamic regime developed. It was also noticed that oil film thickness and ring performance improved with an increase in magnitude of bore distortion. It was noticed that Increase in groove side clearance in axial direction enhance the gas blow-by effect from combustion side to crankcase side