Investigations of Piston Ring Pack and Skirt Contributions to Motored Engine Friction

Abstract

An experimental study has been carried out to examine the influence of ring tan load and piston skirt modifications on piston assembly friction under motored engine conditions for initial temperatures of -20, 0 and 30 o C and motoring speeds within the range 400 to 2000 rev/min. The study has been carried out using the block, crankshaft and pistons of a 2.4l, 4 cylinder diesel engine with a bore and stroke of 89.9mm and 94.6mm respectively. The pistons examined are typical of current designs for light duty diesels. A range of ring pack and piston skirt modifications have been tested, in each case as part of a complete piston assembly. The first changes produced reductions in fmep of between 5% and 38%. The reduction was due to improved skirt and ring pack designs in equal measure, each giving improvements of up to 20%. From this baseline eliminating the tan load of the piston rings was projected to give a further reduction in fmep of between 10% and 20%. Increasing the piston diametric clearances by close to the difference between minimum and maximum grade clearance gave smaller improvements of between 2% and 10% relative to the baseline, and reducing skirt roughness to perfectly smooth gave a projected reduction of typically 4%, and more at low oil viscosities.

A Modified Oil Lubrication System with Flow Control to Reduce Crankshaft Bearing Friction in a Litre 4 Cylinder Diesel Engine

“…Tear-down friction studies of diesel engines show that the piston assembly and interaction with the liner is the largest contributor to friction losses, followed by the crankshaft assembly and the valve train [1]. Friction reduction in power cylinders has received considerable attention [4,5] as have the development of low viscosity oils [6] and improvements in engine thermal management designed to reduce the penalty associated with higher friction during cold engine operation [7]. The higher friction is largely attributable to higher values of oil viscosity at low temperatures, and various routes to accelerate the rate of rise of bulk oil temperature after cold start-up have been explored.…”

Effect of Non-Newtonian Effect of Lubricant on the Lubrication Performance of Piston Ring-Cylinder Liner Components for Diesel Enginee

“…TIAN [7][8] and the research impact of the dynamics of piston and piston ring set on the effect of friction and lubrication. Shayler [9], Felter [10], Livanos [11], Chong [12], Smith [13], Avan [14] have obtained some research findings on the friction pair of cylinder liner and piston ring. KONG LingJia [15], et al have taken the influence of air leakage from a piston ring to the lubrication of the piston ring into consideration; LIU Kun [16], etc.…”