Friction Teardown Data From Motored Engine Tests on Light Duty Automotive Diesel Engines at Low Temperatures and Speeds

Abstract

Friction data have been acquired from motored engine tests on four designs of light duty automotive diesel engines. The engines were all four-cylinder designs with a swept capacity around two litres (1.8l-2.2l). These are typically used in the small and medium car sectors of the European market. The test programme was aligned to cold start and warm-up conditions. The data cover temperatures at the start of motoring of −20°C and above, and motoring speeds covering 200 rev/min – 1000 rev/min. Most tests were carried out using 10W/30 oil. The breakdowns separated piston assembly, crankshaft assembly, valve train and auxiliary component contributions to friction mean effective pressure (fmep), from −20°C upwards, under quasi-steady thermal conditions. Under these conditions, during warm-up the variation of engine fmep exhibits a simple power law dependence on oil viscosity evaluated at the current bulk oil temperature. The dependence of component contributions on oil viscosity has been examined. The empirical coefficients and functions used in the engine friction model developed by Patton, Nitschke and Heywood (SAE 890836) have been modified to give an improved fit to the low speed, low temperature test data, whilst limiting the effect on predictions for fully-warm conditions. The quality of the predictions is illustrated. The degree to which the effect of design detail can be predicted and the scope to reduce friction levels through design are discussed.

Real-time friction torque estimation on a diesel engine using the crankshaft speed fluctuation

“…To predict friction losses at cooler temperatures, a calibration of lubricant viscosity with temperature was added. A modified version of Patton's model was also developed by [20]. The models developed to describe the internal combustion engine cycle are generally divided into two main groups, depending on the physical basis on which the fundamental equations are established.…”

A New Approach to Mixed/Boundary Friction Prediction Using the Logistics Curve

“…The valve train is often considered, by many researchers, to be the engine component which is the major source of mixed/boundary lubrication in an engine [29][30][31][32][33]. Numerous researchers have measured (or predicted) valve train friction [34][35][36][37][38][39] and found it can be as high as 40% of total engine friction at low engine speeds for a fully warmed up engine, and this would primarily all be mixed/boundary friction. The proportion of valve train friction in most modern engines is likely to be lower (due to the use of lower weight materials, and softer springs, and also because many new vehicles use stop-start systems that switch the engine off when the vehicle is stationary so that there is much less engine idling than previously), but it is still anticipated that, for passenger cars, the valve train will be the main source of mixed/boundary lubrication in an engine.…”

Technoeconomic analysis of internal combustion engine – organic Rankine cycle systems for combined heat and power in energy-intensive buildings

“…These loss mechanisms consist of valve throttling losses, friction, heat transfer and mass leakage past the piston rings. Valve losses are modelled using 1-D compressible flow relations with a discharge coefficient [33], while friction losses are estimated based on measurements from motored diesel engines [34]. Heat transfer calculations are made using the complex Nusselt number correlation provided by Lekic [35].…”