Abstract
Automotive industries made a paradigm shift in selection of viscometrics of engine lubricant, from higher to lower viscosity grade, for improving fuel economy of vehicles. Engine fuel consumption is influenced by friction between the various engine components. Engine friction power (FP) of a direct injection diesel engine is calculated from the measured value of in-cylinder pressure signals at various operating conditions. For predicting FP, as a function of speed, load, and lubricant viscosity, a full factorial design of experiments (DOE) was formulated and an empirical correlation was developed. Response surface methodology (RSM) was used for analyzing the dominant parameters and their interactions, which influence engine friction power significantly. Predicted results of engine FP are in good agreement with measured values at all operating points. ANOVA and RSM analysis revealed that the significant parameters influencing engine FP are speed, load, viscosity, speed-load, and speed-viscosity. The effect of engine lubricant viscosity on friction power of a diesel engine was insignificant at low speed, whereas, at high speed, it played a vital role. The empirical relation developed for predicting FP is very useful in estimating engine friction power for various combinations of engine speeds, loads, and lubricant viscosity without running the engine.
Highlights
Engine friction study has been a topic of research for many years
The main objective of this paper is to develop a model to predict the engine friction power of a fired diesel engine based on significant factors and its interaction, using response surface methodology (RSM)
At the speed of 1400 rpm, it may be seen from Figures 8(a) and 9(a) that with the decrease in viscosity from 14.5 cSt. to 11 cSt. friction power reduces from 6–8 kW to 4–6 kW. This experimental study investigates some of the important facts about friction power affected by the engine operating variables and engine lubricant viscosity
Summary
Engine friction study has been a topic of research for many years. Some of the conventional methods like Morse test, PV diagram, Willans Line method, and motoring test for measuring friction of an engine are described in the literature [1]. It is widely accepted that PV diagram method yields more accurate results about engine friction. Total engine mechanical friction losses for a diesel engine were studied by Taylor [2] and Comfort [3]. It was highlighted that the majority of mechanical friction losses inside the engine emanated by piston ring assembly and bearings, which amounts to approximately 65% to 70% of the total mechanical friction losses. To achieve the better fuel efficiency, one must concentrate on reduction of these friction losses
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