Study of Break-In Process and its Effects on Piston Skirt Lubrication in Internal Combustion Engines

Abstract

The piston skirt is one of the main contributors to the total mechanical loss in internal combustion engines. Usually, the skirt friction experiences a rapid change during the break-in period largely due to the wear of the machine marks or roughness against soft coatings. It is thus important to consider the effect of the change of the roughness for a realistic prediction of the piston skirt friction and system optimization. In this work, an existing model of piston skirt lubrication was improved with the consideration of a breaking in process for the most commonly used triangle machine marks. A new set of flow factors in the averaged Reynolds equation were analytically derived for the trapezoid shape formed after wear of the original triangle shape. A new asperity contact model was developed for the trapezoid shape. The calculation results reflect the trend of friction mean effective pressure (FMEP) during break-in in an engine test and showed quantitative agreement under the same amount of wear.

Application of a Wear Debris Detection System to Investigate Wear Phenomena during Running-In of a Gasoline Engine

“…This literature review shows that, overall, research has been mainly focused on the steady-state wear condition of the engine operation. Even though OEMs and R&D centers have developed extensive studies on the running-in stage [20][21][22][23][24][25][26][27], specific research on engine running-in and associated wear phenomena has been mainly dedicated to a specific tribo-pair, such as the piston-cylinder liner assembly [4,20,21,23,28,29], the cam-follower contact [30,31], and journal bearings [22,24,25,32]; and just a few studies have been focused on the running-in wear evaluation of the complete engine [26,33]. In practical applications in the industry, it is common to find running-in procedures based on experimental experience and of various duration times and operating conditions [34].…”

Tribological Properties of Tin-Zinc Hybrid Coating on Bronze in Lubricated Condition

“…It is well recognized that soft thin film coating, overlay, is effective means to reduce friction resistance in lubricated condition [5]. Polymer containing solid lubricants is one of the overlay materials and has been applied to piston skirt and journal bearing surfaces [6]. Tin (Sn) and zinc (Zn) are typical soft metals and the candidates as the overlay.…”

Coupling of heat transfer and lubrication of cylinder liner-piston skirt conjunction and low-friction temperature strategy of cylinder liner

“…In the study of the structure, dynamics and mechanics of piston skirt lubrication, some researchers did not consider the effect of heat (Lu et al, 2018;Meng et al, 2019;Zhao et al, 2016). With the increase in heat load of the internal combustion engine, some scholars considered the effect of heat in their research (Fang et al, 2017;Qasim et al, 2011;Molewyk et al, 2014;Hamid et al, 2018;Plumley et al, 2014;Ning et al, 2018).…”

“…Zhou et al (2019) established a three-dimensional transient heat transfer lubrication friction coupling mathematical model of the piston group cylinder liner system without consideration of the lube oil filling rate. In the past, the heat transfer boundary of piston land, groove and piston skirt was obtained by using a one-dimensional multilayer thermal resistance model with cooling water as the starting point (Liu et al , 2017; Lu et al , 2017; Yao and Qin, 2018). However, it is not suitable to calculate the piston temperature under different cylinder temperature distributions.…”