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This paper aims to study the effect of piston skirt design parameters on the dynamic characteristics of a piston–cylinder contact.

This paper focuses on an analysis of the piston dynamic response. The oil-film pressure and the structural deformation were approximated, respectively, by finite difference method and finite element method.

The results show that the design parameters such as clearance, offset and the axial location of piston pin have a great influence on the dynamics of the piston and hence on the piston slap phenomenon and the frictional power loss.

All the results mainly focus on the slap noise of the engine and can be used in the piston–liner development at the development of the engine.

The analysis carried out in this study can provide guidance for manufacturers and researchers to design a piston for the development of engines.

Running conditions for pistons have become very severe because of the high combustion pressure and increase in piston temperature in the past 10 years. The precision of the model has a great effect on the power transmission, vibration noise emission. In this paper, the model was established with lubrication and dynamic governing equations, which were solved using finite element method coupled with Runge–Kutta method. A piston of an inline six-cylinder engine was studied, and some structural parameters were used to investigate its effect on the friction loss with lubrication and dynamic motion theory.

Based on the analyses, the effect of the friction load at the oil groove and thermal deformation of piston skirt were added to the model, and some useful information about the friction loss and dynamic characteristics were compared.

All the results will provide guidance for the development of the piston and reduction in the friction loss and wear.

The purpose of this paper is to evaluate the influence of temperature, load and sliding speed on wear and friction behavior of LM25/SiC composites in as-cast and heat-treated conditions.

The LM25/SiC aluminum matrix composites (AMCs) were prepared using the stir casting process. The wear tests were carried out using a pin-on-disc setup in dry condition. The three levels of each parameter, i.e. 100, 150 and 200°C operating temperature; 15, 25 and 35 N load; 0.8, 1.6 and 2.4 m/sec sliding speed, were considered for the investigation. ANOVA has been carried out to evaluate the percentage contribution of parameters. Scanning electron microscope analysis of worn surfaces has been carried out to understand the wear mechanism.

The wear and coefficient of friction (COF) increase with the increase in the temperature, load and sliding speed within a selected range for as-cast as well as heat-treated LM25/SiC AMCs. The mean values of wear and COF in heat-treated samples were found to be lower than as-cast samples for all cases. It was observed that the percentage wear increases significantly as temperature increases in as-cast AMCS. Mild to severe wear transition was observed at 150°C. In heat-treated AMCs, mild wear was observed irrespective of temperature. It was also observed that as the temperature increases, transition of wear mechanism from abrasive to adhesive (including delamination) occurs earlier in as-cast samples as compared to heat-treated samples.

There is a lack of data on combined effect of temperature, load and sliding speed on tribological aspects of as-cast and heat-treated LM25/SiC AMCs, limiting its applications. The present research work has addressed this gap.

THE I.C. engine is a special form of heat engine and, by its very nature, produces excess quantities of heat. Uncontrolled, this heat would soon lead to distortion and damage of mechanical components causing the overall working of the engine to be less efficient and eventually leading to complete breakdown. In the case of small engines, sufficient cooling can be achieved by increasing suitably the external area of the combustion chamber by finning and ensuring a suitable flow of air to these surfaces by ducting and powered fans. These methods are less suitable for larger engines as the extra heat produced would require extensive finning and fans—uneconomical in both power and space. For the majority of i.c. engines the accepted method of cooling is by the transfer of heat through the medium of a suitable fluid.

The lack of integrity of the piston machine combustion chamber manifests itself in leakages of the working fluid between the piston and the cylinder liner, at valves mounted in the cylinder head and between the head and the liner. An untight combustion chamber leads to decreased power output or efficiency of the engine, while leaks of a fluid may cause damage to many components of the chamber. The actual value of working chamber leak is a desired and essential piece of information for planning operations of a given machine.

This research paper describes causes and mechanisms of leakage from the working chamber of internal combustion engines. Besides, the paper outlines presently used methods and means of leak identification and states that their further development and improvements are needed. New methods and their applicability are presented.

The methods of leak identification have been divided into diagnostic and non-working machine leak identification methods. The need has been justified for the identification of leakage from the combustion chamber of a non-working machine and for using the leakage measure as the value of the cross-sectional area of the equivalent leak, defined as the sum of cross-section areas of all leaking paths. The analysis of possible developments of tightness assessment methods referring to the combustion chamber of a non-working machine consisted in modelling subsequent combustion chamber leaks as gas-filled tank leak, leak from another element of gas-filled tank and as a regulator of gas flow through a nozzle.

A measurement system was built allowing the measurement of pressure drop in a tank with the connected engine combustion chamber, which indicated the usefulness of the system for leakage measurement in units as defined in applicable standards. A pneumatic sensor was built for measuring the cross-sectional area of the equivalent leak of the combustion chamber connected to the sensor where the chamber functioned as a regulator of gas flow through the sensor nozzle. It has been shown that the sensor can be calibrated by means of reference leaks implemented as nozzles of specific diameters and lengths. The schematic diagram of a system for measuring the combustion chamber leakage and a diagram of a sensor for measuring the cross-sectional area of the equivalent leak of the combustion chamber leakage are presented. The results are given of tightness tests of a small one-cylinder combustion engine conducted by means of the set up measurement system and a pre-prototype pneumatic sensor. The two solutions proved to be practically useful.

The purpose of this paper is to analyze the processes of identification, emergence and filling of organizational knowledge gaps over an extended period of time, using the strategy in action perspective. Specifically, it aims to explore the nature and types of knowledge gaps, to capture their changes and to shed some light on the processes of filling knowledge gaps.

The study is based on two case studies and adopts a processual approach. It analyses 40 years of data collected using secondary sources and semi-structured interviews over a period of two years and identifies critical organizational events both in retrospect and real time.

The findings show that the two case study companies have identified a number of knowledge gaps over the 40 years period. Changes in the nature and type of knowledge gaps are identified and discussed in detail leading to a new taxonomy of organisational knowledge gaps. The findings report that knowledge gaps emerge due to changes in both exogenous and endogenous conditions over time. The filling of those gaps depends on a number of factors. Among these, the ability to make a distinction between “strategic” and “imposed” knowledge gaps and the ability to build absorptive capacity within a stipulated time frame have a predominant role.

The respondents were asked to look back into the history of their company using their memory of events to provide explanations surrounding critical organizational events. Since some of the respondents had not witnessed all of the events in question, their responses were at times based on hearsay. However, every effort was made to check the authenticity of the respondents ' explanations, such as using a range of sources and discussing the events with respondents at different hierarchical levels of the company.

This study provides examples of knowledge in practice and puts forward a new taxonomy of knowledge gaps which can help managers to deal with imposed and strategic knowledge requirements. Specifically, this study equips managers with tools on how to devise their knowledge strategy, how to identify their knowledge requirements and what are different sources (internal and external) which they can explore to fill those knowledge gaps.

The paper builds on the strategy in practice perspective, which stresses the need for further studies to link theoretical frameworks with practical solutions. In this respect, this paper attempts to make sense of organizational knowledge theory by applying it in real life business situations and by unearthing the concept and usage of knowledge gaps. The use of a retrospective processual approach to study changes in organizational knowledge requirements over time is another interesting aspect of this research. Finally, the paper provides a new taxonomy of organizational knowledge gaps.

Cavitation in piston-ring lubrication is studied as part of the performance of piston-ring assemblies. Cavitation degrades performance in engineering applications and its effect is that it alters the oil film pressure, generated at the converging-diverging wedge of the interface. Studies tried to shed light to the phenomenon of cavitation and compare it with cavities that have been identified in bearings. The paper aims to discuss this issue.

Lubricant formulations were used for parametric study of oil film thickness (OFT) and friction providing the OFT throughout the stroke and LIF for OFT point measurements. Lubricant formulation affects cavitation appearance and behaviour when fully developed.

Cavitation affects the ring load carrying capacity. Different forms of cavitation were identified and their shape and size (length and width) is dictated from reciprocating speed and viscosity of the lubricant. A clear picture is given from both techniques and friction results give quantifiable data in terms of the effect in wear and cavitation, depending on the lubricant properties.

Engine results are limited due to manufacturing difficulties of visualisation windows and oil starvation. Therefore, full stroke length sized windows were not an option and motoring tests were implemented due to materials limitations (adhesive and quartz windows). Lubricant manufacturer has to give data regarding the chemistry of the lubricants.

The contribution of cavitation in piston-ring lubrication OFT, friction measurements and lubricant parameters that try to shed light to the different forms of cavitation. A link between viscosity, cavitation, shear thinning properties, OFT and friction is given.

During running-in, the change in the honed cylinder liner surface alters the performance and efficiency of the piston ring-pack system. The present paper, thus, aims to investigate the surface topography and wear and friction evolution of a cylinder liner surface during the running-in tests on a reciprocating ring–liner tribometer under a mixed lubrication regime. After an initial period of rapid wear termed “running-in wear”, a relatively long-term steady-state surface topography can emerge. A numerical model is developed to predict the frictional performance of a piston ring-pack system at the initial and steady-state stages.

The liner surfaces are produced by slide honing (SH) and plateau honing (PH). The bearing area parameter (Rk family), commonly used in the automotive industry, is used to quantitatively characterize the surface topography change during the running-in process. A wear volume-sensitive surface roughness parameter, Rktot, is used to show the wear evolution.

The experimental results show that a slide-honed surface leads to reduced wear, and it reduces the costly running-in period compared to the plateau-honed surface. The simulation results show that running-in is a beneficial wear process that leads to a reduced friction mean effective pressure at the steady-state.

To simulate the mixed lubrication performance of a ring–liner system with non-Gaussian roughness, a one-dimensional homogenized mixed lubrication model was established. The real surface topography instead of its statistical properties is taken into account.

This paper aims to understand the influence of cylinder liner temperature on friction power loss of piston skirts and the synergistic effect of cylinder liner temperature on lubrication and heat transfer between piston skirt and cylinder liner.

A method to calculate the influence of cylinder liner temperature on piston skirt lubrication is proposed. The lubrication is calculated by considering the different temperature distribution of the cylinder liner and corresponding piston temperature calculated by a new multilayer thermal resistance model. This model uses the inner surface temperature of the cylinder liner as the starting point, and the starting temperature corresponding to different positions of the piston is calculated using the time integral average. Besides, the transient heat transfer of mixed lubrication is taken into account. Six temperature distribution schemes of cylinder liner are designed.

Six temperature distributions of cylinder liner are designed, and the maximum friction loss is reduced by 34.4% compared with the original engine. The increase in temperature in the second part of the cylinder liner will lead to an increase in friction power loss. The increase of temperature in the third part of the cylinder liner will lead to a decrease in friction power loss. The influence of temperature change in the third part of the cylinder liner on friction power loss is greater than that in the second part.

The influence of different temperature distribution of cylinder liner on the lubrication and friction of piston skirt cylinder liner connection was simulated.