Experimental investigations of heavy metal addition in lubricating oil and soot deposition in an EGR operated engine Shrawan Kumar Singh a , Avinash Kumar Agarwal b, * , Mukesh Sharma a a EEM Program, Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India b Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India Received 29 November 2004; accepted 4 May 2005 Available online 28 June 2005 Abstract Exhaust gas recirculation (EGR) is a technique, which is being used widely to reduce and control the NO x emissions from diesel engines. However, the use of EGR leads to rise in soot emission because of soot–NO x trade-off. This EGR generated soot leads to several other problems inside the engine like degradation of lubricating oil, enhanced engine wear etc. In the present study, an experi- mental investigation has been carried out to evaluate the effect of EGR on characteristics of lubricating oil with time of its usage. A two cylinder, air cooled, constant speed direct injection diesel engine of 9 kW rating was used for conducting the experiments. The experiments were conducted in two phases for a comparative study on the normally operated engine (i.e. without EGR) and the engine operated with EGR for 96 h in each phase. Lubricating oil samples were collected after every 24 h interval and were analysed for soot loading (total carbon content) and various metal addition due to wear of the engine. Higher metal contents were found in the lubricating oil drawn from the engine using EGR. Higher carbon deposits were also observed on vital parts of the engine oper- ating with EGR. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: EGR; Heavy metals; Soot; Engine wear; Lubricating oil 1. Introduction In recent years, popularity of diesel engines has in- creased due to its higher fuel economy and low mainte- nance cost. At the same time, regulatory emission norms around the world have been tightened in order to control the emissions from vehicles. For diesel en- gines, these norms particularly focus on emission of oxi- des of nitrogen (NO x ) and particulates. NO x is primary as well as secondary pollutant. These gases are toxic to human nervous system apart from being responsible for smog formation in the environment [1]. They react with the volatile hydrocarbons to form troposphere ozone, which is a major pollutant in smog. For control- ling the emission of NO x from diesel engines, various techniques have been tried e.g. retarded injection timing, injection of diluents in combustion chamber, selective catalytic reduction, NO x adsorbers, exhaust gas recircu- lation (EGR) etc. Most of these techniques have limita- tions in practical implementation on the engines. EGR has proved to be an effective method of reducing NO x emissions and is practically implemented in most diesel engines worldwide. In EGR system, part of exhaust gas is recirculated and mixed with air in the intake manifold, replacing an equal amount of fresh air. This reduces the availability of oxygen and increases the heat absorbing capacity of the exhaust gas and air mixture entering the combustion chamber, since specific heat of exhaust gas is significantly higher than air. The oxygen in air is par- tially displaced by CO 2 and water vapour of the exhaust 1359-4311/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2005.05.004 * Corresponding author. Fax: +91 512 259 7408. E-mail address: akag@iitk.ac.in (A.K. Agarwal). www.elsevier.com/locate/apthermeng Applied Thermal Engineering 26 (2006) 259–266