Abstract
Ever since the establishment of the California Air Resources Board (CARB) in 1968 and Environmental Protection Agency (EPA) in 1970, significant strides have been made in diesel engine emission control technology. The diesel emission control is being achieved using strategies involving in-situ and after-treatment techniques and even with their effective combinations. Among these techniques, recirculation of the exhaust gases back to the engine inlet is an in-situ approach for Nitrogen Oxides (NOx) control. Moreover, exhaust gas recirculation (EGR) has been used for controlling the onset of combustion process. In the current review, the importance of EGR for advanced diesel combustion like homogeneous charge compression ignition (HCCI) or low-temperature combustion (LTC) system and the requirement of EGR with the use of alternate fuels are discussed. In order to facilitate better understanding, the adverse effects of EGR, the impact of EGR on diesel engine wear and lube oil deterioration is also highlighted.
1. Introduction
Over the last five decades, the vehicle population across the globe has grown significantly. The concern over vehicular pollution increased steadily after 1960s Los Angeles episode. It is wellknown that vehicular emissions vary with engine type, operating conditions and fuel utilized, and all these aspects need to be addressed simultaneously for their abatement. The severity of engine pollutant depends on their concentration and exposure time and severely affects human health. Owing to inherent fuel economy advantage, diesel engines have made inroads into automotive applications beside their usual stationary domain. However, the diesel fuel operated vehicles are the major source of NOx and particulate emissions and responsible for the deterioration of ambient air quality. Many countries like Brazil, China, Sri Lanka, Denmark and Paris are in the process of eliminating diesel vehicles and enforcing heavy taxes and levies on such vehicles. Recently, Indian government banned the registration of dieselrun private cars with capacity of 2000 CC and above in certain cities [1].
