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Transportation needs of society has been growing at a rapid rate and to a great extent dependent on crude oil derived fuels. The crude oil supply may fall short of demand has been clearly realized and future fuel scenarios are being studied. In this background, transport fuels and their effect on exhaust emission as well as greenhouse gases have become the driving force for their interactions with engine and emission control systems. In this paper, various transport fuel options to supplement/replace the existing fuel supply are discussed particularly considering the Indian Transport scenario.

In India, continuous efforts are being made to upgrade fuel quality and vehicle technology for meeting European emission norms. However, these efforts make a very little impact in improving the air quality due to exponential increase in the vehicle population and the poor quality of the Indian roads. The long-term strategy for meeting the requirement of huge road infrastructure and traffic management systems needs immediate attention. Studies have been conducted worldwide to study the effect of fuel quality and vehicle technology on fuel economy and emissions. However, the contribution of road quality, traffic management and driver training on reduction of vehicular emissions and improvement of fuel economy under Indian road conditions is still not established.

Hydrocarbon composition of fuel affects the deposit composition, its capacity to heat up the hot spots, and propensity of the fuel to preignition. Presently, fluidized catalytically cracked streams forms a large fraction of total gasoline pool in India and gasolines contain up to 50% olefins. About 60% of total gasoline in the country is consumed by the two wheeled vehicles powered mostly by 2-stroke engines. Preignition tendency of fuels with varying content of olefinic hydrocarbons was studied on a 2-stroke engine, during a 50 hour test. Preignition was indicated by sudden increase in combustion chamber surface temperature. Results showed a marked increase in preignition as the olefin content of gasoline increased above 20% by volume.

Injector nozzles of direct injection diesel engines (DI) of in-service vehicles showed one or more holes blocked and significant flow reduction even in nozzles with all the holes open. Coked nozzles from field gave measurable increase in smoke, carbonmonoxide (CO) emissions and specific fuel consumption (BSFC). Tests of 500 hour duration on a naturally aspirated DI diesel engine revealed hardly any significant nozzle coking particularly with the fuels containing total cycle oil (TCO). In some cases, an increase in flow rates in nozzles was observed for in-service vehicles as well as in 500 hour engine tests. In the long duration tests, statistically significant increase only in CO and reduction in NOx emissions were observed with a straight run diesel fuel and another fuel containing 20% TCO. Change in power, BSFC and HC emissions during 500 hour engine operation were not significant with any of the test fuels.

The influence of fuel characteristics on particulate emissions has been widely investigated. In this paper, the effect of different fuel properties on particulate emissions has been reviewed. The effect of fuel sulphur has been reported to have linear-relationship with the sulphate content of particulates. Combustion system, engine loading etc. were found to have weak contribution to the sulphate content variation. The results and analysis of various studies showed that the aromatic content had little influence on particulate emissions particularly in DI engines of modern design. The results from a number of investigations show that the key fuel property influencing particulate matter (PM) is the density.

Gasoline vapour losses from marketing operations are a major source of Volatile Organic Compounds (VOC) emission and a significant economic loss. Exposure to VOC can cause adverse health effects. VOC also lead to the formation of harmful ground level ozone. Gasoline vapour losses from retail outlets occur in two stages viz., vapour losses from the underground storage tank termed as Stage I and vapour losses during dispensing of fuel to the vehicles termed as Stage II. In India, there are currently only few Stage II vapour recovery systems in selected marketing outlets and no Stage I vapour recovery systems in place. Quantifying the extent of the gasoline losses would help in implementation of the vapour recovery systems.