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Engine components are exposed to various lubrication regimes such as hydrodynamic, elasto-hydrodynamic, boundary and mixed lubrication during engine operation. In each of these regimes, the factors which influence engine friction are different. Hydrodynamic friction is influenced by lubricant rheology, film thickness and sliding speed of interacting surfaces, whereas boundary and elasto-hydrodynamic friction is a function of surface properties like roughness and hardness and the type of friction modifier used in engine lubricant. So the principal factors which influence engine friction power are speed, load, surface topography of engine components, oil viscosity, oil temperature and type of friction modifiers used. Experimental studies on an off-highway diesel engine were conducted to investigate the effect of engine oil viscosity and engine operating conditions on engine friction power.

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.

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.

In India, two and three-wheelers constitute about 70% of the total in-use vehicle population and consume about 2/3rd of the total gasoline, rest of the gasoline being consumed primarily by the passenger cars. This paper presents the findings of an experimental study carried out on in-use gasoline vehicles, including two and three- wheelers and passenger cars. The gasoline fuels used for the study were equivalent to Euro-II, Euro-III and Euro-IV fuel quality specifications. The study analyzes the effect of improving the gasoline fuel quality on exhaust emissions from in-use vehicles.

Available information in the literature has been reviewed to understand the effect of gasoline composition (olefins, aromatics and benzene) on the exhaust emissions from two and four wheeled vehicles. Studies show that isolating the effect of an individual compositional characteristics may be difficult. Aromatics in the exhaust could be correlated with the aromatics in the fuel. The benzene and toluene fractions in the exhaust were sometimes more than in the fuel because of dealkylation of higher alkyl aromatics. The olefins fraction in the exhaust were also observed to be more than in the fuel. The olefin fraction was noted to be directly proportional to the sum of olefins and paraffins in the fuel, and, inversely proportional to the aromatics. Exhaust emissions of benzene may be due to benzene content in the fuel or benzene formation during combustion or over the catalytic converter due to dehydroalkylation of the alkyl benzene.

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.

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 are also discussed for identifying the effect of Aromatic content, volatility, cetane number, oxygenates etc.

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.

The matching of fuel injection characteristics with air motion and combustion chamber geometry is now widely modelled for more rigorous investigations of fuel-air, mixing in direct injection (DI) diesel engines to obtain improvements in fuel economy and emission characteristics. A number of studies have contributed in the understanding of fuel spray-air motion interaction in DI diesel engines. The genesis and characterization of swirl motion both during induction and compression is discussed as it influences spray growth, its trajectory and fuel-air mixing. Different aspects of fuel spray structure eg. break-up, drop-size distribution, spray penetration, air entrainment etc. are important. These spray development aspects are also briefly discussed in the paper. Different analytical approaches to model air entrainment in turbulent jet in the engine situation are summarized.

A mathematical model based on turbulent gas jet theory was used to study spray-swirl interaction in direct injection diesel engine. Vectorial approach was used to predict the momentum change in two directions (i) along the spray centre-line and (ii) normal to the centre-line. Effect of changes in air density and swirl velocity during compression was accounted for. Effect of different injection parameters viz. nozzle size, injection rates, duration of injection, shape of injection rate curve, location of injector in the cylinder head and spray angle was studied on spray penetration, spread, air entrainment and momentum ratio of spray to air etc. Initial rate of injection and mass averaged injection pressure play significant role in air-fuel mixing for spray injected from side of the cylinder, whereas the initial rate of injection dominates the mixing for central injection. Nozzle orifice size does affect fuel-air mixing but it is predominantly controlled by the injection pressure.