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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 the present study, the effect of fuel properties in terms of cetane number, density, tail end volatility, sulphur content and aromatic content on particulate matter (PM), soluble organic fraction( SOF) of PM and gaseous CO, HC and NO, was studied. From different refinery streams, using blending correlation, a fuel matrix was formulated. Experiments were conducted on both direct injection (DI) and in-direct injection(IDI) engines using a steady state test cycle. The results of the study indicated that sulphur content and density were observed to be important from the point of view of particulate emissions. The increase in cetane number of the fuel reduced the gaseous emissions of HC, CO and NO,. Particulate matter was observed to be composed of 13-22% of soluble organic fraction (SOF). Both fuel and lubricant oil were seen to be contributing equally to the formation of SOF.

Two-dimensional Mie and LIEF techniques were applied to investigate the spray formation of a high pressure gasoline swirl injector in a constant volume chamber. The results obtained provide information on the propagation of liquid fuel and fuel vapor for different fuel pressures and ambient conditions. Spray parameters like tip penetration, cone angles and two new defined parameters describing the radial fuel distribution were used to quantify the fuel distributions measured. Simultaneous detection of liquid and vapor fuel was applied to study the influence of ambient temperature, injector temperature and ambient pressure on the evaporating spray.

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.

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.

In India, during 1992, two wheelers numbered around 17 millions compared to only 2.8 million passenger cars. Two wheelers are estimated to consume about 60% of the total gasoline annually. Very little information however, is available on the octane number requirement of two stroke engine two wheelers. In this study, octane number requirement (ONR) of 13 makes of two wheeled vehicles constituting the bulk of current production was measured using full boiling range gasolines as well as primary reference fuels. Knock intensity was measured by an instrument which measures and analyzes cylinder head vibrations in the frequency range of 5 to 12 kHz. Among different makes, ONR varied from 51.5 to 101 research octane number (RON) and 48-86 motor octane number (MON). ONR of the 2-stroke engine powered vehicles measured using primary reference fuels was found to be closer to MON of the full boiling range reference fuels.

Two-stroke engines are gaining importance as they provide smaller, simple machines having less moving parts than four stroke engines. In India the majority of them employ mixed lubrication systems. Lubrication requirements of two-stroke, air cooled engines are different than that of a four-stroke engines and need some specific characteristics in the oil formulation. Due to enviromental and lubricant conservation considerations, carburetors will run leaner and lower oil consumption is expected in the future. This situation may result in higher piston temperatures leading to increased tendency of ring sticking and piston seizure. With a view to conserve and eventually replace petroleum base stocks, alternate and renewable sources of lubricating oil are being considered. The vegetable oils, in general, provide good shear stability, miscibility with mineral oil and gasoline fuel, and easy biodegradability.

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.

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.

Analysis and evaluation of total and individual hydrocarbon components during the scavenging process is desirable for possible improvements in fuel consumptions and emissions for small two stroke gasoline engines. Experiments were carried out to analyse and understand the history of hydrocarbons near the exhaust port using a high speed electromagnetic gas sampling valve and the gas chromatography technique. The analysis showed that during the scavenging process initially the hydrocarbon concentration decreases, goes to a minimum level around bottom dead centre and increases again to its maximum level. The analysis of the composition of the individual hydrocarbons (C1 to C6) was carried out near the exhaust port and inside the cylinder. The composition of gases near the exhaust port predominantly consists of hydrocarbons having higher carbon numbers (C5 and above). The in-cylinder gases (during expansion) contain a higher proportion of hydrocarbons with lower carbon numbers.

Research on conversion of diesel engines for operation on methanol is, currently, of worldwide interest. Due to requirements of higher cyclic delivery of methanol and changes in fuel properties e.g. compressibility, wave propagation velocity, viscosity, surface tension, density etc., injection and atomization characteristics of methanol are expected to be different from diesel. From the equation of continuity and forces acting on the injection system elements and applying the principles of similarity, modifications required in the injection system were identified. Methanol injection and atomization characteristics were studied with a modified injection system and compared with those observed with diesel fuel. Methanol gave more favourable cyclic delivery characteristics than diesel. Laser diffraction technique was used to study time and space resolved drop size distribution in methanol and diesel sprays.