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Homogeneous Charge Compression Ignition (HCCI) offers great promise for excellent fuel economy and extremely low emissions of NOx and PM. HCCI combustion lacks direct control on the "start of combustion" such as spark timing in SI engines and fuel injection timing in CI engines. Auto ignition of a homogeneous mixture is very sensitive to operating conditions of the engine. Even small variations of the load can change the timing from "too early" to "too late" combustion. Thus a fast combustion phasing control is required since it sets the performance limitation of the load control. Crank angle position for 50% heat release is used as combustion phasing feedback parameter. In this study, a dual-fuel approach is used to control combustion in a HCCI engine. This approach involves controlling the combustion heat release rate by adjusting fuel reactivity according to the conditions inside the cylinder. Two different octane fuels (methanol and n-heptane) are used for the study.

New combustion concepts developed in internal combustion engines such as homogeneous charge compression ignition (HCCI) have attracted serious attention due to the possibilities to simultaneously achieve higher efficiency and lower emissions, which will impact the environment positively. The HCCI combustion concept has potential of ultra-low NOX and particulate matter (PM) emission in comparison to a conventional gasoline or a diesel engine. Environmental Legislation Agencies are becoming increasingly concerned with particulate emissions from engines because the health and environmental effects of particulates emitted are now known and can be measured by sophisticated instruments. Particulate emissions from HCCI engines have been usually considered negligible, and the measurement of mass emission of PM from HCCI combustion systems shows their negligible contribution to PM mass. However some recent studies suggest that PM emissions from HCCI engines cannot be neglected.

Use of alternative fuels, and reduction of particulate and NOx emissions are major challenges for making diesel engines environmentally benign. Measures adopted for reducing gravimetric particulate emissions necessarily always do not reduce particulate number concentration, which is strongly related with adverse health effects. Current emission norms in some parts of the world limit particulate number concentration along with particulate mass. In this scenario, it becomes important to investigate effect of fuel injection parameters and fuel injection strategies such as pilot injections on particulate size-number distribution. A single cylinder research engine is used to evaluate the effect of different fuel injection strategies and injection timings (for pilot and main injections) on particulate size-number distribution and total particulate numbers.

Indian Railways have a fleet of high-horsepower diesel-electric locomotives rated at 2310 kW. These high horsepower diesel-electric locomotives have evolved from original design of 1940 kW locomotives. Adoption of new design turbochargers was essential for this upgrading efforts and a series of new design turbochargers were evaluated on the engine test-bed before their use on the diesel locomotives. The objective was to increase engine power output, improve fuel efficiency and limit thermal loading. Test-bed evaluation of different turbochargers was carried out for comparing five different turbochargers. Each turbocharger had different size nozzle ring, diffuser, turbine blade assembly, impeller and inducer. The compressor maps of turbochargers were used to plot the engine load lines and to calculate surge margins. The tests involved measuring critical parameters for various combinations of engine speed and load for every turbocharger.