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During the last decade the use of alternative fuels for diesel engine has received renewed attention. The interdependence and uncertainty of petroleum based fuel availability and environmental issues, most notably air pollution are among the principal forces behind the movement towards alternative sources of energy. The main pollutants from the conventional hydrocarbon fuels are unburned / partially burned hydrocarbon (UHC), carbon monoxide (CO), oxides of Nitrogen (NOx), smoke and particulate matter. These emissions are harmful to human, animal and plant life. Emissions from automobiles are currently a dominant source of air pollution representing 70 % of carbon monoxide, 41 % of oxides of Nitrogen (NOx), 38 % of hydrocarbon emissions globally. In addition 25 % of the man made CO2 emissions globally adds to the green house effect, which results in global warming. In the present investigation hydrogen is used in a diesel engine in the dual fuel mode using diesel as an ignition source.

Hydrogen is expected to be one of the most important fuel in the near future to solve greenhouse problem and to save conventional fuels. In this study, a Direct Injection (DI) diesel engine was tested for its performance and emissions in dual-fuel (Hydrogen-Diesel) mode operation. Hydrogen was injected into the intake port along with air, while diesel was injected directly inside the cylinder. Hydrogen injection timing and injection duration were varied for a wider range with constant injection timing of 23° Before Injection Top Dead Centre (BITDC) for diesel fuel. When hydrogen is used as a fuel along with diesel, emissions of Hydro Carbon (HC), Carbon monoxide (CO) and Oxides of Nitrogen (NOX) decrease without exhausting more amount of smoke. The maximum brake thermal efficiency obtained is about 30 % at full load for the optimized injection timing of 5° After Gas Exchange Top Dead Centre (AGTDC) and for an injection duration of 90° crank angle.

Diesel engines are the main prime movers for public transportation vehicles, stationary power generation units and for agricultural applications. Hence it is very important to find a best alternate fuel, which emits fewer pollutants into the atmosphere from diesel engines. In this regard hydrogen is receiving considerable attention, as an alternative source of energy to replace the rapidly depleting petroleum resources. Its clean burning characteristics provide a strong incentive to study its utilization as a possible alternate fuel. Hydrogen injection along with selective catalytic converter shows very attractive results both from the performance and emissions point of view. A maximum reduction in oxides of nitrogen (NOx) of 74% is achieved for a (ratio of flow rate of ammonia to the flow rate of NO) of 1.1 with a marginal reduction in efficiency. The reduction in both hydrocarbon (HC) and NOx emission is one of the major advantages of Selective Catalytic Reduction (SCR) system.

The internal combustion engines, have already, become an indispensable and integral part of our present day life style, particularly in the transportation and agricultural sectors. Unfortunately the survival of these engines has, of late, been threatened due to the problems of fuel crisis and environmental pollution. Therefore, to sustain the present growth rate of civilization, a non-depletable, clean fuel must be expeditiously sought. Hydrogen exactly caters to the specified needs. Hydrogen, even though “Renewable” and “clean burning”, does give rise to some undesirable combustion problems in an engine operation, such as backfire, pre-ignition, knocking and rapid rate of pressure rise. The present investigation compares the performance and emission characteristics of a DI diesel engine with gaseous Hydrogen as a fuel inducted by means of Carburation and Timed Port Injection (TPI) techniques along with diesel as a source of ignition.

Hydrogen is one of the most promising alternate fuels due to its clean burning characteristics and better performance as compared to fossil fuels. In addition to the need for finding effective solutions to the problem of air pollution from combustion processes, increasing pressure is being placed to find alternative fuel to replace the rapidly depleting petroleum fuels. Numerous research works have been carried out on using hydrogen as a fuel in Spark Ignition (SI) engine. However the major drawback of using hydrogen in a SI engine is the reduction in power output of the engine by about 30% in addition to problems like pre ignition, back fire and knocking at higher loads. Hence the use of hydrogen in a SI engine is limited.

Vehicular emissions contribute nearly two-third of the environmental pollution. The increasing usage of personal transportation and higher emissions from the tail pipe contribute significantly to the climate change. Though catalytic converters and other regulatory measures have brought down the emission levels, it is a serious concern about addressing the problems of depleting fossil fuel sources and the green house gas emissions. The effective use of ethanol either as a neat fuel or as a mixture with gasoline has proved technically feasible and environmentally acceptable. Electric Vehicle (EV) which is a Zero emission vehicle is yet to be accepted due to its poor drivability range. Hence Hybrid Electric Vehicles is emerging as an alternate solution that overcome the disadvantages of EV's and the existing prime movers can suitably be combined with the electric drive to produce optimal results.

Intensified search for alternative fuels is the main interest across the world due to the impact of fossil fuel crisis, ever increasing vehicle population and oil price and stringent emission norms. On the other hand, the disposal of waste tyres from automotive vehicles becomes complex. Apart from alternative biomass derived fuels like Ethanol, Methanol, Hydrogen, Vegetable oils etc, the new sources for alternative fuels are also appreciable. In this context, Pyrolysis of solid wastes is currently receiving renewed interest. The disposal of waste tyres can be simplified to some extent by Pyrolysis. In this paper, the properties of the pyrolysis oil derived from the waste automobile tyres were analysed and compared with the petroleum products and pure rubber pyrolysis oil. Also, Tyre pyrolysis oil-Diesel blends were used as alternate fuel in a four stroke Diesel Engine without any modification in the engine and the performance and emission characteristics have been studied.