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The diesel engine has for many decades now assumed a leading role in both the medium and medium-large transport sector due to their high efficiency and ability to produce high torque at low RPM. Furthermore, energy diversification and petroleum independence are also required by each country. In response to this, biodiesel is being considered as a promising solution due to its high calorific value and lubricity conventional petroleum diesel. However, commercial use of biodiesel has been limited because of some drawbacks including corrosivity, instability of fuel properties, higher viscosity, etc. Biodiesel are known for lower CO, HC and PM emissions. But, on the flip side they produce higher NOx emissions. The addition of alcohol to biodiesel diesel blend can help in reducing high NOx produced by the biodiesel while improving some physical fuel properties.

The growing energy demand and limited petroleum resources in the world have guided researchers towards the use of clean alternative fuels like alcohols for their better tendency to decrease the engine emissions. To comply with the future stringent emission standards, innovative diesel engine technology, exhaust gas after-treatment, and clean alternative fuels are required. The use of alcohols as a blending agent in diesel fuel is rising, because of its benefits like enrichment of oxygen, premixed low temperature combustion (LTC) and enhancement of the diffusive combustion phase. Several researchers have investigated the relationship between LTC operational range and cetane number. In a light-duty diesel engine working at high loads, a low-cetane fuel allowed a homogeneous lean mixture with improved NOx and smoke emissions joint to a good thermal efficiency.

The danger posed by climate change and the striving for securities of energy supply are issues high on the political agenda these days. Governments are putting strategic plans in motion to decrease primary energy use, take carbon out of fuels and facilitate modal shifts. Man's energy requirements are touching astronomical heights. The natural resources of the Earth can no longer cope with it as their rate of consumption far outruns their rate of regeneration. The automotive sector is without a doubt a chief contributor to this mayhem as fossil fuel resources are fast depleting. The harmful emissions from vehicles using these fuels are destroying our forests and contaminating our water bodies and even the air that we breathe. The need of the hour is to look not only for new alternative energy resources but also clean energy resources. Hydrogen is expected to be one of the most important fuels in the near future to meet the stringent emission norms.

The art and science of thrust vectoring technology has seen a gradual shift towards fluidic thrust vectoring techniques owing to the potential they have to greatly influence the aircraft propulsion systems. The prime motive of developing a fluidic thrust vectoring system has been to reduce the weight of the mechanical thrust vectoring system and to further simplify the configuration. Aircrafts using vectored thrust rely to a lesser extent on aerodynamic control surfaces such as ailerons or elevator to perform various maneuvers and turns than conventional-engine aircrafts and thus have a greater advantage in combat situations. Fluidic thrust vectoring systems manipulate the primary exhaust flow with a secondary air stream which is typically bled from the engine compressor or fan. This causes the compressor operating curve to shift from the optimum condition, allowing the optimization of engine performance. These systems make both pitch and yaw vectoring possible.

Increased demand and use of fossil fuels in transportation sector accompanied by the global oil crisis does not support sustainable development for the future generations to come. Not only that, today's on-road vehicles produce over one third of the CO and NOX present in our atmosphere and over twenty per cent of the global warming pollution. This air pollution carries significant risks for human health and the environment. Through clean vehicle and fuel technologies, it is possible to significantly reduce air pollution from our vehicles. In such a grim situation, Compressed Air Vehicles (CAV) powered by pressurized air stored in high pressure storage tanks seem to be one of the practical solutions available for tackling the fuel crisis and environment related issues.

Increased dependency on fossil fuels has led to its depletion as well as affected the environment adversely. Moreover, increasing crude oil prices is pressurizing vehicle manufacturers to invent new technology so as to increase fuel economy and at the same time to keep emissions under control. Hydrogen has gained popularity not just in terms of being an abundant alternative but also due to being a very clean propellant. In the present investigation, hydrogen boosting has been performed on an SI engine running on gasoline-methanol and ethanol-gasoline blends to determine the additional advantages of the same compared to pure gasoline operation. The engine selected for experimental analysis is a single cylinder, air cooled spark ignition engine that has been modified for hydrogen injection in the intake manifold prior to the port with the injection timing being held constant throughout the experiment.

In the past few decades, use of energy resources in industrial and transportation sector have reached to its peak resulting in depleting resources and environment squalor. Vegetable oils, which have properties comparable to diesel fuel, are considered promising alternative fuels for unmodified diesel engines. However, high viscosity of vegetable oils is a major challenge which could be reduced by blending with alcohols. The aim of the present study was to investigate the suitability of orange peel oil and n-butanol blends as an alternative fuel for CI engine. Various blends of butanol with orange peel oil were prepared on volumetric basis and named as B10OPO90 (10% n-butanol and 90% orange peel oil), B20OPO80 (20% n-butanol and 80% orange peel oil), B30OPO70 (30% n-butanol and 70% orange peel oil) and B40OPO60 (40% n-butanol and 60% orange peel oil). All blends were found homogenous and various physico-chemical properties were evaluated in accordance to relevant standards.

Diesel engines are employed particularly in the field of heavy transportation and agriculture on account of their higher thermal efficiency and durability. As these engines, are the backbones of contemporary global transportation and accounts a 30% of world's energy consumption, which is second highest after the industrial sector. Therefore, the fossil fuel consumption becomes the prime concern. Following the global energy crisis and the increasingly stringent emission norms, the search for alternative renewable fuels has intensified. Currently, biodiesel (BD) has been identified as the most attractive and practical choice to replace fossil fuel as the main source of energy, due to the similarity in the properties with conventional diesel. However, its development and application have been hindered by the high cost of required feedstock. Therefore, in recent years, researchers have been seeking the alternative sources of non-edible oil which are economical.

The interest of using alternative fuels in diesel engines has been accelerated exponentially due to a foreseen scarcity in world petroleum reserves, increase in the prices of the conventional fossil fuels and restrictions on exhaust emissions such as greenhouse gases from internal combustion (IC) engines initiated by environmental concerns. The constant trade-off between efficiency and emissions should be in proper balance with the conventional fuels in a fuel design process for future combustors. Unlike gasoline and diesel, alcohols act as oxygenated fuels. Adding alcohols to petroleum products allows the fuel to combust properly due to the presence of oxygen, which enhances premixed combustion phase, improves the diffusive combustion phase which increases the combustion efficiency and reduces air pollution. The higher activation energy of alcohols leads to better resistance to engine knocking that allows higher compression ratios and greater engine thermal efficiencies.

Primary energy sources can be divided into non-renewable and renewable. The over-exploration of non-renewable sources for energy availability imposes considerable impacts on the environment. Reducing the use of fossil fuels would significantly reduce the carbon dioxide emissions and other pollutants produced. The future drift for sustainable production of renewable energy is cautiously thoughtful for it has been increasingly understood that first generation biofuels, majorly produced from food crops that are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-edible feedstock such as microalgae, which potentially offers greatest opportunities in the longer term. Microalgae are considered a very promising feedstock for biodiesel production due to their very high yield and their no competition with food crops.

The commercial sources of energy such as fossil fuels and petroleum products are extensively used. These sources are finite and cause large scale degradation of environment. The increased pollution in urban areas is already causing serious sociological, ecological and economic implications. Diesel engines produce high torque at low rpm as compared to spark ignition engines due to which they are used in industrial, agricultural and transportation sector. Diesel fuel has higher HC, CO and PM emissions in comparison to biodiesel. This has drawn the attention of world towards the usage of biodiesel as an alternative fuel. Biodiesel has an advantage over diesel fuel because of its biodegradable and less toxic nature and superior lubrication properties. However, NOx emissions are compounded in case of biodiesel in CI engine. There has been concerns that biodiesel feedstock may compete with food supply in the long term.