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The likely transition from today's conventional to future alternative fuels will be discussed. It will be shown that in the very long term renewable fuels might be the most promising road fuels with respect to low CO2 emissions. In the short and medium term, however, liquid alternative fuels will prevail being produced initially from natural gas and later increasingly from biomass. Methanol, Ethanol, GTL Hydrocarbons and other fuels are still under study since lowest WTW CO2 emissions and overall system costs are not yet clarified. The availability of alternative fuels in large quantities will depend on the costs for production and infra-structure, and not least of all, on the market benefits of the resulting fuel / power train systems in a holistic assessment. Cost trends for conventional and alternative fuels will be discussed.

The growing necessity for less carbon emission vehicles due to environmental issues and more rigid legislation rules encourages many automotive companies to develop low CO2 emission engines. This motivation leads Mercedes-Benz do Brazil to the development of a “dual-fuel” diesel engine for buses that works with diesel and CNG (Compressed Natural Gas) fuel. One of the challenges for the development of this kind of engine is the electric/electronic integration between the diesel engine ECU (Electronic Control Units) and the CNG system ECU that coordinates the engine gas injectors.

With the discovery of oil and gas in the pre-salt Santos and Campos basin, the supply of natural gas (NG) is expected to increase considerably, so the use of compressed natural gas (CNG) in city buses will be an important option for reducing the overall consumption of fossil diesel fuel and a reduction in operating costs in São Paulo and Rio de Janeiro Metropolitan Areas in Brazil. A vehicle with an engine that can run on pure diesel or diesel and CNG has advantage over a vehicle that works exclusively with CNG, because when there is no availability or the lack of CNG, the vehicle / engine operates with diesel only. Another benefit of this technology is the resale value in Brazil, because after the life cycle of use in theses two big cities, Urban Buses are sold country side to small cities where CNG is not available.

In view of limited crude oil resources, alternative fuels for internal combustion engines are currently being intensively researched. Synthetic fuels from natural gas offer a promising interim option before the development of CO2-neutral fuels. Up to a certain degree, these fuels can be tailored to the demands of modern engines, thus allowing a concurrent optimization of both the engine and the fuel. This paper summarizes investigations of a Gas-To-Liquid (GTL) diesel fuel in a modern, post-EURO 4 compliant diesel engine. The focus of the investigations was on power output, emissions performance and fuel economy, as well as acoustic performance, in comparison to a commercial EU diesel fuel. The engine investigations were accompanied by injection laboratory studies in order to assist in the performance analyses.

Although various legislation and regulations have been adopted to promote the use of alternative-fuel vehicles for curbing urban air pollution problems, there is a lack of systematic comparisons of emission control cost-effectiveness among various alternative-fuel vehicle types. In this paper, life-cycle emission reductions and life-cycle costs were estimated for passenger cars fueled with methanol, ethanol, liquified petroleum gas, compressed natural gas, and electricity. Vehicle emission estimates included both exhaust and evaporative emissions for air pollutants of hydrocarbon, carbon monoxide. nitrogen oxides, and air-toxic pollutants of benzene, formaldehyde, 1,3-butadiene, and acetaldehyde. Vehicle life-cycle cost estimates accounted for vehicle purchase prices, vehicle life, fuel costs, and vehicle maintenance costs.

The heavy-duty natural gas engine has been subject of growing interest as a feasible alternative for the reduction of pollution levels in urban centers, where currently diesel vehicles predominate. This paper summarizes the development of the Mercedes Benz compressed natural gas engine M366LAG, which reached competitive characteristics of Diesel engines, like fuel consumption, weight / power ratio and thermal loading, by matching the turbocharging technology with charge cooler and the concept of lean burn combustion. An oxidation catalyst was developed and emissions less than 50% of the EURO II limits were achieved. With 5,958 1 of displacement and 6 cylinders in line, the M366LAG provides a power of 170 kW @ 2600 min-1 and 720 Nm @ 1560 min-1 as maximum torque.

Engine manufacturers have explored many routes to reducing the emissions of harmful pollutants and conserving energy resources, including development of after treatment systems to reduce the concentration of pollutants in the engine exhaust, using alternative fuels, and using alternative fuels with after treatment systems. Liquefied petroleum gas (LPG) is one alternative fuel in use and this paper will discuss emission measurements for several LPG vehicles. Regulated emissions were measured for five school buses, one box truck, and two small buses over a cold start Urban Dynamometer Driving Schedule (CS_UDDS), the Urban Dynamometer Driving Schedule (UDDS), and the Central Business District (CBD) cycle. In general, there were no significant differences in the gas phase emissions between the UDDS and the CBD test cycles. For the CS-UDDS cycle the total hydrocarbons and non-methane hydrocarbon emissions are higher than they are from the UDDS cycle.

Steady-state, transient and dithering characteristics of emission conversion efficiencies of three-way catalysts on natural gas IC engine were investigated experimentally on a single-cylinder CFR engine test bench. Steady-state runs were conducted as references for specific engine emission levels and corresponding catalyst capacities. The steady-state data showed that conversion of HC will be the major problem since conversion of HC was effective only for a very narrow range of exhaust mixture. Unsteady exploration runs with both lean-to-rich and rich-to-lean transitions were conducted. These results were interpreted with a time scale analysis, according to which a qualitative oxygen storage model was proposed featuring the difference between oxygen absorption and desorption rates on the palladium catalysts.