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In the 80's, due to the oil crisis, natural gas (NG) began to be regarded as a fuel with great potential for replacing diesel in heavy duty vehicles. At that time, Petrobras, together with other companies, developed conversion kit technology for heavy duty diesel engines to run burning simultaneously diesel and NG, known as diesel gas. For several reasons, the trials were interrupted. In the late 90's and beginning of the 2000's, factors such as NG availability, expansion of NG distribution network; increase of NG converted light duty vehicle fleet, government interest in increasing NG's energy matrix share, all together made a scenario which stimulated new developments in diesel gas technology. The scenario changed in the last couple of years, with Brazilian NG demand reaching its offering, mainly due to thermoelectricity generation guarantee of supply. This makes the diesel gas technology more attractable than the NG dedicated technologies.

In the last years, world's general concern about climate changes and their effects on human life has strongly increased. Some countries, such as European Union members and the USA, are improving their legislations in order to limit vehicular CO2 emissions. To comply with these limits, new vehicle and fuel technologies are being developed in many places. Thus, the main goal of this paper is to present a comprehensive overview of some of these technologies for light-duty vehicles based on international published references and some experiences of Petrobras Research Center (CENPES). Also, this work addresses to some regulatory initiatives, such as new CO2 emission legislations and fuel economy labeling programs.

Due to worldwide concern regarding greenhouse gases emission, mainly CO₂, automakers are developing new technologies to reduce vehicles' fuel consumption. One of the most promising technologies, growing fast in USA, Japan and Europe is the Hybrid Electric Vehicles (HEVs). In the Brazilian Market, HEVs availability is still absent, which causes uncertainties about possible impacts caused by the introduction of this new vehicle technology in the big cities. However, as requirements of non-pollutant technologies arise, HEVs are expected to be available in Brazilian Market in the next years. Within this scenario, in 2002, aiming to evaluate the adequacy of Brazilian Gasolines blended with up to 25% v/v of Ethanol in HEV technology, Petrobras Research and Development Center (CENPES) purchased from USA a 2002 Toyota Prius and a 2002 Honda Insight. Since then, both HEVs are being tested at CENPES's Vehicle Test Laboratory (LEV).

In 2005, it was published a paper in Brazil reporting significant values of aldehydes emissions for some old Brazilian diesel SUVs (Sport Utility Vehicles). In 2008, PETROBRAS (Brazilian Oil Company) together with LACTEC (Institute of Technology for Development) decided to study methods for measuring aldehydes from diesel vehicles, including SUVs and heavy-duty engines. In 2008, National Environmental Council (CONAMA) published legislation 408/08, establishing that IBAMA (Brazilian National Environmental Institute) must provide a procedure for aldehyde measurement at the end of December 2010 and that engine manufacturers must report typical aldehyde emission values of diesel vehicles before the end of December 2012. A technical group was created in 2009 by the Brazilian Automotive Engineering Association (AEA) to discuss and elaborate a new method for aldehyde measurement in diesel vehicles and heavy-duty engines. The new procedure must be published before the end of 2010.

Heavy duty diesel engines are homologated for emissions using engine test dynamometers according to predefined emission cycles. In 2012, it was released in the Brazilian market the first diesel heavy duty vehicles with PROCONVE P7 technology (EURO V). The homologation tests include emission measurement according to stationary cycles (ESC) and also transient tests (ETC). For the ESC emission measurement it is possible to use a passive dynamometer, while the transient test requires an active dynamometer. Uncertainty of measurement is an important matter to get accurate emission data, but there are not many published papers about a method for its calculation related to diesel engine emissions. According to this scenario, this paper presents a method to calculate the uncertainty of measurement of legislated pollutants for diesel engines (CO, NOx, THC and particulate matter).

The development of new fuels involves several areas of an oil company and several tests, including vehicle emissions tests on chassis dynamometers and engine performance tests on engine bench laboratory. Particularly for diesel and blends of gasoline fuels, an important test is to evaluate the engine speed profile during the vehicle cold start. In this work, for engine speed profile analysis, it was developed a system to acquire data using the engine's flywheel ring gear information and the audio input of a standard notebook computer. It was also developed a specific software to analyze the acquired signals. The system is able to point out several important features of the engine start such as the starter motor beginning of operation, the maximum engine speed during the start time, the settling time and the engine idling speed. All of this information can be collected using a low cost set of instrumentation devices.

Natural gas (NG) produced in the north of Brazil (Amazon Forest) has low methane and high nitrogen and therefore does not meet current NG specifications for vehicular use, as established by ANP (National Petroleum Agency). This paper reports the steps for NG conversion kit adjustments and also the results and comparisons of vehicle performance, emissions and fuel economy tests on a chassis dynamometer. The vehicles were tested with different fuels like regular NG, Amazon Forest NG, gasoline and ethanol. Also reported on this paper is an overview of the Brazilian NG fleet, present and future emission legislation, fuel specification, new trends on NGV (Natural Gas Vehicle) market and conversion kit technologies.

Hydrogen is considered one of the cleanest solutions for sustainable mobility. This paper presents an overview of some of these applications, such as internal combustion engines, fuel cell application and also blends of hydrogen and natural gas. This paper addresses questions regarding hydrogen properties such as net heating value, flame speed, power density, range of flammability and ignition energy. Also, the paper will draw a comparison between H2 and fossil and biofuels, such as ethanol. Questions regarding storage conditions, emissions levels, Internal Combustion Engine (ICE) air/fuel ratio among others are expected to be covered as well.