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The secondary pollutants formation in the atmosphere, such as ozone (O3), comes from the reactions between volatile organic compounds (VOCs) and the photochemical oxidants in the presence of oxygen and nitrogen oxides (NOx). The understanding of VOCs reactivity emitted by light duty vehicles is very important to construct reactivity scales regarding ozone formation. In 2003, flex-fuel vehicles were released in the Brazilian market and nowadays, they represent over 50% of the total light duty vehicle fleet in the country. In 2007, new tailpipe emission limits were implemented for Non-Methane Hydrocarbons (NMHC), a group of pollutants included in VOCs. The new NMHC limit became a challenge to homologate some flex-fuel models, when fueled with ethanol. To deal with this issue, other legislation allowed the subtraction of the unburned ethanol emission from the NMHC value.

In-cylinder pressure measurements and indicating diagrams have proven to be a valuable research tool for the analysis of combustion in spark-ignition or compression-ignition engines. With the use of thermodynamic models, the rate of heat release and mass fraction burned curves are calculated, and from the latter the CA50 parameter (crank angle fifty), which is the angle in which 50% of the total fuel has been burned. The empirical process of obtaining the optimum start of combustion typically leads to a value of CA50 from 8° to 10° after top dead center. This paper attempts to numerically investigate which properties have an influence on this optimum CA50. A simple thermodynamic model was implemented which used the Wiebe function for the rate heat release. The CA50 was then evaluated for combustion duration in the base configuration and in a theoretical adiabatic engine.

In Brazilian market, Flex-Fuel vehicles represented over 85% of new light-duty vehicles sold in 2010. These vehicles can use gasoline blended with anhydrous ethanol (18 to 25% v/v), 100% of hydrous ethanol (contains from 6,2 to 7,4% w/w of water) or any blend of these fuels. Some studies regarding Flex-Fuel technology are being made in Brazil, but there are not many published information about fuel properties of different ethanol-gasoline blends. Also, it is important to better understand emissions of aldehydes, unburned ethanol and total hydrocarbons of different ethanol blends on gasoline. A Flex-Fuel engine, 1.4 l, 4 cylinders was tested on a dynamometer. A FTIR (Fourier Transform Infrared analyzer) bench measured aldehydes, unburned ethanol and total hydrocarbons. It was used Gasoline with 25% of anhydrous ethanol was used as a reference fuel (E25). E25 was blended with different hydrous ethanol contents such as 30% (H30), 50% (H50), 80% (H80) and 100% (H100).

In Brazilian market, Flex-Fuel vehicles represented over 90% of new light-duty vehicles sold in 2009. These vehicles can use gasoline blended with anhydrous ethanol (20 to 25% v/v), 100% of hydrous ethanol (contains from 6,2 to 7,4% w/w of water) or any blend of these fuels. An experimental investigation was done to study fuel consumption, emissions and in-cylinder pressure data of a Flex-Fuel Otto engine, 1.4 L, 4 cylinders. It used gasoline with 22% of anhydrous ethanol as a reference fuel (E22). E22 was blended with different hydrous ethanol contents such as 50% (H50) and 80% (H80), also a 100% hydrous ethanol H100) was used. The main fuel properties were analyzed as part of this work. To control the engine operation, a programmable ECU (Engine Control Unit) was used, allowing spark timing calibration either for maximum break torque (MBT) or to keep the engine below the knocking limit.

Uncertainty in measurements is a complex issue in the process of obtaining accurate results in a vehicle emission test. Based on the ISO GUM (Guide to the expression of uncertainty in measurement), a study was carried out to calculate the final uncertainty of measurement during a vehicle emission test following a feasible method that can be used in many laboratories. When applying the methods in other laboratories high uncertainty values may be obtained for some pollutants making the compliance with emission requirements a difficult task to attain. To reduce expanded uncertainty of measurement, it is necessary to estimate and reduce the influence of several variables on the final result, including type B (calibration certificates, reference materials, transducers and sensors, calculations) and type A (repeatability) uncertainty budgets.