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Combustion images are not simple to be obtained in conventional engines. Therefore, some experimental apparatus, such as a rapid compression machine (RCM), are useful to conduct this kind of study. Imaging techniques allow flame front propagation analysis, which is a very important parameter to understand engine performance, using different fuels and also to generate data to improve fuel modeling in engine simulation softwares. A RCM was adapted to operate in a spark ignition engine mode. It was used to obtain cylinder pressure measurements of gasoline-ethanol combustion synchronized with high-speed photos of flame propagation. Contour plots of the flame front profiles, assumed to be spherical, were used in successive frames to calculate the propagation speeds toward the cylinder walls. So, it was possible to correlate images, pressure curves and flame speeds of gasoline-ethanol blends.

Regarding fuels research and development, some preliminary studies - low cost and short time - can be conducted before the traditional engine tests - more expensive and time consuming. Therefore, experimental apparatus, such as a rapid compression machine (RCM) and specific methodologies, such as imaging techniques, are very useful in order to simulate engine combustion with simplicity, agility and flexibility, reducing development time and costs. Imaging techniques allow flame front propagation and ignition delay analysis, which are important parameters to understand fuel performance in engines and also to improve fuel modeling in engine simulation softwares. A RCM was adapted to operate in a spark ignition engine mode. It was used to obtain high-speed photos of flame propagation and ignition delay. Contour plots of the flame front profiles were obtained in successive frames to analyze the flame development with gasoline-ethanol blends.

Commercial gasoline is composed of hundreds of hydrocarbon components. Surrogate fuels that decrease the chemical and physical complexity of gasoline are being used to allow a better understanding of the processes involved in the interaction between fuels and internal combustion engines (ICEs). Based on previous published works about methodologies for fuel development using surrogate fuels, the aim of this paper is to present further results on the effect of individual components and fuel fractions on the combustion and performance parameters of spark ignition engines. SI engine dynamometer tests were conducted using ten mixtures of iso-octane, toluene, n-heptane and ethanol. Response surface models were statistically developed to analyze the interactions between fuel components, fuel properties and engine performance.

Fossil fuels and biofuels usage in internal combustion engines are the main source for vehicular propulsion. This justifies the intense worldwide research and development to comply with the challenges of increasing efficiency and emissions reduction. The modeling of commercial fuels and engine combustion processes presents great challenges. There is also the need to better understand how different fuel components interact and influence engine combustion and performance parameters. In previous works, components selection and engine dynamometer tests were done to identify representative surrogate fuels for commercial Brazilian gasoline. It was concluded that formulations with n-heptane, iso-octane, toluene and ethanol can be used to model oxygenated gasolines. Methodologies were implemented to evaluate the influence of the fuel components on fuel properties and several engine combustion and performance parameters.

Gasoline is a complex mixture that possesses a quasi-continuous spectrum of hydrocarbon constituents. Surrogate fuels that decrease the chemical and/or physical complexity of gasoline can be used to enhance the understanding of fundamental processes involved in the interaction between fuels and internal combustion engines (ICEs). The aim of this paper is to present methodologies for fuel development and show how surrogate fuels can be used to investigate the effect of individual components and fuel fractions on fuel properties and the performance of commercial engines. For this purpose, experiments were designed and SI engine dynamometer tests were conducted using ten mixtures of iso-octane, toluene, n-heptane and ethanol. Response surface models were statistically developed to analyze the interactions between fuel components, fuel properties and engine performance.

Experiments in engine test cells are under the influence of several parameters and types of equipment, which may impact the test results. Many variables of interest are derived from the combination of more than one quantity, increasing the results uncertainty of the final reported value. This paper describes a detailed procedure to calculate uncertainty of measurement of emission tests using a FTIR (Fourrier Transformed Infrared) emission analyzer. A Flex-Fuel engine using gasoline and ethanol was tested under different operating conditions on an engine dynamometer equipped with automation system. For each operating condition at least four different measurements were taken. The expanded uncertainty was calculated by the combination of Type A (due to repeatability) and Type B (due to calibration, sensor resolution and others).

Gasoline is a complex mixture, composed of hundreds of different hydrocarbons. Surrogate fuels decrease the complexity of gasoline and are being used to improve the understanding of internal combustion engines (ICEs) fundamental processes. Computational tools are largely used in ICE development and performance optimization using simple fuels, because it is still not possible to completely model a commercial gasoline. The kinetics and interactions among all the chemical constituents are not yet fully understood, and the computational cost is also prohibitive. There is a need to find suitable surrogate fuels, which can reproduce commercial fuels performance and emissions behavior, in order to develop improved models for fuel combustion in practical devices, such as homogeneous charge compression ignition (HCCI) and spark ignition (SI) engines. Representative surrogate fuels can also be used in fuel development processes.

Gasoline is composed of hundreds of components. The fuel properties can present a wide range of variation, depending on the formulation. Commercial fuel specifications differ from country to country, based on the features of each market. Also, fuels for some specific engine applications can differ widely from commercial fuels. For the next decades it is expected that the fossil fuels and bio-fuels usage in internal combustion engines remains to be the main source for vehicular propulsion. This justifies the intense worldwide research and development to comply with the challenges of increasing efficiency and emissions reduction. In this context the fuel can play an important role, mainly when there is the possibility to optimize fuel formulation, engine design and engine calibration for the desired application.