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The work focuses on studying ethanol spray behavior injected directly inside a spark ignited internal combustion engine in the compression stroke. An experimental procedure for measuring spray penetration and spray overall cone angle produced by a multi-hole direct injector was developed by means of computational codes written in Matlab environment for working with images of spray injections and to acquire calculated results in an automatic way. The shadowgraph technique with back continuous illumination associated with a high speed recording image process was used in a single cylinder optical research engine for acquiring images of Brazilian ethanol fuel injected at 120° before the top dead center of compression stroke. The process of spray injections occurred with engine speeds of 1000 rpm, 2000 rpm and 3000 rpm. The results showed that spray penetrations decrease and spray cone angle increase when the engine speed is raised.

A multi-hole direct injection injector was studied by means of image analysis. Methodologies based on an automatic process of cone angle measurement and edge detection were applied for the spray images generated by a 100 bar injection pressure discharged into a pressurized rigid chamber. A criterion based on pixel values was taken to localize the spray edges as angular coordinates and also with x and y position data. The high pixel values were associated with liquid phase while the low pixel values were associated to its absence. Computational codes written in MATLAB environment were used to analyze the numerical matrices associated to the images. Using the written MATLAB codes, a comparison of the effect of atmospheric back pressure, inside the chamber, on the spray pattern, cone angle and spray penetration were evaluated. The chamber was pressurized with 2.5, 5.0, 7.5 and 10 bar of back pressure. The tested fluid injected was EXXSOL D60 for simulating ethanol fuel behavior.

The growing demand for more efficient and less polluting engines has lead the scientific community to further develop the road map engine technologies, including direct fuel injection. Direct injection research demands the investigation of spray formation and its characteristics. The present work performs the characterization of the macroscopic parameters of ethanol sprays (E100) produced with a fuel gauge pressure of 80 bar and gauge back pressures of 0, 5 and 10 bar. The sprays analysis was performed using high speed filming by means of Shadowgraph technique. Computational routines of matrix analysis were applied to measure the spray cone angles, penetration and penetration rate. The spray visualization demanded an experimental apparatus composed of a pressurized cylinder with nitrogen, a fuel tank as pressure vessel, an injection driver equipped with a peak and hold module controlled by a MoteC M84, a Phantom V7.3 high speed camera and LEDs for illumination.

The transportation sector is responsible for 24% of CO2 global emissions and great effort has been made by the scientific community to replace the use of fossil fuels with renewables. Brazil has committed to implement all obligations provided in COP26 seeking carbon neutrality in the set of economic activities. In this regard, Brazil has agreed in reducing GHG by 50% until 2030. Flexfuel technology was introduced in the Brazilian market decreasing fuel conversion efficiency due to the use of an intermediary compression ratio value, lower in comparison with the best value for engines exclusively fueled with ethanol and higher for gasoline. According to data published by INMETRO, flexfuel engine consumption has increased around 6%. Many European countries have been pointing to the electrification of the light vehicle as a solution to mitigate GHG, which is neither best nor a feasible solution for the future of Brazilian mobility.

Direct inject engine provides increased possibilities to work with injection strategies in order to achieve better efficiency. Some ethanol properties such as the higher octane number, the latent heat of vaporization as well as the faster laminar speed made ethanol one of the most promising biofuels. These properties help to achieve knock suppression in a SI engine and therefore allow the use of higher volumetric compression ratio, which is one of the key factors in efficiency improvement. Several studies have showed ethanol as a way to reduce soot formation in direct injection engines as the oxygen molecule reduces the locally fuel-rich region. The use of ethanol contributes significantly to the reduction of total hydrocarbon (THC) and carbon monoxide (CO).

In the actual context, Researchers are making efforts for becoming mobility more sustainable. Whithin it context, the strategy of direct injection of renewable ethanol fuel in spark ignition engines is an interesting alternative for substitution of fossil fuels. In Brazil, the majory part of ethanol fuel production is provenient of sugar cane that has the potential to absorb great quantity of carbon dioxide through the photosynthesis process. The focus of this study was to create a very low computational cost methodology for evaluating the shape of sprays produced by an inwardly opening pressure-swirl injector. The referred injector is to be used in four stroke spark ignition engines for delivering fuel directly inside the combustion chamber. The spray geometry was then predicted by numerical calculations of single droplets trajectories in a purely lagrangian approach. The working fluid injected considered was EXXSOL D60.