Análise da combustão de misturas diesel/biodiesel em um motor de uso agrícola turboalimentado e com gerenciamento eletrônico

Abstract

This study involves a combustion analysis, through the experimental performance evaluation of an agricultural engine with electronic management, in response to the variation of different proportions of soy biodiesel added to conventional diesel. The engine for tests is from the brand AGCO Power, model 44CWC3 Centurion T3, with 4,400 cm³ of displacement, with a turbocharger installed and using an electronic fuel injection management system. The study was based on the performance evaluation of the engine operating with biodiesel at the levels of 10% (B10), 20% (B20) and 30% (B30), at four control points that were established by the engine operation speed. For accomplishment out tests the engine was coupled to a dynamometer to control load level and the speed. The data referring to the work parameters were obtained through these tests, using a pressure sensor on the cylinder and a high resolution incremental encoder on the crankshaft. A data acquisition and processing system with a high acquisition rate was used and the data collected with this system were used in a zero-dimensional model, and with the application of this model, different combustion diagrams were generated for each speed and testing fuel. The analysis of the cylinder pressure and heat release rate diagrams allowed for the evaluation of combustion. These diagrams revealed that the rate of heat release has its value decreased, getting closer for all fuels, as the engine's operating speed rises, also showing that the premixed and diffusion combustion phases are clear for all fuels at 1800 and 2000 rpm conditions, while at 1400 and 1600 rpm most of the fuel is burned in the pre-mixed phase. Interestingly, a pre-main heat release event is perceived, which is called low-temperature heat release and which only occurs at high fuel injection pressures. Analyzing the burned mass fraction diagrams it is noticed that the slope of the burned mass fraction curve increases as the engine speed increases, for all the fuels used in the tests, indicating the increasing time necessary for combustion to complete. Interesting characteristics about the mechanism of combustion reactions were obtained when using these fuels, such as COV, imep and the duration of combustion. And it is concluded that biodiesel blends of up to 30% by volume to petroleum diesel can be used in agricultural engines with electronic fuel injection management, without any changes in the fuel injection control system.