ABSTRACT. The increasing deployment of biodigesters for the treatment of waste on farms and the use of the biogas generated in the production of energy have highlighted the need for knowing the influence of this fuel on internal combustion engines. This study aimed to analyze the influence of filtrated biogas on lubricant oil contamination and degradation, as well as on engine wear and corrosion. Lubricant oil samples were collected every 75 engine operating hours (EOH) and then correlated between each other and with a sample of new oil, determining the elements present in the biogas that contribute to lubricant oil contamination and degradation, as well as lubricant oil performance in the course of EOH and engine wear. The results demonstrate that hydrogen sulfide affects the performance of the lubricant oil and engine wear. Among the metals, we observed that the copper concentration exceeded the maximum limit recommended in the literature. As for the additives, the variation in concentrations of magnesium impacted on lubricant performance. By monitoring lubricant oil quality were able to extend the engine oil change interval of this study by 50%, what resulted in a savings of 33.3% in the cost of lubricant per hour worked.Keywords: contaminants, biogas, biodigester, biomethane, corrosion.Análise da contaminação e degradação do óleo lubrificante e desgaste de um motor ottolizado alimentado por biogás RESUMO. A crescente implantação de biodigestores para tratamento de resíduos nas propriedades rurais e a utilização do biogás gerado na produção de energia mecânica evidenciaram a necessidade de conhecimento da influência de utilização deste combustível nos motores de combustão interna. Este trabalho teve como objetivo analisar a influência da utilização do biogás filtrado na contaminação e degradação do óleo lubrificante, desgaste e corrosão do motor. Amostras de óleo lubrificante foram coletadas a cada 75 hM (horas de funcionamento do motor), e após correlacionadas dentre elas e com uma amostra de óleo novo, determinando os elementos presentes no biogás que contribuem para a contaminação e degradação do óleo lubrificante, como também o desempenho do lubrificante no decorrer das hM e o desgaste do motor. Os resultados demostraram que o gás sulfídrico influencia no desempenho do óleo lubrificante e no desgaste do motor. Dentre os metais, foi identificado que a concentração de cobre excedeu o máximo recomendado pela literatura, e a elevação da sua concentração teve relação com a elevação de chumbo e estanho, principalmente após as 375 hM. Em relação aos aditivos, foi a variação das concentrações de magnésio que impactou no desempenho do lubrificante. Por meio do monitoramento da qualidade do lubrificante é possível estender o intervalo de troca de óleo do motor do presente estudo em 50%, resultando em uma economia de 33,3% no custo do lubrificante por hora trabalhada.

The objective of this research was to develop concepts, possibilities of occurrence, and ways to solve the vibratory phenomenon of power hop, which is quite common in tractors with auxiliary front-wheel drive or all-wheel drive, in particular conditions of field work. First, the phenomenon is defined, and context is given for the practical situations in which the phenomenon can occur. Subsequently, actions are proposed to solve and minimize the problems arising from power hop. The subject of this study has been insufficiently analyzed in the literature, with mentions (some detailed) in scientific articles and theses developed to diagnose and propose ways to solve the problem. Equally, there has been almost no mention of the problem in agricultural tractor operation manuals, despite the frequent occurrence of the phenomenon.

In a tractor, the transmission system transmits the power generated in the engine to the driving wheels, hydraulic systems, and power take-off (PTO). There are several types of transmission systems available in the Brazilian market ranging from the simplest to the most advanced. Therefore, the objective of this study was to verify the different types of transmission systems present in 228 models of agricultural tractors produced and marketed in Brazil during 2019. The tractor models were grouped based on the engine power and the transmission systems were classified as sliding, partially synchronized, synchronized, semi powershift, full powershift, and continuously variable transmission (CVT). According to this classification, it was found that most tractors belonged to Class III (51.5-73.5 kW) with 66 models in total. However, even with continuous modernization in this field and with tractors becoming increasingly independent from the operator, 66% of transmission systems are still mechanical. However, CVT systems, which are available only in tractors with an engine power above 117.7 kW, are expected to be equipped on less powerful tractors in the coming decades.

Partial fuel replacement strategies arising from fossil sources used in compression ignition engines involve mixtures of mineral Diesel oil, biodiesel and ethanol to minimize the gas emissions. In this study, experimental assessments were performed on a multi-cylinder, turbocharged aftercooler, compression-ignition, agricultural tractor engine provided with electronic injection management and an exhaust gas recirculation (EGR) gas treatment system. Diesel oil containing low (BS10 -10 ppm) and high sulfur concentrations (BS500 - 500 ppm) was utilized, with 10% of biodiesel as a constituent established by Brazilian legislation, in blends with 5, 10, 15 and 20% of the total volume, made up of anhydrous ethanol with additives. Thus, there were eight fuels blends and two reference conditions (without ethanol). The emissions of CO, HC, NOx and the HC+NOx gases were estimated, corresponding to the eight operating modes (M) of the ABNT NBR ISO 8178-4 standard. From the findings, it was evident that with the rise in the ethanol concentrations in the fuel blends there was a corresponding increasing in the CO, NOx and HC+NOx emissions. The HC, on the contrary, exhibited a pattern of higher emissions for the high-sulfur fuels (BS500) at low loads. No difference was observed for the NOx emissions at high loads. In the other operation modes, different behaviors were expressed for the BS10, which sometimes showed an increase, while at other times a reduction in the NOx emissions. Regarding the BS500, the NOx emission increased when the ethanol concentrations rose. As the specific emissions of the NOx were higher than those of the HC (in g.kW-1.h-1), the behavior exhibited by the HC+NOx showed similarity to that of the NOx. When the directly analysis of the operating modes was taken into consideration, the use of ethanol triggered an upswing in the emissions, exceeding the threshold of MAR-1 and EURO V standards.