Efeito do biodiesel no bico injetor e na emissão de material particulado em motor do ciclo diesel

摘要

A nozzle is a very important component of a diesel engine injection system. It is responsible for the atomization of the fuel for efficient combustion and low pollutant emissions levels, which directly affects the environment and the human cardiovascular system. The standards of vehicle emissions set by the environmental legislation are increasingly stringent, as PROCONVE P7 in Brazil and Euro 6, in the European Union. They restrict the size of the particulate material and NOx emissions levels. The main objective of this thesis is to investigate and understand the wear mechanisms of brittle and ductile materials which undergo the action of an atomizer type common rail, erosion, cavitation, adherence, adhesion, and corrosion. A systematic method was developed for evaluating diesel biofuels with additives or obtained in gas stations, its process of atomization and its interaction with two structural materials: a chemically active, electrolytic copper, and a chemically inert, silicon oxide glass. A test rig equipped with a high-pressure atomizing chamber (HPSC), a carrier device for ductile and brittle materials and a CCD camera were used to evaluate the atomization process. In this test rig there were tested three fluids: Ultrasene (standard fluid of the fluid nozzle testing machine TM 507), B6, B6 additivated with surfactants plus water and additivated B6 with surfactants, water and glycerin. A dynamometer test rig was used for testing a stationary diesel single cylinder engine, brand Branco, model BD5.0, four-stroke, 5 cv diesel, with the aforementioned fuels. In the end of 150 hours of each test fuel, the engine was disassembled, visually inspected and its main parts were replaced - piston, piston rings, pin, connecting rod, bearings, valves, seals, gaskets and the nozzle repair were replaced. The particulate matter coming from the combustion process, was collected by a device developed in the Tribology Study Group and Structural Integrity (GET-UFRN). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were used to assess the damage resulting from the materials submitted to atomization and the particulate matter from the exhaust of combustion after 20 and 150 hours. Each fluid was atomized by a new nozzle and the spray atomized by each nozzle (the new one and after testing) was recorded using a CCD camera in a 10 kfps resolution. Posteriorly, those nozzles were analyzed by SEM and EDS. It was observed metal particles ranging in size from 0.5 to 50.0 μm2. Evidences of wear by adherence, adhesion, corrosion, erosion and cavitation were observed on inject nozzle because the fuel atomization processes.