Dimensionamento e avaliação de um sistema de escapamento de motor de combustão interna ciclo-Otto

Abstract

The present work refers to the study and analysis of the exhaust system dimensioning of an internal combustion engine with the engine initially operating with the original factory system and, later, with the new sized system. Based on the literature review on the subject, was used a sizing method proposed in the literature for the exhaust system of internal combustion engines. The sizing was applied to an engine naturally aspirated and carburated, equipping a chevrolet vehicle, model "C10", six cylinders in line and with a volumetric displacement of 4100 cm³. The idea was to replace the original engine discharge system based on a design of short tubes to have less space, with the pipes discharging the combustion gases in a gallery (collector). The replacement of such a system culminated in the manufacture of an exhaust consisting of individual (separated) tubes, more elongated, with smooth curves and joined three to three to connect at two discharge pipes. This favors the gaseous discharge of into engines with large overlaps, such in as six-cylinder engines. This issue is of great importance in the automotive industry, where it is increasingly seeking to increase the efficiency of engines. After the development of the calculations, a prototype was built in a company specialized in the field of exhausts. The objective was to verify the influence of the new discharge on torque and power measured directly on the wheels, using specific equipment for the analyses, such as the chassis dynamometer, which allows the simulation of more real operating conditions for comparison of results. Another instrument used for the development of the work was a manometer to evaluate the backpressure generated in the exhaust. The results obtained for the two conditions were compared to verify the contribution of the new sized exhaust system. The main results showed that the sized exhaust provided an increase in power compared to the original engine by 6.7%, i.e. increasing peak power from 103.73 HP (77.4 kW) to 110.67 HP (82.6 kW), while peak torque decreased from 254.04 N·m to 250.58 N·m. In addition, internal pressure in exhaust was decreased by 0.12 bar, preventing the motor from operating with the undesirable effect of braking by the backpressure generated in it. The results achieved in the tests were very promising, showing that sized exhaust obtained the expected results in the rotation range from 3000 to 4000 RPM, with increased power availability and reduction in pressure in the exhaust pipes (sic).