Viabilidade do aproveitamento do rejeito térmico de escape de motor à combustão interna de 4 tempos para geração de potência através de um ciclo de Rankine

Abstract

The present work aims to increase the performance of 4-stroke spark ignition internal combustion engines through the study of the feasibility use of thermal exhaust waste from fuel combustion thought the concentric tube heat exchanger with countercurrent flow for water heating to perform a Rankine power cycle, aiming to increase the thermodynamic efficiency of the engine through the use of saturated water vapor in the expansion stage of the thermodynamic cycle. This work is based on the fact that, on average, 30% of the energy from the burning of fuels in an internal combustion engine is wasted, which is too much for the study of methods to take advantage of, if not totally, engine performance, thus reducing fuel consumption. The heat wasted through the exhaust gas is transferred, through a heat exchanger of concentric tubes with countercurrent flow, to the preheating of water to be used for power generation through a Rankine cycle. Two hypotheses were raised, the first being the transfer of all the heat wasted in the exhaust gas absorbed by the water with different configurations between the diameters of the heat exchanger, which resulted in lengths greater than 10m of the pipe, and the second hypothesis that it consisted of the amount of heat transferred if the length of the tubes of the heat exchanger had the fixed length, obtaining a maximum value of 2.42kW of heat transferred. FU et al.(2012) obtains, for a Rankine cycle with overheating of the temperature of superheated steam, 2.5kW of absorbed heat for a maximum pressure of 3.07MPa for a 4-stroke engine that operates on a Otto cycle, at 3000rpm and has an internal volume of 2000cm³.