Análise termodinâmica de um módulo compacto baseado no ciclo Stirling para a recuperação da energia dos gases de escape de um motor de combustão interna

Abstract

In the process of generating mechanical work with the use of thermal energy from combustion, internal combustion engines release the exhaust gases, which have high temperature and contain pollutants harmful to the environment. Energy recovery consists of harnessing the energy that would be wasted during the operation of a system, and in the case of internal combustion engines, the thermal energy of the exhaust gases which are in high temperature can be recovered by means of thermal systems of energy recovery. Between 30% and 40% of the fuel energy is lost through the exhaust gases. Several systems can be used to recover exhaust gas energy, such as the Rankine cycle, thermoelectric, thermoacoustic and thermo-photovoltaic systems, Stirling cycle and others. Stirling engines, are external combustion engines, therefore they can operate with almost any source of heat, and they have high efficiency. In this sense, this work aimed to contribute to the study of the Stirling cycle as an option to recover energy through simulation and experiments to understand the behavior of the alpha type Stirling engine. The simulation was performed by means of a first order mathematical model based on the Schmidt’s theory, implemented with the aid of Matlab® software. The indicated power given by the simulated motor was 0.689 W, while its efficiency was 54.98%, similar to the efficiency of Carnot. In the experiments the temperatures of the hot cylinder, the cold cylinder and inside the flame of an alpha type Stirling were collected, and the electric voltage generated by the dynamo coupled to the motor was measured, considering alternating current. The results showed that the difference between the temperatures of the hot cylinder and the cold cylinder tends to become constant after some time, the temperature inside the flame has values above 600 °C and the electric voltage generated by the dynamo is stable and presented values around 0.36 V.