Resumo:
Currently combustion processes represent the largest amount of energy generated in the world, energy used to sustain the current lifestyle, therefore it is also an important source of pollutants that promote the main contemporary environmental problems. Over time, due to its importance, researches regarding the improvement of combustion processes have been conducted in a variety of fields, such as yield improvement and use of new types of fuels. Among the new technologies used, flameless combustion offers basically a good yield combined to low emission of NOx and CO, and it is researched widely with gaseous fuels. The use of liquid and solid fuels has still been explored in the last years in a limited form, comparing with gaseous fuels. In this thesis, a combustion chamber was designed and built operating in a flameless combustion regime using non-traditional liquid fuels (waste tire Pyrolitic Oil) and diesel, for this purpose an effervescent injector was designed to guarantee the atomization inside the chamber. A computational simulation model was created and validated using the commercial Fluent/ANSYS® Academic Student 2019 R2 software to numerically determine the conditions under which flameless combustion using S-10 diesel would take place. The simulation results were compared to experiments performed in flameless chambers of similar geometry observing the results of the temperatures and the internal recirculation patterns (current lines) of the burned gases. The best recirculation conditions and temperature homogeneity were obtained for coefficients of excess air (λ) higher than 1.2. From the results of the fluid dynamics simulation, an effervescent type injector and a small combustion chamber, designed to work with up to 20kW, were designed and built. This chamber was tested with S-10 Diesel and with mixtures of S-10 Diesel and TPO (tyre pyrolysis oil) in mixtures of: 98% S-10 Diesel & 2% TPO, 95% S-10 Diesel & 5% TPO and 90% S-10 Diesel & 10% TPO. The carried out tests resulted in obtaining the flameless combustion regime with the extinction of the traditional flame, besides homogenization of temperatures within the chamber and a drop in NOx gas emissions.
