The gas turbine combustion chamber is one of the most critical components to be designed, because it must ensure a stable operation in a wide range of air/fuel ratio and load. Among several calculations involved in the design of a combustion chamber, the reference area is the most important physical parameter, especially by the great impact on other dimensions. In general, this parameter must be calculated from an analysis of the limitations imposed both chemical reactions and aerodynamics, i.e., based on combustion process requirements and maximum pressure drop allowable in the combustion chamber, respectively. So, the aim of this paper is investigate the influence of the reference area in the velocity profile, in the temperature distribution, in the mixing process and in the flame behavior, according to the reference area used in the combustion chamber. These numerical analyses were carried out using ANSYS CFX®, comparing them with the base value calculated by Lefebvre [5], for a thermodynamic cycle of 600 kW gas turbine engine, conduced in GateCycle® program. Finally, it can be concluded that some changes in the reference area calculated by Lefebvre [4] produces better results, especially by improving the burning process and the behavior of the flame.

ResumoEncontrar um conjunto ótimo de parâmetros para um processo de soldagem é uma tarefa pouco trivial, face às múltiplas características exigíveis ou desejáveis que devem ser analisadas. Além disso, a negligência da estrutura de variância-covariância Palavras-chave: Erro Quadrático Médio Multivariado (EQMM). FCAW. Projeto e Análise de Experimentos. Metodologia de Superfície de Respostas. Abstract: The optimization of welding processes is not a trivial task, mainly due to the great number of exigible and desirable characteristics that must be analyzed. Moreover, the optimization of a welding process with multiple characteristics without to consider the variance-covariance structure, may lead to inadequate optimum. To help in this task, a method of multiobjective optimization based in the Multivariate Mean Square Error applied in the study of multiple correlated characteristics of a FCAW (Flux Cored Arc Welding) welding process will be presented. This method characterized by a combined approach based in the Response Surface Methodology, Design of Experiments and Principal Components Analysis consisted in an attempt to achieve the nearest values to specific targets, for each studied characteristic (penetration, deposition rate, deposition efficiency, convexity index of the weld bead and dilution) considering the welding variables expressed in function of welding voltage (V), wire feed speed (Va) and the contact tip to workpiece distance (d). The results point out a good adequacy of the proposed method. Key-words: Multivariate Mean Square Error (MMSE); FCAW; Design of Experiments; Response Surface Methodology (RSM). IntroduçãoNum processo de soldagem é desejável que se determinem parâmetros adequados para sua realização, com a máxima acurácia possível. A busca por esses parâmetros, entretanto, passa por um processo de otimização de múltiplas variáveis, representando múltiplas características de qualidade, exigíveis ou desejáveis, para um determinado processo ou produto, constituindo-se em uma tarefa de difícil execução e de eficácia improvável.

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Os desafios da engenharia industrial na produção de alimentos, energia renovável e na promoção da qualidade de vida das pessoas."