AeroG-LAETA - Associate Laboratory of Energy, Transports and Aeronautics
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The Aeronautics and Astronautics Research Center (AeroG) is dedicated to the research and technology development in the field of Aeronautics and Space, with a view to improving safety and environmental protection, while promoting the socioeconomic growth and the quality of life of citizens. The activities of the AeroG aim at contributing to strengthen the excellence of European science base in the scientific and technological fields of aeronautics and astronautics.
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Browsing AeroG-LAETA - Associate Laboratory of Energy, Transports and Aeronautics by Author "Antunes, Eduardo Luís Santos Farias"
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- Cubic and multiparameter equations of state evaluation for supercritical flow modelingPublication . Magalhães, Leandro; Antunes, Eduardo Luís Santos Farias; Silva, André; Barata, Jorge M MThe dawn of space exploration privatizing contributed to a boost and renewed interest in the modeling of vehicles used for such missions. However, the increase of temperature and pressure in combustion chambers, while enhancing fuel injection efficiency, makes fuel and oxidizer exceed their critical point entering a supercritical state. While cubic equations of state such as the Soave-Redlich-Kwong and Peng-Robinson are widely utilized due to their relative simplicity, recent formulations of multiparameter equations for transport properties based on the Helmholtz reduced energy are proving to be an alternative worth considering. The higher accuracy and improved performance of these equations in the critical region is a time-consuming enterprise, relying on large and accurate data sets. Therefore, this work aims at evaluating the influence of cubic and multiparameter transport equations of state in the numerical evolution of density and temperature inside a cryogenic liquid rocket combustion chamber at supercritical conditions.
- Evaluation of Numerical Variable Density Approach to Cryogenic JetsPublication . Antunes, Eduardo Luís Santos Farias; Silva, André; Barata, Jorge M MThe present work is devoted to study cryogenic nitrogen jets in high subcritical conditions. Fuel injection is one of the great challenges in engineering of diesel engines, gas turbines and rocket engines, combining in the last one also the injection of oxidizer. It is widely known that the increase of operation pressures and temperatures increases engine efficiency and reduces fuel specific consumption. Thus, it is a general trend in modern engines the operation in increasingly higher pressures. However at higher chamber pressures the injected fluids may experience ambient conditions exceeding the critical values. Several authors stated that at these conditions the injected fluids suffers a change of its properties, and the traditional two-phase flow models cannot correctly predict the jet behavior at these conditions, thus new computational models are needed for these specific conditions. Barata et al. [18] performed a numerical investigation aimed to evaluate the applicability of an incompressible but variable density model in liquid jets under sub-to-supercritical conditions. The results achieved agree well with the experimental data but they only considered intermediate density ratios from 0.05 to 0.14. The objective of the present work was to extend the investigation of Ref. 18 to lower density ratios from 0.025 to 0.045 which correspond to cases with subcritical chamber pressures. The obtained results agree well with the experimental and numerical data of Chehroudi et al. presented in Ref. 18. It was also found in this work that the computational model does not offers valid results for density ratios lower than 0.025.
- Modelling of transcritical and supercritical nitrogen jetsPublication . Antunes, Eduardo Luís Santos Farias; Silva, A. R. R.; Barata, Jorge M MThe present paper addresses the modelling of fuel injection at conditions of high pressure and temperature which occur in a variety of internal combustion engines such as liquid fuel rocket engines, gas turbines, and modern diesel engines. For this investigation a cryogenic nitrogen jet ranging from transcritical to supercritical conditions injected into a chamber at supercritical conditions was modelled. Previously a variable density approach, originally conceived for gaseous turbulent isothermal jets, imploying the Favre averaged Navier-Stokes equations together with a “k-ε” turbulence model, and using Amagats law for the determination of density was applied. This approach allows a good agreement with experiments mainly at supercritical injection conditions. However, some departure from experimental data was found at transcritical injection conditions. The present approach adds real fluid thermodynamics to the previous approach, and the effects of heat transfer. The results still show some disagreement at supercritical conditions mainly in the determination of the potential core length but significantly improve the prediction of the jet spreading angle at transcritical injection conditions.
- RANS Modeling of Transcritical and Supercritical Nitrogen JetsPublication . Antunes, Eduardo Luís Santos Farias; Silva, André; Barata, Jorge M MThe present work is dedicated to the study of cryogenic nitrogen jets under supercritical chamber conditions with the objective of simulating the process of fuel injection inside a combustion engine. In order to do so, a numerical simulation using a RANS model was performed over two case studies previously analyzed by other authors both in experimental and numerical studies. The result obtained by the present numerical approach were then compared with previous results and this way accessed the capabilities of RANS approach using a k-ε turbulence model in which the density is calculated through the mixture fraction value to correctly model cryogenic jets at supercritical conditions. The results show the ability to achieve good agreement with other studies for the axial density distribution however for other parameters like the jet spreading angle the same agreement was not found.
- Variable Density Approach for Modeling of Transcritical and Supercritical JetsPublication . Antunes, Eduardo Luís Santos Farias; Silva, A. R. R.; Barata, Jorge M MIn order to study the high pressure and high temperature operating condition of a variety of internal combustion engines such as modern diesel engines, gas turbines and liquid fuel rocket engines, a cryogenic nitrogen jet injected into supercritical chamber conditions was simulated numerically. The favre averaged navier-stokes equations were employed together with a “k-ε” Turbulence Model and using instead of an ideal gas equation of state, the Amagat’s law in an approach originally conceived for gaseous turbulent jets with variable density. The present study describes the assessment of the capabilities of the approach by comparison against experimental data as well as numerical simulation performed by other researcher. The obtained results show an acceptable agreement with experiments for the axial density distribution, failing slightly in the prediction of the jet potential core. Good agreement is observed for radial density distribution as well as for the jet spreading rate.