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Öğe Genetic Algorithm Optimisation of a TNT Solidification Model(Defence Scientific Information Documentation Centre, 2019) Susantez, Cigdem; Caldeira, Aldelio BuenoThe control of the solidification process of energetic materials is important to prevent manufacturing defects in high explosive ammunitions. The present work aims to propose an optimisation procedure to determine the value of the model parameter, avoiding the traditional trial and error approach. In this work, the solidification of TNT has been numerically modelled employing apparent heat capacity method and the model parameter was optimised using genetic algorithm. One dimensional numerical model has been solved in Comsol Multiphysics Modeling Software and the genetic algorithm code was written in Matlab. The Neumann's analytical solution of the solidification front was used as a reference to build the fitness function, following the inverse problems concepts. The optimum model parameter has been predicted after 20 generations and among 30 candidate solutions for each generation. The numerical solution performed with the optimised model parameter has agreed with the analytical solution, indicating the feasibility of the proposed procedure. The discrepancy was 3.8 per cent when maximum difference between analytical and numerical solutions was observed.Öğe Heat Transfer Modelling and Simulation of a 120 mm Smoothbore Gun Barrel During Interior Ballistics(Defence Scientific Information Documentation Centre, 2022) Susantez, Cigdem; Caldeira, Aldelio BuenoUnderstanding the heat transfer phenomenon during interior ballistics and consequently presenting a realistic model is very important to predict the temperature distribution inside the cannon barrel, which influences the gun wear and the cook-off. The objective of this work is to present a new detailed numerical model for the prediction of thermal behaviour of a cannon barrel by combining PRODAS interior ballistics simulation with COMSOL simulation. In this study, a numerical model has been proposed for the heating behaviour of a 120 mm smoothbore cannon barrel, taking into account the combustion equation of the JA-2 propellant. Temperature dependent thermophysical properties of product gases were used for the calculation of the convective heat transfer coefficient inside the barrel. Projectile position, velocity of the projectile, gas temperature inside the barrel, volume behind the projectile and mass fraction during interior ballistics have been obtained by PRODAS software and used in the numerical model performed by COMSOL multiphysics finite element modelling and simulation software. Temperature simulations show that maximum wall temperature inside the cannon barrel is observed after 3 ms from fire, when maximum value of the convective heat transfer coefficient inside the barrel is observed. The results reveal that the convective heat transfer coefficient of burned gases inside the gun has major effect than the burned gas temperature on the heat transfer phenomenon.Öğe INVESTIGATION OF THE TIME DEPENDENT THERMAL BEHAVIOR OF A CONTAINER WITH PCM WALLS DURING A HOT SUMMER DAY(Turkish Soc Thermal Sciences Technology, 2020) Susantez, Cigdem; Caldeira, Aldelio BuenoIn this paper, the thermal comfort of a container with PCM walls has been investigated numerically for a hot summer day in Rio de Janeiro. Four different cases have been investigated. These cases are: (i) container made by Polyurethane plates, which is the reference solution, (ii) RT 22 HC plates, (iii) RT 25 HC plates and (iv) RT 28 HC plates. Analyses have been performed for 10 hours from 08:00 to 18:00 h, and dimensionless numerical results for all investigated cases have been presented. Nondimensional governing equations have been solved by COMSOL Multiphysics finite element modeling and simulation software. Results show that although thermal conductivity of polyurethane is one-eighth of that of PCM, the container with PCM walls present considerably better performance. It has been observed that the average value of the dimensionless temperature inside the container is equal to its initial value at the end of the investigation time for the cases of RT 22 HC and RT 25 HC are used. On the other hand, this value shows increments of 0.1235 (2.35 degrees C) and 0.7710 (14.65 degrees C) respect to initial temperature, respectively for the cases of RT 28 HC and polyurethane are used at the end of that time.Öğe A simplified numerical approach to hydrogen and hydrocarbon combustion in single and double-layer porous burners(Pergamon-Elsevier Science Ltd, 2020) Caldeira, Aldelio Bueno; Susantez, CigdemMotivated by the fuel hydrogen applications in porous combustors, as well as hydrogen production in syngas porous devices, this work shows a simplified one-dimensional, steady state heat and mass transfer model for stabilized premixed flames in porous inert media. Single-layer and double-layer porous burner are studied. The model has three conservation equations, describing the heat transfer in the solid and fluid phases and the mass transfer in the reacting flow. The model considers a plug flow and is solved numerically by using the finite volume method. The results are compared with benchmark data, depicting the superadiabatic flames and the heat recirculation process. A parametric analysis of the model reveals the effects of the porous media properties and the Lewis and Peclet numbers on the heat and mass transfer processes. Furthermore, the effects of the flame stand-off parameter in double layer porous burner are also analyzed. The results have considered the values of the dimensionless parameters based on reference data for hydrogen/air and methane/air combustion in porous burners built with SiC and Al2O3. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
