Fritz Rocco - Academia.edu (original) (raw)

vol.7 no.4 by Fritz Rocco

Journal of Aerospace Technology and Management, 2015

In the last decades, hybrid rocket engines have been increasingly studied and used in space vehic... more In the last decades, hybrid rocket engines have been increasingly studied and used in space vehicles. However, the low regression rates and specific impulses still represent major drawbacks to this technology. The objective of this study was to quantify the relative improvement of regression rate values with the use of a swirling flow injector in comparison to an axial injector. Seven tests were conducted with axial injection and seven with swirl injection. Regression rate results were compared, and it was found that swirl injection improved regression rates in 50% for mass fluxes higher than 45 kg • s –1 • m –2. It was possible to see radiation, kinetic and diffusion theory on the logarithmic plot of regression rate per oxidizer flux yielded by both injectors. A strong agreement with experimental findings of regression rates in the literature parameters is reported.

Papers by Fritz Rocco

Journal of Physics: Conference Series, 2020

Predicting explosion parameters is an important step when planning for blast tests or the design ... more Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings and of explosive materials and formulations. This paper presents reactive molecular dynamics simulations of furazanotetrazinedioxide (FTDO) explosive, a new and highly energetic material, calculated with the software LAMMPS with ReaxFF force field. The decomposition steps and chemical mechanism of the material decomposition was elucidated and the Arrhenius parameters of the global decomposition reaction was calculated based on a first order approach with six different isothermal simulations sets. Results present an original mechanism for the detonation/decomposition and an activation energy and frequency factor with high linear determination coefficient. These results are the first ones published for this material and present a good comparison for future experiments.

47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2011

This research aims to provide a methodology for the project of labscale hybrid motors. This devel... more This research aims to provide a methodology for the project of labscale hybrid motors. This development begun with the thermal analysis of the fuel grain using the Flynn, Wall and Ozawa method; this provided the simulation entry data to maximize the motor performance. The computer simulation was performed with the Chemical Equilibrium Specific Impulse Code of the U.S. Air Force, also known as ISP Code. Based on the optimum oxidizer to fuel ratio, the literature was used to supply the mathematical background for the calculation of the motor geometrical parameters whose operating conditions were determined throughout the simulation. Finally, firing tests were conducted to verify the reliability of the project methodology. The firing tests were performed with three injectors: 2 swirling and one axial. The tests showed that the higher the operation pressure the more suitable is the project, meaning the methodology developed works best in hybrid rocket motors with high operating pressures.

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2021

Energetic materials have been used over time in civil and military applications. Concomitantly, s... more Energetic materials have been used over time in civil and military applications. Concomitantly, studies were conducted focusing on the combustion mechanisms of these materials, including their kinetic and thermodynamic behavior during firing. The objective of this work was to systematically study the mechanisms of thermal decomposition of ammonium dinitramide (ADN), and ADN formulated as a solid composite propellant with glycidyl azide polymer (GAP), through reactive molecular dynamics simulations. The main reactions of the mechanisms were elucidated and analyzed, and the Arrhenius parameters were determined for the global processes. Calculated activation energies for the systems were 127.84 and 354.72 kJ/mol for ADN and ADN/GAP, respectively. Comparison to literature data shows up to 14% of deviation, which proves the methodology useful for predictions and kinetic analyzes of combustion/pyrolysis reactions of energetic materials.

AIAA Journal, 1974

Single crystal and pressed polycrystalline ammonium perchlorate (AP) wafers, pressed polycrystall... more Single crystal and pressed polycrystalline ammonium perchlorate (AP) wafers, pressed polycrystalline AP pellets, and ammonium perchlorate-binder (polybutadiene acrylic acid, hydroxyl terminated polybutadiene , polyurethane , and carboxyl terminated polybutadiene) sandwiches were burned in a schlieren equipped combustion bomb and in a centrifuge mounted combustion bomb. High-speed color schlieren and regular motion pictures were taken of the combustion process to determine the effects of pressure, binder type, binder thickness, and purity of ammonium perchlorate on the AP deflagration. AP pellet fabrication techniques and burning rate acceleration sensitivity were also investigated. ammonium perchlorate and to Mr. Edward Michelson for his assistance in conducting the experiments .

Ingeniería e Investigación, 2018

This paper presents results from blast tests conducted on four 50 MPa concrete slabs with reinfor... more This paper presents results from blast tests conducted on four 50 MPa concrete slabs with reinforcement ratios of 0,175% and 0,37%. Two of the slabs were retrofitted with 50 mm thick foam in order to investigate the potential of using the foam as a strengthening option. The slabs were simply supported on two sides. Non-confined PBX (Plastic bonded explosive) was molded with the form of a cylinder measuring 20 cm in height and 10,5 cm in diameter. The explosive was detonated at 2 m stand-off distance. The equivalent TNT mass of the explosive ranges from 2,58 to 2,72 kg for the four tests. Accelerometers, displacement and pressure gages were used to measure blast wave parameters and global response of the slabs. A high-speed digital camera in conjunction with a rugged notebook recorded images. Qualitative and quantitative results are included. Slabs retrofitted with foam showed a different pressure pattern as recorded by the sensors and resulted in higher displacement, acceleration an...

O presente estudo avaliou diferentes formulações de propelentes sólidos à base de PBLH/AP/Al modi... more O presente estudo avaliou diferentes formulações de propelentes sólidos à base de PBLH/AP/Al modificados por dióis de cadeia curta, 1,4-butanodiol e 1,2-propanodiol, em diferentes concentrações mássicas, com intuito de obter propriedades mecânicas diferenciadas sem negligenciar os demais requisitos impostos, tais como processabilidade e propriedades balísticas, destas mesmas formulações. Neste sentido, desenvolveu-se uma metodologia de cálculo das formulações, onde o processamento das mesmas foi realizado em reator de pequeno porte. Com a intenção de avaliar a influência do teor mássico de plastificante empregado, também foi processada uma formulação, de maior teor de 1,4-butanodiol, com maior quantidade de plastificante. Para tanto, avaliou-se o perfil de viscosidade dinâmica pós-processamentos, a evolução da propriedade mecânica da dureza durante a cura e realizaram-se ensaios mecânicos de tração e dureza finais. Realizaram-se também ensaios de determinação de massa específica, Raio-X das amostras e bomba calorimétrica. Ficou evidente que formulações modificadas com 1,4-butanodiol são promissoras. Não obstante, não foi possível alcançar no presente estudo todos os requisitos esperados em um produto final para emprego imediato. Palavras-chave: propulsão sólida; propelente compósito; extensor de cadeia.

The molecular dynamics simulations were used to study the epoxy ring-opening in the determination... more The molecular dynamics simulations were used to study the epoxy ring-opening in the determination of kinetic parameters, with a temperature range from 1500 to 2500 K in a 20 x 20 x 20 Å unit cell containing 15 molecules of C2H4O (ethylene oxide) and 35 molecules of CH6N2 (methanediamine). The activation energy values for epoxy and diamine was 66 and 92 kJ mol-1, respectively. The simulation showed epoxy ring breakage in some of the molecules, but mainly the release of ammonia by diamine. It was observed that the activation energy involved in diamine consumption for ammonia formation is higher than for the epoxy ring opening. The results of the epoxy ring-opening study show that the polymerization occurs slowly, which leads to high computational simulation values.

Anais da Academia Brasileira de Ciências, 2021

Hydroxyl-terminated polybutadiene (HTPB) is widely used in the formulations of solid propellants ... more Hydroxyl-terminated polybutadiene (HTPB) is widely used in the formulations of solid propellants used in rocket motors. Furthermore, in general, chain extenders and short chain diols, such as 1,4-butanediol and 1,2-propanediol, can also be used in propellant formulations to improve mechanical properties, especially tensile strength. However, the incorporation of these diols can result in a considerable increase in the viscosity of the mixture during the processing of propellants. Thus, the present study evaluated the compatibility of these diols with the HTPB prepolymer, through a viscometric study, with the aim to determine the order of addition that results in greater homogeneity for the mixture. It was concluded that 1,4-butanediol, due to its larger chain size, has better compatibility with HTPB resin than 1,2-propanediol. On top of that, it was found that when the resin is added fi rst, it results in mixtures with greater compatibility.

Propellants, Explosives, Pyrotechnics, 2021

Journal of Applied Polymer Science, 2021

Propellants, Explosives, Pyrotechnics, 2021

Acta Scientiarum. Technology, 2019

Predicting explosion parameters is an important step when planning for blast tests or the design ... more Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings. This paper presents a comparison of recorded pressure that was reflected on the surface of reinforced concrete slabs with and without EPS (Expanded Polystyrene) foam retrofit measured from a detonation of 2.7 kg of non-confined plastic explosive. Two 50 MPa reinforced concrete slabs measuring 1.0x1.0x0.08 m, simply supported on two sides were tested. The explosive was suspended at a distance of 2.0 m from the upper surface of the slabs; one of the slabs had 5.0 cm thick foam on the top side. Eight piezoelectric pressure sensors were positioned at a distance of 2.0 m from the explosive. Results showed that the foam retrofit reduced the reflected pressure by approximately 57% when compared to the slab without EPS foam retrofit.

Defence Science Journal, 2018

Explosions emanating from terrorist attacks or military weapons cause damage to civilian and mili... more Explosions emanating from terrorist attacks or military weapons cause damage to civilian and military facilities. Understanding the mechanical behaviour of reinforced concrete structures subjected to blast is of paramount importance for minimizing the possible blast damage. A full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa, measuring 1.0 m × 1.0 m × 0.08 m, and subjected to 2.7 kg of non-confined plastic bonded explosive, was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force). This paper compares experimentally measured peak displacement values with theoretical values. Theoretical analysis was carried out using single degree of freedom (SDOF) models. The comparison showed that SDOF analysis worked very well in predicting the reinforced concrete slab peak displacement against blast effects. Qualitative analysis after the experiments showed that the blast ...

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019

Propellants based on HTPB/AP (hydroxyl-terminated polybutadiene/ammonium perchlorate) are the mos... more Propellants based on HTPB/AP (hydroxyl-terminated polybutadiene/ammonium perchlorate) are the most commonly used in most of the rocket engines used by the Brazilian Armed Forces. This work aimed at the possibility of extending its useful life (currently in 10 years) by performing chemical kinetic analysis of the energetic material via differential scanning calorimetry (DSC) and also performing computer simulation of aging process using the software Large-scale Atomic/Molecular Massively Parallel Simulator. The simulations presented the experimental behavior of the aging process, showing the bending and cross-link of the binder with the volume contraction and the energetic stabilization. Thermal analysis via DSC was performed in triplicate and in 3 heating ratios (5 °C, 10 °C and 15 °C) of rocket motor with 11-year shelf-life, using the Arrhenius equation to obtain its activation energy, using Ozawa and Kissinger kinetic methods, allowing comparison with manufacturing period data (standard motor). The obtained activation energies were 126.67 kJ/mol (Ozawa) and 122.85 kJ/mol (Kissinger), much higher than that of the aged propellants (~ 78 kJ/mol, based on literature data), showing that the propellant has not yet aged significantly. In addition, the kinetic parameters of internal pressure of the combustion chamber in 8 rocket engines with 11 years of shelf-life were also acquired, for comparison purposes with the engine start-up data.

Química Nova, 2019

DETERMINATION OF KINETIC PARAMETERS AND COMPUTATIONAL SIMULATION OF PERFLUOROPOLYTER (PFPE) EMPLO... more DETERMINATION OF KINETIC PARAMETERS AND COMPUTATIONAL SIMULATION OF PERFLUOROPOLYTER (PFPE) EMPLOYED AS A SYNTHETIC LUBRICANT. This work aims to determine the kinetic parameters of the thermal decomposition of a lubricating grease based on perfluoropolyether (PFPE) and the computational simulation of this decomposition. The determination of kinetic parameters of thermal decomposition was done by thermal analysis using thermogravimetry (TG) at different heating rates (β) of 10, 15 and 20 °C min-1. With the TG curves obtained, the kinetic parameters were determined by the kinetics methods of Goldfarb et al. and Duvvuri et al., Flynn-Wall-Ozawa and Kissinger. The activation energy of the thermal decomposition of the PFPE grease in the kinect models ranged from 63.54 to 112.3 kJ mol-1. The results of the thermogravimetry indicated that the PFPE grease is thermally stable up to 300 °C. A simulation of the thermal decomposition of the PFPE oil base was carried out by molecular dynamics simulation, using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) in a temperature range of 0 to 3500 K during 50 ps. The value of the activation energy in the simulation was 92 kJ mol-1. The results show that PFPE oil base and PFPE lubricant grease can be used in high-temperature applications.

International Journal of Energetic Materials and Chemical Propulsion, 2017

Química Nova, 2018

LINEAR AND NON-LINEAR EQUATIONS TO PREDICT THE BEHAVIOR OF PHYSICO-CHEMICAL PROPERTIES OF AVIATIO... more LINEAR AND NON-LINEAR EQUATIONS TO PREDICT THE BEHAVIOR OF PHYSICO-CHEMICAL PROPERTIES OF AVIATION FUEL MIXED WITH ALTERNATIVE BIOQUEROSENE DROP-IN. Density, viscosity and calorific values are important physical properties to affect the utilization of biofuel. In this work, mixtures of farnesane and a "jet fuel", QAv-1, were used to study the variation of density and kinematic viscosity as a function of the volumetric fraction of farnesane and temperature. Experimental measurements were carried out for nineteen farnesane blends and pure farnesane and QAv-1, at four temperatures in the range of 293-323 K. Variation of high heating (HHV) and low heating (LHV) values were also determined for different blends of farnesane/ QAv-1. Several empirical correlations were used to predict the density, the kinematic viscosity, HHV and LHV values. By using some of these empirical correlations, the estimated values of those three properties studied are in excellent agreement with the experimental data, with low absolute average prediction error.

Structures Congress 2017, 2017

Journal of Aerospace Technology and Management, 2015

In the last decades, hybrid rocket engines have been increasingly studied and used in space vehic... more In the last decades, hybrid rocket engines have been increasingly studied and used in space vehicles. However, the low regression rates and specific impulses still represent major drawbacks to this technology. The objective of this study was to quantify the relative improvement of regression rate values with the use of a swirling flow injector in comparison to an axial injector. Seven tests were conducted with axial injection and seven with swirl injection. Regression rate results were compared, and it was found that swirl injection improved regression rates in 50% for mass fluxes higher than 45 kg • s –1 • m –2. It was possible to see radiation, kinetic and diffusion theory on the logarithmic plot of regression rate per oxidizer flux yielded by both injectors. A strong agreement with experimental findings of regression rates in the literature parameters is reported.

Journal of Physics: Conference Series, 2020

Predicting explosion parameters is an important step when planning for blast tests or the design ... more Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings and of explosive materials and formulations. This paper presents reactive molecular dynamics simulations of furazanotetrazinedioxide (FTDO) explosive, a new and highly energetic material, calculated with the software LAMMPS with ReaxFF force field. The decomposition steps and chemical mechanism of the material decomposition was elucidated and the Arrhenius parameters of the global decomposition reaction was calculated based on a first order approach with six different isothermal simulations sets. Results present an original mechanism for the detonation/decomposition and an activation energy and frequency factor with high linear determination coefficient. These results are the first ones published for this material and present a good comparison for future experiments.

47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2011

This research aims to provide a methodology for the project of labscale hybrid motors. This devel... more This research aims to provide a methodology for the project of labscale hybrid motors. This development begun with the thermal analysis of the fuel grain using the Flynn, Wall and Ozawa method; this provided the simulation entry data to maximize the motor performance. The computer simulation was performed with the Chemical Equilibrium Specific Impulse Code of the U.S. Air Force, also known as ISP Code. Based on the optimum oxidizer to fuel ratio, the literature was used to supply the mathematical background for the calculation of the motor geometrical parameters whose operating conditions were determined throughout the simulation. Finally, firing tests were conducted to verify the reliability of the project methodology. The firing tests were performed with three injectors: 2 swirling and one axial. The tests showed that the higher the operation pressure the more suitable is the project, meaning the methodology developed works best in hybrid rocket motors with high operating pressures.

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2021

Energetic materials have been used over time in civil and military applications. Concomitantly, s... more Energetic materials have been used over time in civil and military applications. Concomitantly, studies were conducted focusing on the combustion mechanisms of these materials, including their kinetic and thermodynamic behavior during firing. The objective of this work was to systematically study the mechanisms of thermal decomposition of ammonium dinitramide (ADN), and ADN formulated as a solid composite propellant with glycidyl azide polymer (GAP), through reactive molecular dynamics simulations. The main reactions of the mechanisms were elucidated and analyzed, and the Arrhenius parameters were determined for the global processes. Calculated activation energies for the systems were 127.84 and 354.72 kJ/mol for ADN and ADN/GAP, respectively. Comparison to literature data shows up to 14% of deviation, which proves the methodology useful for predictions and kinetic analyzes of combustion/pyrolysis reactions of energetic materials.

AIAA Journal, 1974

Single crystal and pressed polycrystalline ammonium perchlorate (AP) wafers, pressed polycrystall... more Single crystal and pressed polycrystalline ammonium perchlorate (AP) wafers, pressed polycrystalline AP pellets, and ammonium perchlorate-binder (polybutadiene acrylic acid, hydroxyl terminated polybutadiene , polyurethane , and carboxyl terminated polybutadiene) sandwiches were burned in a schlieren equipped combustion bomb and in a centrifuge mounted combustion bomb. High-speed color schlieren and regular motion pictures were taken of the combustion process to determine the effects of pressure, binder type, binder thickness, and purity of ammonium perchlorate on the AP deflagration. AP pellet fabrication techniques and burning rate acceleration sensitivity were also investigated. ammonium perchlorate and to Mr. Edward Michelson for his assistance in conducting the experiments .

Ingeniería e Investigación, 2018

This paper presents results from blast tests conducted on four 50 MPa concrete slabs with reinfor... more This paper presents results from blast tests conducted on four 50 MPa concrete slabs with reinforcement ratios of 0,175% and 0,37%. Two of the slabs were retrofitted with 50 mm thick foam in order to investigate the potential of using the foam as a strengthening option. The slabs were simply supported on two sides. Non-confined PBX (Plastic bonded explosive) was molded with the form of a cylinder measuring 20 cm in height and 10,5 cm in diameter. The explosive was detonated at 2 m stand-off distance. The equivalent TNT mass of the explosive ranges from 2,58 to 2,72 kg for the four tests. Accelerometers, displacement and pressure gages were used to measure blast wave parameters and global response of the slabs. A high-speed digital camera in conjunction with a rugged notebook recorded images. Qualitative and quantitative results are included. Slabs retrofitted with foam showed a different pressure pattern as recorded by the sensors and resulted in higher displacement, acceleration an...

O presente estudo avaliou diferentes formulações de propelentes sólidos à base de PBLH/AP/Al modi... more O presente estudo avaliou diferentes formulações de propelentes sólidos à base de PBLH/AP/Al modificados por dióis de cadeia curta, 1,4-butanodiol e 1,2-propanodiol, em diferentes concentrações mássicas, com intuito de obter propriedades mecânicas diferenciadas sem negligenciar os demais requisitos impostos, tais como processabilidade e propriedades balísticas, destas mesmas formulações. Neste sentido, desenvolveu-se uma metodologia de cálculo das formulações, onde o processamento das mesmas foi realizado em reator de pequeno porte. Com a intenção de avaliar a influência do teor mássico de plastificante empregado, também foi processada uma formulação, de maior teor de 1,4-butanodiol, com maior quantidade de plastificante. Para tanto, avaliou-se o perfil de viscosidade dinâmica pós-processamentos, a evolução da propriedade mecânica da dureza durante a cura e realizaram-se ensaios mecânicos de tração e dureza finais. Realizaram-se também ensaios de determinação de massa específica, Raio-X das amostras e bomba calorimétrica. Ficou evidente que formulações modificadas com 1,4-butanodiol são promissoras. Não obstante, não foi possível alcançar no presente estudo todos os requisitos esperados em um produto final para emprego imediato. Palavras-chave: propulsão sólida; propelente compósito; extensor de cadeia.

The molecular dynamics simulations were used to study the epoxy ring-opening in the determination... more The molecular dynamics simulations were used to study the epoxy ring-opening in the determination of kinetic parameters, with a temperature range from 1500 to 2500 K in a 20 x 20 x 20 Å unit cell containing 15 molecules of C2H4O (ethylene oxide) and 35 molecules of CH6N2 (methanediamine). The activation energy values for epoxy and diamine was 66 and 92 kJ mol-1, respectively. The simulation showed epoxy ring breakage in some of the molecules, but mainly the release of ammonia by diamine. It was observed that the activation energy involved in diamine consumption for ammonia formation is higher than for the epoxy ring opening. The results of the epoxy ring-opening study show that the polymerization occurs slowly, which leads to high computational simulation values.

Anais da Academia Brasileira de Ciências, 2021

Hydroxyl-terminated polybutadiene (HTPB) is widely used in the formulations of solid propellants ... more Hydroxyl-terminated polybutadiene (HTPB) is widely used in the formulations of solid propellants used in rocket motors. Furthermore, in general, chain extenders and short chain diols, such as 1,4-butanediol and 1,2-propanediol, can also be used in propellant formulations to improve mechanical properties, especially tensile strength. However, the incorporation of these diols can result in a considerable increase in the viscosity of the mixture during the processing of propellants. Thus, the present study evaluated the compatibility of these diols with the HTPB prepolymer, through a viscometric study, with the aim to determine the order of addition that results in greater homogeneity for the mixture. It was concluded that 1,4-butanediol, due to its larger chain size, has better compatibility with HTPB resin than 1,2-propanediol. On top of that, it was found that when the resin is added fi rst, it results in mixtures with greater compatibility.

Propellants, Explosives, Pyrotechnics, 2021

Journal of Applied Polymer Science, 2021

Propellants, Explosives, Pyrotechnics, 2021

Acta Scientiarum. Technology, 2019

Predicting explosion parameters is an important step when planning for blast tests or the design ... more Predicting explosion parameters is an important step when planning for blast tests or the design of blast resistant buildings. This paper presents a comparison of recorded pressure that was reflected on the surface of reinforced concrete slabs with and without EPS (Expanded Polystyrene) foam retrofit measured from a detonation of 2.7 kg of non-confined plastic explosive. Two 50 MPa reinforced concrete slabs measuring 1.0x1.0x0.08 m, simply supported on two sides were tested. The explosive was suspended at a distance of 2.0 m from the upper surface of the slabs; one of the slabs had 5.0 cm thick foam on the top side. Eight piezoelectric pressure sensors were positioned at a distance of 2.0 m from the explosive. Results showed that the foam retrofit reduced the reflected pressure by approximately 57% when compared to the slab without EPS foam retrofit.

Defence Science Journal, 2018

Explosions emanating from terrorist attacks or military weapons cause damage to civilian and mili... more Explosions emanating from terrorist attacks or military weapons cause damage to civilian and military facilities. Understanding the mechanical behaviour of reinforced concrete structures subjected to blast is of paramount importance for minimizing the possible blast damage. A full-scale experimental program consisting of six reinforced concrete slabs with compressive strengths of 60 MPa, 50 MPa and 40 MPa, measuring 1.0 m × 1.0 m × 0.08 m, and subjected to 2.7 kg of non-confined plastic bonded explosive, was conducted in blast test area of Science and Technology Aerospace Department (Brazilian Air Force). This paper compares experimentally measured peak displacement values with theoretical values. Theoretical analysis was carried out using single degree of freedom (SDOF) models. The comparison showed that SDOF analysis worked very well in predicting the reinforced concrete slab peak displacement against blast effects. Qualitative analysis after the experiments showed that the blast ...

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019

Propellants based on HTPB/AP (hydroxyl-terminated polybutadiene/ammonium perchlorate) are the mos... more Propellants based on HTPB/AP (hydroxyl-terminated polybutadiene/ammonium perchlorate) are the most commonly used in most of the rocket engines used by the Brazilian Armed Forces. This work aimed at the possibility of extending its useful life (currently in 10 years) by performing chemical kinetic analysis of the energetic material via differential scanning calorimetry (DSC) and also performing computer simulation of aging process using the software Large-scale Atomic/Molecular Massively Parallel Simulator. The simulations presented the experimental behavior of the aging process, showing the bending and cross-link of the binder with the volume contraction and the energetic stabilization. Thermal analysis via DSC was performed in triplicate and in 3 heating ratios (5 °C, 10 °C and 15 °C) of rocket motor with 11-year shelf-life, using the Arrhenius equation to obtain its activation energy, using Ozawa and Kissinger kinetic methods, allowing comparison with manufacturing period data (standard motor). The obtained activation energies were 126.67 kJ/mol (Ozawa) and 122.85 kJ/mol (Kissinger), much higher than that of the aged propellants (~ 78 kJ/mol, based on literature data), showing that the propellant has not yet aged significantly. In addition, the kinetic parameters of internal pressure of the combustion chamber in 8 rocket engines with 11 years of shelf-life were also acquired, for comparison purposes with the engine start-up data.

Química Nova, 2019

DETERMINATION OF KINETIC PARAMETERS AND COMPUTATIONAL SIMULATION OF PERFLUOROPOLYTER (PFPE) EMPLO... more DETERMINATION OF KINETIC PARAMETERS AND COMPUTATIONAL SIMULATION OF PERFLUOROPOLYTER (PFPE) EMPLOYED AS A SYNTHETIC LUBRICANT. This work aims to determine the kinetic parameters of the thermal decomposition of a lubricating grease based on perfluoropolyether (PFPE) and the computational simulation of this decomposition. The determination of kinetic parameters of thermal decomposition was done by thermal analysis using thermogravimetry (TG) at different heating rates (β) of 10, 15 and 20 °C min-1. With the TG curves obtained, the kinetic parameters were determined by the kinetics methods of Goldfarb et al. and Duvvuri et al., Flynn-Wall-Ozawa and Kissinger. The activation energy of the thermal decomposition of the PFPE grease in the kinect models ranged from 63.54 to 112.3 kJ mol-1. The results of the thermogravimetry indicated that the PFPE grease is thermally stable up to 300 °C. A simulation of the thermal decomposition of the PFPE oil base was carried out by molecular dynamics simulation, using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) in a temperature range of 0 to 3500 K during 50 ps. The value of the activation energy in the simulation was 92 kJ mol-1. The results show that PFPE oil base and PFPE lubricant grease can be used in high-temperature applications.

International Journal of Energetic Materials and Chemical Propulsion, 2017

Química Nova, 2018

LINEAR AND NON-LINEAR EQUATIONS TO PREDICT THE BEHAVIOR OF PHYSICO-CHEMICAL PROPERTIES OF AVIATIO... more LINEAR AND NON-LINEAR EQUATIONS TO PREDICT THE BEHAVIOR OF PHYSICO-CHEMICAL PROPERTIES OF AVIATION FUEL MIXED WITH ALTERNATIVE BIOQUEROSENE DROP-IN. Density, viscosity and calorific values are important physical properties to affect the utilization of biofuel. In this work, mixtures of farnesane and a "jet fuel", QAv-1, were used to study the variation of density and kinematic viscosity as a function of the volumetric fraction of farnesane and temperature. Experimental measurements were carried out for nineteen farnesane blends and pure farnesane and QAv-1, at four temperatures in the range of 293-323 K. Variation of high heating (HHV) and low heating (LHV) values were also determined for different blends of farnesane/ QAv-1. Several empirical correlations were used to predict the density, the kinematic viscosity, HHV and LHV values. By using some of these empirical correlations, the estimated values of those three properties studied are in excellent agreement with the experimental data, with low absolute average prediction error.

Structures Congress 2017, 2017