cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.7511798
title: Copper/Iron Brake Friction for Military Aircraft Application

description: ABSTRACT: The present study assesses the influence of non-metallic constituents and manufacturing parameters, such as compaction pressure and sintering temperature, to produce a metal matrix composite (MMC) of copper/iron, based on the brake disc of aircraft AT-29 SuperTucano. The samples were produced with six different compositions, by varying the amount of abrasive particles (quartz and zirconia silicate) and the solid lubricant (graphite), with one of the compositions manufactured without the addition of graphite. The compaction pressures were 210 and 420 MPa, with sintering temperatures of 950 °C and 1050 °C in a furnace with controlled atmosphere of argon + 10% H2. After sintering, the effectiveness of the sintering process was evaluated through the apparent density (Archimedes's method), Brinell and Vickers hardness, and the microstructure by Scanning Electron Microscopy (SEM). The sintering process was severely affected by the solid lubricant (graphite): its reduction resulted in a density increase near 18%, and the hardness of the compound up to 62%. The hardness values demonstrated significant variation with compaction pressure, with a pronounced effect on compounds with less non-metallic elements. SEM analysis demonstrated that not only graphite, but also the ceramic particles affected the sintering process through the agglomeration of inclusions into the metal-metal interface. The samples without graphite exhibited almost the same value of pores after sintering, regardless of the compaction pressure, indicating that the graphite content affects directly the sintering process, regardless of the compaction pressure.
DOI: 10.6084/m9.figshare.7511798.v1
title: Copper/Iron Brake Friction for Military Aircraft Application

description: ABSTRACT: The present study assesses the influence of non-metallic constituents and manufacturing parameters, such as compaction pressure and sintering temperature, to produce a metal matrix composite (MMC) of copper/iron, based on the brake disc of aircraft AT-29 SuperTucano. The samples were produced with six different compositions, by varying the amount of abrasive particles (quartz and zirconia silicate) and the solid lubricant (graphite), with one of the compositions manufactured without the addition of graphite. The compaction pressures were 210 and 420 MPa, with sintering temperatures of 950 °C and 1050 °C in a furnace with controlled atmosphere of argon + 10% H2. After sintering, the effectiveness of the sintering process was evaluated through the apparent density (Archimedes's method), Brinell and Vickers hardness, and the microstructure by Scanning Electron Microscopy (SEM). The sintering process was severely affected by the solid lubricant (graphite): its reduction resulted in a density increase near 18%, and the hardness of the compound up to 62%. The hardness values demonstrated significant variation with compaction pressure, with a pronounced effect on compounds with less non-metallic elements. SEM analysis demonstrated that not only graphite, but also the ceramic particles affected the sintering process through the agglomeration of inclusions into the metal-metal interface. The samples without graphite exhibited almost the same value of pores after sintering, regardless of the compaction pressure, indicating that the graphite content affects directly the sintering process, regardless of the compaction pressure.
DOI: 10.6084/m9.figshare.9985928.v1
title: Review of Power Device for Solar-Powered Aircraft Applications

description: ABSTRACT This paper reviews various power device components of solar-powered aircraft such as photovoltaic (PV) cells, maximum power point tracker (MPPT) and rechargeable batteries. The various power device components were highlighted, and the ones applicable to aircraft were analyzed, based on criteria as efficiency for photovoltaic cells; energy densities about rechargeable batteries; and maximum power point tracker on quick response to achieve maximum power point on I-V curve. Emerging technologies like photovoltaic cells, thin film cell, organic photovoltaic cell, multi-junction cell and silicon quantum dot cell, with the future potential of high efficiencies that can be used in solar-powered aircraft, were all examined. Regarding battery technology, Lithium-air battery (Li-air) was reported as having great opportunities for high energy densities capable of improving the efficiency of the solar-powered aircraft, for the greater prospect of the aviation industry. The design of efficient power device for solar-powered aircraft application is proposed. Gallium Arsenide (GaAs) solar cells were used because of its high energy conversion efficiency of 30 to 40%. A smart and intelligent MPPT Artificial Neural Network (ANN) is chosen because of its efficiency in partial shading and fast response and speed. The Li-air rechargeable battery is proposed because of its theoretical energy density of 11680 Wh/Kg.
DOI: 10.6084/m9.figshare.9985928
title: Review of Power Device for Solar-Powered Aircraft Applications

description: ABSTRACT This paper reviews various power device components of solar-powered aircraft such as photovoltaic (PV) cells, maximum power point tracker (MPPT) and rechargeable batteries. The various power device components were highlighted, and the ones applicable to aircraft were analyzed, based on criteria as efficiency for photovoltaic cells; energy densities about rechargeable batteries; and maximum power point tracker on quick response to achieve maximum power point on I-V curve. Emerging technologies like photovoltaic cells, thin film cell, organic photovoltaic cell, multi-junction cell and silicon quantum dot cell, with the future potential of high efficiencies that can be used in solar-powered aircraft, were all examined. Regarding battery technology, Lithium-air battery (Li-air) was reported as having great opportunities for high energy densities capable of improving the efficiency of the solar-powered aircraft, for the greater prospect of the aviation industry. The design of efficient power device for solar-powered aircraft application is proposed. Gallium Arsenide (GaAs) solar cells were used because of its high energy conversion efficiency of 30 to 40%. A smart and intelligent MPPT Artificial Neural Network (ANN) is chosen because of its efficiency in partial shading and fast response and speed. The Li-air rechargeable battery is proposed because of its theoretical energy density of 11680 Wh/Kg.
DOI: 10.6084/m9.figshare.8227331
title: Effect of Boundary Layer and Rotor Speed on Broadband Noise from Wind Turbines

description: ABSTRACT: Trailing edge surface of aerofoil is an important source of broadband aerodynamic noise production. In this paper, three aerofoil self-noise mechanisms from turbulent boundary layer near trailing edge surface are studied. Numerical computations were performed for a three bladed 2 MW horizontal axis upwind turbine of blade length 37 m and source height of 80 m, for wind speeds of 8-15 m/s. A weighted 1/3rd octave band sound power levels (SPL) are evaluated for receiver located at distance of total turbine height and at 2 m above ground. The results obtained for sound power level using baseline models showed maximum values occurring between 300 Hz and 1 kHz region of spectrum. The trends for BPM model showed a reduction of ~2 dBA near 1 kHz region of spectrum at 10 m/s, but Grosveld’s and Lowson model were identical and agreed over the entire spectrum. The effect of rotational speed on sound power levels using three baseline models are illustrated at a wind speed of 8 m/s for 2 MW turbine. Results showed that for a change of ±10% rotor speed from the rated value, there is an increase of 2 to 6 dBA over the entire sound spectrum due to differences in blade tip speed.
DOI: 10.6084/m9.figshare.8227331.v1
title: Effect of Boundary Layer and Rotor Speed on Broadband Noise from Wind Turbines

description: ABSTRACT: Trailing edge surface of aerofoil is an important source of broadband aerodynamic noise production. In this paper, three aerofoil self-noise mechanisms from turbulent boundary layer near trailing edge surface are studied. Numerical computations were performed for a three bladed 2 MW horizontal axis upwind turbine of blade length 37 m and source height of 80 m, for wind speeds of 8-15 m/s. A weighted 1/3rd octave band sound power levels (SPL) are evaluated for receiver located at distance of total turbine height and at 2 m above ground. The results obtained for sound power level using baseline models showed maximum values occurring between 300 Hz and 1 kHz region of spectrum. The trends for BPM model showed a reduction of ~2 dBA near 1 kHz region of spectrum at 10 m/s, but Grosveld’s and Lowson model were identical and agreed over the entire spectrum. The effect of rotational speed on sound power levels using three baseline models are illustrated at a wind speed of 8 m/s for 2 MW turbine. Results showed that for a change of ±10% rotor speed from the rated value, there is an increase of 2 to 6 dBA over the entire sound spectrum due to differences in blade tip speed.
DOI: 10.6084/m9.figshare.10073255
title: Effect of Pressure Gradient on the Development of Görtler Vortices

description: ABSTRACT: Boundary layers over concave surfaces may become unstable due to centrifugal instability that manifests itself as stationary streamwise counter rotating vortices. The centrifugal instability mechanism in boundary layers has been extensively studied and there is a large number of publications addressing different aspects of this problem. The results on the effect of pressure gradient show that favorable pressure gradients are stabilizing and adverse pressure gradient enhances the instability. The objective of the present investigation is to complement those works, looking particularly at the effect of pressure gradient on the stability diagram and on the determination of the spanwise wave number corresponding to the fastest growth. This study is based on the classic linear stability theory, where the parallel boundary layer approximation is assumed. Therefore, results are valid for Görtler numbers above 7, the lower limit where local mode linear stability analysis was identified in the literature as valid. For the base flow given by the Falkner-Skan solution, the linear stability equations are solved by a shooting method where the eigenvalues are the Görtler number, the spanwise wavenumber and the growth rate. The results show stabilization due to favorable pressure gradient as the constant amplification rate curves are displaced to higher Görtler numbers, with the opposite effect for adverse pressure gradient. Results previously unavailable in the literature identifying the fastest growing mode spanwise wavelength for a range of Falkner-Skan acceleration parameters are presented.
DOI: 10.6084/m9.figshare.10073255.v1
title: Effect of Pressure Gradient on the Development of Görtler Vortices

description: ABSTRACT: Boundary layers over concave surfaces may become unstable due to centrifugal instability that manifests itself as stationary streamwise counter rotating vortices. The centrifugal instability mechanism in boundary layers has been extensively studied and there is a large number of publications addressing different aspects of this problem. The results on the effect of pressure gradient show that favorable pressure gradients are stabilizing and adverse pressure gradient enhances the instability. The objective of the present investigation is to complement those works, looking particularly at the effect of pressure gradient on the stability diagram and on the determination of the spanwise wave number corresponding to the fastest growth. This study is based on the classic linear stability theory, where the parallel boundary layer approximation is assumed. Therefore, results are valid for Görtler numbers above 7, the lower limit where local mode linear stability analysis was identified in the literature as valid. For the base flow given by the Falkner-Skan solution, the linear stability equations are solved by a shooting method where the eigenvalues are the Görtler number, the spanwise wavenumber and the growth rate. The results show stabilization due to favorable pressure gradient as the constant amplification rate curves are displaced to higher Görtler numbers, with the opposite effect for adverse pressure gradient. Results previously unavailable in the literature identifying the fastest growing mode spanwise wavelength for a range of Falkner-Skan acceleration parameters are presented.
DOI: 10.6084/m9.figshare.14328942
title: Studies on Heat Flux Imparted on Thermal Insulation Inside Rocket Motor Containing Double Base Propellant

description: ABSTRACT Thermal insulation inside the rocket motor experience severe pressure and temperature conditions. Experimental determination of heat flux imparted to thermal insulator inside the rocket motor during the static firing is a challenging task. This paper reports experimental determination of heat flux for double base propellant (DBP) in small rocket motor. It includes development of experimental rocket motor, adaptation of water-cooled heat flux sensor on rocket motor, required instrumentation for heat flux time recording and analysis of data. Data are recorded in real time for double base propellant combustion up to the pressure level ~3.6 MPa. Average heat flux imparted to the rocket motor casing is found in the range of 230-300 × 104 W/m2. Heat flux inside the rocket motor varies nearly linear with pressure. A correlation between the heat flux and pressure is also established for measured pressure range.
DOI: 10.6084/m9.figshare.14328942.v1
title: Studies on Heat Flux Imparted on Thermal Insulation Inside Rocket Motor Containing Double Base Propellant

description: ABSTRACT Thermal insulation inside the rocket motor experience severe pressure and temperature conditions. Experimental determination of heat flux imparted to thermal insulator inside the rocket motor during the static firing is a challenging task. This paper reports experimental determination of heat flux for double base propellant (DBP) in small rocket motor. It includes development of experimental rocket motor, adaptation of water-cooled heat flux sensor on rocket motor, required instrumentation for heat flux time recording and analysis of data. Data are recorded in real time for double base propellant combustion up to the pressure level ~3.6 MPa. Average heat flux imparted to the rocket motor casing is found in the range of 230-300 × 104 W/m2. Heat flux inside the rocket motor varies nearly linear with pressure. A correlation between the heat flux and pressure is also established for measured pressure range.
DOI: 10.6084/m9.figshare.10258181.v1
title: The Role of Terrestrial and Space Environments in Launch Vehicle Development

description: ABSTRACT: Natural (Terrestrial & Space) Environment (NE) phenomena play a significant role in the design and flight of aerospace vehicles and in the integrity of the associated aerospace systems and structures. Natural environmental design criteria guidelines described here are based on measurements and modeling of atmospheric and climatic phenomena relative to various aerospace vehicle development and mission/operational procedures, and for vehicle launch locations. Both the terrestrial environment (0-90 km altitude) and the space environment (Earth orbital altitudes) parameters and their engineering application philosophy are given with emphasis on launch vehicle-affected terrestrial environment elements. This paper also addresses the basis for the NE guidelines presented, the interpretation of the guidelines, and application to the development of launch or space vehicle design requirements. This paper represents the first of three on this subject.
DOI: 10.6084/m9.figshare.10258181
title: The Role of Terrestrial and Space Environments in Launch Vehicle Development

description: ABSTRACT: Natural (Terrestrial & Space) Environment (NE) phenomena play a significant role in the design and flight of aerospace vehicles and in the integrity of the associated aerospace systems and structures. Natural environmental design criteria guidelines described here are based on measurements and modeling of atmospheric and climatic phenomena relative to various aerospace vehicle development and mission/operational procedures, and for vehicle launch locations. Both the terrestrial environment (0-90 km altitude) and the space environment (Earth orbital altitudes) parameters and their engineering application philosophy are given with emphasis on launch vehicle-affected terrestrial environment elements. This paper also addresses the basis for the NE guidelines presented, the interpretation of the guidelines, and application to the development of launch or space vehicle design requirements. This paper represents the first of three on this subject.
DOI: 10.6084/m9.figshare.10073261
title: A Comparative Survey on Flight Software Frameworks for ‘New Space’ Nanosatellite Missions

description: ABSTRACT: Nanosatellite missions are becoming increasingly popular nowadays, especially because of their reduced cost. Therefore, many organizations are entering the space sector due to the paradigm shift caused by nanosatellites. Despite the reduced size of these spacecrafts, their Flight Software (FSW) complexity is not proportional to the satellite volume, thus creating a great barrier for the entrance of new players on the nanosatellite market. On the other side, there are some available frameworks that can provide mature FSW design approaches, implying in considerable reduction in software project timeframe and cost. This paper presents a comparative survey between six relevant flight software frameworks, compared according to commonly required ‘New Space’ criteria, and finally points out the most suitable one to the VCUB1 reference nanosatellite mission.
DOI: 10.6084/m9.figshare.10073261.v1
title: A Comparative Survey on Flight Software Frameworks for ‘New Space’ Nanosatellite Missions

description: ABSTRACT: Nanosatellite missions are becoming increasingly popular nowadays, especially because of their reduced cost. Therefore, many organizations are entering the space sector due to the paradigm shift caused by nanosatellites. Despite the reduced size of these spacecrafts, their Flight Software (FSW) complexity is not proportional to the satellite volume, thus creating a great barrier for the entrance of new players on the nanosatellite market. On the other side, there are some available frameworks that can provide mature FSW design approaches, implying in considerable reduction in software project timeframe and cost. This paper presents a comparative survey between six relevant flight software frameworks, compared according to commonly required ‘New Space’ criteria, and finally points out the most suitable one to the VCUB1 reference nanosatellite mission.
DOI: 10.6084/m9.figshare.8127932
title: Tuning Techniques Evaluation for Satellite Launch Vehicle Attitude Controllers

description: ABSTRACT: This communication presents a comparative analysis of tuning techniques for satellite launch vehicle attitude controllers. The investigated tuning techniques consist in the minimization of specific performance indexes, namely the Integral Absolute Error (IAE) index, the Integral of Time Multiplied Absolute Error (ITAE) index, the Integral Squared Error (ISE) index, and the Integral of Time Multiplied Squared Error (ITSE) index, being hence, termed optimal. By defining adequate figures of merit, relevant for evaluating the overall performance of satellite launch vehicles, and also taking into account requirements related to the physical limitations of the latter, the performance of attitude controllers tuned by the investigated techniques is compared to the one tuned by the methodology currently employed in the Brazilian Satellite Launch Vehicle (VLS), namely, the Linear Quadratic (LQ) methodology. Through simulation results, it is demonstrated that, despite sparse benefits produced by the alternative tuning techniques, in particular ITAE and ISE, the LQ methodology remains globally superior.
DOI: 10.6084/m9.figshare.8127932.v1
title: Tuning Techniques Evaluation for Satellite Launch Vehicle Attitude Controllers

description: ABSTRACT: This communication presents a comparative analysis of tuning techniques for satellite launch vehicle attitude controllers. The investigated tuning techniques consist in the minimization of specific performance indexes, namely the Integral Absolute Error (IAE) index, the Integral of Time Multiplied Absolute Error (ITAE) index, the Integral Squared Error (ISE) index, and the Integral of Time Multiplied Squared Error (ITSE) index, being hence, termed optimal. By defining adequate figures of merit, relevant for evaluating the overall performance of satellite launch vehicles, and also taking into account requirements related to the physical limitations of the latter, the performance of attitude controllers tuned by the investigated techniques is compared to the one tuned by the methodology currently employed in the Brazilian Satellite Launch Vehicle (VLS), namely, the Linear Quadratic (LQ) methodology. Through simulation results, it is demonstrated that, despite sparse benefits produced by the alternative tuning techniques, in particular ITAE and ISE, the LQ methodology remains globally superior.
DOI: 10.6084/m9.figshare.10438160
title: Numerical Simulation of a Pitching Airfoil Under Dynamic Stall of Low Reynolds Number Flow

description: ABSTRACT: In this research, viscous, unsteady and turbulent fluid flow is simulated numerically around a pitching NACA0012 airfoil in the dynamic stall area. The Navier-Stokes equations are discretized based on the finite volume method and are solved by the PIMPLE algorithm in the open source software, namely OpenFOAM. The SST k - ω model is used as the turbulence model for Low Reynolds Number flows in the order of 105. A homogenous dynamic mesh is used to reduce cell skewness of mesh to prevent non-physical oscillations in aerodynamic forces unlike previous studies. In this paper, the effects of Reynolds number, reduced frequency, oscillation amplitude and airfoil thickness on aerodynamic force coefficients and dynamic stall delay are investigated. These parameters have a significant impact on the maximum lift, drag, the ratio of aerodynamic forces and the location of dynamic stall. The most important parameters that affect the maximum lift to drag coefficient ratio and cause dynamic stall delaying are airfoil thickness and reduced frequency, respectively.
DOI: 10.6084/m9.figshare.10438160.v1
title: Numerical Simulation of a Pitching Airfoil Under Dynamic Stall of Low Reynolds Number Flow

description: ABSTRACT: In this research, viscous, unsteady and turbulent fluid flow is simulated numerically around a pitching NACA0012 airfoil in the dynamic stall area. The Navier-Stokes equations are discretized based on the finite volume method and are solved by the PIMPLE algorithm in the open source software, namely OpenFOAM. The SST k - ω model is used as the turbulence model for Low Reynolds Number flows in the order of 105. A homogenous dynamic mesh is used to reduce cell skewness of mesh to prevent non-physical oscillations in aerodynamic forces unlike previous studies. In this paper, the effects of Reynolds number, reduced frequency, oscillation amplitude and airfoil thickness on aerodynamic force coefficients and dynamic stall delay are investigated. These parameters have a significant impact on the maximum lift, drag, the ratio of aerodynamic forces and the location of dynamic stall. The most important parameters that affect the maximum lift to drag coefficient ratio and cause dynamic stall delaying are airfoil thickness and reduced frequency, respectively.