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Conceptual Design, Material, and Structural Optimization of a Naval Fighter Nose Landing Gear for the Estimated Static Loads

SAE International Journal of Aerospace

Anna University Chennai - Regional Office Tiruchirappalli, India-Swagata Paul, K. Suresh
Senior Grade Assistant Professor, India-C. Senthilkumar
  • Journal Article
  • 01-12-02-0009
Published 2019-12-13 by SAE International in United States
The Naval Nose Landing Gear (NLG) structural assembly consists of components with complex structural geometry and critical functionalities. The landing gear components are subjected to high static and dynamic loads, so they must be appropriately designed, dimensioned, and made by materials with mechanical characteristics that meet high strength, stiffness, and less weight requirements. This article contributes to the shape, size, and material optimization for the NLG of a supersonic naval aircraft for the estimated static loads. The estimated modal frequency values of the NLG assembly using Finite Element Analysis (FEA) software were compared with available Ground Vibration Test data of an aircraft to literally prove the accuracy and suitability of finite element (FE) model that can be used for any further analysis. Static structural analysis was performed for the critical landing load cases, and the Reserve Factor (RF) values of the landing gear components were calculated to determine their static strength capacity. Iterations including shape, size, and material optimization were done in the NLG to reduce the mass with the required strength characteristics.
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Process Regulations and Mechanism of WEDM of Combustor Material

SAE International Journal of Aerospace

National Institute of Technology, Kurukshetra, India-Bhupinder Singh, Joy Prakash Misra
  • Journal Article
  • 01-12-01-0004
Published 2019-06-07 by SAE International in United States
This study discusses the experimental investigation on WEDM of combustor material (i.e., nimonic 263). Experimentation has been executed by varying pulse-on time (Ton), pulse-off time (Toff), peak current (Ip), and spark gap voltage (Sv). Material removal rate (MRR), surface roughness (SR), and wire wear rate (WWR) are employed as process performance characteristics. Experiments are designed as per the box-Behnken design technique. Parametric optimization has also been performed using response surface methodology. Besides this, field-emission scanning electron microscope (FE-SEM) and an optical microscope are utilized to characterize WEDMed and worn-out wire surfaces. It is observed that both surfaces contain micro-cracks, craters, spherical droplets, and a lump of debris. Furthermore, the mechanism of recast layer formation has been critically evaluated to apprehend a better understanding of the technique. The key features of the experimental procedure are also highlighted.
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Multicriteria Optimization, Sensitivity Analysis, and Prediction of Bond Characteristics of Vacuum Diffusion Bonded Aero Engine Ti6Al4V Alloy Joints

SAE International Journal of Aerospace

Annamalai University, India-T. Pragatheswaran, S. Rajakumar, V. Balasubramanian, S. Kavitha
Materials Group, Gas Turbine Research Establishment (GTRE), India-Vijay Petley, Shweta Verma
  • Journal Article
  • 01-12-02-0008
Published 2019-12-13 by SAE International in United States
Joining titanium (Ti) alloys with conventional processes is difficult due to their complex structural properties and ability of phase transformation. Concerning all the difficulties, diffusion bonding is considered as an appropriate process for joining Ti alloys. Ti6Al4V, which is an α+β alloy widely used for aero engine component manufacturing, is diffusion bonded in this investigation. The diffusion bonding process parameters such as bonding temperature, bonding pressure, and holding time were optimized to achieve desired bonding characteristics such as shear strength, bonding strength, bonding ratio, and thickness ratio using response surface methodology (RSM). Empirical relationships were developed for the prediction of the bond characteristics, and sensitivity analysis was performed to determine the increment and decrement tendency of the shear strength with respect to the bonding parameters. Various criteria were applied to achieve the desired bond characteristics and their effects; optimum values and limits were evaluated through graphical and numerical optimization. The predicted and experimented results are validated and found that they are in good agreement with each other. The microstructural examination and X-ray diffraction (XRD) analysis…
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Stall Mitigation and Lift Enhancement of NACA 0012 with Triangle-Shaped Surface Protrusion at a Reynolds Number of 105

SAE International Journal of Aerospace

University of Petroleum and Energy Studies, India-Aslesha Bodavula, Rajesh Yadav, Ugur Guven
  • Journal Article
  • 01-12-02-0007
Published 2019-11-21 by SAE International in United States
Transient numerical simulations are conducted over a NACA 0012 airfoil with triangular protrusions at a Reynolds number (Re) of 100000 using the γ-Reθ transition Shear Stress Transport (SST) turbulence model. Protrusions of heights 0.5%c, 1%c, and 2%c are placed at one of the three locations, viz, the leading edge (LE), 5%c on the suction surface, and 5%c on the pressure surface, while the angle of attack (AOA) is varied between 0° and 20°. Results obtained from the time-averaged solution of the unsteady Navier-Stokes equation indicate that the smaller protrusion placed at 5%c on the suction surface improves the post-stall lift coefficient by up to 59%, without altering the pre-stall characteristics. The improvement in time-averaged lift coefficients comes with enhanced flow unsteadiness due to vigorous vortex shedding. For a given protrusion height, the vortex shedding frequency decreases as the AOA is increased, while the amplitude of fluctuations in lift coefficient increases as the protrusion height is increased or as the AOA is increased. Nevertheless, mitigation of static stall phenomena is observed for most configurations investigated, and…
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Improving the Modelling of Dissociating Hydrogen Nozzles

SAE International Journal of Aerospace

Prince Mohammad Bin Fahd University, Saudi Arabia Ton Duc Thang University, Vietnam-Alberto Boretti
  • Journal Article
  • 01-12-02-0006
Published 2019-11-21 by SAE International in United States
While the design of nozzles for diatomic gases is very well established and covered by published works, the case of a diatomic gas dissociating to monatomic along a nozzle is a novel subject that needs a proper mathematical description. These novel studies are relevant to the definition of nozzles for gas-core Nuclear Thermal Rockets (NTR) that are receiving increased attention for the potential advantages they may deliver versus current generation rockets. The article thus reviews the design of the nozzles of gas-core NTR that use hydrogen as the propellant. Propellant temperatures are expected to reach 9,000-15,000 K. Above 1500 K, hydrogen begins to dissociate at low pressures, and around 3000 K dissociation also occurs at high pressures. At a given temperature, the lower the gas pressure the more molecules dissociate, and H2 → H + H. The properties of the gas are a function of the mass fractions of diatomic and monatomic hydrogen x H2 and x H = 1 − x H2. Dissociation influences the molecular weight of the gas and its heat capacity,…
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Enhancing Flight Path Separation to Reduce Bird Strikes with Ultraviolet Radiation

SAE International Journal of Aerospace

Lite Enterprises, USA-Donald J. Ronning
  • Journal Article
  • 01-12-02-0005
Published 2019-10-29 by SAE International in United States
In the autumn of 2018, a pilot study using a prototype (PAR46 size) landing light that incorporated ultraviolet light emitting diodes (UVLEDs) was attached on a one-quarter scale remote controlled (RC) plane. The plane was flown in the direction of birds to measure their behavioral response to the approaching plane with landing lights either turned ON or OFF. Data were collected from multiple sources including cameras on the plane and the ground and a bird radar unit to measure the flight path separation between the plane and the birds. The purpose of this study was to determine the effectiveness of using UVLEDs integrated into a PAR46 landing light to trigger bird avoidance behavioral responses that would increase flight path separation to reduce the incidence of bird strikes. The findings showed the mean distance of the avoidance response was statistically significantly greater when the PAR46 landing light with UVLEDs was turned ON versus OFF. Field test data were used to create a three-variable model based upon recent neuroscience research corresponding to visual image capture, retinal neural…
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Design and Experiment on Aircraft Electromechanical Actuator Fan at Different Altitudes and Rotational Speeds

SAE International Journal of Aerospace

Air Force Research Laboratory, USA-Q.H. Leland
North Carolina A&T State University, USA-E. Gyasi, J.P. Kizito
  • Journal Article
  • 01-12-01-0003
Published 2019-06-07 by SAE International in United States
For electromechanical actuators (EMAs) and electronic devices cooling on aircraft, there is a need to study cooling fan performance at various altitudes from sea level to 12,000 m where the ambient pressure varies from 1 to 0.2 atm. As fan static pressure head is proportional to air density, the fan’s rotational speed has to be increased significantly to compensate for the low ambient pressure of 0.2 atm at the altitude of 12,000 m. To evaluate fan performance for EMA cooling, a high-rotational-speed, commercially available fan made by Ametek with a diameter of ~82 mm and ~3 m3/min zero-load open cooling flow rate when operating at 20,000 rpm was chosen as the baseline. According to fan scaling laws, this fan was expected to meet the cooling needs for an EMA when operating at 0.2 atm. Using a closed flow loop, the performance of the fan operating in the above ambient pressure range and at a rotational speed between 15,000 and 30,000 rpm was evaluated. Unexpectedly, at 0.2 atm, the Ametek fan was able to produce only…
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High Power-Density, High Efficiency, Mechanically Assisted, Turbocharged Direct-Injection Jet-Ignition Engines for Unmanned Aerial Vehicles

SAE International Journal of Aerospace

Ton Duc Thang University, Vietnam-Alberto Boretti
  • Journal Article
  • 01-12-01-0002
Published 2019-05-02 by SAE International in United States
More than a decade ago, we proposed combined use of direct injection (DI) and jet ignition (JI) to produce high efficiency, high power-density, positive-ignition (PI), lean burn stratified, internal combustion engines (ICEs). Adopting this concept, the latest FIA (Fédération Internationale de l’Automobile) F1 engines, which are electrically assisted, turbocharged, directly injected, jet ignited, gasoline engines and work lean stratified in a highly boosted environment, have delivered peak power fuel conversion efficiencies well above 46%, with specific power densities more than 340 kW/liter. The concept, further evolved, is here presented for unmanned aerial vehicle (UAV) applications. Results of simulations for a new DI JI ICE with rotary valve, being super-turbocharged and having gasoline or methanol as working fuel, show the opportunity to achieve even larger power densities, up to 430 kW/liter, while delivering a near-constant torque and, consequently, a nearly linear power curve over a wide range of speeds.
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Landing Response Analysis on High-Performance Aircraft* Using Estimated Touchdown States

SAE International Journal of Aerospace

Aeronautical Development Agency, India-P.S. Suresh, Niranjan Kumar Sura
Indian Institute of Technology Madras, India-K. Shankar
  • Journal Article
  • 01-12-01-0001
Published 2019-04-08 by SAE International in United States
A novel use of state estimation methods as initial input for a landing response analysis is proposed in this work. Six degrees of freedom (DOF) non-linear landing response model is conceived by considering longitudinal dynamics of aircraft as a rigid body with heave-and-pitch motions coupled onto a bicycle landing gear† arrangement. The DOF for each landing gear consist of vertical and longitudinal motions of un-sprung mass, considering strut bending flexibility. The measurement data for state estimation is obtained for three landing cases using non-linear flight mechanics model interfaced with pilot-in-loop simulation. State estimation methods such as Upper Diagonal Adaptive Extended Kalman Filter (UD-AEKF) with fuzzy-based adaptive tuning and Un-scented Kalman Filter (UKF) were adapted for landing maneuver problem. On the basis of estimation error metrics, aircraft state from UKF is considered during onset of touchdown. These estimated states are used as an initial condition for the six DOF non-linear landing response model, numerically solved in Matlab environment. The dynamic responses such as displacement, velocity, and acceleration for the aircraft and the loads on landing gears…
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Mapping of Fuel Anti-Knock Requirements for a Small Remotely Piloted Aircraft Engine

SAE International Journal of Aerospace

Air Force Institute of Technology-Joseph K. Ausserer, Marc D. Polanka
Air Force Research Laboratory-Paul Litke
  • Journal Article
  • 2016-32-0045
Published 2016-11-08 by SAE International in United States
Small remotely piloted aircraft (10-25 kg) powered by internal combustion engines typically operate on motor gasoline, which has an anti-knock index (AKI) of >80. To comply with the single-battlefield-fuel initiative in DoD Directive 4140.25, interest has been increasing in converting the 1-10 kW power plants in the aforementioned size class to run on lower AKI fuels such as diesel and JP-8, which have AKIs of ~20. It has been speculated that the higher losses (short-circuiting, incomplete combustion, heat transfer) that cause these engines to have lower efficiencies than their conventional-scale counterparts may also relax the fuel-AKI requirements of the engines. To investigate that idea, the fuel-AKI requirement of a 3W-55i engine was mapped and compared to that of the engine on the manufacturer-recommended 98 octane number (ON) fuel. The knock limit was established to be a peak-pressure rise rate of 5 bar/deg or a maximum amplitude of pressure oscillations of 5 bar for 1% of 400 consecutive cycles, whichever was more conservative. The 3W-55i engine was able to develop full power at all speeds above…
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