Large commercial aircraft by design typically are not capable of transporting maximum fuel capacity and maximum payload simultaneously. Maximum payload range remains less than maximum range. When an aircraft is operated on a route that may exceed its maximum payload range capability, environmental conditions can vary the payload capability by as much as 20%. An airline’s commercial department needs to know of such restrictions well in advance, to restrict booking levels accordingly. Current forecasting approaches use monthly average performance, at, typically, the 85% probability level, to determine such payload capability. Such an approach can be overly restrictive in an industry where yields are marginal, resulting in sellable seats remaining empty. The analysis of operational flight plans for a particular ultra-long routing revealed that trip fuel requirements are near exclusively predictable by the average wind component for a given route, at a correlation of over 98%. For this to hold, the route must be primarily influenced by global weather patterns rather than localised weather phenomena. To improve on the current monthly stepped approach the average wind components were modelled through a sinusoidal function, reflecting the annual repetitiveness of weather patterns. Long term changes in weather patterns were also considered. Monte Carlo simulation principles were then applied to model the variance around the mean predicted by the sinusoidal function. Monte Carlo simulation was also used to model expected payload demand. The resulting forecasting model thus combines supply with demand, allowing the risk of demand exceeding supply to be assessed on a daily basis. Payload restrictions can then be imposed accordingly, to reduce the risk of demand exceeding supply to a required risk level, if required. With payload demand varying from day of week to seasonally, restricting payload only became necessary in rare cases, except for one particular demand peak period where supply was also most restricted by adverse wind conditions. Repeated application of the forecasting model as the day of flight approaches minimises the risk of seats not sold, respectively of passengers denied boarding. / Thesis (PhD)--University of Pretoria, 2019. / Mechanical and Aeronautical Engineering / PhD / Unrestricted

Flame stabilization behavior is experimentally investigated at engine relevant conditions using an optical sensor imaging system. Optical imaging systems can provide insight into local engine behavior as opposed to measurements with devices such as flowmeters. Two facilities are utilized to examine premixed flame combustion stabilized by bluff body flame holders at both atmospheric and elevated pressures. C2* and CH* chemiluminescence signals are recorded on a four-band imaging system to calibrate the sensor intensity ratio of C2*/CH* to the flame equivalence ratio. Tracking this ratio across flame position can provide local information concerning flow disturbances and other combustor instabilities. Several fuels (methane, propane, and liquid Jet-A) are tested to examine the change in chemiluminescence ratios that can be found in industrial applications. The calibrations are obtained across a wide range of equivalence ratios (0.6-1.4) and for pressures of 1 and 5 bar. Methane flames showed very low C2* signal value in lean and stoichiometric flames, resulting in non-monotonically increasing calibration curves. Propane flames had a monotonic calibration curve, attributed to greater C2* signal intensity. The Jet-A-air flames also had non-monotonically increasing calibrations at 1 bar, but a monotonic curve at elevated pressure. These calibrations are then applied to the average C2*/CH* intensity ratio images to yield maps of flame equivalence ratio. Downstream variation in the equivalence ratio of the unconfined facility is attributed to air entrainment, while in the weaker signal is thought to be a function of the local flame properties.

Remotely operated aerial vehicles such as quadcopters and drones have been, and continue to be, used extensively by military personnel, industry, and civilians alike. Current research into unsteady flapping mechanisms has been primarily concerned with the heaving and pitching motion of rigid foils. The purpose of this thesis is to investigate how a dynamically morphing foil affects the fluid-structure interactions of unsteady flapping locomotion as measured by lift, drag, and vorticity. The effects of non-dimensional heaving amplitude and reduced frequency are studied using force sensor and Particle Image Velocimetry (PIV) measurements. Two reduced frequencies are tested: one in the unsteady range, κ=0.105, and one in the highly unsteady range, κ=0.209. Two morphing modes were investigated: spanwise twisting in the direction of upward pitch (Mode A), and spanwise twisting in the direction of downward pitch (Mode B). The effects of changing reduced frequency and nondimensional heaving amplitude were explored for each morphing mode. Force sensor measurements showed that Mode A recovered some of the lift that is usually lost during the upstroke of flapping locomotion. Additionally, Mode A maintained a near-constant lift coefficient during the transition between downstroke and upstroke, suggesting a more stable form of locomotion. PIV results showed that Mode A limits circulation and leading-edge vortex (LEV) growth during the downstroke, keeping Cd ≈ 0 at the cost of reduced lift. By contrast, PIV results showed that Mode B increases the circulation during the downstroke, resulting in large increases in both lift and drag coefficients. Force sensor data showed that this effect on lift is reversed during the upstroke, where Mode B causes negative lift. The effects of each morphing mode is caused by changes in shear layer velocity that occur as a result of spanwise twisting. The twisting performed by Mode A reduces the effective angle of attack, resulting in a reduced shear layer velocity and lower circulation. The twisting performed by Mode B does the exact opposite, increasing the effective angle of attack and consequently increasing the shear layer velocity and circulation.

Corrosion presents an inherent challenge in the safe and effective use of metallic aerospace structures for extended periods of time. Progress in the fundamental understanding of corrosion initiation and propagation under stress requires a multi-scale approach that leverages experiments to develop predictive models. Although there exists a large amount of research results tracking the corrosive processes of anodic dissolution and hydrogen embrittlement, the amount of available data and modeling of the micro-scale initiation of corrosion is sparse. This work leverages a suite of characterization techniques to systematically analyze an aerospace grade aluminum alloy AA7075-T6, providing important multi-scale data for correlation with overall corrosion progression. Samples were exposed to 3.5% NaCl solution at various exposure times under loading with a micro-tensile system. Optical microscopy, Raman spectroscopy and Energy Dispersive X-ray Analysis provided spatial maps of the visual and chemical alloy signatures before, during, and after failure, to analyze and track the progression of corrosion. An experimental setup for in-situ Digital Image Correlation (DIC) was developed to provide strain maps to study local concentrations around corrosion pits and quantify the impact on the material tensile performance. The material morphology and composition from these measurements identified localized oxide formations at a high spatial resolution that can be used to quantify the corrosion rates. Meanwhile, in-situ DIC measurements provided results showing stress concentrations formed by the corrosion pits and the reduced mechanical performance with exposure. The results demonstrate that multiple factors affect corrosion susceptibility and material deterioration, and highlight the need to overcome experimental challenges in quantifying these factors distinctly. This work demonstrates the capacity for highly detailed analysis of corrosion initiation and propagation in affected alloys using the processes outlined in the systematic study. The outcomes provide a pathway to address methods for maintaining the integrity of these alloys and extending their lifespan.

The chemistry of propane continues to play a pivotal role in today's power production technologies. As reliance on natural gas expands as greener cleaner fuels are sought throughout the world, especially as countries are attempting to transition away from traditional coal and crude-oil fired plants towards solar, wind, and hydro-electric sources. Natural gas, often seen as a bridge fuel between these two competing ends, has been in the recent past and for the foreseeable future will continue to play an important role in the energy sector. Among the components of natural gas, propane plays a key role in the chemistry for both pyrolysis and combustion. While the composition of natural gas is primarily dominated by the presence of methane, the heavier hydrocarbons especially propane dominates the chemistry of reactions. Thus, developing a healthy understanding of the pyrolysis of propane will aid in deepening insights into the chemistry that dominates that of natural gas. The pyrolysis of propane was carried out behind reflected shockwaves at elevated temperatures. Species concentration histories were recorded simultaneously using a broadband mid-infrared optical parametric oscillator to probe the reacting flows. Concentration histories for methane, acetylene, ethylene, ethane, propene, and propane were collected over a range of pressures and temperatures (pressures of ~4 to 5 atm, and temperatures of 1105 to 1304 K). These species were chosen due to there prevalence in the computational and theoretical framework of the pyrolysis of propane, but have been difficult to experimentally measure due to overlapping molecular absorption spectra.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautical Engineering, 1926. / Includes bibliographical references (leaves 13-14, first group). / by N.J. Medvedeff and N.N. Sinitzin. / M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Aeronautical Engineering, 1940. / Microfiche copy available in Barker. MIT copy bound with: Effect of balancing of freed elevator on longitudinal damping / Robert Knott Prince, Jr., Ernest Gunther Chilton. 1940. / Includes bibliographical references (leaf [36]). / by Ernesto T. Mendoza. / B.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautical Engineering, 1935. / Microfiche copy available in Barker. / Includes bibliographical references (leaves 48-49). / by Hideo Tsukada. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautical Engineering, 1949. / by Milton Beilock. / M.S.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Aeronautical Engineering, 1936. / Microfiche copy available in Barker. / Vita. / Includes bibliographical references (leaves 96-98). / by Robert K. Mueller. / Sc.D.