Master of Science, The Ohio State University, 2020, Mechanical Engineering

The fuel economy label (window sticker) is used by every vehicle manufacturer in the United States to report fuel economy for two purposes. First, the values reported on the sticker are certified by the United States Environmental Protection Agency (EPA) and are used for certifying emissions regulations like the Corporate Average Fuel Economy (CAFE). Second, the fuel economy numbers are used by consumers to compare competing vehicles in the marketplace. These fuel economy numbers are generated through a process that involves standardized testing on a chassis dynamometer using standard drive cycles. As a result, the test requires an accurate replication of the resistive forces that a vehicle experiences in the real-world, which requires an accurate estimation of road load applied by the road and the surroundings opposing the vehicle motion. The estimation also depends on the type (aerodynamic shape, drivetrain configuration, etc.) of vehicle being tested. To get a description of road load that is as close as possible to reality, several noise factors and residuals need to be estimated as well, which forms the bulk of this thesis. Vehicle coastdown method is widely used to determine road load coefficients for testing vehicles on a chassis dynamometer for fuel economy certification. However, apart from being a time-consuming procedure for each variant in a mass production vehicle lineup, the repeatability of track coastdown testing procedure is sensitive to environmental conditions, the track surface condition as well as on the type of vehicle being tested (for example, SUVs, sedans, hybrid vehicles, manual transmissions, etc.). As a result, several attempts have been made to accurately model the coastdown road load parametrically. This thesis explores various ways in which such parametric models can be obtained and methods to minimize risks related to overfitting and collinearity of variables. Since, the vehicle's road load is dependent on several physical phenomen (open full item for complete abstract)

Committee: Giorgio Rizzoni (Advisor); Yann Guezennec (Committee Member); Adithya Jayakumar (Committee Member) Subjects: Automotive Engineering; Mechanical Engineering; Statistics

Master of Science (M.S.), University of Dayton, 2023, Aerospace Engineering

There has been a recent surge in the need for unmanned aerial vehicles (UAVs), drones, and air taxis for a variety of commercial, entertainment, and military applications. New aircraft designs put forth by companies have shown to feature multiple lift producing surfaces and rotors acting in proximity to each other. These configuration choices are primarily informed by the “compactness” requirement in the design. For this reason, configurational choices are being considered that would otherwise not receive attention. Multi-wing configurations or distributed lift systems become a compelling choice in conceptual design of future UAVs and private air vehicles (PAVs) that complements the vertical takeoff and landing capabilities of the design. For multi-wing configurations to be considered in the early conceptual design process, the reliability of traditional lower order aerodynamic methods in predicting these aerodynamic effects must be determined. However, the nature of a highly distributed lift configuration, with 10 or more lifting surfaces in close proximity, does not lend itself to rapid or accurate viscous numerical solution. Moreover, highly distributed lift configurations drive individual lifting surface Reynolds numbers into a range where viscous interactions could have a profound effect on aerodynamic performance. As such, the degree of dependence of wing-wing interactions due to viscous effects could be determined in a first iteration through a reductionist approach. Focusing specifically on the three-dimensional viscous interactions and the aerodynamic forces on the upstream and downstream wings allows for a direct determination of the importance and isolated contribution of these effects. Proximity effects due to wing-wing interactions were experimentally quantified as a function of gap and stagger across a wide range of different relative angles of attack (decalage). The proximity effects and the zone of influence at different gap and stagger locations wer (open full item for complete abstract)

Committee: Sidaard Gunasekaran (Committee Chair); Aaron Altman (Committee Member); Michael Mongin (Committee Member); Markus Rumpfkeil (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Master of Science (M.S.), University of Dayton, 2019, Aerospace Engineering

An investigation into upstream propagation of blockage effects from a bluff body at varying tunnel dynamic pressures was undertaken but ultimately linked instead to wind tunnel fan RPM for a nimiety of reasons which will be described herein. The bluff body is intended to simulate propellers tested in the Air Force Research Laboratory's (AFRL) Vertical Wind Tunnel (VWT) where blockage effects were suspected due to disagreements between experimental results and numerical predictions from various sources. It is discovered that the previous understanding of the character of the VWT's flowfield properties is lacking. Significant heat transfer occurs and test section total pressure varies significantly with changes in fan RPM. Additionally, the traditional method for measuring tunnel total pressure is unreliable at blockage ratios greater than 2.8%. At present, due to these total pressure variations, there is no method available that uses tunnel instruments to anchor test data for comparison across multiple days. Resorting to an unconventional approach, it is found that blockage effects can propagate more than 8 feet upstream of the test section lip (0.75 test section diameters); far upstream of the tunnel pitot-static probe used to measure test section conditions. It is thus concluded that incorrect tunnel dynamic pressure readings are likely and must be taken into consideration in evaluating the propeller performance accurately.

Committee: Aaron Altman Ph.D (Committee Chair); Sidaard Gunasekaran Ph.D (Committee Member); Gregory Parker Ph.D (Committee Member) Subjects: Aerospace Engineering

Master of Sciences, Case Western Reserve University, 2019, EMC - Aerospace Engineering

An octagonal supersonic nozzle and test section are developed for use with a magnetic suspension and balance system (MSBS) for testing dynamic stability in aeroshell re-entry models. A method of characteristics code is used with computational iterations to design an axisymmetric nozzle contour adjusted for boundary layer growth. Circular-to-octagonal transition schemes are developed to create a circular-to-octagonal nozzle. Computational calculations indicate the nozzles are shock free and operate at the desired Mach number. An experimental nozzle and test section are manufactured and tested for flow quality. Results indicate the nozzle is shock free and operates at a nominal Mach 2.45 +/- 0:04 as predicted in CFD

Committee: Paul Barnhart (Advisor); James T'ien (Committee Member); Yasuhiro Kamotani (Committee Member); David Davis (Committee Member) Subjects: Aerospace Engineering; Engineering; Fluid Dynamics

Master of Sciences, Case Western Reserve University, 2017, EMC - Aerospace Engineering

The feasibility of a magnetic suspension and balance system (MSBS) for testing dynamic stability of atmospheric entry capsules in the NASA GRC 225 cm2 Supersonic Wind Tunnel is investigated. The following are examined in the study: largest model size for testing in the MSBS, minimum proximity between wall and model, and analysis techniques using high-speed video images of model movement. Results indicate larger models can be tested in an axisymmetric test section and at locations closer to the nozzle exit resulting from lower boundary-layer blockage. Additionally, models contact the reflected shock from the boundary-layer at a 2.5 cm distance from centerline. Video analysis methods establish a measurement error of 0.6 degrees in pitch or yaw angle. Using these methods, a proof of concept demonstration for a one degree-of-freedom test in pitch simulating blunt body dynamic behavior is compared to ballistic range data for atmospheric entry vehicles.

Committee: Paul Barnhart Ph.D. (Advisor); Joseph Prahl Ph.D. (Committee Member); James T'ien Ph.D. (Committee Member) Subjects: Aerospace Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2012, Mechanical Engineering

Today's unmanned aerial vehicles are being utilized by numerous groups around the world for various missions. Most of the smaller vehicles that have been developed use commercially-off-the-shelf parts, and little information about the performance characteristics of the propulsion systems is available in the archival literature. In light of this, the aim of the present research was to determine the performance of various small-scale propellers in the 4.0 to 6.0 inch diameter range driven by an electric motor. An experimental test stand was designed and constructed in which the propeller/electric motor was mounted in a wind tunnel for both static and dynamic testing. Both static and dynamic results from the present experiment were compared to those from previous studies. For static testing, the coefficient of thrust, the coefficient of propeller power, and the overall efficiency, defined as the ratio of the propeller output power to the electrical input power, were plotted versus the propeller rotational speed. For dynamic testing, the rotational speed of the propeller was held constant at regular intervals while the freestream airspeed was increased from zero to the windmill state. The coefficient of thrust, the coefficient of power, the propeller efficiency and the overall efficiency were plotted versus the advance ratio for various rotational speeds. The thrust and torque were found to increase with rotational speed, propeller pitch and diameter, and decrease with airspeed. Using the present data and data from the archival and non-archival sources, it was found that the coefficient of thrust increases with propeller diameter for square propellers where D = P. The coefficient of thrust for a family of propellers (same manufacturer and application) was found to have a good correlation from static conditions to the windmill state. While the propeller efficiency was well correlated for this family of propellers, the goodness of fit parameter was improved by modifying t (open full item for complete abstract)

Committee: Scott K. Thomas PhD (Committee Chair); Haibo Dong PhD (Committee Member); Zifeng Yang PhD (Committee Member); Mitch Wolff PhD (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2009, EMC - Mechanical Engineering

In order to improve the understanding of particle vitiation effects in hypersonic propulsion test facilities, a quasi-one dimensional numerical tool was developed to efficiently model reacting particle-gas flows over a wide range of conditions. Features of this code include gas-phase finite-rate kinetics, a global porous-particle combustion model, mass, momentum and energy interactions between phases, and subsonic and supersonic particle drag and heat transfer models. The basic capabilities of this tool were validated against available data or other validated codes. To demonstrate the capabilities of the code, and to provide initial insight into the effects of various particle laden flows on ignition, a series of computations were performed for a model hypersonic propulsion test facility and scramjet. Parameters studied were simulated flight Mach number (Mach 5, 6, and 7), particle size (10, 100, and 1000 micron diameters), particle mass fraction (single particle and 1%) and particle material (alumina and graphite). For the alumina particles, it was found that the presence of particles up to 1% mass fraction had very little effect on the gas phase, even though only the 10 micron particles closely followed the gas flow velocity and temperature. With the graphite particles, the 10 micron particles were either quickly quenched, or were quickly consumed, depending on the gas temperature. As the particle size was increased to 100 microns, the particles did not quench, but were still typically consumed within the model test facility. For the 1000 micron particles, combustion was diffusion limited, so particle and gas temperature had little effect on the combustion rate. When the particle mass fraction was increased to 1%, the main change was the addition of significant heat release. In those cases where low graphite reaction rates were observed for single particles, the increase to 1% mass fraction had very little impact. Hydrogen/vitiated air ignition delay calculations (open full item for complete abstract)

Committee: Chih-Jen Sung PhD (Advisor); James Tien PhD (Committee Member); Yasuhiro Kamotani PhD (Committee Member); Steven Izen PhD (Committee Member) Subjects: Engineering; Mechanical Engineering