Mechanical Engineering Commons^™

Operational Modal Analysis And Force Characterization Of An Unstable Liquid Rocket Engine, Kevin Charles Buechele

Open Access Theses

Combustion instability has plagued the rocket industry since its beginnings. It is characterized by sustained pressure oscillations in the combustion chamber due to the coupling of natural pressure fluctuations with unsteady heat release. Typically, combustion instabilities are identified and mitigated during ground testing. Occasionally combustion instabilities do not present themselves until after a system is fielded and may only occur in a flight environment. While ground tests are heavily instrumented, operational flight data may not contain any direct measurement of the combustion forcing function. Post-event efforts to characterize anomalous combustion instabilities with existing instrumentation have had little success.

Accelerometers, which …

Age-Related Changes To The Production Of Linguistic Prosody, Daniel Richard Barnes

Open Access Theses

The production of speech prosody (the rhythm, pausing, and intonation associated with natural speech) is critical to effective communication. The current study investigated the impact of age-related changes to physiology and cognition in relation to the production of two types of linguistic prosody: lexical stress and the disambiguation of syntactically ambiguous utterances. Analyses of the acoustic correlates of stress: speech intensity (or sound-pressure level; SPL), fundamental frequency (F0), key word/phrase duration, and pause duration revealed that both young and older adults effectively use these acoustic features to signal linguistic prosody, although the relative weighting of cues differed by group. Differences …

Effect Of Aviation Fuel Type And Fuel Injection Conditions On The Spray Characteristics Of Pressure Swirl And Hybrid Air Blast Fuel Injectors, Rick Thomas Feddema

Open Access Theses

Feddema, Rick T. M.S.M.E., Purdue University, December 2013. Effect of Aviation Fuel Type and Fuel Injection Conditions on the Spray Characteristics of Pressure Swirl and Hybrid Air Blast Fuel Injectors. Major Professor: Dr. Paul E. Sojka, School of Mechanical Engineering

Spray performance of pressure swirl and hybrid air blast fuel injectors are central to combustion stability, combustor heat management, and pollutant formation in aviation gas turbine engines. Next generation aviation gas turbine engines will optimize spray atomization characteristics of the fuel injector in order to achieve engine efficiency and emissions requirements.

Fuel injector spray atomization performance is affected by the …

Characterization Of Heat And Mass Transport In Magnesium Hydride Hydrogen Storage Systems, Jennifer Anne Dadson

Open Access Theses

Hydrogen systems can provide viable alternatives for satisfying the world's energy requirements that both reduce dependency on and are more environmentally friendly than fossil fuels. For vehicular systems for example, hydrogen storage systems must have adequate gravimetric and volumetric storage capacities in addition to rapid uptake and release. Magnesium hydride shows good potential as a solid state hydrogen storage media due to its high gravimetric storage capacity of 7.6 wt% H₂; the highest of all reversible metal hydrides. Drawbacks, however, are its large reaction enthalpy of 78 kJ/mol for the desorption reaction and its low thermal conductivity of …

Autonomous Orientation And Geolocation Via Celestial Objects, Cheng Liu

Open Access Theses

Based on a hemispherical sensor geometry, a novel celestial navigation system is developed to use celestial objects to determine the absolute location and orientation information without the aid of satellites via two different approaches.

The first approach employs a hemispherical arrangement of light intensity sensors to determine the vector to the dominant light source. We present the sensing system to measure the sun vector via least squares method and achieve the application of a low-cost, small-sized solar compass. The system is shown to work well under ideal conditions but is susceptible to noise and uncertainties in some situations.

The second …

Cold Climate Field Test Analysis Of An Air-Source Heat Pump With Two-Stage Compression And Economizing, Stephen Lance Caskey

Open Access Theses

A Department of Defense project was established to conduct a field demonstration led by Purdue University with several industry partners. The technology investigated was an air-source, two-stage heat pump with closed-loop economizing. The field demonstration site was a military barracks on a National Guard base, Camp Atterbury, in southern Indiana. Two heat pumps were built at the Ray W. Herrick Laboratories and installed into two almost identical, barracks buildings. Data on the heat pump operation and building conditions were to be collected over an entire heating season. Due to complications with the system, the amount of runtime data collected from …

Rotor Blade Operational Data Analysis Methods And Applications For Health Monitoring Of Wind Turbines Using Integrated Blade Sensing, Noah Jacob Myrent

Open Access Theses

Wind energy is one of the fastest growing sources of power production in the world today. In order to extract the maximum potential amount of energy from the wind, a wind turbine's reliability must be a top priority. As utility scale wind turbines increase in size and initial capital investment cost, there also comes an increasing need to monitor the health of the turbine. Currently, most wind turbines do not incorporate blade mounted inertial sensing in addition to blade strain measurements. This approach has the potential to detect inevitable blade damage types early on so that a maintenance schedule can …

Analysis Of An Actuated Two Segment Leg Model Of Locomotion, Nikhil Vinayak Rao

Open Access Theses

Research studies on dynamic models of legged locomotion have generally focused on telescoping-type leg models. Such telescoping spring loaded inverted pendulum (SLIP) models have been able to accurately predict observed center of mass (CoM) trajectories. There have been comparatively fewer studies on dynamics of locomotion

with segmented legs. Some earlier studies on the dynamics due to leg segmentation appear straightforward. For example, a simple model with the only joint moment being due to a passive springy knee has been shown to behave similarly to a telescoping spring-mass model. However, in real-life animal locomotion, there are multiple joint-moments acting at the …

Determination Of Heat Transfer In Under-Floor Plenums In Buildings With Under-Floor Air Distribution Systems, Yan Xue

Open Access Theses

Under-Floor Air Distribution (UFAD) systems have potential advantages of energy saving and indoor air quality improvement over conventional well-mixed systems. As a ventilation strategy for buildings, a UFAD system provides conditioned air to occupied rooms through diffusers in raised floors and the air is exhausted through return grilles at the ceiling level.

Many previous researches have focused on the energy saving and air quality improvement by UFAD systems because of their high supply air temperature and room air stratification. However, few of them paid attention to the effects of the heat transfer through floor slabs on the energy performance of …

Strategy For Health Monitoring And Fault Detection In Heavy-Duty Diesel Engines, Aniketjayant Vagha

Open Access Theses

Performance tuning, health monitoring, fault diagnosis, etc. are important aspects of testing a pre-production engine out in the field. To fulfill these tasks, a robust data-based strategy for detecting anomalies in diesel engines is proposed in this work. Such a strategy separates the healthy data from outlying, anomalous trends of faulty data. The data classifier used here is based on fundamental principles of statistical learning and derived from linear discriminant analysis.

Further efforts to improve the classification performance led to the finding that steady state data makes for a more accurate classification of the working conditions of individual trucks. Hence …

Modeling Of Legged Locomotion With A Suspended Load In The Sagittal Plane, Karna P. Potwar

Open Access Theses

Walking or running while carrying loads has always been a tedious task, more so when the loads are heavy. Such a task of carrying loads not only requires extra effort but also leads to physical pain and in some cases injury. Prior studies on human locomotion with a suspended load have used models that are restricted in their DOFs and so are not able to take into account the fore aft movement in human beings. The objective of this thesis is to model the dynamics of sagittal plane center-of-mass locomotion with a suspended load and apply findings to carrying loads …

Adaptive Nonlinear Control For Autonomous Ground Vehicles, William Spencer Black

Open Access Theses

We present the background and motivation for ground vehicle autonomy, and focus on uses for space-exploration. Using a simple design example of an autonomous ground vehicle we derive the equations of motion. After providing the mathematical background for nonlinear systems and control we present two common methods for exactly linearizing nonlinear systems, feedback linearization and backstepping. We use these in combination with three adaptive control methods: model reference adaptive control, adaptive sliding mode control, and extremum-seeking model reference adaptive control. We show the performances of each combination through several simulation results. We then consider disturbances in the system, and design …

Control Of Impacting Dynamical Systems, Akhil Salunke

Open Access Theses

Impacting systems are encountered frequently in nature, and often in mechanical systems. Impacts can be undesirable in some applications, and desirable and deliberate in others. A subset of impacting systems are vibro&ndashimpact systems, wherein the impacts arise during vibrations or oscillatory behavior. Considering their potential prominence in a number of day&ndashto&ndashday applications, such vibro&ndashimpact systems have become the subject of extensive research in the past few decades. A significant number of these studies have been specifically aimed at controlling vibro&ndashimpact systems. To date, a wide variety of control algorithms have been proposed, a subset of which account for the effects …

Effect Of Exhaust Gas Recirculation And Combustible Oxygen Mass Fraction On Emission Index Of Nox For Counterflow Methane/Air Diffusion Flames, Mugdha S. Sane

Open Access Theses

Exhaust gas recirculation has been proven to be an effective method of reducing emissions of oxides of nitrogen (NOx) from internal combustion engines. The present study validates this effect through flame simulations using detailed chemistry. Counterflow methane/air diffusion flames were simulated in one dimension in physical space using GRI-Mech 3.0 detailed chemistry mechanism, thermal, and transport data. The influence of Exhaust Gas Recirculation (EGR) on the flame structure and NOx emissions was studied by selecting higher than ambient inlet temperature and by varying the composition of the oxidizer stream. The Combustible Oxygen Mass Fraction (COMF), which represents the fraction of …

Health Diagnosis Of Lithium-Ion Battery Cell Using Vibration-Based Test And Analysis, Huan Le Pham

Open Access Theses

With their superior advantages of high capacity and low percentage of self-discharge, lithium-ion batteries, which are most commonly used as power sources for hand-held electronic devices, have become the most popular choice for power storage in electric vehicles. Due to the increased potential for long life of lithium-ion batteries in vehicle applications, manufacturers are pursuing methodologies to increase the reliability of their batteries. Methods are now being developed to monitor the health of lithium-ion batteries throughout their life cycle. The work in this thesis is focused on utilizing non-destructive vibration diagnostic testing methods to monitor changes in the physical properties …

Laser Assisted Milling Of Difficult To Machine Materials, Gary Kent Hedberg

Open Access Theses

Titanium alloys are well known for their excellent strength to weight ratio and corrosion resistance and is highly sought after in the aerospace industry. Additionally, titanium alloys maintain a high biocompatibility for implants and other medical devices. However, these alloys are notorious for their poor machinability. As the demand for these alloys continue to increase, improved methods of manufacture must be explored. ^ This thesis describes Laser Assisted Milling (LAML) of Ti-6AL-4V (Ti-64) alloys, which studies localized preheating of the workpiece by a laser and characterizes the improvements to the machinability of these metals. Laser parameters are determined based on …

Turbomachine Stability And Forced Response Prediction, Leland Bert Clark

Open Access Theses

A mathematical model is developed and utilized to analyze turbomachine cascade flutter and forced response. The flutter boundary, defined as the largest value of reduced frequency at which flutter occurs for a given cascade, was evaluated for single degree of freedom torsional oscillation as well as coupled bending and torsional oscillations. The maximum amplitude of forced response in bending and torsion was also considered. The unsteady aerodynamic lift and moment coefficients were determined from unsteady aerodynamic flow models for subsonic flow, supersonic flow with a subsonic axial component and supersonic axial flow. The effect of changing the Mach number, stagger …

Experimental And Theoretical Studies On Design Calculations For Latent Heat Storage, Dieter Lindemann

Open Access Theses

Research was conducted to obtain design data of latent heat-of-fusion thermal energy storage (LHTES) devices. The devices studied utilize a porous medium (PM) to increase the effective conductivity of the storage system. Therefore the melting and freezing process is accelerated. Metal shavings and metal spheres were used as porous media and water as the phase change medium (PCM). A simple experimental method to measure the conductivity of a water-metal mixture or ice-metal mixture was applied to obtain conductivity data. These measurements can be considered fairly accurate because measured conductivity of pure water and of pure ice agreed very well with …