The enhanced growth of ignition kernels through modulation of nanosecond pulsed high-frequency discharges is investigated quantitatively in a reactive flow. High-frequency discharge and new notions of rotational temperature coupling per subsequent pulse ( < 30 kHz) existing within the breakdown regime have led to the discovery of the "fully-recoupled" regime. The evolution of flame kernels is observed in a methane-air mixture at an equivalence ratio of 0.6 flowing at 12.5 m/s, with an interelectrode gap of 1.7 mm. Energy deposition into the flow per pulse was previously found to be 2.9 ± 0.23 mJ/pulse, where the number of pulses per effective modulation type was 10 ( ≈ 30mJ). By holding A.P. (average power) constant through each pulse train, the CPRF (Constant Pulse Repetition Frequency) partially-coupled and decoupled regimes were directly compared against the MPRF (Modulated Pulse Repetition Frequency) fully-recoupled regime through kernel growth measurements via high-speed schlieren. It was found that by utilizing the inter-pulse coupling of rotational temperatures through modulating the PRF (Pulse Repetition Frequency), the ignition probability and kernel area increased as to create the fully-recoupled regime as a new form of ignition optimization.

Shock tubes are as close to an ideal reactor as most modern experiments can attain to examine chemical kinetics. As reaction temperatures drop, homogeneous combustion within a shock tube begins to exhibit inhomogeneous modes, which in a typical Hydrogen-Oxygen system are ex- pressed as deflagration to detonation transition. Experimental results of such a system in the Uni- versity of Central Florida's low-pressure shock tube have been collected through end and side-wall imaging to analyze flame structure and chemical kinetics. The purpose of this work is to con- duct a baselining of these results using both chemical and computational fluid dynamics modeling. The model will use the Siemens STAR-CCM+ computational fluid dynamics software in order to accurately simulate the system. A seven-step reaction mechanism will be used to accurately capture initialization, propagation, and termination of the combustion within an implicit unsteady, three-dimensional, direct eddy simulation solution on a well-conditioned mesh. The end goal of this study is to create a lightweight model of hydrogen-oxygen combustion with a shock tube for baselining purposes. Both a two- and three- dimensional model were applied in this effort. The simulation results indicate good conditioning and agreement with the experimental results, although some combustion phenomena are not captured as well as a higher fidelity, significantly more computationally expensive model would.

With reusability being a novel design parameter for liquid rocket engines (LRE), the need to lower internal wall temperatures for an increased engine longevity is a desired outcome. One of the mechanisms that has been effectively implemented is the use of high aspect ratio cooling channels (HARCC) to promote fin-like effects from internal cooling channel sidewalls. In the gas turbine industry, the use of wedge turbulators has gained recognition for its heat augmentation properties with relatively low pressure drop penalty. In an ideal case, LRE's could adopt the wedge turbulator cooling technique to enhance the benefits of HARCC with minimal penalty; however, the relationship between these two cooling schemes in a LRE environment is relatively unknown. A conjugate heat transfer analysis is performed on wedge turbulator features on various channels of differing aspect ratios. The boundary and initial conditions of the validation channel geometry is taken from a simulated 1 MN Vulcain engine high-aspect ratio cooling channel environment. After smooth walled channels are validated from a previous study, backward facing wedge turbulators are introduced into the channel in order to observe and analyze heat augmentation and pressure drop effects across various aspect ratios.

With rising labor costs and high consumer demand, economic conditions are becoming increasingly favorable for mechanization in the strawberry industry. However, virtually all strawberry crops are still picked by hand because the harvesting process is very challenging to automate, and strawberries are susceptible to bruising. For these reasons, the development of a harvester which can avoid damaging the fruit is of interest. Conventional designs for robotic grippers are less than ideal, as precise positioning or force feedback capabilities are required to reduce the risk of bruising. As an alternative, a novel "camera-in-hand" gripper design is presented which effectively avoids bruising by containing the fruit in a spherical shell before pulling away from the plant. Additionally, a corresponding visual servo control system is also presented for positioning the gripper with an XYZ table. Camera feedback paired with a color-based filtering method identifies and locates strawberries of sufficient size and ripeness. If a strawberry is found, alignment errors between the gripper and the target fruit are updated through a discrete Kalman filter for noise reduction. Validation of the autonomous harvester consisting of the gripper, XYZ table, and associated visual servoing software is conducted via field tests on the Florida radiance cultivar grown in plasticulture.

Early detection of the crop diseases helps to prevent failure in the amount and the quality of the production. In agricultural robotics, the idea of a disease detection robot is a fresh and an innovative hot-button topic. The exclusion of the diseased parts from the strawberry plants for further analyses is one of the main tasks of a recently developed strawberry robot. To this purpose, the handling mechanism in the robot needs to achieve an accurate manipulation task to reach the target. Reaching, cutting and storing the diseased leaf are challenging and delicate processes during the procedure of the handling mechanism operation in the field. The manipulation task of the mechanism is succeeded when the inverse kinematic relations from workspace to joint space are defined properly. The inverse kinematic analysis is usually subjected to the restrictions due to the limitations in mechanical design of the mechanism, hardware components and operation environment of the robots as well as the morphology of the target. This study proposes a set of analytical algorithms to solve the inverse kinematics problem of the handling mechanism under certain constraints. First, proposed analytical approach is based on the calculation of the joint variables by solving only the 3D position information of the target since the output from image processing algorithms of vision subsystem in the ground robot is only the location of the diseased point. The position of target point is the only output from vision subsystem and this data will be given as an input to the proposed algorithms. Second, the mechanism has certain restrictions on its geometrical construction and the joint actuators' capacity. Hence, these restrictions limit the range of joint variables to be solved. Due to sudden and unpredicted nature of field conditions, the quickness of handling mechanism inverse kinematics solution's execution has a vital effect on the success of the picking task of the robot. Another essential factor is to use the battery life of the robot effectively, by minimizing energy consumption. Therefore, the effectiveness of the proposed algorithm is decided by comparing the developed performance indices of consumed energy and CPU time cost via numerical solution namely, a nonlinear constrained optimization method under same restrictions of inverse kinematics problem. Performance of both algorithms is observed by the simulations in MATLAB® and laboratory set-up experiments.

A major challenge faced by automobile manufacturers is to achieve reduction of particulate emission to acceptable standards, as the emission standards become more and more stringent. One of the ecologically friendly options to reduce emissions is to develop external combustion in a steam engine as a replacement of the internal combustion engine. There are multiple factors, other than pollution that need to be considered for developing a substitute for Internal Combustion Engine, like specific power, throttle response, torque speed curve, fuel consumption and refueling infrastructure. External combustion in a steam engine seems to be a bright idea, for a cleaner and more environment friendly alternative to the IC engine that can satisfy the multiple technology requirements mentioned. One way of performing external heterogeneous combustion is to use porous ceramic media, which is a modern and innovative technique, used in many practical applications. The heterogeneous combustion inside ceramic porous media provides numerous advantages, as the ceramic, acts as a regenerator that distributes heat from the flue gases to the upstream reactants, resulting in the extended flammability limits of the reactants. The heat exchanger design is the major challenge in developing an external combustion engine because of the space, such systems consume in an automobile. The goal of the research is to develop a compact and efficient heat exchanger for the application. The proposed research uses natural gas as a fuel that is mixed with air for combustion and the generated flue gases are fed to a heat exchanger to generate superheated system for performing engine work to the vehicle. The performed research is focused on designing and modeling of the boiler heat exchanger section. The justification for selection of working fluid and power plant technology is presented as part of the research, where the proposed system consists of an Air and Flue Gas Path and a Water and Steam Path. Models are developed for coupled thermal and fluid analysis of a heat exchanger, consisting of three sections. The first section converts water to a saturated liquid. The second portion consists of a section where water is converted to saturated steam. The third section is the superheater, where saturated steam is converted to superheated steam. The Finite Element Model is appropriately meshed and boundary conditions set up to solve the mass, momentum and energy conservation equations. The k-epsilon model is implemented to take care of turbulence. Analytical calculations following the established codes and standards are also executed to develop the design.

An in-house reflectometer/interferometer has been built to investigate the varying curvature and thickness profiles in the contact line region of air, acetone, iso-octane, ethanol, and water on various types of substrates. Light intensity measurements were obtained using our reflectometer/interferomter and then analyzed in MATLAB to produce thickness and curvature profiles. The apparatus is based on the principle of a reflectometer, consisting of different optical elements, probe, light source, and spectrometer. Our reflectometer/interferomter takes measurements in the UV-Vis-IR range (200nm-1000nm). This range is achieved by using a light source that has both a deuterium light (190nm-800nm), a tungsten halogen light (400nm-1100nm), a Metal-Core Printed Circuit Board LED (800nm-1000nm) and a Metal-Core Printed Circuit board cold white LED (400nm-800nm, 6500 K). A UV-VIS-IR spectrometer reads the light response after light is focused on the region of interest. Then a CCD camera (2448x2048) records the profiles for image analyzing interferometry. The readings were then validated based on results in the literature and studies with cylindrical lens samples.

The chemical kinetics of 1,3-butadiene (1,3-C4H6) are important because 1,3-butadiene is a major intermediate during the combustion of real fuels. However, there is only limited information on the chemical kinetics of 1,3-butadiene combustion, which has applications in several combustion schemes that are currently being developed, including spark-assisted homogeneous charge compression ignition and fuel reformate exhaust gas recirculation. In the present work, the ignition delay times of 1,3-butadiene mixtures has been investigated using pressure data. Oxidation of 1,3-butadiene/oxygen mixtures diluted in argon or nitrogen at equivalence ratios (Φ) of 0.3 behind reflected shock waves has been studied at temperatures ranging from 1100 to 1300K and at pressures ranging from 1 to 2atm. Reaction progress was monitored by recording concentration time-histories of 1,3-butadiene and OH* radical at a location 2cm from the end wall of a 13.4m long shock tube with an inner diameter of 14cm. 1,3-Butadiene concentration time-histories were measured by absorption spectroscopy at 10.5µm from the P14 line of a tunable CO2 gas laser. OH* production was measured by recording emission around 306.5nm with a pre-amplified gallium phosphide detector and a bandpass filter. Ignition delay times were also determined from the OH* concentration time-histories. The measured concentration time-histories and ignition delay times were compared with two chemical kinetics models. The measured time-histories and ignition delay times provide targets for the refinement of chemical kinetic models at the studied conditions.

The meniscus region of a thin film is known to have high heat transfer properties due to high evaporation rates and activation of latent heat. The region known as the thin film meniscus (δfilm lt& 2 µm ) can account for more than half of the total heat transfer of a droplet or film. This study focuses on the potential elongation and curvature amplification of the thin film meniscus region by the implementation of a layer of high hydrogen bonding (hydrogel) film on which the liquid meniscus is built. Forced wetting via liquid propagation though this hydrogel layer in the radial direction increases the surface area of the film. By analyzing the mass flux of liquid lost through evaporation and using both spectroscopic and optical methods to obtain the curvature of the film, relationships between hydrogel thickness and the resulting mass flux were made. Isothermal and steady state assumptions were used to relate hydrogel thickness layers to meniscus curvature, evaporative mass flux, and overall heat transfer coefficients. The experimental results demonstrate, that steady state conditions are achievable with small percentage change in film profile over time. These results are promising toward the addition of the hydrogel coatings and further advancements in heat piping and high heat flux cooling systems for micro electronic devices.

As commercial space travel expands, the need for specialized instrumentation to ensure the safety of crew and cargo becomes increasingly necessary. Both the Federal Aviation Administration (FAA) and pioneers in the space tourism industry have expressed an interest in a robust, low cost, and low power consumption sensor to measure atmospheric composition aboard spacecraft. To achieve this goal a time-resolved NDIR absorption sensor that measures transient levels of gaseous carbon dioxide (CO2) and carbon monoxide (CO) was developed. The developed sensor has a wide range of applications applicable to the growing needs of industry, from monitoring CO and CO2 levels for crew cabin safety to early detection of gas leaks, fires, or other atmospheric altering events. A proof of concept, lab-bench dependent sensor has been previously developed to begin to target the needs of this industry. This thesis discusses the expansion and evolution from this previous lab-bench dependent design into a portable, autonomous, and remote sensor that is able to withstand the harsh environmental conditions required for its intended operation in near space. The sensor incorporates compact high-efficiency LEDs that transmit in the 3-5µm wavelength range. These LEDs are further centered at 4.2µm and 4.7µm by the use of narrow band-pass filters to measure the spectral absorbance features of CO2 and CO respectively. Active and passive thermal management of all components is achieved via thermal electric coolers (TEC) and thermal sinks to enable sensor temperature control in applicable low convection environments. To accomplish the needs for a stand-alone sensor, remote and autonomous operation is achieved via the inclusion of a real-time embedded controller with configurable FPGA/IO modules that autonomously handle thermal management, LED operation, and signal data acquisition/storage. Initial instrument validation was completed by utilizing a thermal vacuum chamber with a testable temperature and pressure range from standard temperature and pressure (STP) down to -22°F and 8mbar. Variable measurements of CO/CO2/N2 gas mixtures were supplied via mass flow controllers to the sensor's gas cell in order to determine various key metrics of sensor operation. The culmination of the sensor's operational validation was via its flight aboard a NASA funded Louisiana State University (LSU) high-altitude balloon. This flight reached an altitude of 123,546ft with ambient temperatures and static pressures ranging from 910mbar and 53°F at ground level to .68mbar and -54°F at float altitude. A total mission time of 18h:09m:30s was reached with a total float time of 15h:08m:54s. Successful sensor operation was achieved throughout the entire mission which demonstrates the applicability, adaptability, and relevance of the technologies discussed here for space applications.