Browsing by Author "Carpenter, Joseph"

Now showing 1 - 5 of 5
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    Analysis of Combustion and Emissions Characteristics of Butanol Isomers in a Single Cylinder Heavy Duty Compression Ignition Engine
    (University of Alabama Libraries, 2025) Gray, Justin; Srinivasan, Kalyan
    Internal combustion (IC) engines are essential in transportation, agriculture, and power generation, yet they are significant contributors to harmful environmental pollutants, including nitrogen oxides (NOₓ) and particulate matter. Compression ignition (CI) engines, widely favored for their superior thermal efficiency compared to spark ignition (SI) engines, predominantly rely on diesel fuel, exacerbating environmental and health concerns due to their high NOₓ and black smoke emissions. While electrification of the medium- to heavy-duty vehicle (MHDV) sector through battery electric vehicles (BEVs) and fuel cell electric vehicles holds promise, widespread adoption is hindered by challenges such as limited driving ranges and inadequate recharging infrastructure. As a viable alternative, renewable fuels such as biobutanols have garnered attention for their potential to reduce greenhouse gas emissions and mitigate environmental impacts. Among these, n-butanol, with its oxygenated structure and favorable combustion properties, emerges as a promising candidate to replace diesel in dual-fuel CI engines. However, its low reactivity and high combustion sensitivity at standard intake temperatures present challenges for direct ignition. Dual-fuel combustion, wherein butanol is ignited using a diesel pilot injection, provides an effective solution, allowing for substantial diesel replacement without requiring powertrain modifications. This dissertation investigates the combustion characteristics of n-butanol and iso-butanol in dual-fuel CI engines, focusing on their performance relative to conventional diesel. A series of experiments were conducted under controlled conditions, including sweeps of start-of-injection (SOI) timing, pilot energy substitution (PES) ratios, rail pressure, and boost pressure. The results highlight optimal operating points for minimizing engine-out emissions such as NOₓ, particulate matter, carbon monoxide, and hydrocarbons. Key findings demonstrate that a fixed SOI of 40° before top dead center (bTDC) yields the lowest NOₓ emissions for both n- and iso-butanol. PES and rail pressure optimizations further refine the balance between emissions and combustion efficiency, while boost pressure studies reveal that lower levels enhance fuel conversion efficiency by reducing CO emissions. The results provide a comprehensive understanding of how dual-fuel combustion of butanol isomers can enhance engine performance, reduce environmental impact, and maintain operational efficiency in MHDVs. This research contributes valuable insights into the viability of n-butanol and iso-butanol as cleaner, renewable alternatives to diesel, supporting pathways to sustainable and efficient transportation solutions.
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    Confined Tube Aeration System for Aquaculture and Wastewater Industries
    (University of Alabama Libraries, 2023) Mahmud, Roohany; Woodbury, Keith
    This dissertation proposes a novel bubble-based aeration system known as 'Confined Tube Aeration (CTA)', which uses a Venturi injector as the bubble generation device and connects to a coiled pipe network after the Venturi outlet as a mixing chamber where the air-water mass transfer occurs. In this work, to analyze the effectiveness of this proposed system, several experiments are conducted, and numerical (Discrete Bubble Model) analyses are also performed to optimize the system performance. A lab-scale simple CTA system is built using a single pump, one 1-inch Venturi, and a coiled pipe network, and experiments are conducted to analyze its performance. Results from the numerical model also conform well with experimental results. Two sizes of Venturi injectors, 1-inch and 4-inch, are investigated numerically to identify their performances in a CTA system. Suction air flow, bubble size, volume fractions, and injector efficiency are also analyzed. The 4-inch injector is found to perform better in terms of oxygen transfer rate and per unit of power requirement for that specific oxygen transfer rate at standard conditions. CTA system with multiple injectors arranged in parallel connections is also studied. Experimental data show that the 2-injector system performs better than the 1-injector and 3-injector systems. When pump speed is slowed down using a VFD, the performance of the 1-injector system is greatly improved. It is also observed that, at a larger-sized CTA tube, the mass transfer efficacy is improved, and SAE also improves as the pump's hydraulic energy input remains constant. An additional benefit of this proposed technology is its simplistic design which may incur reduced installation and maintenance costs compared to the existing porous bubble diffuser and mechanical aerator system. This proposed technology can be easily retrofitted to the existing aeration system without requiring large-scale modifications of the treatment plant's aeration techniques. Additionally, the flexibility of this system to build outside of the aeration tank can be considered for retrofitting in existing treatment plants. Aquaculture can specifically benefit from this technology as it does not require a deep aeration pond for the bubbles to transfer oxygen to the water.
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    Development and Modelling of Self-Sufficient Wastewater Treatment with Near Zero Emissions
    (University of Alabama Libraries, 2022) Erguvan, Mustafa; Amini, Shahriar; University of Alabama Tuscaloosa
    A report published by the United Nations Water states that access to clean water will be a significant problem for more than 6 billion people by 2050 with population and water demand increasing. So as to mitigate water shortages, wastewater recovery with proper treatment can have an important contribution. Apart from water shortage, the water-energy-nexus (WEN) has been a key consideration owing to close connection and dependency of water and energy to each other. WEN also plays a key role in wastewater treatment plants (WWTPs), especially in developed countries, due to the fact that treatment of wastewater requires a significant amount of electricity usage. In this dissertation, two different models are developed to investigate the self-sufficiency of WWTPs in terms of energy with near-zero emissions. Chapter 1 discusses current and past studies involving the water energy nexus, wastewater treatment methods, activated sludge process, biomass conversion methods, anaerobic digestion, biogas utilization, self-sufficient WWTPs, CO2 capture techniques as well as oxy – fuel combustion processes. In the second chapter, a numerical model has been created to investigate the energetical self-sufficiency of a novel integrated energy system in a WWTP. The proposed system consists of an activated sludge process, an anaerobic digester, a Brayton cycle, and a Rankine cycle. In order to investigate energy and exergy efficiencies along with self-sufficiency ratio, several parametric studies have been conducted by varying some decision variables. While biological oxygen demand and dissolved oxygen level have been varied in the WWTP part, turbine inlet temperature, compression ratio, and preheater temperature have been used as decision variables in the power cycle. This work presented here suggests that up to 109% of the energy needed to treat wastewater can be provided using the proposed system. The optimum values and dominant parameters to achieve the highest self-sufficiency ratio have been determined as well. The highest exergy efficiencies for the WWTP, cogeneration system and overall system were found to be 58.36%, 44.59%, 36.6%, respectively. A subsequent study investigates the integration of activated sludge process, anaerobic digestion, and an oxyfuel combustion process in a WWTP in order to provide a plant which is not only energetically self-sufficient but also emission free. Several parametric studies have been conducted to investigate their effects on the thermodynamic efficiencies as well as self-sufficiency ratio. The most dominant factors were found to be wastewater strength and compression ratio. While the overall exergy efficiencies varied from 19.38 to 32.59%, self-sufficiency ratio changed from 82.29 to 132.4%. In addition, more than 95% of the CO2 has been captured and recycled in the combustion chamber. This study proves that an energetically self-sufficient WWTP with near zero emission is plausible.
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    Evaluation of the Environmental Impacts of Clean Hydrogen Production and CO2 Utilization from Carbon Capture and Direct Air Capture for Sustainable Chemical Synthesis
    (University of Alabama Libraries, 2025) Badger, Nicholas; Amini, Shahriar
    The transition to low-carbon industrial processes requires an understanding of the environmental trade-offs associated with emerging chemical conversion technologies. Life cycle assessment (LCA) provides a framework for evaluating these processes against decarbonization goals. This dissertation applies LCA to assess the impacts of methanol production, formic acid synthesis, and hydrogen production, incorporating both carbon capture (CC) and direct air capture (DAC), focused on greenhouse gas emissions. The first chapter establishes an LCA for DAC-based methanol production, showing that wind- and hydro-powered DAC lead to the most net-negative emissions of all energy sources, reaching as low as -2.53 kg CO2 eq per kg methanol. The findings highlight that DAC’s energy source determines the feasibility of CO2-derived methanol. The second chapter applies multi-objective optimization to balance competing stakeholder environmental and economic priorities relative to an LCA study. In the illustrative example, the DAC-to-methanol system is optimized between profit margin of methanol sale and climate change impacts, with the model predicting that the best business strategy is a mix of photovoltaic and wind energy cases. The third chapter examines formic acid synthesis from DAC-derived CO2 regenerated with waste heat. Results show up to a 110% global warming potential (GWP) reduction compared to fossil-based routes, but economic challenges remain, with electricity costs and CO2capture efficiency as key factors. The fourth chapter evaluates the environmental impacts of hydrogen production via gas switching reforming (GSR), a natural gas reforming process that integrates CO2 capture. The LCA results showed that compared to steam methane reforming (SMR), GSR reduces CO2 emissions by 73% and requires 94% less energy than proton exchange membrane (PEM)electrolysis. The final chapter assesses the environmental impacts of various hydrogen production routes for methanol production, showing that integrating renewable electrolysis-based hydrogen lowers emissions by 89% compared to steam methane reforming with CC, while methanol from GSR hydrogen reduces emissions by 30%.Together, these chapters provide a comprehensive assessment of decarbonization technologies, highlighting the interconnected roles of hydrogen production, DAC, carbon utilization, and synthetic fuel synthesis. This research quantifies key trade-offs, guiding the development of sustainable chemical conversion technologies to support climate change mitigation.
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    Using inverse regression models to create gray box models for industrial facilities
    (University of Alabama Libraries, 2018) Carpenter, Joseph; Woodbury, Keith A.; O'Neill, Zheng; University of Alabama Tuscaloosa
    Industrial facilities account for approximately one third of energy usage in the world, and effective energy assessments of these facilities require a reliable baseline energy model. Commercial and residential buildings are baselined with both simple change-point models and models that are more complex, such as Gaussian process and artificial neural networks, and these models are developed and tested with dense high-frequency data. However, industrial facilities are only baselined using change-point models, and data for the models are typically restricted to monthly utility bills and, therefore, generally sparse data. This investigation first compares the effectiveness of change-point models with that of Gaussian process models for baselining industrial facilities using only monthly utility billing information as data. Two case studies are presented to predict electricity usage and two case studies are presented to predict natural gas usage. Both change-point and Gaussian process models provided similar results, and both models meet the recommended NMBE and CV-RMSE from ASHRAE Guideline 14. Due to the simplicity and straight-forward equations of change-point models, they are better for regression analysis unless uncertainty is required. This study then investigates using three parameter cooling change-point regression models to determine the physical parameters, specifically overall heat transfer coefficient, surface area, and outdoor air mass flow rate of an industrial building through a simulation-based emulator. A simplified industrial building similar in size, energy usage, and physical parameters as a typical industrial facility was simulated in fifteen of the climate zones defined by ASHRAE using a whole building simulation program (i.e., EnergyPlus) to produce hourly data to illustrate and demonstrate the proposed approach. The change-point models showed poor results for finding the physical parameters using ambient air temperature as the independent variable. When using sol-air temperatures as the independent variable the change-point models were able to predict a lumped capacity of building envelope and outdoor air infiltration/ventilation within +/– 25 % error of actual (UA+ṀCP)/COP for most of the climate zones in the U.S.