Mountain Scholar :: Browsing by Author "Windom, Bret, committee member"

Browsing by Author "Windom, Bret, committee member"

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Open Access
Advancing medium- and heavy-duty electric vehicle adoption models with novel natural language processing metrics
(Colorado State University. Libraries, 2024) Ouren, Fletcher, author; Bradley, Thomas H., advisor; Coburn, Timothy, committee member; Windom, Bret, committee member
The transportation sector must rapidly decarbonize to meet its emissions reduction targets. Medium- and heavy-duty decarbonization is lagging behind the light-duty industry due to technical and operational challenges and the choices made by medium- and heavy-duty fleet operators. Research investigating the procurement considerations of fleets has relied heavily on interviews and surveys, but many of these studies need higher participation rates and are difficult to generalize. To model fleet operators' decision-making priorities, this thesis applies a robust text analysis approach based on latent Dirichlet allocation and Bi-directional Encoder Representations of Transformers to two broad corpora of fleet adoption literature from academia and industry. Based on a newly developed metric, this thesis finds that the academic corpus emphasizes the importance of suitability, familiarity, norms, and brand image. These perception rankings are then passed to an agent-based model to determine how differences in perception affect adoption predictions. The results show a forecast of accelerated medium- and heavy-duty electric vehicle adoption when using the findings from the academic corpus versus the industry corpus.
Open Access
Analysis of simulated dilute anode tail-gas combustion characteristics on a CFR engine
(Colorado State University. Libraries, 2020) Balu, Alexander, author; Olsen, Daniel, advisor; Windom, Bret, committee member; Baker, Daniel, committee member
Recent innovations in metal-supported solid oxide fuel cells (MS-SOFC) have increased the longevity and reliability of fuel cells. These innovations drive the desire to create power generating systems that combine different ways of extracting power from a fuel to increase overall fuel conversion efficiency. This investigation assesses the feasibility of operating an internal combustion engine (ICE) with the anode tail-gas, which is a blend of H2, CO, CO2, H2O, and CH4, exhausted by a metal-supported solid oxide fuel cell (MS-SOFC). This engine would be used to support the fuel cell balance of plant equipment, including a compressor and expander, and produce excess electrical power. Seven variations of the expected anode tail-gas blends were determined by varying the dewpoint temperature of the fuel. In three of the test blends, CO2 replaced the water content of the fuel to allow for initial feasibility testing without the capital investment required to simulate the tail-gas with steam injection. Gas blends are tested by combining separate flows of each constituent, and combustion is tested using a Cooperative Fuel Research (CFR) engine. Compression ratio (CR), spark timing, intake manifold temperature (IMT), and boost pressure were manipulated to obtain optimal operating conditions. All test blends produced power and reached stable engine operation. Response surface method (RSM) optimization was used to experimentally optimize operating parameters and determine the maximum achievable efficiency utilizing the CFR engine. Initial feasibility testing performed on test blends with CO2 in place of water showed that all combinations successfully produced power in the engine. The mixture with the highest levels of CO2 was problematic and required an increased CR of 14.4:1, advanced timing of 40° before top dead center (BTDC), and an increased IMT of 70℃. All CO2 test blends operated at brake efficiencies ranging from 12-17% during initial testing. After the feasibility of this project was determined, a steam generator and steam flow meter were installed and used to fully simulate the anode tail-gas blends with steam injection. All fully simulated anode tail-gas blends produced power in the engine, although the blend with the most water content caused operational problems with the CFR engine test stand. These problems were caused by large amounts of water entering the engine lube oil system. RSM optimization was performed on the most viable test blends which had steam injection to 40℃ and 90℃ fuel dewpoint temperatures. During optimization, the 40℃ and 90℃ dewpoint temperature blend brake efficiency increased from 20% to 22.2%, and 17% to 22.3%, respectively. This study determined that ICE operation on dilute anode tail-gas is possible. Anode tail-gas combustion data was collected and used to inform engine and combustion models to facilitate prototype engine development for further testing.
Open Access
Application of alcohols in spark ignition engines
(Colorado State University. Libraries, 2018) Aghahossein Shirazi, Saeid, author; Reardon, Kenneth, advisor; Foust, Thomas, committee member; Dandy, David, committee member; Marchese, Anthony, committee member; Windom, Bret, committee member
Replacing petroleum fuels with sustainable biofuels is a viable option for mitigation of climate change. Alcohols are the most common biofuels worldwide and can be produced biologically from sugary, starchy and lignocellulosic biomass feedstocks. Alcohols are particularly attractive options as fuels for spark ignition engines due to the high octane values of these molecules and their positive influence on performance and emissions. In the context of the US Department of Energy's Co-Optimization of Fuels and Engines (Co-Optima) initiative, a systematic product design methodology was developed to identify alcohols that might be suitable for blending with gasoline for use in spark ignition engines. A detailed database of 943 molecules was established including all possible molecular structures of saturated linear, branched, and cyclic alcohols (C1-C10) with one hydroxyl group. An initial decision framework for removing problematic compounds was devised and applied. Next, the database and decision framework were used to evaluate alcohols suitable for blending in gasoline for spark ignition engines. Three scenarios were considered: (a) low-range (less than 15 vol%) blends with minimal constraints; (b) ideal low-range blends; and (c) high-range (greater than 40 vol%) blends. A dual-alcohol blending approach has been tested. In addition, the azeotropic volatility behavior and mixing/sooting potential of the single and dual-alcohol gasoline blends were studied by monitoring the distillation composition evolution and coupling this with results of a droplet evaporation model. Although nearly all of the work done on alcohol-gasoline blends has been on single-alcohol blends, the results of this study suggest that dual-alcohol blends can overcome many of the limitations of single-alcohol blends to provide a broader spectrum of advantaged properties. A third study focused on the possibility of replacing anhydrous ethanol fuel with hydrous ethanol at the azeotrope composition, which can result in significant energy and cost savings during production. In this collaborative study, the thermophysical properties and evaporation dynamics of a range of hydrous and anhydrous ethanol blends with gasoline were characterized. The results showed that hydrous ethanol blends have the potential to be used in current internal combustion engines as a drop-in fuel with few or no modifications.
Open Access
Autoigntion and flame speed of premixed liquefied petroleum gas in a rapid compression machine: experimental results and reduced chemical kinetic mechanism
(Colorado State University. Libraries, 2023) Slunecka, Colin, author; Olsen, Daniel, advisor; Marchese, Anthony, advisor; Windom, Bret, committee member; von Fischer, Joe, committee member
Liquefied petroleum gas (LPG) has many properties that make it an attractive alternative fuel such as lower cost than conventional fuels and an established distribution infrastructure. The development of high efficiency, spark ignited LPG engines is currently limited by engine knock and misfire. The knock and misfire limits are further complicated by the wide range of chemical reactivity in LPG, particularly in international markets. In this study, a rapid compression machine (RCM) was used to characterize the effects of variation in LPG fuel reactivity, equivalence ratio, and exhaust gas recirculation (EGR) on the autoignition and flame speeds of LPG/oxidizer/inert/EGR blends. Experiments were conducted with 100% propane and blends of propane with propene, ethane, isobutane, or n-butane. EGR was simulated with mixtures of Ar, CO2, CO, and NO at substitution percentages from 0 to 30 mass percent. Equivalence ratio was varied from 0.75 to 1.5. Ignition delay period under homogeneous autoignition conditions was measured at compressed pressures and temperatures of 23 to 25 bar and 701 to 921 K, respectively. Laminar flame speeds and apparent heat release rates (AHRR) at 24 bar with mixture temperatures of 700 K or 867 K were obtained by firing a laser ignition system into the reaction chamber shortly after compression and analyzing the propagating flame with high speed schlieren imaging. Zero-dimensional simulations of published autoignition experiments were performed using Chemkin-Pro with several detailed chemical kinetic mechanisms to determine their suitability at predicting ignition delay periods. Multiple reduced chemical kinetic mechanisms were created from the NUIGMech1.1 mechanism to determine the optimal balance between accuracy and computational efficiency for future three-dimensional, time-dependent spark-ignited engine simulations. The chosen reduction, ALPINE 153, was used to model ignition delay periods and flame speeds measured in the RCM during this study.
Open Access
Bayesian data assimilation for CFD modeling of turbulent combustion
(Colorado State University. Libraries, 2022) Wang, Yijun, author; Gao, Xinfeng, advisor; Zupanski, Milija, committee member; Guzik, Stephen, committee member; Windom, Bret, committee member; Koslovsky, Matthew, committee member
Achieving accurate CFD prediction of turbulent combustion is challenging due to the multiscale nature of the dynamical system and the need to understand the effect of the small-scale physical features. Since direct numerical simulation (DNS) is still not feasible even for today's computing power, Reynolds-averaged Navier-Stokes (RANS) or large-eddy simulation (LES) is commonly used as the practical approach for turbulent combustion modeling. Nevertheless, physical models employed by RANS or LES for describing the interactions between the turbulence, chemical kinetics, and thermodynamic properties of the fluid are often inadequate because of the uncertainties in the dynamical system, including those in the model parameters, initial and boundary conditions, and numerical methods. Understanding and reducing these uncertainties are critical to the CFD prediction of turbulence and chemical reactions. To achieve this, this dissertation is focused on the development of a Bayesian computational framework for the uncertainty estimation of the dynamical system. In the framework, a data assimilation (DA) algorithm is integrated to obtain a more accurate solution by combining the CFD model and available data. This research details the development, verification, and validation of a multi-algorithm system (referred to as DA+CFD system) that aims to increase the predictability of CFD modeling of turbulent and combusting flows. Specifically, in this research, we develop and apply a Bayesian computational framework by integrating our high-order CFD algorithm, Chord, with the maximum likelihood ensemble filter to improve the CFD prediction of turbulent combustion in complex geometry. The verified and validated system is applied to a time-evolving, reacting shear-layer mixing problem and turbulent flows in a bluff-body combustor with and without C3H8-air combustion. Results demonstrate the powerful capability of the DA+CFD system in improving our understanding of the uncertainties in model and data and the impact of data on the model. This research makes novel contributions, including (i) the development of a new alternative approach to improve the predictability of CFD modeling of turbulent combustion by applying data assimilation, (ii) the derivation of new insights on factors, such as where, what, and when data should be assimilated and thus providing potential guidance to experimental design, and (iii) the demonstration of data assimilation as a potentially powerful approach to improve CFD modeling of turbulent combustion in engineering applications and reduce the uncertainties with data. Future work will focus on a performance study of the present DA+CFD system for turbulent combustion of high Reynolds numbers and understanding the uncertainty in model parameters for developing and assessing physical models based on available information.
Open Access
Development of a methane cavity ring-down spectrometer for deployment on ground and aerial based vehicles
(Colorado State University. Libraries, 2020) Martinez, Benjamin, Jr., author; Yalin, Azer P., advisor; Yost, Dylan, committee member; Windom, Bret, committee member
Recent findings show that the oil and natural gas industry is responsible for a large portion of total anthropogenic methane (CH4) emissions. These findings have driven the need for suitable methane detection and quantification methods. Methane emissions on the scale that the oil and gas industry produce (13 Tg[CH4]/year) can cause environmental effects comparable to that of CO2 due to methane's high global warming potential. The present thesis focuses on continued developments and improvements to a laser-based methane sensor that uses the open-path cavity ring-down spectroscopy (CRDS) technique. The sensor is intended for continuous mobile monitoring of methane emissions from the oil and gas industry by deployment on ground and aerial based vehicles. Sensor performance in a range of environmental conditions is characterized and shows the feasibility of deploying the sensor in real world applications. Indoor accuracy tests were done utilizing a closed-path system and verified through comparison with a commercial analyzer. Sensor measurements compared to the commercial analyzer showed good 1:1 agreement. Allan variance studies within laboratory measurements demonstrated the sensor's high sensitivity of ~10 ppb. A heater system was designed and implemented for overall improvement in low temperature conditions. The heater system successfully improved the thermal range of the sensor to temperatures as low as 0°C. Environmental tests also showed the sensor's reliability in harsh winter conditions over a ~70-day period of continuous measurement. The sensor's methane plume detection ability and sensitivity in simulated controlled releases through vehicle deployment is demonstrated and good 1:1 agreement was found comparing against a commercial analyzer in the field. Controlled release experiments demonstrated CH4 measurements more than 400 meters away from the source at an emission rate of 0.5 g[CH4]/s. A retro-fitted closed-path cell was constructed and tested in field campaigns to reduce noise due to Mie scattering. Additional field testing with simulated controlled releases were performed to test a modified, light-weight (4.1 kg) sensor mounted on two unmanned aerial vehicle platforms. Detection of various plumes in the UAV configuration was shown to be feasible with the current mounting method. Sensitivity in UAV flights were as low as 17 ppb which demonstrated the robust opto-mechanical capabilities of the sensor.
Open Access
Dual-fuel combustion of hydrocarbon fuel droplets in lean, premixed methane/oxidizer mixtures in a rapid compression machine
(Colorado State University. Libraries, 2018) Gould, Colin M., author; Marchese, Anthony, advisor; Windom, Bret, committee member; Dandy, David, committee member
The combustion of two fuels with disparate reactivity (dual-fuel) has been shown to be an effective method for increasing fuel efficiency and reducing both fuel costs and pollutant formation in internal combustion engines. Due to recent decreases in the price of natural gas, the incentive has grown to operate engines in dual-fuel mode, where some amount of diesel is substituted with natural gas. Since natural gas is expected to remain less expensive on a per-unit-energy basis than diesel fuel for the foreseeable future, it will continue to be economically advantageous to maximize the substitution percentage of natural gas in dual-fuel engines. However, at higher natural gas substitution percentages, uncontrolled fast combustion (i.e. engine knock) can occur, which limits the load of the engine and can shorten the lifetime of engine components. Emission of unburned methane has also been shown to increase with increasing natural gas substitution percentage. Previous detailed computational engine modeling at CSU with reduced chemical kinetics and simplified spray models has captured these effects but little data are available to validate chemistry and spray models at engine-relevant conditions. In this study, a rapid compression machine (RCM) was used as a platform to provide a high-temperature/high-pressure environment to better understand the thermodynamic, transport and chemical kinetic phenomena of dual-fuel combustion. The RCM was modified to perform evaporation and combustion experiments on single n-alkane fuel droplets in gaseous inert, O2/inert and O2/CH4/inert environments. Droplet evaporation experiments were performed on C5 to C12 n-alkane droplets in inert gas to measure droplet evaporation rates at near supercritical and supercritical conditions (18 bar < P < 35 bar; 450 K < T < 850 K). The Dual-fuel droplet evaporation and combustion experiments were studied using pressure data and images collected a Schlieren optical system. In the combustion experiments, ignition delay of heptane/O2/inert was quantified at elevated pressure and temperature (27 bar < P < 38 bar; 844 K < T < 1251 K). In addition, the process of dual-fuel combustion was captured, showing two distinct ignition events.
Open Access
End-gas autoignition propensity and flame propagation rate measurements in laser-ignited rapid compression machine experiments
(Colorado State University. Libraries, 2019) Zdanowicz, Andrew, author; Marchese, Anthony, advisor; Windom, Bret, committee member; Hampson, Greg, committee member; Reardon, Ken, committee member
Knock in spark-ignited (SI) engines is initiated by autoignition and detonation in the unburned gases upstream of spark-ignited, propagating, turbulent premixed flames. Knock propensity of fuel/air mixtures is typically quantified using research octane number (RON), motor octane number (MON), or methane number (MN; for gaseous fuels), which are measured using single-cylinder, variable compression ratio engines. In this study, knock propensity of SI fuels was quantified via observations of end-gas autoignition (EGAI) in unburned gases upstream of laser-ignited, premixed flames at elevated pressures and temperatures in a rapid compression machine. Stoichiometric primary reference fuel (PRF; n-heptane/isooctane) blends of varying reactivity (50 ≤ PRF ≤ 100) were ignited using an Nd:YAG laser over a range of temperatures and pressures, all in excess of 545 K and 16.1 bar. Laser-ignition produced outwardly-propagating premixed flames. High-speed pressure measurements and schlieren images indicated the presence of EGAI. The fraction of the total heat release attributed to EGAI (i.e., EGAI fraction) varied strongly with fuel reactivity (i.e., octane number) and the time-integrated temperature in the end-gas prior to ignition. Flame propagation rates, which were measured using schlieren images, did not vary strongly with octane number but were affected by turbulence caused by variation in piston timing. Under conditions of low turbulence, measured flame propagation rates agreed with the theoretical premixed laminar flame speeds quantified by 1-D calculations performed at the same conditions. Experiments were compared to a three-dimensional CONVERGE™ model with reduced chemical kinetics. Model results accurately captured the measured flame propagation rates, as well as the variation in EGAI fraction with fuel reactivity and time-integrated end-gas temperature. Model results also revealed low-temperature heat release and hydrogen peroxide formation in the end-gas upstream of the propagating laminar flame, which increased the temperature and degree of chain branching in the end-gas and ultimately led to EGAI.
Open Access
Energetics and dynamics of flow through baffle drop shafts using physical and computational model studies
(Colorado State University. Libraries, 2023) Aluthwalage, Kasun Prabodha Sahabandu, author; Venayagamoorthy, Subhas Karan, advisor; Loc, Ho Huu, advisor; Nelson, Peter, committee member; Windom, Bret, committee member
A drop shaft is one of the main hydraulic structures that is used to convey water from higher to lower elevations while dissipating potential energy in storm water management systems, water treatment plants, and hydropower stations. Drop shafts need to be adjusted for higher discharges because of the increased urban flooding due to climate change and rapid urbanization. Traditional baffle drop shafts have limited flow capacity and are unstable due to their asymmetric nature. The novel baffle drop shaft is proposed here for larger range of flow discharges. To the author's knowledge, there are no previous studies that have thoroughly investigated the energy dissipation potential of the novel baffle drop shaft. Hence, there is a need to establish a design relationship between key parameters such as the shaft diameter, baffle spacing, and discharge to inform best design practices. A 1:10 physical model study was carried out to investigate the energy dissipation of a novel baffle drop shaft using different discharges. Pressure and velocity were measured at two locations on the baffles using low range pressure sensors (100 mbar) and an electromagnetic velocity meter. Timed averaged pressure and velocity on the baffles increased with discharge. These averaged quantities were considered to calculate global and local energy dissipation through the shaft. The global energy dissipation efficiency was calculated based on the inlet and outlet channel flow data, and was found to range from 89.6% to 91.9%. The flow regime profiles were quite similar on each baffle section of the shaft; hence, we can consider the energy dissipation in each baffle to be equivalent. Under free-flow conditions, the energy dissipation efficiency decreases as the discharge increases. Physical models are costly and time-consuming for performing parametric studies of flowthrough such structures because each and every geometric configuration needs to be constructed in the lab. Computational Fluid Dynamics (CFD) is a more feasible option to conduct an in-depth investigation of the energetics and dynamics of flow in a baffle drop shaft since it is faster and more cost-effective than a physical model study. The CFD models have been built to simulate the hydraulic behavior of baffle drop shafts using OpenFOAM. This software is adaptable for modeling diverse flow issues due to the variety of models and numerical techniques that it incorporates. A suitable turbulence model that is commonly used in CFD for modeling turbulent flows such as in drop shafts is the RANS-based realizable k- ϵ model. Mesh sensitivity analysis was also performed to establish grid independences of the solution. Benchmark geometry CFD models were calibrated using four locations in the physical model, and velocity and pressure measurements at the edge of the baffle were used for validation with remarkable agreement. A parametric study was conducted using shaft diameters (D) of 0.8 m, 0.9 m, and 1 m, six baffle spacings (h) ranging from 0.23m to 0.48 m, and baffle rotating angles (θ) of 180◦, 250◦, and 270◦. Global energy dissipation efficiency (η) ranged from 92% to 97%. The η value decreased with discharge but was higher under free flow conditions in the baffle drop shaft. The geometric parameters D, h, and θ have little influence on energy dissipation. Considering structural integrity, available space, construction costs, and maintenance costs, the baffle drop shaft needs to be optimized to achieve the desired hydraulic performance. Maximum pressure was observed at the water jet impact location close to the outer shaft wall. Air entrainment is also a significant consideration in designing baffle drop shafts because its impact is critical in applications like hydro power generation. The bulking of the flow due to air entrainment needs to be considered to evaluate the maximum flow carrying capacity of baffle drop shafts. In summary, designing baffle drop shafts requires a multi-criteria approach that is mainly dependent on the design requirements on energy dissipation, structural integrity, construction costs, air entrainment, application, and location.
Open Access
Environmental and economic evaluation of algal-based biofuels through geographically resolved process and sustainability modeling
(Colorado State University. Libraries, 2023) Quiroz, David, author; Quinn, Jason C., advisor; Windom, Bret, committee member; Willson, Bryan, committee member; Reardon, Kenneth, committee member
Advanced algal renewable fuels have been the subject of extensive research during the last decades. Their advantages over conventional biofuel feedstocks position algal biomass as a promising feedstock for the development of a sustainable and circular bioeconomy. Despite recent technological improvements, techno-economic analyses (TEAs) show that algae-derived fuels fail to be cost-competitive with petroleum fuels. Moreover, results from life-cycle assessments (LCAs) indicate declining greenhouse gas emissions when compared to petroleum fuels, but their water, health and air pollution impacts are still uncertain. This is explained by the fact that most published TEAs and LCAs of algal systems are not supported by high-resolution models and can only provide average sustainability metrics based on results from restricted data sources. These assessments often lack the resolution to correctly analyze the temporal and regional variations of biomass yields which have a direct impact on TEA and LCA metrics. Based on the current state of the field, there is a critical need to develop dynamic models that can inform sustainability assessments and consequently assist decision-making and technology development. This first part of this research work focuses on establishing the foundations for spatially explicit and temporally resolved LCA and TEA by developing and validating models that capture the thermal and biological dynamics of open algal cultivation systems. The modeling work is heavily focused on providing accurate predictions of evaporation losses in open algae raceway ponds and investigating the effects of evaporation rates on pond temperatures and growth rates. To date, this is the first modeling effort focused on predicting the evaporation losses of open algal ponds at the commercial scale. The outputs from the thermal model are then used to inform a biological algae growth model that is validated with experimental data representing the current biomass productivity potential. When integrated with hourly historical weather data, the modeling tools provide spatiotemporal mass and energy balances of the algal cultivation, dewatering, and conversion to fuel processes. These results are then leveraged with sustainability tools such as LCA and TEA to provide sustainability metrics at a high temporal and spatial scale. After developing a robust modeling framework, the modeling tool is leveraged with two distinct water LCA methods to provide a comprehensive assessment of the water impacts of algae-derived renewable diesel production across the United States. First, a water footprint analysis is conducted to understand the direct freshwater and rainwater consumption of algal cultivation and provide a framework for comparison to traditional biofuel feedstocks. The second method provides a county-level water scarcity footprint by analyzing the impact of algal systems on local water demand and availability. This assessment allows for the proper identification of potential algal sites for algal cultivation and locations where the deployment of algal systems will exacerbate local water stress. Ultimately, this research chapter provides the first holistic investigation of the water consumption and environmental water impacts of algal systems across the U.S. and establishes benchmarks for comparison to other fuels. Finally, the work comprising the third research chapter includes a novel global sustainability assessment that integrates the developed process modeling framework with regional-specific TEA and LCA. The spatially explicit TEA considers regional labor costs, construction factors, and tax rates to assess the economic viability of algal biofuels across 6,685 global locations. Similarly, a well-to-wheels LCA was performed by accounting for the regional life cycle impacts associated with electricity generation, hydrogen, and nutrient production across ten different environmental categories including health, air pollution, and climate impacts. This framework enables the identification of algal sites with optimal productivity potential, environmental impacts, and economic viability. Discussion focuses on the challenges and opportunities to reduce costs and environmental impacts of algal biofuels in various global regions.
Open Access
Evaluation of controlled end gas auto ignition with exhaust gas recirculation in a stoichiometric, spark ignited, natural gas engine
(Colorado State University. Libraries, 2020) Bayliff, Scott Michael, author; Olsen, Daniel B., advisor; Windom, Bret, committee member; Baker, Daniel, committee member
Many stationary and heavy-duty on-road natural gas fueled engines today operate under stoichiometric conditions with a three-way catalyst. The disadvantage of stoichiometric natural gas engines compared to lean-burn natural gas and diesel engines is lower efficiency, resulting primarily from lower power density and compression ratio. Exhaust gas recirculation (EGR) coupled with advanced combustion controls can enable operation with higher compression ratio and power density, which yields higher efficiency. This also results in engine operation between the limits of knock and misfire. Operation between these limits has been named controlled end gas auto-ignition (C-EGAI) and can be used to improve the brake efficiency of the engine. Various methods of cylinder pressure-based knock quantification were explored to implement C-EGAI. The indicated quantification methods are used for the implementation of a control scheme for C-EGAI with a relation to the fractional heat release due to auto-ignition. A custom EGR system was built and the effect of EGR on the performance of a stoichiometric, spark ignited, natural gas engine is evaluated. C-EGAI is implemented and the optimal parameters are determined for peak performance under EGR and C-EGAI conditions. In this study, knock detection is used for the recognition, magnitude, and location of the auto-ignition events. Cylinder pressure-based knock detection was the primary method for determining the occurrence and location of knock but was also used for implementing the ignition control scheme for controlled end gas auto-ignition. The combustion intensity metric (CIM) enabled parametric ignition timing control which allowed for the creation of a relationship between fractional heat release due to auto-ignition and CIM. Both exhaust gas recirculation and controlled end gas auto-ignition were analyzed with a cooperative fuel research (CFR) engine modified for boosted fuel/air intake. The data was interpreted to provide a proper evaluation of unique analytical methods to quantify the results of C_EGAI and characterize the live auto-ignition events. The control variables for this method of C-EGAI were optimized with EGR conditions to generate the point of peak performance on the CFR engine under stoichiometric, spark ignited, natural gas conditions.
Open Access
Expanding the knock/emissions limits for the realization of ultra-low emissions, high-efficiency heavy-duty natural gas engines
(Colorado State University. Libraries, 2023) Rodriguez Rueda, Juan Felipe, author; Olsen, Daniel B., advisor; Windom, Bret, committee member; Baker, Daniel, committee member; Quinn, Jason, committee member
Heavy-duty on-highway natural gas (NG) engines are a promising alternative to diesel engines to reduce greenhouse gas and harmful pollutant emissions if the limitations (knock and misfire) for achieving diesel-like efficiencies are addressed. This study shows innovative technologies for developing high-efficiency stoichiometric, spark-ignited (SI) natural gas engines. To develop the base knowledge required to reach the desired efficiency, a Single Cylinder Engine (SCE) is the most effective platform for acquiring reliable and repeatable data. An SCE test cell was developed using a Cummins 15-liter six-cylinder heavy-duty engine block modified to fire one cylinder (2.5-liter displacement). A Woodward Large Engine Control Module (LECM) is integrated to permit real-time advanced combustion control implementation. Fixed location of 50% burn and Controlled End Gas Auto-Ignition (C-EGAI) were used to define the ignition timing. C-EGAI allows operation with an optimized fraction of end gas auto-ignition combustion. Intake and exhaust characteristics, fuel composition, and exhaust gas recirculated substitution rate (EGR) are fully adjustable. A high-speed data acquisition system acquires in-cylinder, intake, and exhaust pressure for combustion analysis. Further development includes advanced control methodologies to maintain stable operation and higher dilution tolerance. Controlled end-gas autoignition (C-EGAI) is used as a combustion control strategy to improve efficiency. A Combustion Intensity Metric (CIM) is used for ignition control while operating the engine under C-EGAI. During the baseline testing of the developed SCE test cell, effective control of intake manifold pressure, exhaust manifold pressure, engine equivalence ratio, speed, torque, jacket water temperature, and oil temperature was demonstrated. The baseline testing shows reliable and consistent results for engine thermal efficiency, indicated mean effective pressure (IMEP), and coefficient of variance of the IMEP over a wide range of operating conditions. High Brake Thermal Efficiency (BTE) was achieved using improved hardware and a high EGR rate. Due to the correlation of CIM to the fraction of EGAI (f-EGAI), CIM was used as the reference variable to implement C-EGAI. Achieving conditions of C-EGAI allowed for the utilization of high EGR at high IMEP without inducing knock. The operation of the engine under these conditions showed peak brake thermal efficiency above 46% using an EGR ratio of 30% The work described proves the concept of using new and innovative control algorithms and CFD-optimized combustion chamber designs, allowing ultra-high efficiency and low emissions for NG ICE's heavy-duty on-road applications.
Open Access
Experimental investigation of an advanced organic Rankine vapor compression chiller
(Colorado State University. Libraries, 2022) Grauberger, Alex Michael, author; Bandhauer, Todd, advisor; Quinn, Jason, committee member; Windom, Bret, committee member; Sharvelle, Sybil, committee member
Thermally driven chilling technologies convert heat into cooling. These systems can support increasing cooling demands using waste heat in a variety of applications. Commercial thermally driven chilling technologies suffer from several implementation challenges, including high capital costs, limited equipment lifecycles, rigid working principles, and large physical formats, and thus are not implemented widely. Organic Rankine vapor compression cooling systems are a pre-commercial technology which can address the limitations of commercial alternatives. Organic Rankine vapor compression cooling systems couple an organic Rankine power generation cycle to a standard vapor compression chilling cycle. These systems can use benign, pressurized refrigerants as working fluids which allows for reduced heat exchanger costs over commercial thermally driven alternatives without environmentally impactful fugitive emissions. Refrigerants are released from cooling technologies during charging, leaking connections, and/or improper/unregulated disposal. Furthermore, the coupling of the two individual cycles allows the use of high-speed compression and expansion machinery as well as multiple methods of heat recuperation. High-speed fluid machinery and heat recuperation strategies reduce the format and cost of the technology while simultaneously improving the longevity and operational flexibility. Current organic Rankine vapor compression efforts are limited from an absence of experimental validation. This study aims to fill this research gap through investigating a prototype organic Rankine vapor compression system enhanced with a high-speed, centrifugal turbo-compressor, sub cycle and cross cycle heat recuperation, compact heat exchanger technologies, and benign, next-generation refrigerants at an industry-relevant scale of 300 kW. A thermodynamic model was created and a system heat-to-cooling coefficient of performance (COP) of 0.65 was simulated with 91°C liquid waste heat, 30°C condenser coolant, and 7°C chilled water delivery where a 5°C inlet to outlet temperature difference was specified for each stream. A full-scale prototype was fabricated and tested following standards for performance rating of commercial water chilling technologies to validate the performance simulation. Experimental testing of the prototype yielded a thermal COP of 0.56 and a cooling duty of 264 kW under its baseline operating conditions. The baseline test conditions were identical to the simulated conditions except the temperature difference across the condensers, which was 1.7°C greater due to a 25.6% lower condenser coolant flowrate. The lower condenser coolant flowrate, a vapor compression condenser refrigerant outlet vapor mass quality of 6.2% instead of the modeled 1°C of subcooling, and elevated system pressure losses limited the efficiency and cooling duty of the prototype over the simulated values. A scenario analysis on the test data was complete to show the prototype could surpass the simulated performance prediction with a COP of 0.66 at 300 kW of cooling if the operational limitations associated with prototype were corrected. This performance is competitive with commercial single-effect absorption systems and is possible because the turbomachinery efficiencies were high. The isentropic efficiency values for the turbine and compressor were 76.7% and 84.8% respectively at the baseline conditions during experimentation and the two devices had a 100% power transmission efficiency within experimental error. Following the assessment of baseline performance, operational characteristics of the technology were quantified at off-design boundary conditions and normalized to those of the baseline to identify performance trends. It was shown that prototype thermal performance generally improved with increasing waste heat supply temperature, increasing chilled water delivery temperature, decreasing condenser coolant temperature, and decreasing chilling duty. These trends are consistent with performance simulations in literature. However, performance improvements at off-design operation were often challenged by variations in turbine and compressor efficiency as well as the efficacy of heat recuperation strategies. Such changes to component performance characteristics at varying boundary conditions have not been previously quantified in practice and, thus, have historically been neglected in analytical investigations of organic Rankine vapor compression systems. Understanding the off-design component performance characteristics allows for the creation of validated organic Rankine vapor compression performance models. Such models will be critical to understanding the true energy savings potential of organic Rankine vapor compression systems as they are continuously investigated.
Open Access
From waste to energy: a techno-economic analysis and life cycle analysis of liquid biochemical production from wet wastes through enhanced anaerobic digestion
(Colorado State University. Libraries, 2022) Soliman, Abdallah, author; Quinn, Jason C., advisor; Reardon, Kenneth, committee member; Windom, Bret, committee member
Wet wastes such as manure and food wastes present problems due to disposal costs and environmental impacts. Low value products and methane leaks limit the sustainability and viability of current anaerobic digestion for treatment of wet waste. Electrochemically enhanced conversion of wet wastes diverts carbon from low-value methane into volatile fatty acids that are subsequently upgraded to improve anaerobic digestion sustainability and generate biochemicals which are seamlessly compatible with the current infrastructure. A chain elongation pathway and a bioconversion pathway are used to produce caproic acid and n-butanol, respectively. Techno-economic analysis and life cycle assessment are used to demonstrate the economic and environmental viability of the technology. The economic analysis generates market competitive minimum selling prices of $1.05 per kg for the caproic acid pathway and $2.25 per kg for the n-butanol pathway. The baseline environmental analysis yields an environmentally unfavorable GWP of 72.1 g CO2-eq·MJcaproic acid-1 for the chain elongation pathway whereas the GWP of the bioconversion pathway (24.0 g CO2-eq·MJn-butanol-1) qualifies it as a renewable fuel under the RFS program. Using scenario and sensitivity analyses, critical research areas were highlighted to guide future work and improve the performance and sustainability of the technology.
Open Access
Geographically-resolved evaluation of economic and environmental services from renewable diesel derived from attached algae flow-ways across the United States
(Colorado State University. Libraries, 2022) Banks, Austin Brice, author; Quinn, Jason, advisor; Peebles, Christie, committee member; Windom, Bret, committee member
Harmful algal blooms (HABs) are becoming more invasive and ever more prevalent due to rises in nitrogen and phosphorus pollution in watersheds. Nitrogen and phosphorus leakages primarily occur from non-point sources like agricultural runoff, but also point sources like wastewater treatment facilities. Previous efforts to reduce nitrogen and phosphorus loadings and mitigate HABs have largely been ineffective despite investment in nutrient reduction technologies. As the population grows, our consumption and dispersal of nitrogen and phosphorus is expected to compound, and HABs will continue to wreak havoc on our aquatic ecosystems. Herein, we introduce a novel biorefinery that taps into the vast sources of nitrogen and phosphorus in watersheds while simultaneously producing biofuels. Contaminated water is diverted to flow over attached algae systems, feeding native, periphytic algal cultures and scrubbing excessive nutrients from the water. Hydrothermal liquefaction converts the algal biomass into renewable fuels, nutrient-rich fertilizers, and carbonaceous char. The evaluation of the biorefinery concept is done through integrating geographically-resolved growth modeling with nutrient resource availability based on all Hydrologic Unit Code-8 (HUC8) in the contiguous US which is integrated into sustainability models to evaluate the economic and environmental impact of the proposed system. Life cycle analysis results demonstrate a global warming potential of 25 g CO2-eq MJ-1, a eutrophication potential of 1.3*10-5 kg N eq MJ-1, and a net energy ratio 0.33 of MJ MJ-1 in the Santa Monica Bay, CA subbasin. Technoeconomic assessments found that renewable diesel can be produced for $1.20 per cubic decimeter (dm-3) or $4.56 per gallon of gasoline equivalent (GGE-1) under optimal conditions in the Santa Monica Bay, CA subbasin, with results dramatically varying across the US. Water quality trading was also incorporated into the analysis. Using modest nutrient credit values of $4.5 per kg of total nitrogen (kg-TN-1) and $4.5 per kg total phosphorus (kg-TP-1) removed enabled the renewable diesel to achieve parity with conventional diesel, $1.01 dm-3 ($3.84 GGE-1) in the Santa Monica Bay, CA subbasin. A more aggressive credit value of $45 kg-TN-1 and $45 kg-TP-1 made the price of the renewable diesel negative in Santa Monica Bay, CA, roughly $-4.45 dm-3 ($-16.8 GGE-1), and across the Midwest, the Gulf of Mexico, and major cities on the East and West Coast. This means the value of the service that the algae provide in remediating watersheds covers all costs of the system to the point where the renewable diesel represents a product with negligible value. These results highlight a path forward for mitigating eutrophication while also creating a sustainable fuel. Discussion focuses on the service that large-scale deployment of attached algae flow-ways provide to remediate excessive nutrients from watersheds and generate biofuels at a cost-effective price point when water quality trading credits are incorporated into the system economics.
Open Access
Heat transfer enhancement in two-phase microchannel heat exchangers for high heat flux electronics
(Colorado State University. Libraries, 2020) Hoke, Jensen, author; Bandhauer, Todd, advisor; Windom, Bret, committee member; Venayagamoorthy, Karan, committee member
Laser diodes are semiconductor devices that emit high intensity light with a small spectral bandwidth when a forward voltage is applied. Laser diodes have a high electrical to light conversion efficiency which can be greater than 50%. These robust, high efficiency laser sources are used in medical and manufacturing fields and, if their power can be increased, show promise in inertial confinement fusion and defense applications. Individual diode emitters are arrayed into bars with a footprint of 1 mm by 10 mm to increase their light output power. These bars are further combined into arrays with the light emitting edges stacked close together. As the spacing in these arrays are reduced to increase brightness, thermal management becomes the limiting factor for each bar. State of the art diode arrays can have heat fluxes exceeding 1 kW cm-2. Effective thermal management strategies are key because the diode's output wavelength, bandwidth, efficiency and lifetime are temperature dependent. Commercially available high powered laser diode arrays are traditionally cooled using a single-phase fluid passing through conduction coupled copper-tungsten channels. These heat exchangers have high thermal resistances which require the coolant to be significantly subcooled before entering the device. High working fluid flow rates are required to reduce thermal gradients in the diode bars and working fluid conditioning is required to reduce corrosion in the cooling plates. Many of these issues can be addressed by cooling the diodes with a two-phase working fluid in a corrosion resistant, silicon microchannel heat exchanger. The high heat transfer coefficients associated with flow boiling, as well as the high surface area to volume ratios in microchannel arrays allow the working fluid temperature to be much closer to that of the diode which reduces the cooling load on a system level. Additionally, as heat is added to a two-phase fluid, there is virtually no change in temperature. Therefore, the working fluid flow rate can be much lower than a comparable single-phase heat exchanger, which reduces pump work. However, using a two-phase working fluid presents its own unique set of challenges. This work presents a novel approach to increasing the effective critical heat flux and reducing thermal resistance in an array of 125 high aspect ratio silicon microchannels (40 µm × 200 µm) subjected to heat fluxes up to 1.27 kW cm-2. R134a is used as the two-phase working fluid and outlet vapor qualities up to 80.7% are reported. The silicon heat exchangers are manufactured using a DRIE MEMS process that allows fine control over feature sizes. The performance of traditional plain walls is compared to a novel sawtooth structuring pattern that increases available heat transfer area by 41% and provides bubble nucleation sites. A 17% decrease in thermal resistance is reported for one of the area enhancement schemes and critical heat flux is increased in both area enhanced parts. A thermal FEA model is used to determine heat transfer coefficients and local heat fluxes within the test section. This model is used to investigate alternate patterning schemes. An adjustment to the Bertsch two-phase heat transfer coefficient is also suggested for smaller microchannels geometries and higher heat fluxes. Examination of the model results show that performance increase observed in the area enhanced test sections is driven by an increase in bubble nucleation sites. The additional area available for heat transfer has little effect because reduction of heat flux at the fluid wall interface reduces two-phase heat transfer coefficients. This effect is driven by the relative importance of nucleate boiling in these small channels.
Open Access
Improved catalyst regeneration process to increase poison removal and improve performance recovery
(Colorado State University. Libraries, 2021) Bauza, Rodrigo, author; Olsen, Daniel, advisor; Windom, Bret, committee member; Johnson, Jerry, committee member
Internal combustion engines are partly responsible for increasing amounts of carbon dioxide, nitrogen, carbon monoxide, hydrocarbons, aldehydes, and particulate matter in the atmosphere. These emissions have detrimental health effects on humans and negatively impact the environment by contributing to the formation of acid rain and photochemical smog. Large bore two-stroke natural gas engines are used commonly for power generation, and in order to meet the National Emissions Standards for Hazardous Air Pollutants set by the Environmental Protection Agency, engine manufacturers commonly select oxidation catalysts as the exhaust aftertreatment of choice. These catalysts degrade over time due to thermal, chemical, and mechanical reasons. Lubrication oil makes its way through the combustion chamber and onto the catalyst, degrading the unit. To estimate the degradation rate of the units and to find the best restoration method, two identical alumina-platinum oxidation catalysts were used in a dual setting, combining a field degradation engine and a laboratory testing engine. The lubrication oil from the cylinder makes its way to the catalyst and creates a layer of volatile hydrocarbons at the very surface that reduces the surface area and catalytic activity of the unit. Moreover, the additives from the oil, such as sulfur, phosphorus, and zinc actively poison the crystallites and minimize the reduction efficiency of the units. The wash-coat is turned into a powder and analyzed, showing sulfur is the most prevalent poison, constituting approximately 8.97% of the wash-coat when the units are degraded. Phosphorus constitutes roughly 2.55%, and zinc makes up less than 0.50% of the wash-coat and is the most superficial poison. Sulfur is not only the most prevalent but also penetrates deeper into the wash-coat than the rest of the poisons, but phosphorus is seen to interact chemically with the platinum crystallites, suggesting a stronger de-activation by phosphorus. Platinum is more active in its metallic form, and the catalyst of interest improves in performance after being chemically reduced in a 5% hydrogen purge at 450°C, indicating the platinum crystallites were oxidized in the aging process. The units were aged, then restored with the industry standard washing procedure, then aged again until reaching non-compliance with the emissions standards set by the Environmental Protection Agency, and then restored a second time with a modified version of the industry standard washing process. In order to find the best restoring process, variations of the industry standard chemical wash are tested, and the result proves unsuccessful to modify the washing procedure. Moreover, the industry standard washing process is enhanced by adding two new steps, carbon baking and crystallite restoration. The combination of both baking and washing is tested with elemental and performance analysis. The laboratory elemental analysis suggests the baking restoration steps should be added before washing, which is in agreement with the performance bench testing results. The levels of sulfur and phosphorus are respectively brought down to 0.692% and 0.689% after applying the modified restoration process to the units, and zinc is reduced to 0.048% of the wash-coat. However, the slipstream performance results with real exhaust from a Cummins QSK19G do not fully agree with the addition of the baking steps to the industry washing standard restoration, likely because the combined restoration was tested on a catalyst that had been previously washed and re-aged, which is known in the industry to produce less successful restoring results. The catalysts can be aged and restored two to three times before the reduction efficiency increase from the restoration is not great enough to financially motivate catalyst users to restore the units instead of replacing them.
Open Access
Modernizing automation in industrial control/cyber physical systems through the system engineering lifecycle
(Colorado State University. Libraries, 2021) Ault, Trevor J., author; Bradley, Thomas, advisor; Golicic, Susan, committee member; Windom, Bret, committee member; Chong, Edwin, committee member
The systems engineering process seeks to develop systems beginning from a need and ending with an operational system. The systems engineering framework is acknowledged as an effective tool for building complex systems, but this research seeks an expansion in scope and emphasis to include more detailed methods for managing, operating, and upgrading existing subsystems when they are challenged by obsolescence, functional degradation, and upgrades/commissioning. System development from a blank slate is often the default for the systems engineering field, but often an individual subsystem (in this case studied here, the automation system) must undergo upgrades much sooner than the rest of the system because it can no longer meet its functional requirements due to obsolescence. Partial system upgrades can be difficult to conceive and execute for a complex industrial system, but the fundamentals of the system engineering process can be adapted to meet the requirements for maintenance of an industrial control/cyber physical system in practice. Cyber physical systems are defined as systems that are enabled by interactions between computers and physical systems. Computers and other automation components that control the physical processes are considered part of this system. This dissertation seeks to engineer industrial automation systems to enable identification of obsolescence in cyber physical systems, simulation testing of the automation subsystems before/during upgrade, and integrity testing of alarms and automation after completion. By integrating some key aspects of the systems engineering approach into operations and maintenance activities for large-scale industrial cyber physical systems, this research develops and applies 1) novel risk-based approaches for managing obsolescence, 2) novel techniques for simulation of automation controls for fast commissioning in the field, and 3) an automatic alarm configuration engineering and management tool. These systems engineering developments are applied over the course of 5 years of continuous operation and 14 large upgrades to automation systems in the process industry (gas processing, chemical, power generation). The results of this application illustrate consistent improvement in the management, upgrading, and engineering of industrial automation systems. Metrics of system performance used to quantify the value of the proposed methodological innovations include commonly used metrics such as number of alarms, cost, and schedule improvement. For the research contribution which develops novel obsolescence identification and replacement strategies, the results show that using a modified risk management approach for automation and cyber physical systems that can quickly identify components that required upgrade. The results indicate a reduction of roughly 70% of reactive replacements due to obsolescence after the major upgrade and a 24% reduction in unplanned downtime due to part failure during normal operations. For the research contribution illustrating that automation system simulation can confirm that the upgraded subsystems meet functional requirements during upgrade on continuously running sites, results are similarly positive. A new metric is developed to normalize the cost of simulations per system which measures the amount of simulation inputs (I/O) divided by cost. Results show that using the proposed simulation tools can reduce the cost of simulation by 40% on a normalized basis and reduce alarms for a system by 55% during system startup and early operations. Lastly, an audit system was developed for the automation systems to ensure that the subsystem continued to meet functional requirements after the upgrade. Deploying the audit system for alarm configuration was successful in that it resulted in no unauthorized alarm changes after the subsystem upgrade. It also resulted in improved alarm performance at sites since causes of alarm deterioration were eliminated. Results show that these added controls resulted in 52% fewer alarms (post implementation) and the elimination of alarm flooding (periods where more than 10 alarms occur in under 10 minutes). The goal of this dissertation is to document innovative means to develop systems engineering towards operational and maintenance upgrades for industrial automation systems and to provide examples of ways this process can be applied. The values of the proposed engineering methods were validated through its application to over a dozen industrial sites of varying processes and complexity. While this research focused on heavy process industries, the process for identifying obsolete components and making major subsystems upgrades can also be applied to a broad set of industries and systems and provide research contributions to both the fields of industrial automation and system engineering.
Open Access
On intensity change and the effects of shortwave radiation on tropical cyclone rainbands
(Colorado State University. Libraries, 2020) Trabing, Benjamin, author; Bell, Michael, advisor; Chiu, Christine, committee member; Knaff, John, committee member; Windom, Bret, committee member; van den Heever, Sue, committee member
In this dissertation, the effects of shortwave radiation and the diurnal cycle of radiation on tropical cyclone rainbands are explored. In order to improve short term forecasts of tropical cyclone intensity and size, a better understanding of the processes that affect the inner rainbands of tropical cyclones is warranted. In Chapter 2, the distribution of intensity forecast errors from the National Hurricane Center (NHC) are characterized in the Atlantic and East Pacific basins. Analysis of the forecast error distributions and the relationship between the thermodynamic environments in which those errors occur leads to the conclusion that improvements need to be made to our understanding and prediction of inner-core processes, particularly to predict rapid changes in intensification and weakening. The effect of shortwave radiation on tropical cyclone rainbands during an eyewall replacement cycle (ERC) is examined in Chapter 3. In the idealized experiments we vary the amount of incoming solar radiation to change the magnitude of the response and assess the sensitivity of the timing of the ERC. Shortwave radiation has a delaying effect on the ERC primarily through its modifications of the distribution of convective and stratiform heating profiles in the rainbands. Shortwave radiation reduces the amount and strength of convective heating profiles by stabilizing the thermodynamic profiles and reducing convective available potential energy. The idealized modeling study shows that the coupled interactions between the shortwave radiation and the cloud microphysics is at the crux of the experiment and requires further verification by observations. Chapter 4 explores the diurnal cycle of convection in the rainbands of Typhoon Kong-rey (2018) using a suite of novel observations from the Propagation of Intraseasonal Tropical Oscillations (PISTON) field campaign. Convection in the rainbands of Typhoon Kong-rey had a more pronounced diurnal cycle compared to the rest of PISTON where shortwave heating in the upper-levels increased the static stability during the day. Pronounced diurnal oscillations in the brightness temperatures, which are out of phase with those documented in Dunion et al. (2014), are found to be coupled with outflow jets below the tropopause and radially outward propagating convective rainbands approximately ∼6 hours later. In Chapter 5 an attempt is made to simulate the diurnal variations in the rainbands of Typhoon Kong-rey that were observed during PISTON. Four experiments are conducted using commonly used shortwave radiation and cloud microphysics schemes to determine the extent to which previous and future studies can reproduce diurnal variability. Of the four experiments, only one realistically simulated Typhoon Kong-rey's rapid intensification and none of the experiments reproduce the diurnal oscillations in the infrared brightness temperatures. The interactions between the shortwave radiation and cloud microphysics schemes cause variations in the distribution of convective and stratiform pre- cipitation in the inner-rainbands and the extent of upper-level clouds that can largely explain the differences in the intensity. Sensitivity tests suggest that more work on documenting radiation-microphysics interactions is needed to improve model forecasts of inner-rainband structure.
Open Access
Physical validation of predictive acceleration control on a parallel hybrid electric vehicle
(Colorado State University. Libraries, 2022) White, Samantha M., author; Bradley, Thomas, advisor; Quinn, Jason, committee member; Daily, Jeremy, committee member; Windom, Bret, committee member
Previous research has been conducted towards the development of predictive control strategies for Hybrid Electric Vehicles (HEVs). These methods have been shown to be effective in reducing fuel consumption in simulation, but no physical validation has been conducted. This is likely due to the fundamental "curses" of dynamic programming mostly the "curse of dimensionality" wherein the run-time needed to generate the optimal solution renders the method unfit as a real-time control. Predictive Acceleration Event (PAE) control combats the run-time issues associated with dynamic programming based control methods by pre-computing the optimal solutions for common Acceleration Events (AEs). This method was physically implemented on a 2019 Toyota Tacoma that was converted into a Parallel-3 (P3) HEV with limited information on the vehicle, including a reduced access to the vehicle's Controller Area Network (CAN) bus. Results from on-track testing indicate a Fuel Economy (FE) improvement in the range of 7% is possible to achieve using PAE control in the real world. To the author's knowledge this is the first time that this type of testing has ever been implemented on a vehicle in the real world.