Browsing by Author "Olsen, Daniel, committee member"

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Cattle manure characteristics in relation to manure accumulation period and seasonal impacts in the intermountain west
(Colorado State University. Libraries, 2023) Bhowmik, Priya R., author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Olsen, Daniel, committee member
Anaerobic digestion (AD) of organic waste has been studied and implemented in practice more recently than ever. AD is used to produce biogas, which mainly consists of methane gas that has multiple purposes. Arguably the most important purpose methane gas has is that it is a renewable energy source. Organic waste that can serve as feedstock for AD ranges from food waste to animal waste, including manure. There are limited application of AD technology to process beef cattle manure compared to other manure sources due to factors such as method of collection processes (i.e., scraped on dry lots) and inconsistent methane gas produced due to varied conditions. This study focuses on beef cattle manure from the intermountain west, home to many cattle feedlots producing millions of tons of manure a year. Beef cattle feedlots pens typically have a base of compacted manure with no roof covering the pen. With no roof over the beef cattle feedlots and low collection frequency, the manure is exposed to seasonal change with varying weather conditions and often contains low water content and high inorganic material compared to other animal feeding operation manure. To improve the methane production of beef cattle manure in AD processes, more information is needed on the quality of beef cattle manure over varying collection frequency and seasons. The objective of this research is to determine biochemical methane potential (BMP) for differing accumulation time periods and seasonal impact. Four sample collections were conducted at one concentrated animal feeding operation (CAFO) from different months with different seasonal effects. For each sample collection, different manure accumulation periods were selected ranging from 7 to 90-day old manure. For each accumulation period, three cattle pens were selected based on the similar number of cattle and same feed. All manure was collected from each pen and was weighed with subsequent testing for characteristics. Based on the total solids (TS) from each pen in each manure accumulation period the composite sample was created for the manure accumulation period which was tested for BMP. A second manure collection technique was used due to complications with collecting lower manure accumulation periods with the first collection technique such as an uneven surface of the pen. The second technique applied land surveying one singular pen for a 10- and 20-day manure accumulation period to attempt to only collect newly deposited manure over the accumulation period. The BMP data is expressed as the volume of methane (CH4) produced per unit of volatile solids (VS) added, typically represented as mL CH4/ g VS feedstock. VS is the portion of the material that is organic and for this study in terms of volatile mass per dry mass. The sample collections from this study BMP results ranged from 200-276 mL CH4/ g VS feedstock. A literature review was conducted comparing over 13 studies that tested beef manure in AD. Results from this study were above the average of the literature review which was 160 mL CH4/ g VS feedstock. One of the sample collections occurred in May, which was the only data which represented a parallel trend between manure accumulation periods and BMP results, with BMP decreasing with longer accumulation periods. The May sample collection produced the highest measured ultimate BMP and was considered the most precise manure collection. Statically different trends were not observed for samples collected over seasons, leading to inconclusive results on seasonal impacts on BMP. The land surveying technique for manure collection resulted in variable quality manure, which emphasized the struggle of replication of manure collected and the possibility of obtaining only the desired manure accumulation period without obtaining any of the manure pad. Overall, results indicated the potential for increased methane production potential for more frequently collected manure at beef feedlots. However, the study also indicated that more frequent collection of only freshly deposited manure would be difficult to implement in practice.
Open Access
Characterization of direct injected propane and iso-octane at engine-like conditions in a high-pressure spray chamber
(Colorado State University. Libraries, 2022) Windell, Brye Thomas, author; Windom, Bret C., advisor; Olsen, Daniel, committee member; Venayagamoorthy, Subhas Karan, committee member
This thesis focuses on the recommission, modification, and testing of a high-pressure spray chamber (HPSC) and its role in aiding the experimental and numerical examination of direct injection (DI) propane at various engine-like conditions to address fundamental limitations of achieving near diesel efficiencies in heavy duty on-road liquified petroleum gas (LPG) engines. The HPSC was reconstructed and is capable of incorporating optical diagnostic techniques including high-speed Schlieren and planar Mie scattering imaging. High-speed Schlieren was used to characterize the global spray morphology and vapor phase regions while planar Mie scattering allowed for individual plume resolution providing insights into the liquid regions of the spray. These optical imaging techniques unveiled propane's spray propagation was fed by flash boiling effects, spray collapse, and high degree of vaporization, unlike iso-octane. This resulted in a direct proportionality of propane's penetration length to temperature, an inversely proportional relationship to ambient pressure, and a direct proportionality to injection pressure. Contrary to propane, iso-octane's spray morphology exhibited minor changes as temperatures and pressures were varied. Due to these unique effects, flash boiling, spray collapse, and high degree of vaporization, propane is classified as an unconventional spray, dissimilar to iso-octane's spray morphology. Experimental testing provided corrections to numerical models that were developed to reproduce the under-expanded jet dynamics. The numerical modeling results were found to be sensitive to cone and inclusion angles. The current work serves as preliminary results for an experimental validation campaign which aid in the numerical model development for future heavy duty on-road LPG engines.
Open Access
Characterizing fuel reactivity in advanced internal combustion engines
(Colorado State University. Libraries, 2014) Baumgardner, Marc E., author; Marchese, Anthony J., advisor; Reardon, Ken, committee member; Olsen, Daniel, committee member; Gao, Xinfeng, committee member
The urgent need to increase efficiency and reduce exhaust emissions from internal combustion engines has resulted in an increased interest in alternative combustion modes. Premixed or partially premixed compression ignition modes, such as homogeneous-charge compression ignition (HCCI), reactivity-controlled compression ignition (RCCI) and multi-zone stratified compression ignition (MSCI) have been a particular focus because of their potential to deliver enhanced fuel efficiency and meet exhaust emissions mandates without the addition of costly after-treatment technologies. For HCCI and other single fuel, partially premixed compression ignition schemes such as MSCI, many studies have shown that fuels with characteristics intermediate between gasoline and diesel fuel are necessary. Many researchers have shown, however, that existing industry metrics such as Octane Number and Cetane Number are insufficient to represent fuel ignition characteristics for advanced engine combustion modes. In light of the poor performance of traditional metrics, new methods have been proposed to try and better characterize, order, and rank fuels used in HCCI operation. However, studies have since shown that when a broad array of fuels are considered, these recent metrics fail to adequately define a characteristic HCCI fuel index. Described in this work is an analysis of fuel reactivity in traditional and advanced internal combustion engines. Firstly, conventional engine regimes are broken down to their basic components, providing a framework for investigating the context of fuel reactivity. This analysis allows a novel equation to be formulated which links the historic metrics of Octane Number and Cetane Number. As part of this analysis a parameter, the knock length, is developed which explains the underlying principles of the Research and Motor Octane Number scales and further shows why some fuels test differently in these two methods. The knock length is also used to investigate unusual behavior observed in Methane Number reference fuels data - behavior which traditional concepts such as ignition delay and flame speed are unable to explain on their own. Secondly, this work focuses on the application of fuels such as bio-derived alcohols (ethanol and butanol) and fatty acid methyl esters in traditional and advanced combustion applications. Reactivity differences between alcohol and petroleum fuels are described and explained. Lastly, a new metric, the HCCI Number, is developed which allows the prediction of combustion timing in HCCI engines, and is highly amenable toward the development of bench-top laboratory apparatuses to facilitate practical adoption by fuel manufactures. Data from 23 different fuel blends tested in Cooperative Fuel Research (CFR) engines, a Fuel Ignition Tester, and a HCCI engine provide the experimental support for the theory presented herein. Additionally, a new chemical-kinetic mechanism is developed and used to describe combustion of n-butanol/n-heptane fuel mixtures in both conventional and advanced combustion applications (HCCI). Computational modeling is also used to examine the experiments presented herein: single and multi-zone (CHEMKIN) as well as system-level (GT Power) and multi-dimensional (CONVERGE) modeling approaches are developed and discussed. For the HCCI experiments conducted herein, an engine test-bed that allows HCCI examination across a wide array of conditions was also designed and fabricated. In summary, it is hoped that with better understanding of how fuels react in current and future engines, researchers can achieve the control necessary to bring higher performance engines to market and help the world take one step closer to addressing some of the pressing environmental and humanitarian issues at hand.
Open Access
Comprehensive concept-phase system safety analysis for hybrid-electric vehicles utilizing automated driving functions
(Colorado State University. Libraries, 2019) Knopf, Matthew David, author; Bradley, Thomas, advisor; Olsen, Daniel, committee member; Pasricha, Sudeep, committee member
Automotive system safety (SS) analysis involving automated driving functions (ADFs) and advanced driver assistance systems (ADAS) is an active subject of research but highly proprietary. A comprehensive SS analysis and a risk informed safety case (RISC) is required for all complex hybrid-vehicle builds especially when utilizing ADFs and ADAS. Industry standard SS procedures have been developed and are accessible but contain few detailed instructions or references for the process of completing a thorough automotive SS analysis. In this work, a comprehensive SS analysis is performed on an SAE-Level 2 autonomous hybrid-vehicle architecture in the concept phase which utilizes lateral and longitudinal automated corrective control actions. This paper first outlines a proposed SS process including a cross-functional SS working group procedure, followed by the development of an item definition inclusive of the ADFs and ADAS and an examination of 5 hazard analysis and risk assessment (HARA) techniques common to the automotive industry that were applied to 11 vehicle systems, and finally elicits the safety goals and functional requirements necessary for safe vehicle operation. The results detail functional failures, causes, effects, prevention, and mitigation methods as well as the utility of, and instruction for completing the various HARA techniques. The conclusion shows the resulting critical safety concerns for an SAE Level-2 autonomous system can be reduced through the use of the developed list of 116 safety goals and 950 functional safety requirements.
Open Access
Design considerations for an engine-integrated reciprocating natural gas compressor
(Colorado State University. Libraries, 2014) Malakoutirad, Mohammad, author; Bradley, Thomas H., advisor; Young, Peter, committee member; Olsen, Daniel, committee member
This thesis presents the development of an engine retrofit concept to turn a ICE vehicle's engine into a compressor for convenient natural gas refueling, as opposed to building a smaller secondary standalone unit. More specifically, this project seeks to outfit an internal combustion engine (ICE) to serve the dual purposes of providing vehicle propulsion and compression for natural gas refueling with minimal hardware substitution. The principal objective of this thesis is to describe and analyze the dynamic and thermal design considerations for an automotive engine-integrated reciprocating natural gas (NG) compressor. The purpose of this compressor is to pressurize storage tanks in NG vehicles from a low-pressure NG source by using one of the cylinders in an engine as the compressor. The engine-integrated compressor is developed by making minor changes to a 5.9 liter displacement diesel-cycle automotive engine. In this design, a small tank and its requisite valving are added to the engine as an intermediate storage tank to enable a single compressor cylinder to perform two-stage compression. The resulting pressure in the compressor cylinder and storage tank is 25 MPa, equivalent to the storage and delivery pressure of conventional compressed NG delivery systems. The dynamic simulation results show that the high cylinder pressures required for the compression process create reaction torques on the crankshaft, but do not generate abnormal rotational speed oscillations. The thermal simulation results show that the temperature of the storage tank and engine increases over the safety temperature of the NG unless an active thermal management system is developed to cool the NG before it is admitted to the storage tanks. Results are then translated into vehicle-level operating costs and petroleum consumption for a dual-fuel NG-diesel vehicle.
Open Access
Design tradeoffs of a reciprocating auxiliary power unit
(Colorado State University. Libraries, 2013) Renquist, Jacob Vinod, author; Bradley, Thomas H., advisor; Olsen, Daniel, committee member; Young, Peter, committee member
This thesis presents a comparison of reciprocating auxiliary power units to conventional, gas turbine auxiliary power units. A metric of interest is created to represent the specific auxiliary power system weight including the prime mover, generator, gearbox, and fuel consumed. The metric of interest is used to compare the different auxiliary power unit technologies by incorporating detailed engine simulations, auxiliary power unit system weight modeling, and flight path-realized fuel consumption modeling. Results show that reciprocating auxiliary power units can be competitive with gas turbines in near-term, more-electric aircraft applications.
Open Access
Development of mobile open-path cavity ring-down spectrometer for measurement of trace atmospheric methane gas
(Colorado State University. Libraries, 2018) McHale, Laura, author; Yalin, Azer P., advisor; Marchese, Anthony, committee member; Olsen, Daniel, committee member; Pierce, Jeffrey, committee member
Use in recent decades of methane as a 'clean' alternative to coal and gasoline has seen a rapid increase in natural gas extraction in the United States. Although combustion of methane produces less CO2 than traditional fuels, it is a powerful greenhouse gas with a 20 year Global Warming Potential (GWP20) that is 84x that reported for CO2 in the latest IPCC report; therefore, the promise of natural gas as a clean fuel can only by realized if emissions of uncombusted gas are sufficiently low. To address this problem, there is a need for both regional (basin wide) measurements of methane emissions to determine global levels, as well as localized measurements to allow identification and reduction of emissions ("leaks") from specific equipment. The goal of this research is to develop a mobile open-path cavity ring-down spectroscopy (CRDS) sensor for localized measurements of atmospheric methane. While designed with the oil and gas industry in mind, the technology also has application to study emissions from agricultural operations and those from other sectors. This thesis presents development from proof-of-concept open-path sensor through two mobile iterations. CRDS can provide fast, non-intrusive, sensitive measurements; but in contrast to available instruments, the focus is on open-path operation (no flow-cell and pump) to provide opportunities for significant weight, size and power reductions to increase the mobility of the technique (<4 kg, <25 W). Challenges of open-path operation, such as fitting broadened spectral peaks, preserving mirror cleanliness and techniques for removing signal noise due to aerosol particles are addressed. The sensor is based on widely available and mature engineering near-infrared (NIR) opto-electronic components that have been developed for the telecom industry. Sensor validation with known methane concentrations show that the open-path sensor is capable of measuring atmospheric concentrations in the range of ~1.8-20+ ppmv at a rate of 1-3 Hz. Sensitivity studies using Allan variance techniques show sensitivity of < 20 ppbv in 1 – adequate for practical leak detection of small plumes <1 ppmv. Comparisons against a commercially available closed path sensor in mobile deployments are presented, along with mobile measurements from natural gas facilities in Platteville, CO and Washington County, PA. Finally, integration of the sensor onto a UAS platform for airborne measurements of methane and ammonia from agricultural applications is discussed.
Open Access
Enhancing hydraulic performance of a multi-stage anaerobic digester for high solids cattle manure
(Colorado State University. Libraries, 2019) Young, Kadin Catlin, author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Olsen, Daniel, committee member
Anaerobic digestion is an attractive technology for waste handling because it converts low value waste material into energy and other useful products while performing necessary treatment for proper waste disposal. Conventional anaerobic digestion technology, however, has been met with many economic challenges when being applied to high solids substrate such as dry-lot cattle manure. In Colorado and the rest of the arid west, feedlot practices and dry climate combine to form a waste product that is very high in total solids (TS) content, from 50% up to 90% TS. Since the most common conventional digestion practices typically can only treat wastes up to a maximum of 15% TS, other options must be considered to digest this abundant waste product and convert it to a valuable resource. Research at Colorado State University has led to the development of an innovative multi-stage anaerobic digester (MSAD) technology capable of digesting high solids content waste with very low water addition. The CSU MSAD has demonstrated the ability to successfully digest high solids content waste like that found at the many Colorado feedlots. This system differs from conventional technology in that hydrolysis takes place in one reactor and methane generation takes place in a separate high rate digester. The development of the MSAD for digestion of high solids cattle manure leads to the promising opportunity for valorization of a prevalent waste product in Colorado to create valuable products including methane biogas, compost, and fertilizers. The present research aims to advance the technology by assessing the performance of the MSAD running in a fully linked configuration including each of its individual components: the Upflow Solid-State Hydrolysis Reactor (USSHR), the Leachate Feed Tank (LFT), and the Fixed Film Reactor (FFR). A fully functional Central Leachate Processing System (CLPS) was constructed to demonstrate the technology, to facilitate column scale studies, and to link with the prototype USSHR (P-USSHR) to enable the evaluation of an improved liquid distribution system. The MSAD was constructed at column scale to evaluate the impact on organic leaching potential of varying hydraulic loading rate (HLR) through the USSHR using HLRs of 20, 41, and 75 cm/day for 16-day cycles. This experiment was the first successful demonstration of a fully linked MSAD system using cattle manure as feedstock. It was found that the higher HLR of 75 cm/day yields 25% more COD leached over the 16-day operating period than the two lower loading rates. Additionally, it was found that the P-USSHR achieved notable improvements over the previous operation in hydraulic distribution through the reactor and therefore improved digestion performance and volatile solids destruction, though areas for further improvement were noted.
Open Access
Investigating overturning high sided vehicles through modeling high Reynolds number incompressible flow around a rectangular cylinder near a plane wall boundary
(Colorado State University. Libraries, 2023) Sanchez, Daniel K., author; Venayagamoorthy, S. Karan, advisor; Chen, Suren, advisor; Olsen, Daniel, committee member
Safety on public roadways is of paramount importance to road users, road authorities, the local economy, and the general wellbeing of society. High sided vehicles (commonly known as semitrucks in the United States (US) or lorries in the European Union (EU)) are used throughout the world for transporting freight, but they are susceptible to roll-over accidents due to high crosswind. The overturning of high sided vehicles is of concern during extreme wind events. In Boulder, Colorado, it is estimated that eight high wind events (with gusts greater than 75 mph) occur every year. The research field of overturning high sided vehicles is young compared to other areas of knowledge since CJ Baker of the United Kingdom (UK) opened the research field in 1986. The traditional method applied for evaluating the likelihood of a high sided vehicle to overturn is to use the predetermined rolling moment coefficient (Crolling) and translate the wind speed into a rolling moment. The resulting rolling moment can be compared to the restoring moment to determine the force required to overturn the high sided vehicle. This methodology requires that Crolling be accurate with respect to the high sided vehicle being analyzed. A recent study conglomerated many papers that have investigated Crolling, showing wide variation in the expected Crolling for yaw angles between 45° and 90° (a direct crosswind). Through this thesis, it was discovered that some of the variation is due to the fact that Crolling is Reynolds number dependent. In this thesis a comprehensive verification analysis and validation of a computational fluid dynamics (CFD) model was completed. Verification and validation are key components to performing a quality CFD analysis. When referring to verification, this traditionally implies a grid independence study to ensure the CFD results are accurate with respect to the mesh sizing. However, this study explores why a comprehensive verification study is necessary to evaluate the influence of the flow domain size for high Reynolds number incompressible flow around a bluff body. Additionally, it was found for flow around a rectangular cylinder near a plane wall boundary with a gap ratio of 0.407, that the drag coefficient (Cdrag) is dependent on Reynolds number. This fundamental field was connected to the application of overturning high sided vehicles, with the assumption that a 2D rectangular cylinder could represent the trailer section of a high sided vehicle. It was found that traditional studies on overturning high sided vehicles assume the aerodynamic coefficients are Reynolds number independent, whereas the fundamental field shows that there is a Reynolds number dependence. It is apparent that additional work on determining Crolling is needed due to the Reynolds number dependency.
Open Access
Modeling and parametric study of end-gas autoignition to allow the realization of ultra-low emissions, high-efficiency heavy-duty spark-ignited natural gas engines
(Colorado State University. Libraries, 2022) Bestel, Diego Bernardi, author; Windom, Bret, advisor; Marchese, Anthony, committee member; Olsen, Daniel, committee member; Bangerth, Wolfgang, committee member
Engine knock and misfire are barriers to pathways leading to high-efficiency Spark-Ignited (SI) Natural Gas (NG) engines. The general tendency to knock is highly dependent on engine operating conditions and the fuel reactivity. The problem is further complicated by the low emission limits and the wide range of chemical reactivity in pipeline-quality natural gas. Depending on the region and the source of the natural gas, its reactivity, described by its Methane Number (MN), which is analogous to the Octane Number for liquid SI fuels, can span from 65 to 95. In order to realize diesel-like efficiencies, SI NG engines must be designed to operate at high Brake Mean Effective Pressures (BMEP), near or beyond knock limits, over a wide range of fuel reactivity. This requires a deep understanding of the combustion-engine interactions pertaining to flame propagation and End-Gas Autoignition (EGAI), i.e., the autoignition of the unburned gas (end gas) ahead of the flame front. However, EGAI, if controlled, provides an opportunity to increase SI NG engine efficiency by increasing the combustion rate and the total fraction of burned fuel, mitigating the effects of the slow flame speeds characteristic of natural gas fuels, which generally reduce BMEP and increase unburned hydrocarbon emissions. For this reason, to realize diesel-like efficiencies and ultra-low emissions on SI NG engines, this work proposes the study of the main parameters influencing the modeling and prediction of NG EGAI to allow for its control. In this work, a novel EGAI detection and onset determination method was developed to reliably quantify EGAI for data analysis and engine control. The new method allowed the prediction of EGAI on SI NG engines without the need to use engine- and operating-condition-dependent thresholds and reduced the error in quantifying the fraction of the total energy released by the EGAI event by up to 40%pts. One- and three-dimensional engine models were then developed to study the engine/fuel interactions that lead to NG EGAI and its performance benefits. These models, although having decent agreement with experimental data, showed the need to account for NOx chemistry when predicting NG EGAI due to a consistently later prediction of the EGAI onset (∼1.65 crank-angle degrees) and thus, a new reduced chemical mechanism for real NG fuels was developed containing NOx chemistry. The new reduced mechanism improved the EGAI onset prediction agreement to within ±0.5 crank-angle degrees and decreased simulation time during combustion by nearly 50% when using the further reduced AREIS50NOx chemical mechanism. These models were then used to study the role of NG composition on EGAI, evaluate the engine/fuel interactions leading to NG EGAI, and perform engine optimization while leveraging EGAI to increase thermal efficiency. Piston design optimization combined with a Controlled EGAI (C-EGAI) combustion mode allowed a Heavy-Duty (HD) SI NG engine to operate at diesel-like efficiencies, i.e., Brake Thermal Efficiency (BTE) ≥44%. Experimental and modeling data analysis revealed that earlier and faster heat release increases combustion efficiency by an average of 1% pts, increases work transferred to the piston resulting in a decrease in exhaust losses by 50% depending on the engine operating condition while slightly increasing heat losses. Finally, the simulation results revealed an opportunity to further enhance the BTE (up to 50%) by enabling C-EGAI combustion at leaner conditions, λ=1.4-1.6.
Open Access
Renewable energy in community: economic impacts of the grid
(Colorado State University. Libraries, 2022) Saarloos, Benjamin Alexander, author; Quinn, Jason, advisor; Bradley, Thomas, committee member; Burkhardt, Jesse, committee member; Olsen, Daniel, committee member
The U.S. energy grid is a complex system that supports everyday lives. Grid energy has traditionally flowed in one direction from large, centralized power plants through transmission and distribution networks to corporate and residential consumers. However, with a growth in renewable energy systems (RES), energy flow has begun to take on a more bi-directional character with distributed generation, including excess energy generated by consumers being fed back to the energy grid. The breadth of individual energy use impacts and societal benefits attributed to growth in RES calls for analysis and development of RES on the community scale. Beyond the physical energy connection it provides, the grid can serve as an economic mechanism whereby RES can be sustainably developed through the grid, rather than an alternative to the grid. Measures have been developed to advance RES toward sustainability targets, recognizing that the grid plays an important enabling role. Net-zero energy is a classification system designed to reduce energy consumption in buildings and communities in support of climatic goals to reduce greenhouse emissions. A hierarchy of renewable energy supply options is established with a preference for on-site renewable energy over off-site supply options. Value of Solar (VOS) is an electric rate design mechanism intended to determine the true value of solar photovoltaic (PV) generated electricity. Beyond the obvious benefit of fossil fuel saved, VOS includes cost savings associated with avoided capacity, transmission & distribution cost deferral, and environmental benefits. Net-zero energy and VOS methodology are both identified as sustainability measures within a broader RES design process. Sustainable RES design recognizes that harmonizing economic, environmental, and social interests is a community effort. Case-studies present an opportunity to further develop a consistent set of design principles while simultaneously presenting unique and important results. In this work, a net-zero energy analysis is conducted for the National Wester Center in Denver, CO. A coupled energy and economic analysis demonstrates the critical role played by the grid in the economic feasibility of achieving net-zero energy, as well as the mutual benefit of on-site energy storage. A VOS case study is performed for Sioux Center Municipal Utilities in northwest Iowa leveraging five years of municipal power consumption coupled with real PV electricity generation data. A dual optimization approach develops an electric rate structure that best aligns with and incentivizes development toward optimal VOS design. Together, these studies affirm that while local technical solutions and optimal designs may differ, the principles of sustainable design can be applied and followed consistently such that RES can grow and flourish in communities across the globe.
Open Access
State-based engine models for transient applications with a scalable approach to turbocharging
(Colorado State University. Libraries, 2015) Bell, Clay S., author; Bradley, Thomas, advisor; Zimmerle, Daniel, committee member; Olsen, Daniel, committee member; Young, Peter, committee member
Microgrids have the potential to improve energy surety, increase the penetration of renewable energy, and provide electrical power in remote areas; however, reduced system inertia contributes to challenges in maintaining power quality during operation. In this dissertation a state-based mean-value turbocharged diesel engine model is developed for applications in microgrid. The model is validated against transient data collected during step load testing at Colorado State University’s Engines and Energy Conversion Laboratory. A controller with an air-fuel ratio based smoke limit and load based gain schedule is implemented to improve agreement with experimental data when compared to a simplified model frequently used in microgrid control studies. The state-based model is capable of variable speed operation, extending the utility to transient applications beyond micro-grid. Due to the uncertainty around transient performance, lean burn gas engines typically are employed in steady load applications such as distributed generation or industrial systems such as natural gas compression in order to take advantage of the low cost of the fuel, improved efficiency, and reduced emissions. There is significant interest in natural gas engines for microgrids due to the low fuel cost and indications that natural gas supplies would be secure during an interruption of the national electric grid. In addition, replacing diesel engines with gas engines has been identified as a method to reduce cost and emissions associated with drilling and well stimulation. However; both of these applications involve transients which may exceed the capabilities of lean-burn natural gas engines. In this dissertation a state based mean-value turbocharged lean-burn natural gas model is developed to study transient control strategies. Transient data was unavailable; however the model exhibits the expected characteristics during transient loading, namely limited load acceptance capability due to turbocharger lag and narrow air-fuel ratio limits. Collecting and processing turbocharger performance data to a form appropriate for simulation is one of the more difficult and effort intensive steps when implementing state based engine models. A method is developed to implement non-dimensional performance maps thereby allowing a range of turbochargers to be modeled from the same performance data, reducing the effort required to implement models of different sizes. The non-dimensional maps seek to model the performance of compressor and turbine families in which the geometry of the rotor and housing are similar, and allow the turbocharger to be scaled for simulation in much the same way used to design customized sizes of turbochargers. A method to match the non-dimensional compressor map to engine performance targets by selecting the compressor diameter is presented, as well as a method to match the turbine to the compressor.
Open Access
Techno-economic analysis and decision making for PHEV benefits to society, consumers, policymakers and automakers
(Colorado State University. Libraries, 2012) Al-Alawi, Baha Mohammed, author; Bradley, Thomas, advisor; Duff, William, advisor; Olsen, Daniel, committee member; Zimmerle, Dan, committee member; Labadie, John, committee member
Plug-in hybrid electric vehicles (PHEVs) are an emerging automotive technology that has the capability to reduce transportation environmental impacts, but at an increased production cost. PHEVs can draw and store energy from an electric grid and consequently show reductions in petroleum consumption, air emissions, ownership costs, and regulation compliance costs, and various other externalities. Decision makers in the policy, consumer, and industry spheres would like to understand the impact of HEV and PHEV technologies on the U.S. vehicle fleets, but to date, only the disciplinary characteristics of PHEVs been considered. The multidisciplinary tradeoffs between vehicle energy sources, policy requirements, market conditions, consumer preferences and technology improvements are not well understood. For example, the results of recent studies have posited the importance of PHEVs to the future US vehicle fleet. No studies have considered the value of PHEVs to automakers and policy makers as a tool for achieving US corporate average fuel economy (CAFE) standards which are planned to double by 2030. Previous studies have demonstrated the cost and benefit of PHEVs but there is no study that comprehensively accounts for the cost and benefits of PHEV to consumers. The diffusion rate of hybrid electric vehicle (HEV) and PHEV technology into the marketplace has been estimated by existing studies using various tools and scenarios, but results show wide variations between studies. There is no comprehensive modeling study that combines policy, consumers, society and automakers in the U.S. new vehicle sales cost and benefits analysis. The aim of this research is to build a potential framework that can simulate and optimize the benefits of PHEVs for a multiplicity of stakeholders. This dissertation describes the results of modeling that integrates the effects of PHEV market penetration on policy, consumer and economic spheres. A model of fleet fuel economy and CAFE compliance for a large US automaker will be developed. A comprehensive total cost of ownership model will be constructed to calculate and compare the cost and benefits of PHEVs, conventional vehicles (CVs) and HEVs. Then a comprehensive literature review of PHEVs penetration rate studies will be developed to review and analyze the primary purposes, methods, and results of studies of PHEV market penetration. Finally a multi-criteria modeling system will incorporate results of the support model results. In this project, the models, analysis and results will provide a broader understanding of the benefits and costs of PHEV technology and the parties to whom those benefits accrue. The findings will provide important information for consumers, automakers and policy makers to understand and define HEVs and PHEVs costs, benefits, expected penetration rate and the preferred vehicle design and technology scenario to meet the requirements of policy, society, industry and consumers.
Open Access
The effect of altitude on turbocharger performance parameters for heavy duty diesel engines: experiments and GT-Power modeling
(Colorado State University. Libraries, 2014) Thompson, Andrew T., author; Marchese, Anthony J., advisor; Olsen, Daniel, committee member; De Miranda, Micahel A., committee member
Operation at high altitude increases the risk of high cycle fatigue (HCF) failure on turbine blades in internal combustion engine turbochargers. Because engine manufacturers rarely acquire performance data at the high altitude limits of their engines, it is imperative that manufacturers rely on computer simulation to visualize, quantify and understand turbocharger performance when experimental tests are not practical. Typically, CFD and FEA models are used to predict HCF damage for turbine wheels. However, the boundary conditions and other input data required for such simulations are often unknown at high altitudes. The main objective of this thesis was to develop these critical boundary conditions and input data for a Cummins QSK19 CI engine and a Cummins QSK50 CI engine. This objective was accomplished by installing and testing both of these engines at 5000ft elevation and calibrating GT-Power computer simulation models against the experimental data at 5000ft elevation. After the models were calibrated against experimental data, the models were extrapolated to the altitude capability of these engines and the critical boundary conditions were recorded. In addition to the diesel engine experiments and modeling, a single cylinder HCCI computer simulation model was developed to evaluate the performance of Woschni and Hohenberg heat transfer correlations by comparing GT-Power model predictions with measured in-cylinder pressure data. Analysis was performed by generating a single zone GT-Power model of a modified John Deere DI 2.4L four-cylinder engine, which was previously converted at CSU to operate in HCCI port injection mode. The HCCI engine was operated at an equivalence ratio of 0.33 and a fuel mixture of 40% iso-octane and 60% n-heptane by volume. The combustion chemistry was modeled using a reduced Primary Reference Fuel (PRF) mechanism from Ra and Reitz with 41 species and 130 reactions. The Cummins modeling results indicate that GT-Power can predict turbocharger performance within 7.59% variation from measured data at 5000ft. When the model was extrapolated to 8000ft, GT-Power predicted an average expansion ratio increase of 1.81% and an average turbine inlet temperature decrease of 2% for the QSK19 CI engine. The Cummins QSK50 GT-Power model predicted an average expansion ratio increase of 2.73% and an average turbine inlet temperature decrease of 9.12% from 5000ft to 8000ft. The HCCI simulation results showed that GT-Power can accurately predict the start of combustion. In addition, the simulation results showed that the pressure rise rate has a low sensitivity to the in-cylinder heat transfer rate.
Open Access
The effect of fuel reactivity and exhaust gas recirculation on knock propensity of natural gas
(Colorado State University. Libraries, 2020) Mohr, Jeffrey, author; Marchese, Anthony, advisor; Olsen, Daniel, committee member; Reardon, Kenneth, committee member
The development of high efficiency, spark ignited natural gas engines is currently limited by engine knock at high compression ratio/elevated boost pressures and misfire at lean conditions/high exhaust gas recirculation (EGR) levels. The knock and misfire limits are further confounded by the wide variety in fuel reactivity observed in "pipeline quality" natural gas. In this study, a rapid compression machine was used to characterize the effects of EGR and variation in natural gas fuel reactivity on the homogeneous ignition delay, flame propagation rate, and end-gas autoignition propensity for stoichiometric natural gas/oxidizer/EGR blends. A reduced chemical kinetic mechanism was also developed to accurately model the homogeneous ignition delays measured in the Colorado State University rapid compression machine (CSU RCM). Pipeline quality natural gas with a range of chemical reactivity (68 < Methane Number < 95) was simulated using mixtures of CH4, C2H6, and C3H8. Exhaust gas recirculation gases were simulated with mixtures of Ar, CO2, CO, and NO at substitution rates of 0 to 30 mass percent. Ignition delay period under homogeneous autoignition conditions was measured at compressed pressures of 30.2 to 34.0 bar and compressed temperatures of 667 to 980 K. End-gas autoignition fraction and flame propagation rate were measured by initiating a laser spark in the center of the combustion chamber, after compression, at pressures of 30.7 to 32.7 bar and temperatures of 751 to 795 K. The results indicate that both fuel reactivity and the presence of reactive species (NO and CO) in the exhaust gas recirculation have a strong impact on end-gas autoignition fraction. A chemical kinetic mechanism was developed to predict homogeneous ignition delays for pipeline quality natural gas in a pressure and temperature range of 1-100 bar and 500-1000 K respectively. This mechanism accurately predicted measured homogeneous ignition delay in the RCM with a total average relative error of 11.0%.
Open Access
The role of physical and chemical properties of single and multicomponent liquid fuels on spray processes, flame stability, and emissions
(Colorado State University. Libraries, 2019) Alsulami, Radi Abdulmonem, author; Windom, Bret, advisor; Marchese, Anthony, committee member; Olsen, Daniel, committee member; Venayagamoorthy, Karan, committee member
Ensuring reliable and clean combustion performance of IC engines, such as liquid-fueled gas turbines, is associated to our understanding of the impact of fuel composition and properties, as well as the processes that the liquid fuel experiences, e.g., atomization, vaporization, turbulent mixing, and chemical kinetics, on the combustion efficiency, stability, and emissions. This understanding is a key prerequisite to the development of fuel surrogates and the deployment of alternative jet fuels. Most of the surrogate formulation activities, especially with regard to aviation fuels, have targeted only the gas-phase behavior of the real fuels, often neglecting properties responsible for atomization, vaporization, and fuel/air mixing (i.e., physical properties). In addition, much research has been done to understand the flame stability (e.g., lean blowout limit and flame liftoff height) of gaseous and pre-vaporized fuels. Thus, the optimization of the fuels and the liquid fueled combustion devices, e.g., gas turbines, requires the consideration of the two-phase process and the coupling between the complex physical and chemical processes. This will improve the understanding of the mechanisms that controls flame lean blowout limit and liftoff height of liquid fuels. Therefore, an appropriate surrogates will be formulated and a faster processes to certify the alternative fuels will be achieved. In this work, the flame stability in spray burner, quantified by flame lean blowout liftoff height, for different single, binary, alternative, and conventional fuels were experimentally measured. The flame behavior from the spray burner was compared to the results which was done using gaseous flame platform, e.g., counterflow flame burner, to clearly demonstrate the significant importance of two-phase spray processes (i.e., atomization, vaporization, and turbulent mixing) on flame stability. It was found that the atomization process, which can lead to the variation of the droplet size and distribution, has significant impact on flame stability. This is because any change in the droplet size can enhance/diminish the vaporization and mixing processes, and therefore influence the clean and efficient energy conversion process. In addition, the sensitivity of the fuels properties on flame stability was evaluated to provide an explanation for why certain fuel properties govern flame stability, such as lean blowout and liftoff height. Thus, flame stability mechanisms can be developed. A number of approaches were used in this work to address these issues, such as multiple linear regression analysis, and previously developed correlations. The results indicate the importance of the atomization process (i.e. droplet size) on the vaporization rate and suggest that the liquid fuel fraction entering the flame plays a dominant role in controlling lean blowout limits. Thus, the large droplet and less volatile fuel was the most resistance fuel to flame blowout. The differences in liftoff height was shown to be a result of two-phase flame speed, which accounts for both pre-vaporized fuel reactivity defined by laminar flame speed (SL) and time scales associated with droplet evaporation. The influence of the physical and chemical properties of different jet fuels on spray process and thus on emissions is also investigated. This is done by measuring soot formation using Laser-Induced Incandescence (LII). The trends in spray flame soot formation are compared to the gas-phase Yield Sooting Index (YSI). Results indicate differences in planar soot distributions amongst the fuels and suggest a significant influence of the atomization and the vaporization processes on mixing and the soot formation.