Browsing by Author "Olsen, Daniel B., committee member"
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Item Open Access A computational and experimental study on combustion processes in natural gas/diesel dual fuel engines(Colorado State University. Libraries, 2015) Hockett, Andrew, author; Marchese, Anthony J., advisor; Hampson, Greg, committee member; Olsen, Daniel B., committee member; Gao, Xinfeng, committee member; Young, Peter, committee memberNatural gas/diesel dual fuel engines offer a path towards meeting current and future emissions standards with lower fuel cost. However, numerous technical challenges remain that require a greater understanding of the in-cylinder combustion physics. For example, due to the high compression ratio of diesel engines, substitution of natural gas for diesel fuel at high load is often limited by engine knock and pre-ignition. Additionally, increasing the natural gas percentage in a dual fuel engine often results in decreasing maximum load. These problems limit the substitution percentage of natural gas in high compression ratio diesel engines and therefore reduce the fuel cost savings. Furthermore, when operating at part load dual fuel engines can suffer from excessive emissions of unburned natural gas. Computational fluid dynamics (CFD) is a multi-dimensional modeling tool that can provide new information about the in-cylinder combustion processes causing these issues. In this work a multi-dimensional CFD model has been developed for dual fuel natural gas/diesel combustion and validated across a wide range of engine loads, natural gas substitution percentages, and natural gas compositions. The model utilizes reduced chemical kinetics and a RANS based turbulence model. A new reduced chemical kinetic mechanism consisting of 141 species and 709 reactions was generated from multiple detailed mechanisms, and has been validated against ignition delay, laminar flame speed, diesel spray experiments, and dual fuel engine experiments using two different natural gas compositions. Engine experiments were conducted using a GM 1.9 liter turbocharged 4-cylinder common rail diesel engine, which was modified to accommodate port injection of natural gas and propane. A combination of experiments and simulations were used to explore the performance limitations of the light duty dual fuel engine including natural gas substitution percentage limits due to fast combustion or engine knock, pre-ignition, emissions, and maximum load. In particular, comparisons between detailed computations and experimental engine data resulted in an explanation of combustion phenomena leading to engine knock in dual fuel engines. In addition to conventional dual fuel operation, a low temperature combustion strategy known as reactivity controlled compression ignition (RCCI) was explored using experiments and computations. RCCI uses early diesel injection to create a reactivity gradient leading to staged auto-ignition from the highest reactivity region to the lowest. Natural gas/diesel RCCI has proven to yield high efficiency and low emissions at moderate load, but has not been realized at the high loads possible in conventional diesel engines. Previous attempts to model natural gas/diesel RCCI using a RANS based turbulence model and a single component diesel fuel surrogate have shown much larger combustion rates than seen in experimental heat release rate profiles, because the reactivity gradient of real diesel fuel is not well captured. To obtain better agreement with experiments, a reduced dual fuel mechanism was constructed using a two component diesel surrogate. A sensitivity study was then performed on various model parameters resulting in improved agreement with experimental pressure and heat release rate.Item Open Access A computational study of auto ignition, spark ignition and dual fuel droplet ignition in a rapid compression machine(Colorado State University. Libraries, 2017) Bhoite, Siddhesh, author; Marchese, Anthony J., advisor; Olsen, Daniel B., committee member; Mahmoud, Hussam N., committee memberA series of computational modeling studies were performed using the CONVERGETM computational fluid dynamics (CFD) platform to gain in-depth understanding of the chemically reacting flow field, ignition and combustion phenomena in a various rapid compression machine (RCM) experiments conducted at CSU including homogeneous autoignition, laser ignition and droplet ignition experiments. A three-dimensional, transient computational modeling study was initially performed to examine premixed, homogeneous autoignition of isooctane/air and methane/air mixtures. A reduced chemical kinetic mechanism for isooctane comprising of 159 species and 805 reactions was developed using direct relation graph error propagation and sensitivity analysis (DRGEPSA) method. Computational results showed good agreement with experimental results capturing the negative temperature coefficient (NTC) behavior of isooctane. The premixed computations also revealed the importance of the piston crevice design for maintaining a homogenous flow field inside a RCM. The result showed that, as the volume of the piston crevices is increased, the roll up vortices are eliminated, which reduces the mixing of the lower temperature boundary layer gases with the higher temperature core gases, thereby maintaining the homogeneity of the flow field. Next, three-dimensional computational modeling laser-ignited premixed fuel/air mixtures at elevated temperatures and pressures in the RCM was performed with detailed chemical kinetics (86 species, 393 reactions). For methane/air mixtures, the computational results were compared against previously reported RCM experiments. Computations were also performed on laser-ignited n-heptane/isooctane/air mixtures under similar simulated conditions in the RCM. In the computations, a simulated spark modeled as a localized hotspot was introduced in the center of the combustion chamber resulting in an outwardly propagating flame, which, depending on the fuel reactivity, produced ignition in the end gas upstream of the flame. Methane/air computations were performed at equivalence ratio of 0.4 ≤ Ф ≤ 1.0 for direct comparisons with experimental measurements of instantaneous pressure, flame propagation rate, and lean limit. For compressed temperature of 782 K, a methane/air lean limit of Ф = 0.38 was predicted computationally (combustion efficiency, χ = 0.8), which was in good agreement with the experimental measurement of Ф = 0.43. For n-heptane/isooctane/air computations, auto-ignition of the end gas was predicted depending on the compressed temperature and Octane Number, which suggests the use of the laser ignition/RCM system as a means to quantify fuel reactivity for spark ignited engines. Lastly, RCM experiments in which single n-heptane droplets are suspended and ignited via compression-ignition in a quiescent, high-pressure, high-temperature, lean methane/air environments were simulated using the 86-species dual-fuel chemical kinetic mechanism developed previously. The simulations capture the ignition event in the vicinity of a spherical n-heptane droplet, which bifurcates into a propagating, premixed methane/air flame and stationary n-heptane/air diffusion flame. Comparisons against experimental measurements of droplet gasification rate, premixed flame propagation speed, and non-premixed flame position will be used to develop revised dual-fuel chemical kinetic mechanisms.Item Open Access A reduced chemical kinetic mechanism for computational fluid dynamics simulations of high brake mean effective pressure, lean-burn natural gas engines(Colorado State University. Libraries, 2012) Martinez Morett, David, author; Marchese, Anthony J., advisor; Olsen, Daniel B., committee member; Dandy, David S., committee memberRecent developments in numerical techniques and computational processing power now permit time-dependent, multi-dimensional computational fluid dynamics (CFD) calculations with detailed chemical kinetic mechanisms using commercially available software. Such computations have the potential to be highly effective tools for designing lean-burn, high brake mean effective pressure (BMEP) natural gas engines that achieve high fuel efficiency and low emissions. Specifically, these CFD simulations can provide the analytical tools required to design highly optimized natural gas engine components such as pistons, intake ports, pre-combustion chambers, fuel systems and ignition systems. To accurately model the transient, multi-dimensional chemically reacting flows present in these systems, detailed chemical kinetic mechanisms are needed that accurately reproduce measured combustion data at high pressures and lean conditions, but are of reduced size to enable reasonable computational times. Prior to the present study, these CFD models could not be used as accurate design tools for application in high BMEP lean-burn gas engines because existing reduced chemical kinetic mechanisms failed to accurately reproduce experimental flame speed and ignition delay data for natural gas at high pressure (40 atm and higher) and lean (0.6 equivalence ratio and lower) conditions. Existing methane oxidation mechanisms had typically been validated with experimental conditions at atmospheric and intermediate pressures (1 to 20 atm) and relatively rich stoichiometry. Accordingly, these kinetic mechanisms were not adequate for CFD simulation of natural gas combustion for which elevated pressures and very lean conditions are typical. This thesis describes an analysis, based on experimental data, of the laminar flame speed computed from numerous, detailed chemical kinetic mechanisms for methane combustion at pressures and equivalence ratios necessary for accurate high BMEP, lean-burn natural gas engine modeling. A reduced mechanism that was shown previously to best match data at moderately lean and high pressure conditions was updated for the conditions of interest by performing sensitivity analysis using CHEMKIN. The reaction rate constants from the most sensitive reactions were appropriately adjusted to obtain better agreement at high pressure lean conditions. An evaluation of two new reduced chemical kinetic mechanisms for methane combustion was performed using Converge CFD software. The results were compared to engine data and a significant improvement on combustion performance prediction was obtained with the new mechanisms.Item Open Access An analysis of the costs and performance of vehicles fueled by alternative energy carriers(Colorado State University. Libraries, 2024) Lynch, Alexander, author; Bradley, Thomas, advisor; Coburn, Tim, committee member; Olsen, Daniel B., committee memberThe transportation sector stands at the crossroads of new challenges and opportunities, driven by the pressing need to mitigate environmental impacts, enhance energy efficiency, and ensure sustainable mobility solutions. This transition will occur across diverse transportation modes, each with distinct characteristics and challenges. From light duty vehicles embracing electrification to maritime transport adopting alternative fuel engines, the push for low-carbon technology is reshaping the landscape of transportation. In this context, it is necessary to conduct a review and assessment of technologies, environmental benefits, and costs of alternative fuels and powertrains across a broad set of applications in the transportation sector. This study seeks to perform this assessment by combining bottom-up cost analysis, environmental assessments, and reviews of the literature to examine the techno-economic aspects of various fuel and powertrain options in the transportation sector. This approach involves detailed evaluations of individual components and systems to model the cost structures and efficiency profiles of vehicles. The results illustrated in this thesis will be embedded into adoption models to enable governments, utilities, private fleets, and other shareholders to make informed transportation planning decisions.Item Open Access An integrated approach to local based biofuel development(Colorado State University. Libraries, 2011) Enjalbert, Jean-Nicolas, author; Johnson, Jerry J., advisor; Peterson, Gary, 1940-, committee member; Olsen, Daniel B., committee member; McKay, John K., committee member; Byrne, Patrick F., 1948-, committee memberOilseed crops have potential to replace a portion of the on-farm energy demand currently satisfied by fossil fuel. This dissertation allies mechanical engineering, field testing, and molecular breeding research into an integrated approach to solve problems associated with straight vegetable oil (SVO) production and use on Colorado farms. Four related topics of investigation and activity are reported. To identify an adapted, short-season oilseed crop that could fit into the current High Plains dryland cropping system, a genetic diversity study was conducted on three potential oilseed species: Brassica juncea, Brassica carinata, and Camelina sativa. To illuminate the genetic basis of camelina response to drought stress, a two-year study of quantitative trait loci (QTLs) was implemented under dry and irrigated conditions using 181 recombinant inbred lines (RILS) developed from European cultivars. To understand and eventually manage camelina production, a multi-environmental regional trial of camelina seed yield, oil content, and oil quality was conducted with eight American and European varieties. Extension activities introduced SVO information and technology to farmers in Colorado. Camelina sativa showed better adaptation to semi-arid environments than B. juncea and B. carinata, outyielding them due to camelina's shorter stature, higher harvest index, and greater resistance to flea beetle. Camelina yield, oil content, and linolenic fatty acid (FA) content were higher in cool, wet environments than in warm, dry environments. Linolenic FA content and seed size were negatively correlated (p<0.05) with early flowering time. Earlier flowering was associated with increased seed yield (p<0.01) under dry and hot environments, but with decreased seed yield under irrigation. Environment was a larger source of variation than genotype for all the traits measured in this study. Twenty-nine QTLs were found in camelina for seed yield, oil quality, and drought-tolerance-related traits such as leaf water content and leaf nitrogen content, which could lead to breeding for improvement of camelina performance in semi-arid environments. Some QTLs were shared by multiple traits, suggesting either pleiotropic effects or proximity of genes. The cumulative effect of stable, favorable alleles for seed yield was a 16% increase in yield. Trait responses to moisture varied widely, both in the multi-environmental regional trial using cultivars and in the single-location trial using RILs. The range of trait response reflects variation in plasticity in camelina germplasm. Two analysis methods, namely, additive main effects and multiplicative interaction (AMMI) and the moisture difference value method, were used to detect false positive QTLs and to predict QTL effect in specific environments. AMMI was used successfully to delineate mega-environments within the study region and to identify the best-adapted varieties for these mega-environments. With the QTL data developed in this study, marker-assisted selection could be used to identify camelina varieties adapted to specific environments or to a broad range of environments. Five lines possessing three favorable yield QTLs expressed under drought conditions are undergoing seed increase and additional multi-locational testing for potential release. Oilseed-for-biofuel workshops, crusher demonstrations, and oilseed field days were conducted to demonstrate the feasibility of potential advantages of SVO for farmers wanting an alternative energy source to reduce their use of fossil fuel. A limited number of early adopters are beginning to integrate camelina into their crop rotation. Three small oilseed crushing and processing facilities have been established from collaboration with farmers and other agencies, and another is in the design stage. Two extension fact sheets will be published on camelina production and on biofuel production at a farm scale.Item Open Access Characterization of gaseous and particulate emissions from combustion of algae based methyl ester biodiesel(Colorado State University. Libraries, 2009) Fisher, Bethany, author; Marchese, Anthony John, 1967-, advisor; Olsen, Daniel B., committee member; Volckens, John, committee memberThe advantages to using biodiesel in place of petroleum diesel are also accompanied by disadvantages. Biodiesel is usually made from crops that are also used to produce food. The land and water use impacts would be profound if current biodiesel feedstocks were used to displace a significant portion of current global petroleum diesel consumption. Oil-producing algae is a favorable alternative to the more common biodiesel feedstocks (soy, canola, etc.) because it does not compete with food sources, does not require arable land to grow and has the potential to produce significantly more oil per area per year than any other oil crops. However, the fatty acid composition of the oil produced by algal species currently under consideration for fuel production differs from that of the more common vegetable oils in that it often includes high quantities of long chain and highly unsaturated fatty acids. When transesterified into fatty acid methyl esters (FAME) biodiesel, the unique fatty acid composition could have a substantial impact on emissions such as Nitrogen Oxides (NOx) and particulate matter (PM). Accordingly, the goal of this study was to examine the effect of the chemical structure of algal methyl esters on pollutant emissions from a diesel engine operating on algae-based FAME biodiesel. Tests were performed on a 2.4 L, 39 kW John Deere 4024T, off-road diesel engine meeting USEPA Tier 2 emissions regulations. The engine was fitted with a unique, low-volume fuel system that enabled emissions tests to be conducted with small specialty fuel samples. Tests were performed on 9 different fuel blends at 2 different engine loading conditions. Exhaust gas measurements were made using a 5-gas emissions analysis system that includes chemiluminescence measurement of NOx, flame ionization detection of total hydrocarbons, paramagnetic detection of oxygen and non-dispersive infrared detection of CO and CO2. Particulate matter was characterized using an Aerosol Mass Spectrometer (AMS), which is capable of direct measurement of particle composition. The PM size distributions (between 10 to 1000 nm) were measured using a Sequential Mobility Particle Sizer. Total PM mass emissions were measured using gravimetric analysis of Teflon filters and the ratio of elemental carbon to organic was measured using thermo-optical analysis of quartz filters. Experiments were performed with ultra-low sulfur diesel, soy biodiesel (both pure biodiesel, B100, and a blend of 20% biodiesel and 80% diesel, B20), canola biodiesel (B20 and B100), and two synthetic algal methyl ester formulations (B20 and B100 for each). Combustion of algal methyl esters resulted in decreased NOx relative to both canola and soy biodiesel and ULSD, in contrast to previous research that examined the effect of fatty acid saturation and chain length on NOx emissions. A correlation was found between NOx emissions and premixed burn fraction, which provides an explanation for these results. Emissions of formaldehyde and organic PM were found to be slightly elevated with the two algal fuels in comparison with the traditional feedstocks. Particle size distribution, total PM mass, total hydrocarbons, CO and acetaldehyde emissions were similar between the different types of biodiesel.Item Open Access Development of detailed prime mover models and distributed generation for an on-board naval power system trainer(Colorado State University. Libraries, 2012) Boley, Matthew J., author; Hagen, Christopher L., advisor; Olsen, Daniel B., committee member; Young, Peter M., committee memberA power management platform (PMP) has been developed for an electric generation plant on-board a U.S. naval ship. The control hardware and software interface with a Human Machine Interface (HMI) where the sailor can monitor and control the electric plant state. With the implementation of the PMP, there becomes a need to train the sailors how to effectively use the HMI to manage the power plant. A power system trainer was developed with all the physical parts of the power system modeled in software that communicate to the control software, HMI software, and training software. Previous simulation models of the prime movers created in MATLAB® Simulink® (developed at Woodward, Inc. for control code testing purposes) were inadequate to simulate all the signals the control software receives. Therefore, the goal of this research was to increase the accuracy and detail of the existing prime mover models and add detail to the current electrical grid model for use in a power system trainer while maintaining real-time simulation. This thesis provides an overview encompassing techniques used to model various prime movers, auxiliary systems, and electrical power system grids collected through literary research as well as creative adaptation. For the prime movers, a mean value model (MVM) was developed for the diesel engine as well as a thermodynamic based steam turbine model. A heat transfer model was constructed for an AC synchronous electrical generator with a Totally Enclosed Air to Water Cooled (TEWAC) cooling arrangement. A modular heat exchanger model was implemented and the electrical grid model was expanded to cover all of the electrical elements. Models now dynamically simulate all the hardware signals in software and the training simulation executes in real-time.Item Open Access Generalized pressure drop and heat transfer correlations for jet impingement cooling with jet adjacent fluid extraction(Colorado State University. Libraries, 2022) Hobby, David Ryan, author; Bandhauer, Todd M., advisor; Olsen, Daniel B., committee member; Prawel, David, committee member; Venayagamoorthy, Karan, committee memberJet impingement technologies offer a promising solution to thermal management challenges across multiple fields and applications. Single jets and conventional impinging arrays have been studied extensively and are broadly recognized for achieving extraordinary local heat transfer coefficients. This, in combination with the versatility of impinging arrays, has facilitated a steady incline in the popularity of jet impingement investigations. However, it is well documented that interactions between adjacent jets in an impinging array have a debilitating effect on thermal performance. Recently, in an attempt to mitigate the jet interference problem, a number of researchers have created innovative jet impingement solutions which eliminate crossflow effects by introducing fluid extraction ports interspersed throughout the impinging array. This novel adaptation on classical impinging arrays has been shown to produce dramatically improved thermal performance and offers an excellent opportunity for future high-performing thermal management devices. The advent of jet-adjacent fluid extraction in impinging arrays presents a promising improvement to impingement cooling technologies. However, there have been very few investigations to quantify these effects. Notably, the current archive of literature is severely lacking in useful, predictive correlations for heat transfer and pressure drop which can reliably describe the performance of such impinging arrays. Steady-state heat transfer and adiabatic pressure drop experiments were conducted using nine unique geometric configurations of a novel jet impingement device developed in this work. This investigation proposes novel empirical correlations for Darcy friction factor and Nusselt number in an impingement array with interspersed fluid extraction ports. The correlations cover a broad range of geometric parameters, including non-dimensional jet array spacing (S/Dj) ranging from 2.7 to 9.1, and non-dimensional jet heights (H/Dj) ranging from 0.31 to 4.4. Experiments included jet Reynolds numbers ranging from 70 to 24,000, incorporating laminar and turbulent flow regimes. Multiple fluids were tested with Prandtl numbers ranging from 0.7 to 21. The correlations presented in this work are the most comprehensive to date for impinging jet arrays with interspersed fluid extraction. Nusselt number was found to be correlated to impinging jet Reynolds number to the power of 0.57. The resulting correlation was able to predict 93% of experimental data within ±25%. During adiabatic pressure drop experiments, multiple laminar-turbulent flow transition regions were identified at various stages in the complex jet impingement flow path. The proposed Darcy friction factor correlation was separated into laminar, turbulent, and transition regions and predicted experimental data with a mean absolute deviation of 20%. The heat transfer and pressure drop correlations proposed in this investigation were used in a follow-on optimization study which targeted an exemplary impingement cooling application. The optimization study applied core experimental findings to a microchip cooling case study and evaluated the effects of geometry, flow, and heat load parameters on cooling efficiency and effectiveness. It was discovered that reducing non-dimensional jet height results in all-around improved cooling performance. Conversely, low non-dimensional jet spacing results in highly efficient but less effective solutions while high non-dimensional jet spacing results in effective but less efficient cooling.Item Open Access Ignition and combustion of liquid hydrocarbon droplets in premixed fuel/air mixtures at elevated pressures and temperatures(Colorado State University. Libraries, 2022) Bhoite, Siddhesh Bharat, author; Windom, Bret, advisor; Marchese, Anthony J., advisor; Olsen, Daniel B., committee member; Venayagamoorthy, Karan, committee memberThe combustion of two fuels with disparate reactivity such as natural gas and diesel in internal combustion engines has the potential to increase fuel efficiency, reduce fuel costs and reduce pollutant formation in comparison to traditional diesel or spark-ignited engines. However, dual-fuel engines are presently constrained by uncontrolled fast combustion (i.e., engine knock) as well as incomplete combustion and a better understanding of dual-fuel combustion processes is necessary to overcome these challenges. In addition to dual-fuel engines, this work is also motivated by abnormal combustion phenomenon that has been observed in highly boosted, spark ignited, natural gas engines, which is caused by engine lubricant oil droplets entering the cylinder and serving as unwanted ignition sources for the natural gas/air mixture. To study the fundamental combustion processes of ignition and flame propagation in dual-fuel engines and abnormal combustion triggered by lubricant oil droplets, single isolated liquid hydrocarbon droplets were injected into premixed CH4/O2/Inert mixtures at elevated temperatures and pressures. In this research, a rapid compression machine (RCM) was used in combination with a newly developed piezoelectric droplet injection system that is capable of injecting single liquid hydrocarbon droplets of 40 to 500 μm along the stagnation plane of the RCM combustion chamber. A high-speed Schlieren optical setup was used for imaging the combustion events in the chamber. Experiments were conducted for diesel fuel and lubricant oil droplets at various initial diameters (50 μm < do < 500 μm), various CH4/O2/Inert equivalence ratios (0 < ϕ < 1.2) and various compressed temperatures (740 K < Tc < 1000 K). Dual fuel experiments revealed multiple modes of droplet ignition, droplet combustion, and premixed flame propagation, which depend on the initial droplet temperature, droplet diameter, droplet velocity, and stoichiometry of the CH4/O2/N2/Ar mixture. In the case of small droplets, spherical ignition events were observed that transition into spherical non-premixed flames that envelope the droplet, producing an outwardly propagating spherical premixed flame. For larger droplet diameters moving at moderate velocity, the ignition event occurs near the droplet surface on the leeward side of the droplet and subsequently creates a non-premixed flame that envelopes the droplet and a non-spherical premixed flame. For droplets moving with high velocities, the ignition event occurs in the wake of the droplet, multiple diameters from the droplet surface, and creates a flame that propagates toward the droplet. Spherical, outwardly propagating premixed flames were observed for diesel droplet ignition in stoichiometric CH4/O2/N2/Ar mixtures, whereas elongated premixed flames were observed in lean CH4/O2/N2/Ar mixtures. The experiments conducted to understand abnormal combustion caused by lubricant oil droplets provided a valuable dataset of ignition delay periods of various petroleum and ester-based lubricant oils at a wide range of thermodynamic and mixture conditions. In concert with the experiments, a combined analytical droplet evaporation model and computational combustion model were developed that simulate the evaporation, ignition, and combustion processes observed in the experiments. The ignition delay dataset was used to successfully develop and validate a surrogate chemical kinetic mechanism suitable for mimicking the ignition characteristics of different lubricant oils. The experiments also revealed the different thermodynamic and mixture conditions at which the lubricant oil droplets did not show ignition. At compressed pressure of 24 bar and varied compressed temperatures of 740 K < Tc < 900 K in CH4/O2/N2/Ar mixture of ϕ = 0.6, two ester-based oils (EBO3 and EBO4) showed no ignition. The experiments and modeling indicate the minimum and maximum droplet sizes for which ignition will occur, the location and mode of ignition in the vicinity of the liquid droplet and the conditions under which the ignition event will transition into a propagating premixed flame. These experimental observations further enhance our understanding of lubricant oil combustion and provide qualitative information of engine operating conditions which can lower the abnormal combustion occurrence in natural gas engines. The results of this study advance the fundamental understanding of dual fuel combustion and provide the practical knowledge to inform which lubricant oil types and droplet sizes promote or inhibit abnormal combustion in natural gas engines.Item Open Access Investigation of a nonlinear controller that combines steady state predictions with integral action(Colorado State University. Libraries, 2010) Hodgson, David A., author; Duff, William S., advisor; Young, Peter M., advisor; Olsen, Daniel B., committee member; Anderson, Charles W., committee memberCross-flow water-to-air heat exchangers are a common element in heating ventilating and air conditioning (HVAC) systems. In a typical configuration the outlet air temperature is controlled by the flow rate of water through the coil. In this configuration the heat exchanger exhibits non-linear dynamics. In particular the system has variable gain. Variable gain presents a challenge for the linear controllers that are typically used to control the outlet air temperature. To ensure stability over the entire operating range controllers need to be tuned at the highest gain state. This leads to sluggish response in lower gain states. Previous research has shown the use of steady state predictions of the flow rate needed to produce zero steady state error has improved the transient response of a heat exchanger. In this project a nonlinear controller that provides smooth mixing between steady state predictions and integral control was introduced. Bounds for the steady state error introduced by the controller were theoretically derived and experimentally verified. The controller outperformed a properly tuned nominal PI controller for both input tracking and disturbance rejection.Item Open Access Measurement of ammonia emission from agricultural sites using open-path cavity ring-down spectroscopy and wavelength modulation spectroscopy based analyzers(Colorado State University. Libraries, 2018) Shadman, Soran, author; Yalin, Azer P., advisor; Marchese, Anthony J., committee member; Olsen, Daniel B., committee member; Ham, Jay, committee memberAgricultural activities and animal feedlot operations are the primary sources of emitted ammonia into the atmosphere. In the US, 4 Tg of ammonia is emitted every year into the atmosphere which ~%75 of that is due to these major sources. Ammonia is the third most abundant nitrogen containing species in the atmosphere and it has important impacts on atmospheric chemistry, health, and the environment. It is a precursor to the formation of aerosols and its deposition in pristine and aquatic systems leads to changes in ecosystem properties. Quantifying the dry deposition rate of ammonia in the first few kilometers of feedlots is crucial for better understanding the impacts of livestock and agricultural operations on environment. Therefore, fast, precise, and portable sensors are needed to quantify ammonia emission from its major sources. Absorption spectroscopy is a reliable technique by which compact and sensitive sensors can be developed for ammonia (and other gaseous species) detection. An open-path absorption spectroscopy based sensor allows ambient air to flow directly through its measurement region which leads to high-sensitivity and fast-response measurements. In this study, two open-path absorption based ammonia sensors using two techniques are developed: cavity ring-down spectroscopy (CRDS) and wavelength modulation spectroscopy (WMS). The CRDS and WMS based sensors show the sensitivity of ~1.5 ppb (at 1 second) and ~4 ppb (at 1 second), respectively. In both sensors, a quantum cascade laser (QCL) is utilized as the light source to cover the strongest absorption feature of ammonia in the mid-infrared (MIR) spectral region. It is the first demonstration of an open-path CRDS based sensor working in mid-infrared MIR, to our knowledge. The WMS based sensor developed in this study is low power (~25 W) and relatively lightweight (~4 kg). The low power consumption and compact size enables the sensor to be deployed on a commercialized unmanned aerial system (UAS) for aerial measurements. The combination of this sensor and another compact CRDS based methane sensor is used for simultaneous measurements of ammonia and methane (ground based and aerial). Methane is another important species emitted from the feedlots with a long lifetime (~10 years). It is nonreactive and thus not lost by dry deposition. Therefore, methane concentration is only influenced by dispersion while the ammonia concentration is affected by both deposition and dispersion. The dry deposition of ammonia nearby the concentrated animal feeding operations (CAFOs), as one of the major sources of ammonia, can be determined by measuring the decrease in the [NH3]/[CH4] ratio downwind.Item Open Access Methods for advancing automobile research with energy-use simulation(Colorado State University. Libraries, 2014) Geller, Benjamin M., author; Bradley, Thomas H., advisor; Marchese, Anthony J., committee member; Olsen, Daniel B., committee member; Young, Peter M., committee memberPersonal transportation has a large and increasing impact on people, society, and the environment globally. Computational energy-use simulation is becoming a key tool for automotive research and development in designing efficient, sustainable, and consumer acceptable personal transportation systems. Historically, research in personal transportation system design has not been held to the same standards as other scientific fields in that classical experimental design concepts have not been followed in practice. Instead, transportation researchers have built their analyses around available automotive simulation tools, but conventional automotive simulation tools are not well-equipped to answer system-level questions regarding transportation system design, environmental impacts, and policy analysis. The proposed work in this dissertation aims to provide a means for applying more relevant simulation and analysis tools to these system-level research questions. First, I describe the objectives and requirements of vehicle energy-use simulation and design research, and the tools that have been used to execute this research. Next this dissertation develops a toolset for constructing system-level design studies with structured investigations and defensible hypothesis testing. The roles of experimental design, optimization, concept of operations, decision support, and uncertainty are defined for the application of automotive energy simulation and system design studies. The results of this work are a suite of computational design and analysis tools that can serve to hold automotive research to the same standard as other scientific fields while providing the tools necessary to complete defensible and objective design studies.Item Open Access Modeling methane emissions from US natural gas operations: national gathering station emission factor development and facility/regional-scale top-down to bottom-up reconciliations(Colorado State University. Libraries, 2017) Vaughn, Timothy L., author; Marchese, Anthony J., advisor; Yalin, Azer P., advisor; Olsen, Daniel B., committee member; Opsomer, Jean D., committee memberUnited States natural gas dry production increased by 47% between 2005 and 2015 due to the widespread use of horizontal drilling and hydraulic fracturing to extract gas from shale and other tight formations. Natural gas production and consumption is projected to continue to increase for the foreseeable future. In 2016, the natural gas supply chain delivered 29% of the energy used in the U.S., and natural gas surpassed coal as the leading electricity generating source for the first time in U.S. history. When combusted, natural gas produces less CO2 per unit energy released compared to coal or petroleum. However, uncombusted methane (the primary component of natural gas) has a global warming potential 30 times higher than CO2 on a 100 year time horizon (including oxidation to CO2, but excluding climate-carbon feedbacks). Therefore, the net greenhouse gas impacts resulting from displacement of coal and petroleum by natural gas depend on the emission rate of uncombusted natural gas. Short term climate benefits resulting from coal substitution, for example, are lost if the net rate of methane (CH4) emission from the natural gas supply chain exceeds 3—4% . Three studies were conducted to quantify CH4 emissions from the natural gas industry. In particular, these studies focused on quantifying emissions from the gathering and processing sector and reconciling emissions estimates developed using top-down (tracer flux and aircraft) vs. bottom-up (on-site component-level) measurement approaches. In the first study, facility-level CH4 emissions measurements were made at 114 natural gas gathering facilities and 16 processing plants in 13 U.S. states during a 20-week field campaign conducted from October 2013 through April 2014. Measurement results were combined with facility counts obtained from state air permit databases and national inventories in a Monte Carlo simulation to estimate CH4 emissions from U.S. natural gas gathering and processing operations. Annual CH4 emissions from normal operations at gathering facilities totaled 1699 Gg (95% CI=1539—1863 Gg), while normal operations at processing plants totaled 505 Gg (95% CI=459—548 Gg). CH4 emissions from abnormal operations at gathering facilities were estimated in a separate Monte Carlo simulation based on field observations and a sub-set of field measurements. These emissions totaled 169 Gg (+426%/-96%). In the second study, coordinated dual-tracer, aircraft-based, and direct component-level measurements were made at midstream natural gas gathering and boosting stations in the Fayetteville shale in Arkansas, USA. On-site component-level measurements were combined with engineering estimates to generate comprehensive facility-level CH4 emission rate estimates ("study on-site estimates (SOE)") comparable to tracer and aircraft measurements. Concurrent measurements at 14 normally-operating facilities showed a strong correlation between tracer and SOE, but indicated that tracer measurements estimated lower emissions (regression of tracer to SOE=0.91 (95% CI=0.83—0.99, R2=0.89). Tracer and SOE 95% confidence intervals overlapped at 11/14 facilities. Contemporaneous measurements at six facilities suggested that aircraft measurements estimated higher emissions than SOE. Aircraft and study on-site estimate 95% confidence intervals overlapped at 3/6 facilities. In the third study, a detailed spatiotemporal inventory model was developed and used to reconcile top down and bottom-up CH4 emission estimates from natural gas infrastructure and other sources in the Fayetteville shale on two consecutive days. On Thursday October 1, 2015 13:00—15:00 CDT top-down aircraft mass balance flights estimated 28.7 (20.1—37.3 Mg/h 95% CI) from the study area, while the bottom-up ground level area estimate predicted 23.9 (20.9—27.3 Mg/h 95% CI). On Friday October 2, 2015 14:30—16:30 CDT top-down estimated 36.7 (21.3—52.1 Mg/h 95% CI), while bottom-up estimated 21.1 (18.4—24.2 Mg/h 95% CI). Production and gathering activities were the largest contributors to modeled CH4 emissions. In contrast to prior studies, comparisons on two consecutive days indicated overlapping confidence intervals between top-down aircraft estimates and bottom-up inventory-driven estimates. Operator participation and extensive activity data proved critical in understanding emissions as observed by aircraft. In particular, the agreement obtained was possible only because bottom-up models included the variability in production maintenance activities, which showed substantially higher emissions during daytime hours when aircraft-based measurements were performed. Results indicated that that poor activity estimates (counts and timing) for large episodic events likely drives divergence in CH4 emission estimates from production basins, and that even more precise activity data would be required to improve agreement between these two approaches.Item Open Access NOx formation in methyl ester, alcohol, and alkane droplet autoignition and combustion: PLIF measurements and detailed kinetic modeling(Colorado State University. Libraries, 2014) Grumstrup, Torben, author; Marchese, Anthony J., advisor; Yalin, Azer, advisor; Kreidenweis, Sonia, committee member; Olsen, Daniel B., committee memberNumerous studies have shown that diesel engines fueled by fatty-acid methyl ester biodiesel often exhibit slightly increased production of oxides of nitrogen (NOx) in comparison to petroleum diesel. A number of explanations for this increase have been proposed. One theory, which has been supported by optical engine test results, suggests that the presence of oxygen atoms in the methyl ester fuel molecule results in a leaner premixed autoignition zone, thereby increasing in-cylinder temperatures and promoting Zel'dovich NOx production. Other experiments have suggested that the unsaturated methyl esters in biodiesel cause an increase in CH radical production (and/or other potential precursors such as C2O) which in turn increases Fenimore NOx formation. In this work, these hypotheses are explored experimentally and computationally by considering autoignition and combustion of single, isolated methyl ester, alcohol and alkane droplets. Experiments were conducted in which the planar laser-induced fluorescence (PLIF) spectroscopy technique was applied to burning liquid fuel droplets in free-fall. A monodisperse stream of droplets was generated by a piezoelectric device and passed through a resistively heated ignition coil. A pulsed laser beam from a Nd:YAG-pumped dye laser (10 Hz, 10 ns width) was formed into a sheet and passed through the droplet flame. The dye laser was tuned to excite hydroxyl (OH) at 282.9 nm and nitric oxide (NO) at 226.0 nm. The resulting fluorescence was imaged by a Cooke Corporation DiCam Pro ICCD digital camera. Band pass filters were utilized to reject laser light scattering while admitting fluorescence wavelengths. Due to the small fluorescence signal, many fluorescence images were averaged together to create a useful average image; approximately 250 and 1000 images were averaged for OH and NO spectroscopy, respectively. Finally, pixel intensity of the averaged fluorescence image was integrated about the droplet center to create qualitative radial profiles of OH and NO concentration. Profiles were generated for a number of oxygenated fuels and one pure hydrocarbon: methanol, ethanol, 1-propanol, methyl butanoate, methyl decanoate, and n-heptane. To quantitatively interpret the contribution of Zel'dovich and Fenimore NOx mechanisms on NOx formation in the vicinity of igniting liquid droplets, detailed numerical droplet combustion simulations were conducted. The transient, spherically symmetric droplet combustion modeling featured detailed gas-phase kinetics, spectrally resolved radiant heat transfer, and multicomponent gas transport. New chemical kinetic mechanisms were created by appending NOx chemical kinetics to existing detailed methanol, methyl butanoate, and n-heptane mechanisms. In the computations, non-oxygenated (heptane) and oxygenated (methyl butanoate, methanol) fuel droplets are introduced into a hot (1150 K) air ambient whereupon the liquid vaporizes, thus producing a stratified fuel/air mixture that thermally autoignites after an ignition delay period. The computational results suggest that NOx formation in stratified fuel/air mixture in the vicinity of a cold liquid droplet is influenced greatly by the detailed full NOx chemistry (Fenimore, Zel'dovich and N2O) and cannot be fully explained by considering only the Zel'dovich NOx route. The computations also suggest, however, that the stoichiometry of the premixed autoignition zone in the laminar gas phase surrounding a spherical droplet differs from that observed in turbulent diesel spray ignition. In single droplets, irrespective of the fuel used, autoignition always initiates in the relatively hot lean region far from the droplet. In diesel sprays, depending on the thermodynamic conditions and fuel reactivity, ignition can occur in lean or rich regions by virtue of turbulent transport of heat and mass. In large molecular weight fuels like n-heptane or petroleum diesel fuel, this is often in mixtures which are quite rich (Φ ≈ 3). To underscore the difference between turbulent spray ignition and ignition of a single droplet, the most reactive mixture fraction and critical scalar dissipation rate were derived for the case of turbulent ignition The results show that for a turbulent non-premixed flame to ignite, two requirements must be met: (1) the fuel/air mixture fraction must be equal or similar to the most reactive mixture fraction, (2) the local scalar dissipation rate must be less than the critical scalar dissipation rate. Due to the effect of scalar dissipation rate on transport and mixing in turbulent, non-premixed flames, it is concluded that, at least as far as autoignition is concerned, autoignition of spherically-symmetric isolated fuel droplets has limitations as physical model for ignition of diesel sprays in compression ignition engines. However, the computations clearly show that transient NOx formation in presence of thermal and concentration gradients cannot be adequately described by the Zel'dovich NOx mechanism, which has consequences with regards to capability of computational engine simulations to accurately predict NOx formation.Item Open Access Optimizing water management in hydraulic fracturing(Colorado State University. Libraries, 2016) Esmaeilirad, Nasim, author; Carlson, Kenneth, advisor; Omur-Ozbek, Pinar, committee member; Catton, Kimberly, committee member; Olsen, Daniel B., committee memberTo view the abstract, please see the full text of the document.Item Open Access Physiochemical properties and evaporation dynamics of bioalcohol-gasoline blends(Colorado State University. Libraries, 2018) Abdollahipoor, Bahareh, author; Windom, Bret C., advisor; Reardon, Kenneth F., committee member; Olsen, Daniel B., committee memberAfter fermentation, the concentration of bioethanol is only 8-12 wt%. To produce anhydrous ethanol fuel, a significant amount of energy is required for separation and dehydration. Once the azeotrope composition is reached, distillation can no longer be exploited for purification and other expensive methods must be used. Replacing anhydrous ethanol fuel with hydrous ethanol (at the azeotrope composition) can result in significant energy and cost savings during production. Currently there is a lack of available thermophysical property data for hydrous ethanol gasoline fuel blends. This data is important to understand the effect of water on critical fuel properties and to evaluate the potential of using hydrous ethanol fuels in conventional and optimized spark ignition engines. In this study, the thermophysical properties, volatility behavior, evaporation dynamic, and mixing/sooting potential of various hydrous and anhydrous ethanol blends with gasoline were characterized. Results show that the properties of low and mid-level hydrous ethanol blends are not significantly different from those of anhydrous ethanol blends, suggesting that hydrous ethanol blends have the potential to be used in current internal combustion engines as a drop-in biofuel. Dual-alcohol approach, mixing lower and higher alcohols with gasoline to obtain a blend with a vapor pressure close to that of the base gasoline, is a potential way to circumvent issues with single alcohol blends. In second project, the azeotropic volatility behavior and mixing/sooting potential of dual-alcohol gasoline blends were studied by monitoring the distillation composition evolution and use of droplet evaporation model.Item Open Access Waste heat recovery from a high temperature diesel engine(Colorado State University. Libraries, 2017) Adler, Jonas E., author; Bandhauer, Todd M., advisor; Olsen, Daniel B., committee member; Sharvelle, Sybil E., committee memberGovernment-mandated improvements in fuel economy and emissions from internal combustion engines (ICEs) are driving innovation in engine efficiency. Though incremental efficiency gains have been achieved, most combustion engines are still only 30-40% efficient at best, with most of the remaining fuel energy being rejected to the environment as waste heat through engine coolant and exhaust gases. Attempts have been made to harness this waste heat and use it to drive a Rankine cycle and produce additional work to improve efficiency. Research on waste heat recovery (WHR) demonstrates that it is possible to improve overall efficiency by converting wasted heat into usable work, but relative gains in overall efficiency are typically minimal (~5-8%) and often do not justify the cost and space requirements of a WHR system. The primary limitation of the current state-of-the-art in WHR is the low temperature of the engine coolant (~90°C), which minimizes the WHR from a heat source that represents between 20% and 30% of the fuel energy. The current research proposes increasing the engine coolant temperature to improve the utilization of coolant waste heat as one possible path to achieving greater WHR system effectiveness. An experiment was performed to evaluate the effects of running a diesel engine at elevated coolant temperatures and to estimate the efficiency benefits. An energy balance was performed on a modified 3-cylinder diesel engine at six different coolant temperatures (90°C, 100°C, 125°C, 150°C, 175°C, and 200°C) to determine the change in quantity and quality of waste heat as the coolant temperature increased. The waste heat was measured using the flow rates and temperature differences of the coolant, engine oil, and exhaust flow streams into and out of the engine. Custom cooling and engine oil systems were fabricated to provide adequate adjustment to achieve target coolant and oil temperatures and large enough temperature differences across the engine to reduce uncertainty. Changes to exhaust emissions were recorded using a 5-gas analyzer. The engine condition was also monitored throughout the tests by engine compression testing, oil analysis, and a complete teardown and inspection after testing was completed. The integrity of the head gasket seal proved to be a significant problem and leakage of engine coolant into the combustion chamber was detected when testing ended. The post-test teardown revealed problems with oil breakdown at locations where temperatures were highest, with accompanying component wear. The results from the experiment were then used as inputs for a WHR system model using ethanol as the working fluid, which provided estimates of system output and improvement in efficiency. Thermodynamic models were created for eight different WHR systems with coolant temperatures of 90°C, 150°C, 175°C, and 200°C and condenser temperatures of 60°C and 90°C at a single operating point of 3100 rpm and 24 N-m of torque. The models estimated that WHR output for both condenser temperatures would increase by over 100% when the coolant temperature was increased from 90°C to 200°C. This increased WHR output translated to relative efficiency gains as high as 31.0% for the 60°C condenser temperature and 24.2% for the 90°C condenser temperature over the baseline engine efficiency at 90°C. Individual heat exchanger models were created to estimate the footprint for a WHR system for each of the eight systems. When the coolant temperature increased from 90°C to 200°C, the total heat exchanger volume increased from 16.6 × 103 cm3 to 17.1 × 103 cm3 with a 60°C condenser temperature, but decreased from 15.1 × 103 cm3 to 14.2 × 103 cm3 with a 90°C condenser temperature. For all cases, increasing the coolant temperature resulted in an improvement in the efficiency gain for each cubic meter of heat exchanger volume required. Additionally, the engine oil coolers represented a significant portion of the required heat exchanger volume due to abnormally low engine oil temperatures during the experiment (~80°C). Future studies should focus on allowing the engine oil to reach higher operating temperatures which would decrease the heat rejected to the engine oil and reduce the heat duty for the oil coolers resulting in reduced oil cooler volume.