Mountain Scholar :: Browsing by Author "Marchese, Anthony, advisor"

Browsing by Author "Marchese, Anthony, advisor"

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Open Access
A personal thermophoretic sampler for airborne nanoparticles
(Colorado State University. Libraries, 2010) Thayer, Daniel Lee, author; Marchese, Anthony, advisor; Volckens, John, advisor; Popat, Ketul, committee member; Prieto, Amy, committee member
Engineered nanoparticles are materials with at least one dimension measuring less than 100 nm that are designed on the molecular scale to produce unique or enhanced properties that differ from the bulk material. However, the same properties that make engineered nanoparticles attractive to industry also may present potential health risks to the workers who manufacture them. Very little human exposure data exist for these particles, although they are known enter the body through a number of routes (e.g., respiration, dermal penetrations, and ingestion). Nanoparticles that enter the body can also translocate from one organ to another by virtue of their small size. A cost-effective personal sampler is necessary to evaluate levels of worker exposure to these materials to determine the relative levels of individual risk. Such a sampler must be capable of collecting nanoparticles with high efficiency for subsequent analysis of size, surface chemistry, morphology, and other properties. In addition, the sampler must be able to differentiate between incidental nanoparticles, which are nanoparticles that are naturally present in the environment, and engineered nanoparticles. As detailed in this thesis, a small thermal precipitator was designed to measure breathing-zone concentrations of airborne nanoparticles. The thermal precipitator samples aerosol by producing a 1000 °C cm ' temperature gradient between two aluminum plates (0.1 cm separation distance) using a resistive heater, a thermoelectric cooler, a temperature controller, and two thermistor sensors. The collection efficiency was evaluated for 15, 51, 100, and 240 nm particles at flow rates of 5 and 20 mL/min. Tests were also performed with a zero temperature gradient to determine losses in the device for measurement correction. The homogeneity of particle collection across the collection surface was evaluated using electron microscopy and imaging software. The results indicate that thermal precipitation is a feasible approach for personal monitoring of airborne nanoparticle concentrations in the workplace.
Open Access
Autoigntion and flame speed of premixed liquefied petroleum gas in a rapid compression machine: experimental results and reduced chemical kinetic mechanism
(Colorado State University. Libraries, 2023) Slunecka, Colin, author; Olsen, Daniel, advisor; Marchese, Anthony, advisor; Windom, Bret, committee member; von Fischer, Joe, committee member
Liquefied petroleum gas (LPG) has many properties that make it an attractive alternative fuel such as lower cost than conventional fuels and an established distribution infrastructure. The development of high efficiency, spark ignited LPG engines is currently limited by engine knock and misfire. The knock and misfire limits are further complicated by the wide range of chemical reactivity in LPG, particularly in international markets. In this study, a rapid compression machine (RCM) was used to characterize the effects of variation in LPG fuel reactivity, equivalence ratio, and exhaust gas recirculation (EGR) on the autoignition and flame speeds of LPG/oxidizer/inert/EGR blends. Experiments were conducted with 100% propane and blends of propane with propene, ethane, isobutane, or n-butane. EGR was simulated with mixtures of Ar, CO2, CO, and NO at substitution percentages from 0 to 30 mass percent. Equivalence ratio was varied from 0.75 to 1.5. Ignition delay period under homogeneous autoignition conditions was measured at compressed pressures and temperatures of 23 to 25 bar and 701 to 921 K, respectively. Laminar flame speeds and apparent heat release rates (AHRR) at 24 bar with mixture temperatures of 700 K or 867 K were obtained by firing a laser ignition system into the reaction chamber shortly after compression and analyzing the propagating flame with high speed schlieren imaging. Zero-dimensional simulations of published autoignition experiments were performed using Chemkin-Pro with several detailed chemical kinetic mechanisms to determine their suitability at predicting ignition delay periods. Multiple reduced chemical kinetic mechanisms were created from the NUIGMech1.1 mechanism to determine the optimal balance between accuracy and computational efficiency for future three-dimensional, time-dependent spark-ignited engine simulations. The chosen reduction, ALPINE 153, was used to model ignition delay periods and flame speeds measured in the RCM during this study.
Open Access
Corrosion testing of alloys for biomass cookstove combustors
(Colorado State University. Libraries, 2017) Banta, Kelly, author; Marchese, Anthony, advisor; Mizia, John, committee member; Jathar, Shantanu, committee member; Sambur, Justin, committee member
Worldwide, over 3 billion people use biomass for cooking and heating. Many people cook over 3-stone fires or inefficient and highly polluting traditional cookstoves, presenting a large human health risk and significant climate impacts. One solution to this is the development of improved cookstoves, which can alleviate this burden by being more efficient and cleaner-burning. To be effective in their purpose, improved cookstoves must be long-lasting. Achieving longevity is challenging from a material corrosion perspective, particularly in the case of metallic combustors, because cookstove combustors must operate at high temperatures (> 600 deg. C) in environments with corrosive species released from biomass combustion. A key part of this challenge is cost, since materials must be inexpensive to permit widespread adoption in the developing world; however, corrosion resistant materials are typically costlier. In this work, screening protocols for corrosion testing of cookstove combustor materials were developed and shown to be effective methods for accelerated corrosion testing, and a number of alloys were evaluated for corrosion performance. Additionally, a FeCrSi alloy was identified as a potentially low-cost material with high corrosion resistance in cookstove applications. This alloy is currently being patented.
Open Access
Design and fabrication of a 3-D printable counter-flow/precipitation heat exchanger for use with a novel off-grid solid state refrigeration system
(Colorado State University. Libraries, 2016) Ryan, Sean Thomas, author; Marchese, Anthony, advisor; Kirkpatrick, Allan, committee member; Sharvelle, Sybil, committee member
Off-grid refrigeration technologies are currently limited to either vapor-compression cycles driven by photovoltaics or solar thermal absorption cycles. Rebound Technologies has recently developed a novel off-grid refrigeration system called SunchillTM for agricultural applications in humid environments in the developing world. The SunchillTM refrigeration system utilizes the daily high and low temperatures to drive a 24 hour refrigeration cycle. Cooling is provided by the dissolution of an endothermic salt, sodium carbonate decahydrate. Once the salt is solvated and cooling is delivered to freshly harvest crops, the system is “recharged” in a multi-step process that relies on a solar collector, an air-gap membrane unit and a heat exchanger. The heat exchanger, which is the focus of this thesis, is required to remove 36.6 MJ of heat over a twelve hour period in order to “recharge” the system. The heat exchanger is also required to transfer heat from a fresh water stream to a cold brine solution to generate the cold water necessary to submerse and cool harvested crops. To provide a sustainable technology to the target community, the feasibility of fabricating the heat exchanger via the low cost 3-D printing method of fused filament fabrication (FFF) was examined. This thesis presents the design, development, and manufacturing considerations that were performed in support of developing a waterproof, counter-flow, 3-D printable heat exchanger. Initial geometries and performance were modeled by constructing a linear thermal resistance network with truncating temperatures of 30°C (saturated brine temperature) and 18°C (average daily low temperature). The required surface area of the heat exchanger was found to be 20.46 m2 to remove the required 36.6 MJ of heat. Iterative print tests were conducted to arrive at the wall thickness, hexagon shape, and double wall structure of the heat exchanger. A laboratory-scale heat exchanger was fabricated using a Lulzbot Taz 4 printer from acrylonitrile butadiene styrene (ABS) polymer. Performance was verified empirically for the laboratory-scale unit. A heat transfer rate of 22.8 W was obtained at a flow rate of 0.00075 kg/s. The results of this thesis demonstrate the feasibility of manufacturing low cost heat exchangers using additive manufacturing techniques.
Open Access
Development of a combustion system for fecal materials
(Colorado State University. Libraries, 2017) Flagge, Maxwell, author; Marchese, Anthony, advisor; Mizia, John, committee member; Jathar, Shantanu, committee member; Magzamen, Sheryl, committee member
CSU is working with Research Triangle Institute on the Reinvent the Toilet Challenge (RTTC) to develop a fecal matter combustion system. The proposed system will dry, pelletize and combust fecal matter from a community bathroom in a net zero energy consumption process. This technology has the potential to reduce disease by improving sanitation in rural villages that lack modern plumbing. This research is aimed at helping the 2.5 billion individuals in the world who lack modern plumbing and sanitation facilities. Many villages have nothing more than a concrete pit for defecation, and some individuals have no alternative to open defecation, which creates a huge potential for disease transmission. If individuals could safely burn away their fecal material without using any external energy or resources, the instances of sanitation-related disease could be greatly reduced. In this project, CSU's primary tasks are the optimization and automation of fecal combustion technology. The current combustor design is a modified continuous feed downdraft gasifier. Through a series of tests and measurements, several modifications and improvements have been made to the combustor and its control system, allowing the system to burn fecal materials cleanly and efficiently, while ensuring the destruction of any disease-causing pathogens or bacteria.
Open Access
Development of a Martian in-situ hybrid rocket motor
(Colorado State University. Libraries, 2020) Babazadeh, Iman Andrew, author; Marchese, Anthony, advisor; Mizia, John, advisor; Bareither, Christopher, committee member
One of the chief obstacles that has prevented a human mission to Mars is the excessive amount of mass that must be launched into low earth orbit to assemble the Mars-bound spacecraft. Since propellants alone account for 75% of the total mass requirements, a new concept has been proposed for both manned missions and unmanned robotic sample return missions, which relies on In-Situ Resource Utilization wherein propellants for the return trip to Earth are manufactured from raw materials available on Mars. This research focused on the development and testing of a unique propulsion system that could enable in-situ use of the Martian atmosphere as an oxidizer source and Martian soil as a fuel source for the return journey back to Earth for manned and unmanned vehicles. The propulsion system employs carbon dioxide as an oxidizer and metals as the fuel component. The need to understand and test this concept is significant as there is currently little experimental knowledge on the performance of carbon dioxide oxidizer and metallic fuels in rocket engines. Aluminum and magnesium fuels are the leading choice for burning with carbon dioxide as they can liberate the contained oxygen for rapid combustion to occur. Magnesium is favorable for its ignitability characteristics, whereas aluminum has a higher energy density but is more difficult to ignite due to the formation of its oxide layer. In the research conducted for this thesis, aluminum and magnesium particles were both considered to determine an optimal system that could be used to model an actual Mars propulsion system. The project entailed a myriad of combustion tests based on a conventional hybrid rocket motor in which the metallic fuel particles were encased in a polymer matrix binder and oxidized through a liquid oxidizer. The hybrid rocket motor configuration is not only amenable for the Mars environment because of ease of storage, but also afforded great adaptability safety for the experimental studies described here because of the simplicity of refueling procedures and because the fuel component itself aids in keeping the combustion chamber wall cool, thereby eliminating the need for an active cooling system. Through initial testing, it was observed that adding an additional oxidizer aided in the combustion of carbon dioxide with high percentage metal fuel grains. Specifically, the results of this study suggest that using nitrous oxide as a complementary oxidizer was beneficial in attaining sustained combustion. However, it was also found that miscibility and mixing issues between the carbon dioxide and nitrous oxide oxidizers led to induced combustion instability during the hybrid test fires that had a 50% carbon dioxide and 50% nitrous oxide mixture ratio.
Open Access
Development of a plume identification algorithm for optical gas imaging of natural gas emissions that requires no human intervention
(Colorado State University. Libraries, 2020) Martinez, Marcus M., author; Zimmerle, Daniel, advisor; Marchese, Anthony, advisor; von Fischer, Joe, committee member
Recent growth in natural gas production in the United States has increased focus on reducing greenhouse gas emissions from the natural gas supply chain. Methane, the primary constituent of natural gas, is also a potent greenhouse gas. Optical gas imaging (OGI) is frequently used for emission detection in upstream and midstream sectors of the natural gas supply chain. Current OGI methods typically use mid-range infrared video cameras tuned to absorption lines of light hydrocarbons to make natural gas emissions visible to human operators. Prior studies of camera output have used human interpretation to determine if an emission is visible in the video stream, making it difficult to standardize measures of visibility between tests or to automate large test suites. This work presents a signal processing method which separates the background scene from the gas plume when used in controlled test conditions where video is collected in both leaking and non-leaking conditions. The method utilizes a novel frequency-based method that detects the high-frequency motion of the gas plume in the video stream. After background removal, the size of the gas plume can be quantified by thresholding the detected plume and measuring its size relative to the camera's field of view. The resulting metric eliminates the need for human evaluation of video streams. To demonstrate application of the method, multiple cameras were used to develop a relationship between emission rate and plume visibility over a range of viewing distances. Tests were conducted at the Methane Emissions Technology Evaluation Center, on CSU's Foothills Campus, using six identical OGI cameras (FLIR G300a camera cores with 38 mm lenses) to image the emission from multiple directions at a range 1 to 6 m. Gas was released from a mock well head at 17 to 196 g/h, with wind speeds of 1.8 to 3.0 m/s. Comparison with expert evaluation was used to set and validate the threshold levels; a 90% probability of detection requires a plume covering at least 13.8% of the camera's field of view. Testing indicated a linear relationship between emission rate and plume coverage fractions at a distance of 1 to 2 m, regardless of the viewing angle. Beyond 2 m, plume coverage drops rapidly, approaching the noise floor. While test conditions were limited, sufficient data was collected to demonstrate method functionality and its applicability to evaluating OGI emission detection systems.
Open Access
Dual-fuel combustion of hydrocarbon fuel droplets in lean, premixed methane/oxidizer mixtures in a rapid compression machine
(Colorado State University. Libraries, 2018) Gould, Colin M., author; Marchese, Anthony, advisor; Windom, Bret, committee member; Dandy, David, committee member
The combustion of two fuels with disparate reactivity (dual-fuel) has been shown to be an effective method for increasing fuel efficiency and reducing both fuel costs and pollutant formation in internal combustion engines. Due to recent decreases in the price of natural gas, the incentive has grown to operate engines in dual-fuel mode, where some amount of diesel is substituted with natural gas. Since natural gas is expected to remain less expensive on a per-unit-energy basis than diesel fuel for the foreseeable future, it will continue to be economically advantageous to maximize the substitution percentage of natural gas in dual-fuel engines. However, at higher natural gas substitution percentages, uncontrolled fast combustion (i.e. engine knock) can occur, which limits the load of the engine and can shorten the lifetime of engine components. Emission of unburned methane has also been shown to increase with increasing natural gas substitution percentage. Previous detailed computational engine modeling at CSU with reduced chemical kinetics and simplified spray models has captured these effects but little data are available to validate chemistry and spray models at engine-relevant conditions. In this study, a rapid compression machine (RCM) was used as a platform to provide a high-temperature/high-pressure environment to better understand the thermodynamic, transport and chemical kinetic phenomena of dual-fuel combustion. The RCM was modified to perform evaporation and combustion experiments on single n-alkane fuel droplets in gaseous inert, O2/inert and O2/CH4/inert environments. Droplet evaporation experiments were performed on C5 to C12 n-alkane droplets in inert gas to measure droplet evaporation rates at near supercritical and supercritical conditions (18 bar < P < 35 bar; 450 K < T < 850 K). The Dual-fuel droplet evaporation and combustion experiments were studied using pressure data and images collected a Schlieren optical system. In the combustion experiments, ignition delay of heptane/O2/inert was quantified at elevated pressure and temperature (27 bar < P < 38 bar; 844 K < T < 1251 K). In addition, the process of dual-fuel combustion was captured, showing two distinct ignition events.
Open Access
Effect of additives on laser ignition and compression ignition of methane and hydrocarbons in a rapid compression machine
(Colorado State University. Libraries, 2016) Boissiere, Andrew, author; Marchese, Anthony, advisor; Yalin, Azer, advisor; Van Orden, Alan, committee member
Despite recent efforts to develop new energy systems that do not rely on combustion of fossil fuels, internal combustion (IC) engines powered on fossil fuels (i.e. gasoline, diesel or natural gas) will remain as an integral component of the global energy portfolio for years to come and increasing the efficiency of IC engines will be a necessary means to reduce fossil fuel consumption and greenhouse gas emissions. In this study, the effect of fuel additives on natural gas and gasoline spark ignited engines were investigated using laser ignition and compression ignition experiments performed in a rapid compression machine (RCM). The goal of the laser ignition study was to examine the effect of additives to extend the lean limit of natural gas engines, while the goal of the compression ignition experiments were to examine the ability of fuel additives to decrease knock propensity of gasoline fuels. For the laser ignition study, methane/air mixtures containing various fuel additives at temperatures and pressures representative of the compressed conditions inside an internal combustion engine were ignited in the RCM. An Nd:YAG laser operating at a wavelength of 1064 nm was used to ignite methane/air mixtures ranging in equivalence ratio from stoichiometric down to 0.4 using a rapid compression machine (RCM). Experiments were conducted to determine the lean limit, minimum spark energy (MSE), and minimum ignition energy (MIE). Three different fuel additives at varying concentrations were tested. The results show that laser ignition exhibits a stochastic behavior which must be interpreted statistically. A 90% probability of occurrence is used to evaluate the MSE and MIE which resulted in MSE90=2.3 mJ and MIE90=7.2 mJ for methane/air mixtures of equivalence ratio equal to 0.4. The lean limit, defined as greater than 90% of the theoretically possible heat release, was found as equivalence ratio of 0.47 for methane/air mixtures. All three fuel additives resulted in a reduction of the baseline methane/air MIE, while only DTBP and NM resulted in a reduction of the lean limit. For the compression ignition study, the effects of various fuel additives on the auto-ignition characteristics of gasoline reference fuels were studied in the RCM. Fuel additives were added to stoichiometric fuel/air mixtures of liquid gasoline surrogate fuels and were auto-ignited in a RCM. Experiments were conducted to determine the ignition delay, heat release rate, and net heat release of the gasoline surrogate/air mixtures with and without fuel additives. Five different gasoline fuel additives were tested in an Iso-Octane and Toluene Reference base fuel. The results show that the majority of the additives increased the reactivity and decreased the ignition delays of the base fuels. However, a select few of the tested additives decreased the reactivity and increased the ignition delays of the base fuel at select conditions, which could be beneficial to increasing the efficiency of internal combustion engines.
Open Access
End-gas autoignition propensity and flame propagation rate measurements in laser-ignited rapid compression machine experiments
(Colorado State University. Libraries, 2019) Zdanowicz, Andrew, author; Marchese, Anthony, advisor; Windom, Bret, committee member; Hampson, Greg, committee member; Reardon, Ken, committee member
Knock in spark-ignited (SI) engines is initiated by autoignition and detonation in the unburned gases upstream of spark-ignited, propagating, turbulent premixed flames. Knock propensity of fuel/air mixtures is typically quantified using research octane number (RON), motor octane number (MON), or methane number (MN; for gaseous fuels), which are measured using single-cylinder, variable compression ratio engines. In this study, knock propensity of SI fuels was quantified via observations of end-gas autoignition (EGAI) in unburned gases upstream of laser-ignited, premixed flames at elevated pressures and temperatures in a rapid compression machine. Stoichiometric primary reference fuel (PRF; n-heptane/isooctane) blends of varying reactivity (50 ≤ PRF ≤ 100) were ignited using an Nd:YAG laser over a range of temperatures and pressures, all in excess of 545 K and 16.1 bar. Laser-ignition produced outwardly-propagating premixed flames. High-speed pressure measurements and schlieren images indicated the presence of EGAI. The fraction of the total heat release attributed to EGAI (i.e., EGAI fraction) varied strongly with fuel reactivity (i.e., octane number) and the time-integrated temperature in the end-gas prior to ignition. Flame propagation rates, which were measured using schlieren images, did not vary strongly with octane number but were affected by turbulence caused by variation in piston timing. Under conditions of low turbulence, measured flame propagation rates agreed with the theoretical premixed laminar flame speeds quantified by 1-D calculations performed at the same conditions. Experiments were compared to a three-dimensional CONVERGE™ model with reduced chemical kinetics. Model results accurately captured the measured flame propagation rates, as well as the variation in EGAI fraction with fuel reactivity and time-integrated end-gas temperature. Model results also revealed low-temperature heat release and hydrogen peroxide formation in the end-gas upstream of the propagating laminar flame, which increased the temperature and degree of chain branching in the end-gas and ultimately led to EGAI.
Open Access
FTIR spectroscopy of methyl butanoate-air and propane-air low pressure flat flames
(Colorado State University. Libraries, 2012) Naber, Kristen Ann, author; Marchese, Anthony, advisor; Catton, Kimberly, committee member; Gao, Xinfeng, committee member
The combustion of fatty acid methyl esters (FAME) in diesel engines has been shown to produce lower emissions of carbon monoxide (CO), unburned hydrocarbons, greenhouse carbon dioxide (CO2), and particulate matter than petroleum based fuels. However, most diesel engine studies have shown that emission of oxides of nitrogen (NOx) typically increase for methyl ester fuels in comparison to petroleum based fuels. Many theories have been proposed to explain these NOx increases from FAME combustion but a general consensus has emerged toward two primary mechanisms: (1) the increased bulk modulus of biodiesel results in earlier fuel injection into the cylinder and/or (2) the presence of oxygen in the fuel results in a leaner (but still rich) premixed autoignition zone thereby increasing the local flame temperature during the premixed burn phase. It is well known that NOx is produced during the combustion of hydrocarbons in air from three different mechanisms: prompt NOx, thermal NOx, and via fuel bound nitrogen. Both of the mechanisms that have been proposed to explain the observed NOx increases from the combustion of FAME in diesel engines are related to the thermal NOx production route. However, no quantitative data exist on local in-cylinder temperatures and associated in-cylinder NO production during the premixed autoignition phase to experimentally verify these hypotheses. The present work is aimed at developing an experimental approach to examine a third hypothesis that suggests that the chemical structure of methyl esters results in an increase in prompt NOx in comparison to non-oxygenated hydrocarbons. This new hypothesis has the potential to be verified by conducting experiments with steady, laminar flames. Accordingly, in the present study, low pressure, flat flame burner experiments were conducted, which enabled direct temperature measurements using a thermocouple and direct species sampling using a quartz microprobe. The fuels used in the flame experiments were propane (C3H8) and methyl butanoate (C5H10O2), a small methyl ester fuel whose chemical kinetic mechanism has been the subject of substantial research in the past decade. The gas samples were directed to an FTIR spectrometer for analysis of various species including NO, CO, and CO2. Equivalence ratios of φ = 0.8, 1.0, and 1.2 were examined for both fuels. Temperatures were obtained using coated Pt-Pt/13%Rh type R thermocouples and were corrected for radiation losses. In addition to the experiments, laminar flame modeling studies were conducted using CHEMKIN for the both fuel types at each equivalence ratio using existing detailed chemical kinetic mechanisms to predict temperature and species concentrations. Because no methyl butanoate mechanisms containing detailed NOx chemistry exist, the propane/NOx chemical kinetic mechanism of Konnov and was combined with a detailed methyl butanoate mechanism Gail and coworkers. Experimental and modeling results show that nitric oxide production in the steady, premixed laminar methyl butanoate flames did not differ substantially from that produced in similar propane flames. Results were inconclusive on which nitric oxide formation mechanisms contributed to the overall measured concentrations.
Open Access
Implications of cell composition and size on the performance of microalgae ultrasonic harvesting
(Colorado State University. Libraries, 2018) Aligata, Alyssa Jean, author; Marchese, Anthony, advisor; Quinn, Jason, advisor; Peebles, Christie, committee member
Substantial economic challenges exist across the value chain for microalgae-based biofuels and bioproducts. Acoustic harvesting could dramatically reduce harvesting costs and directly address current energy barriers to separating algae from growth media. This technology utilizes ultrasonic standing waves to create an acoustic radiation force that, due to differences in the acoustic properties of the cells and media, causes the microalgae cells to agglomerate and settle out of the solution. The magnitude of the acoustic radiation force is directly related to the cell radius and acoustic contrast factor (ACF), the latter of which is a function of the density and compressibility of the cell. These properties can vary widely depending on the algae species, cultivation conditions, and growth stage—all of which affect the composition of the microalgae cells (e.g., lipid, carbohydrate, protein content). In this work, two methods were used to determine the ACF of microalgal cells: 1) a property measurement approach and 2) a particle tracking approach. The first method involved experimentally measuring the size distribution, density and compressibility of the cells and calculating the ACF. The second method utilized particle tracking velocimetry and a COMSOL Multiphysics model to estimate the ACF. The ACF was characterized, using both techniques, for three species—Chlamydomonas reinhardtii, Nannochloropsis salina, and Tetraselmis chuii—as a function of dynamic cellular composition over a 2-week growth period. For C. reinhardtii the lipid content increased from 26% ± 1% to 40% ± 1% from day 3 to 9, which resulted in a 43% decrease in ACF (0.056 ± 0.003 to 0.032 ± 0.001). For N. salina the lipid content increased from 25% ± 1% to 33% ± 1% from day 3 to 10, which also resulted in a 43% decrease in ACF (0.040 ± 0.002 to 0.023 ± 0.001). For T. chuii the lipid content remained relatively stable (~10%) throughout the growth period so the ACF (~0.3) did not change significantly. ACF decreases as lipid content increases because lipids have a negative ACF in growth media, whereas carbohydrates and proteins have a positive ACF. However, cell size can have a greater impact on an algal strains' responsiveness to acoustic harvesting because the net force is proportional to Φa2. Furthermore, acoustic harvesting works best for large diameter cells, provided that those cells have a nonzero ACF. T. chuii had the largest cell diameter of approximately 12 µm, while C. reinhardtii and N. salina had cell diameters of 8.5 µm and 4.3 µm, respectively. The Φa2 values for T. chuii were approximately 50× higher than the values for N. salina, which is largely due to T. chuii cells having a diameter that is 3× the diameter of N. salina cells. Composition also contributed to the higher Φa2 values for T. chuii since these cells were composed of mostly carbohydrates and had an ACF that was an order of magnitude higher than the ACF of N. salina. This research shows that acoustic harvesting has the potential to positively impact the algal biofuels value chain through the reduction of energy required for harvesting.
Open Access
Improved characterization of natural gas leak plumes using a Laplace transform approach to correct for instrument response time
(Colorado State University. Libraries, 2021) O'Brien, Thomas E., author; Marchese, Anthony, advisor; von Fischer, Joe, advisor; Abutayeh, Mohammad, committee member; Weller, Zachary, committee member
The response time of an instrument is a measure of how quickly it achieves a steady-state value in response to a step change input. The response time directly affects the accuracy of reported values when the instrument is subject to transient conditions. In methane leak surveying, methane gas concentrations are often measured from instruments mounted in moving vehicles. The methane concentrations detected by those instruments are therefore constantly varying. Depending on the physical size of the methane plume, vehicle speed and instrument response time, a vehicle-mounted instrument may or may not reach a steady-state value as the instrument inlet traverses the plume, which can result in an underestimation of the true ambient gas concentration of the plume. For leak detection techniques that rely on downwind concentration measurements to estimate an emission rate and/or detect the presence of a methane emission source, this issue can result in underestimation of emission rates and/or failure to detect an emission source. Further complicating these efforts, different gas analyzers often have different time response characteristics, resulting in an ambiguity in readings achieved by different instruments. In this research, a model was developed to generate improved estimates of the actual gas concentration values and waveform shapes using Laplace transforms, given the time response characteristics of the instruments. Several methane gas analysis instruments used for methane leak detection surveying were experimentally characterized in a laboratory setting to determine their time response characteristics. Controlled release field testing in conjunction with simultaneous methane measurements from multiple instruments mounted on the same moving vehicle were then used to validate this methodology. During field testing, instruments with different response characteristics were plumbed in parallel, thereby sampling the same air stream. The results indicated that the instrument with a faster response time consistently reported significantly higher peak methane concentrations than the slower response instrument. However, by applying the model developed in this study to the raw time-varying gas concentration data, the corrected concentration profiles for the two instruments were found to be nearly identical. The results also indicate that the raw signals from both instruments underrepresented the actual peak methane concentrations for the majority of detected plumes. The results of this study suggest the importance of accurately accounting for instrument time response in downwind, vehicle-mounted methane measurement techniques to ensure that peak methane concentrations are not underreported.
Open Access
Methods for particulate matter emissions reduction in wood burning cookstoves
(Colorado State University. Libraries, 2015) Dischino, Kevin, author; Marchese, Anthony, advisor; Pierce, Jeffrey, committee member; Volckens, John, committee member
About 3 billion people cook by burning biomass. Most use inefficient cooking technologies that lead to high levels of domestic air pollution. This results in tremendous damages to human and environmental health. For example, in 2012 the World Health Organization estimated that 4.3 million people died prematurely from illnesses attributable to inefficient household use of biomass fuels.
Open Access
Modeling ablative and regenerative cooling systems for an ethylene/ethane/nitrous oxide liquid fuel rocket engine
(Colorado State University. Libraries, 2020) Browne, Elizabeth C., author; Marchese, Anthony, advisor; Windom, Bret, advisor; Watson, Ted, committee member
Rocket engines create extreme conditions for any material to withstand. The combustion temperatures in rocket engines are substantially greater than the melting points of metals, and wall temperatures must be maintained well below the melting point to ensure structural integrity. This requirement necessitates a robust cooling system for the combustion chamber and nozzle to endure the mandated burn times. A liquid rocket engine utilizing ethane/ethylene as the fuel and nitrous oxide as the oxidizer, which is currently under development by Pioneer Astronautics, required a detailed analysis of thrust chamber cooling options. Due to the impracticality of experimentally validating the performance of each design parameter, this thesis employed computational methods to investigate two common cooling systems for rocket engines - ablative and regenerative - to determine their effectiveness at 130 and 200 chamber pressures, as prescribed by Pioneer Astronautics. Additional 1000-psi chamber pressure models were investigated for prediction validation. An analytical model was developed and utilized to elucidate the behavior of both cooling methods, while regenerative cooling was additionally analyzed using numerical modeling, coupling finite element analysis (FEA) and computational fluid dynamics (CFD) software. Simulations were created of the fluid dynamics and heat transfer within the rocket engine and coolant channels for numerous regenerative designs. The designs examined included a single-channel model utilizing only the liquid ethylene/ethane fuel as the coolant, and a dual-channel model using both the fuel and the nitrous oxide as coolants in separate sets of channels. In the single-channel regenerative cooling design, both the analytical and numerical models exhibited insufficient cooling capacity with coolant temperatures of 3-11 K above the critical temperature of 292.5 K. However, the dual-channel model provided the supplemental thermal energy absorption necessary to maintain engine wall and coolant temperatures within the allowable limits. From a design and manufacturing standpoint, ablative cooling is far simpler to implement than regenerative cooling. Although, material erosion at the throat reduces engine performance over time. Integrating ablative cooling in the combustion chamber and nozzle bell with dual-channel regenerative cooling near the throat has the potential to provide the requisite heat removal to ensure sustained material strength while maintaining all reactants in a condensed liquid phase.
Open Access
Optimization of daytime fuel consumption for a hybrid diesel and photovoltaic industrial micro-grid
(Colorado State University. Libraries, 2017) Dufrane, Stacey, author; Marchese, Anthony, advisor; Zimmerle, Daniel, advisor; Suryanarayanan, Siddharth, committee member; Bradley, Thomas, committee member
The work to be presented will examine the optimization of daytime diesel fuel consumption for a hybrid diesel and photovoltaic (PV) industrial micro-grid with no energy storage. The micro-grid utilizes a control system developed to forecast PV transients and manage the diesel generators providing electrical supply to the micro-grid. The work focuses on optimization of daytime fuel consumption when PV generation is available. Simulations were utilized to minimize diesel consumption while maintaining secure operations by controlling both PV curtailment and diesel generation. The control system utilizes a cloud forecast system based upon sky imaging, developed by CSIRO (Australia), to predict the presence of cloud cover in concentric "rings" around the sun's position in the sky. The control system utilizes these cloud detections to establish supervisory settings for PV and diesel generation. Work included methods to optimize control response for the number of rings around the sun, studied the use of two different sizes of generators to allow for increased PV utilization, and modification of generator controller settings to reduce fault occurrence. The work indicates that increasing the number of rings used to create the PV forecast has the greatest impact on reducing the number of faults, while having a minimal impact on the total diesel consumption. Additionally, increasing the total number of generators in the system increases PV utilization and decreases fuel consumption.
Open Access
Statistical analysis of the challenges to high penetration of wind energy
(Colorado State University. Libraries, 2014) O'Connell, Matthew, author; Marchese, Anthony, advisor; Zimmerle, Daniel, advisor; Young, Peter, committee member
Grid penetration of renewable energy technologies, especially wind power, is higher than ever and continues to increase. The inherent stochastic variability of wind makes predicting wind, and thus power generation difficult. Generating companies usually don't openly share power output predictions or historical generation data which increases the level of complexity when determining new wind plant locations or estimating delivered grid level power. This work focuses on statistical data analysis and advanced data modeling related to wind power forecasting and generation. The first part of this thesis uses power output logs from several wind plants and a well-known forecasting method to determine energy storage requirements for individual wind plant contract firming. Forecasts of varying accuracy are used to characterize storage requirements based on contract period length, forecast lead time, and forecast accuracy. Results show that forecast error distributions are effected more by forecast accuracy and lead time than wind plant size and location. The biggest reductions in produced power deviations can be achieved by increasing forecast accuracy and decreasing forecast lead time. The second part of this work develops a statistical analysis which allows estimation of contract firming requirements for a specific wind plant location without the need for time series wind and forecast data. The developed method requires only a wind speed and forecasting error distribution. Using these distributions, deviations between forecast to produced power and energy can be estimated. Results from comparing to historical time series data show this method is accurate to within 10% of actual amounts. Since distributions are much more easily attained than historical time series data, this analysis is useful for developers when evaluating potential new locations. The third part of this work uses a pattern matching algorithm to recognize wind ramp events and separate the forecasting error due to timing from the forecasting error due to magnitude. Wind ramp detection is achieved by developing a pattern matching algorithm which is also shown to work in identifying start and stop transients in electrical device current draw. The analysis confirms wind ramp events can be detected by calculating a bimodal ranking value from a histogram of power data, and the effects of forecast timing and magnitude can be separated from overall forecasting errors. The results of this analysis show magnitude errors contribute more in large wind ramp events, while timing errors contribute more in small ramp events.
Open Access
The effect of fuel additives in a natural gas and gasoline engine
(Colorado State University. Libraries, 2016) Falloon, Thomas, author; Marchese, Anthony, advisor; Olsen, Daniel, advisor; Reardon, Kenneth, committee member
Fuel additives are used worldwide for a variety of applications including increasing fuel efficiency, decreasing emissions, decreasing knock propensity and/or modifying storage/handling properties. Because of the high percentage of global fossil fuel consumption attributed to internal combustion engines, fuel additives that increase the efficiency of fossil fuel powered internal combustion engines can greatly impact global fossil fuel consumption and greenhouse gas emissions. In this study, the effect of various fuel additives on spark ignited natural gas and gasoline internal combustion engines was examined. The natural gas work focused primarily on using fuel additives to extend the lean limit, while the gasoline additives work focused on lean limit extension, decreased knock propensity and increased power. Experiments were performed in using a constant speed, single cylinder, variable compression ratio Cooperative Fuel Research (CFR) engine, which has the capability to operate with both gaseous and liquid fuels. The gaseous fuel system used compressed air to simulate a turbocharged engine, while the liquid fuel system used a naturally aspirated carburetor. In-cylinder pressure data were acquired using a high-speed piezoelectric pressure transducer, which is used to calculate indicated power, peak pressure and to quantify engine knock. In this study, four natural gas and three gasoline additives were considered. For the natural gas fuel additives, the primary hypothesis for the fuel additives was that the lean limit would be decreased with the addition of the additives. By holding the power of the engine constant and decreasing the equivalence ratio, this hypothesis was tested and it was concluded that the additives had a negative impact on the lean limit. For the gasoline additives, the hypothesis was that the additives would either increase engine power, decrease the knock propensity (i.e. increase the octane number), or decrease the lean limit. It was found that one of the additives increased engine efficiency slightly and decreased the knock propensity, while the other two gasoline additives had negative impacts on both metrics. One of the gasoline additives appeared to slightly extend the lean limit, but further testing will be required to confirm this result.
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 effects of ambient air-injection on particulate matter emissions in high firepower chimney cookstoves
(Colorado State University. Libraries, 2017) Hogberg, Thor, author; Marchese, Anthony, advisor; L'Orange, Christian, committee member; Collett, Jeffrey, committee member; Jathar, Shantanu, committee member
Approximately 2.8 billion people use solid fuel to cook and heat their homes. The resulting emissions from using solid fuel to cook and heat has detrimental effects on both indoor and outdoor air quality. In 2012 it was estimated that 4.3 million premature deaths occurred from indoor air pollution and 3.7 million deaths occurred from ambient air pollution. In 2009 it was estimated that incomplete combustion and harvesting of solid biofuels combined accounted for 1.9-2.3% of all greenhouse gases and short lived climate forcers. Due to the high firepower of institutional stoves, they produce far greater amounts of particulate matter (PM) than residential cookstoves; despite this fact, they have received little attention in comparison. Technology at the Advanced Biomass Combustion Laboratory has been developed that is capable of reducing PM emissions in high firepower chimney stoves by over 90%, and shifting the elemental to organic carbon ratio (EC/OC) towards a higher organic fraction. These changes were achieved by the use of high velocity air injection directly above the combustion chamber. Air injection nozzle orifice number, diameter, and the mass flow rate of injection air was tested to understand what combination of geometry and flow rate resulted in the best overall emissions reduction. The most significant emissions reductions occurred at high velocities that resulted from nozzles with fewer and smaller holes.