Browsing by Author "Windom, Bret, advisor"
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Item Open Access Development of a low-firepower biomass dust combustor(Colorado State University. Libraries, 2018) Greer, Kyle C., author; Mizia, John, advisor; Windom, Bret, advisor; Ham, Jay, committee memberAs of 2017, the World Health Organization estimates that 2.3 billion people globally lack access to basic sanitation facilities such as toilets or latrines. 892 million of these people defecate in the open, which increases the spread of disease and intestinal parasites. Incinerating desiccated human waste provides a low-cost opportunity to safely mitigate this public health risk. Over the last five years, the Advanced Biomass Combustion lab at CSU has developed a 2-kW fecal gasifier as part of the Gates Reinvent the Toilet Challenge, but the combustor lacks scalability to low firepowers. Continuous low-firepower biomass combustion has eluded development due to several technical challenges, however it is advantageous in many situations and opens the door for many low energy devices. Development of a low-firepower fecal combustor could act as a pilot light for the existing gasifier, it could be a low-cost standalone incinerator for household use, it may have higher combustion efficiencies and lower emissions than the gasifier, and it could be scaled to high firepowers by creating arrays of flames. A 100 Watt idealized biomass dust combustor has been developed to investigate the feasibility of creating a low-firepower fecal dust burner. Despite extensive research on dust explosion dynamics, few stable dust-flame burners have been researched and developed. This project utilized dust combustion fundamentals and iterative hardware development to create a low-firepower biomass dust combustor. Cornstarch, wheat flour, and lycopodium spores were explored as idealized biomass fuels, and human feces was briefly tested in the combustor. The hardware development process will help guide the transition to a stable low-firepower fecal dust burner.Item Open Access Development of a low-firepower continuous feed biomass combustor(Colorado State University. Libraries, 2020) Rayno, Mars, author; Mizia, John, advisor; Windom, Bret, advisor; Carter, Ellison, committee memberApproximately 25% of world's population lacks basic sanitation amenities. This lack of sanitation leads directly to the spread of contagious diseases and parasites. One method that can help mitigate these consequences is the thermal treatment of human feces in a combustion system. Colorado State University's Advanced Biomass Combustion Lab has been working on thermal treatment systems as part of the Bill and Melinda Gates Foundation Reinvent the toilet challenge for over 7 years. The goal is to develop stand-alone treatment technologies that can process waste for less than 5 cents per person per day. Thermal processing is an attractive solution because it not only destroys pathogens, but also significantly reduces the amount of mass that needs to be disposed of. Until recently, the focus has been on larger (2 kW) fecal gasifiers. This scale of combustor was designed to incinerate the solid waste of approximately 28 users per hour. The large amount of users required to operate meant that either fuel would need to be stored before usage or the combustor would be subject to frequent startups and shutdowns. During steady state operation the gasifier emits low quantities of harmful pollutants, but during startup and shutdown the emissions are considerably higher. Thus, there is a need to mitigate or reduce the frequency of those transient events. One way to address this problem is to develop a suite of scaled combustors. A 500 W combustor, for example, would be able to run continuously for 12 hours with 30 users, or 24 hours with 60 users. This project investigated a scaled version of the 2kW fecal combustor developed under the BMGF RTTC. Emission factors for this scaled device were generated for various firepowers, air-fuel ratios, and primary-to-secondary air ratios.Item Open Access Diagnostics and characterization of direct injection of liquified petroleum gas for development of spray models at engine-like conditions(Colorado State University. Libraries, 2023) Sharma, Manav, author; Windom, Bret, advisor; Yalin, Azer, committee member; Yost, Dylan, committee memberResearch within the realm of internal combustion (IC) engines is concentrated on enhancing fuel efficiency and curbing tailpipe emissions, particularly CO2 and regulated pollutants. Promising solutions encompass the utilization of direct injection (DI) and alternative fuels, with liquefied petroleum gas (LPG) standing out as a notable candidate. LPG presents a pragmatic and economical option for fueling the heavy-duty transportation sector in the United States. However, widespread adoption hinges on achieving energy conversion efficiencies in LPG engines comparable to those in diesel engine platforms. The overarching goal of this research is to address fundamental limitations to achieving or surpassing near-diesel efficiencies in heavy-duty on-road liquefied petroleum gas engines. Owing to substantial differences in physical properties compared to traditional fuels, an enhanced understanding and modeling of LPG sprays become imperative. This work conducts an experimental and numerical analysis of direct-injected propane and iso-octane, serving as surrogates for LPG and gasoline, respectively, under diverse engine-like conditions. The overall objective is to establish a baseline for the fuel delivery system required in future high-efficiency DI-LPG heavy-duty engines. Propane, emulating LPG, undergoes injection across various engine-like conditions, encompassing early and late injections, as well as boosted engines, using a range of direct injectors available in both research and commercial domains. Optical diagnostics, including high-speed schlieren and planar Mie scattering imaging, were performed to study the spray penetration, liquid and vapor phase regions, and mixing of propane and to characterize bulk and the plume-specific spray behavior of propane. The study also investigates the influence of injector geometry on spray performance. Iso-octane was used as a surrogate for gasoline, and propane was used to compare LPG's behavior with more conventional DI fuel. The experimental results and high-fidelity internal nozzle-flow simulations were then used to define best practices in computational fluid dynamics (CFD) Lagrangian spray models. Optical imaging revealed that, unlike iso-octane, propane's spray propagation was fed by its flash boiling, spray collapse, and a high degree of vaporization, resulting in a direct proportionality of propane's penetration length to temperature. These unique attributes categorize propane as an unconventional spray, necessitating corrections to injection and breakup models to replicate under-expanded jet dynamics and emulate flash boiling-driven spray development across various research and commercial injectors.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 Embargo Informing methane emissions inventories using facility aerial measurements at midstream natural gas facilities(Colorado State University. Libraries, 2023) Brown, Jenna A., author; Windom, Bret, advisor; Zimmerle, Daniel, advisor; Blanchard, Nathaniel, committee memberIncreased interest in greenhouse gas (GHG) emissions, including recent legislative action and voluntary programs, has increased attention on quantifying, and ultimately reducing, methane emissions from the natural gas supply chain. While inventories used for public or corporate GHG policies have traditionally utilized bottom-up (BU) methods to estimate emissions, the validity of such inventories has been questioned. To align with climate initiatives, multiple reporting programs are transitioning away from BU methods to utilizing full-facility measurements using airborne, satellite or drone (top-down (TD)) techniques to inform, improve, or validate inventories. This study utilized full-facility estimates from two independent TD methods at 15 midstream natural gas facilities in the U.S.A., and were compared with a contemporaneous daily inventory assembled by the facility operator, employing comprehensive inventory methods. Methods produced multiple full-facility methane estimates at each facility, resulting in 801 individual paired estimates (same facility, same day), and robust mean estimates for each facility. Mean estimates for each facility, aggregated across all facilities, differed by 28% [10% to 43%] for the first deployment and nearly 2:1 (49% [32% to 68%]) the second deployment. Estimates from the two TD methods statistically agreed in 12% (97 of 801) of the paired measurements. These data suggest that one or both methods did not produce accurate facility-level estimates, at a majority of facilities and in aggregate across all facilities. Operator inventories, which included extensions to capture sources beyond regular inventory requirements and to integrate local measurements, estimated significantly lower emissions than the TD estimates for 96% (1535 of 1589) of the paired comparisons. Significant disagreement is observed at most facilities, both between the two TD methods and between the TD estimates and operator inventory. Overall results were coupled with two case studies where TD estimates at two pre-selected facilities were coupled with comprehensive onsite measurements to understand factors driving the divergence between TD and BU inventory emissions estimates. In 3 of 4 paired comparisons between the intensive onsite estimates and one of the TD methods, the intensive on-site work did not conclusively diagnose the difference in estimates. In these cases, the preponderance of evidence suggests that the TD methods mis-estimate emissions an unknown fraction of the time, for unknown reasons. The results presented here have two implications. Firstly, these findings have important implications for the construction of voluntary and regulatory reporting programs that rely on emission estimates for reporting, fees or penalties, or for studies using full-facility estimates to aggregate TD emissions to basin or regional estimates. Secondly, the TD full-facility measurement methods need to undergo further testing, characterization, and potential improvement specifically tailored for complex midstream facilities.Item 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 memberRocket 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.Item Open Access Modeling and parametric study of end-gas autoignition to allow the realization of ultra-low emissions, high-efficiency heavy-duty spark-ignited natural gas engines(Colorado State University. Libraries, 2022) Bestel, Diego Bernardi, author; Windom, Bret, advisor; Marchese, Anthony, committee member; Olsen, Daniel, committee member; Bangerth, Wolfgang, committee memberEngine knock and misfire are barriers to pathways leading to high-efficiency Spark-Ignited (SI) Natural Gas (NG) engines. The general tendency to knock is highly dependent on engine operating conditions and the fuel reactivity. The problem is further complicated by the low emission limits and the wide range of chemical reactivity in pipeline-quality natural gas. Depending on the region and the source of the natural gas, its reactivity, described by its Methane Number (MN), which is analogous to the Octane Number for liquid SI fuels, can span from 65 to 95. In order to realize diesel-like efficiencies, SI NG engines must be designed to operate at high Brake Mean Effective Pressures (BMEP), near or beyond knock limits, over a wide range of fuel reactivity. This requires a deep understanding of the combustion-engine interactions pertaining to flame propagation and End-Gas Autoignition (EGAI), i.e., the autoignition of the unburned gas (end gas) ahead of the flame front. However, EGAI, if controlled, provides an opportunity to increase SI NG engine efficiency by increasing the combustion rate and the total fraction of burned fuel, mitigating the effects of the slow flame speeds characteristic of natural gas fuels, which generally reduce BMEP and increase unburned hydrocarbon emissions. For this reason, to realize diesel-like efficiencies and ultra-low emissions on SI NG engines, this work proposes the study of the main parameters influencing the modeling and prediction of NG EGAI to allow for its control. In this work, a novel EGAI detection and onset determination method was developed to reliably quantify EGAI for data analysis and engine control. The new method allowed the prediction of EGAI on SI NG engines without the need to use engine- and operating-condition-dependent thresholds and reduced the error in quantifying the fraction of the total energy released by the EGAI event by up to 40%pts. One- and three-dimensional engine models were then developed to study the engine/fuel interactions that lead to NG EGAI and its performance benefits. These models, although having decent agreement with experimental data, showed the need to account for NOx chemistry when predicting NG EGAI due to a consistently later prediction of the EGAI onset (∼1.65 crank-angle degrees) and thus, a new reduced chemical mechanism for real NG fuels was developed containing NOx chemistry. The new reduced mechanism improved the EGAI onset prediction agreement to within ±0.5 crank-angle degrees and decreased simulation time during combustion by nearly 50% when using the further reduced AREIS50NOx chemical mechanism. These models were then used to study the role of NG composition on EGAI, evaluate the engine/fuel interactions leading to NG EGAI, and perform engine optimization while leveraging EGAI to increase thermal efficiency. Piston design optimization combined with a Controlled EGAI (C-EGAI) combustion mode allowed a Heavy-Duty (HD) SI NG engine to operate at diesel-like efficiencies, i.e., Brake Thermal Efficiency (BTE) ≥44%. Experimental and modeling data analysis revealed that earlier and faster heat release increases combustion efficiency by an average of 1% pts, increases work transferred to the piston resulting in a decrease in exhaust losses by 50% depending on the engine operating condition while slightly increasing heat losses. Finally, the simulation results revealed an opportunity to further enhance the BTE (up to 50%) by enabling C-EGAI combustion at leaner conditions, λ=1.4-1.6.Item Open Access Optimizing energy conversion efficiency of a proton exchange membrane green hydrogen generation system while incorporating balance of plant modeling(Colorado State University. Libraries, 2023) Landin, Nikolas, author; Windom, Bret, advisor; Bradley, Thomas, committee member; Montgomery, David, committee memberHydrogen has the potential to decarbonize several difficult to decarbonize sectors of the U.S. energy economy such as medium- and heavy-duty transportation, energy storage, and industrial processes such as steel making. Currently most of the hydrogen produced globally is produced with steam methane reforming and has a carbon intensity associated with partially burning natural gas. An alternative way of producing hydrogen is using electrolysis and renewable energy to split water into hydrogen and oxygen. Hydrogen produced in this way is called "green" hydrogen. The devices that are used to produce green hydrogen are electrolyzers and the most prominent type of electrolyzer today is the proton exchange membrane (PEM) electrolyzer. Most PEM systems are designed for continuous operation with a constant input of electricity. When PEM electrolyzers are coupled with renewable energy such as wind turbines and solar photovoltaics, the input electricity to the electrolyzer may follow the same variable and intermittent profile as renewable energy generation. System modeling while including balance of plant components can be used to optimize the green hydrogen generation system for the highest energy conversion efficiency across the range of possible operating conditions with renewable energy input. This work is focused on creating a system model of a PEM green hydrogen generation system including the balance of plant components such as power electronics, electrolyzer stack, hydrogen purification, hydrogen compression/storage, and system cooling. Literature primarily focuses on modeling the electrolyzer stack and ignores the balance of plant components. Some recent publications create system models with the balance of plant included but are unnecessarily complex. The model created in this work includes the balance of plant and reduces the complexity of recently published balance of plant models while maintaining the model's functionality in system optimization studies. Limited experimental data available in literature is used to verify and validate the model. The model is scaled to represent a utility scale system which would include multiple electrolyzer stacks and power electronics. A case study of wind and solar generation in Texas is used to demonstrate the model's capability in optimization studies. The model results show the effects of varying operating conditions such as electrolyzer cathode pressure and electrolyzer current density on the overall system efficiency for a single 120-kW electrolyzer green hydrogen generation system. At low electrolyzer power, the system energy conversion efficiency drops off significantly which is mainly driven by the increase in specific hydrogen loss in the balance of plant. Increasing the electrolyzer cathode pressure decreases the system efficiency and operating range but may provide benefit by allowing the hydrogen compressor to be removed from the system. Two different electrolyzer "loading" strategies were imposed on the multi-electrolyzer stack model with the Texas case study and show that there is a slight benefit in efficiency if the strategy maximizes the electrolyzer power and minimizes the amount of electricity that is wasted within the system. Other tradeoffs such as average electrolyzer power and the number of electrolyzer shutdowns are evaluated between the two loading strategies. If a minimum electrolyzer power is selected at 50% of the rated power, the parallel loading scheme produces 9,000 kg more hydrogen than the series loading scheme with the same input power profile. The model developed in this work is a valuable tool to optimize the production of green hydrogen by identifying and optimizing the interactions of different components within the system to maximize the energy conversion efficiency. Optimizing the green hydrogen generation system will improve the economic feasibility and accelerate the adoption of green hydrogen at a large scale.Item Open Access Reciprocating compressor lubrication – lubricant dilution with natural gas species and the impact on lubrication rates at various operating conditions(Colorado State University. Libraries, 2021) Schulthess, Jesse Jamison, author; Windom, Bret, advisor; Olsen, Dan, committee member; Watson, Ted, committee memberReciprocating compressors are ubiquitous in the natural gas industry as they provide much of the pressure necessary to move natural gas from the wellhead to the customer. Many of these compressors use lubricants to reduce friction and wear at the piston-cylinder interface. These lubricants have a difficult job for many reasons, but one phenomenon is often overlooked: gas solubility. Natural gas is soluble in the lubricant at high pressures and mixes with, or dilutes, the lubricant. Recent research has demonstrated that this dilution may reduce a lubricant's viscosity so far that the lubricant cannot adequately protect the compressor. However, questions remain. First, how quickly do a gas and lubricant mix? Second, are results from previous studies applicable to the field? Third, how much lubricant is required for proper compressor lubrication? To address the first question, an experiment was devised to measure the dilution of a lubricant while it mixed with natural gas. This "dilution rate" was measured for multiple lubricants subjected to a range of temperatures and pressures. These experiments indicated that lubricants quickly obtain equilibrium with the gas stream which implies that the equilibrium viscosity of the gas-lubricant mixture is an accurate estimate of the lubricant's viscosity inside an operating compressor. To answer the second question, samples of used lubricant were collected from the field at various operating conditions. These samples were subsequently depressurized in an enclosed chamber allowing for an analysis of the gas dissolved in the lubricant. Results showed that the lubricant absorbed higher proportions of heavier hydrocarbons (C2+) than methane even when the natural gas stream was mostly methane. To answer the third question, a model of the piston-cylinder interface was created to estimate the lubricant film thickness in a reciprocating compressor. Many prior researchers have measured or estimated the lubricant film thickness for internal combustion engines but the piston ring geometry in a reciprocating compressor is drastically different. Suggestions for lubricants and lubrication rates are made using this model and compared with current industry experience.Item Open Access Synthesis, properties, and suitability of various oxymethylene ethers for compression ignition fuels(Colorado State University. Libraries, 2023) Lucas, Stephen P., author; Windom, Bret, advisor; Foust, Thomas, committee member; Reardon, Kenneth, committee member; Marchese, Anthony J., committee memberCompression ignition (CI) engines are currently the most common prime mover for medium and heavy duty vehicles; these engines contribute roughly a quarter of US greenhouse gas emissions from transportation, and even higher percentages of particulate and nitrogen oxide emissions. As a result, there have been significant efforts made to reduce these emissions, particularly through selection of low-emissions alternative fuels. Oxymethylene ethers (OMEs) are a class of molecule, typically structured R-O-(CH2O)n-R', which have been considered as a possible blendstock in CI fuels for the goal of soot reduction. Generally, past work has focused on methyl-terminated OMEs, CH3-O-(CH2O)n-CH3, which by virtue of containing no C--C bonds, produce negligible soot. These molecules show significant reductions in soot emission from engines when blended in moderate to high ratios with traditional diesels, however, they have been shown to have inferior physical properties and poor compatibility with some legacy systems. Recent theoretical work has shown that OMEs with non-methyl alkyl groups may have superior performance, albeit at the cost of increased soot formation. In this work, a variety of OMEs with terminating alkyl groups from methyl to butyl are considered for their suitability as CI fuels. The synthesis of these extended OMEs is studied, including formation of n=1 OMEs from common chemical sources, and extension of the chain length to heavier molecules, via reactions over acidic ion exchange resins. Following the synthesis, the properties of these OMEs are studied with respect to their engine applicability. It is found that heavier (propyl- and butyl-terminated) OMEs have superior properties for diesel compatibility, particularly in reactivity, volatility, and water solubility. Extended-alkyl OMEs are found to have higher soot production than methyl-terminated OMEs, but remain superior to diesel soot production on a per-unit-energy basis. A sample of a butyl-terminated OME mixture, n=2-4, is selected as the ideal OME blend for close compatibility with legacy diesel systems. This mixture is blended with certified diesel and tested for ASTM D975 compatibility, passing all required tests but lubricity; decreased heat of combustion is observed but not governed by the diesel standard. Fundamental combustion tests of various mid-weight OMEs are performed in a rapid compression machine, where it is shown that low-temperature chemistry causes a region of decreased dependence of ignition delay on temperature, consistent with methyl-terminated OME behavior. An isopropyl-terminated OME is observed to have low reactivity compared to other OMEs; this fuel is investigated via further rapid compression machine testing and CFR engine testing. It is found that this OME has strong negative-temperature-coefficient ignition behavior - a first for OMEs - and has reactivity lower than other OMEs, but insufficient for direct spark ignition engine testing.Item Open Access The development and implementation of a hybrid rocket motor thrust stand to investigate the relationship between combustion chamber pressure and graphite rocket nozzle erosion in hybrid rocket motors(Colorado State University. Libraries, 2022) Kronwall, Matthew, author; Windom, Bret, advisor; Marchese, Anthony, committee member; Kim, Seonah, committee memberRocket motors frequently implement carbon-based nozzle inserts to insulate the motor from the heat produced by combustion. Over time these inserts will erode due to oxidation at the surface wherein oxidizing species found in the combustion products react with the carbon to form carbon monoxide. It has been shown that the largest contributors/oxidants to erosion are H2O, CO2, and OH, due to their high concentrations within the exhaust products and the low activation energy needed to react with the carbon surface. As such, a clear understanding of the rate of oxidation, or erosion, is critical to rocket motor design. Previous research has modeled many of these characteristics, yet this has largely been limited to solid rocket motors with combustion chamber pressures greater than 6.9 MPa. Earlier studies have asserted that combustion chamber pressure has a linear effect on erosion rates, but it is unclear whether this linear assumption can be extrapolated to lower chamber pressures. This research lays the foundational work to explore the relationship between combustion chamber pressure and erosion rates at pressures below 6.89 MPa. Based on the numerical modeling and rocket motor test firings described in this study, preliminary findings indicate that this linear assumption may not hold at combustion chamber pressures below 3.4 MPa. Initial numerical modeling shows a non-linear increase in boundary layer thicknesses as combustion chamber pressures fall below 3.4 MPa. It is postulated that thicker boundary layer slows the diffusion of the oxidizing species to the surface thereby decreasing the rate of erosion. Thus, the modeled results suggest a non-linear relationship between nozzle erosion and pressure may be present at lower chamber pressures. Moreover, pure hydrocarbon fuels generate high fractions of key oxidizing species (H2O, CO2, and OH) in the product stream and the impact of these fuels on carbon nozzle erosion has remained largely unexplored. A hybrid rocket motor test stand (HRMTS) was developed to perform test fires of a HTPB-N2O hybrid motor at chamber pressures between 2.07 MPa and 4.83 MPa. Supplementary research was carried out that explored hybrid motor injectors and their effects of combustion instabilities. Major milestones included, implementation of a new semi-autonomous LabVIEW VI, creation of a MATLAB model that predicts motor performance, design and manufacture of a modular hybrid rocket motor, and the development of a secondary model that uses gathered test data to predict transient throat diameters. Furthermore, the predicted nozzle erosion was validated with the measured nozzle surface geometry pre and post-test fire through the utilization of a coordinate measuring machine (CMM). Initial results show that, despite the non-linear boundary layer growth, a linear relationship between combustion chamber pressure and nozzle erosion may still be true for chamber pressures below 6.89 MPa. Testing also illuminated correlations between combustion stability with injector pressure and nitrous oxide phase, for which, poor oxidizer vaporization and injector pressure dramatically decrease combustion stability and motor performance.Item Open Access The role of physical and chemical properties of single and multicomponent liquid fuels on spray processes, flame stability, and emissions(Colorado State University. Libraries, 2019) Alsulami, Radi Abdulmonem, author; Windom, Bret, advisor; Marchese, Anthony, committee member; Olsen, Daniel, committee member; Venayagamoorthy, Karan, committee memberEnsuring reliable and clean combustion performance of IC engines, such as liquid-fueled gas turbines, is associated to our understanding of the impact of fuel composition and properties, as well as the processes that the liquid fuel experiences, e.g., atomization, vaporization, turbulent mixing, and chemical kinetics, on the combustion efficiency, stability, and emissions. This understanding is a key prerequisite to the development of fuel surrogates and the deployment of alternative jet fuels. Most of the surrogate formulation activities, especially with regard to aviation fuels, have targeted only the gas-phase behavior of the real fuels, often neglecting properties responsible for atomization, vaporization, and fuel/air mixing (i.e., physical properties). In addition, much research has been done to understand the flame stability (e.g., lean blowout limit and flame liftoff height) of gaseous and pre-vaporized fuels. Thus, the optimization of the fuels and the liquid fueled combustion devices, e.g., gas turbines, requires the consideration of the two-phase process and the coupling between the complex physical and chemical processes. This will improve the understanding of the mechanisms that controls flame lean blowout limit and liftoff height of liquid fuels. Therefore, an appropriate surrogates will be formulated and a faster processes to certify the alternative fuels will be achieved. In this work, the flame stability in spray burner, quantified by flame lean blowout liftoff height, for different single, binary, alternative, and conventional fuels were experimentally measured. The flame behavior from the spray burner was compared to the results which was done using gaseous flame platform, e.g., counterflow flame burner, to clearly demonstrate the significant importance of two-phase spray processes (i.e., atomization, vaporization, and turbulent mixing) on flame stability. It was found that the atomization process, which can lead to the variation of the droplet size and distribution, has significant impact on flame stability. This is because any change in the droplet size can enhance/diminish the vaporization and mixing processes, and therefore influence the clean and efficient energy conversion process. In addition, the sensitivity of the fuels properties on flame stability was evaluated to provide an explanation for why certain fuel properties govern flame stability, such as lean blowout and liftoff height. Thus, flame stability mechanisms can be developed. A number of approaches were used in this work to address these issues, such as multiple linear regression analysis, and previously developed correlations. The results indicate the importance of the atomization process (i.e. droplet size) on the vaporization rate and suggest that the liquid fuel fraction entering the flame plays a dominant role in controlling lean blowout limits. Thus, the large droplet and less volatile fuel was the most resistance fuel to flame blowout. The differences in liftoff height was shown to be a result of two-phase flame speed, which accounts for both pre-vaporized fuel reactivity defined by laminar flame speed (SL) and time scales associated with droplet evaporation. The influence of the physical and chemical properties of different jet fuels on spray process and thus on emissions is also investigated. This is done by measuring soot formation using Laser-Induced Incandescence (LII). The trends in spray flame soot formation are compared to the gas-phase Yield Sooting Index (YSI). Results indicate differences in planar soot distributions amongst the fuels and suggest a significant influence of the atomization and the vaporization processes on mixing and the soot formation.