Browsing by Subject "Diesel"
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Item Constraints on algal biofuel production(2011-05) Beal, Colin McCartney; Ruoff, Rodney S.; Webber, Michael E., 1971-; Hebner, R. E. (Robert E.); Berberoglu, Halil; Seibert, A F.; King, Carey W.The aspiration for producing algal biofuel is motivated by the desire to replace conventional petroleum fuels, produce fuels domestically, and reduce greenhouse gas emissions. Although, in theory, algae have the potential to produce a large amount of petroleum fuel substitutes and capture carbon emissions, in practice, profitable algal biofuel production has proven quite challenging. This dissertation characterizes the production pathways for producing petroleum fuel substitutes from algae and evaluates constraints on algal biofuel production. Chapter 8 provides a summary of the entire dissertation. The first chapter provides a framework for reporting the production of renewable diesel from algae in a consistent way by using data that are specific and by presenting information with relevant metrics. The second chapter presents a review of analytical tools (i.e., microscopy, spectroscopy, and chromatography) that can be used to analyze the structure and composition of intermediate products in an algal biofuel production pathway. In chapters 3 through 6, the energy return on investment, water intensity, and financial return on investment are presented for three cases: 1) an Experimental Case in which data were measured during five batches of algal biocrude production with a combined processed volume of about 7600 L, 2) a hypothetical Reduced Case that assumes the same energy output as the Experimental Case, with reduced energy and material inputs, and 3) a Highly Productive Case that assumes higher energy outputs than the Experimental Case, with reduced energy and material inputs, similar to the Reduced Case. For all three cases, the second-order energy return on investment was determined to be significantly less than 1, which means that all three cases are energy negative. The water intensity (consumption and withdrawal) for all cases was determined to be much greater than that of conventional petroleum fuels and biofuels produced from non-irrigated crops. The financial return on investment was also found to be significantly less than 1 for all cases, indicating production would be unprofitable. Additionally, it was determined that large-scale algal biofuel production would be constrained by the availability of critical energy and material inputs (e.g., nitrogen and carbon dioxide). The final part of this dissertation presents a first-principles thermodynamic analysis that represents an initial attempt at characterizing the thermodynamic limits for algal biofuel production. In that analysis, the energy, entropy, and exergy is calculated for each intermediate product in the algal biofuel production pathway considered here. Based on the results presented in this body of work, game-changing technology and biotechnology developments are needed for sustainable and profitable algal biofuel production.Item Fuel economy predictions for heavy‐duty vehicles and quasi‐dimensional DI diesel engine numerical modeling(2016-05) Ates, Murat, 1982-; Matthews, Ronald D.; Hall, Matthew John; Ellzey, Janet L.; Ezekoye, Ofodike A.; Biros, George; Roberts, Charles E.A research team developed the University of Texas Fuel Economy Model to estimate the fuel consumption of both light-duty and heavy-duty vehicles operated on Texas roads. One of the objectives of the model was to be as flexible as possible in order to be capable of simulating a variety of vehicles, payloads, and traffic conditions. For heavy-duty vehicles, there are no prescribed driving cycles, there are no coastdown coefficients available from the EPA, and we relied on experimental brake specific fuel consumption maps for a few heavy-duty diesel engines. Heavy-duty vehicle drive cycles highly depend upon the vehicle load, the grade of the road, the engine size, and the traffic conditions. In order to capture real driving conditions 54 drive cycles with three different Class 8 trucks, three weight configurations, three traffic congestion levels, and two drivers are collected. Drive cycles obtained in this research include road grade and vehicle speed data with time. Due to the lack of data from EPA for calculating the road load force for heavy-duty vehicles, coastdown tests were performed. To generate generic fuel maps for the fuel economy model, a direct injection quasi-dimensional diesel engine model was developed based on in-cylinder images available in the literature. Sandia National Laboratory researchers obtained various images describing diesel spray evolution, spray mixing, premixed combustion, mixing controlled combustion, soot formation, and NOx formation via imaging technologies. Dec combined all of the available images to develop a conceptual diesel combustion model to describe diesel combustion from the start of injection up to the quasi-steady form of the jet. The end of injection behavior was left undescribed in this conceptual model because no clear image was available due to the chaotic behavior of diesel combustion. A conceptual end-of-injection diesel combustion behavior model was proposed to capture diesel combustion in its life span. A full-cycle quasi-dimensional direct injection diesel engine model was developed that represents the physical models, utilizing the conceptual model developed from imaging experiments and available experiment-based spray models, of the in-cylinder processes. The compression, expansion, and gas exchange stages are modeled via zero-dimensional single zone calculations. A full cycle simulation is necessary in order to capture the initial conditions of the closed section of the cycle and predict the brake specific fuel consumption accurately.Item Increasing exhaust temperature of an idling light-duty diesel engine through post-injection and intake throttling(2017-12) Ozel, Cafer Tayyar; Hall, M. J. (Matthew John); Matthews, Ronald DModern Diesel engines rely heavily on aftertreatment systems for reducing tail pipe emissions. However, for operating conditions such as cold start, extended low load operations and idling aftertreatment systems cannot maintain a high enough temperature of approximately 200° C to maintain catalyst activity. In crowded urban areas actual driving conditions may significantly differ from FTP cycles due to operating under idle conditions for an extended period of time in congested traffic, long drive thru lines, traffic lights and so on. This study aimed to increase the exhaust temperature of a fully warmed-up idling light-duty Diesel engine by utilizing two methods: intake throttling and post-injection. Also, effects of these two techniques on HC and NOx emissions as well as IMEP and COV of IMEP were investigated. With start of injection (SOI) of post-injection being the primary variable, engine operating parameters were idle speed of 850, 1100 and 1200 rpm as well as injection pressure of 500 and 800 bar. The exhaust temperature was measured to be 105° C for an idle speed of 850 rpm and WOT with no post injection. I was able to increase the exhaust temperature by nearly 65° C with the first method. A further increase by 25° C vi with combined use of the two methods was possible and that yielded exhaust temperatures of around 200° C while HC and NO[subscript emissions roughly doubled. For higher engine speeds and for the heaviest throttling case exhaust temperature increased up to 240° C however, the engine-out HC emission penalty associated with this was nearly 300%. For all degrees of intake throttling, maximum exhaust temperature and minimum NO[subscript x]emissions were achieved for a SOI of post-injection at 25-30° CA aTDC and beyond this range the temperature showed a downward trend while HC emissions increased significantly.Item Model comparison of prototype diesel rotating liner engine and baseline diesel engine(2016-12) Schwartz, Jairus Daniel; Matthews, Ronald D.; Hall, Matthew JFrictional losses in combustion engines have been the subject of many automotive engineers’ research. Understanding the fundamentals behind each frictional loss helps pave the way to finding a solution in reducing the overall frictional power losses and increasing efficiency. The reciprocating piston assembly has been proven to account for over 60% of all frictional power losses within a combustion engine. A major factor contributing to this is when the piston motion is temporarily static at top dead center (TDC) and bottom dead center (BDC). This causes the frictional forces between the cylinder wall and the piston rings to dramatically increase during these time periods. A solution to this would be to rotate the cylinder wall in order to keep the frictional forces in the hydrodynamic regime throughout the entire cycle of the combustion engine process. The prototype diesel rotating liner engine (RLE) is designed to prove this concept. The prototype diesel RLE is a Cummins 4BT engine that has been converted to a single cylinder engine and uses a crank pulley and gear system to rotate the cylinder wall. The purpose of this report is to provide information about the history of this research, a piston assembly friction model comparison between baseline engine and RLE, and a commercial application analysis. The results provide evidence of improved motoring operations and that a successfully operating prototype would be highly valued in the heavy-duty diesel industry.Item Performance improvements of turbocharged engines with the use of a PTP turbo blanket(2016-08) Bickle, Steffen Hans; Matthews, Ronald D.; Hall, Matthew J.Efforts in R&D of modern vehicles are highly focused on improvements of the overall efficiency. The engine still has potential for better performance which not only implies pure efficiency considerations but also the power output specific to the engine size and weight. Turbochargers are a key technology. However, a significant amount of exhaust energy is lost through the turbine housing, and thus cannot be utilized to boost the intake air. If a certain portion of the lost heat can be conserved, however, the process in the turbine can be shifted more towards adiabatic expansion which, in theory, is the ideal case. The Engines Research Program at The University of Texas at Austin conducted comparison tests of a PTP turbo blanket. The baseline engine was a Cummins 6.7 Turbocharged Diesel Engine hooked up to a Superflow SF-901 dynamometer. A series of steady-state points were obtained as well as three instantaneous load tip-in scenarios (hard acceleration transients) in order to test for changes in transient response due to the turbo blanket. In addition to seven thermocouples that we installed around the turbine we used the open ECU software to log a set of about 30 engine parameters. The recorded data was first analysed with respect to the performance of the turbocharger alone. On the steady-state cases, the temperature increase of the turbine housing was significant while we did not measure a major increase of the oil temperature in the exit of the center section. According to these findings, oil “coking” was not a concern since the temperature difference of the oil with and without the turbo blanket was negligibly small. The boost pressure increase corresponded well with the higher turbo shaft speeds when the turbo blanket was applied. Second, tip-in transients were performed to examine the difference in performance during a hard acceleration. The turbo spooled up more rapidly with the turbo blanket installed in comparison to the baseline configuration. In all cases this resulted in an improved boost performance in the intake and a significant time-to-torque advantage of the engine with a torque benefit of up to 140 Nm while the acceleration was improved by 200-250 rpm for most of the tip-in event. This report presents detailed data regarding experiments in which the turbocharger and the engine are treated as an integrated system with a PTP turbo blanket applied in comparison to the baseline configuration for which the turbine housing is not insulated.