http://digital.library.wisc.edu/1793/294 http://digital.library.wisc.edu/1793/38073 GENIUS v2: An Extensible Platform for Modeling Advanced Global Fuel Cycles Dunn, Kerry Ahn, Tae Wook Elmore, Royal Huff, Kathryn Oliver, Kyle Wilson, Paul P.H. GENIUS v2 is a modular extensible platform for the study of advanced nuclear fuel cycles. A great deal of flexibility is available within the high-level modeling approach described here. Fundamental to GENIUS v2 is the modeling of every individual fuel cycle and reactor facility in the nuclear fuel cycle. Each facility is assumed to operate as a black box converting discrete batches of one material, with a given isotopic composition, into discrete batches of new material, with new isotopic compositions. The modular nature of this implementation allows new developers and users to implement any numerical model for achieving this conversion. GENIUS v2 employs an approach in which every facility is owned by an institution, and each institution operates in a specific region. Institutions are intended to represent a generic operating entity, whether a private corporation, a government, an international agency, etc. Regions are intended to represent any type of geo-politically defined part of the globe, real or representative, including sub-national, national, or super-national regions. This ownership hierarchy affords two important capabilities: (a) performance characteristics of facilities can be determined in part by the institution or region in which they operate (b) relationships between/among institutions and regions can be modeled in other parts of the problem. At each time step, a set of requests for material and offers to provide material are collected and arranged into a network flow problem. The sources and sinks for this problem are the facilities that produce/consume the commodity in question. A different network flow problem is created for each commodity in the problem. The behavior of the system is affected by changing the arc costs of the network flow problem. By adopting a modular approach for the definition of the arc costs, users/developers are free to introduce their own behaviors. The default behavior defines default affinities for trade between different institutions and different regions to determine these costs. The user can override these affinities to model different technical/economic/political arrangements. (Affinities are a coarse grained quantity intended to model a qualitative behavior.) A common problem in fuel cycle modeling tools that include advanced fuel cycles is the ability to match the available separated materials with desired fuel recipes. With a discrete material approach, a number of batches of separated material are available at any point in time, each with a specific isotopic composition. We formulate this as a small optimization problem in which we minimize the relative difference between the achieved recipe and the target receipe on an isotope-by-isotope basis while constraining the difference between the achieved and target recipes based on some metric of neutronics performance. Under this paradigm, users/developers are free to modify the objective function and/or constraints to improve the quality of the approximation. The output of GENIUSv2 is a database documenting every transaction of material including: the facility from which the material originated, the facility to which the material was sent, the simulation time step at which the transaction took place, and a reference to the composition of the material at that time. Post-processing tools are provided for extracting and visualizing this data in a variety of ways. Tue, 03 Nov 2009 22:58:59 GMT http://digital.library.wisc.edu/1793/35333 FUEL FILM DIAGNOSTIC DEVELOPMENT OF A SPARK IGNITED, HOMOGENEOUS CHARGED, FOUR STROKE, AIR-COOLED ENGINE Jehlik, Forrest Auchmuty The main objective of this research has been to develop techniques for qualifying and quantifying fuel film development in the intake port of a small air-cooled four-stroke utility engine. These techniques should be able to quantify the total mass of fuel film in the intake port under various operating conditions. Such techniques would determine operating conditions that lead to the formation of fuel films, yielding information into fuel film behavior and possible means of reducing such effects. To achieve the above-mentioned objectives, five methods were used to assess fuel films under various operating conditions. The five methods used to assess fuel films were 1. Indolene- and propane-fueled impulsive fueling transients using a heated universal exhaust gas oxygen (UEGO) sensor as a diagnostic. 2. Indolene- and propane-fueled impulsive throttle transients using a UEGO sensor as a diagnostic. 3. Capacitance fuel film measurements. 4. Skip-injection with fast flame ionization detector (FFID) exhaust hydrocarbon sampling. 5. Stop-injection with FFID exhaust hydrocarbon sampling. The thesis is presented as follows. Chapter 2 consists of a literature review of various other research work conducted on fuel film behavior. In Chapter 3, the laboratory setup and equipment used for this experiment is presented such that the experiment could be independently repeated. Chapter 4 consists of characterizing the response time of the UEGO sensor that is used for both the impulsive fuel and impulsive throttle transient tests listed as 1 and 2 above. Statistical tests are also presented that verify the validity of the tests. In Chapter 5, the techniques and results of the indolene- fueled impulsive transients are presented. In Chapter 6, the techniques and results to indolene and propane impulsive throttle transients are presented. In Chapter 7, a localized capacitance technique of measuring film thickness is presented. Two methods of calibrating the sensors are presented, as well as the results of using such gages on a motored engine. In Chapter 8, results of skip-injection and stop-injection tests with FFID exhaust sampling techniques and are presented. The thesis concludes with Chapter 9, which summarizes the work and recommendations for future research on fuel film behavior involving small air-cooled utility engines. Wed, 08 Jul 2009 19:17:03 GMT http://digital.library.wisc.edu/1793/35331 Fuel Effects on Homogeneous Charge Compression Ignition Combustion Zuehl, Jacob Richard Homogeneous charge compression ignition (HCCI) is one combustion strategy that has shown the possibility of both lower emissions and lower fuel consumption than spark ignition combustion. However, HCCI combustion can be sensitive to changes in fuel composition. The effects of fuel composition on HCCI combustion were experimentally investigated in a single cylinder 4-stroke SI engine adapted to run HCCI combustion with the Negative Valve Overlap (NVO) valve timing strategy. This strategy traps large amounts of hot residual gases in the cylinder to raise the mixture temperature and promote auto-ignition. Direct fuel injection was used, with one injection occurring during the NVO period to increase the residual temperature and for fuel reforming, and the other injection occurring just after intake valve opening. The timing and duration of the NVO injection were used to control the combustion phasing; an advance in timing or increase in delivered fuel mass caused an advance in combustion. The testing was performed at three operating conditions: 2100RPM 3bar IMEP, 2100RPM 2bar IMEP, and 3500RPM 2bar IMEP. Three gasoline-like fuels and an 87 octane pump gasoline were tested to examine the effects on fuel consumption and HC, CO, and NOx emissions. The trends for the fuels were consistent over all conditions and correlated well with combustion phasing. Most differences were small with a few exceptions. One of the test fuels, which was the only oxygenated fuel tested, showed significantly higher fuel consumption, which was mainly due to its lower energy density. This fuel also had lower HC emissions than the other test fuels; however, this may have been caused by the HC analyzer?s lower response to oxygenated hydrocarbons. The pump iv gasoline had significantly higher NOx emissions, but the reason for this difference is less clear and may have been caused by chemical effects. The combustion phasing of the four fuels was also compared. Heptane and Iso-Octane were also tested as they provided limits of low and high octane rating respectively. The phasing of the three test fuels, which ranged in RON from 66 to 88 and MON from 69 to 98, were all advanced compared to the pump gasoline by 2� at 2100RPM and 1� at 3500RPM. The phasing of Heptane was advanced by 6� at 2100RPM and 3� at 3500RPM, while the Iso-Octane was retarded 6� at 2100RPM and 3� at 3500RPM. Correlations of RON and MON with the change in phasing were poor, but Octane Index correlations were good. Wed, 08 Jul 2009 19:11:10 GMT http://digital.library.wisc.edu/1793/35329 UNBURNED HYDROCARBON EMISSION MECHANISMS IN SMALL ENGINES Salazar, Victor M. The effect of the liquid fuel in the intake manifold, the ring pack crevices and the oil film on the unburned hydrocarbon (HC) emissions of a spark-ignited, carbureted, air-cooled V-twin engine was studied. Tests were performed for a range of engine load, two engine speeds, various air-fuel ratio and with a fixed ignition timing. To isolate liquid fuel effects due to the poor atomization and vaporization of the fuel when using a carburetor, a specially conditioned homogeneous, pre-vaporized mixture system (HMS) was developed. The results from carburetor and HMS are compared. To verify the existence of liquid fuel in the manifold, and to obtain an estimate of its mass, a carburetor-mounted liquid fuel injection (CMLFI) system was also implemented. Stop-injection tests performed with the CMFLI system show that 60-80 cycles worth of liquid fuel is held in the intake manifold depending on operating condition. The results of the comparison show that the liquid fuel in the intake manifold does not have a statistically significant influence on the averaged HC emissions. In addition, the cycle-resolved HC emissions for both systems follow the same trends and are comparable in magnitude. Heat release analysis showed little difference between fuel mixture delivery system. These results suggest that under steady state operation the HC emissions for this engine are not sensitive to the presence of liquid fuel in the intake manifold. The ring pack contribution to the engine-out HC emissions was estimated using a simplified ring pack gas flow model; the model was tested against the experimentally measured blowby. The tests were performed using the homogeneous fuel mixture system. The integrated mass of HC leaving the crevices from the end of combustion (the crank angle that the cumulative burn fraction reached 90%) to exhaust valve closing was taken to represent the potential contribution of the ring pack to the overall HC emissions; post-oxidation in the cylinder will consume some of this mass. Time-resolved exhaust HC concentration measurements were also performed, and the instantaneous HC mass flow rate was determined using the measured exhaust and cylinder pressure. At high load the model predicts that the ring pack returns approximately three times as much HC mass to the cylinder as is measured in the exhaust, indicating that the HC emissions are dominated by the ring pack contribution. At the lightest load condition tested, the ring pack model predicts less mass returning to the cylinder from the ring pack than is observed in the exhaust, clearly indicating that another HC mechanism is significantly contributing to the exhaust HC emissions. The integrated exhaust HC mass from the time-resolved HC measurement was found to correlate inversely with the IMEP on a cycle-by-cycle basis, which strongly suggest that incomplete combustion is materially contributing to the exhaust HC emissions. A statistical analysis showed that the correlation was significant. The intermediate load condition represents a combination of these two extremes. The ensemble-average ring pack model results indicate that the mass returned to the cylinder from the ring pack is slightly higher than the amount measured in the exhaust. But, a conditional sampling analysis indicates that there are sub-groups, i.e. late-burning cycles, for which this is not true. There is expected to be some in-cylinder post-oxidation of the ring pack HC mass at this condition, and the late burning cycles were not found to excessively contribute to the HC emissions, which both strongly suggests that there are other mechanisms besides the ring pack that are significantly contributing to the HC emissions at this condition. The most likely mechanism is incomplete combustion. The contribution of fuel adsorption in engine oil and its subsequent desorption following combustion to the engine-out hydrocarbon (HC) emissions was studied by comparing steady state and cycle-resolved HC emission measurements from operation with a standard full-blend gasoline, and with propane, which has a low solubility in oil. Experiments were performed at two speeds and three loads, and for different mean crankcase pressures. The crankcase pressure was found to impact the HC emissions, presumably through the ringpack mechanism, which was largely unaltered by the different fuels. The average and cycle-resolved HC emissions were found to be in good agreement, both qualitatively and quantitatively, for the two fuels. Further, the two fuels showed the same response to changes in the crankcase pressure. The experiments were supported by a numerical analysis. The simulation of the liquid-gas phase equilibrium of the fuel-oil system showed the solubility of propane in the oil was approximately an order of magnitude lower than for gasoline. Further the numerical analysis of the adsorption-desorption of the fuel in the oil along the cycle showed that the oil layer contribution is very small compared with the ring pack contribution. This suggests that the effect of fuel adsorption in the oil is not significant for small air-cooled utility-type engines. Wed, 08 Jul 2009 19:09:24 GMT http://digital.library.wisc.edu/1793/35327 OPTICAL INVESTIGATIONS OF THE EFFECTS OF STRATIFICATION ON HOMOGENEOUS CHARGE COMPRESSION IGNITION COMBUSTION Herold, Randy E. The effects that thermal and compositional stratification have on homogeneous charge compression ignition (HCCI) combustion were studied using an optically accessible internal combustion engine. A stratified flowfield was developed in the engine by feeding each intake valve of the four-valve engine with independent intake systems. Planar laser-induced fluorescence (PLIF) of 3-pentanone that was introduced through only one intake valve indicated significant mixing between the two intake streams. A number of different intake-flow modifying devices were used in an attempt to maximize the amount of bulk stratification maintained throughout compression, but only when using top- and inside-directing intake baffles were significant improvements over a simple, straight-runner system observed. The bulk stratification maintained throughout compression, measured as the average deviation of the mean fluorescence profile from the mean homogeneous fluorescence profile, increased by 36% when using the topdirecting baffles and by 30% when using the inside-directing baffles compared to when using the same runner with no baffles. The combination of cylinder pressure, engine-out emissions, and high-speed chemiluminescence measurements were used to evaluate the effects that stratification had on HCCI combustion. The cylinder pressure and emissions data showed little-to-no difference when comparing the combustion under homogeneous operation to combustion under stratified operation at a constant location of peak pressure. Large differences, however, could be observed in the spatial progression of the HCCI combustion. Qualitative observations of the manner in which the combustion proceeded indicated that �60 K temperature stratification, �25% fuel concentration stratification, and �7 air-fuel ratio stratification all similarly affected the combustion progression. A dual-tracer PLIF temperature imaging technique was calibrated in situ and applied under motored and fired engine operation. Initial experiments under motored engine operation showed that the dual-tracer PLIF technique, with 3-pentanone and triethylamine as the tracers, achieved sufficient temperature precision to measure singleshot temperature variations of �2.3 K (�1?) with an intensified camera or �1.4 K (�1?) with an unintensified camera. Mean temperature profiles acquired with thermally stratified intake conditions showed a 5 K gradient across the combustion chamber. When applied under fired operation, the high in-cylinder temperatures resulted in low fluorescence signals and limited the ability to precisely measure temperature variations resulting from introduced thermal stratifications. Wed, 08 Jul 2009 19:07:27 GMT http://digital.library.wisc.edu/1793/35325 LIGHT-LOAD BURN RATE ANALYSIS IN AN AIR-COOLED UTILITY ENGINE Brossman, John Richard In order to maximize the power-to-weight ratio, small, air-cooled utility engines are designed for WOT performance. Low-speed, light-load conditions suffer due to high residual gas retention, poor volumetric efficiency and an unfavorable in-cylinder flow field that can lead to heat release past EVO. Conditions with significant heat release past EVO have been found to contribute as a dominant HC emissions source at low-speed and lightload. The effects of a dual spark configuration, an alternate spark location, and bulk flow improvement through swirl enhancement were investigated on a single-cylinder, air-cooled utility engine. A steady flow analysis of various swirl enhancement techniques was conducted on a steady flow bench with a swirl adaptor to obtain a global view of the intake flow angular momentum. Through in-cylinder pressure recording and exhaust gas sampling, a single-zone heat release and ring-pack model were utilized to analyze combustion and emissions performance. A similar operating condition was defined and explored to determine the light-load performance of various engine designs to isolate characteristics leading to improved performance. It was found that a dual spark configuration advances combustion leading to a reduction in burn duration, but increased burning rate only occurs when the flame fronts are held independent. With a retarded combustion phasing strategy, HC and NOX emissions were reduced independent of speed and load due to lower ring pack loading and a favorable post-oxidation environment. Conditions with significant heat release past EVO through retarded combustion phasing were found to not increase HC emissions; an oxidation reaction was still in effect. A port blockage that induced a tangential flow was found to significantly improve the part-throttle steady flow swirl coefficient leading to a greater global swirl ratio. Engine combustion tests using this blockage indicated a significant advance of combustion leading to decreased burn duration and reduced COV independent of speed and load. Due to the improved burn rate, lean operating conditions were explored and resulted in a significant reduction in HC emissions, but increased NOX leading to a negligible change in the HC+NOX parameter from the rich condition. A similarity condition was defined based on mean piston speed, IMEP and combustion phasing with engines of various size and geometry. This first order assessment provided similar thermodynamic conditions at CA50, with the intake and combustion chamber geometry produced in-cylinder flow field variations impacting combustion duration. Engines with centralized spark positions and pent-roof combustion chambers were found to improve the CAIgn-10 and CA10-50 duration over the side spark, bathtub configurations. Significant differences of the flame termination period, CA50-90, indicate favorable flow fields late in the cycle and may indicate a dependence on the cooling package associated with the engine. Wed, 08 Jul 2009 19:05:32 GMT http://digital.library.wisc.edu/1793/35323 Numerical and Experimental Fuel Flow Analysis of Small Engine Carburetor Idle Circuits Hendricks, Terry L. Small engine carburetors have been used for over 100 years and their continual development has produced a mechanical device that although simple in principle is difficult to control in practice. This study aims to develop a mathematical model of the air and fuel delivery process that occurs in the idle path that can predict the air-to-fuel ratio in small engines. A one-dimensional model was created that incorporates single phase air and fuel flow effects using an electrical circuit analog. The model incorporates dynamic fuel flow effects due to inertia, and was coupled to the engine airflow via input data provided by commercial engine simulation software. The methodology developed for the idle path creates a foundation on which to build a transition system and the boundary conditions that control it. A simplified model of the main path circuit was also created that incorporates single phase inertial effects and was used to provide boundary conditions to the idle path model. Finally, a dynamic sensitivity analysis of the idle path was conducted to analyze which elements of the idle path control the fuel flow response. The second part of this study addressed the results of the sensitivity analysis. The idle discharge metering orifice has the largest effect on the air-to-fuel ratio delivered to the engine by the idle path. An experiment was created to characterize two-phase orifices representative of the idle discharge metering orifice. The data produces an empirical correlation that can be used to predict the pressure loss across the metering orifice. The correlation displays results that are inconsistent with the homogeneous assumption and highlights the need for further research in this area. Wed, 08 Jul 2009 19:03:06 GMT http://digital.library.wisc.edu/1793/35321 A COMPUTATIONAL STUDY OF FUEL IMPINGEMENT IN THE INTAKE OF A SPARK IGNITION ENGINE Guldan, Jason Ronald A computational study of fuel impingement in a port fuel injection gasoline engine was performed to gain an understanding of the fuel impingement process, and provide insight into high load fuel delivery, where oil dilution by fuel can be a significant problem. The relatively low intake manifold temperatures and large amount of fuel injected make fuel impingement and oil dilution of particular interest in marine outboard engines. This project included the development of a rezoning subroutine, a single-component fuel study and multi-component fuel study using KIVA. Single-component studies of C6H14, C8H18, C14H30 and C8H17 (gasoline) gave an initial indication of the amount and location of fuel impingement. These results indicated a fuel-composition dependence of the fuel impingement process. ASTM D-86 fuel distillation curves were used to create gasoline multicomponent fuel distributions. The results of the multi-component study showed that the mass-averaged mean molecular weight fuel increased during time, suggesting that the heavy components in the fuel would have significant impact on the fuel film. Additional single-component simulations were conducted with a fuel mass representative of the multi-component distribution to examine what effect heavier (C9H20 and C10H22) test fuels would have on the impingement process. The C9H20 and C10H22 simulations showed a higher fraction of the fuel forming a fuel film, 86.9% and 94.4% of total injected fuel, respectively, compared to 38.6% for C8H18 and 33.2% for C8H17. For the tested conditions, there is a clear transition in the impingement process between C8H18 and lighter hydrocarbons and hydrocarbons that are heavier than C8H18. Wed, 08 Jul 2009 19:00:54 GMT http://digital.library.wisc.edu/1793/35319 Non-Intrusive Engine Piston Temperature Measurement Using a Fiber Bragg Grating Pfeifer, Timothy Ross An embedded fiber Bragg grating was used to examine the operating temperature of a small gasoline engine piston. Optical system analyses were conducted to enhance the accuracy and consistency of the measured piston temperature. The goal of the work was to experimentally characterize light transmission through embedded fibers, with the aim of improving the entire measurement system to acquire data as the engine was running. An aspheric collimating lens and a polyimide-buffered fiber Bragg grating were found to create a transmission profile with a much more noticeable Bragg dip, and the optical system was more tolerant to misalignment while maintaining measurement accuracy. A wavelength-agile VCSEL diode laser provided a low-cost means to interrogate the embedded fiber Bragg grating at speeds up to 100 kHz, albeit for a small wavelength domain. Stationary engine measurements successfully determined the piston temperature to be 31.5 �C. However, irreparable damage was caused to the engine when a small piece of electroplated nickel became loose and wedged between the piston and cylinder wall shortly after initiating motored tests. After verifying the integrity of the embedded FBG, the cylinder was rebored and the piston reinstalled. A modified motoring experiment proved that light coupling was occurring for each engine rotation, and analysis determined the piston temperature to be approximately 56 �C. Due to substantial noise in the photodetector data, it was difficult to qualitatively identify the Bragg wavelength without making assumptions about the expected Bragg dip location. Wed, 08 Jul 2009 18:58:30 GMT http://digital.library.wisc.edu/1793/35317 THE EFFECTS OF EXHAUST GAS RECIRCULATION ON COMBUSTION AND EMISSIONS IN AN AIR-COOLED UTILITY ENGINE Haugle, Nathan Jon Among other requirements, small air-cooled utility engines must maximize power-toweight ratio. A means of meeting this requirement is to optimize the gas exchange process by utilizing cam shafts that complement high speed, wide open throttle (WOT) performance. The resulting valve timing tends to cause high levels of exhaust gas retention, or residual, at low-speed, light-load conditions, giving rise to poor combustion stability and idle quality. The effects of residual gas level and homogeneity were studied in a single-cylinder, air-cooled utility engine using both external exhaust gas recirculation (EGR) and internal residual retention. EGR was introduced far upstream of the throttle to ensure proper mixing. Internal residual was changed by varying the length of the valve overlap period. The total in-cylinder diluent was measured directly using a skip-fire cylinder dumping technique. A sweep of diluent fraction was performed for several engine speeds, engine loads, fuel mixture preparation systems, and ignition timings. An optimum level of diluent, where the combined hydrocarbon (HC) and oxides of nitrogen (NOx) emissions were minimal, was found to exist for each operating condition. Higher levels of diluent, either through internal retention or external recirculation, caused the combined emissions to increase. The transition to higher emissions levels was found to correspond to conditions where the heat release rate extends to the point of exhaust valve opening. Combustion with a high level of variability, but heat release completing prior to exhaust valve opening, did not adversely affect the hydrocarbon emissions. This was observed by direct analysis of individual-cycle hydrocarbon emissions and combustion performance. Complementary studies investigated how fuel mixture preparation, residual mixedness, intake volume, ignition timing, spark energy and volume affect combustion quality and emissions. Optimizing the spark timing improved the combustion quality in highly diluted conditions by improving phasing, reducing cyclic variability, and decreasing the burn duration. Similar behavior to stock ignition conditions with regards to hydrocarbon emissions was found; however, improvements in diluent tolerance and combustion quality did not result in reduced emissions. Residual gas mixing, or the source of diluent, appeared to have little effect on the trends seen in combustion or emissions. The trends were found to be only a function of overall diluent fraction. Optimizing the ignition at high levels of diluent appeared to improve combustion quality more easily in the EGR supplemented cases compared to the maximum overlap cases. Very slight improvements in cyclic variability, combustion phasing, and heat release rate were noted with increased spark gap and, to a lesser degree, spark energy. Combustion quality reduced significantly at very low energy and hydrocarbon emissions drastically increased as a result. Wed, 08 Jul 2009 18:55:18 GMT http://digital.library.wisc.edu/1793/35315 Transient High-Pressure Hydrogen Jet Measurements Peterson, Benjamin R. Jets produced by prototype multi-hole gaseous injectors were visualized using schlieren methods. Hydrogen and helium were injected at pressures ranging from 1.3 bar to 104 bar into chamber densities ranging from 1.15 to 12.8 kg/m3, resulting in jets spanning from subsonic to highly underexpanded conditions. The jet tip penetration rate was found to increase with injection pressure, and decrease with increasing chamber density, as expected. The jet angle was also measured, but variability in the results restricted the quantitative assessment of trends. The complex expansion and shock structures within the underexpanded jets were clearly visible, and the distance between the expansion wave fronts was found to scale directly with the ratio of the exit to chamber pressure. Two injector characteristics, the discharge coefficient and rate shape, were measured to describe injector performance. The discharge coefficient was found to range from 0.19 to 0.33, while the rate shape displayed ?top hat? behavior for all conditions tested. Five normalization models that included the effects of expansion outside the nozzle, jet angle variation, and discharge coefficient variation were investigated to analyze their importance in the collapse of the penetration rate data from the three- and seven-hole injectors.. The nondimensional penetration was found to be linearly dependent on the square root of the nondimensional time, indicating self-similar behavior for each investigated normalization scheme. The uncertainty of the slopes of individual runs was quantified and was found to vary for each method, with no clearly superior method. Wed, 08 Jul 2009 18:51:45 GMT http://digital.library.wisc.edu/1793/35313 Analysis of Intake Charge Temperature and EGR Stratification Effects on HCCI Combustion Chialva, Angelo P. HCCI combustion is characterized by a near homogeneous composition and temperature mixture of air, fuel and post-combustion products. HCCI related research work around the world defines different strategies for achieving HCCI combustion based on intake charge characteristics, fuel type, and fuel and residual gas mixing methodologies. Engine specific characteristics that defined our HCCI combustion research can be listed as follows: - Fuel injection was always performed upstream of the intake port to ensure that a fully homogeneous air and fuel mixture charge was delivered into the engine. ? Low levels of in-cylinder residual gas were achieved by a late EVC timing and a minimum of NVO for the purposes of mitigating the in-cylinder temperature, air-fuel ratio and diluent stratification effects imposed by the trapped residual gas. ? Externally added EGR helped achieve HCCI combustion within the desired limits of combustion variability and ringing index, and also allowed running the engine fully unthrottled. ? Cylinder head split port and dual intake surge tanks / dual intake runners made possible it to inject two fully independent charges into the engine. ? Fuel type used to run these experiments was isooctane. This fuel was chosen due to its characteristics as a single stage ignition fuel. A very specific intake port and intake system setup has been designed and installed in a single cylinder engine to analyze and characterize the effects of imposed intake charge temperature and composition stratification on combustion and emission metrics. The characteristics of this particular engine intake port and intake system setup allowed us to establish different sorts of charge stratification, such as thermal and composition stratification. The main objective of this research work was to conduct HCCI combustion and emission studies through the isolation of combined effects imposed by the stratified charge. Thermal and composition intake charge stratification effects could be imposed by applying separately diluent or charge composition and thermal stratification effects throughout the intake charge. The list of combined effects within the stratified charge was detailed as follows: local air-fuel ratio effects, thermal charge gradient effects caused by differences in charge specific heat ratios, diluent stratification and fuel number density non uniform spatial distributions. Experimental results have shown that: - Combustion phasing is sensitive to thermal and diluent stratification effects. ? The combustion event was a unique function of Combustion Phasing CA50. - With thermal charge stratification, combustion advances at a fixed intake charge temperature. - With diluent stratification, combined effects take place to modify ignition timing. - Stratified charge effects such as A/F, Non-uniform Spatial Distribution of Mixture Gamma, Fuel and Diluent are all interconnected. Combustion phasing is strongly sensitive to each one of these individual effects. Wed, 08 Jul 2009 18:43:07 GMT http://digital.library.wisc.edu/1793/35311 OH Absorption Spectroscopy to Investigate Light-Load HCCI Combustion Younger, Sean J. Absorption spectroscopy of the OH molecule was used to examine the light-load limit of the HCCI combustion process. Optical results were compared to cylinder pressure and emissions data, with a focus on the transition from low to high engine-out CO emissions. The goal of the work was to experimentally verify a low-load emissions limit to practical HCCI combustion that has been predicted by detailed kinetic simulations. Two diluent mixtures were used along with 100% air to create intake charges with varying specific heats in order to highlight the temperature dependence of OH formation. Peak OH concentration data show a correlation with temperature, which agrees with theory. In general, OH absorption decreased monotonically with the mass of fuel injected per cycle for all diluent cases. The absorption spectra, which were taken with 400 ?s time resolution (~1.8 CAD at 600 RPM) show that OH forms during the secondstage heat release and remains in the cylinder well into the expansion stroke. Spectral resolution did not allow a temperature measurement from absorption, so temperature was measured separately. Emissions data showed low exhaust CO concentrations at high fuel rates, and higher CO concentrations at low fueling rates. Qualitatively, the detection limit for OH coincided with the onset of increased engine-out CO emissions and the transition from strong to weak second stage heat release. These data suggest that the three phenomena are linked. As increased CO emissions are the practical limitation to the light-load operation of the HCCI engine, this transition is the light-load limit. Due to noise issues in the temperature data, the temperatures at which these transitions happened could not be determined exactly. Wed, 08 Jul 2009 18:39:39 GMT http://digital.library.wisc.edu/1793/35309 Optical Spray Patternation of Gasoline Fuel Injectors Rudnitzki, Ryan M. Planar Mie scattering images were acquired for 21 injectors to investigate the feasibility of a predictive method of injector performance in an engine. A testing apparatus was constructed, which allowed optical access for spray illumination and visualization at pressures up to 650 kPa. The injectors were tested by taking images of a thin cross section of a fuel spray, illuminated with counter-propagating in-plane laser sheets. Data were collected at atmospheric pressure, using capture delay times of 2.5 and 2.7 ms, and at 377 kPa absolute, at 3.1, 3.6, and 4.1 ms. Tests were also run to assess the impact of secondary scattering in the spray images. The results of these tests revealed some signal attenuation and blurring of the images, as well as laser sheet attenuation. Visual analysis of the injector images was only capable of identifying the known good injectors (R1-R6) and the known worst injector (#6). Statistical analysis of spray using the Insight 3G pattern factor tool produced better results. Identification of the good and bad injectors was possible using a capture delay time of 4.1 ms, a vessel pressure of 377 kPa, and a fuel-air delay of 0.952 ms. Similar results were found using the same parameters, but with a capture delay time of 3.6 ms. Of the blind injectors, #2, #8, and #13 were thought to be good, and #4, #10, and #14 were considered. The pattern factor results were sensitive to changes in input parameters. Because of this sensitivity, the ranking of the injectors with APFs near the data set mean could not be determined. Wed, 08 Jul 2009 18:38:06 GMT http://digital.library.wisc.edu/1793/35307 Near-wall PLIF Imaging of Formaldehyde in an HCCI Engine Schrewe, Mark R. This project studied the characteristics of Homogeneous-Charge Compression Ignition (HCCI) combustion near the combustion chamber surfaces using Planar Laser- Induced Fluorescence (PLIF) of the intermediate combustion species formaldehyde. Motivation for this study is a more complete understanding of the thermochemistry associated with HCCI combustion in the thermal boundary layer near the chamber surfaces. Current multi-zone models are based on a mass distribution defined by predictions of the thermal boundary layers. The engine used for this study was a single-cylinder optically accessible research engine, operating with a compression ratio of 9.4:1, at 600 RPM, with equivalence ratios ranging from 0.06 to 0.26 and an intake temperature of 90�C. Formaldehyde fluorescence was excited by 355 nm light from a pulsed Nd:YAG laser using an innovative through-the-wall approach to avoid vignetting effects. Images were acquired with an intensified CCD camera and post-processing was performed to remove background signal interference. This technique allowed spatial resolution both across the field of view and into the combustion chamber with a resolution of 0.5 mm at the wall. The data indicate the absence of a strong global thermal stratification effect near the chamber surfaces, with no preferred location for formaldehyde formation or consumption. In all cases, images show a small thermal boundary layer, counter to model predictions. Trends in formaldehyde concentration as a function of crank timing and equivalence ratio were consistent with the literature. Wed, 08 Jul 2009 18:35:30 GMT