bluuebunny/crossref_metadata_2025 huggingface dataset:
Adolescent girls with emotional disorders have a lower end‐tidal CO2 and increased respiratory rate compared with healthy controls
Authors: Henje Blom Eva , Serlachius Eva , Chesney Margaret A. , Olsson Erik M. G.
Published: February 2014

Hyperventilation has been linked to emotional distress in adults. This study investigates end‐tidal carbon dioxide (ETCO2), respiratory rate (RR), and heart rate variability (HRV) in adolescent girls with emotional disorders and healthy controls. ETCO2, RR, HRV, and ratings of emotional symptom severity were collected in adolescent female psychiatric patients with emotional disorders (n = 63) and healthy controls (n = 62). ETCO2 and RR differed significantly between patients and controls. ETCO2, HR, and HRV were significant independent predictors of group status, that is, clinical or healthy, while RR was not. ETCO2 and RR were significantly related to emotional symptom severity and to HRV in the total group. ETCO2 and RR were not affected by use of selective serotonin reuptake inhibitors. It is concluded that emotional dysregulation is related to hyperventilation in adolescent girls. Respiratory‐based treatments may be relevant to investigate in future research.
A novel HLA‐A allele, HLA‐A*02:441, identified by sequence‐based typing in Chinese individuals
Authors: Li W.‐X. , Xia J.‐A. , Zhang D.‐Y. , Yao L. , Lu H.‐Q. , Shen G. , Bi H. , Ma Y. , Yin J.‐P. , Liu G.‐J. , Zhu Y.‐Y. , Zou J.
Published: February 2014

HLA‐A*02:441 differs from HLA‐A*02:01:01:01 by one nucleotide exchange at position 91(T>C) with an amino acid exchange.
Employing Internet GIS Surveys to Characterize Recreational Boating Travel Patterns
Authors: Cui Yue , Mahoney Edward
Published: February 2014

Spatial factors are fundamental features of the tourism and recreation phenomenon. In terms of recreational boating, scholars are interested both in boaters' spatial distribution and movement patterns and in the factors associated with their movements, e.g. travel costs, environmental impacts, and social impacts of the movements. Spatial factors are also key to policymakers' decisions about where to establish new boating facilities, how protected areas are used by boaters and in crafting policy that minimizes conflict between recreational boating and other waterway uses. However, systematic studies regarding the recreationist movement are scant, especially at the fine geographic level. One reason for the lack of research is that gathering spatial data presents significant practical problems. In the Florida Saltwater Fishing Study, we integrated Google Map APIs into the online survey instrument to collect spatially‐referenced data regarding boaters' movement on water. Results appear to be accurate, highly cost effective, and easily integrated with other survey information such as angler catch, effort, expenditures and attitudes.
Distinct Sets of Rab6 Effectors Contribute to ZW10‐ and COG‐Dependent Golgi Homeostasis
Authors: Majeed Waqar , Liu Shijie , Storrie Brian
Published: February 2014

The organization of the Golgi apparatus is determined in part by the interaction of Rab proteins and their diverse array of effectors. Here, we used multiple approaches to identify and characterize a small subset of effectors that mimicked the effects of Rab6 on Golgi ribbon organization. In a visual‐based, candidate protein screen, we found that the individual depletion of any of three Rab6 effectors, myosin IIA (MyoIIA), Kif20A and Bicaudal D (BicD), was sufficient to suppress Golgi ribbon fragmentation/dispersal coupled to retrograde tether proteins in a manner paralleling Rab6. MyoIIA and Kif20A depletions were pathway selective and suppressed ZW10‐dependent Golgi ribbon fragmentation/dispersal only whereas BicD depletion, like Rab6, suppressed both ZW10‐ and COG‐dependent Golgi ribbon fragmentation. The MyoIIA effects could be produced in short‐term assays by the reversible myosin inhibitor, blebbistatin. At the electron microscope level, the effects of BicD‐depletion mimicked many of those of Rab6‐depletion: longer and more continuous Golgi cisternae and a pronounced accumulation of coated vesicles. Functionally, BicD‐depleted cells were inhibited in transport of newly synthesized VSV‐G protein to the cell surface. In summary, our results indicate small, partially overlapping subsets of Rab6 effectors are differentially important to two tether‐dependent pathways essential to Golgi organization and function.
Increasing susceptibility of nitric oxide–mediated inhibitory platelet signaling during storage of apheresis‐derived platelet concentrates
Authors: Kobsar Anna , Klinker Erdwine , Kuhn Sabine , Koessler Angela , Yilmaz Pinar , Boeck Markus , Koessler Juergen
Published: February 2014

Background

Storage of platelets (PLTs) affects PLT integrity and functionality, a process named the PLT storage lesion. Normal PLT function essentially depends on the balanced interaction of activating and inhibitory signaling pathways. As there are poor data on the alterations of inhibitory signaling during storage of PLT concentrates, this study investigates the modulation capability of the cyclic nucleotide–mediated inhibitory pathways by use of the nitric oxide donor diethylamine diazenium diolate (DEA/NO).

Study Design and Methods

PLTs were obtained from whole blood (WB) and from apheresis‐derived PLT concentrates (APCs) stored for 0, 2, and 5 days. Vasodilator‐stimulated phosphoprotein (VASP) phosphorylation, cyclic nucleotide concentrations, fibrinogen binding, and agonist‐induced aggregation were measured without or after stimulation with DEA/NO.

Results

DEA/NO‐induced VASP phosphorylation was significantly higher in PLTs from APCs on Days 2 and 5 compared to WB, conditioned by a stronger increase of cyclic guanosine monophosphate (cGMP), but not cyclic adenosine monophosphate (cAMP), in stored PLTs. A quantity of 5 nmol/L DEA/NO neither influenced thrombin receptor activator peptide 6 and collagen‐induced aggregation nor fibrinogen binding in freshly collected PLTs, whereas it significantly inhibited both in stored PLTs.

Conclusion

Stored PLTs showed an impairment of intracellular cGMP regulation, resulting in exceeding inhibition of agonist‐induced aggregation and fibrinogen binding in the course of storage. The observed effects could be an important mechanism contributing to the storage lesion with reduced activating potential of PLTs.
Active Control of Pressure Pulsation in a Piping System Using Measured Dynamic Flow Rate
Authors: Pan Min , Johnston D. Nigel , Plummer Andrew , Kudzma Sylwester , Hillis Andrew
Published: February 2014

Fluid-borne noise is caused primarily by unsteady flow from pumps and motors and the instability and cavitation of valves. It takes the form of pressure pulsation or fluctuations in the fluid, and results in structure-borne noise and air-borne noise. An effective method to reduce the noise is needed that does not impair the system performance. In this paper, an active attenuator of pressure pulsation in a conventional piping system is proposed. The unsteady flowrate is determined indirectly by using easily-measured pressure signals and implemented in a controller which is designed based on wave propagation and superposition principles. Simulated and experimental results on a test rig show a good attenuation. It is concluded that a well-designed noise attenuator could potentially provide significant reduction in pressure pulsation in a piping system.
Efficiency Modeling and Experimental Validation of a Variable Displacement Linkage Pump
Authors: Wilhelm Shawn , Van de Ven James
Published: February 2014

The power density of hydraulic drive trains make variable displacement machines appealing to a wide range of applications such as mobile hybrid systems, displacement controlled actuation of heavy machinery, and hydrostatic transmissions for wind power. Current state of the art variable displacement pumps suffer from poor efficiencies at low displacements, thus limiting the potential benefits of hydraulic solutions. Here, a variable displacement linkage pump is presented as a promising method for achieving high efficiency across the full displacement range. In this paper, the linkage kinematics and dynamics are discussed, an energy loss model is presented and used to drive design decisions of a first generation prototype, and experimental results are presented to validate the model. It will be shown that this linkage-based, variable, positive displacement architecture shows promise as a highly efficient alternative to other axial piston machines across a wide range of displacements.
Research on the Constant Speed Control System of Hydraulic Motor Under Variable Flow-Rate Input Based on Dual-PID Method
Authors: Ruijia Huang , Guanglin Shi
Published: February 2014

With the development and application of wind power generation and wave power generation, the hydraulic pump-motor control system has a unique effect on power conversion and constant speed driving of power generator. In this situation, the hydraulic pump-motor control system is required that the output speed of the hydraulic motor must be constant when the flow-rate input is randomly varied. Therefore, the power generator driven by the hydraulic motor can maintain constant speed and generate constant frequency electricity power. Considering the particular requirement mentioned above, this paper proposes a stratified-adjustment closed-loop speed control system which is rough-tuned by a variable-displacement motor and fine-tuned by a bypass proportional flow control valve and a control strategy based on dual-PID method. When the flow-rate from the hydraulic pump is randomly varied, the displacement of the variable-displacement motor and the opening of the bypass proportional flow control valve are stratified adjusting by a dual-PID controller, so that the output speed of the variable-displacement motor can maintain constant despite the flow-rate input varying. The simulation and the experiment show that the dual-PID stratified algorithm is effective for constant speed control of hydraulic motor under variable flow-rate input, and it fulfills the requirement of generating constant frequency electricity power.
Investigation and Comparison of Separate Meter-In Separate Meter-Out Control Strategies
Authors: Pedersen Henrik C. , Andersen Torben O. , Skouboe Tobias , Jacobsen Morten S.
Published: February 2014

In the later years, there has been an increased focus on new valve types, which yield the possibility to do Separate Meter-In Separate Meter-Out (SMISMO) control. This includes both digital valves, but proportional valves with separate metering spools and build in pressure sensors are also emerging. The possibility to independently control the meter-in and meter-out side not only increase the functionality of the system, but also opens up for better performance and/or lowered energy consumption. The focus of the current paper is therefore on investigation and comparison of what may be obtained using multivariable control strategies for SMISMO control of a single axis hydraulic system with a differential cylinder, when not taking other measures to improve performance. The paper first presents an experimentally verified model of the system considered, from which a linear model is derived. Based on the model, the control strategies are discussed and several H∞ controllers are designed, for which both simulation and experimental results are presented. The controllers are evaluated with regard to performance and robustness and compared to a simple SISO control. Based on the findings, the possibilities and limitations of the approach and the different controllers are outlined and discussed.
Assessment of Large-Eddy Simulation (LES) Models for Engine Type Flows: Effect of Model Type and Grid Size
Authors: Han Jun , Singh Satbir , Pomraning Eric
Published: February 2014

In this paper, large-eddy simulations (LES) of engine type flow are performed using commercially available computer code CONVERGE. First, accuracy of the numerical discretization scheme of the code is assessed using well established laminar flow configurations. Then, two different subgrid scale (SGS) models, an eddy-viscosity model of Vreman (Physics of fluids, 16, 2004) and a non eddy-viscosity model of Pomraning and Rutland (AIAA Journal, 40, 2002) are employed to predict turbulent flow characteristics in a piston-valve assembly. A number of grid resolutions are employed to perform the simulations, with and without the SGS models. The mean velocity and the root-mean-squared (RMS) values of the velocity fluctuations are compared with available experimental data. Although satisfactory comparison of model predictions with measured data is obtained, it is found that the predictions are more influenced by the grid resolution than the SGS model contribution.
Short Spray-Penetration for Direct Injection Gasoline-Engines With Numerical Simulation
Authors: Ishii Eiji , Abe Motoyuki , Ehara Hideharu , Ishikawa Tohru
Published: February 2014

Direct injection gasoline-engines have both better engine power and fuel efficiency than port injection gasoline-engines. However, direct injection gasoline-engines also emit more particulate matter (PM) than port injection gasoline-engines do. To decrease PM, fuel injectors with short spray-penetration are required. More effective fuel injectors can be preliminarily designed by numerically simulating fuel spray. We previously developed a fuel-spray simulation. Both the fuel flow within the flow paths of an injector and the liquid column at the injector outlet were simulated by using a grid method. The liquid-column breakup was simulated by using a particle method. The motion of droplets within the air/fuel mixture (secondary-drop-breakup) region was calculated by using a discrete droplet model (DDM). In this study, we applied our fuel-spray simulation to sprays for the direct injection gasoline-engines. Simulated spray penetrations agreed relatively well with measured spray penetrations. Velocity distributions at the outlet of three kinds of nozzles were plotted by using a histogram, and the relationship between the velocity distributions and spray penetrations was studied. We found that shrinking the high-speed region and making the velocity-distribution uniform were required for short spray penetration.
Effect of Load on Close-Coupled Post-Injection Efficacy for Soot Reduction in an Optical, Heavy-Duty Diesel Research Engine
Authors: O’Connor Jacqueline , Musculus Mark P. B.
Published: February 2014

The use of close-coupled post injections of fuel is an in-cylinder soot-reduction technique that has much promise for high efficiency, heavy-duty diesel engines. Close-coupled post injections, short injections of fuel that occur soon after the end of the main fuel injection, have been known to reduce engine-out soot at a wide range of engine operating conditions, including variations in injection timing, EGR level, load, boost, and speed. While many studies have investigated the performance of post injections, the details of the mechanism by which soot is reduced remains unclear. In this study, we have measured the efficacy of post injections over a range of load conditions, at constant speed, boost, and rail pressure, in a heavy-duty, optically-accessible research diesel engine. Here, the base load is varied by changing the main-injection duration. Measurements of engine-out soot indicate that not only does the efficacy of a post injection decrease at higher engine loads, but that the range of post-injection durations over which soot reduction is achievable is limited at higher loads. Optical measurements, including natural luminescence of soot and planar laser-induced incandescence of soot, provide information about the spatio-temporal development of in-cylinder soot through the cycle in cases with and without post injections. The optical results indicate that the post injection behaves similarly at different loads, but that its relative efficacy decreases due to the increase in soot resulting from longer main-injection durations.
Study of Unsteady Airflow in Muffler and Air Box Equivalent Geometries
Authors: Hatat Nicolas-Ivan , Lormier François , Chalet David , Chesse Pascal
Published: February 2014

The Internal Combustion Engines (ICE) are inherently sources of the flow’s unsteadiness in the intake and exhaust ducts. Unsteady flow has a direct impact on the engine’s behavior and performance by influencing the filling and emptying of the cylinder. Air intake boxes as well as muffler geometries, which are very commonly used on the two-wheeled vehicles, have an impact on pressure levels and so, on air filling and performances levels. Thus, the purpose of this paper is to identify and analyze different typical geometries of these elements (air box and muffler) by comparing the test bench results with those obtained by 3D and 1D calculations. In this way, it is possible to establish a methodology for modeling the air box and muffler based on experimental tests and the development of 3D and then 1D model.

In a beginning, studies consist in describing the geometry of the air box and muffler using a combination of tubes and simple volumes. During one-dimensional simulations, the gases properties in a volume must be calculated taking into account a method of filling and emptying. Under transient conditions, the pipe element is considered essentially as one-dimensional. The gas dynamic is described by a system of equations: the equations of continuity, momentum and energy. In the three-dimensional case, all tubes and volumes are meshed and solved using various physical models, equations and hypotheses that will be detailed subsequently.

The study is performed on a shock tube bench. One of the main points is that this type of experimental test allows to test easily different pressure ratios, different geometries and to measure direct and inverse flow. In this way, the propagation of a shock wave is studied in our different geometries and is compared to the pressure signals obtained with 1D and 3D simulations. Once the 1D modeling is obtained, it must be validated in order to be applied in a simulation for Internal Combustion Engine. Validation will be done by direct comparison of results at each stage to ensure that the models and assumptions used in the calculations are correct.
Experimental Investigation of the Variations of Early Flame Development in a Spark-Ignition Direct-Injection Optical Engine
Authors: Hung David L. S. , Chen Hao , Xu Min , Yang Jie , Zhuang Hanyang
Published: February 2014

Experiments under two intake air swirl levels (swirl ratio of 0.55 and 5.68) were conducted to investigate the early flame development of combustion in a single-cylinder spark-ignition direct-injection engine. The engine was equipped with a quartz insert in the piston which provided an optical access to its cylinder through the piston. The crank angle resolved combustion images through the piston window and in-cylinder pressure measurements of 250 cycles were recorded simultaneously for both swirl levels at a specified engine speed and low load condition. The early development, size and spatial characteristics extracted from the flame images were analyzed as a function of crank angle degrees after the ignition. Experimental results revealed that the early flame development was strongly influenced by the highly directed swirl motion of intake-air into the combustion cylinder. The location of the start of flame kernel relative to the spark plug position also changed intermittently at different swirl levels. While the structure of the early flame was found to be similar for both swirl levels, the starting location of the flame showed vast difference in how the flame progressed. In general, the flame kernel was formed 2 crank-angle degrees after spark timing for the high swirl level, which was 4 crank-angle degrees earlier than that of low swirl case. For low swirl flow, the early combustion showed more cycle-to-cycle variation in terms of both flame size and centroid location. It was quantitatively shown that increasing swirl ratio from 0.55 to 5.68 could reduce the cycle-to-cycle variation of early flame structure, resulting in about 3 to 4 crank-angle degrees advance of peak pressure location and 1% improvement for COV of IMEP.
Cyclic Variability in Diesel/Gasoline Dual-Fuel Combustion on a Medium-Duty Diesel Engine
Authors: Sun Jiafeng , Bittle Joshua A. , Jacobs Timothy J.
Published: February 2014

Most studies comparing diesel/gasoline dual-fuel operation and single-fuel diesel operation in diesel engines center on time-averaged results. It seems few studies discuss differences in cyclic variability. Motivated by this, the present study evaluates the cyclic variability of combustion in both dual-fuel and single-fuel operations of a diesel engine.

Steady-state tests were done on a medium duty diesel engine with conventional direct injection timings of diesel fuel into the cylinder at one speed and three loads. In addition to single-fuel (diesel) operation, dual-fuel (gasoline and diesel) operation was studied at increasing levels of gasoline fraction. Gasoline fuel is introduced via a fuel injector at a single location prior to the intake manifold (and EGR mixing location). Crank-angle resolved data including in-cylinder pressure and heat release rate obtained for around 150 consecutive cycles are used to assess cyclic variability.

The sources of cyclic variability, namely the factors causing cyclic variability or influencing its magnitude, especially those related to cylinder charge amount and mixture preparation, are analyzed. Fuel spray penetration and cyclic variability of cylinder charging, overall A/F ratio, and fuel injection timing, tend to increase cyclic variability of combustion in dual-fuel operation. On the other hand, fuel type and fuel spray droplet size tend to increase cyclic variability in single-fuel operation.

The cyclic variability in dual-fuel operation in this study is more serious than that in single-fuel operation, in terms of magnitude, indicated by metrics chosen to quantify it. Most measures of cyclic variability increase consistently with increasing gasoline fraction. Variations of gasoline amount and possibly gasoline low temperature heat release cause higher combustion variation in dual-fuel operation primarily by affecting premixed burning.

Statistical methods such as probability density function, autocorrelation coefficient, return map, and symbol sequence statistics methods are used to check determinism. In general, the parameters studied do not show strong determinism, which suggests other parameters must be identified to establish determinism or the system is inherently stochastic. Regardless, dominant sequences and optimal sequence lengths can be identified.
Ignition Delay and Heat-Release Rate for n-Heptane in a Direct-Injection Constant-Volume Combustion Chamber: Experiments and Computations
Authors: Allen James C. , Pitz William J. , Fisher Brian T.
Published: February 2014

The purpose of this study was to characterize combustion behavior for n-heptane using experimental measurements in a direct-injection constant-volume combustion chamber (CVCC) to validate chemical-kinetic mechanisms. This work is focused on compression-ignition (i.e., diesel) combustion, primarily because mechanisms for larger-chain diesel-relevant species are not well developed and require significant attention.

The CVCC used in this work can be pressurized and heated to create engine-relevant conditions that enable study of autoignition behavior. In addition, the chamber is equipped with a high-pressure, common-rail diesel injector, making the study of autoignition and combustion in this system highly relevant to modern diesel engines. By varying injection pressure and duration, it is possible to control global equivalence ratio as well. Chamber pressure during injection and combustion is measured using a piezoelectric transducer, and can be subsequently used to infer heat-release rates. Experimental measurements for n-heptane mostly displayed expected trends. As initial chamber pressure increased, ignition delay decreased and peak pressure increased. As injection duration increased, ignition delay decreased due to faster ignition of richer mixtures, and peak pressure increased due to higher total heat release. The effect of temperature on ignition delay, however, was more complex and suggested some amount of NTC (negative temperature coefficient) behavior. For all conditions, heat-release rates indicated entirely premixed combustion with no hint of mixing-controlled combustion.

Experimental data were compared with results from CHEMKIN-PRO simulations. The model simulated zero-dimensional combustion using a detailed n-heptane mechanism developed at Lawrence Livermore National Laboratory. These computations were used to infer local equivalence ratio information, based on equivalence ratio required in the model to match experimental ignition delay. For most test cases, the model required an equivalence ratio that was at least ∼2× richer than the global value. In addition, equivalence ratios in the model ranged a full order of magnitude, from ∼0.6 to 6, suggesting that local mixture equivalence ratios varied considerably as experimental conditions were varied. Results suggest that improved models that include details of spray physics are required in order to properly predict local equivalence ratios and resulting autoignition characteristics.
Predictions of Transient Flame Lift-Off Length With Comparison to Single-Cylinder Optical Engine Experiments
Authors: Senecal P. K. , Pomraning E. , Anders J. W. , Weber M. R. , Gehrke C. R. , Polonowski C. J. , Mueller C. J.
Published: February 2014

A state-of-the-art, grid-convergent simulation methodology was applied to three-dimensional calculations of a single-cylinder optical engine. A mesh resolution study on a sector-based version of the engine geometry further verified the RANS-based cell size recommendations previously presented by Senecal et al. [1]. Convergence of cylinder pressure, flame lift-off length and emissions was achieved for an adaptive mesh refinement cell size of 0.35 mm. Full geometry simulations, using mesh settings derived from the grid convergence study, resulted in excellent agreement with measurements of cylinder pressure, heat release rate and NOx emissions. On the other hand, the full geometry simulations indicated that the flame lift-off length is not converged at 0.35 mm for jets not aligned with the computational mesh. Further simulations suggested that the flame lift-off lengths for both the non-aligned and aligned jets appear to be converged at 0.175 mm. With this increased mesh resolution, both the trends and magnitudes in flame lift-off length were well predicted with the current simulation methodology. Good agreement between the overall predicted flame behavior and the available chemiluminescence measurements was also achieved. The present study indicates that cell-size requirements for accurate prediction of full geometry flame lift-off lengths may be stricter than those for global combustion behavior. This may be important when accurate soot predictions are required.
Numerical Study of the Combustion Characteristics of a Diesel Micro Pilot Ignited DI Gasoline Engine With Turbocharging and Cooled EGR
Authors: Zhu Yuhua (York) , Salman Nameer , Freeman Kevin , Reese Ronald , Wang Zihan , Scarcelli Riccardo , Som Sibendu
Published: February 2014

Advanced technologies combining turbocharging, downsizing, direct injection, and cooled EGR are being intensively investigated in order to significantly improve the fuel economy of spark-ignition (SI) gasoline engines. To avoid the occurrence of knock and to improve the thermal efficiency, a significant fraction of EGR is often used. Due to the significant fraction of EGR, the ignition source needs to be enhanced to ensure high combustion stability. In addition to advanced spark-based solutions, diesel micro-pilot (DMP) technology has been proposed in recent years where the diesel fuel replaces the spark-plug as the ignition source.

This paper studies the combustion characteristics of a diesel micro pilot ignited gasoline engine, employing direct injection of gasoline and diesel as well as turbocharging and cooled EGR. A multi-dimensional CFD code with a chemical kinetic calculation capability was extensively validated across the engine speed and load range in a previous study [1]. This paper explores the influence of a number of parameters on DMP combustion behavior, including: diesel pilot mass fraction, start of injection (SOI), DMP injection strategy, as well as EGR rate, air/fuel ratio, and DI gasoline/air mixture inhomogeneity.

Besides, the comparison of DMP ignited combustion with traditional spark ignited combustion is also made in terms of EGR tolerance, lean burn limit, and DI gasoline air mixture inhomogeneity. Finally, numerical simulations aimed at optimizing both gasoline and diesel injection parameters, as well as EGR rate in order to enhance the engine performance in the DMP combustion mode, are discussed.
A Comparison of Valving Strategies Appropriate for Multi-Mode Combustion Within a Downsized Boosted Automotive Engine: Part B — Mid Load Operation Within the SACI Combustion Regime
Authors: Gerow Matthew S. , Shingne Prasad S. , Triantopoulos Vassilis , Bohac Stanislav V. , Martz Jason B.
Published: February 2014

Spark Assisted Compression Ignition (SACI) is a combustion mode that may offer significant efficiency improvements compared to conventional spark-ignited combustion systems. Unfortunately, SACI is constrained to a relatively narrow range of dilution levels and top dead center temperatures. Both positive valve overlap (PVO) and negative valve overlap (NVO) strategies may be utilized to attain these conditions at low and intermediate engine loads.

The current work compares 1D thermodynamic simulations of PVO valving strategies and a baseline NVO strategy in a downsized boosted automotive engine with variable valve timing capability. As future downsized boosted engines may employ multiple combustion modes, the goal of this work is the definition of valving strategies appropriate for SACI combustion at low to moderate loads and SI combustion at moderate to high loads for an engine with fixed camshaft profiles. PVO durations, valve opening timings and peak lifts are investigated at low to moderate loads and are compared to a baseline NVO configuration in order to assess valving strategies appropriate for multi-mode combustion operation. A valvetrain kinematic model is used to translate the desired valve lift profiles into camshaft profiles, while a kinematic analysis is used to calculate piston to valve clearances and to define the practical limits of the PVO strategies. The NVO and PVO strategies are also compared to throttled SI operation at part load to assess the overall efficiency benefit of operating under the thermodynamic conditions of the SACI combustion regime.

While the results of this study are engine specific, there are several camshaft profiles that are appropriate for the use of PVO rebreathing type valve events. For the range of PVO valve events examined and taking into consideration piston to valve interference, the use of high exhaust and low intake lifts with early exhaust valve opening timing and long PVO durations enables high levels of internal EGR with relatively low pumping losses.
The Effect of Spark Plug Electrode Geometry on Combustion Rates in a High Performance Automotive Engine
Authors: Worm Jeremy J. , McFarland Jim , Jehlik Forrest , Dice Paul W. , Miers Scott A.
Published: February 2014

Spark plugs utilizing a J-wire electrode are standard in most automotive engines and have been for decades. However, innumerable alternative spark plug designs have been introduced. This paper examines the potential benefit of one particular alternative electrode geometry in a high-performance automotive engine. The alternative spark plug that is investigated is a commercially available aftermarket unit. The testing included detailed analysis of both brake and indicated parameters including MEP and burn rates. Testing was conducted under both steady state and transient conditions, and encompassed multiple induction systems and test fuels including E85. The test engine was a commercially available high performance aftermarket engine assembly intended for motorsports.

This paper includes the optimal settings for ignition timing and lambda and the process by which those values were determined. The combustion analysis shows the alternative spark plug electrode resulted in an increased early burn rate, which in turn lead to an overall advancing of the combustion phasing. To better decouple combustion phasing effects from test to test variation on brake output parameters, an empirical model is developed and exercised. The model describes the expected change in brake output resulting from the shift in combustion phasing induced by the alternative spark plug geometry.
Investigation of Combustion Phasing Control Strategy During Reactivity Controlled Compression Ignition (RCCI) Multi-Cylinder Engine Load Transitions
Authors: Wu Yifeng , Hanson Reed , Reitz Rolf D.
Published: February 2014

The dual fuel reactivity controlled compression ignition (RCCI) concept has been successfully demonstrated to be a promising, more controllable, high efficiency and cleaner combustion mode. A multi-dimensional computational fluid dynamics (CFD) code coupled with detailed chemistry, KIVA-CHEMKIN, was applied to develop a strategy for phasing control during load transitions. Steady-state operating points at 1500 rev/min were calibrated from 0 to 5 bar brake mean effective pressure (BMEP). The load transitions considered in this study included a load-up and a load-down load change transient between 1 bar and 4 bar BMEP at 1500 rev/min. The experimental results showed that during the load transitions, the diesel injection timing responded in 2 cycles while around 5 cycles were needed for the diesel common-rail pressure to reach the target value. However, the intake manifold pressure lagged behind the pedal change for about 50 cycles due to the slower response of the turbocharger.

The effect of these transients on RCCI engine combustion phasing was studied. The CFD model was first validated against steady-state experimental data at 1 bar and 4 bar BMEP. Then the model was used to develop strategies for phasing control by changing the direct port fuel injection (PFI) amount during load transitions. Specific engine operating cycles during the load transitions (6 cycles for the load-up transition and 7 cycles for the load-down transition) were selected based on the change of intake manifold pressure to represent the transition processes. Each cycle was studied separately to find the correct PFI to diesel fuel ratio for the desired CA50 (the crank angle at which 50 % of total heat release occurs). The simulation results showed that CA50 was delayed by 7 to 15 degrees for the load-up transition and advanced by around 5 degrees during the load-down transition if the pre-calibrated steady-state PFI table was used. By decreasing the PFI ratio by 10 % to 15 % during the load-up transition and increasing the PFI ratio by around 40 % during the load-down transition, the CA50 could be controlled at a reasonable value during transitions. The control strategy can be used for closed-loop control during engine transient operating conditions. Combustion and emission results during load transitions are also discussed.
Development of Radio Frequency Sensing for In-Situ Diesel Particulate Filter State Monitoring and Aftertreatment System Control
Authors: Sappok Alexander , Bromberg Leslie
Published: February 2014

Diesel particulate filters (DPF) have seen widespread application in the United States and Europe to meet stringent diesel particulate matter (PM) emissions regulations. Now commonplace on most on-road diesel vehicles, DPFs are being increasingly applied to diesel-powered off-road equipment as additional regulations are phased in. Further, recent awareness of particulate matter emissions from gasoline direct injection engines has motivated additional study into potential applications of gasoline particulate filters (GPF).

Key to the efficient operation of the combined engine and emissions aftertreatment system, is the accurate determination of the filter loading state, to enable precise control of filter regeneration and on-board diagnostics. Currently pressure- and model-based controls are utilized, in parallel, to provide an indirect estimate of filter loading. This work presents results of an investigation applying radio frequencies (RF) to monitor the accumulation of particulate matter in the DPF, providing a direct, in-situ determination of filter loading state. Simulation results, supported by experimental measurements, are provided to demonstrate the utility of the technique to monitor not only the filter loading state but also to provide a measure of the spatial distribution of the accumulated material. The results of this work indicate significant potential to apply RF-based sensing for improved monitoring and control of the particulate filter in a range of applications.
A Cycle-to-Cycle Method to Predict HCCI Combustion Phasing
Authors: Vaughan Adam , Bohac Stanislav V.
Published: February 2014

Homogeneous Charge Compression Ignition (HCCI) is a low temperature combustion strategy that simultaneously improves fuel efficiency and lowers engine-out NOx emissions. Unfortunately, broad usage of HCCI is hampered by combustion instabilities and a limited operation envelope. To help understand these limitations, this paper treats individual cylinders in a production four-cylinder engine as dynamical systems that iterate CA90 (the crank angle where 90% of net heat release is achieved) cycle-to-cycle as the engine operates in an unboosted, negative valve overlap HCCI combustion mode. This approach is shown to provide qualitative understanding of the stability limit bifurcation behavior, while also enabling quantitative cycle-to-cycle predictions of combustion phasing across a wide variety of transient and steady-state conditions, right up to complete misfire.
Improvement of a Diesel Engine Water Cooling Performance Through Implementation of Different Cooling Designs
Authors: Jafarabadi Mazdak , Chamani Hamidreza , Jazayeri Seyed Ali
Published: February 2014

Improving engine cooling performance requires sophisticated and intelligent engine cooling design especially when interactions of all engine parts are to be considered. The cooling system would highly influence engine thermal efficiency, durability and engine design criteria. Several attempts have been made by engine designers to improve the cooling design during the past decades, each with particular purpose considerations.

In this paper, based on the cylinder head flame face of an existing heavy duty medium speed diesel engine, three other flame face cooling systems are designed, modeled and changes are implemented using a three dimensional computer aided design modeling software. Modeled cylinder head flame face cooling concepts are experiencing the effect of cooling passages geometry changes on performance of thermal efficiency, effective subcooled regions and other resultant factors.

A detailed coupled computational fluid dynamic and thermal finite element analysis for one cylinder bank assembly is performed several times; paying special attention to the risky areas to get comparative results to assess the flame face cooling designs. Engine specifications and loading conditions together with the engine performance data are available from test rig. Initial and boundary conditions have been determined through a global model simulation and analysis.

The subcooled nucleate boiling heat transfer computation is carried out using the boiling departure lift-off model. In order to obtain the temperature for components under consideration, a comprehensive thermal analysis has been performed coupling with the detailed CFD analysis to reach an accepted value through transferring data between the CFD and FEA software. This method leads to an accurate prediction of the wall temperature and heat flux.

It is observed that proper cooling design could improve wall temperature and thermal stress related phenomena significantly. The advantages and disadvantages of each concept are discussed and preferred flame face design is demonstrated. Calculated results of original design are validated with test cell records.
Thermodynamic Modeling of an Epitrochoidal Engine Cycle
Authors: Grammer Thomas Allen , Bittle Robert R.
Published: February 2014

A thermodynamic performance model has been developed for a new four-stroke piston engine design in which the crankshaft path is epitrochoidal, or non-circular. The model is based on an Otto air-standard cycle with non-ideal effects of friction, valve and spark timing, heat transfer, volumetric efficiency, and fuel burn timing then added. The same modeling approach was then used in developing a standard circular path engine model for comparison: the result being two discrete models varying only in their crankshaft paths, and thus piston path timing.

The thermodynamic modeling was one phase of a larger senior design project in which senior engineering students were tasked with answering the question of whether the epitrochoidal crankshaft path engine will produce more power than a standard circular path engine of the same size and compression ratio. The starting point for the effort was the epitrochoidal crankshaft design description given in the patent, followed by major challenges of design, fabrication, modeling, and testing of a prototype engine. A Briggs and Stratton model 20 was employed as the standard circular crankshaft path comparison engine, and upon which the epitrochoidal prototype engine geometry was based. The result was two test engines of the same size and compression ratio, but differing in crankshaft path. Thermodynamic modeling, however, is the primary focus of the paper presented herein. Details of the design/fabrication/testing phases of the larger project are included in another paper, currently in preparation.

The modeling description starts with the development of the mathematical equations describing the piston movement within the standard engine and the epitrochoidal engine, followed by the specifics of the thermodynamic modeling and inclusion of non-ideal effects. The model calibration to measured data is developed next, and finally a prediction of the epitrochoidal engine performance is shown to agree with measured data for the prototype engine. The testing did in fact show an increase in power in the epitrochoidal prototype engine, and the modeling was used to explain the improvements attributable to the epitrochoidal design. These results also affirmed the comparative modeling approach that was used.
Study of Cylinder Charge Control for Enabling Low Temperature Combustion in Diesel Engines
Authors: Divekar Prasad , Asad Usman , Han Xiaoye , Chen Xiang , Zheng Ming
Published: February 2014

Suitable cylinder charge preparation is deemed critical for the attainment of a highly homogeneous, diluted, and lean cylinder charge which is shown to lower the flame temperature. The resultant low temperature combustion (LTC) can simultaneously reduce the NOx and soot emissions from diesel engines. This requires sophisticated coordination of multiple control systems for controlling the intake boost, exhaust gas recirculation (EGR), and fueling events. Additionally, the cylinder charge modulation becomes more complicated in the novel combustion concepts that apply port injection of low reactivity alcohol fuels to replace the diesel fuel partially or entirely. In this work, experiments have been conducted on a single cylinder research engine with diesel and ethanol fuels. The test platform is capable of independently controlling the intake boost, EGR rates, and fuelling events. Effects of these control variables are evaluated with diesel direct injection and a combination of diesel direct injection and ethanol port injection. Data analyses are performed to establish the control requirements for stable operation at different engine load levels with the use of one or two fuels. The sensitivity of the combustion modes is thereby analyzed with regard to the boost, EGR, fuel types and fueling strategies. Zero-dimensional cycle simulations have been conducted in parallel with the experiments to evaluate the operating requirements and operation zones of the LTC combustion modes. Correlations are generated between air-fuel ratio (λ), EGR rate, boost level, in-cylinder oxygen concentration and load level using the experimental data and simulation results. Development of a real-time boost-EGR set-point determination to sustain the LTC mode at the varying engine load levels and fueling strategies is proposed.
Experimental Studies of High Efficiency Combustion With Fumigation of DME and Propane Into Diesel Engine Intake Air
Authors: Prabhakar Bhaskar , Jayaraman Srinivas , Vander Wal Randy , Boehman André
Published: February 2014

This work explores the role of the ignition quality of a fumigated fuel on combustion phasing and brake thermal efficiency (BTE), which was investigated in a 2.5L turbocharged common rail light-duty diesel engine. Different combinations of dimethyl ether (DME) and propane were fumigated into the intake air and displaced some of the directly injected ultra-low sulfur diesel fuel (ULSD) needed to maintain the engine and a constant speed and load. Fumigation of DME and propane significantly increased BTE and reduced brake specific energy consumption (BSEC) compared to the baseline diesel condition with no fumigation. A mixture of 20% DME with 30% propane provided the maximum BTE, with 24% reduction in BSEC, however, at the expense of increasing peak cylinder pressure by 6 bar, which was even higher at greater DME substitutions. Fumigated DME auto-ignited early, ahead of top dead center (TDC), showing the typical low temperature and high temperature heat release events and propane addition suppressed the early low temperature heat release (LTHR), shifting more of the DME heat release closer to TDC. Total hydrocarbon emissions increased while NOx emissions reduced with increasing fumigation.
Analyses for Lateral Deflection of Railroad Track Under Quasi-Static Loading
Authors: Jeong David Y.
Published: February 2014

This paper describes analyses to examine the lateral deflection of railroad track subjected to quasi-static loading. Rails are assumed to behave as beams in bending. Movement of the track in the lateral plane is constrained by idealized resistance characteristics, while movement in the vertical plane is resisted by a continuous, linear and elastic foundation. These analyses are based on solving the ordinary differential equations for beam deflections. In certain cases, convenient mathematical expressions may be used to represent idealized lateral resistance characteristics and derive closed-form equations to relate lateral force as a function of track lateral deflection. However, in general, the idealized lateral resistance characteristic may be nonlinear, in which case numerical methods are required to examine the lateral load versus track lateral deflection behavior. In these general cases, a Fourier series technique is used to solve the governing equations numerically.

The analysis of track lateral deflection subjected to quasi-static loads may be applied to examine track shift. For example, lateral resistance of track may be measured using Track Lateral Pull Tests (TLPT). The Fourier method is also used to examine the relationship between lateral and vertical wheel loads and track lateral shift.