bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfated-polysaccharide fraction extracted from red algae Gracilaria birdiae ameliorates trinitrobenzenesulfonic acid-induced colitis in rats
Authors: Brito Tarcisio V , Neto José P R P , Prudêncio Rafael S , Batista Jalles A , Júnior José S C , Silva Renan O , Franco Álvaro X , Aragão Karoline S , Soares Pedro M G , Souza Marcellus H L P , Chaves Luciano S , Freitas Ana L P , Medeiros Jand-V R , Barbosa André L R
Published: February 2014

Objectives

The aim of this study was to evaluate the protective effect of the sulfated-polysaccharide (PLS) fraction extracted from the seaweed Gracilaria birdiae in rats with trinitrobenzenesulfonic acid (TNBS)-induced colitis.

Methods

In the experiments involving TNBS-induced colitis, rats were pretreated with polysaccharide extracted from G. birdiae (PLS: 30, 60 and 90 mg/kg, 500 μL p.o.) or dexamethasone (control group: 1 mg/kg) once daily for 3 days starting before TNBS instillation (day 1). The rats were killed on the third day, the portion of distal colon was excised and washed with 0.9% saline and pinned onto a wax block for the evaluation of macroscopic scores. Samples of the intestinal tissue were used for histological evaluation and assays for glutathione (GSH) levels, malonyldialdehyde (MDA) concentration, myeloperoxidase (MPO) activity, nitrate and nitrite (NO3/NO2) concentration and cytokines levels.

Key findings

PLS treatment reduced the macroscopic and microscopic TNBS-induced intestinal damage. Additionally, it avoided the consumption of GSH, decreased pro-inflammatory cytokine levels, MDA and NO3/NO2 concentrations and diminished the MPO activity.

Conclusions

Our results suggest that the PLS fraction has a protective effect against intestinal damage through mechanisms that involve the inhibition of inflammatory cell infiltration, cytokine releasing and lipid peroxidation.
Medical Mistrust, Perceived Discrimination, and Satisfaction With Health Care Among Young‐Adult Rural Latinos
Authors: López‐Cevallos Daniel F. , Harvey S. Marie , Warren Jocelyn T.
Published: February 2014

Purpose

Little research has analyzed mistrust and discrimination influencing receipt of health care services among Latinos, particularly those living in rural areas. This study examined the associations between medical mistrust, perceived discrimination, and satisfaction with health care among young‐adult rural Latinos.

Research Design

This cross‐sectional study analyzed data from 387 young‐adult Latinos (ages 18‐25) living in rural Oregon. The Behavioral Model of Vulnerable Populations was utilized as the theoretical framework. Correlations were run to assess bivariate associations among variables included in the study. Ordered logistic regression models evaluated the associations between medical mistrust, perceived discrimination, and satisfaction with health care.

Results

On average, participants used health services 4 times in the past year. Almost half of the participants had health insurance (46%). The majority reported that they were moderately (32%) or very satisfied (41%) with health care services used in the previous year. In multivariable models, medical mistrust and perceived discrimination were significantly associated with satisfaction with health care.

Conclusions

Medical mistrust and perceived discrimination were significant contributors to lower satisfaction with health care among young‐adult Latinos living in rural Oregon. Health care reform implementation, currently under way, provides a unique opportunity for developing evaluation systems and interventions toward monitoring and reducing rural Latino health care disparities.
Biosystematics and evolutionary relationships of perennial Triticeae species revealed by genomic analyses
Authors: WANG Richard R. C. , LU Baorong
Published: February 2014

Understanding the classification and biosystematics of species in Triticeae Dumort., an economically important tribe in the grass family (Poaceae), is not an easy task, particularly for some perennial species. Does genomic analysis facilitate the understanding of evolutionary relationships of these Triticeae species? We reviewed literature published after 1984 to address questions concerning: (1) genome relationships among the monogenomic diploid species; (2) progenitors of the unknown Y genome in Elymus polyploids, X genome in Thinopyrum intermedium, and Xm genome in Leymus; and (3) genome constitutions of some perennial Triticeae species that were unknown or misidentified. A majority of publications have substantiated the close affinity of the Eb and Ee genomes in Th. bessarabicum and Th. elongatum, supporting the use of a common basic genome symbol. The E genome is close to the St genome of Pseudoroegneria and ABD genomes of Triticum/Aegilops complex, providing an explanation for transferring genes from the E to ABD genomes with relative ease. Although the solid proof is still lacking, the W, P, and especially Xp genomes are possible origins for the Y genome of polyploid Elymus. The absence of the E genome and the allopolyploidy nature of tetraploid Leymus species have been unequivocally confirmed by both cytogenetic and molecular studies. However, the donor of the Xm genomes of Leymus was only speculated to be related to the P genome of Agropyron and F genome of Eremopyrum. Intermediate wheatgrass (Th. intermedium) has been extensively studied. The presence of the St (as the previously designated X) genome in Th. intermedium is now unequivocal. Its two more closely related E1 and E2 genomes are shown to be older versions of the E genome rather than the current Eb and Ee genomes. Speciation of Th. intermedium was similar to that of Triticum aestivum, in which the Js/Es (like B) genomes had the greatest differentiation from the current J (Eb) genome owning to repetitive sequences of the V genome, whereas its St (like D) had the least differentiation from the current St genome. Species with unknown or misidentified genomes have been correctly designated, including those with the ESt, StP, StPY, StWY, EStP, HW, StYHW, and NsXm genomes. Some of those species have been transferred to and renamed in appropriate genera.
Comparing the Montreal Cognitive Assessment with Mini‐Mental State Examination in Japanese Parkinson's disease patients
Authors: Ohta Kouichi , Osada Takashi , Shinohara Yukito , Suzuki Norihiro , Takahashi Kazushi , Seki Morinobu , Nihei Yoshihiro , Iwasawa Satoko , Gotoh Jun , Yamaguchi Keiji , Komatsumoto Satoru , Isozumi Kazuo , Kobari Masahiro , Mihara Ban , Morita Yoko , Yasutomi Daisuke , Gotoh Kyoko , Muramatsu Kazuhiro , Shirai Toshitaka , Tomita Yutaka , Sato Hideki ,   the Keio Parkinson's Disease Database
Published: February 2014

Background and Aim

The Montreal Cognitive Assessment (MoCA) is the most suitable measure for screening cognitive impairment in Parkinson's disease (PD). However, the utility of the MoCA has not been documented sufficiently, especially in Asian populations. The present multicenter study included a large number of Japanese patients, and compared Mini‐Mental State Examination (MMSE) and MoCA scores in PD patients.

Methods

We carried out a cross‐sectional study. Idiopathic PD patients (n = 304; age 70.6 ± 8.3 years (mean ± SD); disease duration 6.6 ± 5.1 years; Hoehn and Yahr stage 2.7 ± 0.7) were registered at 13 participating hospitals, and their clinical/neurological/cognitive features were examined using Japanese versions of the MMSE and MoCA.

Results

The MMSE and MoCA scores were 26.3 ± 3.6 (range 12–30) and 20.9 ± 5.0 (range 5–30), respectively, and showed a strong correlation (R2 = 0.74, P < 0.001) with each other. A MMSE score of <26 was observed in 35% of the participants. A MoCA score of <21 had 89% sensitivity and 83% specificity, comparable with a MMSE score of <26. The two scores were correlated with age (R2 = 0.12 and 0.20, respectively; P < 0.0001), but not with Hoehn and Yahr stage or disease duration.

Conclusions

One‐third of the patients had a MMSE score of <26, a diagnostic criterion of PD with dementia. A MoCA score of <21 seemed comparable with a MMSE score of <26. The two scores were correlated with age, rather than severity of motor symptoms, suggesting that cognitive decline might be independent of motor decline in PD.
Nonlinear Dynamic Analysis of a Parametrically Excited Cold Rolling Mill
Authors: Kapil Sajan , Eberhard Peter , Dwivedy Santosha K.
Published: February 2014

In this work, a four high cold rolling mill is modeled as a spring-mass-damper system considering horizontally and vertically applied time-dependent forces due to the interaction between the strip and the working rolls. The effect of vibration of the moving strip on the work roll vibration is also considered for developing the governing equation of motion of the system which is found to be that of a nonlinear parametrically excited system. The governing equation of motion is solved by using the method of multiple scales to find the instability regions and frequency-response curves of the system. The critical amplitude of horizontal load in roll bite is calculated and the frequency-response is studied in detail considering the effect of various process parameters, such as velocity, thickness of strip, time delay, amplitude, and frequency of horizontal load in roll bite. This work can find application in the design and development of high speed and chatter free rolling mills.
Flaw Testing of Fiber Reinforced Composite Pressure Vessels
Authors: Makinson John , Newhouse Norman L.
Published: February 2014

The ASME Boiler Pressure Vessel Project Team on Hydrogen Tanks, in conjunction with other ASME Codes and Standards groups, is developing Code Cases and revisions to the Boiler and Pressure Vessel Code, including such to address the design of composite pressure vessels. The Project Team had an interest in further understanding the effect of cuts to the surface of composite tanks, and how the burst pressure would be affected during the lifetime of the pressure vessel. A test program was initiated to provide data on initial burst pressure, and burst pressure after pressure cycling, of composite cylinders with cuts of different depth. This test program was conducted by Lincoln Composites under contract to ASME Standards Technology LLC, and was funded by National Renewable Energy Laboratory (NREL) [1]. These results were considered during the development and approval of the ASME Code Cases and Code Rules. Thirteen pressure vessels with a design pressure of 24.8 MPa (3600 psi), approximately 0.406 m (16.0 in.) in diameter and 1.02 m (40.2 in.) long, were tested to investigate the effects of cuts to the structural laminate of a composite overwrapped pressure vessel with respect to cycling and burst pressure. Two flaws, one longitudinal and one circumferential, were machined into the structural composite. The flaws were 57 mm long by 1 mm wide (2.25 in. × 0.04 in.) and varied in depth from 10% to 40% of the structural composite thickness of 11.4 mm (0.45 in.). These pressure vessels were cycled to design pressure 0, 10,000, and 20,000 times then burst. The resulting burst pressures were evaluated against the performance of a pressure vessel without flaws or cycling. The burst pressures were affected by depth of cut, but the pressure cycling did not have a significant effect on the burst pressure.
Model Tests for Evaluating the Impact of Low Viscosity Tailor-Made Biofuels on Tribological Contacts in Injection Pumps
Authors: Heitzig Stefan , Weinebeck Alexander , Murrenhoff Hubertus
Published: February 2014

In the scope of the cluster of excellence “Tailor-made Fuels from Biomass” new biofuels are developed within an interdisciplinary research approach at RWTH Aachen University. To ensure a safe and reliable functioning of the new fuels in combination with state of the art fuel injection equipment, every fuel has to fulfil requirements regarding its tribological performance, which depends on characteristics like dynamic viscosity and fuel lubricity. Hence, one focus of the cluster lies on the tribological characteristics of the fuel candidates.

Biofuel candidates which have been investigated so far and which are suitable for the use in self-ignition engines as surrogates for fossil diesel fuel tend to have lower viscosities and show varying lubrication behaviour, compared to diesel.

As a standard test method for diesel fuel lubricity the HFRR test is well established. Nevertheless, relying on the established diesel-pass/fail criterion, which is defined in several norms, is disputable, since the investigated biofuels differ strongly from modern diesel fuels.

To identify the relevant fuel properties and to gain a more detailed understanding of the wear and friction processes within the critical contacts, results of different tribological test methods, including the HFRR test and a disc-on-disc tribometer, are presented, compared and discussed in this paper. In order to estimate the validity of the established HFRR pass/fail criterion for low viscosity biofuels the experimental results are compared to simulation outcomes of elasto-hydrodynamic simulations of the main tribological contacts in a standard common rail injection pump.
Constrained Multi-Objective Optimization of a Hydraulic Flywheel Accumulator
Authors: Strohmaier Kyle G. , Van de Ven James D.
Published: February 2014

Improving energy storage technology is an important means of addressing concerns over fossil fuel scarcity and energy independence. Traditional hydraulic accumulator energy storage, though favorable in power density, durability, cost, and environmental impact, suffers from relatively low energy density and a pressure-dependent state of charge. The hydraulic flywheel accumulator concept utilizes both pneumatic and kinetic energy domains by employing a rotating pressure vessel.

This paper describes a mathematical model of the hydraulic flywheel accumulator and presents the results of a multi-objective optimization of the associated design parameters. The two optimization objectives are to minimize the total system mass and minimize the total energy converted between the pneumatic and kinetic domains during operation. These objectives are pursued by varying five design parameters: accumulator radius, wall thickness, and length; end cap length; and maximum angular velocity. Constraints on combinations of these design parameters are imposed by material stress, as well as the energy capacity required to complete a specified drive cycle. This optimization approach can be used to guide the design of a hydraulic flywheel accumulator for a variety of different applications.
Geometric Optimization of a Hydraulic Motor Rotary Valve
Authors: Tian Hao , Van de Ven James D.
Published: February 2014

The performance of a hydraulic motor is strongly influenced by the timing, leakage, and friction of the valves connecting to the pressure and tank ports. For the application of a linkage-based hydraulic piston motor, a novel clearance sealed cylindrical rotary valve is introduced. A model of the cylinder pressure dynamics is formulated from the bulk modulus definition and solved using a variable-step Runge-Kutta stiff solver. Energy loss equations are developed and used to aid the creation of objective functions. A geometric optimization of the motoring efficiency is conducted based on coupled relationships: including throttling across the transitioning and fully open valve ports, viscous friction, and leakage, but excluding piston related losses. A simple genetic algorithm is used to obtain the optimized geometry, and a theoretical system efficiency greater than 97% is achieved. A multi-objective sub-population genetic algorithm is then used to generate Pareto Optimal solutions for different combinations of efficiency and output power. A sensitivity study of the valve timing and rotational frequency shows the starting angle of the pressure port and the width of the rotor orifice dominate the performance while the system frequency has negligible effects.
Detection and Isolation of Faults in Mobile Hydraulic Valves Based on a Reduced-Order Model and Adaptive Thresholds
Authors: Nurmi Jarmo , Mattila Jouni
Published: February 2014

Detecting and isolating faults in complex engineering systems is important for properly planning maintenance, and it leads to decreases in down and repair times and to an increase in system performance. Mobile hydraulic valves, which are characterized by functions such as pressure-compensation and pilot-operation, are such complex systems that they could tremendously benefit from a real-time, accurate fault detection and isolation system. However, the complexity of these valves means that accurate full-state modeling is generally difficult and time-consuming. This paper proposes a reduced-order model for the fault detection of an open-loop-controlled mobile hydraulic valve. This reduced-order model is used along with statistically computed adaptive thresholds for the purpose of enhancing the reliability of fault detection. The considered faults include valve spool jamming caused by hydraulic fluid impurities, leakages caused by wear-induced increased clearances between the valve spool and sleeve, and sensor faults. The reduced-order model omits the modeling of pressure compensator dynamics by using a measurement of the pressure compensator, and pilot pressure dynamics by measuring the pilot pressures that drive the main spool. Experimental results from a commercial mobile hydraulic valve controlling a 2-DOF hydraulic crane show the practicality of the reduced-order modeling and adaptive threshold arrangements in this fault detection task. As a downside, a reduced set of faults can be isolated with the reduced-order model, but as a future consideration a bigger set of fault patterns with a full model are given and compared with the results obtained.
Simulation of Fluid Power Systems in Consideration of Uncertainties
Authors: Rüdenauer Andreas , Thiebes Phillip
Published: February 2014

This paper presents the fundamental interrelation of uncertainty in the context of the modeling and simulation process of fluid power systems. Building up a simulation model means to represent a real system and its dynamic behavior in an experimental model. This process generally requires a model simplification. Additionally, in an early stage of product development, a certain lack of knowledge about a system is to be assumed. These so called epistemic uncertainties lead to a deviation of the simulated system’s behavior from the real one. One possibility to consider such uncertainties in simulation is by using the approach of fuzzy arithmetic. This approach allows substituting crisp parameter values through fuzzy intervals. This way, uncertainty-sensitive simulation results can be obtained and the reliability of simulation can be significantly increased.

Especially for the simulation of fluid power systems with lumped parameters, a trade-off between simulation performance and the level of detail of the model has often to be accepted. The assumption of uncertainties in fluid power simulation shows the potential of creating simplified simulation models, which at the same time promise to have a high conformance to the real system behavior.

Using the fuzzy arithmetic approach under application of the transformation method by Hanss, the potential for fluid power system simulation in consideration of epistemic uncertainties is explained and evaluated. Therefore, a simulation model is tested as an example application using different degrees of parameter fuzzification.
Internal Leakage Fault Detection for Variable Displacement Axial Piston Pump
Authors: Kivelä Tuomo , Mattila Jouni
Published: February 2014

In mobile machines, reliable condition monitoring (CM) of hydraulic system would be very beneficial because it could decrease the maintenance costs in case of a failure. It should also foresee potentially harmful, slight defects in the system, before they lead to system downtime. Very often the focus of the CM is in short term performance. For example, a neural network-based CM solutions require an extensive data collection and teaching phase. A model-based CM on the other hand an accurate model of the process which is tuned into a known operation points. However, it is typical that the operation conditions change. As a result, the process models become outdated and cause-action definitions do not apply to the changed situation. Therefore, a new model structure, Multi-Variable Histogram (MVH), for CM purposes is introduced. The MVH model is statistical nonlinear model of variable relations. The model is based on schematics where the system operation point changes are taken into account. The system input variables, as explanatory variables, define the operation point for the variable being observed. When the effects of the system input variables excluding faults are taken into account, faults can be seen as operation point changes. MVH model based CM solution includes the key elements of a long-term manageable CM solution. Furthermore, the experimental tests are carried-out with a variable displacement axial piston pump to verify the performance of the solution.
Simulation of Dynamic Behaviour of a Digital Displacement Motor Using Transient 3D Computational Fluid Dynamics Analysis
Authors: Roemer Daniel B. , Johansen Per , Pedersen Henrik C. , Andersen Torben O.
Published: February 2014

A fast rotating 1500 rpm radial piston digital displacement motor connected to a 350 bar high pressure manifold is simulated by means of transient 3D CFD analysis of a single pressure chamber. The analysis includes dynamic piston and valve movement, influencing the boundaries of the fluid domain. Movement of the low and high pressure valves is coupled to fluid forces and valve actuation is included to control the valve movement according to the pressure cycle of the digital displacement motor. The fluid domain is meshed using a structured/unstructured non-conformal mesh, which is updated throughout the simulation using layering zones as required by the moving fluid boundaries. The effect of cavitation at low pressures is included by implementing a pressure dependent density, based on an effective bulk modulus model. In addition, pressure dependent oil viscosity is included in the analysis. As a result of the CFD analysis, the dynamic response of the pressure chamber and valve movement of a digital displacement motor is presented, along with the total efficiency of a multi-chamber motor at full and partial displacement. Simulation predicts that pressure over- and undershoot may be reduced to a few percent of the high pressure manifold level by precise timing and fast switching of the seat valves.
Analysis on the Adaptability of Two Different Hydraulic Energy Recovery Circuits on Various Machine Types and Work Cycles
Authors: Hänninen Henri , Pietola Matti
Published: February 2014

In the task of improving the energy efficiency of a work machine, the implementation of an energy recovery system is in many cases the most effective solution. Simulations and measurements on two distinctive hydraulic recovery circuit types, implemented on a reach truck test bench, have indicated clearly different performance profiles with different work cycle types.

The first of the two systems is based on diverting the flow to be recovered directly to hydraulic accumulators utilizing a digital flow control unit. This system has been measured to exceed cyclic efficiency of 90 percent with optimal system settings in constant load scenarios. However, in mixed goods warehouses this efficiency can be significantly lower. The second recovery system, even though exhibiting slightly lower peak efficiency, has been measured to operate at relatively constant efficiency regardless of the work cycle type. This system is based on hydraulic transformer which varies the pressure/flow ratio in order to maximize the quantity of recovered energy.

In this study these two systems are analyzed in terms of their adaptability to different fork lift types and to different work cycles. The assessment is carried out by analyzing typical machine specific operation cycles, comparing machine complexity versus recovery circuit complexity and by estimations of build costs versus gains.
Study on Dynamic Behavior of a Gas Pressure Relief Valve for a Big Flow Rate
Authors: Sverbilov Victor , Stadnick Dmitry , Makaryants Georgy
Published: February 2014

The paper investigates instable behavior of a poppet-type gas pressure relief valve operating at a big flow rate (more than 2 kg/s) under super critical pressure drop. Instability is experienced as noise and vibration and leads to severe damage of a seat and other elements. Significant and unsteady flow forces coupled with small inherent damping make it difficult to stabilize the system. In previous works, the analytical and experimental research was carried out to reveal the most essential factors influencing stability and dynamic properties of the valve. The impact of the pilot valve dynamics on the system behavior was studied for the purpose of obtaining required accuracy and stability in a wide range of flow rate. It was shown in some testing that unstable behavior of the main valve occurred when the pilot valve was stable. This paper considers inherent stability of the main valve in the gas flow. CFD software ANSYS FLUENT is employed to study the effect of the poppet geometry on aerodynamic lifting force and valve stability in axial and lateral direction. The results have been verified through comparison with experimental data.
Modelling and Experimental Validation of the Effective Bulk Modulus of a Mixture of Hydraulic Oil and Air
Authors: Gholizadeh Hossein , Bitner Doug , Burton Richard , Schoenau Greg
Published: February 2014

It is well known that the presence of entrained air bubbles in hydraulic oil can significantly reduce the effective bulk modulus of hydraulic oil. The effective bulk modulus of a mixture of oil and air as pressure changes is considerably different than when the oil and air is not mixed. Theoretical models have been proposed in the literature to simulate the pressure sensitivity of the effective bulk modulus of this mixture. However, limited amounts of experimental data are available to prove the validity of the models under various operating conditions. The major factors that affect pressure sensitivity of the effective bulk modulus of the mixture are the amount of air bubbles, their size and the distribution and rate of compression of the mixture. An experimental apparatus was designed to investigate the effect of these variables on the effective bulk modulus of the mixture. The experimental results were compared with existing theoretical models and it was found that the theoretical models only matched the experimental data under specific conditions. The purpose of this paper is to specify the conditions in which the current theoretical models can be used to represent the real behavior of the pressure sensitivity of the effective bulk modulus of the mixture. Additionally, a new theoretical model is proposed for situations where the current models fail to truly represent the experimental data.
Thermodynamic Considerations for Advanced, High Efficiency IC Engines
Authors: Caton Jerald A.
Published: February 2014

Thermodynamics is the key discipline for determining and quantifying the elements of advanced engine designs which lead to high efficiency. In spite of its importance, thermodynamics is often not given full consideration in understanding engine operation for high efficiency. By fully utilizing the first and second laws of thermodynamics, detailed understanding of the engine features that provide for high efficiency may be determined. Of all the possible features that contribute to high efficiency, the results of this study show that highly diluted engines with high compression ratios provide the greatest impact for high efficiencies. Other important improvements which increase the efficiency include reduced heat losses, optimal combustion phasing, reduced friction, and reduced combustion duration. Thermodynamic quantification of these concepts is provided. For one comparison, the brake thermal efficiency increased from about 34% for the conventional engine to about 48% for the engine with one set of the above features. One aspect that contributes to these improvements is the importance of the ratio of specific heats (“gamma”). In addition, these design features often result in low emissions due to the low combustion temperatures.
Design and Analysis of a Lightweight Polygon Engine
Authors: Clark Adam N. , Anderson Kevin R. , Stover Clifford M. , Cunningham Stephen L. , Stuart Martin
Published: February 2014

Current trends in engine design have pushed the state-of-the-art regarding high power-to-weight ratio gasoline engines. Newly developed engine systems have a power to weight ratio near 1 hp per pound. The engine configuration presented herein makes it possible to package a large number of power producing pistons in a small volume resulting in a power to weight ratio near 2 hp per pound, which have never before been realized in a production engine. The analysis and design of a lightweight, two-stroke, 6 side, in-plane, polygon engine having a geometric compression ratio of 15.0, actual compression ratio of 8.8 and piston speed of 3500 ft/min are presented in this investigation. Power output, kinematic modeling, and weight estimates are presented.
Predicting the Physical and Chemical Ignition Delays in a Military Diesel Engine Running n-Hexadecane Fuel
Authors: Hamilton Len , Cowart Jim , Luning Prak Dianne
Published: February 2014

There are currently numerous efforts to create renewable fuels that have similar properties to conventional diesel fuels. One major future challenge is evaluating how these new fuels will function in older legacy diesel engines. It is desired to have physically based modeling tools that will predict new fuel performance without extensive full scale engine testing. This study evaluates two modeling tools that are used together to predict ignition delay in a military diesel engine running n-hexadecane as a fuel across the engine’s speed-load range. AVL-FIRE® is used to predict the physical delay of the fuel from the start of injection until the formation of a combustible mixture. Then a detailed LLNL chemical kinetic mechanism is used to predict the chemical ignition delay. This total model predicted ignition delay is then compared to the experimental engine data. The combined model predicted results show good agreement to that of the experimental data across the engine operating range with the chemical delay being a larger fraction of the total ignition delay. This study shows that predictive tools have the potential to evaluate new fuel combustion performance.
Development of a High-Pressure, High-Temperature, Optically Accessible Continuous-Flow Vessel for Fuel-Injection Experiments
Authors: James Kemar C. , Wang Jin , Morris Zackery B. , Maynard Michael C. , Fisher Brian T.
Published: February 2014

The focus of this work was to develop a continuous-flow vessel with extensive optical access for characterization of engine-relevant fuel-injection and spray processes. The spray chamber was designed for non-reacting experiments at pressures up to 1380 kPa (200 psi) and temperatures up to 200°C. Continuous flow of inert “sweep gas” enables acquisition of large statistical data samples and thus potentially enables characterization of stochastic spray processes. A custom flange was designed to hold a common-rail diesel injector, with significant flexibility to accommodate other injectors and injector types in the future. This flexibility, combined with the continuous flow through the chamber, may enable studies of gas-turbine direct-injection spray processes in the future. Overall, the user can control and vary: injection duration, injection pressure, sweep-gas temperature, sweep-gas pressure, and sweep-gas flow rate. The user also can control frequency of replicate injections.

There are four flat windows installed orthogonally on the vessel for optical access. Optical data, at present, include global spray properties such as liquid-phase fuel penetration and cone angle. These measurements are made using a high-speed spray-visualization system (up to 100 kHz) consisting of a fast-pulsed LED (light emitting diode) source and a high-speed camera. Experimental control and data acquisition have been set up and synchronized using custom LabVIEW programs. The culmination of this development effort was an initial demonstration experiment to capture high-speed spray-visualization movies of n-heptane injections to determine liquid-phase fuel penetration length (i.e., liquid length) and spray cone angle. In this initial experiment, fuel-injection pressure was ∼120 MPa (1200 bar) and the injection command-pulse duration was 800 μs. At room conditions, liquid length and nominal spray cone angle were ∼170 mm and ∼14.5°, respectively. In contrast, with air flow in the chamber at 100 psi and 100°C, liquid length was considerably shorter at ∼92 mm and spray cone angle was wider at ∼16.5°. Future experiments will include the continuation of these measurements for a wider range of conditions and fuels, extension of high-speed imaging to vapor-phase fuel penetration using schlieren imaging techniques, and detailed characterization of spray properties near the injector nozzle and near the liquid length.
Analysis of the Influence of Pilot Injection Timing on Diesel Combustion in an Optical Engine by the Two-Color Method
Authors: Zeng Weilin , He Xu , Jin Senjia , Liu Hai , Li Xiangrong , Liu Fushui
Published: February 2014

High-speed photography, two-color method, and thermodynamic analysis have been used to improve understanding of the influence of pilot injection timing on diesel combustion in an optical engine equipped with an electronically-controlled, common rail, high-pressure fuel injection system. The tests were performed at four different pilot injection timings (30 degree, 25 degree, 20 degree, and 15 degree CA BTDC) with the same main injection timing (5 degree CA BTDC), and under 100MPa injection pressure. The engine speed was selected at 1200 rev/min, and the whole injection mass was fixed as 27.4 mg/stroke. The experimental results showed that the pilot injection timing had a strong influence on ignition delay and combustion duration: advancing the pilot injection timing turned to prolong the ignition delay and shorten the combustion duration. The combustion images indicated that when pilot injection was advanced, the area of luminous flames decreased. The results of two-color method suggested pilot injection timing significantly impacted both the soot temperature distribution and soot concentration (KL factor) within the combustion chamber. 30 degree CA BTDC was the optimal pilot injection timing for in-cylinder soot reduction.
Integrated HCCI Engine Control Based on a Performance Index
Authors: Bidarvatan M. , Shahbakhti M.
Published: February 2014

Integrated control of HCCI combustion phasing, load, and exhaust aftertreatment system is essential for realizing high efficiency HCCI engines, while maintaining low HC and CO emissions. This paper introduces a new approach for integrated HCCI engine control by defining a novel performance index to characterize different HCCI operating regions. The experimental data from a single cylinder engine at 214 operating conditions is used to determine the performance index for a blended fuel HCCI engine. The new performance index is then used to design an optimum reference trajectory for a multi-input multi-output HCCI controller. The optimum trajectory is designed for control of combustion phasing and IMEP, while meeting catalyst light-off requirements for the exhaust aftertreatment system. The designed controller is tested on a previously validated physical HCCI engine model. The simulation results illustrate the successful application of the new approach for controller design of HCCI engines.
Analysis of Aluminum and Steel Pistons: Comparison of Friction, Piston Temperature, and Combustion
Authors: Schreer Kai , Roth Ingo , Schneider Simon , Ehnis Holger
Published: February 2014

While steel pistons have been in use for a long time in commercial vehicle diesel engines, the first series production applications for passenger car diesel engines are currently imminent. The main reason for the use of steel pistons in high speed diesel engines is not, as maybe initially hypothesized, the increasing requirements on the component strength due to increasing mechanical loads, but rather challenges based on the actual CO2-legislation. The increasing requirements to reduce the fuel consumption necessitate new innovative technologies. The imminent penalties for exceeding the prescribed CO2 emissions seem to make the steel piston a viable alternative today, despite its higher manufacturing costs. So far, the CO2-benefits using steel pistons were mainly ascribed to the reduced friction between piston and cylinder liner due to no thermal interference.

Fuel consumption measurements at vehicle manufacturer and research institutes hypothesize also an influence of the steel piston on the thermodynamic efficiency. MAHLE uses engine tests to investigate one piston variant made of aluminum (series production piston with cooled ring carrier) and one of steel (MAHLE TopWeld) in a detailed system comparison. Using a fully indicated engine, a combustion process analysis is performed and used as the basis for a loss analysis. The engine set-up parameters can be adjusted fully variable using a flexible ECU. The effect that the piston variant has on the combustion process is captured and balanced, e.g., by adjusting the parameters to obtain identical emissions. The analysis records the potential of the variants for each engine operating map area. The thermal conditions for the piston and the piston wall temperature on the combustion chamber side are varied over a wide range using a conditioning device for piston cooling. The influence of this intervention on the thermal load of the piston and the combustion and also the influence of different combustion mappings is measured directly by telemetric piston temperature measurement. MAHLE recently completed a system comparison [3] between aluminum and steel pistons with detailed measurements on a fully indicated engine, covering friction and temperature behavior as well as influences on combustion.
Analysis and Modelling of the Transient Thermal Behaviour of Automotive Turbochargers
Authors: Burke Richard D.
Published: February 2014

Turbochargers are a key technology to deliver fuel consumption reductions on future internal combustion engines. However, the current industry standard modeling approaches assume the turbine and compressor operate under adiabatic conditions. Although some state of the art modeling approaches have been presented for simulating the thermal behavior, these have focused on thermally stable conditions. In this work, an instrumented turbocharger was operated on a 2.2L Diesel engine and in parallel a one-dimensional lumped capacity thermal model was developed. For the first time this paper presents analysis of experimental and modeling results under dynamic engine operating conditions.

Engine speed and load conditions were varied to induce thermal transients with turbine inlet temperatures ranging from 200–800°C; warm-up behavior from 25°C ambient was also studied. Following a model tuning process based on steady operating conditions, the model was used to predict turbine and compressor gas outlet temperatures, doing so with an RMSE of 8.4°C and 7.1°C respectively. On the turbine side, peak heat losses from the exhaust gases were observed to be up to double those observed under thermally stable conditions due to the heat accumulation in the structure. During warm-up, the model simplifications did not allow for accurate modeling of compressor, however on the turbine side gas temperature predictions errors were reduced from 150°C to around 40°C. The main benefits from the present modeling approach appear to be in turbine outlet temperature prediction, however modeling improvements are identified for future work.
Compression of a Swirling and Tumbling Flow
Authors: Söder Martin , Prahl Wittberg Lisa , Lindgren Björn , Fuchs Laszlo
Published: February 2014

The effect of compression on a swirling/tumbling flow is studied using Large-Eddy Simulations (LES). In this study the geometry investigated is a cylinder with an artificially created swirling/tumbling motion. During compression the evolution of turbulence and vorticity are investigated. An increase of turbulence and vorticity is observed and linked to vorticity-dilatation interaction. It is shown that for swirling/tumbling flows turbulent kinetic energy available at Top Dead Center (TDC) is introduced by the piston through the vorticity-dilatation interaction and that turbulence increases independently of the presence of instability of the large scale flow structures.
Automatic Combustion Phase Calibration With Extremum Seeking Approach
Authors: Corti Enrico , Mancini Giorgio , Forte Claudio , Moro Davide
Published: February 2014

Combustion control is assuming a crucial role in reducing engine tailpipe emissions and maximizing performance. The number of actuations influencing the combustion is increasing, and, as a consequence, the calibration of control parameters is becoming challenging. One of the most effective factors influencing performance and efficiency is the combustion phasing: for gasoline engines control variables such as Spark Advance (SA), Air-to-Fuel Ratio (AFR), Variable Valve Timing (VVT), Exhaust Gas Recirculation (EGR) are mostly used to set the combustion phasing.

The optimal control setting can be chosen according to a target function (cost or merit function), taking into account performance indicators, such as Indicated Mean Effective Pressure (IMEP), Brake Specific Fuel Consumption (BSFC), pollutant emissions, or other indexes inherent to reliability issues, such as exhaust gas temperature, or knock intensity.

Many different approaches can be used to reach the best calibration settings: Design Of Experiment (DOE) is a common option when many parameters influence the results, but other methodologies are in use: some of them are based on the knowledge of the controlled system behavior, by means of models that are identified during the calibration process.

The paper proposes the use of a different concept, based on the extremum seeking approach. The main idea consists in changing the values of each control parameter at the same time, identifying its effect on the monitored target function, allowing to shift automatically the control setting towards the optimum solution throughout the calibration procedure. An original technique for the recognition of control parameters variations effect on the target function is introduced, based on spectral analysis.

The methodology has been applied to data referring to different engines and operating conditions, using IMEP, exhaust temperature and knock intensity for the definition of the target function, and using SA and AFR as control variables. The approach proved to be efficient in reaching the optimum control setting, showing that the optimal setting can be achieved rapidly and consistently.
Virtual Design of an Industrial, Large-Bore, Spark-Ignited, Natural Gas, Internal Combustion Engine for Reduction of Regulated Pollutant Emissions
Authors: Etcheverry John , Patterson Mark , Grauer Diana
Published: February 2014

The natural gas industry has long depended on large bore, two-stroke cycle, spark-ignited, gas-powered, reciprocating engines to move gas from the well to the pipeline and downstream. As regulations governing the pollutant emissions from these engines are tightened the industry is turning to the engine OEMs for a solution.

The challenge of further reducing engine emissions is not a new task to the industry. However, as the requirements placed on the engines are further restricted, the technology required to achieve these goals becomes more advanced, along with the required tools and technology to create it. New predictive tools have been created and have become more powerful and capable as computer software and hardware becomes more advanced, enabling engineers to create more complex designs and to do so quickly and at lower cost, all of which may not have been possible previously. This paper investigates methods used in designing the Ajax 2800 series, which is a large bore, two-stroke cycle, gas-powered, reciprocating engine and the improvements in emissions that resulted from the application of these methods.. Solutions to overcoming the challenges encountered during the process will also be presented.
High Load (21bar IMEP) Dual Fuel RCCI Combustion Using Dual Direct Injection
Authors: Lim Jae Hyung , Reitz Rolf D.
Published: February 2014

Dual-fuel reactivity controlled compression ignition (RCCI) combustion has shown high thermal efficiency and superior controllability with low NOx and soot emissions. However, as in other low temperature (LTC) combustion strategies, the combustion control using low exhaust gas recirculation (EGR) or high compression ratio at high load conditions has been a challenge. The objective of this work was to examine the efficacy of using dual direct injectors for combustion phasing control of high load RCCI combustion. The present computational work demonstrates that 21bar gross indicated mean effective pressure (IMEP) RCCI is achievable using dual direct injection. The simulations were done using the KIVA3V-Release 2 code with a discrete multi-component fuel evaporation model, coupled with sparse analytical Jacobian solver for describing the chemistry of the two fuels (iso-octane and n-heptane). In order to identify an optimum injection strategy a Nondominated Sorting Genetic Algorithm II (NSGA II), which is a multi-objective genetic algorithm, was used. The goal of the optimization was to find injection timings and mass splits among the multiple injections that simultaneously minimize the six objectives: soot, nitrogen oxide (NOx), carbon monoxide (CO), unburned hydrocarbon (UHC), indicated specific fuel consumption (ISFC), and ringing intensity. The simulations were performed for a 2.44 liter, heavy-duty engine with 15:1 compression ratio. The speed was 1800 rev/min and the intake valve closure (IVC) conditions were maintained at 3.42bar, 90°C, and 46% EGR. The resulting optimum condition has 12.6bar/deg peak pressure rise rate, 158bar maximum pressure, and 48.7% gross indicated thermal efficiency. NOx, CO, and soot emissions are very low.
A Study on Measurement of Conformability of the Piston Oil Ring on the Cylinder Bore Under Engine Operating Condition by LIF Method Using Optical Fiber
Authors: Ito Akemi , Mochiduki Kazuya , Kikuhara Koji , Inui Masatsugu , Akamatsu Hirotaka
Published: February 2014

Engine oil consumption must be reduced for reducing exhaust gas emissions. It is well known that a cylinder bore shape under engine operating condition affects oil consumption. This study aimed clarifying the conformability of an oil ring against the distorted cylinder bore. Oil film thickness at the sliding surface of oil ring upper and lower rails was successfully measured by LIF method using optical fiber, which was embedded in the oil ring. The piston motion was also measured and compared with measured oil film thickness. It was found that the piston tilting motion affected oil film thickness hence its conformability. It was also found that thicker oil film was found at the following rail than that at former rail, and it was suggested that oil was supplied to the following rail from not only the sliding surface of the former ring but also somewhere, for example, the oil ring groove.