bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced in vitro approach to study neurovascular coupling mechanisms in the brain microcirculation
Authors: Kim Ki Jung , Filosa Jessica A.
Published: February 2012

Key points 

We show that parenchymal arterioles of less than 30 μm in diameter can be successfully cannulated and perfused in cortical and hypothalamic brain slices.

Increased flow/pressure induced parenchymal arteriolar constriction.

Alternatively to video microscopy, diameter measurements of cannulated arterioles could be obtained from perfusion velocity values obtained using fluorescence recovery after photobleaching.

Perfused and pressurized parenchymal arterioles responded with dilatation to two well‐established signals in neurovascular coupling, K+ (10 mM) and activation of metabotropic glutamate receptors (mGluRs).
Synthetic localized calcium transients directly probe signalling mechanisms in skeletal muscle
Authors: Figueroa Lourdes , Shkryl Vyacheslav M. , Zhou Jingsong , Manno Carlo , Momotake Atsuya , Brum Gustavo , Blatter Lothar A. , Ellis‐Davies Graham C. R. , Ríos Eduardo
Published: February 2012

Key points 

The signal for skeletal muscle contraction is a rapid increase in cytosolic Ca2+ concentration, which requires the coordinated opening of ryanodine receptor (RyR) channels in the sarcoplasmic reticulum.

Channel opening is controlled by voltage‐sensing dihydropyridine receptors (DHPRs) of plasma membrane and T tubules. Whether or not their signal is amplified by Ca2+‐induced Ca2+ release (CICR) is controversial.

We used two‐photon lysis of an advanced Ca2+ cage to produce local Ca2+ concentration transients that were large, fast, reproducible and quantifiable, while monitoring the cellular response with a dual confocal laser scanner.

Single frog muscle cells in physiological solutions responded to transients greater than 0.28 μm with propagated CICR waves.

Mouse cells did not respond to stimuli up to 8 μm, unless channel opening drugs were present.

We conclude that CICR contributes to physiological Ca2+ release in frog but not mouse muscle.

Mice and presumably other mammals do have a capability for CICR that is normally inhibited. It could be manifested under special circumstances, including diseases.
A Sequential Sampling Strategy to Improve Reliability-Based Design Optimization With Implicit Constraint Functions
Authors: Zhuang Xiaotian , Pan Rong
Published: February 2012

Reliability-based design optimization (RBDO) has a probabilistic constraint that is used for evaluating the reliability or safety of the system. In modern engineering design, this task is often performed by a computer simulation tool such as finite element method (FEM). This type of computer simulation or computer experiment can be treated a black box, as its analytical function is implicit. This paper presents an efficient sampling strategy on learning the probabilistic constraint function under the design optimization framework. The method is a sequential experimentation around the approximate most probable point (MPP) at each step of optimization process. Our method is compared with the methods of MPP-based sampling, lifted surrogate function, and nonsequential random sampling. We demonstrate it through examples.
A Numerical Contour Method for Simulating Spiral Groove Bottom Profiles
Authors: Wu Weifeng , Sun Shuo , Feng Quanke
Published: February 2012

The envelope method can be used to model the spiral groove surface profile in single screw compressors produced by cylindrical milling using the contact lines of the cutter surface and the groove. However, the envelope method cannot predict the groove bottom profile accurately because it does not account for the boundary contact lines on the end face of the cutter. A new numerical contour method is proposed to model the groove bottom profile by identifying the contact points on the end face of the cutter to a set position on the spiral groove. Results show that the new method can calculate accurately both the boundary and the inner contact line and thus simulate the groove bottom profile exactly. This method could also be used to simulate other profiles of machines, such as rotor profiles of twin screw compressors and screw pumps.
Combustion Analysis and Study on Smoke and NOX Emissions of Diesel and Biodiesel Fueled CI Engines With Ethanol Blends
Authors: Iranmanesh Masoud
Published: February 2012

Diesel engines suffer from high amount of soot, particulate matter and nitrogen oxides emissions in spite of their advantages such as high thermal efficiency, low CO and HC emissions. The use of Biodiesel in conventional diesel engines results in a substantial reduction of HC, CO and PM. Its higher cetane number improves the ignition quality. However it suffers from cold starting problems and increased NOx emissions when compared with diesel fuel. Reduction of NOx emissions and particulate matter simultaneously is quite difficult due to the Soot/NOx trade off. In this investigation, tests were conducted on a single cylinder DI diesel engine fueled with neat diesel and biodiesel as baseline fuel and addition of 5 to 20% ethanol on a volume basis in steps of 5 vol.% as a bio-resource supplementary oxygenated fuel to analyze the combustion and emissions characteristics. The results have shown a simultaneous reduction of NOx and smoke emissions in comparison with baseline fuels. A global overview of the results has shown that the 15% ethanol addition to diesel and biodiesel fuel produce the lowest smoke opacity. Meanwhile the lowest amount of NOX emissions belongs to the 10% and 15% ethanol addition to diesel and biodiesel respectively.
Characterizing Diesel Fuel Spray Cone Angle From Back-Scattered Imaging by Fitting Gaussian Profiles to Radial Spray Intensity Distributions
Authors: Nesbitt Jaclyn E. , Naber Jeffrey D. , Lee Seong-Young
Published: February 2012

Quantifying fuel spray properties including penetration, cone angle, and vaporization processes sheds light on fuel-air mixing phenomenon which governs subsequent combustion and emissions formation in diesel engines. Accurate experimental determination of these spray properties is a challenge but imperative to validate computational fluid dynamic (CFD) models for combustion prediction. This study proposes a new threshold independent method for determination of spray cone angle when using Mie back-scattering optical diagnostics to visualize diesel sprays in an optically accessible constant volume vessel. Test conditions include the influence of charge density (17.6 and 34.9 kg/m3) at 1990 bar injection pressure, and the influence of injection pressure (990, 1370, and 1980 bar) at a charge density of 34.8 kg/m3 on diesel fuel spray formation from a multi-hole injector into nitrogen at a temperature of 100°C. Conventional thresholding to convert an image to black and white for processing and determination of cone angle is threshold subjective. As an alternative, an image processing method was developed which fits a Gaussian curve to the intensity distribution of the spray at radial spray cross-sections and uses the resulting parameters to define the spray edge and hence cone angle. This Gaussian curve fitting methodology is shown to provide a robust method for cone angle determination, accounting for reductions in intensity at the radial spray edge. Results are presented for non-vaporizing sprays using this Gaussian curve fitting method and compared to the conventional thresholding based method.
Analysis of Tribological Performance of Piston Ring Lubrication
Authors: Guo Yibin , Li Wanyou , Zou Dequan , Lu Xiqun , He Tao
Published: February 2012

In this paper a mixed lubrication model considering lubricant supply conditions on cylinder bore has been developed for the piston ring lubrication. The numerical procedures of both fully flooded and starved lubrication were included in the model. The lubrication equations and boundary conditions at the end of strokes were discussed in detail. The effects of piston ring design parameters, such as ring face profile and ring tension, on oil film thickness, friction force and power loss under fully flooded and starved lubrication conditions due to available lubricant supply on cylinder bore were studied. The simulation results show that the oil available in the inlet region of the oil film is important to the piston ring friction power loss. With different ring face crown heights and tensions, the changes of oil film thickness and friction force were apparent under fully flooded lubrication, but almost no changes were found under starved lubrication except at the end of a stroke. In addition, the oil film thickness and friction force were affected evidently by the ring face profile offsets under both fully flooded and starved lubrication conditions, and the offset towards the combustion chamber made a large contribution to forming thicker oil film during the expansion stroke. So under different lubricant supply conditions on the cylinder bore, the ring profile and tension need to be adjusted to reduce the friction and power loss. Moreover, the effects of lubricant viscosity, surface composite roughness, and engine operating speed on friction force and power loss were also discussed.
Advanced Model of Bi-Component Fuel Droplet Heating and Evaporating With Liquid Turbulence Effects at High Pressure
Authors: Abianeh Omid Samimi , Chen C. P.
Published: February 2012

A new approach to account for finite thermal conductivity, finite mass diffusivity and turbulence effects within atomizing liquid sprays at high pressure condition is presented in this paper. The finite conductivity model is based on a newly developed two-layer film theory, where the turbulence characteristics of the droplet are used to estimate the effective thermal conductivity [1]. The present paper extends the formulation to model the multi-component mass diffusivities within the droplet phase at high pressures but less than components critical pressures. An approximate solution to the quasi-steady energy equation was used to derive an explicit expression for the heat flux from the surrounding gas to the droplet–gas interface, with inter-diffusion of fuel vapor and the surrounding gas taken into account. The Peng-Robinson equation of state (EOS) is used for extension of the model to the high pressures. The latent heat of vaporization and fuel enthalpies are also corrected for high pressure. The model includes the non-ideal gas and liquid behavior, and variable thermo-transport properties including their dependence on pressure and temperature. For this study a mixture of decane and hexadecane fuel droplet was considered. Predictions of the high-pressure single droplet model are in good agreement with the available data in literature.
Simulating Flame Lift-Off Characteristics of Diesel and Biodiesel Fuels Using Detailed Chemical-Kinetic Mechanisms and LES Turbulence Model
Authors: Som Sibendu , Longman Douglas E. , Luo Zhaoyu , Plomer Max , Lu Tianfeng , Senecal Peter K. , Pomraning Eric
Published: February 2012

Combustion in direct-injection diesel engines occurs in a lifted, turbulent diffusion flame mode. Numerous studies indicate that the combustion and emissions in such engines are strongly influenced by the lifted flame characteristics, which are in turn determined by fuel and air mixing in the upstream region of the lifted flame, and consequently by the liquid breakup and spray development processes. From a numerical standpoint, these spray combustion processes depend heavily on the choice of underlying spray, combustion, and turbulence models. The present numerical study investigates the influence of different chemical kinetic mechanisms for diesel and biodiesel fuels, as well as Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) turbulence models on predicting flame lift-off lengths (LOLs) and ignition delays. Specifically, two chemical kinetic mechanisms for n-heptane (NHPT) and three for biodiesel surrogates are investigated. In addition, the RNG k-ε (RANS) model is compared to the Smagorinsky based LES turbulence model. Using adaptive grid resolution, minimum grid sizes of 250 μm and 125 μm were obtained for the RANS and LES cases respectively. Validations of these models were performed against experimental data from Sandia National Laboratories in a constant volume combustion chamber. Ignition delay and flame lift-off validations were performed at different ambient temperature conditions. The LES model predicts lower ignition delays and qualitatively better flame structures compared to the RNG k-ε model. The use of realistic chemistry and a ternary surrogate mixture, which consists of methyl decanoate, methyl 9-decenoate, and NHPT, results in better predicted LOLs and ignition delays. For diesel fuel though, only marginal improvements are observed by using larger size mechanisms. However, these improved predictions come at a significant increase in computational cost.
Combustion Characteristics of Producer Gas in the Stationary Gas Engine
Authors: Kim Arnold M. , Smith James A. , Wagler Jayson R. , Baldwin Darryl D.
Published: February 2012

Three syngases were selected from customer sites and the engine performance test was conducted on a single cylinder test engine (SCTE) to explore the engine operating limits and investigate the combustion characteristics for the simulation model development. Syngas has a wide range of lambda between the misfire and the detonation compared to conventional natural gas. Combustion of syngas 1 having no CH4 showed unique characteristics which are different from syngas 3. It appears that even a small amount of CH4 in the fuel would be important to lower the rate of the main branching reaction of hydrogen and mitigate the explosive reaction of the hydrogen. Lean operating limit of the tested syngas was observed when LFS (Laminar Flame Speed) and AFT (Adiabatic Flame Temperature) become around 5∼7 cm/s and 1660 ∼ 1720°C.
JP-8 Combustion Characteristics in a Small Diesel Auxiliary Power Unit
Authors: Soloiu Valentin , Covington April , Lewis Jeffery , Welch Jonathan
Published: February 2012

The US Army Single Fuel Forward policy mandates that deployed vehicles must be operable with aviation fuel JP-8. Therefore, an investigation into the influence of JP-8 on a diesel engine’s performance is currently in progress. The injection, combustion, and performance of JP-8, 20–50% by weight in diesel no.2 mixtures (J20-J50) produced at room temperature were investigated in a 77mm indirect injection, high compression ratio (23.5) diesel engine, in order to evaluate its effectiveness for application in Auxiliary Power Units (APUs) at 2000rpm continuous operation (100% load/BMEP 4.78 bar). Due to the viscosity requirements for proper injection the new fuel can contain as high as 100% JP-8 (J100). The blends had an ignition delay of 1.03ms regardless of the amount of JP-8 introduced. J50 and diesel no.2 exhibited similar characteristics of heat release, the premixed phase being combined with the diffusion combustion. The maximum combustion pressure remained relatively constant for all blends, 72.7bar for diesel and decreased slightly by 0.40bar for J50, with the peak pressure position being delayed by 0.5CAD for the J50. The instantaneous volume-averaged gas combustion temperature reached 2162K for diesel versus 2173K for J50; displaying a 1.2CAD delay in the position of the maximum temperature and retaining the higher temperature for a longer duration for J50. The heat flux in the engine cylinder exhibited comparable maximum values for all blends (diesel: 2.12MW/m2, J50: 2.14MW/m2). The cylinder heat losses were at a minimum during combustion before TDC with increased convection losses at TDC for all fuels and the beginning of the power stroke. The heat losses associated with the system increased slightly with the addition of JP-8. The BSFC for diesel no.2 was 242(g/kW/hr) and increasing by only 0.7% for J50. The engine’s mechanical efficiency displayed similar values for all blends, 83% and decreasing by only 1% for J50. Taking into account each fuels’ corresponding density, the engine’s overall efficiency remained relatively constant at 29% with the addition of the JP-8. The engine investigation demonstrated that up to 50% JP-8 by weight in diesel can be injected and burnt in a small diesel engine with a combustion duration of approximately 5ms, while maintaining the engine overall efficiency. The study validates JP-8 as an excellent source for power generation in a diesel APU based on its combustion characteristics. The next stage of research shall be the full emissions investigation.
Particulate Matter Emissions From Late Injection High EGR Low Temperature Diesel Combustion
Authors: Tompkins Brandon T. , Song Hoseok , Jacobs Timothy J.
Published: February 2012

Low temperature combustion (LTC) is an advanced mode of combustion that has attained much attention due to ever increasing emission standards. LTC simultaneously reduces soot and nitric oxide (NO) emissions by having combustion take place at, for example bulk gas temperatures below 1200K (as observed in this study) so that soot and NO formation is substantially reduced. Soot is typically considered a building block for particulate matter (PM); both PM and NO are heavily regulated emissions by government agencies due to their potential effects on human and environmental health. Although LTC is believed to substantially reduce soot, it is not clear what is the end effect on PM. Because PM is composed of other agents, such as condensed liquid and solid hydrocarbons, there could potentially be non-negligible emission of PM from LTC combustion. This study will compare the gravimetric-based PM data from 3 different modes of combustion in a direct injection diesel engine; specifically: conventional combustion, combustion with high exhaust gas recirculation (EGR) at conventional injection timing, and combustion with high EGR and late injection timing (all other control parameters are the same, including fuel flow rate and engine speed). The objective of this study is to quantify PM emissions of LTC and assess potential differences relative to the soot concentration (the latter as assessed by a smokemeter). PM is gravimetrically measured using a mini-dilution tunnel. Further, chemical analysis of the collected PM is analyzed by an independent laboratory to develop an understanding of the constituent species composing conventional and LTC PM. PM results show that there are differences among the three modes of combustion. The PM differs in appearance as well as composition, and due to the change in appearance FSN may not correlate with PM when running LTC modes of combustion.
Detection of Combustion Resonance Using an Ion Current Sensor in Diesel Engines
Authors: Badawy Tamer , Shrestha Amit , Henein Naeim
Published: February 2012

This paper discusses the use of an ion current sensor to detect combustion resonance in a heavy duty direct injection diesel engine. A modified glow plug is used to measure the ion current in addition to its main function in warming up the combustion chamber. A comparison is made between the combustion resonance determined from the signals of an ion current sensor, a cylinder pressure transducer and an engine vibration sensor. Experiments are conducted on a four cylinder, turbo-charged 4.5L diesel engine to determine the potential of using the ion current sensor to detect combustion resonance under different injection pressures and exhaust gas recirculation rates. It is concluded that the ion current signal can be used to determine the timing, amplitude, frequency and duration of the resonance. The sensor output has the potential to be used as a feedback signal to the ECU (Electronic Control Unit) to minimize engine vibration and noise.
On the Relationship Between Fuel Injection Pressure and Two-Stage Ignition Behavior of Low Temperature Diesel Combustion
Authors: Bittle J. A. , Jacobs T. J.
Published: February 2012

In previous work, it is reported that increased dilution at mid-range injection pressures produces longer first stage combustion (cool-flame) duration. There is also corresponding decreases in nitric oxide concentrations and smoke number with respect to a reference conventional combustion mode. Continuing this effort, the objective of this study is to investigate the effect of injection pressure on the cool-flame duration under low temperature combustion conditions. A sweep of injection pressure is performed and the resulting heat release profiles are examined. The ignition delay behavior is expected based on changing injection pressure, but the cool-flame duration does not follow expected trends based on initial literature review. It is postulated that the influence of injection pressure on the local equivalence ratios is causing the observed behavior. The appropriate measurement and analysis tools are not available to the authors to confirm this postulation. A literature review of work investigating ignition conditions in low temperature combustion modes is used to support the postulation made in this study.
Knock Detection and Control in an HCCI Engine Using DWT
Authors: Mashkournia Masoud , Audet Adrian , Koch Charles Robert
Published: February 2012

The novel application of the Discrete Wavelet Transform (DWT) in a real time controller is used to detect and subsequently control knock in a Homogeneous Charge Compression Ignition (HCCI) engine. Classical Fourier techniques for knock detection are discussed and compared to Wavelet Transforms. The Discrete Wavelet Transform filter bank is chosen as the best method for knock detection due to its good time-resolution and low computational requirements. The DWT method is compared with the root mean squared value of the pressure trace as the benchmark method for determining knock and the two methods are linearly correlated. Using the DWT method for knock detection and modulating fuel octane, both a Proportional Integral (PI) and PI with Feed-forward control are implemented. Both of these methods reduce knock intensity for a step increase in engine load. The combination of Feed-forward with PI feedback is found to be slightly more effective than just PI feedback control.
Performance and Emissions Characteristics of Bio-Diesel (B100)-Ignited Methane and Propane Combustion in a Four Cylinder Turbocharged Compression Ignition Engine
Authors: Shoemaker N. T. , Gibson C. M. , Polk A. C. , Krishnan S. R. , Srinivasan K. K.
Published: February 2012

Different combustion strategies and fuel sources are needed to deal with increasing fuel efficiency demands and emission restrictions. One possible strategy is dual fueling using readily available resources. Propane and natural gas are readily available with the current infrastructure and biodiesel is growing in popularity as a renewable fuel. This paper presents experimental results from dual fuel combustion of methane (as a surrogate for natural gas) and propane as primary fuels with biodiesel pilots in a 1.9 liter, turbocharged, 4 cylinder diesel engine at 1800 rev/min. Experiments were performed with different percentage energy substitutions (PES) of propane and methane and at different brake mean effective pressures (BMEP/bmep). Brake thermal efficiency (BTE) and emissions (NOx, HC, CO, CO2, O2 and smoke) were also measured. Maximum PES levels for B100-methane dual fuelling were limited to 70% at 2.5 bar bmep and 48% at 10 bar bmep, and corresponding values for B100-propane dual fuelling were 64% and 43%, respectively. Maximum PES was limited by misfire at 2.5 bar bmep and the onset of engine knock at 10 bar bmep. Dual fuel BTEs approached straight B100 values at 10 bar bmep while they were significantly lower than B100 values at 2.5 bar bmep. In general dual fuelling was beneficial in reducing NOx and smoke emissions by 33% and 50%, respectively from baseline B100 levels; however, both CO and THC emissions were significantly higher than baseline B100 levels at all PES and loads.
Evaluation of Mass Flow Rate Distribution in Diesel Fuel Spray by L2F
Authors: Komada Keisuke , Kawaharada Noritsune , Sakaguchi Daisaku , Ueki Hironobu , Ishida Masahiro
Published: February 2012

A laser 2-focus velocimeter (L2F) has been applied for measurements of velocity and size of droplets of diesel spray and an evaluation method of mass flow rate has been proposed. The L2F has a micro-scale probe which consists of two foci. The distance between two foci is 17μm. The data acquisition rate of the L2F has been increased to 15MHz in order to capture every droplet which appears in the measurement volume. The diesel fuel spray injected intermittently into the atmosphere was investigated. The orifice diameter of the injector nozzle was 0.113mm. The injection pressure was set at 40MPa by using a common rail system. Measurements were conducted on ten planes 5 to 25mm downstream from the nozzle exit. It was clearly shown that the velocity of droplet was the highest at the spray center. The size of droplet at the spray center decreased downstream within 15mm from the nozzle exit. The mass flow rate near the spray center was found to be larger than that in the spray periphery region. It was confirmed that the fuel mass per injection evaluated by the proposed method based on the L2F measurement was near to the injected mass in a plane further than 15mm from the nozzle exit. However, fuel mass was underestimated in a plane closer to the nozzle exit. The probability density of infinitesimal distance between surfaces of adjacent droplets increased remarkably near the spray center 5 and 12mm downstream from the nozzle exit. As infinitesimal distance can be thought as an indicator of a highly dense region, it is understood that underestimation of fuel mass near the nozzle exit is due to the highly dense region. The diameter of the region, where the highly dense region was observed, was estimated as an order of 0.2mm in a plane 5mm downstream from the nozzle.
Real-Time Measurements of Engine-Out Trace Elements: Application of a Novel Soot Particle Aerosol Mass Spectrometer for Emissions Characterization
Authors: Cross E. S. , Sappok A. , Fortner E. C. , Hunter J. F. , Jayne J. T. , Brooks W. A. , Onasch T. B. , Wong V. W. , Trimborn A. , Worsnop D. R. , Kroll J. H.
Published: February 2012

Lubricant-derived trace element emissions are the largest contributors to the accumulation of incombustible ash in diesel particulate filters (DPF), eventually leading to filter plugging and an increase in engine fuel consumption. Particulate trace element emissions also pose adverse health effects and are the focus of increasingly stringent air quality regulations. To date, the rates and physical and chemical properties of lubricant-derived additive emissions are not well characterized, largely due to the difficulties associated with conducting the measurements. This work investigated the potential for conducting real-time measurements of lubricant-derived particle emissions. The experiment used the Soot Particle Aerosol Mass Spectrometer (SP-AMS) developed by Aerodyne Research to measure the size, mass and composition of submicron particles in the exhaust. Results confirm the ability of the SP-AMS to measure engine-out emissions of calcium, zinc, magnesium, phosphorous, and sulfur. Further, emissions of previously difficult to detect elements, such as boron, and low-level engine wear metals, such as lead, were also measured. This paper provides an overview of the results obtained with the SP-AMS, and demonstrates the utility of applying real-time techniques to engine-out and tailpipe-out trace element emissions. The SP-AMS used in this study was developed for real-time characterization of refractory particles (i.e. black carbon or soot) in the ambient atmosphere. The instrument consists of an intra-cavity laser (1064 nm) for particle vaporization followed by electron impact ionization and ion detection via a time-of-flight mass spectrometer. Application of the SP-AMS for engine exhaust characterization followed a two-part approach: (1) measurement validation, and (2) measurement of engine-out exhaust. Measurement validation utilized a diesel burner with precise control of lubricant consumption. Results showed a good correlation between CJ-4 oil consumption and measured levels of lubricant-derived trace elements in the particle phase. Following measurement validation, the SP-AMS measured engine-out emissions from a medium-duty diesel engine, operated over a standard speed/load matrix. This work demonstrates the utility of state-of-the-art online techniques (such as the SP-AMS) to measure engine-out emissions, including trace species derived from lubricant additives. Results help optimize the combined engine-lubricant-aftertreatment system and provide a real-time characterization of emissions. As regulations become more stringent and emission controls more complex, advanced measurement techniques with high sensitivity and fast time response will become an increasingly important part of engine characterization studies.
Method for Translation of In-Use Fuel Consumption and NOX Emissions Between Different Heavy-Duty Vehicle Routes
Authors: Delgado Oscar F. , Clark Nigel N. , Thompson Gregory J.
Published: February 2012

Portable emissions measurement systems (PEMS) are used to perform in-use measurements for emissions inventory and regulatory applications. PEMS data represent real world conditions more accurately than chassis dynamometer or engine dynamometer testing, arguably being the most realistic method of determining exhaust emissions over a certain driving route. However, measured emissions and fuel consumption depend strongly on both the route followed and the traffic situation that the vehicle encounters. A tool for translation of emissions and fuel consumption between diverse types of vehicle activity is required. The purpose of this paper is to assess the possibility of using route-averaged properties (kinematic parameters) for translation of fuel consumption and NOx emissions for a set of eighteen heavy-duty vehicles operating over up to eight different driving routes. A linear model developed for heavy-duty vehicle chassis dynamometer data modeling has been extended to in-use heavy-duty vehicle data. Two approaches were implemented; the first approach mimicked the prior chassis dynamometer work by incorporating average vehicle speed and average positive acceleration and the second approach incorporated road grade in a characteristic power parameter. The end result is a simple method which was shown to be accurate for estimation of fuel consumption (within 5% relative error) and NOx emissions (within 12% relative error) for over-the-road vehicles over “unseen” roads or traffic situations, without the need to perform additional over-the-road tests.
Speciation Analysis of Light Hydrocarbons and Hydrogen Production During Diesel Low Temperature Combustion
Authors: Asad Usman , Mendoza Arturo , Xie Kelvin , Jeftic Marko , Wang Meiping , Zheng Ming
Published: February 2012

The simultaneous reduction in engine-out NOx and soot emissions with diesel low temperature combustion (LTC) is generally accompanied by high levels of hydrocarbon (THC) and carbon monoxide (CO) emissions in the exhaust. To achieve clean diesel combustion in terms of low regulated emissions (NOx, soot, THC, and CO), the exhaust combustibles must be dealt with the exhaust aftertreatment (typically a diesel oxidation catalyst). In this work, engine tests were performed to realize LTC on a single-cylinder common-rail diesel engine up to 12 bar IMEP. A single-shot fuel injection strategy was employed to push the diesel cycles into LTC with exhaust gas recirculation (EGR). The combustibles in the exhaust were generally found to increase with the LTC load and were observed to be a function of the overall equivalence ratio. A Fourier transform infrared (FTIR) spectroscopy analysis of light hydrocarbon emissions found methane to constitute a significant component of the hydrocarbon emissions under the tested LTC conditions. The relative fraction of individual species in the hydrocarbons also changed, indicating a richer combustion zone and a reduction in engine-out THC reactivity. The hydrogen production was found to correlate consistently with the CO emissions, largely independent of the boost pressure or engine load under the tested LTC conditions. This research intends to identify the major constituents of the THC emissions and highlight the possible impact on exhaust aftertreatment.
Transient Behaviour of Glow Plugs in Direct Injection Natural Gas Engines
Authors: Cheng Stewart Xu , Wallace James S.
Published: February 2012

Glow plugs are a possible ignition source for direct injected natural gas engines. This ignition assistance application is much different than the cold start assist function for which most glow plugs have been designed. In the cold start application, the glow plug is simply heating the air in the cylinder. In the cycle-by-cycle ignition assist application, the glow plug needs to achieve high surface temperatures at specific times in the engine cycle to provide a localized source of ignition. Whereas a simple lumped heat capacitance model is a satisfactory representation of the glow plug for the air heating situation, a much more complex situation exists for hot surface ignition. Simple measurements and theoretical analysis show that the thickness of the heat penetration layer is small within the time scale of the ignition preparation period (1–2 ms). The experiments and analysis were used to develop a discretized representation of the glow plug domain. A simplified heat transfer model, incorporating both convection and radiation losses, was developed for the discretized representation to compute heat transfer to and from the surrounding gas. A scheme for coupling the glow plug model to the surrounding gas computational domain in KIVA-3V was also developed. The glow plug model successfully simulates the natural gas ignition process for a direct injection natural gas engine. As well, it can provide detailed information on the local glow plug surface temperature distribution, which can aid in the design of more reliable glow plugs.
Effect of Injection Parameters and Strategy on the Noise From a Single Cylinder Direct Injection Diesel Engine
Authors: Khaira Sukhbir Singh , Singh Amandeep , Jansons Marcis
Published: February 2012

Acoustic noise emitted by a diesel engine generally exceeds that produced by its spark-ignited equivalent and may hinder the acceptance of this more efficient engine type in the passenger car market (1). This work characterizes the combustion noise from a single-cylinder direct-injection diesel engine and examines the degree to which it may be minimized by optimal choice of injection parameters. The relative contribution of motoring, combustion and resonance components to overall engine noise are determined by decomposition of in-cylinder pressure traces over a range of load, injection pressure and start of injection. The frequency spectra of microphone signals recorded external to the engine are correlated with those of in-cylinder pressure traces. Short Time Fourier Transformation (STFT) is applied to cylinder pressure traces to reveal the occurrence of motoring, combustion noise and resonance in the frequency domain over the course of the engine cycle. Loudness is found to increase with enhanced resonance, in proportion to the rate of cylinder pressure rise and under conditions of high injection pressure, load and advanced injection timing.
The Effect of Piston Bowl and Spray Configuration on Diesel Combustion and Emissions
Authors: Ramadan Bassem H. , Gray Charles L. , Hamady Fakhri J. , Squibb Cody , Schock Harold J.
Published: February 2012

A numerical and experimental study of the effect of piston bowl and spray configuration on diesel combustion and emissions has been conducted. The objective of this study is to gain better understanding of the effect of the piston bowl shape and fuel injector configuration on fuel-air mixing, combustion, and emissions in a diesel engine. Ideally, a uniform fuel-air mixture in the cylinder is desired to prevent the formation of regions containing a rich mixture, where soot is usually formed, and regions of lean mixtures, where nitrogen oxides are formed. Different piston bowl shapes and fuel injectors (number of nozzles, spray angle) have been considered and simulated using computational fluid dynamics and experiments. CFD calculations of fuel mass fraction, and measurements of cylinder pressure and emissions species are included. The results show that computer simulations coupled with experiments provide insight into the interactions between fluid flow, fuel-air mixing, combustion, and emissions.
Novel NOx Emission Reduction Technology for Diesel Marine Engines
Authors: Ayre Louise S. , Johnson Derek R. , Clark Nigel N. , England Jason A. , Atkinson Richard J. , McKain David L. , Ralston Bradley A. , Balon Thomas H. , Moynihan Paul J.
Published: February 2012

Emissions from diesel marine engines are significant contributors to the emissions inventories of commercial ports. Prior to 1998, these emissions were unregulated and current EPA regulations apply predominantly to new engines. Considering that the useful life of marine engines in work vessels, such as tugboats, may be 20 years or longer, retrofit emission reduction technologies are needed for these legacy engines. Oxides of nitrogen (NOx) have negative health and environmental impacts and are difficult to reduce substantially without aftertreatment. A scrubber system for NOx reduction was proposed; the presented research focuses on the verification of operating principles and the quantification of possible NOx reduction from this system. Major elements of the proposed scrubber system are exhaust heat exchangers, a catalyzed particulate filter (CPF), a diesel oxidation catalyst (DOC), and a packed bed wet scrubber. The system works on the principle of absorption of NOx species into water. The majority of engine-out NOx is in the form of nitric oxide (NO) which is relatively insoluble in water. A CPF and a DOC are utilized to convert up to 80% of the NO into nitrogen dioxide, NO2. NO2 and NO exist in equilibrium with N2O3 and N2O4, species of NOx that are highly soluble in water. The use of a CPF and DOC also reduces carbon monoxide, hydrocarbons, and particulate matter, reducing possible scrubber contamination. The scrubber liquor operates on a closed loop with zero discharge, its final composition is weak nitric acid; a byproduct of capturing the NOx. Research to support this design was conducted on a Mack E7 298 kW, 12 liter engine operating over 8 steady state points. Modal NOx absorption ranged from 4–66%. Cycle average NOx absorption ranged from 15–58%. It was concluded that NOx absorption varies with gas residence time, absorption surface area, temperature, and NOx concentration. Separately, a system was constructed and operated to convert the stored concentrated NOx into diatomic nitrogen, carbon dioxide, and water.
A CFD Study of the Effect of HCHO Addition on Autoignition and Combustion
Authors: Florea Radu , Zha Kan , Jansons Marcis , Taraza Dinu , Henein Naeim
Published: February 2012

Experimental and theoretical research [1] targeted towards the effect of formaldehyde on combustion has identified its OH-scavenging role and recent data suggests it plays an important role in combustion instability observed during engine cold-starting. This effect was further studied using a CFD approach and the kinetic inhibiting effect of formaldehyde on the combustion process has been found to be enhanced by thermal/diffusion effects.
Accurate Specific Fuel Consumption Measurement and its Application on Piston Friction Reduction for a Heavy-Duty Diesel Engine
Authors: Chen Yu , Deck Carol Lynn
Published: February 2012

In recent years the attention of the internal combustion engine industry has been on improving fuel economy. These changes not only decrease the amount of fuel used and improve the efficiency of the engine, but also save the end-user on fuel costs, reduce engine emissions, and aid in the achievement of future government fuel economy regulations. An approach to decreasing fuel consumption is through improvements to engine mechanical and thermal efficiency. MAHLE has developed a testing method to accurately measure engine specific fuel consumption (SFC). SFC is an indicator of engine efficiency, hence it is directly effected by a reduction in friction. Since changes in SFC are small, considerable precision was required to measure it. To achieve this high level of accuracy key engine parameters were controlled along with boundary parameters. This study utilized a firing heavy-duty diesel engine running on a dynamometer. Results are presented to depict the repeatability of the technique over speed and load.
Modeling of SCR NH3 Storage in the Presence of H2O
Authors: Smith Michael A. , Depcik Christopher D. , Hoard John W. , Bohac Stanislav V. , Assanis Dionissios N.
Published: February 2012

Diesel engines offer excellent fuel economy, but this comes at the expense of higher emissions of nitrogen oxides (NOx) and Particulate Matter (PM). To meet current emissions standards, diesel engines require aftertreatment devices. Concepts using combinations of catalysts are becoming more common in aftertreatment systems to reduce the cost and size of these aftertreatment systems. One combination is an LNT-SCR system where the LNT releases NH3 during a regeneration to be used by the SCR catalyst for further NOx reduction. This involves rich-lean cycling of the exhaust stream, which alters species concentrations in the exhaust. Most notably H2O and CO2 levels can vary from 4%–14% during lean-rich cycling. An investigation was performed using multiple Temperature Programmed Desorption (TPD) experiments to determine how H2O and CO2 affect NH3 storage capacity of an Fe-based zeolite SCR catalyst. It was determined that H2O and CO2 inhibit NH3 storage capacity of the SCR catalyst. This inhibition has shown a linear dependence on H2O and CO2 concentration at constant temperature. It was also determined that H2O is a much stronger inhibitor of NH3 storage capacity then CO2. Additional Temperature Programmed Desorption (TPD) experiments, were run where H2O and CO2 concentration (0%, 6%, and 10%) and the initial storage temperature (200°C, 250°C, 300°C, 350°C) were varied. Results suggest the addition of a reaction that creates competition for active sites on the catalyst between H2O and NH3. The additional reaction allows H2O and NH3 to be stored on open catalytic sites and has improved model accuracy by accounting for large changes in H2O, CO2, and temperature.
Simulation of the electron field emission characteristics of a flat panel x-ray source
Authors: Posada Chrystian M. , Castaño Carlos H. , Grant Edwin J. , Lee Hyoung K.
Published: February 2012

A distributed flat panel x ray source is designed as an alternative for medical and industrial imaging fields. The distributed x ray source corresponds to a two dimensional array of micro (93 μm) x ray cells similar in format to a field emission display. In this paper the field electron emission characteristics of a single micro x ray cell are presented. The field electron emission from a carbon-nanotube- (CNT-) based cold cathode is simulated using the particle-in-cell code oopic pro. The electron source is simulated as a triode structure, composed of an emitting cathode, extracting grid and anode. The possibility of using focusing lenses to control the trajectory of emitted electrons is also evaluated. The layer of CNT emitters is modeled as Fowler–Nordheim emitters. The field emission characteristics were analyzed for extracting voltages between 20 and 70 V and accelerating voltages between 30 and 120 kV. Under these conditions, JFN-V curves, energy, and electron distributions at the anode surface were determined. Electron trajectories were determined as well. When no focusing structures were employed, electron trajectories were found to be divergent. When focusing lenses were included in the triode structure, the emitted electrons could be made to converge at the anode. In the cases where focusing structures were used, a dependency between the focal spot size and the extracting grid voltage was found. Results indicated an early feasibility of the proposed device to be employed as an electron source in the distributed flat panel x ray source.
The T788G Mutation in the
cyp51C
Gene Confers Voriconazole Resistance in Aspergillus flavus Causing Aspergillosis
Authors: Liu Wei , Sun Yi , Chen Wei , Liu Weixia , Wan Zhe , Bu Dingfang , Li Ruoyu
Published: February 2012

With voriconazole (VRC) being approved as the first choice in treating invasive aspergillosis (IA) and its increasing use in treatment, a VRC-resistant strain of
Aspergillus flavus
, the second leading cause of IA after
Aspergillus fumigatus
, has emerged. The VRC-resistant strain of
A. flavus
was isolated for the first time from the surgical lung specimen of an IA patient with no response to VRC therapy. In order to ascertain the mechanism of VRC resistance, the azole target enzyme genes in this strain of
A. flavus
were cloned and sequenced, and 4 mutations generating amino acid residue substitutions were found in the
cyp51C
gene. To further determine the role of this mutated gene for VRC resistance in
A. flavus
, an
Agrobacterium tumefaciens
-mediated gene replacement approach was applied. Consequently, the mutated
cyp51C
gene from this
A. flavus
strain was proven to confer the VRC resistance. Finally, to discern the one out of the four mutations in the
cyp51C
gene that is responsible for contributing to VRC resistance, a site-directed gene mutagenesis procedure combined with a gene replacement method was performed. As a result, the T788G missense mutation in the
cyp51C
gene was identified as responsible for VRC resistance in
A. flavus
. These findings indicated that the detection of this mutation in
A. flavus
could serve as an indicator for physicians to avoid the use of VRC during IA treatment. Further comprehensive surveillance for antifungal susceptibility, as well as intensive study on the mechanism of azole resistance in
A. flavus
causing IA, would be required to fully understand this mechanism.
Ajoene, a Sulfur-Rich Molecule from Garlic, Inhibits Genes Controlled by Quorum Sensing
Authors: Jakobsen Tim Holm , van Gennip Maria , Phipps Richard Kerry , Shanmugham Meenakshi Sundaram , Christensen Louise Dahl , Alhede Morten , Skindersoe Mette Eline , Rasmussen Thomas Bovbjerg , Friedrich Karlheinz , Uthe Friedrich , Jensen Peter Østrup , Moser Claus , Nielsen Kristian Fog , Eberl Leo , Larsen Thomas Ostenfeld , Tanner David , Høiby Niels , Bjarnsholt Thomas , Givskov Michael
Published: February 2012

In relation to emerging multiresistant bacteria, development of antimicrobials and new treatment strategies of infections should be expected to become a high-priority research area. Quorum sensing (QS), a communication system used by pathogenic bacteria likePseudomonas aeruginosato synchronize the expression of specific genes involved in pathogenicity, is a possible drug target. Previousin vitroandin vivostudies revealed a significant inhibition ofP. aeruginosaQS by crude garlic extract. By bioassay-guided fractionation of garlic extracts, we determined the primary QS inhibitor present in garlic to be ajoene, a sulfur-containing compound with potential as an antipathogenic drug. By comprehensivein vitroandin vivostudies, the effect of synthetic ajoene towardP. aeruginosawas elucidated. DNA microarray studies of ajoene-treatedP. aeruginosacultures revealed a concentration-dependent attenuation of a few but central QS-controlled virulence factors, including rhamnolipid. Furthermore, ajoene treatment ofin vitrobiofilms demonstrated a clear synergistic, antimicrobial effect with tobramycin on biofilm killing and a cease in lytic necrosis of polymorphonuclear leukocytes. Furthermore, in a mouse model of pulmonary infection, a significant clearing of infectingP. aeruginosawas detected in ajoene-treated mice compared to a nontreated control group. This study adds to the list of examples demonstrating the potential of QS-interfering compounds in the treatment of bacterial infections.