bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical and Experimental Investigations of Electromagnetic Field Enhancement Among Nanospheres With Varying Spacing
Authors: Han Li-Hsin , Wang Wei , Lu Yalin , Knize R. J. , Reinhardt Kitt , Howell John , Chen Shaochen
Published: January 2009

A modified Mie scattering theory was used to calculate the enhancement of electromagnetic (EM) field between gold nanospheres. The simulation result showed that the density of EM-energy in the space between neighboring nanospheres increases drastically as the interparticle space decreases. Simulated absorption-spectra also showed a peak-shifting from the visible to the infrared region when decreasing the nanosphere spacing. We used our previous experiment to verify the analytical results; the experiment was conducted by using a photodeformable microshell, which was coated with gold nanospheres. Made of photoshrinkable azobenzene polyelectrolytes, the microshells supported the gold nanospheres and gave the tunability of the interparticle spacing among the nanospheres. Upon irradiation of ultraviolet light, the microshells shrank and reduced the interparticle space. The absorption-spectra of the gradually shrinking microshells showed significant changes; a peak-broadening from the visible to the near-infrared region and a drastically enhanced water-absorption were observed in the experimental spectra. The experimental results confirmed the analytical analysis based on the modified scattering theory.
Microscale Transport Phenomena in Materials Processing
Authors: Jaluria Yogesh
Published: January 2009

Microscale transport mechanisms play a critical role in the thermal processing of materials because changes in the structure and characteristics of the material largely occur at these or smaller length scales. The heat transfer and fluid flow considerations determine the properties of the final product, such as in a crystal drawn from silicon melt or a gel from the chemical conversion of a biopolymer. Also, a wide variety of material fabrication processes, such as the manufacture of optical glass fiber for telecommunications, fabrication of thin films by chemical vapor deposition, and surface coating, involve microscale length scales due to the requirements on the devices and applications for which they are intended. For example, hollow fibers, which are used for sensors and power delivery, typically need fairly precise microscale wall thicknesses and hole diameters for satisfactory operation. The basic transport mechanisms underlying these processes are discussed in this review paper. The importance of material characterization in accurate modeling and experimentation is brought out, along with the coupling between the process and the resulting properties such as uniformity, concentricity, and diameter. Of particular interest are thermally induced defects and other imperfections that may arise due to the transport phenomena involved at these microscale levels. Additional aspects such as surface tension, stability, and free surface characteristics that affect the material processing at microscale dimensions are also discussed. Some of the important methods to treat these problems and challenges are presented. Characteristic numerical and experimental results are discussed for a few important areas. The implications of such results in improving practical systems and processes, including enhanced process feasibility and product quality, are also discussed.
Heat Transfer Predictions for Micro-/Nanochannels at the Atomistic Level Using Combined Molecular Dynamics and Monte Carlo Techniques
Authors: Nedea S. V. , Markvoort A. J. , van Steenhoven A. A. , Hilbers P. A. J.
Published: January 2009

The thermal behavior of a gas confined between two parallel walls is investigated. Wall effects such as hydrophobic or hydrophilic wall interactions are studied, and the effect on the heat flux and other characteristic parameters such as density and temperature is shown. For a dilute gas, the dependence on gas-wall interactions of the temperature profile between the walls for the incident and reflected molecules is obtained using molecular dynamics (MD). From these profiles, the effective accommodation coefficients for different interactions and different mass fluid/wall ratio are derived. We show that Monte Carlo (MC) with Maxwell boundary conditions based on the accommodation coefficient gives good results for heat flux predictions when compared with pure molecular dynamics simulations. We use these effective coefficients to compute the heat flux predictions for a dense gas using MD and MC with Maxwell-like boundary conditions.
Flow and Stability of Rivulets on Heated Surfaces With Topography
Authors: Gambaryan-Roisman Tatiana , Stephan Peter
Published: January 2009

Surfaces with topography promote rivulet flow patterns, which are characterized by a high cumulative length of contact lines. This property is very advantageous for evaporators and cooling devices, since the local evaporation rate in the vicinity of contact lines (microregion evaporation) is extremely high. The liquid flow in rivulets is subject to different kinds of instabilities, including the long-wave falling film instability (or the kinematic-wave instability), the capillary instability, and the thermocapillary instability. These instabilities may lead to the development of wavy flow patterns and to the rivulet rupture. We develop a model describing the hydrodynamics and heat transfer in flowing rivulets on surfaces with topography under the action of gravity, surface tension, and thermocapillarity. The contact line behavior is modeled using the disjoining pressure concept. The perfectly wetting case is described using the usual h−3 disjoining pressure. The partially wetting case is modeled using the integrated 6–12 Lennard-Jones potential. The developed model is used for investigating the effects of the surface topography, gravity, thermocapillarity, and the contact line behavior on the rivulet stability. We show that the long-wave thermocapillary instability may lead to splitting of the rivulet into droplets or into several rivulets, depending on the Marangoni number and on the rivulet geometry. The kinematic-wave instability may be completely suppressed in the case of the rivulet flow in a groove.
Semiconductor Thin Films Combined With Metallic Grating for Selective Improvement of Thermal Radiative Absorption/Emission
Authors: Fu C. J. , Tan W. C.
Published: January 2009

We propose in this work a structure of semiconductor thin films combined with a one-dimensional metallic grating, which allows for selective improvement of thermal radiative absorptivity (also emissivity) of the structure. Both shallow and deep gratings are considered in this work. Our numerical results obtained with a 2D rigorous coupled-wave analysis algorithm demonstrate that the proposed structure exhibits enhanced spectral absorptivity for photon energy slightly above the gap energy of the semiconductor (silicon in this work). Furthermore, the selectively improved absorptivity can be obtained in a wide range of incidence angles. As such, much smaller thickness of the semiconductor layer is required to absorb the same amount of high energy photons than in a conventional Si-based photovoltaic device. In addition, absorptivity for low energy photons in the new structure is lower due to the smaller semiconductor layer thickness. Therefore, the new structure may have potential applications in energy conversion devices.
Optical Strain Measurement Techniques to Assist in Life Monitoring of Power Plant Components
Authors: Morris Andrew , Maharaj Chris , Kourmpetis Miltiadis , Dear Ian , Puri Amit , Dear John
Published: January 2009

Sensors for monitoring creep strain in high-pressure steam pipes and other power plant components are subjected to very demanding environmental and operational conditions. It is important that the sensors are of a rugged design and that measurement can be made that only relates to creep movements in power plant components. The E.ON UK auto-reference creep management and control (ARCMAC) optical strain gauges have been designed to have this capability. These optical strain gauges are installed across sections of welded steam pipe and other plant components in locations that provide the best monitoring points to reveal the early onset of failure processes. Reported in this paper are recent developments to improve optical creep strain measurement to achieve a 65 microstrain accuracy level with an error of less than 10%. Also reported are trials of combining optical strain gauges with digital image correlation (DIC) to obtain detailed information of the creep strain distribution around the gauges. The DIC data for known defect geometries have been validated with finite element analysis.
Leak Detection in a Pipeline Using Modified Line Volume Balance and Sequential Probability Tests
Authors: Di Blasi Martín , Muravchik Carlos
Published: January 2009

The use of statistical tools to improve the decision process within leak detection is becoming a common practice in the area of computer pipeline monitoring. Among these tools, the sequential probability ratio test is one of the most named techniques used by commercial leak detection systems (Zhang and Di Mauro, 1998, “Implementing a Reliable Leak Detection System on a Crude Oil Pipeline,” Advances in Pipeline Technology, Dubai, UAE). This decision mechanism is based on the comparison of the estimated probabilities of leak or no leak observed from the pipeline data. This paper proposes a leak detection system that uses a simplified statistical model for the pipeline operation, allowing a simple implementation in the pipeline control system (Di Blasi, M., 2004, “Detección y localización de fugas en sistemas de transporte de fluidos incompresibles,” MS thesis, Universidad Nacional de La Plata, Buenos Aires, Argentina). Applying real-time recursive linear regression to volume balance and average pipeline pressure signals, a statistically corrected volume balance signal with reduced variance is derived. Its average value is zero during normal operation whereas it equals the leak flow under a leak condition. Based on the corrected volume balance, differently configured sequential probability ratio tests are presented to extend the dynamic range of detectable leak flow. Simplified mathematical expressions are obtained for several system performance indices, such as spilled volume until detection, time to leak detection, minimum leak flow detected, etc. Theoretical results are compared with leak simulations on a real oil pipeline. A description of the system tested over a 500 km oil pipeline is included, showing some real data results.
Cyclic and Fatigue Behavior of the P355NL1 Steel Under Block Loading
Authors: Pereira Hélder F. S. G. , De Jesus Abílio M. P. , Ribeiro Alfredo S. , Fernandes António A.
Published: January 2009

Current fatigue analyses of metallic structures undergoing variable amplitude loading, including pressure vessels, are mostly based on linear cumulative damage concepts, as proposed by Palmgren and Miner. This type of analysis neglects any sequential effects of the loading history. Several studies have shown that linear cumulative damage theories can produce inconsistent fatigue life predictions. In this paper, both fatigue damage accumulation and cyclic elastoplastic behaviors of the P355NL1 steel are characterized using block loading fatigue tests. The loading is composed of blocks of constant strain-controlled amplitudes, applied according to two and multiple alternate blocks sequences. Also, loading composed by blocks of variable strain-controlled amplitudes are investigated. The block loading illustrates that fatigue damage evolves nonlinearly with the number of load cycles, as a function of the block strain amplitudes. These observations suggest a nonlinear damage accumulation rule with load sequential effects for the P355NL1 steel. However, the damage accumulation nonlinearity and load sequential effects are more evident for the two block loading rather than for multiple alternate block sequences, which suggests that the linear Palmgren–Miner rule tends to produce better results for more irregular loading histories. Some phenomenological interpretations for the observed trends are discussed under a fracture mechanics framework.
Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading
Authors: Pereira Hélder F.S.G , De Jesus Abílio M. P. , Ribeiro Alfredo S. , Fernandes António A.
Published: January 2009

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren–Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope stress-life curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as nonconservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two-block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely, R=0, R=0.15, and R=0.3. Also, constant amplitude fatigue data are generated for the investigated structural component. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels, and stress ratios. In particular, a clear load sequence effect is verified for the two-block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is nonlinear. This suggests an important effect of the stress ratio on fatigue damage accumulation.
Thermal Stress Distribution in Thick Wall Cylinder Under Thermal Shock
Authors: Yun Yingwei , Jang Il-Young , Tang Liqiang
Published: January 2009

This paper presented the stress distribution in a thick walled cylinder under thermal shock. Dirac function was introduced to model thermal shock. An analytical solution of the temperature field was obtained by Laplace transform. Based on the temperature solution, the thermal stress response of the thick walled cylinder was solved. The time dependent variations of the temperature field—thermal stress field—were discussed, and the effect of cylinder radius ratio on the problem was given. The exploration in this paper will lay a theoretical reference to further study on the decrease in fatigue damage of the superhigh pressure tubular reactor under thermal shock.
A Comparison of Two- and Three-Dimensional Fracture Assessments in the Presence of Residual Stresses
Authors: Lewis S. J. , Truman C. E. , Smith D. J.
Published: January 2009

The influence of various assumptions on the modeling of cleavage fracture in the presence of residual stresses was investigated. Analyses were undertaken for modified single edge notched bend specimens, manufactured from A533B ferritic steel. The influence of residual stress fields, introduced by a method of in-plane compression, was investigated through the use of a modified J-integral, designed to retain path independence in the presence of initial stress and strain fields and nonproportional loading. Application of modified J values to predict fracture using probabilistic methods, and their use in a well-known structural integrity assessment code, showed that assumptions about levels of out-of-plane constraint, material hardening behavior, and the method of crack introduction have a significant influence on the conservatism of the resulting failure predictions. It was found that more realistic modeling of crack introduction had a major effect on the accuracy of failure predictions, with the effects of material hardening being of secondary importance.
Continuous Development of the L/V 32/40 and L/V 48/60 MAN B&W Engines
Authors: Wachtmeister Georg , Rieck Kai
Published: January 2009

Fierce competition, particularly in the market for medium-speed four-stroke diesel engines, requires the continuous technical development of the products available in that market. Alongside the continued pressure on reducing prices and demands for low fuel consumption rates without compromising power/bulk ratios and reliability, optimization work on medium-speed engines is increasingly also dominated by a tightening of emission regulations. Soot concentrations in the exhaust below the visibility level and constantly falling NOx exhaust concentrations place ever greater demands, particularly on the combustion process, supercharging and fuel injection systems. Recent years have seen extensive basic development work in this field using simulation calculations and tests on our 1L 32/40 research engine. This work produced an array of measures with which the trade-off between soot, NOx and specific fuel consumption can be effectively reduced. This paper discusses how these customer and market led measures are being implemented by our design engineers in our 32/40 and 48/60 engine types.
Analysis of the HCCI Combustion of a Turbocharged Truck Engine Using a Stochastic Reactor Model
Authors: Montorsi Luca , Mauss Fabian , Bianchi Gian Marco , Bhave Amit , Kraft Markus
Published: January 2009

Homogeneous Charge Compression Ignition (HCCI) engines arouse great interest due to their high thermal efficiency and very low emissions of nitrogen oxides (NOx) and particulates. Critical issue of the HCCI combustion is the control of the engine since the combustion process is mostly dominated by chemical kinetics. Therefore the accurate assessment of the chemical kinetic is fundamental in numerical simulation of this kind of engines. Experimentally it has been demonstrated that even in HCCI engine the charge within the cylinder is not fully homogeneous, but many quantities, such as temperature, density and equivalence ratio, vary along the combustion chamber. These inhomogeneities influence the combustion process and yield the homogeneous reactor model to be not completely adequate to simulate HCCI combustion. This paper focuses on the use of a stochastic rector model in order to account for temperature inhomogeneities in the numerical simulation of the HCCI combustion. Moreover, the chemical kinetic code has been coupled to GT – Power Code, a 1-D fluid – dynamics code, in order to accurately simulate the operation of a turbocharged truck engine.
Study on Different Flame Jet Ignition Variants in a Stratified Charge Spark Ignition Engine
Authors: Rakosi Edward , Rosca Radu
Published: January 2009

The paper presents some experimental results regarding a stratified charge spark ignition engine. We have applied the divided combustion chamber concept, using a flame jet in order to ignite the fuel-air mixture. The fueling system was a combined one: the cylinder head combustion chamber (secondary, auxiliary) was fueled by direct fuel injection, while the main combustion chamber was fueled with lean mixture by the means of a carburetor. During the tests we have used two types of main combustion chamber and three types of secondary combustion chamber. Thus, we had the possibility to use different compression ratios, starting with the lower ones, imposed by the less volatile fuels and ending with the higher ones, that led to the highest output power and a steady working process. In the meantime, three types of spark plugs were tested. We have also studied the HC and CO emissions, as well as the fuel consumption.
Heat Transfer Within Deforming Droplets
Authors: Dai Meizhong , Perot J. Blair , Schmidt David P.
Published: January 2009

The effect of droplet oscillation on internal heat transfer was investigated using a transient, three-dimensional Navier-Stokes solver for free-surface flows. The code solves conservation of momentum and energy on a three-dimensional deforming domain. The investigation sought to explore the effect that oscillations might have on temperature non-uniformity within droplets. Biot numbers of 0.1 and 0.25 were investigated for three different degrees of distortion: no perturbation, 13% and 35%. The droplets were given an initial perturbation and allowed to relax back to a spherical shape. The results show that the effect of the oscillation is minimal. As expected, the effect was greatest at large distortion and large Biot number. However, it appears that distortion does not contribute much to heat transfer within droplets.
The Development of a Dual Injection Hydrogen Fueled Engine With High Power and High Efficiency
Authors: Lee Jong T. , Kim Y. Y. , Caton J. A.
Published: January 2009

To achieve high power and high efficiency in a hydrogen fueled engine for all load conditions, the dual injection hydrogen fueled engine that can derive the advantage of both high efficiency from external mixture hydrogen engine and high power from direct cylinder injection hydrogen engine was introduced. For verifying the feasibility of the above engine, the high pressure hydrogen injector of ball valve type actuated by a solenoid was developed. A systematic experimental study was conducted by using a modified single cylinder dual injection hydrogen fueled engine which was equipped with both an intake injector and a high pressure in-cylinder injector. The results showed that (1) the developed high pressure hydrogen injector with a solenoid actuator had good gas-tightness and fine control performance, (2) the transient injection region, in which injection methods are changed from external fuel injection to direct-cylinder injection, ranged from 59 to 74 percent of the load, and (3) the dual injection hydrogen fueled engine had the maximum torque of direct-cylinder fuel injection and the maximum efficiency of external fuel mixture hydrogen engines.
Effects of Different LPG Fuel Systems on Performances of Variable Compression Ratio Single Cylinder Engine
Authors: Choi G. H. , Kim J. H. , Homeyer Christian
Published: January 2009

Since the early 20th century, most ground vehicles are driven with gasoline and diesel. The degradation of the environment affects human on earth unless the quality of the air is improved. One of the alternative fuels, LPG, is potentially capable of lowering vehicular emissions when compared to gasoline or diesel. There is a penalty in power output resulting from the use of LPG because the engine can induce less amount of air with Mixer system comparing with gasoline engine. Currently, the liquid-phase LPG is injected into the intake port of the engine, the fuel vaporizes enroute to the combustion chamber. Therefore, the performance and combustion processes of the tested engine are investigated with different LPG fuel systems. The test engine was developed and named heavy-duty VACRE. The test engine for this work operates 1400rpm with MBT conditions. The major conclusions of the work include; 1) The power output of LPi system with liquid-phase is approximately 17% higher than that of vapor-phase Mixer system due to increases of volumetric efficiency. And the MBT spark timing of LPi system is approximately 25% more advanced than that of Mixer system at λ value 1.0; 2) The LPi system shows both the maximum heat release rate and the cumulative heat release to be approximately 20% higher than the Mixer system; 3) Maximum cylinder pressure decrease with increase of compression ratio and a point of maximum cylinder pressure is delayed with high compression ratio.
Instantaneous Engine Speed Time-Frequency Analysis for On-Board Misfire Detection and Cylinder Isolation in a V12 High Performance Engine
Authors: Ponti Fabrizio
Published: January 2009

The diagnosis of a misfire event and the isolation of the cylinder in which the misfire took place is enforced by the On Board Diagnostics (OBD) requirements over the whole operating range for all the vehicles whatever the configuration of the engine they mount. This task is particularly challenging for engines with a high number of cylinders and for engine operating conditions that are characterized by high engine speed and low load. This is why much research has been devoted to this topic in recent years, developing different detection methodologies based on signals such as instantaneous engine speed, exhaust pressure, etc., both in time and frequency domains. This paper presents the development and the validation of a methodology for misfire detection based on the time-frequency analysis of the instantaneous engine speed signal. This signal contains information related to the misfire event, since a misfire occurrence is characterized by a sudden engine speed decrease and a subsequent damped torsional vibration. The identification of a specific pattern in the instantaneous engine speed frequency content, characteristic of the system under study, allows performing the desired misfire detection and cylinder isolation. Particular attention has been devoted in designing the methodology in order to avoid the possibility of false alarms caused by the excitation of this frequency pattern independently from a misfire occurrence. Although the time-frequency analysis is usually considered a time consuming operation and is not associated to on-board application, the methodology here proposed has been properly modified and simplified in order to obtain the quickness required for its use directly on-board a vehicle. Experimental tests have been performed on a 5.7 liter V12 spark ignited engine, with the engine mounted on-board a vehicle. The frequency pattern identified is not the same that could be observed when running the engine on a test bench, because of the different stiffness that the connection between the engine and the load presents in the two cases. This makes impossible to set-up the methodology here proposed only on a test bench, without running tests on the vehicle.
Experimentally Determined Port Discharge Coefficients From Large-Bore Reciprocating Engines
Authors: Chapman K. S. , Keshavarz A. , Li Yuanhong
Published: January 2009

This paper describes the collection and analysis of discharge coefficients from the ports of large-bore two-stroke cycle engines. The literature includes some information on discharge coefficients from very small ports. The literature was found to not include data collected from very large ports, such is in Cooper, Clark, and Worthington two-stroke cycle engines. The methodology was to construct and then use a flow bench that was sized for large-bore engine cylinder liners. The flow bench is designed to experimentally determine the discharge coefficients of large bore engine ports. The discharge coefficients are an integral part of determining the air flow rate through an engine, and in modeling and predicting the airflow through an engine system. This information can be used by designers to better match turbochargers and aftercoolers to engines. Large bore engine cylinders are typically are 35–56 cm (14–22 in.) in diameter, and have power outputs ranging 745–3730 kW (1,000–6,000 hp). In general, the majority of these engines were built in the 1940–1950’s. The importance of predicting the airflow rate through these engines has become paramount due to increasingly stringent EPA emission regulations. The data shows that there is a vast difference between the discharge coefficients of the three primary engines used in the natural gas industry.
The Advanced Injection Low Pilot Ignited Natural Gas Engine: A Combustion Analysis
Authors: Srinivasan Kalyan K. , Krishnan Sundar R. , Singh Sabir , Midkiff K. Clark , Bell Stuart R. , Gong Weidong , Fiveland Scott B. , Willi Martin
Published: January 2009

The Advanced Low Pilot Ignited Natural Gas (ALPING) engine is proposed as an alternative to diesel and conventional dual fuel engines. Experimental results from full load operation at a constant speed of 1700 rev/min are presented in this paper. The potential of the ALPING engine is realized in reduced NOx emissions (less than 0.2 g/kWh) at all loads accompanied by fuel conversion efficiencies comparable to straight diesel operation. Some problems at advanced injection timings are recognized in high unburned hydrocarbon (HC) emissions (25 g/kWh), poor engine stability reflected by high COVimep (about 6 percent), and tendency to knock. This paper focuses on the combustion aspects of low pilot ignited natural gas engines with particular emphasis on advanced injection timings (45°–60°BTDC).
A Theoretical and an Experimental Investigation of a Small Scale Trigeneration System: A Comparison Between Trigeneration and Separate Generation Systems
Authors: Wang Yaodong , Al-Shemmeri Tarik
Published: January 2009

A theoretical and an experimental investigation of a small scale trigeneration based on a diesel engine generator set is conducted. Comparing with the separate generation system, trigeneration saves primary energy input; and it reduces CO2 gas emission to the environment. A conclusion can be drawn that trigeneration is an environment friendly method, and it is financially feasible.
Preliminary Energy-Efficiency Analyses of an Active-Flow Aftertreatment System for Lean-Burn IC Engines
Authors: Zheng M. , Reader G. T.
Published: January 2009

Exhaust purification for lean-burn internal combustion engines has been impaired by the relatively low temperature of the exhaust that makes conventional passive aftertreatment schemes less energy-efficient in oxidation/regeneration. To tackle such adversaries, an active-flow control scheme, reversal-flow control, is outlined and analyzed in this paper. Preliminary energy-efficiency analyses are performed with different gas flow rate, flow reversal frequency, and monolith-solid properties. Simulation results indicate that through active thermal management the supplemental energy consumption can be drastically reduced, which is also supported by previous empirical studies.
Integration of a CAM Phaser on an Engine to Reduce Fuel Consumption: A Comprehensive Approach to the System
Authors: Gaudino P. , Bianco A. , Fiorenza R. , Pirelli M. , Pallotti P.
Published: January 2009

The paper presented describes the application of a Continuously Variable Cam Phaser (CVCP) to an existing engine, with the scope of reducing significantly the engine specific fuel consumption at part load, through the reduction of pumping losses. A single vane-type cam phaser was adopted, which controls both intake and exhaust cam events simultaneously, thanks to the particular cam timing assembly used on the base engine (FIAT-GM Powertrain FIRE 1,4 16v). The cam phaser itself is powered by the same oil which lubricates the engine, through a three-way solenoid valve controlled by the Engine Management System (EMS) with an on-off duty cycle signal. The design and experimental activity done to introduce the CVCP on an existing engine is described, which must comply with a number of key features needed (advance and retard travel speed, precision in actuation, minimum oil leakage, no increase of oil pressure required, minimum additional oil mass flow required) and constraints required (reduced modifications of base engine and of production line, system cost). In particular the base engine structure, which features cam timing command through toothed belt, limited room in the cylinder head for oil and blow-by gases, hydraulic tappets, wide camshaft bearing diameter, no external oil/gas separator, determined the need to limit the overall oil mass flow within the cylinder head: this was required to avoid possible oil recirculation into the intake manifold through the crankcase venting system. For this and other reasons, an accurate and comprehensive optimization of all the components involved in the above described system was needed. An extensive experimental activity was performed, which included the cam phaser design optimization, the re-definition of camshaft bearing and hydraulic tappet clearances, the re-design of piston rings, some prescriptions for the cam phaser control strategies and calibration of the EMS. This development work achieved a system definition which solves all the main problems described above, with no additional costs with respect to (w.r.t.) the first version of the CVCP engine, since no additional parts have been required nor particular material or machining or configurations were prescribed. The described engine is currently in its industrialization phase: it is planned to produce about 1000 engines/day in the Italian FIRE engine manufacturing plant (Termoli).
Reduced Fuel Consumption Engine for a CO2 < 125 g/km Vehicle, Through Friction Losses Reduction and Combustion Optimization
Authors: Gaudino P. , Accongiagioco A. , Formisano G. , Lucignano G. , Petraglia F.
Published: January 2009

Friction reduction is a very challenging theme in research and development on reciprocating engines, and in particular on engines for passenger cars. The points for improvement are several: valve train and timing command, piston package, liners, crankshaft, ancillaries and related command, lubrication, cooling, and involve optimization of couplings, components design, materials, manufacturing technology, etc. This paper presents a comprehensive activity of engine development, which starts from considerations about the single contribution of each functional group of the engine on total friction, selects the fields of research where the most effective results can be expected, and concludes with results obtained on a Demonstration Vehicle. The fuel consumption reduction obtained is about 11% with respect to (w.r.t.) the reference vehicle in the NEDC, with better performance. No modifications in terms of drag force, weight and gearbox/tyre configuration have been made to the vehicle itself. The main themes of development have been: a new lightened valve train, also featuring “shimless” mechanical tappets; and a new piston package, which includes a piston with only two segments, a newly designed con-rod and a lightened piston pin . The range of FMEP reduction obtained is about 10–26% w.r.t. base engine over the whole engine speed and load map, with the strongest effect in the low speed and load range. Additionally, a new thermodynamic package has been developed, including a new intake manifold and combustion chamber, to improve engine performance at full load and to have a further reduction in BSFC at part load. Furthermore, combustion optimization allows for a synergic effect together with friction reduction at low engine speed and load, which reflects in real-life vehicle urban driving. In fact, lower friction reduces the indicated torque needed for a given mechanical torque. At low engine speed load, lower IMEP gives lower thermodynamic efficiency and higher combustion instability. A parallel improvement in combustion efficiency reduces this negative effect, giving a higher engine efficiency. Combustion optimization also led to a reduction in the engine speed at idle, due to the improved combustion stability. This gives an additional reduction of vehicle fuel consumption. Finally, functionality and durability of the new components have been tested and validated. In particular, the new two-segments pistons have been optimized for blow-by and oil consumption, obtaining results equal to or lower than the standard package. Both the piston package and the new lightened valve-train have been tested for durability with procedures usually required for production validation.
Design and Evaluation of High Pressure Fuel Valve Nozzles Using the Method of Characteristics and CFD
Authors: Kim Sangwon , Mitchell Charles , Kirkpatrick Allan
Published: January 2009

The topic of this paper is the design of fuel valve nozzles for natural gas engines that maximize the kinetic energy and momentum of the injected fuel and maintain a required mass flow rate. The nozzle design used both the method of characteristics and computational fluid dynamics (CFD). Three types of nozzles were designed: a converging-diverging nozzle, three conical nozzles and an aerospike nozzle. The evaluation of the performance of the nozzle designs was conducted using Computational Fluid Dynamics. CFD simulations were used to calculate the average axial momentum per unit fuel mass and the average kinetic energy per unit fuel mass in the jets emanating from each nozzle. The performance was computed in off-design conditions (2.9MPa, 3.1MPa) as well as for the nominal design supply pressure of 3 MPa. Results showed that for the new nozzle designs, the average axial momentum per unit mass was improved by 17 to 24% and the average kinetic energy per unit fuel mass was improved by 30 to 80% compared with a standard shrouded poppet valve. Of the candidate designs, the converging-diverging nozzle gave the best performance, and the simple 15 degree conical nozzle also performed very well.
On-Engine Demonstration of Micro-Pilot Ignition System for a Cooper-Bessemer GMV-4TF
Authors: Brown Jacob A. , Mizia John , Olsen Daniel B. , Wilson Bryan D.
Published: January 2009

This investigation assesses the benefits of retrofitting a diesel micro-pilot ignition system on a Cooper-Bessemer GMV-4TF two-stroke cycle natural gas engine with a 14” (36 cm) bore and a 14” (36 cm) stroke. The pilot fuel injectors are mounted through an adaptor in one of the spark plug holes in a set of dual-spark plug heads. A high pressure, common-rail, diesel fuel delivery system is employed and customizable power electronics control the current signal to the pilot injectors. Pilot fuel is supplied by a variable displacement, high-pressure pump that is driven with an electric motor. Software is developed that interfaces with the pump and controls and monitors the fuel rail pressure. Micro-pilot quantities from 11.5 to 20 mm3 (.0007 to .0012 in3) are explored at rail pressures from 200 to 1400 bar (2,900 to 20,300 psig). Three independent variables, pilot ignition timing, pilot fuel quantity, and pilot fuel rail pressure, are manipulated. An optimization sequence is performed to minimize total fuel consumption.
Prospect of Reduced CO and NOx Emissions in Diesel Dual Fuel Engines
Authors: Mulenga Mwila C. , Reader Graham T. , Ting David S.-K. , Zheng Ming
Published: January 2009

A numerical analysis of homogeneous natural gas/diesel/air mixture, that could be formed when small amounts of diesel pilot are used in a diesel dual fuel engine or when using natural gas/diesel dual fuel homogeneous charge compression ignition combustion, was studied to provide insight on future experimental investigations to be conducted by the institution. Use was made of Curran’s normal-heptane mechanism in CHEMKIN to deduce its effects on lean fuel/air mixtures with respect to ignition timing and carbon monoxide (CO) and oxides of nitrogen (NOx) emissions. For the cases considered, increase in the amount of n-heptane addition resulted in advanced ignition closer to TDC thereby increasing peak cylinder pressure and gross IMEP. Increase in the amount of n-heptane addition also resulted in early decomposition of the fuel consequently advancing the production of OH radicals that oxidised the CO. For the same fuel/air mixture strength, increase in the amount of n-heptane addition increased NOx production due to increased peak temperature, residence time and availability of O2. When using leaner mixtures and small amounts of n-heptane to promote/advance ignition, however, peak cylinder temperatures were reduced and hence comparatively reducing engine-out NOx emissions.
The Goal of Emissions Regulations for Large Engines
Authors: Bouche´ Thomas , Dexter Stephen G.
Published: January 2009

The zero impact emissions engine is an engine which, while it still produces emissions, produces such a low level that it has a minimum effect on air quality. If this is the goal of emissions regulations for marine, power generation, locomotive and automotive engines, then this goal is possible because the technology will soon be available. Past and present regulations are studied and emissions reduction methods are considered. From this it is predicted that the zero impact emissions engine will only be demanded in exceptional cases. Research and development will continue to reduce emissions but only at a rate which is economically acceptable.
Membrane-substrate interface: Phospholipid bilayers at chemically and topographically structured surfaces
Authors: Parikha Atul N.
Published: January 2009

The surface-assisted fusion, rupture, and spreading of vesicles and hydration-induced spreading of lipids onto chemically and topographically structured surfaces gives rise to lipid structures useful for modeling many physical-chemical properties of lipid bilayers. Chemically structured surfaces produce a lipid structure revealing template-induced assembly of coexisting lipid phases, which reflect the underlying pattern of surface energy, wettability, and chemistry. In a construct derived using photochemically patterned molecular monolayers, the author found a spontaneous separation of fluid bilayer regions from the fluid monolayer regions by a controllable transition region or moat. The coexisting bilayer/monolayer morphologies derived from single vesicular sources are particularly attractive for the study of a range of leaflet-dependent biophysical phenomena and offer a new self-assembly strategy for synthesizing large-scale arrays of functional bilayer specific substructures including ion-channels and membrane-proteins. The uses of topologically patterned surfaces similarly provide new models to design complex three-dimensional membrane topographies and curvatures. These platforms promise fundamental biophysical studies of curvature-dependent membrane processes as well as useful bioanalytical devices for molecular separations within fluid amphiphilic membrane environments. Some future directions enabled by lipid self-assembly at structured surfaces are also discussed.
Lipid-anchored DNA mediates vesicle fusion as observed by lipid and content mixing
Authors: Chan Yee-Hung M. , van Lengerich Bettina , Boxer Steven G.
Published: January 2009

A general method for synthesizing 5′- and 3′-coupled DNA-lipid conjugates has been developed and employed in DNA-mediated vesicle fusion. Vesicles presenting complementary DNA fuse, resulting in both outer and inner leaflet mixing as well as content mixing. Fusion is maximized using 5′- and 3′-coupled DNA on opposite vesicle partners, rather than only 5′-coupled DNA, showing the importance of DNA orientation to the process. Lipid and content mixing assays show a dependence of fusion kinetics on the sequence and average number of DNA per vesicle. Vesicles without DNA or presenting noncomplementary sequences also appear to undergo some degree of lipid mixing or exchange, but no content mixing. Total lipid mixing appears to occur more efficiently than inner leaflet mixing and content mixing, and this may be explained by the observed nonspecific lipid mixing and/or the rise of a hemifused intermediate. The ability to control DNA sequence and the relative experimental simplicity of this system make it highly attractive to probe fundamental questions of membrane fusion using both ensemble and single vesicle assays.
Impedance spectroscopy of bilayer membranes on single crystal silicon
Authors: Lin Janice , Merzlyakov Mikhail , Hristova Kalina , Searson Peter C.
Published: January 2009

Bilayer membranes on solid supports are being developed as electrically addressable, robust, surface-supported membrane mimetics. These platforms are being explored for basic ion channel research as well as for detection and analyte sensing. The formation of bilayer membranes on semiconductor surfaces is an important step in device integration for transistor and sensor arrays. Here, the authors review the contributions to the impedance response of bilayer membranes on semiconductors, and highlight the important issues for experimental measurements. The authors also present experimental results for diphytanoyl phosphocholine bilayers formed on moderately doped and highly doped n-type silicon using Langmuir-Blodgett-based deposition techniques. The authors demonstrate that a detailed understanding of the contributions to the impedance response is important in developing silicon-based membrane platforms. The authors further report on the bias dependence of the impedance, and show that on highly doped n-type silicon, the membrane impedance can be measured over a 2 V range.
Stable insulating tethered bilayer lipid membranes
Authors: Vockenroth Inga K. , Ohm Christian , Robertson Joseph W. F. , McGillivray Duncan J. , Lösche Mathias , Köper Ingo
Published: January 2009

Tethered bilayer lipid membranes have been shown to be an excellent model system for biological membranes. Coupling of a membrane to a solid supports creates a stable system that is accessible for various surface analytical tools. Good electrical sealing properties also enable the use of the membranes in practical sensing applications. The authors have shown that tethered membranes have extended lifetimes up to several months. Air-stability of the bilayer can be achieved by coating the membrane with a hydrogel. The structure of a monolayer and its stability under applied dc potentials have been investigated by neutron scattering. © 2008 American Vacuum Society.
Evaluating the performance of fibrillar collagen films formed at polystyrene surfaces as cell culture substrates
Authors: Elliott John T. , Halter Michael , Plant Anne L. , Woodward John T. , Langenbach Kurt J. , Tona Alessandro
Published: January 2009

While it is well-appreciated that the extracellular matrix plays a critical role in influencing cell responses, well-defined and reproducible presentation of extracellular matrix proteins poses a challenge for in vitro experiments. Films of type 1 collagen fibrils assembled on alkanethiolate monolayers formed at gold-coated surfaces have been shown to elicit a cellular response comparable to collagen gels, but with the advantages of excellent optical properties, and high reproducibility and robustness. To make this collagen matrix more accessible to laboratories that do not have access to gold film deposition the authors have examined the use of untreated polystyrene as a substrate for forming fibrillar collagen films. Direct comparison of films of fibrillar collagen fibrils formed at polystyrene with those formed at alkanethiolate monolayers indicates that films of collagen formed on these two surfaces compare very favorably to one another, both in their supramolecular structural characteristics as well as in the cell response that they elicit. Both substrates exhibit a dense covering of fibrils approximately 200 nm in diameter. The spreading of fibroblasts and activation of the tenascin-C gene promoter are statistically equivalent as determined by a metric derived from the D-statistic normally used in the Kolmogorov-Smirnov statistical test. The results of this study suggest that biologically relevant, robust thin films of collagen fibrils can be formed in any laboratory in untreated polystyrene dishes and multi-well polystyrene plates.