bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrasonic Bonding of Membrane Electrode Assemblies for Low Temperature PEM Fuel Cells
Authors: Beck Joseph R. , Walczyk Daniel F. , Hoffman Casey J. , Buelte Steve J. 
Published: July 2013

Ultrasonic bonding of low temperature PEM membrane electrode assemblies has shown to cut the cycle time and energy input of manufacturing by over an order of magnitude each as compared to the industry standard of thermal pressing. Ultrasonic bonding uses high-frequency mechanical oscillations to convert electrical energy into heat energy which bonds the membrane electrode assembly components. This reduction in manufacturing resource requirement and time helps make fuel cell energy more economical as an alternative electrical power source. This paper will discuss ultrasonic and thermal bonding for low temperature Nafion fuel cells with 10 cm2 active area including process optimization and the effects of electrode type and membrane conditioning on ultrasonically bonded MEA performance.
A design set of experiments was created for both ultrasonic bonding and thermal pressing process optimization using commercially available electrodes and conditioned Nafion 115 membrane. Analysis of Variance suggests that neither energy nor pressure have a statistically significant effect on the performance on ultrasonically bonded MEAs. For thermally pressed MEAs, temperature was found to have a significant effect on performance while pressure was not. Neither manufacturing technique found interaction effects to be statistically significant.
Three different electrode compositions were tested on both ultrasonic and thermal MEA bonding methods. Electrodes investigated include two that were custom made in-house with catalyst loadings of 0.16 and 0.33 mg Pt/cm2, and one commercial electrode with 0.5 mg Pt/cm2. The lower loaded custom electrode had greater performance than the commercial electrode, which had higher platinum loading, indicating electrode architecture is an important factor in the performance of ultrasonically bonded MEAs.
Membrane electrode assemblies made using Nafion membranes that were pretreated with a conditioning process showed decreased performance compared to MEAs ultrasonically bonded from dry, unconditioned membrane in short-term testing. MEAs thermally pressed with the custom made electrodes performed better with conditioned membranes while the commercial electrodes showed decreased performance with conditioning.
Current electrodes have been optimized for thermal pressing as demonstrated by the two commercial electrodes having the largest performance decreases between thermally and ultrasonically manufactured MEAs. Future work includes intelligently designing an electrode for optimizing the ultrasonic bonding process for low temperature fuel cells to increase the performance of this manufacturing technique.
Experimental Study of Cylindrical Latent Heat Energy Storage Systems Using Lauric Acid as the Phase Change Material
Authors: Liu Chang , Murray Robynne E. , Groulx Dominic 
Published: July 2013

Phase change materials (PCMs) inside latent heat energy storage systems (LHESS) can be used to store large amounts of thermal energy in relatively small volumes. However, such systems are complicated to design from a heat transfer point of view since the low thermal conductivity of PCMs makes charging and discharging those systems challenging on a usable time scale.
Results of experiments performed on both a vertical and a horizontal cylindrical LHESS, during charging, discharging and simultaneous charging/discharging, are presented in this paper. Both LHESS are made of acrylic plastic, the horizontal LHESS has one 1/2″ copper pipe passing through its center. The vertical LHESS has two 1/2″ copper pipes, one through which hot water flows, and the other through which cold water flows. Each of the pipes has four longitudinal fins to enhance the overall rate of heat transfer to and from the PCM, therefore reducing the time required for charging and discharging.
The objective of this work is to determine the phase change behavior of the PCM during the operation of the LHESS, as well as the heat transfer processes within the LHESS. Natural convection was found to play a crucial role during charging (melting) and during simultaneous charging/discharging (in the vertical LHESS). However, during discharging, the effect of natural convection was reduced in both systems.
Analysis of a Hybrid PCM-Air Heat Sink
Authors: Kozak Y. , Abramzon B. , Ziskind G. 
Published: July 2013

Phase-change materials (PCMs) can absorb large amounts of heat without significant rise of their temperature during the melting process. This effect may be utilized in thermal energy storage and passive thermal management. In order to enhance the rate of heat transfer into PCMs, various techniques have been suggested, like fins, metal and graphite-compound matrices, dispersed high-conductivity particles inside the PCM, and micro-encapsulation.
The present work deals with a hybrid PCM-air heat sink. The heat is dissipated on the heat sink base, and may be either absorbed by the PCM stored in compartments with conducting walls, or dissipated to the air using fins, or both. The heat sink is made of aluminum 6061. Eicosane (C20H42, 96% purity, nominal melting temperature 36.7°C) is used as the PCM. In order to exclude the effect of sensible heating below the melting temperature, a controllable environment is used. The latter is created in a programmable forced-circulation oven.
A simplified thermal model is developed for a conservative estimation of temperature growth of the heat sink base. The results of this model are compared to the experimental results. The relative contributions of heat accumulation, both by latent and sensible heat, and of heat removal by air are presented and discussed.
Selection of Fuel in Different Occupancy Types by Computational Fluid Dynamics
Authors: Lau K. W. , Chow W. K. , Fong N. K. 
Published: July 2013

Computational Fluid Dynamics (CFD) has been widely used to evaluate the effects of fire on people and buildings by predicting temperature, radiation heat flux, smoke visibility and combustion products. In this paper, CFD was used to study plume temperature, radiation heat flux, visibility and carbon monoxide concentration in a building fire. The CFD software Fire Dynamics Simulator (FDS) developed by the National Institute of Standards and Technology of USA is generally adopted to model the various fire scenarios in buildings.
For FDS modeling, the type of fuel is considered an important input parameter which has a significant effect on the simulation results of different types of combustibles, hence the fire hazard evaluation. In the combustion model of FDS, the fuel and oxygen are burnt to give fire products such as carbon dioxide, water, carbon monoxide and soot. Fuels including propane, wood, polyurethane and polyvinyl-chloride were used in the simulation. By using the same fire size and fuel bed for different combustibles under study, a peak fire size of 3 MW was adopted. Simulations were then carried out with different fuel and respective reaction parameters of these combustibles. Simulation results, the output quantities of plume temperature, visibility, carbon monoxide concentration and radiation heat flux for different scenarios obtained were analyzed and evaluated.
It was observed that there were reasonable differences in the results from the fuel packages of different combustibles. These differences were evaluated and their significance was discussed.
Mechanism for High Velocity Turbulent Jet Combustion From Passive Prechamber Spark Plug
Authors: Chiera Domenico , Riley Mike , Hampson Gregory J. 
Published: July 2013

Next generation passive prechamber spark plugs for high BMEP natural gas engines require long ignition delay for durability, fast combustion for efficiency, and low COV for lean engine operation. Additionally, a successful plug should have long life, low cost, and have a robust knock margin, with best-in-class NOx vs. fuel consumption.
This paper discusses the underlying physics of the novel passive prechamber spark plug, the Woodward–Lean Quality Plug (WW-LQP.) The WW-LQP has demonstrated good ignition delay, fast combustion, and low COV at λ > 1.8+, while improving fuel consumption by more than 1% on a lean natural gas engine.
The key operating principles are developed for achieving complete combustion of the prechamber “charge”, leading to high prechamber pressure rise and resulting in high velocity turbulent flame jets, which in-turn provides for fast combustion in the main chamber. The design physics are verified by CFD simulations and on-engine experiments, including pressure measurements in both the prechamber and main combustion chamber.
Investigation of Fuel Spray Propagation, Combustion and Soot Formation/Oxidation in a Single Cylinder Medium Speed Diesel Engine
Authors: Unfug Fridolin , Wagner Uwe , Beck Kai W. , Pfeil Juergen , Waldenmaier Ulf , Celik Oguz , Jaeschke Johannes , Metzger Juergen 
Published: July 2013

To fulfil strict emission regulations and the need for higher efficiency of future Diesel engines require an optimized combustion process. Optical investigations represent a powerful tool for getting a better understanding of the ongoing processes. For medium speed Diesel engines, optical investigations are relatively rare or not available. The “Institut für Kolbenmaschinen” (IFKM) and MAN Diesel & Turbo SE performed extensive optical in-situ investigations of the injection and combustion process of a MAN 32/44 CR single cylinder medium speed Diesel engine that provide previously unavailable insights into the ongoing processes. The optical investigations aimed on fuel spray visualization, high-speed soot luminescence measurement and two colour pyrometry applied for five combustion chamber regions.
To apply the optical measurement techniques, two optical accesses were designed. Access no. 1 is placed near the cylinder liner. Access no. 2 is located close to the injector in a 46° angle to the cylinder vertical axis. An insert was used which consists of an illumination port and a visualization endoscope. Additionally some special nozzle designs were used beside the standard nozzle, which have one separated nozzle hole. This enables a simultaneous view from both optical accesses on the same flame cone.
For Mie-Scattering investigation a pulsed Nd:YAG-Laser with 532 nm wavelength was used for illumination and a CCD-camera with an upstream 532 nm optical filter was used for visualization. This combination allows observing the liquid fuel distribution even after start of combustion. Penetration depth of liquid fuel spray was analysed for different swirl numbers, intake manifold pressures, injection timings and injection pressures.
High-speed flame visualization was done by two CMOS cameras which were mounted at two different optical accesses with view on the same flame cone. Due to this application a simultaneous measurement of the flame distribution of two different views was possible. This enables a 3-dimensional investigation of the flame propagation process.
In addition, the advanced two colour pyrometry was applied for five different regions of the same flame cone. Due to a calibration after each measurement the absolute radiant flux can be calculated and thus the absolute temperature and soot concentration. With this procedure it was possible to give a real temperature and soot concentration distribution of the flame cone.
To provide more detailed information about the combustion process, selected engine operation points were simulated with a modified version of the CFD code KIVA3v-Release2 at the IFKM. The simulated results were compared to the measured data.
Study of Diesel Air-Fuel Mixing and Combustion at High Injection Pressures in a Rapid Compression Machine
Authors: Pribicevic I. , Sattelmayer T. 
Published: July 2013

Diesel air-fuel mixing and combustion have been investigated in a Rapid Compression Machine (RCM). The measurements were performed at high injection pressures up to 260 MPa and under reacting and non-reacting conditions. The spray was injected through solenoid-controlled multi-hole injectors. Two nozzles were applied with orifice diameters of 175 μm (D175) and 150 μm (D150), respectively. The visualization of the penetration of the liquid and the gaseous phase as well as the spray cone angle under evaporative, non-reacting conditions was carried out by the shadowgraph imaging technique in combination with a high speed camera. For combustion studies the flame luminosity of the flame as well as the chemiluminescence signals emitted by the OH radicals in the UV range were detected.
Investigations revealed different behavior of the macroscopic spray characteristics with the two applied nozzles when increasing the injection pressure from 200 MPa to 260 MPa. With the larger nozzle diameter (D175) the spray penetration and the spray propagation velocity increase as the injection pressure is increased. On the contrary to that, with the smaller nozzle diameter (D150) an increase of the injection pressure had no effect on the spray velocity. With 260 MPa a higher spray penetration was only observed at the beginning of the injection due to the faster opening of the needle. The further propagation of the tip of the spray was similar with 200 MPa and 260 MPa. With both applied nozzles the injection pressure has little effect on the penetration length of the liquid phase. At an applied injection pressure of 200 MPa the near-nozzle spray angle is wider with D175, whereas similar spray angles were observed at 260 MPa. From the measurements in reacting atmosphere an earlier ignition of the fuel and a faster combustion could be shown with nozzle D150. In addition, a higher combustion pressure was measured. This can be attributed to better air-fuel mixing and a higher premixed portion, which was confirmed by the analysis of the spray angles in the far-nozzle region obtained from the shadowgraph images at non-reacting conditions.
Effects of Biodiesel Distillation Process of Waste Cooking Oil Blends on Particle Number and Mass Emissions
Authors: Cordiner S. , Mecocci F. , Mulone V. , Rocco V. 
Published: July 2013

The use of biodiesel has been widely accepted as an effective solution to reduce greenhouse emissions. The high potential of biodiesel in terms of PM emission reduction may represent an additional motivation for its wide diffusion. This potential is related to the oxygenated nature of biodiesel, leading to a different PM-NOx trade-off. Wide diffusion is also under debate as it may represent a solution to the highly disputed issue of the development of alternative biofuels sources not competing with the food chain. In fact, besides second generation biofuels (e.g. from algae), the transesterification of Waste Cooking Oil (WCO) is another option, that however needs additional insight. In fact, in this case, the effects on particle emissions are still not well assessed, as well as the impact of fuel distillation on engine performance and emissions.
In this paper an experimental study on particle emissions of a DEUTZ 4L off-road Diesel engine coupled to a DOC-DPF system is proposed. Experimental data have been gathered at the engine test bench of the University of Rome Tor Vergata, by using baseline fossil fuel (B06) and blends (30% vol) with both distilled and non distilled WCO biodiesel. Data have been acquired with respect to the three most probable engine points referring to the NRTC (Non-Road-Transient-Cycle), upstream and downstream of the AfterTreatment System.
Results show that B30 fuels have always lower emission on a mass and number basis, and that distillation process may have an impact especially at high power and torque operation. A slightly better behavior in terms of mass emissions has been observed for the blend with distilled fuel, while a slightly better behavior in terms of particle number has been observed for the blend with non-distilled fuel.
Influence of Post-Injection Parameters on Soot Formation and Oxidation in a Common-Rail-Diesel Engine Using Multi-Color-Pyrometry
Authors: Barro Christophe , Tschanz Frédéric , Obrecht Peter , Boulouchos Konstantinos 
Published: July 2013

The emission trade-off between soot and NOx is an issue of major concern in automotive diesel applications. Measures need to be taken both on the engine and on the aftertreatment sides in order to optimize the engine emissions while maintaining the highest possible efficiency. It is known that post injections have a potential for exhaust soot reduction without any significant influence in the NOx emissions. However, an accurate and general rule of how to parameterize a post injection such that it provides a maximum reduction of soot emissions does not exist. Moreover, the underlying mechanisms are not understood in detail.
The experimental investigation presented here provides insight into the fundamental mechanisms of soot formation and reduction due to post injections under different turbulence and reaction kinetic conditions. In parallel to the measurement of soot elementary carbon in the exhaust (using a Photo Acoustic Soot Sensor), the in-cylinder soot formation and oxidation process have been investigated with an Optical Light Probe (OLP). This sensor provides crank angle resolved information about the in-cylinder soot evolution.
The experiments confirm conclusions of earlier works that soot reduction due to a post injection is mainly based on two reasons: increased turbulence (from the post injection) during soot oxidation and lower soot formation due to lower amount of fuel in the main combustion at similar load conditions. A third effect of heat addition during the soot oxidation, which was often mentioned in the literature, could not be confirmed. In addition, the experiments show that variations of turbulence (from swirl) and reaction kinetics have a minor influence on the diffusion controlled heat release rate. However, the time phasing of the soot evolution is highly influenced by these variations with only small changes in the peak soot concentration. It is shown that the soot reduction of a post injection depends on the timing. More precisely, the soot reduction capability of a post injection decreases rapidly as soon as its timing is late in the soot oxidation phase. The soot oxidation rate can only be improved by increased turbulence and heat addition from the post injection in a time window before the in-cylinder soot peak occurs. Depending on EGR and swirl level, a maximum dwell time can be defined after which the post injection effect becomes counterproductive with respect to the soot oxidation rate.
Improved Tin Based Bearing Alloy for Low Emission Two-Stroke Engines
Authors: Haedicke Lukas , Mergen Robert , Kari Alexander , Harreither Leopold 
Published: July 2013

Recent in Two-stroke engine development for marine applications mainly deal with better and increased overall efficiency hereby reducing the CO2 emissions. Besides a mechanical design change the service conditions play a major role in enhanced efficiency. The so increased engine parameters with higher maximum pressure during combustion will inevitable increase the load on the bearings of the reciprocating parts. Since an increase in the bearing area is not possible due to the engine design parameters the object is to increase the specific load bearing capability of the bearing alloy while keeping the tribological benevolence. In particular, the fatigue properties and the strength of the used tin based alloys, commonly known as whitemetals or babbitts.
This class of alloys stands out due to its emergency running capabilities, embedability and its high flexibility under edge load. Existing Al-based alloys like AlSn40 have improved fatigue properties but they fall behind on the named essential properties. Also, the dimensions of the AlSn40 bearings are limited due to the roll bonding process by which they are produced. On the other hand spin casting as standard production process of Babbitt bearings is limiting the alloying elements due to centrifugal segregation while solidification of the lining alloy. While tin based alloys are used in an environment of 90°C the homologue temperature is 0,7 which means that classic strengthening mechanisms like work-hardening and grain size effects are only shortly employable. Another restricting fact is the requirement of solid solubility for solid solution strengthening which also includes precipitation hardening. Hence there is a limited amount of elements dissolvable and not environmentally hazardous in tin this mechanism is already used to its maximum in the standard babbitts.
In this paper a possible way to circumvent these limits will be presented. The use of high melting elements, compared to Sn, like Co, Ni, Mn, Al and Zn which are partly dissolvable in molten Sn, where used to improve the microstructure and therefor the overall performance of the bearing alloy.
These trace elements serve as grain refinement for the primary precipitation of SbSn and CuSn during solidification. The high melting point of these elements anticipates relaxing processes in the alloy caused by diffusion at the high homologue temperature. Due to the smaller precipitations and the finer structure a better performance can be seen during tests. This leads in a higher strength while maintaining its ductility. Alternate bending tests as well as specific bearing test runs show a significant better fatigue, wear and embedability performance than standard alloys.
Assessing the Effect of E22 Fuel on Two-Stroke and Four-Stroke Snowmobile Performance and Emissions
Authors: Rittenour Michael D. , Weber James C. , Miers Scott A. 
Published: July 2013

A limited amount of information exists on the effect of higher ethanol content fuel (greater than 10 vol%) for recreational vehicle engines. The possibility exists for misfueling of these vehicles, as ethanol content may increase at gas stations in the near future. Engine management systems in the recreational vehicle market are typically not equipped with feedback controls to adapt to the increased ethanol content. To address this concern and generate preliminary data related directly to the recreational industry, a study was conducted to evaluate the impact of E22 fuel on steady-state emissions and performance of two production snowmobiles. To fully analyze the impact of higher ethanol blends, cold-start, durability, and material compatibility tests should be performed, in conjunction with emissions and performance tests. While these additional tests were not performed as part of this study, there is a test program that is assessing all these factors on E15 fuel, which will be released in fall 2012. E0 fuel was used to establish baseline performance and emissions data. A 2009 four-stroke snowmobile with a 998cc, liquid-cooled, four-cylinder, intake port-fuel injected engine and a 2009 two-stroke snowmobile with a 599cc, liquid-cooled, two-cylinder, electronically controlled, crankcase-fuel injected engine were used for this study. Neither vehicle had any feedback air-fuel controls or after-treatment devices in the exhaust system. Power, fuel consumption, relevant engine temperatures, as well as, regulated exhaust emissions were recorded using the EPA 5-mode certification test cycle.
The data showed no major impact on power output for either the four-stroke or two-stroke snowmobile. Brake specific fuel consumption varied with E22 as compared to E0. A reduction in CO emissions for both vehicles was observed for the E22 fuel. Both vehicles were factory calibrated rich of stoichiometric and hence, the addition of ethanol to the fuel effectively leaned out the air/fuel ratio and thus reduced the CO emissions. HC emissions were reduced for both the four-stroke and two-stroke engines, though certain test points of the two-stroke engine produced HC emissions that exceeded the analyzer measurement range (idle). Leaner operation reduced HC formation. Exhaust gas temperatures were observed to increase from 20°C – 50°C with E22 fuel, due to enleanment.