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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Strategies for reducing hydrocarbon emissions in diesel low temperature combustion

Sogbesan, Oluwasujibomi January 2016 (has links)
Government legislation on particulate matter (PM) and oxides of nitrogen (NOX) emissions have become increasingly stringent over the past decades. Future projections have led to internal combustion (IC)engine developers exploring advanced combustion technologies which may replace or supplement current state of the art systems. Advanced combustion technologies such as Low Temperature Combustion (LTC) cover a broad series of mechanisms that seek to attain in-cylinder Equivalence ratio (f) - Temperature (T) combinations during combustion which lead to acceptable emissions of exhaust PM and NOX. These are generally achieved by a combination of EGR dilution and extended ignition delays for mixture preparation. Another common feature of LTC is the poor combustion efficiency due to severe requirements placed on mixture quality as lower temperatures and oxygen concentrations reduce local ignitability limits. Therefore, a significant amount of work on LTC is centred around understanding the spatial and temporal development of inadequately prepared mixtures during LTC. The investigations presented in this thesis are expected to contribute to this body of work as they are predicated on the hypothesis that current mixture preparation methods are insufficiently adapted to conditions present in LTC combustion modes.
2

Strategies for Reduced Unburned Hydrocarbon and Carbon Monoxide Emissions in Diesel Propane Dual Fuel Low Temperature Combustion

Hodges, Kyle Anthony 09 December 2016 (has links)
The present manuscript discusses the use of two diesel injections in diesel-ignited propane dual fuel Low Temperature Combustion (LTC). Using propane fumigation into the intake runners of a single cylinder research engine, the maximum and minimum percent energy substitution (PES) values were obtained to be 90% and 53%, respectively at 3.3 bar BMEP. An optimal PES value of 80% was used to explore the effects of a secondary injection on the engine-out emissions. The secondary injection proved to have a strong influence on combustion phasing (CA50). As combustion is phased closer to TDC the IFCE shows and increase of 4% at 5 bar BMEP and 6% at 3.3 bar BMEP. Finally, a relationship between the IFCE and the CO to CO2 conversion was developed. An increase in the carbon to hydrogen ratio of the fuel shows a reduction of the CO output of the engine while the CO2 concentration increases. More importantly however, the CO to CO2 conversion shows a direct effect on the IFCE. It is shown that a decrease in CO emissions found in the engine-out emissions will correlate directly with an increase in the IFCE.
3

Employer offering and employee participation in long-term care health insurance

LaDuca, Michael Christopher 01 January 2004 (has links)
The purpose of this study is to report the current state of employer offering and employee participation in Long-Term Care Health Insurance within the Central Florida area. By distributing a voluntary survey to numerous businesses, information was collected from employers throughout the area regarding the plans and options available within their organizations. Through assessment and analysis of the information, a gauge of the present state of the workplace and Long-Term Care Insurance coverage in Central Florida has been established. What you will find within these pages is the availability and involvement of this insurance along with the options, awareness, advantages, and disadvantages it encompasses. I hope that you will in some way benefit from it.
4

Detailed Characterization of Conventional and Low Temperature Dual Fuel Combustion in Compression Ignition Engines

Polk, Andrew C 11 May 2013 (has links)
The goal of this study is to assess conventional and low temperature dual fuel combustion in light- and heavy-duty multi-cylinder compression ignition engines in terms of combustion characterization, performance, and emissions. First, a light-duty compression ignition engine is converted to a dual fuel engine and instrumented for in-cylinder pressure measurements. The primary fuels, methane and propane, are each introduced into the system by means of fumigation before the turbocharger, ensuring the airuel composition is well-mixed. Experiments are performed at 2.5, 5, 7.5, and 10 bar BMEP at an engine speed of 1800 RPM. Heat release analyses reveal that the ignition delay and subsequent combustion processes are dependent on the primary fuel type and concentration, pilot quantity, and loading condition. At low load, diesel-ignited propane yields longer ignition delay periods than diesel-ignited methane, while at high load the reactivity of propane is more pronounced, leading to shorter ignition delays. At high load (BMEP = 10 bar), the rapid heat release associated with diesel-ignited propane appears to occur even before pilot injection, possibly indicating auto-ignition of the propane-air mixture. Next, a modern, heavy-duty compression ignition engine is commissioned with an open architecture controller and instrumented for in-cylinder pressure measurements. Initial diesel-ignited propane dual fuel experiments (fumigated before the turbocharger) at 1500 RPM reveal that the maximum percent energy substitution (PES) of propane is limited to 86, 60, 33, and 25 percent at 5, 10, 15, and 20 bar BMEP, respectively. Fueling strategy, injection strategy, exhaust gas recirculation (EGR) rate, and intake boost pressure are varied in order to maximize the PES of propane at 10 bar BMEP, which increases from 60 PES to 80 PES of propane. Finally, diesel-ignited propane dual fuel low temperature combustion (LTC) is implemented using early injection timings (50 DBTDC) at 5 bar BMEP. A sweep of injection timings from 10 DBTDC to 50 DBTDC reveals the transition from conventional to low temperature dual fuel combustion, indicated by ultra-low NOx and smoke emissions. Optimization of the dual fuel LTC concept yields less than 0.02 g/kW-hr NOx and 0.06 FSN smoke at 93 PES of propane.
5

Auto-inflammation de mélanges pauvres assistée par plasma / Plasma assisted auto-ignition of lean mixtures

Prevost, Vivien 28 October 2013 (has links)
Le durcissement des normes d’émission, tout autant que l’impératif d’économie,poussent à étudier de nouveaux modes de combustion pour les moteurs. L’autoallumage decharges homogènes à basse température offre de bonnes perspectives quant au rejet de NOx,suies, et CO2. Cependant son control reste délicat, car il est extrêmement sensible à latempérature et la cinétique de l’hydrocarbure. L’assistance par plasma hors-équilibre pourraitfournir une solution. Les expériences sont menées dans une MCR avec des mélanges pauvresd’isooctane/air et un prototype d’allumeur Renault. La combustion obtenue identifiée commeSICI se déroule en deux phases: la propagation d’une flamme comprime les gaz restantjusqu’à leur autoallumage. Le réchauffement du système expérimental est intégré dans leprotocole d’exploitation, afin de quantifier l’effet SICI relativement à l’autoallumage pur.L’effet du plasma semble avant tout dépendre de l’énergie déposée, bien qu’il convergerapidement, quel que soit l’avance du déclenchement. Le comportement asymptotique à hauteénergie s’explique par la thermalisation des filaments, soulignée par comparaison avec l’effetSICI d’un arc classique. A l’inverse, le seuil minimal d’énergie nécessaire semble lié à lacapacité à générer un noyau de flamme viable, rapprochant le phénomène d’un problèmeclassique d’allumage en conditions difficiles. La propagation de la flamme détermine ledéclenchement de l’autoallumage selon une caractéristique linéaire particulièrementremarquable, car indépendante des conditions thermodynamiques du mélange. L’existenced’une flamme froide est mise en avant par des acquisitions de PLIF formaldéhyde. Lapréréaction semble accélérer la propagation du front de flamme. / Emission standards tightening as well as economical needs urge to study newcombustion modes for engines. Low-temperature homogeneous charge auto-ignition offersgood prospects for NOx, soot, and CO2 emissions. However, its control remains sharp for it isextremely influenced by temperature and fuel chemistry. Assisting non-equilibrium plasmascould provide a solution. Experiments are RCM managed with lean isooctane/air mixtures andprototype Renault ignition devise. Combustion occurs in a two steps mode known as SICI:flame propagation compresses the remaining gas to auto-ignition. The experimental settemperature rise is computed in order to measure the SICI effect compared to pure autoignition.The plasma seems to act mainly through the energy dropped, albeit its effect quicklyreaches a maximum, no matter how early it starts. This asymptomatic high energy behaviorrelies on the streamers overheating, as underlined by the look-like SICI effect from a regulararc discharge. On the contrary, minimal required energy appears to be linked to the capabilityof generating a sustainable flame kernel, making it closer to a standard ignition issue in roughconditions. Flame propagation sets auto-ignition start, according to an astonishingly linearcharacteristic not even influenced by charge’s thermodynamic conditions. Cool flame is putforward through formaldehyde PLIF imaging. Prereaction seems to enhance front propagationspeed.
6

Investigation into the Emissions and Efficiency of Low Temperature Diesel Combustion

Knight, Bryan Michael 2010 August 1900 (has links)
As global focus shifts towards the health and conservation of the planet, greater importance is placed upon the hazardous emissions of our fossil fuels, as well as their finite supply. These two areas remain intense topics of research in order to reduce green house gas emissions and increase the fuel efficiency of our vehicles. A particular solution to this problem is the diesel engine, with its inherently fuel-lean combustion, which gives rise to low CO2 production and higher efficiencies than its gasoline counterpart. Diesel engines, however, typically exhibit higher nitrogen oxides (NOx [NOx = NO NO2, where NO is nitric oxide and NO2 is nitrogen dioxide]) and soot. There exists the possibility to simultaneously reduce both emissions with the application of low temperature diesel combustion (LTC). While exhibiting great characteristics in simultaneous reductions in nitrogen oxides and soot, LTC faces challenges with higher carbon monoxide (CO) and hydrocarbon (HC) emissions, as well as penalties in fuel efficiency. The following study examines the characteristics of LTC which contribute to the differences in emissions and efficiency compared to typical conventional diesel combustion. More specifically, key engine parameters which are used to enable LTC, such as EGR and fuel pressure are swept through a full range to determine their effects on each combustion regime. Analysis will focus on comparing both combustion regimes to determine how exhaust gas recirculation (EGR) and fuel pressure relate to lowering NO and smoke concentrations, and how these relate to a penalty in fuel efficiency. This study finds that the application of LTC is able to realize a 99 percent reduction in NO while simultaneously reducing smoke by 17 percent compared to the conventional combustion counterpart. Through a sweep increasing EGR, LTC is able to defeat the typical soot – NO tradeoff; however, brake fuel conversion efficiency decreases 6.8 percent for LTC, while conventional combustion realizes a 4 percent increase in efficiency. The sweep of increasing fuel pressure confirms typical increases in NO and decreases in smoke for both LTC and conventional combustion; however, brake fuel conversion efficiency increases 2.3 percent for LTC and drops 4 percent for conventional combustion.
7

The organisation of care for people with multimorbidity in general practice : an exploratory case study of service delivery

Lewis, Rachel January 2015 (has links)
This thesis explores the provision of services for people with multimorbidity in general practice. It considers 3 broad research questions: how services are organised; why they are configured in this way; and the impact this organisation has on service delivery. At present, there is no formalised system for managing multimorbidity in general practice. Current arrangements reflect the wider organisation of care for chronic conditions which typically involves managing individual chronic conditions. The needs of people with multimorbidity are often complex and require a number of services from several providers. Coordinating these services is challenging, not least because of the fragmented system within which professionals and providers are situated. Different clinical, managerial and funding arrangements complicate this situation, creating as it does a number of parallel work streams. Effective healthcare for people with multimorbidity requires different providers to work collaboratively to promote linkage across professional and service boundaries. Information flows and administration play an important role in promoting continuity and coordination within and across work streams that span primary, secondary and tertiary care. In some instances, inefficiencies in services can be linked to the lack of integrative working between the clinical and administrative aspects of care. At present, fragmented systems are perpetuated by the lack of a whole systems approach that would align clinical, managerial and financial aspects of service provision across organisations. This thesis demonstrates that, services in general practice are increasingly determined by factors external to it. Most notably the division of care across multiple providers and the financial and contractual arrangements which require an organisation of services that promotes a division of labour and a routinsation, aimed at optimising the daily through put of patients. If the present and future needs of people with multimorbidity are to be effectively met, changes to the way services are provided in general practice must be considered as part of a whole system of healthcare, whereby collaborations between different professionals and services are intentionally organised and actively managed. Although the evidence base for managing multimorbidity is limited, there is a growing recognition that in terms of improving outcomes for people with multimorbidity, improving clinical care alone is not as effective as simultaneously improving the organisation or design of services across the whole system of provision.
8

Planning for Future Long-Term Care Needs: Life Course Catalysts and Constraints

Robbins, Emily J. 08 August 2011 (has links)
No description available.
9

Potential of ozone to enable the low load operation of a Gasoline Compression Ignition engine / Potentiel de l’ozone pour atteindre le fonctionnement en faible charge d’un moteur essence à allumage par compression

Pinazzi, Pietro Matteo 18 January 2018 (has links)
Le moteur essence à allumage par compression (GCI), reposant sur la combustion partiellement prémélangée de l'essence (GPPC), peut potentiellement assurer des opérations efficaces et propres. Le moteur GCI s'est avéré efficace à forte charge, mais l'indice d'octane élevé de l'essence limite considérablement les opérations à faible charge. Le présent travail étudie le potentiel de l'utilisation de l'ozone, fort agent oxydant, pour améliorer la réactivité de l'essence et permettre le fonctionnement à faible charge de GCI. L'ozone peut être produit on board en équipant le moteur d'un générateur d'ozone, sans impact dramatique sur le coût du moteur et sur la complexité du contrôle du moteur. Les essais effectués avec un moteur monocylindre ont montré que l'ozone favorise la combustion HCCI de l'essence, permettant d'étendre la limite d’auto-inflammation et de réduire la température minimale nécessaire de celle-ci. Les diagnostics optiques ont montré que ces propriétés sont liées à une prolifération radicale accrue, amenées par des réactions à basse température induites par l'ozone. En parallèle, le processus de combustion GCI a été étudié dans des conditions de faible charge. Sans ozone, la température d'admission doit être considérablement augmentée pour permettre l'auto-inflammationdes mélanges essence-air pauvres. De plus, les résultats indiquent que le monoxyde d’azote (NO) contenu dans les gaz brûlés résiduels peut, dans certaines conditions, favoriser fortement la combustion GCI. Ensuite,l'effet de l'ozone a été étudié dans des conditions d'injection directe GCI. Les résultats démontrent qu’une stratégie avec double injection est nécessaire pour maximiser l’effet promoteur de l’ozone et pour contrôler le processus de combustion GCI. Enfin, l'utilisation d’une forte concentration d’ozone a permis d’atteindre des opérations à faible charge en mode GCI, avec des faibles émissions de NOx et de suie, et cela, sans avoir besoin d'augmenter la température ou la pression d'admission. / Gasoline Compression Ignition (GCI) engine, relying on Gasoline Partially Premixed Combustion (GPPC) has potential for efficient and clean operations. GCI engine showed to be effective at high load, however, the highoctane number of gasoline dramatically limits low load operations. The present work investigates the potential of using ozone, a strong oxidizing agent, to improve gasoline reactivity and enabling low load GCI operation.Ozone can be produced in-situ and on-demand by equipping the engine with an ozone generator, without a dramatic impact on the engine cost and the engine control complexity. Experiments in a single cylinder engine showed that ozone promotes gasoline HCCI combustion, making possible to extend the lean limit and reducing the minimum temperature needed for autoignition. Optical diagnostics showed that these properties are related to an increased radical proliferation related to ozone-induced low temperature reactions. In parallel, GCI combustion process was investigated under low load conditions. Without ozone, the intake temperature should be considerable increased to enable auto ignition of lean gasoline-air mixtures. Moreover, results indicated that the NO contained into residual burnt gases can strongly promote GCI low load combustion. Finally, the effect of ozone was investigated under GCI direct-injection conditions, demonstrating that low load GCI operation with low NOx and Soot emission can be achieved by seeding the intake of the engine with ozone without needing of increasing the intake charge temperature or boosting the intake pressure.
10

Augmenting Serial Streaming Telemetry with iNET Data Delivery

Reinwald, Carl 10 1900 (has links)
ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, Nevada / Incorporating network-based telemetry components into a flight test article creates new types of network-based data flows between a test article and a telemetry ground station. The emerging integrated Network Enhanced Telemetry (iNET) Standard defines new, network-based data delivery protocols which can produce various network data flows. Augmenting existing Serial Streaming Telemetry (SST) data flows with these network-based data flows is crucial to enhancing current flight test capabilities. This paper briefly introduces the network protocols referenced in the iNET Standard and then identifies the various data flows generated by network-based components which comply with the iNET Standard. Several combinations of SST and TmNS data flows are presented and the enhanced telemetry capabilities provided by each combination are identified. Identifying time intervals of unused telemetry network bandwidth explicitly for reallocation to other test articles is also addressed.

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