Based on the GT-Power software, an engine cycle simulation for a biodiesel fueled direct injection compression ignition engine was developed and used to study its performance and emission characteristics. The major objectives were to establish the engine model for simulation and then apply the model to study the biodiesel fueled engine and compare it to a petroleum-fueled engine. The engine model was developed corresponding to a 4.5 liter, John Deere 4045 four-cylinder diesel engine. Submodels for flow in intake/exhaust system, fuel injection, fuel vaporization and combustion, cylinder heat transfer, and energy transfer in a turbocharging system were combined with a thermodynamic analysis of the engine to yield instantaneous in-cylinder parameters and overall engine performance and emission characteristics. At selected engine operating conditions, sensitivities of engine performance and emission on engine load/speed, injection timing, injection pressure, EGR level, and compression ratio were investigated. Variations in cylinder pressure, ignition delay, bsfc, and indicated specific nitrogen dioxide were determined for both a biodiesel fueled engine and a conventional diesel fueled engine. Cylinder pressure and indicated specific nitrogen dioxide for a diesel fueled engine were consistently higher than those for a biodiesel fueled engine, while ignition delay and bsfc had opposite trends. In addition, numerical study focusing on NOx emission were also investigated by using 5 different NO kinetics. Differences in NOx prediction between kinetics ranged from 10% to 65%.

No description available.

Use of an induced blanket reactor (IBR) to break down organic matter into methane is a financially attractive method to reduce the environmental impact of animal or industrial waste. In order to better understand the biological processes involved with the conversion of waste to biogas by an IBR, it is necessary to gain a better understanding of the microorganisms and their roles in the reactor. Molecular techniques based on the isolation of 16S rDNA were used in order to avoid the limitations posed by conventional culture-based techniques. Total DNA was extracted and amplified using universal primers specific to eubacteria and archaea with the purpose of identifying the dominant microorganisms in the IBR. The amplified DNA was separated based on its sequence composition by denaturing gradient gel electrophoresis (DGGE). Several bands were then excised, cloned, and sequenced, in order to characterize the phylogenetic affiliation of many of the microorganisms and create a useful molecular fingerprint. By using this approach, close relatives of several microorganisms that are typical in anaerobic digestion have been identified, including species of Clostridium, Flavobacterium, Bacteroides, Spirochaeta, Methanobrevibacter, and Methanosarcina. Several species were also identified whose role in the reactor is not completely understood, consisting of relatives of Dehalococcoides, Planctomyces, Aequorivita, and Sedimentibacter species. The information obtained in this project may enable refinements that promote desirable reactions and enhance reactor efficiency.

No description available.

Ammonia has emerged as an attractive potential hydrogen carrier due to its extremely high energy density (hydrogen density), ease of storage and transportation as a liquid, and carbon-free nature. Direct utilization of ammonia in high-temperature solid oxide fuel cells (SOFCs) has been demonstrated over the past decade. Concurrence of in situ endothermic ammonia decomposition and exothermic electrochemical hydrogen oxidation permit efficient heat integration. In this study, the experimental analyses of axial temperature and concentration profiles along the tubular SOFC (t-SOFC) fed directly with ammonia are performed to investigate the coupled ammonia decomposition and hydrogen oxidation reactions as well as the effect of polarization. Fast ammonia decomposition over the Ni catalyst is evident at the inlet of t-SOFC and complete ammonia conversion is confirmed above 600ºC. It is found that direct ammonia-fueled t-SOFC and an equivalent hydrogen-nitrogen fueled t-SOFC provide identical performances. With 100 SCCM of ammonia fuel feed, a maximum power of 12.2 W and fuel utilization of 81% are obtained at 800ºC in a t-SOFC with active area of 32 cm2. The temperature and concentration profiles validate that the efficient heat integration inside ammonia-fueled t-SOFC is feasible if t-SOFC is operated at the temperature of 700ºC and below. The 23-hour performance test and SEM-EDS images of the fresh and used Ni-YSZ cermet surfaces confirm uniform performance and good durability of ammonia t-SOFC.

No description available.

Rapporté à la tonne de fret, le trafic maritime est un mode de transport relativement « propre ». Néanmoins, par l’intensification des échanges mondiaux, sa part dans les émissions de Gaz à Effet de Serre (GES) au niveau mondial est appelée à augmenter. Conscients des effets néfastes associés aux GES, les pays membres des nations unies, via l’organisation maritime internationale, imposent le cadre réglementaire pour que ce secteur, vital dans une économie mondialisée, demeure écologiquement acceptable. Des objectifs ambitieux sont établis à court (2020) et moyen terme (2050). Or, d’après l’hypothèse faible de Porter, fixer des objectifs environnementaux sans imposer les moyens à mettre en oeuvre favorise l’innovation. Aussi, dans l’industrie du « shipping », les solutions fleurissent au premier rang desquelles figure l’emploi du Gaz Naturel Liquéfié (GNL) en tant que combustible. D’un point de vue thermodynamique, les inévitables infiltrations thermiques à travers les parois des réservoirs cryogéniques entraînent une variation de la pression dans le réservoir et des fluctuations de la qualité du gaz à l’admission moteur. Selon le schéma d’exploitation navire, ces deux phénomènes impactent significativement la pertinence de l’option GNL. En réponse, cette thèse propose un ensemble de modèles 0D pour, à partir d’un profil opérationnel, évaluer :1. l’évolution de la pression dans les réservoirs ;2. l’évolution de la qualité du gaz à l’admission moteur.Dans une première partie, des modèles sont proposés pour simuler les infiltrations thermiques à travers le réservoir, l’évaporation du GNL, son vieillissement (altération des propriétés du gaz par évaporation différenciée des composés) et l’évolution du taux de méthane à l’admission moteur. Puis, les modèles sont assemblés à travers une étude de cas apportée par un acteur du transport maritime. / In proportion to the ton of cargo, shipping is a relatively “clean” transportation mode. Nevertheless, due to global trade intensification, its share in the global greenhouse gas (GHG) emissions should increase. Aware that GHG adverse effects are a major concern for humanity, united nation member states impose, via the international maritime organization, a regulatory framework so that this vital sector in a global economy remains sustainable. Short (2020) and medium (2050)-term goals are set. According to the weak version of Porter’s hypothesis, strict environmental regulations encourage innovations. Hence, in the shipping industry solutions flourish among which the use of Liquefied Natural Gas (LNG) as a fuel. On a thermodynamic basis, the unavoidable heat leaks into the cryogenic tanks cause variations of the tank pressure and the natural gas quality at engine inlet. Depending on the ship’s operational profile, those two phenomena will impact significantly the LNG as a fuel option relevance. One major bottleneck slowing the uptake of LNG as a marine fuel is the lack of methods and models to perform, at a concept design level, the feasibility study. In response, this thesis proposes 0D models to assess from the operational profile:1. the tank pressure evolution;2. the gas quality evolution at engine inlet.In the first part, models are proposed to simulate heat leaks into the tanks, LNG vaporization, ageing (the alteration of natural gas thermophysical properties by a differentiate vaporization of its compounds) and methane number evolution at engine inlet. Then, the models are put together and applied on a case study. The ship concept is proposed by a freight company.

No description available.

The EU waste hierarchy includes energy recovery facilities where waste is used as fuel in combined heat- and powerplants. When waste is incinerated can the thermal energy be used in for example, district heating networks and or electricity generation. The purpose of the degree project is to make a pre-study of Heat Management's system solution HISS, optimization of steam soot blowing at Mälarenergi's waste boiler. Waste is a heterogeneous fuel that typically contains a variety of substances such as alkali, chlorine and heavy metals that often contribute to fouling on heat transfer surfaces. These coatings reduce the efficiency of heat transferring surfaces such as superheaters. Cleaning by soot blowing using steam is done at regular intervals to maintain efficiency. Superheater cleaning on the Block 6 is done by retractable rotating soot blowers equipped with a nozzle from where steam is sprayed out at pressure of 25 bar. The blowers are inserted one at a time in a sequence, which means that they wait for the previous blower before the next one can enter. Steam is taken from the main process, which leads to reduction in load on the turbine and causes wear during the sweeping process due to the high impact force. This can lead to erosive damage and thinning of the material on the tubes, thus shortening the lifespan of the superheaters. The optimisation adjusts the soot sequence so that full steam pressure is used only in one direction of travel of the lance, this allows an overlapping soot sequence to be used and thus halves the time required for sooting. Analysis of shorter sooting time and reduced steam consumption based on production data and case studies has led to the following results. The energy consumption of the auxiliary power is reduced by 14.25 MWh per sweeping sequence and 7 115.5 MWh annually. The turbine can produce 2.51 MWh more electricity per sweeping as the time it runs at reduced load is reduced, totalling 1 254.39 MWh in one year. 24.03 tonnes of steam are saved per sweeping and 12 003 tonnes in one year. Payback time for the optimisation is 1.01 years based on an average spot price from Mälarenergi's budgeting from last year. Considering current electricity prices could the payback time be further reduced. The conclusion from the pre-study is that the optimisation as the investment is economically viable and has other positive benefits such as: steadier steam flow and reduced pressure surges. Wear and tear on superheaters are reduced as they are only sprayed with high pressure once instead of twice per sweeping sequence. / I EU:s avfallshierarki ingår energiåtervinningsanläggningar där avfall används som bränsle i förbränningsanläggningar. Vid förbränning utav avfall så kan den utvunna termiska energin användas exempelvis i fjärrvärmenät och- eller generering utav el. Examensarbetets syfte är att göra en förstudie på Heat managements systemlösning HISS, optimering utav ångsotning på Block 6 som är Mälarenergis avfallspanna. Avfall är ett heterogent bränsle som typiskt innehåller en mängd olika ämnen som alkali, klor och tungmetaller som ofta bidrar till att beläggningar bildas på värmeöverförningsytor. Dessa beläggningar försämrar ytors värmeöverförningsverkningsgrad på till exempel överhettare. Rengöring i form av ångsotning görs i jämna intervall för att hålla verkningsgraden uppe. Sotning av överhettare på Block 6 skes av en utdragbar, roterande sotlans utrustad med en dysa där ånga sprutas ut med 25 bars tryck. Lansarna körs in en åt gången i en sekvens vilket innebär att dem väntar på föregående lans innan nästa kan köras. Ångan som används tas från huvudprocessen vilket medför reducerad last på turbinen och dessutom uppstår slitage vid sotningen ty den höga anslagskraften. Detta kan leda till erosiva skador och förtunning utav godset på tuberna och således förkortas livslängden på överhettarna. Optimeringen justerar sot sekvensen så att fullt ångtryck används bara i ena färdriktningen av lansen, detta möjliggör att en överlappande sotsekvens kan användas och på så vis halveras tidsåtgången för sotningen. Analysen utav kortare sottidsåtgång samt minskad ångförbrukning baserat på produktionsdata hämtad från styrsystemet 800xA samt fallstudier har mynnat ut i följande resultat. Hjälpkraftens energianvändning minskas med 14,25 MWh per sotningssekvens och årligen 7 115,5 MWh. Turbinen kan producera 2,51 MWh mer el vid varje sotning då tiden som den körs med reducerad last blir kortare, totalt på ett år blir det 1 254,39 MWh. Vid varje sotning sparas 24,03 ton ånga och på ett år 12 003 ton. Återbetalningstiden för optimeringen blir 1,01 år baserat på ett medelspotpris från Mälarenergis budgetering från förra året. Med hänsyn till dagens elpriser förkortas återbetalningstiden ytterligare.   Förstudien rekommenderar optimeringen då dels är investeringen lönsam rent ekonomiskt, dels medför den andra positiva fördelar. Optimeringen med överlappande sotning skapar ett jämnare ångflöde, det reducerar tryckstötar som är skadliga. Slitage på överhettartuber minskas då dem bara besprutas med högt tryck en gång i stället för två gånger per sotningssekvens. Behovsstyrd sotning skulle kunna implementeras upp till 3 gånger per dygn utan att det skulle kosta mer mot dagsläget där man stora 1,5 gånger per dygn.

Homogeneous Charge Compression Ignition (HCCI) combustion is an alternative combustion mode in which the fuel is homogeneously mixed with air and is auto-ignited by compression. Due to charge homogeneity, this mode is characterized by low equivalence ratios and temperatures giving simultaneously low nitric oxide (NOx) and soot in diesel engines. The conventional problem of NOx-soot trade-off is avoided in this mode due to absence of diffusion combustion. This mode can be employed at part load conditions while maintaining conventional combustion at high load thus minimizing regulatory cycle emissions and reducing cost of after-treatment systems. The present study focuses on achieving this mode in a turbocharged, common rail, direct injection, four-cylinder, heavy duty diesel engine. Specifically, the work involves a combination of three-dimensional CFD simulations and experiments on this engine to assess both traditional and novel strategies related to fuel injection. The first phase of the work involved a quasi-dimensional simulation of the engine to assess potential of achieving HCCI. This was done using a zero-dimensional, single-zone HCCI combustion model with n-heptane skeletal chemistry along with a one-dimensional model of intake and exhaust systems. The feasibility of operation with realistic knock values with high EGR rate of 60% was observed. The second aspect of the work involved three-dimensional CFD simulations of the in-cylinder process with wall film prediction to evaluate injection strategies associated with Early Direct Injection (EDI). The extended Coherent Flame Model-3Zone (ECFM-3Z) was employed for combustion simulation of conventional CI and EDI, and was validated with experimental in-cylinder pressure data from the engine. A new Uniformity Index (UI) parameter was defined to assess charge homogeneity. Results showed significant in-homogeneity and presence of wall film for EDI. Simulations were conducted to assess improvement of charge homogeneity by several strategies; narrow spray cone angle, injection timing, multiple injections, intake air heating, Port Fuel Injection (PFI) as well as combination of PFI and EDI. The maximum UI achieved by EDI was 0.78. The PFI strategy could achieve UI of 0.95; however, up to 50% of fuel remained trapped in the port after valve closure. This indicated that except EDI, none of the above-mentioned strategies could help achieve the benefits of the HCCI mode. The third part of the work involved engine experimentation to assess the EDI strategy. This strategy produced lower soot than that of conventional CI combustion with very short combustion duration, but led to high knock and NOx which is attributed to pool fire burning phenomenon of the wall film, as confirmed by CFD. An Optimized EDI (OptimEDI) strategy was then developed based on results of CFD and Design of Experiments. The Optim EDI consisted of triple injections with split ratio of 41%-45%-14% and advancing the first injection. This strategy gave 20% NOx and soot reduction over the conventional CI mode. Although this strategy gave encouraging results, there was a need for more substantial reduction in emissions without sacrificing efficiency. Hence, a novel concept of utilizing air-assisted Injection (AAI) into the EGR stream was employed, as this implied injecting very small droplets of fuel into the intake which would have sufficient residence time to evaporate before reaching the cylinder, thereby enabling HCCI. The fourth and final part of the work involved engine experimentation with AAI, and combination of OptimEDI with AAI. Results with 20% EGR showed that 5 to 10% of AAI gave further reduction in NOx but not in soot. With experiments involving 48% EGR rate, there was soot reduction of 75% due to combined AAI-EDI. NOx was negligible due to the high EGR rate. Thus, the significant contribution of this work is in proving that combining AAI with EDI as a novel injection strategy leads to substantial NOx and soot reduction.