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Nowadays, around 80% to 90% of the international trade is made by sea, and the vast majority of the large merchant ships are powered by means of low-speed two-stroke diesel engines. Currently, gas turbines have only found niche markets in certain marine applications -such as the military or fast ferries, in which reduced size, mass, noise and vibration levels of the power plant are of paramount importance-, but their capability for entering the sector of the large cargo vessels (containers, bulk carriers, etc.) remains unexplored. Main disadvantages for the gas turbines to become a viable option for powering these ships are the very high thermal efficiency and extremely low running costs that the large diesel engines actually offer. However, as long as the current trend continues, diesel power plants are likely to lose one of their major advantages -i.e. their low operating costs- due to the ongoing regulations regarding ship emissions (IMO's MARPOL 73/78 Annex VI) and the severe reduction in the established limits for Sulphur contents in fuels for marine applications. In such a scenario, in which emissions from ships are relentlessly being cut down lower and lower, diesel engines will have to move to more expensive distillate fuels, likely equalising their fuel prices with the gas-turbine-based power plants and, therefore, opening a potential window for the latter to enter the market. Hence, the main question posed at this point would be: given the expected equalisation in fuel prices between the gas turbines and the diesel engines, is it possible to devise an advanced gas turbine-based power plant that could outcompete the low-speed two-stroke diesel engines as prime mover for marine commercial applications? Working with this hypothesis of fuel prices no longer posing a competitive advantage for diesel engines, and making the simplifying assumption (as a sensible first-order approach to the problem) that the targeted marine applications spend most of their time at cruise speed -i.e. with the prime mover operating very close to its design point-the overall thermal efficiency at nominal conditions will be the main driving parameter to carry out the comparative assessment among the different power plants considered herein. The aim of this research is, thus, to investigate if and which sort of advanced gas-turbine-based power plants could be able to deliver thermal efficiencies high enough to outperform modern diesel engines in this regard, at least at design-point operation. The research comprises two markedly different phases: in phase one of this project, a wide range of candidate gas-turbine-based power plants are proposed and parametrically optimised for maximum thermal efficiency at design point, so that their relative merits against one another can be established consistently and the few most promising cycles can be downselected for further research; in phase two, these few downselected candidates will be physically characterised, carrying out preliminary size and mass estimations of the whole prime mover, along with some acquisition costs assessment. The results presented in this thesis demonstrate the great potential of certain advanced thermodynamic cycles, still based on a gas turbine as the core of the power plant, to achieve outstanding levels of performance at design point, effectively outcompeting the diesels in this regard by a good margin, potentially between 5 and 10 percentage points. In particular, the evaporative gas turbines and the combined-cycle power plants were the most promising candidates analysed, yielding thermal efficiencies at design point in the surrounds of 60%-65%. As it will be shown, these advanced gas turbine-based power plants are, in general, comparable in size to the diesel engines, but can mean huge reductions in the overall uninstalled dry mass of the prime mover. Despite the acquisition costs being significantly higher for the gas turbines, the great potential savings in fuel consumption - because of the higher thermal efficiencies- could make out of these advanced gas-turbine-based power plants a cost-effective solution in the long run for powering large merchant ships.

Heat generation by commonly used systems and components, such as the large batteries used for energy storage, powerful instrumentation in computing, and advanced HVAC and climate control systems, has continued to increase and is further augmented by technological advancement. Assuming progress continues, the research of heat transfer efficiency remains a meaningful and worthwhile endeavor. This study explores possible ways to increase the effectiveness of heat transfer based on natural convection for systems at relatively low temperatures, which increases the range of applications for which it can be applied. It is hypothesized that the high energy density and high thermal conductivity of liquid metals and the effects of vertical partitions on flow organization in a fluid cavity can positively impact the heat transfer rate of a convective cell. The hypothesis is explored for a geometry of a cylindrical cavity with a single partition using Ansys Fluent CFD simulations. The aspect ratio of the cylinder, the Rayleigh number of the convective fluid flow, and the gap height between the top and bottom cylinder surfaces and a partition are considered as factors of a parametric optimization study. The results show manyfold enhancement of the heat transfer rate by a partition and indicate a strong potential in heat transfer applications.

Microencapsulated Phase Change Materials (PCMs) were included in air lime rendering mortars in order to improve the thermal comfort of the inhabitants and the energy efficiency of buildings of the Architectural Heritage under the premises of mínimum intervention and maximum compatibility. Three different PCMs were tested and directly added during the mixing process to fresh air lime mortars in three different percentages: 5, 10 and 20 wt. %. Some chemical additives were also incorporated to improve the final performance of the renders: a starch derivative as an adhesion booster; metakaolin as pozzolanic addition to shorten the setting time and to increase the final strength; anda polycarboxylated ether as a superplasticizer to adjust the fluidity of the fresh renders avoiding an excess of mixing water. The specific heat Cp, the enthalpy ti.H ascribed to the phase change and the melting temperature of the PCMs were determined by Differential Scanning Calorimetry (DSC). The capacity of the renders to store/release heat was demonstrated at a laboratory scale. The favourable results proved the effect of these PCMs with respect to the thermal performance of these rendering mortars, offering a promising way of enhancement of the thermal efficiency of building materia Is of the Cultural Heritage.

Compression-ignition (CI) engines, also known as “diesel” engines, can produce higher thermal efficiency (TE) than spark-ignition (SI) engines, which allows them to emit less carbon dioxide (CO2) per unit of energy generated. Unfortunately, in practice the TE of CI engines is limited by the need to maintain sufficiently low emissions of nitrogen oxides (NOx) and soot. This problem can be mitigated by operating CI engines in dual-fuel modes with port fuel injection (PFI) of gasoline supplementing the direct injection (DI) of diesel fuel. Several strategies for doing this have been introduced in recent years, but these operating modes are usually studied individually at discrete conditions. This thesis introduces a classification system for dual-fuel CI modes that links together several previously studied modes across a continuous two-dimensional diagram. The combustion modes covered by this system include the standard modes of conventional diesel combustion (CDC) and conventional dual-fuel (CDF); the well-explored advanced combustion modes of HCCI, RCCI, PCCI, and PPCI; and a relatively unexplored combustion mode that is herein titled “Piston-split Dual-Fuel Combustion” or PDFC. The results show that dual-fuel CI engines can simultaneously increase TE and lower NOx and/or soot emissions at high loads through the use of Partial HCCI (PHCCI), despite an increase in emissions of carbon monoxide (CO) and unburnt hydrocarbons (UHC). At low loads, PHCCI is not possible, but either PDFC or RCCI can be used to further improve NOx and/or soot emissions, albeit at slightly lower TE and still higher emissions of CO and UHC. This multi-mode strategy of PHCCI at high loads and PDFC or RCCI at low loads is particularly useful when low engine-out NOx emissions are required.

Amongst all the attempts to fulfill the goal of enhancing thermal efficiency and decreasing pollutant emissions in a combustion system, Homogeneous Combustion (HC), or Flameless Oxidization (FLOX) or Moderate Intense Low-oxygen Dilution (MILD) Combustion is thought to be one of the most promising technologies. HC is achieved by strong exhaust gas recirculation, where reactants are intensely diluted and hence reactions occur volumetrically without a visible flame front. Relative to the conventional counterpart, HC increases the in-furnace thermal uniformity and efficiency, and simultaneously suppresses NOx emissions. Thermal radiation enhancement can be one possible approach to further improve the thermal performance of a HC at no or little expense of pollutant emissions, especially when applied in the heating facilities such as industrial furnace. In practical heating systems where thermal radiation is pursued, such as industrial furnace, certain level of soot production in the combustion zone is favored if adequate aftertreatment is available to limit the soot emissions in the exhaust under the regulated values. The present study focuses on the possibility of thermal radiation enhancement through soot formation under Homogeneous Combustion regime through experimental tests implemented in a large-scale furnace (0.84 m in diameter and 1.4 m in length), which can provide direct insights to the development of practical industrial heating systems. The possibility of sooty HC is studied first. Experimental tests, under various concentrations of propane or ethylene in the fuel, oxygen enrichment level and process temperature, are implemented. Results show that sooty HC can be achieved under the conditions of: 1) fuel rich combustion with equivalence ratio of 1.1; 2) fuel mixture with ethylene while the mass fraction of ethylene should be maintained below 20%; 3) process temperature over 1400 K. The characteristics of sooty HC is studied next. Experimental tests under the sooty HC conditions are implemented to measure the soot content (by laser extinction), the thermal radiation heat flux (by a Schmidt-Boelter Gauge), the thermal field (by in-situ temperature probe), the furnace efficiency (by a cooling plate equipped with water jacket) and the pollutant emissions (by various gas analyzers). Results showed an increasing trend in the in-furnace soot content with increasing ethylene content in the fuel. A close-to-linear relationship is found between the measured radiation heat flux and the soot volume fraction in sooty HCs. However, in the test runs with 20% ethylene in the fuel, visible flames can be found and hence this can no longer be identified as sooty HC. To help understand the flow field of the Homogeneous Combustion in the present study, numerical modeling for the turbulent reacting flows in the HC is implemented with CFD simulation. It is found that increasing the air jet momentum will help in achieving Homogeneous Combustion. The Homogeneous Combustion has a large tolerance to the unbalanced air jet distribution while if the disturbance is too large, local flames can appear. The thermal NO is almost negligible in Homogeneous Combustion while the prompt NO can be the most important path in the current fuel rich condition. The oxidation of NO to NO2 is a significant contribution to the consumption of NO while the reduction of NO2 feeds back as a source of NO production.

Homogeneous Charge Compression Ignition (HCCI), exhibits many fundamentally attractive thermodynamic characteristics. These traits, along with lean charge and low combustion temperatures, generally act to increase thermal efficiency relative to competing spark and/or compression ignition strategies. However, HCCI's extreme sensitivity to in-cylinder thermal conditions, place limits on practical implementation. Thus, at low temperatures, combustion remains incomplete limiting cycle efficiency while increasing emissions. In contrast, the introduction of thermal barrier coatings (TBCs) to in-cylinder surfaces has been shown to fundamentally alter gas-wall interactions. The work in this dissertation explores HCCI/TBC synergies. Both experimental and analytical pathways are explored, attempting to illuminate the impact(s) of coatings on engine heat transfer and combustion metrics. Efforts to correlate TBC thermophysical properties and surface phenomena with HCCI performance and emissions are also explored. Finally, methods are proposed to evaluate the TBC-gas interaction as it relates to thermal stratification of the in-cylinder charge. The present work seeks to identify, and eventually quantify HCCI/TBC synergies. A specific research effort is developed, attempting to illuminate the impact(s) of TBCs on fundamental HCCI combustion metrics. Efforts to correlate TBC thermophysical properties and surface phenomena with HCCI performance and emissions are also proposed. Analysis is enabled through complimentary analytic and experimental pathways - which includes specialized solution methodology and experimental hardware. Combined, these tools enable a more complete qualitative assessment of thermal barrier coating's impact on engine performance and emissions metrics, heat loss at the wall, and ultimately thermal stratification of the in-cylinder temperature field.

Engine efficiency improvement can help combustion powertrains, which include conventional, hybrid, and plug-in hybrid systems, to meet the strict emissions standards and the increasing demand from customers for performance, drivability, and affordability of vehicles. Cooled exhaust gas recirculation (EGR) can reduce fuel consumption and NOx emissions of gasoline engine systems while keeping the capability of using a conventional three-way catalyst for effective emissions reduction. However, too much EGR would lead to combustion instability and misfire. This thesis identified opportunities to improve efficiency in internal combustion engines by high EGR dilution SI combustion by using thermodynamics-based approaches. This goal has been achieved by using fuel reforming in a thermodynamically-favorable way. Exhaust heat was used to drive endothermic reforming reactions to increase the chemical fuel energy to attain thermochemical recuperation (TCR), a form of waste heat recovery, with robust integrated systems and the regular gasoline. Three strategies for fuel reforming, along with the unique designs of corresponding integrated engine systems, a committed in-cylinder reformer, a catalytic EGR-loop reforming system, and fuel reforming by fuel injection during Negative Valve Overlap (NVO), have been proposed and investigated with unique engine system setups and corresponding experimental and simulation research. The concept and the system to use one cylinder to serve as a committed fuel reformer without spark ignition is first demonstrated. The committed in-cylinder reformer engine system achieves 8% brake thermal efficiency improvement through EGR and cylinder deactivation effects, even though there is low fuel conversion. The novel catalytic EGR-loop reforming integrated engine system was designed and tested. The experiments and thermodynamic equilibrium calculations reveal that the suppression of H2 and CO caused by the enthalpy limitation could be countered by adding small amounts of O2 by running one-cylinder lean. As much as 15 volume % H2 at the catalyst outlet is produced when the fuel and air equivalence ratio is between 4 and 7 under quasi-steady-state conditions. It is also found that this catalytic EGR reforming strategy makes it possible to sustain stable combustion with a volumetric equivalent of 45%–55% EGR, compared to a baseline EGR dilution limit which is under 25%. This catalytic EGR-loop reforming strategy results in a decrease of more than 8% in fuel consumption with significant potentials for even higher brake thermal efficiency. This novel design also opens up a new control method to control the amount of fuel reforming and the fraction of the partial oxidation reaction and steam reforming reaction by adjusting the lambda value of the cylinder which is running lean. Through this design, the engine is serving as an active system, which can also be adapted to respond to the needs of the passive catalyst system so that even better more significant benefit can be achieved. The results demonstrate fuel injection during NVO can extend the dilution limit, improve brake specific fuel consumption (BSFC), and reduce CO and NOx emissions on the engine modified with the capability of variable intake and exhaust valve timing and higher compression ratio. A comprehensive comparison of different reforming strategies for engine application and analysis of critical factors contributing to the performance of integrated fuel reforming engine systems is also provided. The research of this dissertation has demonstrated new pathways and scientific outcomes for technology development of internal combustion engine powertrain systems that can operate significantly more efficiently and cleanly.

The common practice in corbel design is to block out the insulation in order to provide a solid concrete area at the corbel location. This connection practice results in thermal bridging, which significantly reduces the energy performance of the panel. For example, the PCI Design Handbook indicates that the reduction in thermal resistance caused by a solid part with an area equal to 9% of the total panel surface area is as high as 42%. This paper presents a discussion of a new concept for corbel design of insulated wall panels with the thermal break totally preserved. Two different designs are presented. The structural capacity of the two connections was determined analytically and verified experimentally. The results of the research are encouraging. It is shown that a corbel is feasible to support the reaction of a 60 ft double tee on a 3-4-3 inch (total 10 in. thick) insulated panel. The required capacity of 42,000 pounds is shown to be exceeded by a significant margin. The reinforcement is relatively light and the precast production is relatively simple. Example design calculations and reinforcement details as well as the experimental results of seven full scale specimens will be covered. Advisers: George Morcous and Maher K. Tadros