A numerical methodology for the multi-objective optimization of the DI Diesel engine combustion

DI Diesel engine are widely used both for industrial and automotive applications due to their durability and fuel economy. Nonetheless, increasing environmental concerns force that type of engine to comply with increasingly demanding emission limits, so that, it has become mandatory to develop a robust design methodology of the DI Diesel combustion system focused on reduction of soot and NOx simultaneously while maintaining a reasonable fuel economy. In recent years, genetic algorithms and CFD three-dimensional combustion simulations have been successfully applied to that kind of problem. However, combining GAs optimization with actual CFD three-dimensional combustion simulations can be too onerous since a large number of calculations is usually needed for the genetic algorithm to converge, resulting in a high computational cost and, thus, limiting the suitability of this method for industrial processes. In order to make the optimization process less time-consuming, CFD simulations can be more conveniently used to generate a training set for the learning process of an artificial neural network which, once correctly trained, can be used to forecast the engine outputs as a function of the design parameters during a GA optimization performing a so-called virtual optimization. In the current work, a numerical methodology for the multi-objective virtual optimization of the combustion of an automotive DI Diesel engine, which relies on artificial neural networks and genetic algorithms, was developed.

Automotive diesel engine transient operation: modeling, optimization and control

Traditionally, the study of internal combustion engines operation has focused on the steady-state performance. However, the daily driving schedule of automotive engines is inherently related to unsteady conditions. There are various operating conditions experienced by (diesel) engines that can be classified as transient. Besides the variation of the engine operating point, in terms of engine speed and torque, also the warm up phase can be considered as a transient condition. Chapter 2 has to do with this thermal transient condition; more precisely the main issue is the performance of a Selective Catalytic Reduction (SCR) system during cold start and warm up phases of the engine. The proposal of the underlying work is to investigate and identify optimal exhaust line heating strategies, to provide a fast activation of the catalytic reactions on SCR. Chapters 3 and 4 focus the attention on the dynamic behavior of the engine, when considering typical driving conditions. The common approach to dynamic optimization involves the solution of a single optimal-control problem. However, this approach requires the availability of models that are valid throughout the whole engine operating range and actuator ranges. In addition, the result of the optimization is meaningful only if the model is very accurate. Chapter 3 proposes a methodology to circumvent those demanding requirements: an iteration between transient measurements to refine a purpose-built model and a dynamic optimization which is constrained to the model validity region. Moreover all numerical methods required to implement this procedure are presented. Chapter 4 proposes an approach to derive a transient feedforward control system in an automated way. It relies on optimal control theory to solve a dynamic optimization problem for fast transients. From the optimal solutions, the relevant information is extracted and stored in maps spanned by the engine speed and the torque gradient.

Estensione del game engine Unity per la generazione procedurale di ambienti per videogiochi

In questo elaborato viene descritto il lavoro svolto per sviluppare un generatore procedurale di ambienti per videogiochi, più propriamente definiti con il temine dungeon. Lo strumento creato viene integrato all'interno del game engine Unity ed è di carattere generale: può essere utilizzato per qualunque gioco che richieda una generazione procedurale di livelli.

Il sito web del Palio di San Donato: proposta di localizzazione e Search Engine Optimization

La presente tesi illustra e discute due attività legate all'ambito dei siti web, ovvero la localizzazione e l'ottimizzazione per i motori di ricerca (o SEO, dall'inglese "Search Engine Optimization"). Quest'ultima è un'attività mirata a permettere che i siti stessi ottengano un posizionamento migliore nella pagina dei risultati dei motori di ricerca e siano dunque più visibili agli utenti. Poiché la SEO prevede vari interventi sui siti web, alcuni dei quali implicano la manipolazione di codice HTML, essa viene spesso considerata come un'attività strettamente informatica. L'obiettivo della presente tesi, dunque, è quello di illustrare come i traduttori possano sfruttare le proprie competenze linguistiche per dedicarsi non soltanto alla localizzazione di siti web, ma anche alla loro ottimizzazione per i motori di ricerca. Per dimostrare l'applicabilità di tali tecniche è stato utilizzato come esempio pratico il sito web de "Il Palio di San Donato", un sito gestito dal Comune di Cividale del Friuli e finalizzato alla descrizione dell'omonima rievocazione storica cittadina. La tesi si compone di quattro capitoli. Nel primo capitolo vengono introdotti i principi teorici alla base della localizzazione di siti web, della SEO, della scrittura per il web e della traduzione per il settore turistico. Nel secondo capitolo, invece, viene descritto il sito del Palio di San Donato, esaminandone in particolare la struttura e i contenuti. Il terzo capitolo è dedicato alla descrizione del progetto di localizzazione a cui è stato sottoposto il sito in esame. Infine, il quarto capitolo contiene un breve commento relativo alle problematiche linguistiche, culturali e tecnologiche riscontrate durante il processo traduttivo e un elenco di strategie di SEO applicate a cinque pagine del sito web in esame, selezionate sulla base della possibilità di illustrare il maggior numero possibile di interventi di SEO attuabili dai traduttori.

Chemical composition modification of casting aluminium alloys for engine applications

The research activities were focused on evaluating the effect of Mo addition to mechanical properties and microstructure of A354 aluminium casting alloy. Samples, with increasing amount of Mo, were produced and heat treated. After heat treatment and exposition to high temperatures samples underwent microstructural and chemical analyses, hardness and tensile tests. The collected data led to the optimization of both casting parameters, for obtaining a homogeneous Mo distribution in the alloy, and heat treatment parameters, allowing the formation of Mo based strengthening precipitates stable at high temperature. Microstructural and chemical analyses highlighted how Mo addition in percentage superior to 0.1% wt. can modify the silicon eutectic morphology and hinder the formation of iron based β intermetallics. High temperature exposure curves, instead, showed that after long exposition hardness is slightly influenced by heat treatment while the effect of Mo addition superior to 0,3% is negligible. Tensile tests confirmed that the addition of 0.3%wt Mo induces an increase of about 10% of ultimate tensile strength after high temperature exposition (250°C for 100h) while heat treatments have slight influence on mechanical behaviour. These results could be exploited for developing innovative heat treatment sequence able to reduce residual stresses in castings produced with A354 modified with Mo.

Integrare Search Engine Optimization e Website usability al processo di localizzazione di un sito Web. Proposta di localizzazione dal francese all’italiano del sito del Parc de loisirs du Lac de Maine.

Ce mémoire a comme objectif de montrer le processus de localisation en langue italienne d’un site Internet français, celui du Parc de loisir du Lac de Maine. En particulier, le but du mémoire est de démontrer que, lorsqu’on parle de localisation pour le Web, on doit tenir compte de deux facteurs essentiels, qui contribuent de manière exceptionnelle au succès du site sur le Réseau Internet. D’un côté, l’utilisabilité du site Web, dite également ergonomie du Web, qui a pour objectif de rendre les sites Web plus aisés d'utilisation pour l'utilisateur final, de manière que son rapprochement au site soit intuitif et simple. De l’autre côté, l’optimisation pour les moteurs de recherche, couramment appelée « SEO », acronyme de son appellation anglais, qui cherche à découvrir les meilleures techniques visant à optimiser la visibilité d'un site web dans les pages de résultats de recherche. En améliorant le positionnement d'une page web dans les pages de résultats de recherche des moteurs, le site a beaucoup plus de possibilités d’augmenter son trafic et, donc, son succès. Le premier chapitre de ce mémoire introduit la localisation, avec une approche théorique qui en illustre les caractéristiques principales ; il contient aussi des références à la naissance et l’origine de la localisation. On introduit aussi le domaine du site qu’on va localiser, c’est-à-dire le domaine du tourisme, en soulignant l’importance de la langue spéciale du tourisme. Le deuxième chapitre est dédié à l’optimisation pour les moteurs de recherche et à l’ergonomie Web. Enfin, le dernier chapitre est consacré au travail de localisation sur le site du Parc : on analyse le site, ses problèmes d’optimisation et d’ergonomie, et on montre toutes les phases du processus de localisation, y compris l’intégration de plusieurs techniques visant à améliorer la facilité d’emploi par les utilisateurs finaux, ainsi que le positionnement du site dans les pages de résultats des moteurs de recherche.

A Decision-Tree-Based Approach to Smoke Spike Detection in a Heavy-Duty Diesel Engine

Smoke spikes occurring during transient engine operation have detrimental health effects and increase fuel consumption by requiring more frequent regeneration of the diesel particulate filter. This paper proposes a decision tree approach to real-time detection of smoke spikes for control and on-board diagnostics purposes. A contemporary, electronically controlled heavy-duty diesel engine was used to investigate the deficiencies of smoke control based on the fuel-to-oxygen-ratio limit. With the aid of transient and steady state data analysis and empirical as well as dimensional modeling, it was shown that the fuel-to-oxygen ratio was not estimated correctly during the turbocharger lag period. This inaccuracy was attributed to the large manifold pressure ratios and low exhaust gas recirculation flows recorded during the turbocharger lag period, which meant that engine control module correlations for the exhaust gas recirculation flow and the volumetric efficiency had to be extrapolated. The engine control module correlations were based on steady state data and it was shown that, unless the turbocharger efficiency is artificially reduced, the large manifold pressure ratios observed during the turbocharger lag period cannot be achieved at steady state. Additionally, the cylinder-to-cylinder variation during this period were shown to be sufficiently significant to make the average fuel-to-oxygen ratio a poor predictor of the transient smoke emissions. The steady state data also showed higher smoke emissions with higher exhaust gas recirculation fractions at constant fuel-to-oxygen-ratio levels. This suggests that, even if the fuel-to-oxygen ratios were to be estimated accurately for each cylinder, they would still be ineffective as smoke limiters. A decision tree trained on snap throttle data and pruned with engineering knowledge was able to use the inaccurate engine control module estimates of the fuel-to-oxygen ratio together with information on the engine control module estimate of the exhaust gas recirculation fraction, the engine speed, and the manifold pressure ratio to predict 94% of all spikes occurring over the Federal Test Procedure cycle. The advantages of this non-parametric approach over other commonly used parametric empirical methods such as regression were described. An application of accurate smoke spike detection in which the injection pressure is increased at points with a high opacity to reduce the cumulative particulate matter emissions substantially with a minimum increase in the cumulative nitrogrn oxide emissions was illustrated with dimensional and empirical modeling.

Performance and emissions testing of a small two stroke engine using mid-level ethanol blends

With the introduction of the mid-level ethanol blend gasoline fuel for commercial sale, the compatibility of different off-road engines is needed. This report details the test study of using one mid-level ethanol fuel in a two stroke hand held gasoline engine used to power line trimmers. The study sponsored by E3 is to test the effectiveness of an aftermarket spark plug from E3 Spark Plug when using a mid-level ethanol blend gasoline. A 15% ethanol by volume (E15) is the test mid-level ethanol used and the 10% ethanol by volume (E10) was used as the baseline fuel. The testing comprises running the engine at different load points and throttle positions to evaluate the cylinder head temperature, exhaust temperature and engine speed. Raw gas emissions were also measured to determine the impact of the performance spark plug. The low calorific value of the E15 fuel decreased the speed of the engine along with reduction in the fuel consumption and exhaust gas temperature. The HC emissions for E15 fuel and E3 spark plug increased when compared to the base line in most of the cases and NO formation was dependent on the cylinder head temperature. The E3 spark plug had a tendency to increase the temperature of the cylinder head irrespective of fuel type while reducing engine speed.

Reynolds-stress turbulence model in the KIVA code for engine simulation

A Reynolds-Stress Turbulence Model has been incorporated with success into the KIVA code, a computational fluid dynamics hydrocode for three-dimensional simulation of fluid flow in engines. The newly implemented Reynolds-stress turbulence model greatly improves the robustness of KIVA, which in its original version has only eddy-viscosity turbulence models. Validation of the Reynolds-stress turbulence model is accomplished by conducting pipe-flow and channel-flow simulations, and comparing the computed results with experimental and direct numerical simulation data. Flows in engines of various geometry and operating conditions are calculated using the model, to study the complex flow fields as well as confirm the model’s validity. Results show that the Reynolds-stress turbulence model is able to resolve flow details such as swirl and recirculation bubbles. The model is proven to be an appropriate choice for engine simulations, with consistency and robustness, while requiring relatively low computational effort.

Aerothermodynamic cycle analysis of a dual-spool, separate-exhaust turbofan engine with an interstage turbine burner

This study focuses on a specific engine, i.e., a dual-spool, separate-flow turbofan engine with an Interstage Turbine Burner (ITB). This conventional turbofan engine has been modified to include a secondary isobaric burner, i.e., ITB, in a transition duct between the high-pressure turbine and the low-pressure turbine. The preliminary design phase for this modified engine starts with the aerothermodynamics cycle analysis is consisting of parametric (i.e., on-design) and performance (i.e., off-design) cycle analyses. In parametric analysis, the modified engine performance parameters are evaluated and compared with baseline engine in terms of design limitation (maximum turbine inlet temperature), flight conditions (such as flight Mach condition, ambient temperature and pressure), and design choices (such as compressor pressure ratio, fan pressure ratio, fan bypass ratio etc.). A turbine cooling model is also included to account for the effect of cooling air on engine performance. The results from the on-design analysis confirmed the advantage of using ITB, i.e., higher specific thrust with small increases in thrust specific fuel consumption, less cooling air, and less NOx production, provided that the main burner exit temperature and ITB exit temperature are properly specified. It is also important to identify the critical ITB temperature, beyond which the ITB is turned off and has no advantage at all. With the encouraging results from parametric cycle analysis, a detailed performance cycle analysis of the identical engine is also conducted for steady-stateengine performance prediction. The results from off-design cycle analysis show that the ITB engine at full throttle setting has enhanced performance over baseline engine. Furthermore, ITB engine operating at partial throttle settings will exhibit higher thrust at lower specific fuel consumption and improved thermal efficiency over the baseline engine. A mission analysis is also presented to predict the fuel consumptions in certain mission phases. Excel macrocode, Visual Basic for Application, and Excel neuron cells are combined to facilitate Excel software to perform these cycle analyses. These user-friendly programs compute and plot the data sequentially without forcing users to open other types of post-processing programs.

Simulation of four stroke engine cycle for a 4 - valve pentroof engine in KIVA 3VR2

The main purpose of this project is to understand the process of engine simulation using the open source CFD code called KIVA. This report mainly discusses the simulation of the 4-valve Pentroof engine through KIVA 3VR2. KIVA is an open source FORTRAN code which is used to solve the fluid flow field in the engines with the transient 2D and 3D chemically reactive flow with spray. It also focuses on the complete procedure to simulate an engine cycle starting from pre- processing until the final results. This report will serve a handbook for the using the KIVA code.

Development of a technique for achieving an optimum BSFC for LAF engine

The reserves of gasoline and diesel fuels are ever decreasing, which plays an important role in the technological development of automobiles. Numerous countries, especially the United States, wish to slowly decrease their fuel dependence on other countries by producing in house renewable fuels like biodiesels or ethanol. Therefore, the new automobile engines have to successfully run on a variety of fuels without significant changes to their designs. The current study focuses on assessing the potential of ethanol fuels to improve the performance of 'flex-fuel SI engines,' which literally means 'engines that are flexible in their fuel requirement.' Another important area within spark ignition (SI) engine research is the implementation of new technologies like Variable Valve Timing (VVT) or Variable Compression Ratio (VCR) to improve engine performance. These technologies add more complexity to the original system by adding extra degrees of freedom. Therefore, the potential of these technologies has to be evaluated before they are installed in any SI engine. The current study focuses on evaluating the advantages and drawbacks of these technologies, primarily from an engine brake efficiency perspective. The results show a significant improvement in engine efficiency with the use of VVT and VCR together. Spark ignition engines always operate at a lower compression ratio as compared to compression ignition (CI) engines primarily due to knock constraints. Therefore, even if the use of a higher compression ratio would result in a significant improvement in SI engine efficiency, the engine may still operate at a lower compression ratio due to knock limitations. Ethanol fuels extend the knock limit making the use of higher compression ratios possible. Hence, the current study focuses on using VVT, VCR, and ethanol-gasoline blends to improve overall engine performance. The results show that these technologies promise definite engine performance improvements provided both their positive and negative potentials have been evaluated prior to installation.

Analysis of a novel waste heat recovery mechanism for an I.C. engine

Typical internal combustion engines lose about 75% of the fuel energy through the engine coolant, exhaust and surface radiation. Most of the heat generated comes from converting the chemical energy in the fuel to mechanical energy and in turn thermal energy is produced. In general, the thermal energy is unutilized and thus wasted. This report describes the analysis of a novel waste heat recovery (WHR) system that operates on a Rankine cycle. This novel WHR system consists of a second piston within the existing piston to reduce losses associated with compression and exhaust strokes in a four-cycle engine. The wasted thermal energy recovered from the coolant and exhaust systems generate a high temperature and high pressure working fluid which is used to power the modified piston assembly. Cycle simulation shows that a large, stationary natural gas spark ignition engine produces enough waste heat to operate the novel WHR system. With the use of this system, the stationary gas compression ignition engine running at 900 RPM and full load had a net increase of 177.03 kW (240.7 HP). This increase in power improved the brake fuel conversion efficiency by 4.53%.

Investigation of using waste engine oil blended with reclaimed asphalt materials to improve pavement recyclability

With the increasing importance of conserving natural resources and moving toward sustainable practices, the aging transportation infrastructure can benefit from these ideas by improving their existing recycling practices. When an asphalt pavement needs to be replaced, the existing pavement is removed and ground up. This ground material, known as reclaimed asphalt pavement (RAP), is then added into new asphalt roads. However, since RAP was exposed to years of ultraviolet degradation and environmental weathering, the material has aged and cannot be used as a direct substitute for aggregate and binder in new asphalt pavements. One material that holds potential for restoring the aged asphalt binder to a usable state is waste engine oil. This research aims to study the feasibility of using waste engine oil as a recycling agent to improve the recyclability of pavements containing RAP. Testing was conducted in three phases, asphalt binder testing, advanced asphalt binder testing, and laboratory mixture testing. Asphalt binder testing consisted of dynamic shear rheometer and rotational viscometer testing on both unaged and aged binders containing waste engine oil and reclaimed asphalt binder (RAB). Fourier Transform Infrared Spectroscopy (FTIR) testing was carried out to on the asphalt binders blended with RAB and waste engine oil compare the structural indices indicative of aging. Lastly, sample asphalt samples containing waste engine oil and RAP were subjected to rutting testing and tensile strength ratio testing. These tests lend evidence to support the claim that waste engine oil can be used as a rejuvenating agent to chemically restore asphalt pavements containing RAP. Waste engine oil can reduce the stiffness and improve the low temperature properties of asphalt binders blended with RAB. Waste engine oil can also soften asphalt pavements without having a detrimental effect on the moisture susceptibility.

Implementation of a Variable Compression Ratio Mechanism in a Four Cylinder Engine

Ever since the invention of the internal combustion engine, generating more power and achieving better efficiency has been a major goal for the designers. Variable compression ratio technology is way to achieve those goals. This paper will discuss the method of varying the compression ratio of an inline 4-cylinder engine through the use of a 4-bar linkage and gear mechanism. This mechanism was proven to easily vary the compression ratio of the engine and shows promise of becoming a technology used for future engine designer.