Analisi energetica al variare dello state of charge di propulsori ibridi e plug-in operanti nel ciclo WLTP con propulsore termico a punto fisso stechiometrico

Il presente lavoro propone la stesura di un codice in ambiente MATLAB per l'analisi energetica di powertrain ibridi operanti nel ciclo WLTP con il particolare funzionamento del motore termico benzina a punto fisso stechiometrico. Nello specifico, il codice prende dei dati in input tramite un'interfaccia grafica ed avvia una simulazione, i cui risultati principali corrispondono ad emissioni di anidride carbonica per chilometro percorso ed ai chilometri percorsi con un litro di carburante. Queste sono le due grandezze che questo lavoro si prefigge di ottimizzare, dalle quali proviene la scelta del particolare funzionamento del motore termico. Sono state implementate due differenti strategie di controllo, una generale ed una più particolare. La simulazione con la strategia generale è stata applicata a tre differenti scenari reali, con le caratteristiche tecniche di tre veicoli realmente esistenti che vengono inserite nell'interfaccia grafica. I risultati provenienti da queste simulazioni sono stati poi analizzati e discussi nel dettaglio, anche con l'ausilio di grafici a supporto della spiegazione. La strategia di controllo particolare non è stata applicata a scenari reali ma ha portato alla definizione di una ipotetica architettura di powertrain ibrido, alla quale la sopracitata strategia si adatta al meglio. Dopo aver proposto miglioramenti e possibili ulteriori sviluppi di questo lavoro, sono state tratte le conclusioni generali, allargando il tutto al contesto più ampio in cui si va ad inserire.

ICE Emissions Estimation through Machine-learning techniques to support real-world R&D experiments

The emissions estimation, both during homologation and standard driving, is one of the new challenges that automotive industries have to face. The new European and American regulation will allow a lower and lower quantity of Carbon Monoxide emission and will require that all the vehicles have to be able to monitor their own pollutants production. Since numerical models are too computationally expensive and approximated, new solutions based on Machine Learning are replacing standard techniques. In this project we considered a real V12 Internal Combustion Engine to propose a novel approach pushing Random Forests to generate meaningful prediction also in extreme cases (extrapolation, very high frequency peaks, noisy instrumentation etc.). The present work proposes also a data preprocessing pipeline for strongly unbalanced datasets and a reinterpretation of the regression problem as a classification problem in a logarithmic quantized domain. Results have been evaluated for two different models representing a pure interpolation scenario (more standard) and an extrapolation scenario, to test the out of bounds robustness of the model. The employed metrics take into account different aspects which can affect the homologation procedure, so the final analysis will focus on combining all the specific performances together to obtain the overall conclusions.

Exergy and thermoeconomic analysis of a turbofan engine during a typical commercial flight

In an energy perspective of cost-reduction and configuration-optimization, it becomes necessary to develop and use advanced tools for the analysis, design and improvement of energy conversion systems. In the aeronautical industry, such trend is fundamental since this industry has evolved to design extremely complex aircrafts, with highly integrated systems, requiring more information in order to evaluate the whole system. The aim of this paper is to present an exergy-based analysis as to evaluate the global performance of a typical turbofan engine and its components. The study presents values for exergy efficiency over the whole flight cycle, critical equipment and flight phases considering exergy destruction and estimating internal and exhaust flow costs. (C) 2009 Elsevier Ltd. All rights reserved.

Messaging Application Engine for Symbian Platform

Tämä diplomityö kuvaa viestintä sovelluksen ytimen kehitystyön Symbian-alustalle. Koko sovelluksen vaatimuksena oli vastaamattomiin puheluihin vastaaminen ennalta määritellyillä tekstiviesteillä käyttäjän määrittelemien sääntöjen mukaisesti. Ei-toiminnallisia vaatimuksia olivat resurssien käytön vähentäminen ja uudelleenkäytön mahdollistaminen. Täten tämän työn tavoitteena oli kehittää ydin, joka kapseloi sovelluksen sellaisen toiminnallisuuden, joka on käyttöliittymästä riippumatonta ja uudelleenkäytettävää. Kehitystyössä ohjasi Unified Process, joka on iteroiva, käyttötapauksien ohjaama ja arkkitehtuurikeskeinen ohjelmistoprosessi. Se kannusti käyttämään myös muita teollisuudenalan vakiintuneita menetelmiä, kuten suunnittelumalleja ja visuaalista mallintamista käyttäen Unified Modelling Languagea. Suunnittelumalleja käytettiin kehitystyön aikana ja ohjelmisto mallinnettiin visuaalisesti suunnittelun edistämiseksi ja selkiyttämiseksi. Alustan palveluita käytettiin hyväksi kehitysajan ja resurssien käytön minimoimiseksi. Ytimen päätehtäviksi määrättiin viestien lähettäminen sekä sääntöjen talletus ja tarkistaminen. Sovelluksen eri alueet, eli sovelluspalvelin ja käyttöliittymää, pystyivät käyttämään ydintä ja sillä ei ollut riippuvuuksia käyttöliittymätasolle. Täten resurssien käyttö väheni ja uudelleenkäytettävyys lisääntyi. Viestien lähettäminen toteutettiin Symbian-alustan menetelmin. Sääntöjen tallettamiseen tehtiin tallennuskehys, joka eristää sääntöjen sisäisen ja ulkoisen muodon. Tässä tapauksessa ulkoiseksi tallennustavaksi valittiin relaatiotietokanta. Sääntöjen tarkastaminen toteutettiin tavanomaisella olioiden yhteistoiminnalla. Päätavoite saavutettiin. tämä ja muut hyviksi arvioidut lopputulokset, kuten uudelleenkäytettävyys ja vähentynyt resurssien käyttö, arveltiin juontuvan suunnittelumallien ja Unified Processin käytöstä. Kyseiset menetelmät osoittivat mukautuvansa pieniinkin projekteihin. Menetelmien todettiin myös tukevan ja kannustavan kehitystyön aikaista oppimista, mikä oli välttämätöntä tässä tapauksessa.

It’s a workflow engine. It’s working with linked data. It’s repository! – Supporting electronic thesis related processes in University of Helsinki library

Presentation at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014

On the energetics of stratified turbulent mixing, irreversible thermodynamics, Boussinesq models and the ocean heat engine controversy

In this paper, the available potential energy (APE) framework of Winters et al. (J. Fluid Mech., vol. 289, 1995, p. 115) is extended to the fully compressible Navier– Stokes equations, with the aims of clarifying (i) the nature of the energy conversions taking place in turbulent thermally stratified fluids; and (ii) the role of surface buoyancy fluxes in the Munk & Wunsch (Deep-Sea Res., vol. 45, 1998, p. 1977) constraint on the mechanical energy sources of stirring required to maintain diapycnal mixing in the oceans. The new framework reveals that the observed turbulent rate of increase in the background gravitational potential energy GPEr , commonly thought to occur at the expense of the diffusively dissipated APE, actually occurs at the expense of internal energy, as in the laminar case. The APE dissipated by molecular diffusion, on the other hand, is found to be converted into internal energy (IE), similar to the viscously dissipated kinetic energy KE. Turbulent stirring, therefore, does not introduce a new APE/GPEr mechanical-to-mechanical energy conversion, but simply enhances the existing IE/GPEr conversion rate, in addition to enhancing the viscous dissipation and the entropy production rates. This, in turn, implies that molecular diffusion contributes to the dissipation of the available mechanical energy ME =APE +KE, along with viscous dissipation. This result has important implications for the interpretation of the concepts of mixing efficiency γmixing and flux Richardson number Rf , for which new physically based definitions are proposed and contrasted with previous definitions. The new framework allows for a more rigorous and general re-derivation from the first principles of Munk & Wunsch (1998, hereafter MW98)’s constraint, also valid for a non-Boussinesq ocean: G(KE) ≈ 1 − ξ Rf ξ Rf Wr, forcing = 1 + (1 − ξ )γmixing ξ γmixing Wr, forcing , where G(KE) is the work rate done by the mechanical forcing, Wr, forcing is the rate of loss of GPEr due to high-latitude cooling and ξ is a nonlinearity parameter such that ξ =1 for a linear equation of state (as considered by MW98), but ξ <1 otherwise. The most important result is that G(APE), the work rate done by the surface buoyancy fluxes, must be numerically as large as Wr, forcing and, therefore, as important as the mechanical forcing in stirring and driving the oceans. As a consequence, the overall mixing efficiency of the oceans is likely to be larger than the value γmixing =0.2 presently used, thereby possibly eliminating the apparent shortfall in mechanical stirring energy that results from using γmixing =0.2 in the above formula.

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.

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%.

THERMAL CHARACTERIZATION OF COMBUSTION CHAMBER COMPONENTS IN A GASOLINE TURBOCHARGED DIRECT INJECTION (GTDI) ENGINE

This report is a PhD dissertation proposal to study the in-cylinder temperature and heat flux distributions within a gasoline turbocharged direct injection (GTDI) engine. Recent regulations requiring automotive manufacturers to increase the fuel efficiency of their vehicles has led to great technological achievements in internal combustion engines. These achievements have increased the power density of gasoline engines dramatically in the last two decades. Engine technologies such as variable valve timing (VVT), direct injection (DI), and turbocharging have significantly improved engine power-to-weight and power-to-displacement ratios. A popular trend for increasing vehicle fuel economy in recent years has been to downsize the engine and add VVT, DI, and turbocharging technologies so that a lighter more efficient engine can replace a larger, heavier one. With the added power density, thermal management of the engine becomes a more important issue. Engine components are being pushed to their temperature limits. Therefore it has become increasingly important to have a greater understanding of the parameters that affect in-cylinder temperatures and heat transfer. The proposed research will analyze the effects of engine speed, load, relative air-fuel ratio (AFR), and exhaust gas recirculation (EGR) on both in-cylinder and global temperature and heat transfer distributions. Additionally, the effect of knocking combustion and fuel spray impingement will be investigated. The proposed research will be conducted on a 3.5 L six cylinder GTDI engine. The research engine will be instrumented with a large number of sensors to measure in-cylinder temperatures and pressures, as well as, the temperature, pressure, and flow rates of energy streams into and out of the engine. One of the goals of this research is to create a model that will predict the energy distribution to the crankshaft, exhaust, and cooling system based on normalized values for engine speed, load, AFR, and EGR. The results could be used to aid in the engine design phase for turbocharger and cooling system sizing. Additionally, the data collected can be used for validation of engine simulation models, since in-cylinder temperature and heat flux data is not readily available in the literature..

THERMAL CHARACTERIZATION OF A GASOLINE TURBOCHARGED DIRECT INJECTION (GTDI) ENGINE UTILIZING LEAN OPERATION AND EXHAUST GAS RECIRCULATION (EGR)

The push for improved fuel economy and reduced emissions has led to great achievements in engine performance and control. These achievements have increased the efficiency and power density of gasoline engines dramatically in the last two decades. With the added power density, thermal management of the engine has become increasingly important. Therefore it is critical to have accurate temperature and heat transfer models as well as data to validate them. With the recent adoption of the 2025 Corporate Average Fuel Economy(CAFE) standard, there has been a push to improve the thermal efficiency of internal combustion engines even further. Lean and dilute combustion regimes along with waste heat recovery systems are being explored as options for improving efficiency. In order to understand how these technologies will impact engine performance and each other, this research sought to analyze the engine from both a 1st law energy balance perspective, as well as from a 2nd law exergy analysis. This research also provided insights into the effects of various parameters on in-cylinder temperatures and heat transfer as well as provides data for validation of other models. It was found that the engine load was the dominant factor for the energy distribution, with higher loads resulting in lower coolant heat transfer and higher brake work and exhaust energy. From an exergy perspective, the exhaust system provided the best waste heat recovery potential due to its significantly higher temperatures compared to the cooling circuit. EGR and lean combustion both resulted in lower combustion chamber and exhaust temperatures; however, in most cases the increased flow rates resulted in a net increase in the energy in the exhaust. The exhaust exergy, on the other hand, was either increased or decreased depending on the location in the exhaust system and the other operating conditions. The effects of dilution from lean operation and EGR were compared using a dilution ratio, and the results showed that lean operation resulted in a larger increase in efficiency than the same amount of dilution with EGR. Finally, a method for identifying fuel spray impingement from piston surface temperature measurements was found. Note: The material contained in this section is planned for submission as part of a journal article and/or conference paper in the future.

IMPROVING STARTABILITY AND REDUCING EMISSIONS IN FLEXFUEL SPARK IGNITION DIRECT INJECTION VARIABLE CAM TIMING ENGINE

Experimental work and analysis was done to investigate engine startup robustness and emissions of a flex-fuel spark ignition (SI) direct injection (DI) engine. The vaporization and other characteristics of ethanol fuel blends present a challenge at engine startup. Strategies to reduce the enrichment requirements for the first engine startup cycle and emissions for the second and third fired cycle at 25°C ± 1°C engine and intake air temperature were investigated. Research work was conducted on a single cylinder SIDI engine with gasoline and E85 fuels, to study the effect on first fired cycle of engine startup. Piston configurations that included a compression ratio change (11 vs 15.5) and piston geometry change (flattop vs bowl) were tested, along with changes in intake cam timing (95,110,125) and fuel pressure (0.4 MPa vs 3 MPa). The goal was to replicate the engine speed, manifold pressure, fuel pressure and testing temperature from an engine startup trace for investigating the first fired cycle for the engine. Results showed bowl piston was able to enable lower equivalence ratio engine starts with gasoline fuel, while also showing lower IMEP at the same equivalence ratio compared to flat top piston. With E85, bowl piston showed reduced IMEP as compression ratio increased at the same equivalence ratio. A preference for constant intake valve timing across fuels seemed to indicate that flattop piston might be a good flex-fuel piston. Significant improvements were seen with higher CR bowl piston with high fuel pressure starts, but showed no improvement with low fuel pressures. Simulation work was conducted to analyze initial three cycles of engine startup in GT-POWER for the same set of hardware used in the experimentations. A steady state validated model was modified for startup conditions. The results of which allowed an understanding of the relative residual levels and IMEP at the test points in the cam phasing space. This allowed selecting additional test points that enable use of higher residual levels, eliminating those with smaller trapped mass incapable of producing required IMEP for proper engine turnover. The second phase of experimental testing results for 2nd and 3rd startup cycle revealed both E10 and E85 prefer the same SOI of 240°bTDC at second and third startup cycle for the flat top piston and high injection pressures. E85 fuel optimal cam timing for startup showed that it tolerates more residuals compared to E10 fuel. Higher internal residuals drives down the Ø requirement for both fuels up to their combustion stability limit, this is thought to be direct benefit to vaporization due to increased cycle start temperature. Benefits are shown for an advance IMOP and retarded EMOP strategy at engine startup. Overall the amount of residuals preferred by an engine for E10 fuel at startup is thought to be constant across engine speed, thus could enable easier selection of optimized cam positions across the startup speeds.

Acoustical and emission characteristics of small, high-speed internal combustion engines. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Automotive manufacturing assessment system. Volume IV: Engine manufacturing analysis. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Automotive manufacturing assessment system. Volume II: product schedules of engine/drivetrain combinations. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

A compilation of steady state automotive engine test data. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.