Orientador: Rogério Gonçalves dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T21:02:17Z (GMT). No. of bitstreams: 1 Cavaglieri_MarceloRenato_M.pdf: 17998120 bytes, checksum: 987df39d379a639bae4123aeab57a9d6 (MD5) Previous issue date: 2014 / Resumo: Com o intuito de otimizar o Motor de Combustão Interna e encontrar aplicações que o utilizem de forma racional e eficiente, nessa dissertação estuda-se o comportamento dinâmico da pressão na cavidade dos Coletores de admissão, já que o escoamento através dele acontece de forma pulsada, devido ao movimento do pistão e modulado pelo abrir e fechar das válvulas de admissão e escapamento. Sendo o Coletor de Admissão parte desse circuito, ele consequentemente impõe uma impedância a esse escoamento intermitente, podendo ser mais ou menos acentuada, devido suas formas construtivas. Para essa avaliação busca-se um fator ou um coeficiente que quantifique como as ondas de pressão interagem com a cavidade do Coletor de Admissão, de forma metódica e confiável, para que os resultados possam ser usados como ferramenta prática de desenvolvimento desse componente. Podendo assim, os Coletores de Admissão serem ajustados adequadamente à aplicação e não apenas nos quesitos de regimes permanentes tradicionais como perda de carga e desbalanceamento no fornecimento de ar. Nessa dissertação é apresentado um aparato para medir experimentalmente a curva do Coeficiente de Transmissão de onda de pressão, seus detalhes construtivos, de configuração e operação para a obtenção de curvas de boa qualidade. É mostrado também um método para validação do aparato e por fim a comparação do Coeficiente de Transmissão com a curva de desempenho desses componentes quando instalados em um Motor de Combustão Interna. Comprovando dessa maneira, a relação entre as características dinâmicas da cavidade e sua influência no desempenho do Motor de Combustão Interna e mais, demonstrando que o método experimental de medir o Coeficiente de Transmissão é uma forma eficaz e coerente de se quantificar a influência desse componente no processo de admissão / Abstract: In order to optimize the Internal Combustion Engine and find out applications that use it rationally and efficiently, in this dissertation it is studied the dynamic behavior of the intake manifolds cavity pressure, since the flow through it happens in a pulsed manner, due to the movement of the piston and modulated by opening and closing the intake and exhaust valves. Being the intake manifold part of this circuit, it imposes impedance to the flow that may be more or less pronounced, due to its constructive design. For this evaluation it is made an experimental determination of the Transmission Coefficient of pressure waves through the Intake Manifold, methodically and reliably, so the results can be used as a practical tool for developing these components. The Intake Manifold may thus be properly adjusted to the application needs and not just in the categories of traditional patterns like permanent loss and imbalance of air supply. This dissertation presents an experimental apparatus to measure the curve of the wave pressure Transmission Coefficient, its construction details, configuration and operation to get good quality curves. It is also shown a method to calibrate the apparatus and finally, the comparison of the Transmission Coefficient with the performance curve of measured Intake Manifolds when installed on an Internal Combustion Engine. Providing this way, the correlation between the dynamic characteristics of the cavity and its influence on the Internal Combustion Engine¿s performance and demonstrating that the experimental method to measure the Transmission Coefficient is an effective and consistent way to quantify the influence of the Intake Manifold in admission process / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Orientadores: Pablo Siqueira Meirelles, Douglas Eduardo Zampieri / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T23:03:43Z (GMT). No. of bitstreams: 1 Mendes_AlexandreSchalch_D.pdf: 4157689 bytes, checksum: a667c356ec83b5bb7af3834db18db144 (MD5) Previous issue date: 2012 / Resumo: Este trabalho tem como objetivo a aplicação da técnica conhecida como Hardware-in-the-Loop (HIL), para a avaliação do comportamento dinâmico de dois sistemas mecânicos não-lineares e assim verificar o desempenho da técnica nestes casos. O primeiro estudo consiste na avaliação de um componente, no caso uma engrenagem bi-partida, sujeito a contatos dinâmicos e impactos os quais são difíceis de serem modelados matematicamente. O segundo caso estudado consiste na avaliação de um amortecedor de vibrações torcionais do tipo elastomérico utilizado em motores de combustão interna, o qual apresenta não-linearidades de material, cujas propriedades variam em função da temperatura da borracha. Bancadas de testes distintas foram elaboradas para a avaliação dos dois componentes, tendo como entrada sinais de torques ou deslocamentos angulares gerados em tempo real por um código desenvolvido em ambiente MATLAB/SIMULINK e compilados para a simulação dos componentes através de uma placa controladora dSPACE. Nos estudos de HIL da engrenagem bi-partida, compararam-se os sinais de deslocamento angular medidos em um motor Diesel e na bancada de testes. Como conclusão verificou-se que os sinais obtidos na bancada foram muito próximos aos observados no motor. Já no caso do amortecedor, foram medidas as amplitudes das vibrações no cubo e anel do damper. Os deslocamentos angulares do cubo e anel foram comparados às amplitudes reais medidas em um motor no dinamômetro e, ao término do trabalho, verificou-se que as amplitudes obtidas do ensaio de HIL apresentaram boa correlação com os valores medidos no motor, alcançando-se dessa forma os objetivos propostos para esse trabalho / Abstract: The objective of this work is to apply the technique known as Hardware-in-the-Loop (HIL), to assess the dynamic behavior of two non-linear mechanical systems and to verify the performance of the technique in these cases. The first study is the evaluation of a component, in this case a pre-tensioned gear, subjected to dynamic contacts and impacts which are difficult to be modeled mathematically. The second study is to evaluate an elastomeric torsional vibration damper (TVD) used in internal combustion engines, which has non-linear material properties that depend on the rubber temperature. Different test benches were developed for the evaluation of these two components, with the input signals of torques or angular displacements in real time, generated by a code developed in MATLAB / SIMULINK and compiled for the simulation of the components via dSPACE controller board. In the study of the pre-tensioned gear, we compared the signals of angular displacements in a Diesel engine with the test bench values. In conclusion it was found that the signals from the tests were very similar to those observed in the engine. In the case of the damper, were measured the amplitude of vibration at the hub and ring of the TVD. The angular displacements of the hub and ring were compared to actual measurements on an engine in the dynamometer. At the end of this work, it was found that the obtained amplitudes from the HIL test showed good correlation with the values measured in the engine, achieving that way the proposed goals of this work / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

Orientador: Robson Pederiva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T21:11:27Z (GMT). No. of bitstreams: 1 Chagas_ClodoaldoBorges_M.pdf: 26402874 bytes, checksum: d4bfb8b718bb540f2313823b84724082 (MD5) Previous issue date: 2015 / Resumo: Os sistemas de transmissão por correntes são umas das principais formas de se transmitir torque e potência entre eixos paralelos. A confiabilidade dos sistemas de transmissão por corrente na sincronização do eixo de manivelas e do eixo de comando de válvulas nas aplicações automotivas tem permitido seu emprego durante toda a vida útil do motor. A aparente vantagem no uso dos sistemas de corrente esconde algumas características indesejáveis inerentes a esse tipo de transmissão. Alguns fenômenos físicos como a "Ação Poligonal" a qual faz com que ocorra flutuação da razão entre as velocidades angulares do eixo movido e motriz, mesmo quando o eixo motriz está em velocidade angular constante, puderam ser modelados por meio da analise cinemática e validados experimentalmente em situações "quasi-estáticas". As guias de corrente são inicialmente elementos cuja principal função é atenuar as vibrações transversais da corrente. No entanto, o estudo desenvolvido constatou a guia como sendo um importante mecanismo cuja posição e geometria podem minimizar a flutuação da razão entre as velocidades angulares. Outro importante aspecto aponta a necessidade da existência de elementos com a capacidade de permitir um auto ajuste de posicionamento durante o ciclo de engate de um elo de corrente. Compreender o carregamento aplicado pela corrente sobre a guia tensora torna possível predizer o estado de tensão deste componente bem como o coeficiente de atrito entre corrente e guia. A interação dos resultados teóricos e experimentais puderam ser introduzidos em um software comercial de elementos finitos para determinação do estado de tensão da guia. Os resultados da extensometria aplicada na guia de corrente foi confrontada aos resultados deste software a fim de obter a validação dos modelos desenvolvidos no presente trabalho. O estudo dos modelos matemáticos em paralelo aos experimentos guiam o desenvolvimento do presente trabalho / Abstract: The chain transmission systems are among the most important ways to transfer power and torque between parallel axes. The reliability of the chain transmission systems for synchronizing the crank shaft and command shaft in the automotive engines allows that this type of transmission system can be employed during the whole life of the passenger car engine. This apparent advantage in the use of the chains hides some undesirable characteristics which are inherent to this kind of discrete system. Some physical phenomena such as cinematic analysis of the "Polygonal Action" which makes the ration between angular velocity of driven and driving axis fluctuate during a chain link engagement, even when the velocity of the driving shaft is at constant angular velocity. This fluctuation was modeled and experimental tests were carried out to validate the model for "quasi-static" situations. The chain guide and chain blades are initially elements which the main function is to hold the transversal vibration of the chain. The present study identified the chain guide profile and assembly position as an important helping component to minimize the fluctuation of angular velocity ratio between sprockets. Another important feature of the transmission system picks up the necessity of at least one of the system components has to be able to self-adjust during the engagement cycle. The comprehension of the contact forces which loads the chain blade by the chain becomes possible understanding the stress state of this component and determine the friction coefficient between chain and blade. The interaction of theoretical and experimental results were introduced as incomes at commercial finite element software to determine the stress state of this component. The measurements of the extensometers were compared to the commercial software to validate the mathematical models and simplification adopted in the present work. The mathematical model in parallel to the experimental procedures drive the development of the present work / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Hlavní cíl této práce je vyvinout pokročilý výpočtový model dynamiky pístové skupiny. Kontakt mezi pístem a válcem je zprostředkován skrz vrstvu maziva nebo pomocí kontaktu nerovností. To vede k různým režimům mazání, tudíž k různým silovým interakcím působících na plochy kontaktní dvojice. Během řešení hydrodynamiky a kontaktu nerovností, je nutné zahrnout deformaci pístu a válce do výpočtu—přirozeně iterační proces. Jelikož požadavky na výpočtovou síť kontaktních sil a deformaci těles se liší, byl navržen robustní mapovací algoritmus. Výsledky vyvinutého výpočtového nástroje jsou experimentálně verifikovány. Pro tento účel je uskutečněno měření sekundárního pohybu pístu pomocí laserových snímačů vzdálenosti. Měření je vykonáno na experimentálním motoru s bočním vedením ventilů a průhlednou hlavou válce, aby byl přítomen kompresní tlak ve spalovací komoře. Naměřený boční pohyb pístů je znehodnocen. Proto je další analýze potrobeno pouze úhlové natočení pístů. Shoda mezi naměřenými a vypočítanými výsledky variuje pro různé části pracovního cyklu. Dobrá shoda je dosažena během komprese a expanze. Naopak výrazné rozdíly nastávají, když boční síla dosahuje nízkých hodnot: sání a výfuk. Hlavní přínos této práce je vytvoření výpočtového nástroje, který je schopný zahrnout výše popisované jevy, které mají podstatný vliv na dynamiku pístové skupiny. Bohužel to vede k dlouhým výpočtovým časům, zvláště když je zahrnuta deformace. Tento problém řeší navržený paralelní výpočet. To je založeno na paralelizaci podprogramu během vyčíslování citlivostní analýzy. Tímto způsobem je řádově redukován výpočtový čas.

Internal combustion engines are the most commonly used engines in the automotive world. However, these engines lack an overheating prevention system against cooling system failures when they exceed their normal operating temperature. Less experienced drivers (users) usually do not notice overheating until the engine stops, generating economic expenses in engine repairs. As such, this paper describes the design and construction of an electromechanical device to prevent engine overheating. This device is installed in a vehicle and operates independently from the electronic control unit (ECU); it records the coolant temperature and controls air admission to the engine of the vehicle in which it is installed. In addition, a new Arduino-based card will receive signals from a temperature sensor as input and process them according to its programming. Then, it will send signal outputs to the actuators: A servomotor, monitor, LED display, and buzzer. To control the intake flow, a butterfly valve is used with the servomotor. This valve partially or totally restricts the engine airflow, based on the temperature programmed for the Arduino, thus protecting the engine from overheating.

Extensive analysis of the physical and chemical effects controlling the operation of combustion modes driven by auto-ignition is presented in this thesis. Specifically, the study integrates knowledge attained by analyzing the effects of fuel molecular structure on auto-ignition, quantity or quality of charge dilution, and in-cylinder temperature and pressure on burning characteristics in single and multiple injection strategies employed in compression ignition (CI), partially premixed combustion (PPC) and homogenous charge compression ignition (HCCI) engines. In the first section of the thesis, a multiple injection strategy aimed to produce heat at a constant pressure, commonly known as isobaric combustion, has been studied. Then, to eliminate the complexity of spray-to-spray interactions observed with isobaric combustion, the second section of the thesis is focused on compression ignition (CI) through single injection. In the final section, the presentation will move towards moderate conditions with high dilution, in which combustion becomes dominated by chemical kinetics. At these conditions, there is emerging evidence that certain fuels exhibit unusual heat release characteristics where fuel releases heat in three distinctive stages. Overall, the thesis discusses factors controlling the auto-ignition for CI, PPC and HCCI engines that can provide valuable insights to improve their operation. Isobaric combustion in CI engine involves large interactions between physical and chemical effects. Injection of spray jets into oxygen-deprived regions catalyzes the mechanism for soot production – urging to employ either multiple injectors, low reactivity fuel or an additional expansion stage. Fuels – regardless of their auto-ignition tendency – share the same combustion characteristics in the high load CI, where auto-ignition is controlled by only the injector’s physical specifications. Such observation is a showcase of the fuel flexible engines that has the potential of using sustainable fuels – without being restrained by the auto-ignition properties of the fuel. The thesis provides evidence from experiment and simulation that three-stage auto-ignition is indeed a phenomenon driven by chemical kinetics. Three-stage auto-ignition opens the perspective to overcome the limitation of the high-pressure rise rates associated with HCCI engine.

Internal combustion engines (ICEs) are essential for the welfare of today’s human civilization yet they contribute to almost 10% of the global CO2 emissions. Reducing the carbon footprint of the ICEs can be achieved by either increasing the engine efficiency to reduce fuel consumption or the utilization of carbon-neutral fuels. This dissertation aims to investigate the effect of the oxidizer composition on the efficiency and performance of the homogenous charge compression ignition (HCCI) engine. It also aims to study the behavior of hydrogen in HCCI engines. The experiments are conducted using a Cooperative Fuel Research (CFR) engine. The study also involves using chemical kinetics simulations to estimate the ignition delay time of hydrogen which is relevant to the HCCI mode of combustion. The results suggest that the specific heat ratio of the oxidizer does not significantly affect the HCCI engine efficiency. On the fuel side, hydrogen showed high sensitivity to engine running conditions due to the lack of negative temperature coefficient (NTC).

<p>  </p> <p>A Cummins 6.7L natural gas engine enabled with VVA was installed in a research test cell at Purdue’s Ray Herrick Laboratories for experimental testing. The stock engine which was connected to an AC dynameter was mounted on a movable test bed outfitted with numerous sensors, a charge air cooler, and an external heat exchanger. In the engine control room, a few different systems were set up to run the dyno, collect data from the engine sensors, and monitor the safety apparatuses in the test cell. </p> <p>After the test cell setup was completed, an initial baseline testing was performed to compare the stock engine operation with the baseline engine data given in the Cummins fuel map. The testing was used to verify the engines stock functionality and troubleshoot some additional issues before setting the boundary conditions. Once the boundary conditions were set, a final stock engine testing was performed at rated to check for repeatability and verify stock engine operation following the engine modifications made to accommodate the VVA. </p> <p>Following the baseline testing, the VVA system was assembled on the standalone rig to verify its operation before mounting it on the engine. In order to run the natural gas valve profiles received from Cummins, the VVA controller gains were retuned and the LVDT sensors were calibrated so that the desired closing, opening and lift behaviors were achieved. After verifying the VVA’s functionality, the hardware was mounted on the engine for the VVA experimental testing. </p> <p>The initial VVA testing was focused on understanding the impacts of intake valve modulation on the gas exchange process. Based on previous simulation work, reductions in pumping work leading to better fuel economy is one expected outcome. Experimental testing data related to the engine performance and operation was used to compare each IVC case to the stock IVC timing. These results were also compared to the previous GT-Power work to identify any apparent trends.</p> <p>Future work includes using VVA to further improve efficiency in the part load region, and reduce knock at higher loads. Additionally, the incorporation of a laser based in-cylinder sensing system will help to optimize the capability of VVA.</p>

The road transport sector, dominated by internal combustion engines, accounts for as high as 23% of annual carbon emissions and is considered the major area where urgent carbon reduction strategies are required. Natural gas is considered one of the intermediate fuels to reduce carbon emissions before net carbon neutral solutions can be achieved. Methane (CH4), a major constituent of natural gas, has the highest hydrogen-to-carbon ratio among the naturally occurring hydrocarbons, and the CO2 emission from natural gas combustion is around 25% less than diesel combustion. Lean combustion shows promises for improved engine efficiency, thereby reducing carbon emissions for a given required power output. However, igniting lean natural gas mixtures requires high ignition energy, beyond the capability of spark ig nition. The pre-chamber combustion (PCC) concept can provide the required ignition energy with relatively simple components. While most pre-chamber designs found in the literature are bulky and require extensive cylinder head modifications or complete engine redesign, the narrow-throat pre-chamber design can readily fit the diesel injector pockets of most heavy-duty engines without the need for substantial hardware modifications. The unique pre-chamber design is significantly different from the contemporary pre-chamber geometries, and its engine combustion phenomena and operating characteristics are largely unknown. This thesis work investigates the effect of important pre-chamber dimensions, such as the volume, nozzle hole diameter, and throat diameter, on the engine operating characteristics and emission trends. The experiments focus on the lean operation with excess air ratios (λ) exceeding 1.6, which can be achieved by auxiliary fuel injection into the pre-chamber. The air-fuel mixture formation process inside the pre-chamber is also investigated by employing 1-D and 3-D CFD simulations, where the engine experiments provided the boundary conditions. From the simulation results, a correlation between the injected and the trapped fuel in the pre-chamber is proposed by theoretical scavenging models to estimate the air-fuel ratio in the pre-chamber with high accuracy. Although the studies largely rely on thermodynamic engine experiments, the 1-D engine simulation implements the engine studies in estimating the mixture composition and heat transfer losses from the engine.

The corrosion resistance of chemically modified β-eucryptite (Li_0.41Mg_0.035AlP_0.52Si_0.480₄) having low expansion anisotropy and a near zero coefficient of thennal expansion was evaluated. Samples were exposed to aqueous hydrochloride acid at temperatures up to 100°C and environments containing sodium sulfate up to l000°C. The corrosion resistance was characterized by dilatometry, scanning electron microscopy, X-ray diffraction, energy dispersive x-ray analysis, weight variations, and mechanical properties variations. The results show that modified β-eucryptite is more severely corroded than commercial lithium-alumina-silicate glass-ceramics when exposed to these environments. Aqueous HCI removes AIP04 from modified β-eucryptite leaving a very porous structure. Molten salt corrodes modified β-eucryptite by penetration of sodium and sulfur which form an alkali melt under the surface. The modulus of rupture and the Young's modulus are reduced by both types of corrosion. / Master of Science