University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

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D. Tech. Mechanical Engineering. / Discusses how to reduce the negative impacts of petroleum oil based fuels in reciprocating engines on the environment through the use of oxygenated (alcohol) blends, while not deteriorating engine performance. The specific objectives are as follows: To evaluate the performance characteristics of n-butanol-diesel blends: B5, B10 and B20, in a direct-injection turbo-charged diesel engine and to compare findings with a study that was carried out by others (Sayin, 2010). To compare the performance, combustion and emission characteristics of dual alcohol-gasoline with single alcohol-gasoline blends fired in a naturally-aspirated (NA) spark ignition (SI) engine. To compare the combustion and emission characteristics of dual alcohol (methanol-n-butanol-gasoline) blends with single alcohol (methanol-gasoline) blends in a single-cylinder SI engine. To evaluate the combustion and regulated emission characteristics of DF and n-butanol/diesel blends (B5, B10, and B20 where B5 represents 5 % shared volume of n-butanol to 95 % diesel fuel) fired in a high load turbo-charged diesel engine and to compare the findings with a study that was conducted by Raslavicius & Bazaras, (2010).

O etanol (álcool etílico) tem sido cada vez mais estudado e testado como combustível alternativo para substituição do uso de alguns derivados de petróleo em motores de combustão interna. O presente trabalho procura abordar o emprego do etanol na forma vaporizada em motores do ciclo Otto, objetivando a obtenção de melhores níveis de rendimento térmico total. Deste modo, um motor para teste de octanagem (motor CFR) foi equipado com um vaporizador de álcool instalado no coletor de escapamento, e após uma série de ensaios, várias análises puderam ser feitas. Essas considerações procuraram se ater a aspectos como rendimento térmico, relação ar/combustível, ângulo de avanço da centelha, temperatura de escape, assim como potência e eficiência volumétrica, levando em conta, sempre, a sua influência no funcionamento geral do motor. Ficou constatado que o motor movido a etanol vaporizado apresenta rendimento consideravelmente maior, menor consumo de combustível e funcionamento mais suave que aqueles verificados quando o mesmo motor e alimentado com álcool líquido. / The ethanol (ethyl alcohol) has been studied more and more as alternative fuel to replace some petroleum derivatives for internal combustion engines. The attached study examines the application of vaporized ethanol for Otto cycle engines, searching for better levels of total thermal efficiency. Therefore, an engine for test of octane number (CFR motor) was equipped with an alcohol vaporizer installed inside the escape pipe, and after many experiences, several analysis were made. The various analysis included aspects as thermal efficiency, air/fuel ratio, advance ignition, escape temperature, power and volumetric efficiency, always considering their influence on the operation of the engine. It was confirmed that the engine moved by vaporized ethanol presents higher thermal efficiency, smaller fuel consumption and smoother working than in case of alimentation by liquid alcohol.

O álcool etílico ou etanol vem se tornando, neste novo século, uma importante referência para estudos e aplicações que procuram um combustível alternativo ao uso de derivados de petróleo em motores de combustão interna. Neste trabalho, o uso do etanol vaporizado pelos gases de escape em motores do ciclo Otto busca a obtenção de melhores níveis de rendimento térmico e emissões de poluentes. Assim sendo, um motor de 1.0 litro foi montado em laboratório com um trocador de calor instalado ao lado do coletor de escapamento, e uma série de testes foram feitos, possibilitando uma cuidadosa análise quanto a rendimento térmico, relação ar/álcool, ângulo de avanço da centelha, temperatura de escape e gases de emissão, entre outros aspectos. Conclui-se que o motor a álcool vaporizado, em certos regimes de funcionamento, apresenta rendimento maior e emissões menores que aqueles verificados no motor a álcool líquido. / The ethyl alcohol or ethanol is becoming, in this new century, an important reference for studies and applications that search for an alternative fuel to be used in internal combustion engines, replacing oil derivatives. In this study, an Otto cycle engine is fueled with ethanol vaporized by the exhaust gases, aiming for better levels of thermal efficiency and exhaust emissions. Therefore, a 1.0 liter engine with a heat exchanger connected to the exhaust manifold was prepared in a test bench, and several tests were made, which allowed a criterious analysis about air/alcohol ratio, spark ignition time, exhaust temperature and exhaust emissions, and others. It was concluded that the engine fueled with vaporized alcohol presents, in some operation points, higher thermal efficiency and less emissions compared to the case of engine fueled with liquid alcohol.

Orientador: Rogério Gonçalves dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T13:19:35Z (GMT). No. of bitstreams: 1 Fajgenbaum_Renata_M.pdf: 5459929 bytes, checksum: 05a7fae663d15ca13af6858bbe983761 (MD5) Previous issue date: 2013 / Resumo: A motivação em se estudar os fenômenos que acontecem em cada subsistema de um motor de combustão interna ciclo Otto reside na possibilidade de se prever e otimizar seu funcionamento, em especial com os diferentes combustíveis de nova geração que estão sendo inseridos no mercado. O processo de atomização que ocorre nos bicos injetores de combustível, dispositivos integrantes do sistema de injeção eletrônica do motor, apresenta forte relação com a posterior reação de combustão e, por conseguinte, com a eficiência térmica do motor. No presente trabalho, experimentos foram conduzidos para investigar o efeito da temperatura do líquido em parâmetros de atomização de um atomizador do tipo mecânico-centrífugo utilizado em bicos injetores de combustível automotivos. O aparato experimental consistiu de uma bancada de injeção de combustível conectada a um sistema de controle de calor, este com objetivo de variar a temperatura do combustível. Os parâmetros de atomização foram avaliados por meio da técnica de Shadowgraphy, a fim de se medir diâmetro de gotas, distribuição de partículas e campo de velocidades. Gasolina e etanol em diferentes temperaturas foram usados para fornecer variação nas propriedades do líquido, ambos com a mesma pressão de injeção. Os resultados de tamanho de gota foram dados, principalmente, em termos de Sauter Mean Diameter (SMD) e outros diâmetros representativos que se mostraram pertinentes. Todas as medições foram realizadas em duas diferentes distâncias axiais do orifício de descarga. Para as duas distâncias escolhidas, 25 mm e 100 mm, o SMD e a velocidade se mostraram insensíveis à faixa de temperatura testada, devido à baixa variação das propriedades dos combustíveis. Por outro lado, a distribuição das partículas permitiu visualizar o efeito da temperatura nos diâmetros das gotas, mostrando que o aumento da temperatura proporciona diminuição no tamanho das gotas, e o comparativo entre os parâmetros nas duas distâncias axiais permitiu visualizar o efeito da primeira e segunda atomização sobre o spray / Abstract: The motivation in studying the phenomena that happen in each internal combustion engine subsystem lies in the possibility to predict and optimize its operation. The atomization process that occurs in fuel injectors, devices that belong to engine injection system, has a strong relation with the subsequent combustion reaction and thus with the engine thermal efficiency. Experiments were performed to investigate the liquid temperature effect on atomization parameters in an internal combustion engine pressure-swirl atomizer. The experimental apparatus consisted of a flow control rig connected with a heat control system. The flow rig, which is an injection system, was built specifically for that purpose and the heat system goal was to vary the liquid temperature. The atomization parameters were evaluated by means of Shadowgraphy technique in order to measure drop mean diameter, particle size distribution and drop velocity field. Gasoline and ethanol in different temperatures were used to provide variation in liquid properties and the same injection pressure was used for both fuels. The results for drop sizing were expressed in terms of Sauter Mean Diameter (SMD) and the velocity field as well as the particle size distribution measurements were taken in two different axial distances from the nozzle exit. At both distances, 25 mm and 100 mm, SMD and velocity seemed to be insensitive to the range of temperature used because it provided low variation in fuel properties. On the other hand, particle size distribution allowed the visualization of temperature effect on drop diameters, showing that increasing temperatures decrease droplet sizes, and the comparison between two axial distances allowed seeing the effects of first and second atomization on the spray / Mestrado / Termica e Fluidos / Mestra em Engenharia Mecânica

<div>The commercial vehicle sector is an important enabler of the economy and is heavily dependent on fossil fuels. In the fight against climate change, reduction of emissions by improving fuel economy is a key step for the commercial vehicle sector. Improving fuel economy deals with reducing energy losses from fuel to the wheels. This study aims to analyze efficiency improvements for two systems that are important in reducing CO2 emissions - hybrid powertrains and natural gas engines. At first, a prototype series hybrid powertrain was analyzed based on on-highway data collected from its powertrain components. Work done per mile by the electrical components of the powertrain showed inefficient battery operation. The net energy delivery of the battery was close to zero at the end of the runs. This indicated battery was majorly used as an energy storage device. Roughly 15% of losses were observed in the power electronics to supply power from battery and generator to the motor. Ability of the hybrid system to capture regenerative energy and utilize it to propel the vehicle is a primary cause for fuel savings. The ability of this system to capture the regenerative energy was studied by modeling the system. The vehicle model demonstrated that the system was capturing most of the theoretically available regenerative energy. The thesis also demonstrates the possibility of reduction of vehicular level losses for the prototype truck. Drag and rolling resistance coefficients were estimated based on two coast down tests conducted. The ratio of captured regenerative to the drive energy energy for estimated drag and rolling resistant coefficients showed that the current system utilizes 4%-9% of its drive energy from the captured regenerative energy. Whereas a low mileage Peterbilt 579 truck could increase the energy capture ratio to 8%-18% for the same drive profile and route. Decrease in the truck’s aerodynamic drag and rolling resistance can potentially improve the fuel benefits.</div><div>The second study aimed to reduce the engine level pumping losses for a natural gas spark ignition engine by cylinder deactivation (CDA). Spark ignited stoichiometric engines with an intake throttle valve encounter pumping/throttling losses at low speed, low loads due to the restriction of intake air by the throttle body. A simulation study for CDA on a six cylinder natural gas engine model was performed in GT- Power. The simulations were ran for steady state operating points with a torque range 25-560 ftlbs and 1600 rpm. Two , three and four cylinders were deactivated in the simulation study. CDA showed significant fuel benefits with increase in brake thermal efficiency and reduction in brake specific fuel consumption depending on the number of deactivated cylinders. The fuel benefits tend to decrease with increase in torque. Engine cycle efficiencies were analyzed to investigate the efficiency improvements. The open cycle efficiency is the main contributor to the overall increase in the brake thermal efficiency. The work done by the engine to overcome the gas exchange during the intake and exhaust stroke is referred to the pumping losses. The reduction in pumping losses cause an improvement in the open cycle efficiency. By deactivating cylinders, the engine meets its low torque requirements by increase in the intake manifold pressure. Increased intake manifold pressure also resulted in reduction of the pumping loop indicating reduced pumping losses. A major limitation of the CDA strategy was ability to meet EGR fraction requirements. The increase in intake manifold pressure also caused a reduction in the delta pressure across the EGR valve. At higher torques with high EGR requirements CDA strategy was unable to meet the required EGR fraction targets. This limited the benefits of CDA to a specific torque range based on the number of deactivated cylinders. Some variable valve actuation strategies were suggested to overcome this challenge and extend the benefits of CDA for a greater torque range.</div><div><br></div>

[pt] O desempenho de veículos automotivos é um importante atributo a ser avaliado quando motores de combustão interna e novos combustíveis estão sendo desenvolvidos. A previsão desse parâmetro também é de suma importância, uma vez que os testes de desempenho de automóveis em pista requerem prazos de realização e altos custos com equipamentos, aluguel da pista, contratação de pessoas e deslocamento de veículos e combustíveis. Além disso, seus resultados são diretamente afetados por irregularidades na superfície da pista e variações nas condições climáticas, como pressão ambiente, temperatura, umidade do ar e velocidade do vento. Assim, este trabalho tem como objetivo utilizar os dados coletados em testes de bancada com um motor de combustão interna com a finalidade de modelar os testes de retomada de velocidade de um automóvel convencional leve. A metodologia proposta simula a força de tração nas rodas a partir do torque medido no dinamômetro do motor ou a partir das curvas de pressão no interior da câmara de combustão com o auxílio de modelos de atrito para motores de ignição por centelha. Para validar o modelo proposto, foi necessário realizar testes de retomada de velocidade com o carro em um dinamômetro de chassi. Além disso, foram utilizadas sete misturas diferentes de etanol e gasolina, e concluiu-se que o etanol anidro puro promoveu maior capacidade de aceleração na maioria dos experimentos, mas apresentou maior consumo de combustível. Os combustíveis hidratados reduziram o desempenho, mas melhoraram a eficiência global. As simulações demonstraram alta precisão em relação ao experimento, com média da diferença do tempo de recuperação da velocidade de 0,51 segundos e desvio padrão de 0,078. Além disso, as simulações de desempenho de aceleração tiveram erros menores que 5,25 por cento. Além disso, a realização desses testes em laboratório tem a vantagem de um maior controle das condições ambientais da sala e dos parâmetros de operação do motor. / [en] Vehicle performance is an important feature to be evaluated when internal combustion engines and new fuels are being developed. Predicting this parameter is also of great significance, once track testing requires long periods of time to be done and high costs with equipment, rental of the track, hiring people and displacement of vehicles and fuels. In addition, their results are directly affected by track surface irregularities and variations in weather conditions such as ambient pressure, temperature, air humidity and wind speed. Thus, this work aims to use collected data in bench tests with an internal combustion engine in order to modeling an automobile speed recovery time. The proposed methodology simulates the traction force on the wheels based on the measured torque in engine dynamometer or from the pressure curves inside the combustion chamber with the aid of friction models for spark ignition engines. In order to validate the proposed model, it became necessary to perform speed recovery tests with the car on a chassis dynamometer. Also, seven different mixtures of ethanol and gasoline were used, and it was concluded that pure anhydrous ethanol promoted a higher acceleration capacity in most of the experiments but it had higher fuel consumption. Hydrated fuels reduced performance but improved global efficiency. The simulations demonstrated a high precision in relation to the experiment, with a speed recovery time diference average of 0.51 seconds and standard deviation of 0.078. Also, the acceleration performance simulations had errors smaller than 5.25 percent. In addition, doing these tests in laboratory has the advantage of a greater control of the room ambient conditions and the engine operating parameters.

En la presente tesis se desarrolla un sistema de control de la mezcla de aire y gasolina en un motor alternativo de cuatro tiempos, basado en redes neuronales. Para que el catalizador logre un grado de depuración aceptable con todos los gases contaminantes simultáneamente, debe mantenerse la proporción de aire y combustible, dentro de una banda muy estrecha. En estado estacionario, este objetivo se cumple sin demasiados problemas, pero el funcionamiento habitual de un vehículo es en régimen muy transitorio, donde los sistemas convencionales no logran evitar desviaciones importantes del punto de consigna. Estos se basan además en una gran cantidad de tablas estáticas, que deben calibrarse de forma experimental, lo cual es bastante costoso tanto en tiempo como en dinero.Para evitar estos problemas se ha diseñado un modelo matemático de un motor, que comprende todo el proceso de formación de la mezcla, sensores, la generación del par motor y la dinámica del vehículo. La realización final se ha realizado en el lenguaje de simulación MatLab/Simulink®. Los datos requeridos son fácilmente obtenibles bien por metrología, bien de forma experimental. Se ha validado con un motor SEAT de 1,6 l y 74 kW.Como primer paso se ha aplicado una estrategia de control convencional bastante simple, consistente en un controlador feedforward estático, más un controlador feedback de tipo PI ó PID. Esto ha permitido el estudio de las principales características del motor desde el punto de vista de control. Con los resultados obtenidos se ha diseñado un observador basado en una red neuronal, que elimine los retardos puros del sistema y que pueda ser utilizado para cerrar el lazo de control. Primero se ha usado una red feedforward, pero vistos los malos resultados, se ha desarrollado una red neuronal recurrente a partir de la red de Elman, que se ha modificado convenientemente para adaptarla a las dificultades propias del problema. El algoritmo de entrenamiento utilizado se basa en el de retropropagación clásico, y modifica no sólo los pesos entre capas, sino también los correspondientes a las neuronas de contexto, las cuales permiten memorizar estados internos. La principal mejora consiste en separar las neuronas de contexto en tantos grupos como entradas tiene la red, y entrenarlos por separado, de modo que cada grupo se adapte a la dinámica particular de la entrada a la que va asociado. Se muestra mediante simulación el comportamiento del conjunto motor más observador en lazo cerrado, y se compara con el esquema convencional. Se prueba asimismo la robustez del sistema frente a distintas consignas, ruido en la planta y defectos de sintonía. / In the present thesis a control system for the air-fuel mixture in a reciprocating four-stroke engine is developed, based on neural networks. The air-fuel ratio has to be kept within a very narrow window so that the catalyst achieves an acceptable degree of purification simultaneously with all the polluting gases. In steady state, this goal can be fulfilled without difficulties, but the usual operation of a vehicle is in a very transient state, where the conventional systems are not able to avoid important excursions from the set point. They also rely on a great number of look-up tables, which have to be tuned experimentally, thus with an enormous investment of money and time.To avoid those problems a mathematical model of an engine has been designed, in such a way that it comprises of the whole mixture formation process, sensors, the torque generation and the vehicle dynamics. Finally it has been implemented in the simulation language MatLab/Simulink®. The required data is easily available both from metrology, and experimental work. It has been validated with a 1,6 litre 74 kW SEAT engine.As a first step, a quite simple conventional control strategy has been applied, consisting of a static feedforward controller, and a PI or PID feedback controller. This has permitted studying the main features of the engine from the control point of view.With the obtained results an observer based on a neural network has been designed, which eliminates the delays of the system and that can be used to close the control loop. First a feedforward network has been used, but due to the bad results, a recurrent neural network has been developed starting from the Elman network, which has been properly modified in order to adapt it to the characteristic difficulties of the problem. The training algorithm used is based on that of classical backpropagation, and it modifies not only the weights interconnecting different layers, but also those corresponding to the context neurons, which allow the memorising of internal states. The main improvement consists in separating the context neurons in as many groups as the network has inputs, and to train them separately, so that each group adapts to the particular dynamics of the input with which it is associated. The behaviour of the engine plus the observer in closed loop is shown by means of simulation, and is compared with the conventional scheme. It is proven the robustness of system response to different set points, noise in the plant and tuning defects.

This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies. As a first step, a commercially available 1.2 kW genset engine is modified for biogas operation. The conventional premixing of air and biogas is compared with a new manifold injection strategy. The effect of biogas composition on engine performance is also studied. Results from the genset engine study indicate a very low overall efficiency of the system. This is mainly due to the very low compression ratio (4.5) of the engine. To gain further insight into factors that contribute to this low efficiency, thermodynamic engine simulations are conducted. Reasonable agreement with experiments is obtained after incorporating estimated combustion durations. Subsequently, the model is used as a tool to predict effect of different parameters such as compression ratio, spark timing and combustion durations on engine performance and efficiency. Simulations show that significant improvement in performance can be obtained at high compression ratios. As a step towards developing a more efficient system and based on insight obtained from simulations, a high compression ratio (9.2) engine is selected. This engine is coupled to a 3 kW alternator and operated on 100% biogas. Both strategies, i.e., premixing and manifold injection are implemented. The results show very high overall (chemical to electrical) efficiencies with a maximum value of 22% at 1.4 kW with the manifold injection strategy. The new manifold injection strategy proposed here is found to be clearly superior to the conventional premixing method. The main reasons are the higher volumetric efficiency (25% higher than that for the premixing mode of supply) and overall lean operation of the engine across the entire load range. Predictions show excellent agreement with measurements, enabling the model to be used as a tool for further study. Simulations suggest that a higher compression ratio (up to 13) and appropriate spark advance can lead to higher engine power output and efficiency.