Dissertations / Theses on the topic 'CNG Engines'

Currently there is a large interest in alternative transport fuels. There are two underlying reasons for this interest: the desire to decrease the environmental impact of transports and the need to compensate for the declining availability of petroleum. In the light of both these factors, the CNG-diesel dual fuelengine is an attractive concept. The primary fuel of the dual fuel engine is methane, which can be derived both from renewables and from fossil sources. Methane from organic waste, commonly referred to as biomethane, can provide a reduction in greenhouse gases unmatched by any other fuel. Furthermore, fossil methane, natural gas, is one of the most abundant fossil fuels.Thedual fuelengine is, from a combustion point of view, a hybridof the diesel and theOtto-engineand it shares characteristics with both. From a market standpoint, the dual fuel technology is highly desirable; however, from a technical point of view it has proven difficult to realize. The aim of this project was to identify limitations to engine operation, investigate these challenges, and ,as much as possible, suggest remedies. Investigations have been made into emissions formation, nozzle-hole coking, impact of varying in-cylinder air motion, behavior and root causes of pre-ignitions, and the potential of advanced injection strategies and unconventional combustion modes. The findings from each of these investigations have been summarized, and recommendations for the development of a Euro 6 compliant dual fuel engine have been formulated. Two key challenges must be researched further for this development to succeed: an aftertreatment system which allows for low exhaust temperatures must be available, and the root cause of pre-ignitions must be found and eliminated.

QQC 20140915

Master’s thesis deals with comparsion and rating the compressed natural gas as an aircraft piston engine fuel. An information search of conventional fuels and differences of the fuel systems for AVGAS and CNG is included. Next part describes the aircraft and its engine on which is the mathematic model based. After that perfomance and consumption data are calculated for both fuels and the results are then compared. At the end of the thesis, a design of the CNG fuel system with components selection is described.

One of the major environmental challenges facing our planet and living beings is the global warming. This phenomena, known as the gradual increase in the overall temperature of earth's atmosphere is mostly caused by the greenhouse eect which is a result of increased levels of greenhouse gases. Major constitutes of these gases are Carbon Dioxide (CO2) and Nitrogen Oxides (NOx). Transportation sector is responsible for releasing a signicant portion of these gases into the atmosphere. In recent decades, many endeavors such as using alternative fuels and modications in engine cycles have been made to control the amount of pollutants emitted from internal combustion engines. In this work, the impact of adding humidity to the input Oxidizer stream on reduction of NOx and Carbone Dioxide (CO2) of a CNG engine has been studied. With the addition of the humidity, the combustion temperature will be reduced which improves the engines lifespan. Non-Premixed combustion process in a single cylinder is simulated using the STAR CCM+ software from CD-Adapco company, using the Presumed Probability Density Function (PPDF) combustion model which is an accurate model for combustion. Simulation results indicate with 10% humid air, signicant reductions in NOx and CO2 are obtained, with a moderate increase in CO output. Adding humidity results in total emission reduction.

The master´s thesis is focused on the design of the multi-point CNG injection for the VW 1.4 TSI intake manifold turbocharged spark ignited engine. The 3D model that was created using Autodesk Inventor Professional 2012 is based on the real intake manifold. This model served as an input for CFD analyses of mixing CNG with air. These were made in STAR-CCM+ software.

Heavy duty on-road vehicles represent one of the largest sources of NO _x emissions and fuel consumption in North America. Heavy duty vehicles are predominantly fueled with diesel, with the recent interest in natural gas (NG) systems. As emissions and greenhouse gas regulations continue to tighten new opportunities for advanced fleet specific heavy duty vehicles are becoming available with improved fuel economy. NO_x emissions have dropped 90% for heavy duty vehicles with the recent 2010 certification limit. Additional NO_x reductions of another 90% are desired for the South Coast Air basin to meet its 2023 NO_x inventory requirements and the California optional low NO_x standard in 2015.

One of the difficulties in quantifying NO_x emissions at the levels proposed in this research (90% of the 2010 certification level ~ 0.02 g/bhp-hr) is the measurement methods are approaching their detection limit to sufficiently quantify NO_x emissions. Three upgraded NO _x measurement methods were considered which include a raw NO_x measurement integrated with real time exhaust flow, a real-time ambient correction approach, and a trace level ambient analyzer for accurate bag analysis. In summary the improved methods varied in their success where the raw sampling approach showed to be the most accurate and precise over the rage of conditions tested.

The ISL G NZ 8.9 liter NG engine met and exceeded the target NO _x emissions of 0.02 g/bhp-hr. This engine significantly reduced 97%–100% of NO_x emissions compared with previous ISL G 8.9 engines. The NO_x emissions decreased as the duty cycle was decreased which was the opposite trend for the diesel vehicles. It is expected NG vehicles could play a role in the reduction of the south coast NO_x inventory problem given their near zero emission factors demonstrated.

This master's thesis deals with the process of machining a forged connecting rod in cooperation with the company Zetor Tractors a.s. The first chapter of the thesis is focused on a detailed introduction of the company. The second chapter includes an elaborate analysis of the technical documentation and requirements concerning the making process of the subject of study, specifically the construction of the connecting rod. In the third chapter, the current production technology is discussed and described in detail. The aim of the fourth chapter is to propose an innovative technology which can be used for the production of connecting rods in the required quality. The fifth chapter is aimed at testing the newly designed technology. In the final, sixth, chapter, a technical and economical evaluation of the proposed procedure is performed.

In the development of advanced driver assistance systems, computer vision problemsneed to be optimized to run efficiently on embedded platforms. Convolutional neural network(CNN) accelerators have proven to be very efficient for embedded camera platforms,such as the ones used for automotive vision systems. Therefore, the focus of this thesisis to evaluate the efficiency of a CNN on a future embedded heterogeneous processingdevice. The memory size in an embedded system is often very limited, and it is necessary todivide the input into multiple tiles. In addition, there are power and speed constraintsthat needs to be met to be able to use a computer vision system in a car. To increaseefficiency and optimize the memory usage, different methods for CNN layer fusion areproposed and evaluated for a variety of tile sizes. Several different layer fusion methods and input tile sizes are chosen as optimal solutions,depending on the depth of the layers in the CNN. The solutions investigated inthe thesis are most efficient for deep CNN layers, where the number of channels is high.

The master thesis deals with design and manufacturing of rear right formula hub on CNC machining centre by using modern CAD/CAM technologies. The theoretical part is focused on description and characterization of milling technology and machinability of aluminium alloys. The practical part is focused on the designing formula hub in CAD software Pro/Engineer, proposing machining strategies by using CAM software PowerMILL and manufacturing on CNC machine. There is technical economic evaluation of the machined part at the end of the thesis.

This work describes a tool for extraction of features in 2D images applied to industrial automation. The method uses techniques implemented targeting of images into pieces model as detection of edges in the extraction of spatial coordinates of the image and import applications in CAD (Computer-Aided Design) for the generation of programmers for Computer Numerical Control (CNC). This work is to copy a particular model (image) from an existing object, which features a process of reverse engineering. An initial prototype was developed using the Java language with the Eclipse IDE and library for handling complex images, the API Java Advanced Image (JAI). For the acquisition of parts to be machined, was prepared an environment of lighting to highlight areas of interest improving the luminance of the same and enabling the application of techniques developed in this prototype. Different operators for detecting edges were exploited in order to implement the best technical and that best represent the real piece. A new technique of targeting the prototype was adapted from the integration of technology Java / MatLab and with the acquisition of images through technical Multi-flash. After the application of different processing techniques, a text file containing the coordinates of the image (piece) is generated and imported into CAD. In the CAD environment, runs calculating the trajectory of the tool that identifies the geometry of the piece and defines the path of the tool in the generation of CNC program for breeding the same. Results presented and evaluation of the tool demonstrates the feasibility of applying the automated system developed as part of parts to play in numerical control machines.
O presente trabalho descreve uma ferramenta para extração de características em imagens 2D aplicado à automação industrial. O método implementado utiliza técnicas de segmentação de imagens em peças modelo, como detecção de bordas, na extração das coordenadas espaciais da imagem e importação em aplicativos CAD (Computer-Aided Design) para a geração de programas de Comando Numérico Computadorizado (CNC). Este trabalho consiste em copiar um determinado modelo (imagem) partindo de um objeto já existente, o que caracteriza um processo de engenharia reversa. Um protótipo inicial foi desenvolvido usando a linguagem Java com o IDE Eclipse e a biblioteca para manipulação de imagens complexas, o API Java Advanced Image (JAI). Para a aquisição das peças a serem usinadas, foi elaborado um ambiente de iluminação a fim de ressaltar áreas de interesse melhorando a luminância das mesmas e viabilizando a aplicação das técnicas desenvolvidas nesse protótipo. Diferentes operadores de detecção de bordas foram explorados, a fim de aplicar a melhor técnica e que melhor representasse a peça real. Uma nova técnica de segmentação foi adaptada ao protótipo, a partir da integração da tecnologia Java/MatLab e com a aquisição de imagens através da técnica Multi-flash. Após a aplicação de diferentes técnicas de processamento, um arquivo texto contendo as coordenadas da imagem (peça) é gerado e importado no CAD. No ambiente CAD, é executado o cálculo da trajetória da ferramenta que identifica a geometria da peça e define o caminho da ferramenta na geração do programa CNC para reprodução da mesma. Resultados apresentados e a avaliação da ferramenta demonstram a viabilidade de aplicação do sistema desenvolvido como parte automatizada para reprodução de peças em máquinas de comando numérico.

In-cylinder fuel-air mixing in a compressed natural gas (CNG)-fuelled, single-cylinder, spark-ignited engine is analysed using a transient three-dimensional computational fluid dynamic model built and run using STAR-CD, a commercial CFD software. This work is motivated by the need for strategies to achieve improved performance in engines utilizing gaseous fuels such as CNG. The transient in-cylinder fuel-air mixing is evaluated for a port gas injection fuelling system and compared with that of conventional gas carburetor system. In this work pure methane is used as gaseous fuel for all the computational studies. It is observed that compared to the premixed gas carburetor system, a substantial level of in-cylinder stratification can be achieved with the port gas injection system. The difference of more than 20% in mass fraction between the rich and lean zones in the combustion chamber is observed for the port gas injection system compared to less than 1% for the conventional premixed system. The phenomenon of stratification observed is very close to the “barrel stratification” mode. A detailed parametric study is undertaken to understand the effect of various injection parameters such as injection location, injection orientation, start of injection, duration of injection and rate of injection. Furthermore, the optimum injection timing is evaluated for various load-speed conditions of the engine. It is also observed that the level of stratification is highest at 50% engine load with a reduced level at 100% load. For low engine loads, the level of stratification is observed to be very low. To analyse the effect of stratification on engine performance, the in-cylinder combustion is modeled using the extended coherent flame model(ECFM). For simulating the ignition process, the arc and kernel tracking ignition model(AKTIM) is used. The combustion model is first validated with measured in-cylinder pressure data and other derived quantities such as heat release rate and mass burn fraction. It is observed that there is a good agreement between measured and simulated values. Subsequently, this model is use to simulate both premixed and stratified cases. It is observed that there is a marginal improvement in terms of overall engine efficiency when the stoichiometric premixed case is compared with the lean stratified condition. However, a major improvement in performance is observed when the lean stratified case is compared with lean premixed condition. The stratified case shows a faster heat release rate which could potentially translate to lower cycle-to-cycle variations in actual engine operation. Also, the stratified cases show as much as 20% lower in-cylinder NOx emissions when compared with the conventional premixed case at the same engine load and speed, underscoring the potential of in-cylinder stratification to achieve improved performance and lower NOx emissions.

Yes
The natural gas as an alternative fuel has economical and environmental benefits. Bi-fuel engines powered by gasoline and compressed natural gas (CNG) are an intermediate and alternative step to dedicated CNG engines. The conversion to bi-fuel CNG engine could be a short-term solution to air pollution problem in many developing countries. In this paper a mathematical model of a bi-fuel four-stroke spark ignition (SI) engine is presented for comparative studies and analysis. It is based on the two-zone combustion model, and it has the ability to simulate turbulent combustion. The model is capable of predicting the cylinder temperature and pressure, heat transfer, brake work , brake thermal and volumetric efficiency, brake torque, brake specific fuel consumption (BSFC), brake mean effective pressure (BMEP), concentration of CO2, brake specific CO (BSCO) and brake specific NOx (BSNOx). The effect of engine speed, equivalence ratio and performance parameters using gasoline and CNG fuels are analysed. The model has been validated by experimental data using the results obtained from a bi-fuel engine. The results show the capability of the model in terms of engine performance optimization and minimization of the emissions. The engine used in this study is a typical example of a modified bi-fuel engine conversion, which could benefit the researchers in the field.

Homogeneous Charge Compression Ignition (HCCI) operation is desirable for its high thermal efficiency and low emissions of NOx and particulates. Difficulty with cold starting and maximum achievable speed/load highlight the desire for mode-switching to traditional spark ignition (SI) operation. Mode-switching between SI and HCCI is investigated using only actuation of throttle, CNG injector pulse width, and CNG injection timing on a single cylinder CFR engine. Open-loop control achieves a one cycle mode-switch between two adjustable IMEP levels. Sequences are repeatable as demonstrated by 10 mode-switches with the same inputs. Performance is evaluated using a developed mode-switch performance criterion (MSPC) by considering duration between steady-states of operation, smoothness of IMEP, and knock based on maximum rate of pressure rise. Comparing the results with subjective analysis (the current standard) reveals good correlation. Throughout development, mode-switching performance is shown to improve by a factor of 60.

碩士
國立暨南國際大學
資訊管理學系
106
Searching holders manually in catalogs to make a pair of CNC holder and tool is time wasting and inefficient. As there are no standards for the parameters of holders, this searching can even ineffective in multi-vendor environment. In this thesis, we design and implement a search engine for multi-vendor tool holder based on standardized metadata. The search engine has following advantages: ・CNC tool holders can be searched with standardized data. ・Using metadata to render input view and to generate an exclusive data structure of a CNC tool holder. ・Showing original parameters’ name at input and result views to prevent confusion between the detail images of CNC tool holder and the standardized parameters. ・The scalability of metadata makes it easy to add properties for new processes without modifying code. ・Providing Web API that can be integrated to related services such as Inventory Control System or Interference Prevention System.

Dissertação de mestrado integrado em Engenharia Mecânica
Desde o aparecimento dos primeiros motores de combustão interna, estes têm sido constantemente alvo de evoluções em função das necessidades do meio ao qual se destinam, seja a procura por melhor fiabilidade, por maiores potências ou mesmo pela otimização dos mesmos de modo a tornar o seu custo de produção mais sustentável. Atualmente existe uma crescente preocupação pelos problemas ambientais, bem como pela escassez das reservas de petróleo, o que associado à crise económico-financeira vivida torna a procura por uma maior eficiência energética dos motores de combustão interna, o principal campo de evolução dos mesmos. Neste contexto, surge o conceito de motor sobre-expandido, sendo este um tipo de motor que apresenta rendimentos superiores aos motores convencionais, permitindo deste modo registar valores de consumos e emissões de poluentes francamente inferiores aos dos motores convencionais. O presente trabalho tem como finalidade o fabrico de um motor de combustão interna, mais concretamente o UMotor. Este é um motor de ciclo sobre-expandido que vem sendo desenvolvido há já alguns anos no Departamento de Engenharia Mecânica da Universidade do Minho e que se destina a equipar o EconomicUM. O trabalho apresentado faz inicialmente um enquadramento teórico acerca dos motores de ciclo sobre-expandido, dando a conhecer a sua origem, o seu principio de funcionamento e o seu papel na sociedade atual. Posteriormente, o trabalho é focado no desenvolvimento e fabrico de alguns componentes do UMotor, tais como o cárter, a árvore de cames, os balanceiros, a cambota e o coletor de admissão. Ao longo do trabalho apresentado são dadas a conhecer as diferentes fases no desenvolvimento dos componentes, desde o projeto dos mesmos utilizando ferramentas CAD/CAM, aos processos de fabrico utilizados bem como os procedimentos a ser adotado de modo a que no futuro se concretize a realização de um protótipo funcional do motor.
Since internal combustion engines made their early appearance, continuous evolutions took place in order to fulfill the requests of their application domains, whether pursuing reliability improvement, higher engine power or even manufacturing optimization and cost sustainability. Nowadays there is a growing concern about environmental issues, including oil reserves shortage, economic and financial crisis impact, so driving critical increase of energetic efficiency in internal combustion engines, as a field of study. In this context arises the concept of over-expanded engine, for it shows higher efficiency, allowing less fuel consumption and lower polluting emissions than conventional engines. The present work describes the manufacturing constraints and solutions of an experimental internal combustion engine, the UMotor. This is an over-expanded cycle engine under development in the Department of Mechanical Engineering of University of Minho, to equip the EconomicUM, a formula Shell® prototype vehicle. A theoretical overview is presented about the over-expanded cycle engines, describing its principles of operation and their possibilities in the society. The work is focused on the development and manufacturing of components of the engine, including the crankcase, the camshaft, the rocker arms, the crankshaft and the intake manifold. The work presents an overview of the actual stage in the development of components, including modifications to the project using CAD/CAM tools, and describes the manufacturing processes and procedures to be undertaken in the near future to achieve a fully functional prototype engine.