An alarming number of compression ignition (CI) engines in the transport, mining and heavy engineering environments have been failing due to combustion irregularities within their combustion chambers. It has been found that diesel fuels containing contaminants or diesel fuels with poor lubricity characteristics lead to stickiness of diesel injector needles, which badly affects injector spray patterns resulting in the phenomenon of “cold combustion”. This study has been undertaken to develop a technique for detecting and preventing the damage resulting from this deviation in the combustion of a diesel engine. The technique has been formulated with a view to being as non intrusive as possible, so as not to require major modification of an existing test engine to accommodate the technique. The practice of monitoring individual cylinder exhaust gas temperatures (EGTs) proved to be an effective way of determining whether potentially destructive combustion abnormalities were taking place within the diesel engine. By recording these temperatures at certain stages during the engine’s operation, taking their average, and comparing each one to this average it is also possible to isolate the location of the combustion abnormality. This method proved to be most effective at full loads and maximum fuel delivery where combustion temperatures are highest and the effects of poor combustion are most noticeable and potentially damaging. The second goal was to develop a small, portable electronic device that makes use of the monitoring technique developed and provides a visual and audible alarm to notify a vehicle operator or technician of a combustion fault within a diesel engine. A Combustion Monitoring System (CMS) prototype was developed and tested on a small naturally aspirated engine at the University of Pretoria’s engine testing facilities. The prototype met its primary goal of detecting simulated combustion abnormalities under a variety of test conditions. It is envisaged that the monitoring techniques applied in developing the CMS unit may eventually be incorporated into the powerful processing abilities of the modern diesel Engine Control Unit (ECU). In its current form the CMS prototype is a useful tool in sensing combustion related malfunctions within a diesel engine and preventing damage from occurring. / Dissertation (MEng)--University of Pretoria, 2009. / Mechanical and Aeronautical Engineering / unrestricted

No description available.

Orientador: Luiz Fernando Milanez / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas / Made available in DSpace on 2018-07-16T07:09:02Z (GMT). No. of bitstreams: 1 Souza_EduardoGodoyde_M.pdf: 4233314 bytes, checksum: 431da8392afee63bfdeb9c898bb351a7 (MD5) Previous issue date: 1987 / Resumo: A partir de dados obtidos em ensaios de desempenho na tomada de potência de três tratores agrícolas foram propostos três métodos para a avaliação indireta do torque de motores diesel: medição do consumo de combustível, medição da temperatura dos gases de escape e medição da posição da alavanca de acionamento da bomba injetora. A medição do consumo de combustível foi feita utilizando-se um medidor digital com pré-fixação de volume de combustível a ser utilizado e leitura do tempo gasto. A variável independente, neste caso, para a modelagem do torque foi a massa de combustível injetada por cilindro e por ciclo. A temperatura dos gases de escape foi medida utilizando-se um termo-elemento. A variável independente, neste caso, foi a diferença entre a temperatura de escape e a temperatura do ar de admissão. A posição da alavanca de acionamento da bomba injetora foi avaliada através da rotação máxima livre do motor, sendo esta rotação tomada como a variável independente. A análise estatística dos resultados mostrou que na modelagem matemática, em todos os métodos, deveria ser incluida a rotação do motor que se mostrou significativa. Foram feitas considerações a respeito da utilização de cada método em função da precisão, custo e facilidade de adaptação. / Abstract: Three methods for indirect evaluation of the torque of diesel engines were proposed from data obtained in performance tests in the power take-off of agricultural tractors: measurement of the fuel consumption, measurement of exhaust gas temperature and measurement of the position of the fuel pump control lever. The fuel consumption was measured by means of a digital sensor that records the time taken for a fixed amount of fuel to be burned. The independent variable in this case for the mathematical modeling of the torque was the mass of fuel delivered per cylinder per cycle. The exhaust gas temperature was me1sured by a thermo-couple. The independent variable here was the difference between the exhaust temperature and the admission air temperature. The position of the fuel pump control lever was evaluated as a function of the engine maximum engine speed, with this speed being taken as the independent variable. A statistical analysis of the results indicated that in the mathematical modeling, for all methods, the engine speed should be included as an additional independent variable. Considerations were made regarding the utilization of each method as function of accuracy, costs and adaptability. / Mestrado / Mestre em Engenharia Mecânica

The impact of fuel drops on the walls of combustion chambers is unavoidable in direct-injection automotive engines. These drop-solid interactions can lead to splashing of the lubrication oil, its dilution or removal, which can damage the piston or the liner from dewetting. This can also cause irregular and inferior combustion or soot formation. Understanding the drop-splashing dynamics is therefore important, especially as modern IC engines are being down-sized to achieve higher thermal efficiency. Typical cylinders of IC engines contain metal liners on their walls, which have fine azimuthal grooves to support the lubricating oil as the piston moves inside the cylinder. In this thesis we study how these grooves affect the deposition or splashing of impacting diesel drops, while the solid surface is kept dry without the lubricating oil. For these experiments we use sections of actual cylinder liners and apply high-speed video imaging to capture the details of the drop impacts. The first set of experiments used normal impacts on horizontal substrates. These experiments include a range of drop sizes and impact velocities, to identify impact conditions in Reynolds and Weber number space where the transition from deposition to splashing occurs. We also study the maximum radial spreading factor of the impact lamella, finding about 8% larger spreading along the grooves than perpendicular to them. In the second set of experiments we look at the impact on inclined substrates, where the inclination angle is between 30o–60o. This produces strong asymmetry in the maximum spreading, with the tangential velocity governing the maximum radial motion. The inclined impacts change the splashing threshold, requiring larger impact velocities for splashing. The splashing threshold deviates quantitatively from earlier theories, but shows the same qualitative trends. Furthermore, a new splashing mechanism is observed, where the impact forms a prominent ejecta crown from the downstream edge. This crown ruptures first from the grooves at the sides and subsequently the capillarity detaches the downstream levitated liquid sheet from the substrate generating a myriad of splashed droplets. Preliminary observations with impacts on wet substrates show much stronger crown-formation from the lubricating oil film, with potential for dewetting.

The present manuscript discusses the use of two diesel injections in diesel-ignited propane dual fuel Low Temperature Combustion (LTC). Using propane fumigation into the intake runners of a single cylinder research engine, the maximum and minimum percent energy substitution (PES) values were obtained to be 90% and 53%, respectively at 3.3 bar BMEP. An optimal PES value of 80% was used to explore the effects of a secondary injection on the engine-out emissions. The secondary injection proved to have a strong influence on combustion phasing (CA50). As combustion is phased closer to TDC the IFCE shows and increase of 4% at 5 bar BMEP and 6% at 3.3 bar BMEP. Finally, a relationship between the IFCE and the CO to CO2 conversion was developed. An increase in the carbon to hydrogen ratio of the fuel shows a reduction of the CO output of the engine while the CO2 concentration increases. More importantly however, the CO to CO2 conversion shows a direct effect on the IFCE. It is shown that a decrease in CO emissions found in the engine-out emissions will correlate directly with an increase in the IFCE.

Various sub models of a multi-zone phenomenological model are developed by incorporating Dec’s conceptual model and Siebers’ mixing limited theory and validated with experiments. The spray penetration model, liquid length model and lift-off length model are verified with experiment data. The ignition delay model is then validated with experiment data at different injection timings and loads. The air entrainment model is based on Siebers’ jet theory. Sub models for the premixed heat release rate and diffusion burn rate are also included. The overall phenomenological model is at first used to match the motoring pressure curve. The important sub models are well validated independently and the phenomenological model is useful in simulating diesel spray combustion. Future work is needed to integrate these sub models and to resolve existing issues in temperature profiles of the preparing zone and liquid zone.

The addition of Tier 2 standards by United States Environmental Protection Agency (EPA) has increased focus on light-duty vehicle emissions. In this study, a diesel-electric hybrid vehicle was used for testing under the Challenge X program. The diesel engine was powered by a 20% soy-based biodiesel - 80% diesel blend, and the electric motor received its energy from a 330 volt Nickle Metal Hydride battery pack. The diesel engine, notorious for high emissions of nitrogen oxides (NOx) and particulate matter (PM), requires aftertreatment of these emissions to achieve Tier 2 EPA compliance. The primary focus of this thesis is use of a urea injection selective catalytic reduction (SCR) system to reduce NOx emissions. Also, a diesel particulate filter (DPF) was employed for PM reduction purposes. Significant decreases in both NOx and PM emissions were achieved.

No description available.

La tendencia actual de los Laboratorios de Control de Calidad es la implementación de métodos analíticos versátiles, rápidos, sensibles, precisos, simples, fáciles de operar y de bajo costo. Una de las maneras más efectivas de alcanzar tales características es la automatización y la ayuda de herramientas estadísticas aplicadas a la química. En este trabajo de tesis se presenta el desarrollo de nuevos métodos analíticos para la caracterización de muestras de combustibles diesel. En la primera parte del trabajo se realizó la cuantificación de glicerina en biodiesel, basándose en la automatización de la extracción y determinación del analito mediante Fluorescencia Molecular. Comprobamos que la determinación que se lleva a cabo en los laboratorios de análisis de rutina de combustibles usando cromatografía líquida, puede ser realizada de manera sencilla y con resultados similares usando el método propuesto, que posee una cámara de agitación automática y un Espectrofluorímetro. Continuando con la técnica de Fluorescencia, se hicieron espectros de fluorescencia sincrónica a muestras de biodiesel obtenidas de diferentes aceites comerciales (soja, girasol, etc.) con el objeto de hacer una clasificación de combustibles biodiesel con respecto a la oleaginosa de su procedencia: La información que producen los espectros antes mencionados, fue modelada mediante los algoritmos quimiométricos de clasificación SIMCA y SPA-LDA. También se utilizaron espectros de fluorescencia sincrónica para la determinación cuantitativa de parámetros de calidad. Se determinaron 4 parámetros de calidad simultáneamente (Porcentaje de Biodiesel, Número de cetanos, Calor de combustión, Color) a partir de un espectro de fluorescencia sincrónica. En la última parte de la tesis, se trabajó en la determinación cuantitativa de un aditivo presente en combustibles biodiesel/diesel. Se determinó el mejorador del número de cetanos, el 2-nitrato de etilhexilo a partir de espectros de fluorescencia de excitación - emisión. Esta relación entre los valores de fluorescencia y el contenido del aditivo mejorador de cetanos fue realizada mediante algoritmos quimiométricos de calibración multivariada. / The current trend of cuality control in laboratories is the implement of versatile, fast, sensitive, accurate, simple, easy to operate and inexpensive analytical methods. One of the most effective ways to achieve these features is the automation whith the statistical tools applied to chemistry help. In this thesis the development of new analytical methods for the characterization of diesel fuel samples is presented. In the first part, the quantification of glycerol in biodiesel was performed, based on automating the extraction and determination of analyte by molecular fluorescence. We found that the determination is carried out in the laboratories of routine analysis of fuels using liquid chromatography, can be performed easily and with similar results using the proposed method, which has an automatic stirring chamber adapted in a spectrofluorometer. Then the technique of synchronous fluorescence was used to obtain spectra from different commercial biodiesel oils (soybean, sunflower, etc.) samples in order to do a biodiesel fuel classification regarding its origin of oilseed: The information produced by the above mention spectra, was modelling using chemometric algorithms of classification, SIMCA and SPA-LDA. Synchronous fluorescence spectra for quantitative determination of quality parameters were also used. Simultaneously four quality parameters (Biodiesel content, Cetane Number, Heat of combustion, Color) from a synchronous fluorescence spectrum were determined. In the last part of the thesis, we worked on the quantitative determination of an additive in biodiesel / diesel fuels. The cetane number improver 2-ethylhexyl nitrate was determined from fluorescence excitation - emission spectra. This relationship between the fluorescence values and the content of the cetane improver additive was performed by multivariate chemometric calibration algorithms.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: To reduce exhaust gas emissions in diesel engines and for engine upgrade purposes the major parameters and equipment that should be looked at are boost pressure, intake charge temperature, combustion chamber design and fuel injection equipment. Boost pressure is governed by the turbo-charger; with high-efficiency variable geometry turbochargers, effective control is possible to increase airflow rate at all operating conditions of the engine. Efficient air-to-air inter-cooling results in the engine being filled with a cooler air charge that will influence engine durability and heat rejection to the cooling system. The main objective of the investigation is to look at the influence of boost pressure and intake charge temperature on diesel combustion to better understand the processes where boost pressure is increased and intake charge temperature reduced to increase the brake mean effective pressure of the engine and reduce emissions generation. By running an engine at different intake boost pressures and intake charge temperatures a 25-point matrix was formed at three different operating conditions. On completion of the engine testing, data processing and data evaluation, a number of important conclusions were made about the behaviour of the engine running under different conditions. This enabled the researcher to understand how boost pressure and intake charge temperature influence engine power output, fuel consumption, engine durability and exhaust gas emissions. The opinion is proved when, in most cases, the 75 test points were used to build multiple linear regression models to determine which engine parameters (dependent variables) have a significant effect on emissions generation and durability parameters. From the data it is evident that boost pressure has a positive influence on most engine parameters, as an increase in boost pressure results in an increase in air mass flow through the engine. An increase in air mass flow reduces combustion chamber gas temperature as the result of an increase in excess air ratio during combustion. A further result of the increase in excess air ratio is that less soot is formed during the first part of combustion and more soot and partly decomposed Hydrocarbon (HC) compounds are oxidised during the late combustion phase. Therefore, with an increase in boost pressure, Bosch smoke emissions reduce, but with a change in intake air temperature no difference in smoke concentration is seen except at the very low boost pressure and very high boost temperature test points where low air/fuel ratios exist and the slight increase in air-flow rate as a result of lower air inlet temperature has a big influence. Nitric Oxide (NO) emissions, on the other hand, are more dependent on intake air temperature than on boost pressure, which was proved in the multiple regressions modelling performed on the test data. The flame zone and the post-flame zone temperature play the dominant role in NO formation. As explained in the results discussion on NO formation, intake air temperature influences the ignition mixture temperature and the subsequent flame zone temperature. A lower intake air condition results in longer ignition delay and increases the initial rate of combustion. / AFRIKAANSE OPSOMMING: Die hoofparameters en toerusting wat in ag geneem moet word om uitlaatgasemissies in dieselenjins te verminder en om enjinkraguitset te verhoog, is inlaatdruk, inlaat lugtemperatuur, verbrandingskamerontwerp en brandstofinspuittoerusting. Inlaatdruk word beheer deur die turb-aanjaer. Met hoë effektiwiteit, veranderlike geometrie turboaanjaging, is effektiewe beheer moontlik om lugvloei-tempo deur die enjin te verhoog onder alle enjinwerkstoestande. Effektiewe lug-tot-lug tussenverkoeling laat die enjin met koeler inlaatlug vul, wat 'n uitwerking het op enjinlewensduur en hitte-verlies na die verkoelingsstelsel. Die hoofdoel van die navorsing is om die invloed van inlaatdruk en inlaat lugtemperatuur op dieselverbranding te ondersoek. Sodoende kry die navorser 'n beter begrip omtrent die prosesse waar inlaatdruk verhoog en inlaat lugtemperatuur verlaag word, om rem-gemiddelde effektiewe druk van die enjin te verhoog en uitlaatgas emissies te verlaag. 'n 25-punt matriks is opgestel deur die enjin by verskillende inlaatdrukke en inlaat lugtemperture te opereer, en by drie verskillende wringkragwerkstoestande. 'n Aantal belangrike gevolgtrekkings is gemaak omtrent enjinwerking onder verskillende werkstoestande na voltooiing van die enjintoetse, dataverwerking en data-evaluering. Sodoende het die navorser bepaal hoe inlaatdruk en inlaat lugtemperatuur kraglewering, brandstofverbruik, enjinlewensduur en uitlaatgasemissies beïnvloed. Om bogenoemde begrippe verder te ondersteun is 'n meervoudige, lineëre regressiemodel opgestel om te bepaal watter enjinparameters (afhanklike veranderlikes) 'n wesenlike effek op emissiegenerasie en lewensduur het. Van die data word afgelei dat inlaatdruk 'n positiewe effek op die meeste enjinparameters het, omdat hoër inlaatdruk die lugvloeitempo deur die enjin verhoog. Hoër lugmassavloei verminder verbrandingsgastemperatuur as gevolg van 'n hoër oortollige lugverhouding tydens verbranding. 'n Verdere gevolg van 'n hoër oortollige lugverhouding is dat minder roet gevorm word gedurende die eerste verbrandingsfase en meer roet en gedeeltelik verbrande koolwaterstofverbindings oksideer gedurende die finale verbrandingsfase. Dus, met 'n hoër inlaatdruk word Bosch rookemmissies verlaag. Geen wesenlike verandering in rookkonsentrasies word egter gesien met 'n verandering in inlaatlugtemperatuur nie, behalwe by baie lae inlaatdruk- en hoë inlaat lugtemperatuur-toetskondisies waar lae lug/brandstofverhoudings bestaan en 'n klein toename in lugmassavloei as gevolg van laer inlaat lugtempertuur'n groot invloed het. Stikstofmonoksied (NO) emissies is meer afhanklik van inlaat lugtemperatuur as inlaatdruk. Dit is bewys in die meervoudige regressiemodel. Die vlamsone- en die navlamsone- temperatuur speel 'n groot rol in NO vorming. Inlaat lugtemperatuur beïnvloed die temperatuur van die onstekingsmengsel en die daaropvolgende vlamsonetemperatuur. 'n Laer inlaat lugtemperatuur veroorsaak 'n langer onstekingsvertraging en verhoog die aanvanklike verbrandingstempo.