Indiana University-Purdue University Indianapolis (IUPUI) / Natural gas substitution for diesel can result in significant reduction in pollutant emissions. Based on current fuel price projections, operating costs would be lower. With a high ignition temperature and relatively low reactivity, natural gas can enable promising approaches to combustion engine design. In particular, the combination of low reactivity natural gas and high reactivity diesel may allow for optimal operation as a reactivity-controlled compression ignition (RCCI) engine, which has potential for high efficiency and low emissions. In this computational study, a lean mixture of natural gas is ignited by direct injection of diesel fuel in a model of the heavy-duty CAT3401 diesel engine. Dual-fuel combustion of natural gas-diesel (NGD) may provide a wider range of reactivity control than other dual-fuel combustion strategies such as gasoline-diesel dual fuel. Accurate and efficient combustion modeling can aid NGD dual-fuel engine control and optimization. In this study, multi-dimensional simulation was performed using a nite-volume computational code for fuel spray, combustion and emission processes. Adaptive mesh refinement (AMR) and multi-zone reaction modeling enables simulation in a reasonable time. The latter approach avoids expensive kinetic calculations in every computational cell, with considerable speedup. Two approaches to combustion modeling are used within the Reynolds averaged Navier-Stokes (RANS) framework. The first approach uses direct integration of the detailed chemistry and no turbulence-chemistry interaction modeling. The model produces encouraging agreement between the simulation and experimental data. For reasonable accuracy and computation cost, a minimum cell size of 0.2 millimeters is suggested for NGD dual-fuel engine combustion. In addition, the role of different chemical reaction mechanism on the NGD dual-fuel combustion is considered with this model. This work considers fundamental questions regarding combustion in NGD dual-fuel combustion, particularly about how and where fuels react, and the difference between combustion in the dual fuel mode and conventional diesel mode. The results show that in part-load working condition main part of CH4 cannot burn and it has significant effect in high level of HC emission in NGD dual-fuel engine. The CFD results reveal that homogeneous mixture of CH4 and air is too lean, and it cannot ignite in regions that any species from C7H16 chemical mechanism does not exist. It is shown that multi-injection of diesel fuel with an early main injection can reduce HC emission significantly in the NGD dual-fuel engine. In addition, the results reveal that increasing the air fuel ratio by decreasing the air amount could be a promising idea for HC emission reduction in NGD dual-fuel engine, too.

Le développement de stratégies de combustion innovantes est nécessaire aujourd’hui pour répondre aux réglementations de plus en plus intransigeantes qui fixent les seuils d’émissions polluantes par les véhicules neufs. Parmi ces stratégies, l’approche Dual Fuel a montré un fort potentiel dans la réduction des émissions tout en maintenant des niveaux de rendement élevés. Le concept Dual Fuel est fondé sur la formation d’un mélange homogène d’air et d’un carburant volatile (essence, méthane, éthanol...) allumé par une injection directe d’un carburant à fort cétane (de type gazole) dans la chambre de combustion. Une compréhension détaillée des différents processus de combustion est primordiale pour aider au développement des stratégies Dual Fuel concrètes. Dans ce contexte, le développement d’un modèle adapté, couplé à des mesures expérimentales réalisées sur moteur optique, est indispensable pour optimiser la combustion Dual Fuel. Une étude numérique, fondée sur le couplage d’un modèle de combustion turbulente dédié à la propagation de flamme dans des milieux stratifiés (ECFM3Z) et un modèle de chimie tabulée pour la prédiction de l’auto-inflammation (TKI), a été menée afin d’évaluer la capacité des modèles existants à prédire les différents régimes de combustion qui pourraient exister dans les stratégies Dual Fuel. Des critères de transition ont été ajoutés et évalués afin d’améliorer le couplage des deux modèles et d’assurer la transition entre l’auto-inflammation et la propagation de flamme. D’autre part, l’étude expérimentale sur un moteur à accès optiques a permis d’étudier des variations de richesse, de carburant de prémélange et de taux de dilution et de caractériser de manière fine les mécanismes de la combustion Dual Fuel afin de servir de base de données aux développements de modèles CFD. / Advanced combustion strategies are required in response to increasingly stringent worldwide regulations governing exhaust gas emissions in the transport sector. Among these strategies, the Dual Fuel approach has shown potential to reduce engine-out pollutant emissions without penalizing combustion efficiency. The Dual Fuel concept relies on the formation of a homogeneous mixture of air with a highly volatile fuel (gasoline, methane, ethanol...) which is ignited by direct injection of a high-cetane fuel (Diesel fuel) in the combustion chamber. An improved understanding of the underlying physical phenomena and a detailed insight of the predominant combustion regime(s) are required in order to advance the development of the Dual Fuel combustion strategies. In this context, numerical modeling and optical engine measurements are combined to investigate Dual Fuel combustion. A numerical study, based on the coupling between a turbulent combustion model for flame propagation in stratified mixtures (ECFM3Z) and a tabulated kinetics model for auto-ignition (TKI), was conducted to evaluate the capacity of the existing models to cope with the various combustion regimes that might exist in Duel Fuel combustion strategies. Transition criteria were added and evaluated in order to improve the coupling between the two models and to better predict the transitions between auto-ignition and flame propagation. In addition, an experimental investigation, including equivalence ratio, premixed fuel and dilution variations, was performed in an optical engine. The objective was to apply advanced optical diagnostic techniques to thoroughly characterize the Dual Fuel combustion process and thus enhancing CFD model developments.

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.

The goal of the present work is to develop an open architecture engine controller to operate a production model, heavy-duty diesel engine. Where OEM engine control units (ECUs) are inflexible, this controller is designed to provide the hardware and software flexibility required to facilitate dualuel combustion research. This thesis includes thorough descriptions of the hardware and software development required to interface with all engine sensors and actuators. To establish baseline control settings for the open controller, OEM ECU responses are mapped over a range of speeds and loads. This information is used to calibrate the open controller. Comparison tests considering speed, load, and emissions are performed to ensure the open controller provides a close approximation of OEM engine operation. The results of the tests confirm that the open controller provides full control of the engine with baseline settings close to those of the OEM ECU.

Dual fuel combustion is one strategy to achieve low oxides of nitrogen and soot emissions while maintaining the fuel conversion efficiency of IC engines. However, it also suffers from high engine-out carbon monoxide and unburned hydrocarbon emissions, and the incidence of knock at high loads. The present work focused on CFD simulation of diesel-methane dual fuel combustion in a single-cylinder research engine (SCRE). For pure diesel combustion, a load sweep of 2.5 bar brake mean effective pressure (BMEP) to 7.5 bar BMEP was performed at a constant engine speed of 1500 rpm and a diesel injection pressure of 500 bar. For diesel-methane dual fuel combustion, a methane percent energy substitution sweep was performed from 30% to 90 % at 1500 rpm, 3.3 bar BMEP, 500 bar Pinj, and 355 crank angle degrees (CAD) diesel injection timing. Combustion, performance, and emissions results are presented and compared with experimental data where possible.

The goal of this study is to assess conventional and low temperature dual fuel combustion in light- and heavy-duty multi-cylinder compression ignition engines in terms of combustion characterization, performance, and emissions. First, a light-duty compression ignition engine is converted to a dual fuel engine and instrumented for in-cylinder pressure measurements. The primary fuels, methane and propane, are each introduced into the system by means of fumigation before the turbocharger, ensuring the airuel composition is well-mixed. Experiments are performed at 2.5, 5, 7.5, and 10 bar BMEP at an engine speed of 1800 RPM. Heat release analyses reveal that the ignition delay and subsequent combustion processes are dependent on the primary fuel type and concentration, pilot quantity, and loading condition. At low load, diesel-ignited propane yields longer ignition delay periods than diesel-ignited methane, while at high load the reactivity of propane is more pronounced, leading to shorter ignition delays. At high load (BMEP = 10 bar), the rapid heat release associated with diesel-ignited propane appears to occur even before pilot injection, possibly indicating auto-ignition of the propane-air mixture. Next, a modern, heavy-duty compression ignition engine is commissioned with an open architecture controller and instrumented for in-cylinder pressure measurements. Initial diesel-ignited propane dual fuel experiments (fumigated before the turbocharger) at 1500 RPM reveal that the maximum percent energy substitution (PES) of propane is limited to 86, 60, 33, and 25 percent at 5, 10, 15, and 20 bar BMEP, respectively. Fueling strategy, injection strategy, exhaust gas recirculation (EGR) rate, and intake boost pressure are varied in order to maximize the PES of propane at 10 bar BMEP, which increases from 60 PES to 80 PES of propane. Finally, diesel-ignited propane dual fuel low temperature combustion (LTC) is implemented using early injection timings (50 DBTDC) at 5 bar BMEP. A sweep of injection timings from 10 DBTDC to 50 DBTDC reveals the transition from conventional to low temperature dual fuel combustion, indicated by ultra-low NOx and smoke emissions. Optimization of the dual fuel LTC concept yields less than 0.02 g/kW-hr NOx and 0.06 FSN smoke at 93 PES of propane.

Visando a redução de poluentes emitidos pelos motores de combustão interna com ignição por compressão, que operam conforme o ciclo diesel, foram desenvolvidos nos últimos anos dispositivos para a operação destes motores com novos combustíveis, que além da redução de poluentes barateariam o custo de operação, devido à oportunidade de utilização de alguns combustíveis com boa disponibilidade. No presente estudo analisa-se a operação do motor diesel utilizando gás natural como combustível. Neste caso utiliza-se o óleo diesel apenas como combustível piloto, que será responsável pela ignição do segundo combustível, o gás natural. Em diversas publicações constata-se o ganho ambiental e econômico desta aplicação, porém nada é comentado em relação à alteração de índices de confiabilidade e surgimento de novos modos de falha. Neste trabalho verifica-se através de ferramentas de análise de confiabilidade, tais como a análise do tipo FMEA e Árvore de falhas, quais os principais modos de falha que serão inseridos no motor de combustão interna do tipo diesel quando este passa a operar como bi-combustível, com gás natural. Para tanto, necessita-se subdividir o motor diesel em subsistemas mostrando sua estruturação em árvores funcionais e integrando o kit diesel gás neste sistema. A partir da análise de confiabilidade verifica-se a probabilidade de ocorrência de novos modos de falha, que necessitarão da elaboração de novos planos de manutenção ou mesmo alterações no projeto do subsistema de injeção de gás natural. / In order to reduce pollutants emissions from internal combustion engines with compression bend ignition, designed to operate as the Diesel cycle, it has been developed in recent years devices for the addition of new fuels, which in addition to reducing pollutants could lower the cost of operation, due to the possibility of use of some fuels with good availability. In this case it is used only the diesel oil as the pilot flame, which is responsible for the ignition of the second fuel, the natural gas. Many publications discuss the environmental and the economic gain with the use of natural gas as fuel application, however nothing is said about the change of reliability indexes and the appearance of new failure modes in the engine. In this study through system reliability analysis tools such as Faillure Mode Effects and Analisys and Fault tree analysis it is analysed, which are the main failure modes that are inserted into the internal combustion engine when it comes to operate as dual fuel. For that analyses it is necessary to split the engine into subsystems showing its functional trees and integrating diesel gas kit in this system. New failure modes appear with greater severity than the existing in the traditional diesel engine system, leading to new design and maintenance practices. The end user, according to his need, will have one more parameter to choose whether to adopt a Diesel Gas system.

Visando a redução de poluentes emitidos pelos motores de combustão interna com ignição por compressão, que operam conforme o ciclo diesel, foram desenvolvidos nos últimos anos dispositivos para a operação destes motores com novos combustíveis, que além da redução de poluentes barateariam o custo de operação, devido à oportunidade de utilização de alguns combustíveis com boa disponibilidade. No presente estudo analisa-se a operação do motor diesel utilizando gás natural como combustível. Neste caso utiliza-se o óleo diesel apenas como combustível piloto, que será responsável pela ignição do segundo combustível, o gás natural. Em diversas publicações constata-se o ganho ambiental e econômico desta aplicação, porém nada é comentado em relação à alteração de índices de confiabilidade e surgimento de novos modos de falha. Neste trabalho verifica-se através de ferramentas de análise de confiabilidade, tais como a análise do tipo FMEA e Árvore de falhas, quais os principais modos de falha que serão inseridos no motor de combustão interna do tipo diesel quando este passa a operar como bi-combustível, com gás natural. Para tanto, necessita-se subdividir o motor diesel em subsistemas mostrando sua estruturação em árvores funcionais e integrando o kit diesel gás neste sistema. A partir da análise de confiabilidade verifica-se a probabilidade de ocorrência de novos modos de falha, que necessitarão da elaboração de novos planos de manutenção ou mesmo alterações no projeto do subsistema de injeção de gás natural. / In order to reduce pollutants emissions from internal combustion engines with compression bend ignition, designed to operate as the Diesel cycle, it has been developed in recent years devices for the addition of new fuels, which in addition to reducing pollutants could lower the cost of operation, due to the possibility of use of some fuels with good availability. In this case it is used only the diesel oil as the pilot flame, which is responsible for the ignition of the second fuel, the natural gas. Many publications discuss the environmental and the economic gain with the use of natural gas as fuel application, however nothing is said about the change of reliability indexes and the appearance of new failure modes in the engine. In this study through system reliability analysis tools such as Faillure Mode Effects and Analisys and Fault tree analysis it is analysed, which are the main failure modes that are inserted into the internal combustion engine when it comes to operate as dual fuel. For that analyses it is necessary to split the engine into subsystems showing its functional trees and integrating diesel gas kit in this system. New failure modes appear with greater severity than the existing in the traditional diesel engine system, leading to new design and maintenance practices. The end user, according to his need, will have one more parameter to choose whether to adopt a Diesel Gas system.

A 12.9 L heavy duty compression ignition engine was tested with strategies for dual fuel optimization. The effects of varied intake manifold pressure as well as split-injection strategies at a load of 5 bar BMEP and 85 PES were observed. These results were used to allow testing of split-injection strategies at a higher load of 10 bar BMEP at 70 PES that were void of MPRR above 2000 kPa/CAD. The split-injection strategies at 5 bar BMEP showed that lower BSNOx can be achieved with minimal drop in FCE. Varying intake manifold pressure revealed that combustion occurs earlier in a cycle with increasing intake manifold pressure and indirectly increasing FCE. A load of 10 bar BMEP at 70 PES should only use split-injection strategy to maintain load without high MPRR as efficiency drops with dependency on the second injection.

La dégradation de l’environnement ainsi que l’épuisement progressif des énergies fossiles devient très inquiétant et incite les états à définir des limites d’émission polluantes plus strictes. Ceci a conduit les constructeurs automobiles à poursuivre leurs recherches dans le développement de conception propre et efficace des moteurs en utilisant des combustibles alternatifs dans les moteurs à combustion interne.Dans le présent travail, on s’intéresse à l’étude des moteurs fonctionnant en mode DF afin d’améliorer ses performances tout en minimisant les émissions polluantes, en particulier les HC et les CO. Pour ce faire des études expérimentales ont été menées. Une réduction de 77% des émissions de HC a été observée en passant d’une richesse de 0,35 à 0,7. Par ailleurs, Il a été noté aussi qu’une diminution de 20% à 50% des émissions de CO avec une amélioration de 30% du rendement peut être visualisée en variant l’avance à l’injection de 4,5 °V à 6 °V. Concernant la mise en place de la pré-injection, une baisse de 30% des émissions de NOx a été observée avec un gain de 12% à 30% de rendement par rapport à une seule injection. En dernier terme, un modèle thermodynamique à une zone a été développé afin de prédire la température et la pression dans le cylindre. Une bonne concordance a été notée entre les deux résultats avec une erreur moyenne relative inférieure à 5%. / Currently, the environmental degradation due to pollutant emissions and the gradual depletion of fossil fuels, becoming very worrying, are prompting European directives to set pollutant emission limits. These have led manufacturers to continue research in the development of clean and efficient engine designs using alternative fuels in internal combustion engines.In this work, we focus on the study of engines operating in dual-fuel mode to improve its performance while minimizing pollutant emissions, particularly HC and CO. For this, experimental studies were conducted. A reduction of about 77% in the HC emissions was observed as the equivalence ratio was varied from 0.35 to 0.7. Regarding the effect of injection timing, it was noted that the CO emissions decreased about 20% to 50% with an improvement in the brake thermal efficiency by 30% upon varying the injection advance from 4,5 °CA to 6 °CA. On the other hand, the introduction of pre-injection strategy led to a decrease by 30% in NOx emissions with an amelioration of brake thermal efficiency of 12% to 30% compared to a single injection. Lastly, a single zone thermodynamic model was developed to predict the in-cylinder temperature and pressure. A good agreement was noted between the predicted and experimental results. The average relative error was less than 5%.