1. Numerical and experimental study of water/oil emulsified fuel combustion in a diesel engineNiko Samec, Breda Kegl, Robert W. Dibble, 2002, original scientific article Abstract: Numerical and experimental studies were made on some of the chemical and physical properties of wateržoil emulsified fuel (W/OEF) combustion characteristics. Numerical investigations of W/OEF combustion's chemical kinetic aspects have been performed by simulation of water/n-heptane mixture combustion, assuming a model of a homogenous reactor's concentric shells. The injection and fuel spray characteristics are analyzed numerically also in order to study indirectly the physical effects of water present in diesel fuel during the combustion process. The experimental results of W/OEF combustion in the DI diesel engine are also presented and discussed. The results of engine testing in a broad field of engine loads and speeds have shown a significant pollutant emission reduction with no worsening of specific fuel consumption.
Keywords: internal combustion engines, Diesel engines, combustion, emissions, numerical modelling
Published in DKUM: 01.06.2012; Views: 2356; Downloads: 116
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4. Coupled simulations of nozzle flow, primary fuel jet breakup, and spray formationEberhard von Berg, Wilfried Edelbauer, Aleš Alajbegović, Reinhard Tatschl, Martin Volmajer, Breda Kegl, Lionel C. Ganippa, 2005, original scientific article Abstract: Presented are two approaches for coupled simulations of the injector flow withspray formation. In the first approach the two-fluid model is used within the injector for the cavitating flow. A primary breakup model is then applied at the nozzle orifice where it is coupled with the standard discrete droplet model. In the second approach the Eulerian multi-fluid model is applied for both the nozzle and spray regions. The developed primary breakup model, used in both approaches, is based on locally resolved properties of the cavitating nozzle flow across the orifice cross section. The model provides the initial droplet size and velocity distribution for the droplet parcels released from the surface of a coherent liquid core. The major feature of the predictions obtained with the model is a remarkable asymmetry of the spray. This asymmetryis in agreement with the recent observations at Chalmers University where they performed experiments using a transparent model scaled-up injector.The described model has been implemented into AVL FIRE computational fluid dynamics code which was used to obtain all the presented results.
Keywords: internal combustion engines, fuel injection, simulations
Published in DKUM: 01.06.2012; Views: 1779; Downloads: 95
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5. Improvement of engine performance using an optimization procedureBreda Kegl, Stanislav Pehan, Marko Kegl, 2007, original scientific article Abstract: This paper presents a simple and effective approach to improve engine performance of a racing car with special requirements. Attention is focused onoptimal design of the intake system, using a gradient-based approximation method of mathematical programming. Since optimization relies on accurate numerical analysis of engine processes, the sub-models and parameters needed in the analysis software are carefully determined by experiment. Subsequently,the influence of different design parameters of intake and exhaust systems on engine performance is investigated numerically. The most influencing parameters are selected to be the design variables in the optimization process. In order to improve engine power at several engine speeds, two different forms of the optimal design problem are proposed, solved, and compared as a means to identify the most appropriate one. Since the analysis software is a black-box program, the optimization procedure is implemented by employing the optimization software as a master (driver) program while the analysis software acts as the slave program. The data exchange between these programs is established by XML data files and suitable wrapper programs. The results obtained confirm the usefulness of the approach presented.
Keywords: internal combustion engines, exhaust system, intake system, optimization
Published in DKUM: 31.05.2012; Views: 2156; Downloads: 111
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6. Influence of biodiesel fuel on the combustion and emission formation in a direct injection (DI) Diesel engineAleš Hribernik, Breda Kegl, 2007, original scientific article Abstract: This paper studies the influence of biodiesel fuel on the combustion and emission formation of two different direct-injected diesel engines, both employing different combustion processes. The research was focused on determining the influence of the specific combustion process on measurement results to ascertain if a generalization of the results is possible or whetherthey have to be interpreted as specific for specific engines. Standard D2 diesel fuel and commercial 100% biodiesel fuel were used. Tests were executed using both fuels under the same conditions, and exhaust emissions andengine performance were measured and compared. In-cylinder pressure was also acquired, and the rate of heat release curves were computed by means of azero-dimensional, one-zone combustion model. Some macroparameters of the combustion process were obtained from the heat-release-rate curves. The results obtained for both engines showed that findings regarding the influenceof biodiesel fuel on the combustion process and emission formation could not be generalized and had to be interpreted as specific for the particular engine.
Keywords: internal combustion engines, diesel engines, biodiesel fuel, combustion, emissions
Published in DKUM: 31.05.2012; Views: 1798; Downloads: 147
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7. Experimental analysis of injection characteristics using biodiesel fuelBreda Kegl, Aleš Hribernik, 2006, original scientific article Abstract: This paper deals with injection characteristics using different fuels at different fuel temperatures. The fuels under consideration are neat biodiesel from rapeseed oil and some blends with diesel as well as neat mineral diesel D2. The fuel and fuel temperature influences are investigated experimentally in the mechanically controlled diesel fuel injection M system. At first, attention is focused on the injection characteristics, especially on fuelling, mean injection rate, mean injection pressure, injection timing, injection delay, and injection duration, which influence the most important engine characteristics. Furthermore, the influence of fuel temperature is investigated. On the basis of the measurements of pressure drop through the fuel filter, the minimum fuel temperature for safe engine operation is determined.
Keywords: internal combustion engines, fuel blends, biodiesel fuel, temperature influence, injection characteristics
Published in DKUM: 31.05.2012; Views: 1840; Downloads: 106
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8. Numerical analysis of injection characteristics using biodiesel fuelBreda Kegl, 2006, original scientific article Abstract: This paper deals with numerical analysis of injection process using biodieselžmineral diesel fuel blends with the aim to search for the potentialsto reduce engine harmful emissions. The considered fuels are neat biodiesel from rapeseed oil and its blends with mineral diesel D2. For the numerical analysis a one-dimensional mathematical model is employed. In order to model accurately the investigated fuels, the employed empirical expressionsfor their properties are determined by experiments. To verify the mathematical model and the empirical expressions, experiments and numerical simulation are run on a mechanical control diesel fuel injection M system at several operating regimes. Injection process at many different operating regimes and using several fuel blends are then investigated numerically. Attention is focused on the injection characteristics, especially on fuelling,fuelling at some stage of injection, mean injection rate, mean injection pressure, injection delay and injection timing, which influence the most important engine characteristics. The analysis of the obtained results reveals that, while keeping engine performance within acceptable limits, harmful emissions can be reduced by adjusting appropriately pump injection timing in dependence on the biodiesel content. This prediction is also confirmed experimentally.
Keywords: internal combustion engines, Diesel engines, fuel injection, biodiesel fuel, numerical simulation, emission reduction
Published in DKUM: 31.05.2012; Views: 2488; Downloads: 94
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9. Experimental investigation of optimal timing of the Diesel engine injection pump using biodiesel fuelBreda Kegl, 2006, original scientific article Abstract: This paper discusses the influence of biodiesel on output characteristics of adiesel engine and optimal timing setup for its injection pump. The influence of biodiesel is studied by running experiments on an NA diesel bus engine MAN D2 2566 with a direct-injection M system. The fuel used is biodiesel produced from rapeseed. Special attention is focused on the determination of the optimal injection-pump timing with respect to engine harmful emissions, enginefuel consumption, and other engine performance parameters. These engine characteristics are compared against those obtained using conventional D2 diesel. Experiments with biodiesel and D2 are run on several engine operating regimes. The engine was monitored for possible operation problems and carefully examined after the tests. The results obtained are presented and analyzed. It is shown that with carefully optimized timing of the pump, the harmful emission of NOx, smoke, HC, and CO can be reduced essentially by keeping other engine characteristics within acceptable limits.
Keywords: internal combustion engines, diesel engines, fuel injection, biodiesel fuel, engine characeristics
Published in DKUM: 31.05.2012; Views: 2898; Downloads: 183
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10. Intake system design procedure for engines with special requirementsPrimož Pogorevc, Breda Kegl, 2006, original scientific article Abstract: Intake manifolds provide fresh air to internal combustion engines and have a major effect on their performance. Therefore, many investigations are related to their design in order to improve the charging efficiency and to achieve theuniform distribution of fresh air among the engine cylinders. This paper deals with the design procedure of a cheap multipoint injection intake system,adapted to a racing car engine. Some special demands had to be taken into consideration. The intake manifold must contain the imposed constraint for the airflow in the shape of a single circular restrictor placed between the throttle and the engine to limit its power. The flow and the pressure lossreduction in the engine intake region were investigated with computationalfluid dynamics software. Two different geometries of the intake manifold were taken into consideration. On the basis of the numerically obtained three-dimensional results, a mathematical model of the engine with a more appropriate intake was made in the engine simulation code in order to anticipate its characteristics. The intake system was designed, practically manufactured, and tested in the laboratory. The experimental results confirmednumerical predictions, justifying the simple and relatively quick design procedure for the intake system.
Keywords: internal combustion engines, intake manifold, computational fluid dynamics, experiment
Published in DKUM: 30.05.2012; Views: 2624; Downloads: 111
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