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Numerical optimisation of a waste-to-energy plant's operating parameters using CFD
Miran Kapitler, Niko Samec, Filip Kokalj, 2011, original scientific article

Abstract: The combustion process for using municipal solid waste as a fuel within a waste to energy plant calls for a detailed understanding of the following phenomena. Firstly, this process depends on many input parameters such as proximate and ultimate analyses, the season of the year, primary and secondary inlet air velocities and, secondly, on output parameters such as the temperatures or mass-flow rates of the combustible products. The variability and mutual dependence of these parameters can be difficult to manage in practice. Another problem is how these parameters can be tuned to achieving optimal combustible conditions with minimal pollutant emissions, during the plant-design phase. in order to meet these goals, a waste-to-energy plant with bed combustion was investigated by using computational fluid-dynamics approach. The adequate variable input boundary conditions based on the real measurement are used and the whole computational work is updated using real plant geometry and the appropriate turbulence, combustion, or heat transfer models. The operating parameters were optimized on output parameters through a trade-off study. The different operating conditions were varied and the combustible products were predicted and visualized. Finally, the response charts and matrix among the input and output parameters during the optimization process are presented, which monitored the dependence among these parameters.
Keywords: municipal solid waste, bed combustion, computational fluid dynamics, numerical optimization, goal driven optimization, trade-off study, parameters correlation
Published: 01.06.2012; Views: 1025; Downloads: 57
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Experimental investigation of optimal timing of the Diesel engine injection pump using biodiesel fuel
Breda 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: 31.05.2012; Views: 1295; Downloads: 49
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Numerical analysis of injection characteristics using biodiesel fuel
Breda 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: 31.05.2012; Views: 1147; Downloads: 59
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Experimental analysis of injection characteristics using biodiesel fuel
Breda 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: 31.05.2012; Views: 1010; Downloads: 40
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Intake system design procedure for engines with special requirements
Primož 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: 30.05.2012; Views: 1154; Downloads: 68
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Influence of biodiesel fuel on the combustion and emission formation in a direct injection (DI) Diesel engine
Aleš 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: 31.05.2012; Views: 1015; Downloads: 45
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Improvement of engine performance using an optimization procedure
Breda 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: 31.05.2012; Views: 962; Downloads: 44
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NOx and particulate matter (PM) emission reduction potential by biodiesel usage
Breda Kegl, 2007, original scientific article

Abstract: The transport in many countries is the most significant source for NOx and particulate matter (PM) emissions. Therefore, the possibility of reducing NOx and PM emissions is experimentally investigated using biodiesel and some of its blends with mineral diesel. Attention is focused on the optimal bus dieselengine adjustments for each tested fuel. The obtained engine characteristics are compared to each other by considering the 13 modes of the European stationary cycle test. The optimal injection pump timings are determined with the aim of reducing harmful emissions, while keeping other engine characteristics within acceptable limits. The optimal fuel blend is suggested, and the harmful emissions (NOx, PM, CO, unburned hydrocarbon, and smoke) reduction is estimated.
Keywords: internal combustion engine, NOx emissions, biodiesel fuel
Published: 31.05.2012; Views: 1053; Downloads: 27
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Combustion simulation in the secondary chamber of a pilot-scale incinerator
Niko Samec, Filip Kokalj, Jyh-Yan Chen, 2007, original scientific article

Abstract: A numerical analysis of combustion in the secondary chamber (thermoreactor) ofa two-stage pilot scale incinerator using computational fluid dynamics (CFD)is presented in detail. Various versions of the CFD program package CFX were used, which offer different combustion models for specific types and forms of combustion processes. The present study was focused on those physicalconditions that assure complete combustion, that is, temperature, residence time, and turbulent mixing. The selection of an appropriate combustion model was based on a comparison of the numerical results and experimental values of some combustion macro parameters in a thermoreactor. Combustion models based on one-step bimolecular chemical reaction and models based on multistep reactions were used. These models enabled a more detailed prediction of the combustion process in the secondary chamber of a pilot-scaleincinerator. The products of incomplete combustion that are significantly important for the designing and optimization of combustion devices can be predicted by applying multistep reaction models more accurately, especially in a transient regime of combustion.
Keywords: waste incineration, numerical modeling, combustion models, incinerator chamber, CFX, CFD, computational fluid dynamics
Published: 31.05.2012; Views: 1363; Downloads: 43
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Coupled simulations of nozzle flow, primary fuel jet breakup, and spray formation
Eberhard 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: 01.06.2012; Views: 860; Downloads: 49
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