Zugl.: München, Univ., Diss., 2007

Zugl.: München, University, Diss., 2007. / Zugl.: München, Univ., Diss., 2007. - Mit dt. Zusammenfassung.

Jena, Univ., Diss., 2009.

No description available.

Chemnitz, Techn. Univ., Diplomarb., 2007.

Due to their ability to simultaneously reduce fuel consumption and NOx emissions, Controlled Auto Ignition (CAI) and HCCI combustion processes have been extensively researched over the last decade and adopted on prototype gasoline engines. These combustion processes were initially achieved on conventional two-stroke ported gasoline engines, but there have been significantly fewer studies carried out on the CAI combustion in two-stroke engines. This is primarily due to the inherent problems associated with conventional two-stroke engine intake and exhaust ports. Meanwhile, engine downsizing has been actively researched and developed as an effective means to improve the vehicle’s fuel economy. This is achieved by operating the engine at higher load regions of lower fuel consumption and by reducing the number of cylinders. However, aggressive downsizing of the current 4-stroke gasoline engine is limited by the knocking combustion and high peak cylinder pressure. As an alternative approach to engine downsizing, boosted two-stroke operation is being researched. In this thesis, it has been shown that the CAI combustion in the two-stroke cycle could be readily achieved at part-load conditions with significant reductions in CO and uHC emissions when compared to typical SI combustion in a single cylinder gasoline direct injection camless engine. In addition, extensive engine experiments have been performed to determine the optimum boosting for minimum fuel consumption during the two-stroke operation. In order to minimise the air short-circuiting rate, the intake and exhaust valve timings were varied and optimised. It is shown that the lean operation under boosted condition can extend the range of CAI combustion and increase combustion and thermal efficiencies as well as producing much lower CO and HC emissions. By means of the cycle-resolved in-cylinder measurements and heat release analysis, the improvement in combustion and thermal efficiencies were attributed to the improved in-cylinder mixture, optimised autoignition, and combustion phases. Finally, in view of the increased use of ethanol in gasoline engines, E15 and E85 were used and their effect on engine performance, fuel economy and exhaust emissions were investigated.

<p>This licentiate thesis deals mainly with modelling ofturbocharged SIengines. A model of a 4-cylinder engine was runin both steady state and transient conditions and the resultswere compared to measured data. Large differences betweenmeasurements and simulations were detected and the reasons forthis discrepancy were investigated. The investigation showedthat it was the turbocharger turbine model that performed in anon-optimal way. To cope with this, the turbine model containedparameters, which could be adjusted so that the model resultsmatched measured data. However, it was absolutely necessary tohave measured data to match against. It was thus concluded thatthe predictivity of the software tool was too poor to try topredict the performance of various boosting systems. Thereforemeans of improving the modelling procedure were investigated.To enable such an investigation a technique was developed tomeasure the instantaneous power output from, and efficiency of,the turbine when the turbocharger was used on the engine.</p><p>The project’s initial aim was to predict, throughsimulations, the best way to boost a downsized SI-engine with avery high boost-pressure demand. The first simulation run on astandard turbocharged engine showed that this could not be donewith any high accuracy. However, a literature study was madethat presents various different boosting techniques that canproduce higher boost pressure in a larger flow-range than asingle turbocharger, and in addition, with smallerboost-pressure lag.</p><p><b>Key words:</b>boosting, turbocharging, supercharging,modelling, simulation, turbine, pulsating flow, unsteadyperformance, SI-engine, measurement accuracy</p>

Die Diplomarbeit beschäftigt sich mit der Detektion von Gesichtern in Bildern. Ausgehend von einem Überblick über bestehende Verfahren wird ein viel versprechendes Verfahren ausgewählt, vorgestellt und basierend auf neuen Erkenntnissen weiterentwickelt. Bilddaten aus dem Universitätsarchiv werden exemplarisch für die Evaluierung des Verfahrens verwendet.

This licentiate thesis deals mainly with modelling ofturbocharged SIengines. A model of a 4-cylinder engine was runin both steady state and transient conditions and the resultswere compared to measured data. Large differences betweenmeasurements and simulations were detected and the reasons forthis discrepancy were investigated. The investigation showedthat it was the turbocharger turbine model that performed in anon-optimal way. To cope with this, the turbine model containedparameters, which could be adjusted so that the model resultsmatched measured data. However, it was absolutely necessary tohave measured data to match against. It was thus concluded thatthe predictivity of the software tool was too poor to try topredict the performance of various boosting systems. Thereforemeans of improving the modelling procedure were investigated.To enable such an investigation a technique was developed tomeasure the instantaneous power output from, and efficiency of,the turbine when the turbocharger was used on the engine. The project’s initial aim was to predict, throughsimulations, the best way to boost a downsized SI-engine with avery high boost-pressure demand. The first simulation run on astandard turbocharged engine showed that this could not be donewith any high accuracy. However, a literature study was madethat presents various different boosting techniques that canproduce higher boost pressure in a larger flow-range than asingle turbocharger, and in addition, with smallerboost-pressure lag. <b>Key words:</b>boosting, turbocharging, supercharging,modelling, simulation, turbine, pulsating flow, unsteadyperformance, SI-engine, measurement accuracy / NR 20140805

This thesis studies competence of simplified simulation methods for boosting simulation.  The most efficient propulsion unit has higher amount of power compared to less efficient propulsion units in boosting. Boosting is relevant subject to study due to new concept. New concept allows a larger diameter for the propeller which increases the efficiency of the propeller. New concept relies on the idea to have the propeller behind the hull.   The thesis is restricted to study displacement hulls from a point of view of propulsion efficiency. Large cruise ship model is utilized in this thesis to identify boosting related effects efficiently. Model tests reports of this concept are used as a baseline and a comparison material for two methods that are tested in this thesis. These methods are Matlab simulation code and OpenFOAM as the CFD software.   New propulsion arrangement concept is more efficient than current solutions for this hull type according to model tests. Trend of the CFD and Matlab simulation results matches well with model test results for boosting. Matlab simulation is evidently more time efficient solution than CFD simulation for boosting. Simplified CFD simulation is sufficiently accurate to study boosting concept with this research setup. Matlab and CFD simulations can be combined to obtain the most efficient solution to analyze the most effective load division for boosting.   Different types of hulls should be simulated and results should be verificated with model or full scale tests. In addition, ships with old two shaft arrangements could be converted to have two smaller pods and center line propeller in order to have better comparison with current methods. Scaling factors increases the uncertainty for new concepts; therefore full scale measurements are required. / Denna masteruppsats studerar möjligheterna med förenklade simuleringsmetoder i relation till nya framdrivningskoncept. Studerat koncept ger möjlighet till en större diameter för en boosterpropeller i centerlinjen, vilket ökar propellerns effektivitet. Konceptet bygger på tanken att få propellern bakom skrovet. Masteruppsatsen är begränsad till att studera deplacerande skrov i relation till framdrivningseffektiviteten. Studien appliceras på stora kryssningsfartyg. Resultat från modellförsök används som en referens och ett jämförelsematerial för de två beräkningsmetoder som testas i denna masteruppsats. Dessa metoder är Matlab-simuleringskod och OpenFOAM som CFD-programvara. Arbetet visar att det nya framdrivningskonceptet är effektivare än nuvarande lösningar för denna skrovtyp. Resultaten från CFD och simuleringsresultat från Matlab matchar väl med modellprovresultat. Matlab-simulering är en mer tidseffektiv lösning än CFD-simulering. Förenklad CFD-simulering är tillräckligt exakt för att studera boosterkoncept. Matlab- och CFD-simuleringar kan kombineras för att få den mest effektiva lösningen och för att analysera den mest effektiva belastningsfördelningen mellan propulsorer. Olika typer av skrov bör undersökas och resultaten ska verifieras med modell- eller fullskaletester. Skaleffekter ökar osäkerheten, därför krävs fullskalemätningar