Steady-State and Transient Operation Simulation of a “Downsized” Turbocharged SI Engine

Bozza, Fabio; Gimelli, Alfredo; Strazzullo, L.; Torella, E.; Cascone, C.

doi:10.4271/2007-01-0381

Cited by 33 publications

(20 citation statements)

References 10 publications

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“…Both steady state low speed torque and transient response are critical if any level of engine downsizing is going to be considered acceptable by the customer [16][17][18][19][20]. Currently single turbocharger systems are the predominant boosting system for downsized gasoline engines, with the VW twincharger the exception.…”

Section: Boosting Systemsmentioning

confidence: 99%

Challenges for Increased Efficiency through Gasoline Engine Downsizing

Fraser¹,

Blaxill²,

Lumsden³

et al. 2009

SAE Int. J. Engines

177

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In order to achieve the required future CO 2 reduction targets significant further development of both gasoline and diesel engines is required. One of the main methods to achieve this with the gasoline engine in the short to medium term is through the application of engine downsizing, which has resulted in numerous downsized engines already being brought to production. It is, however, considered that there is still significant further CO 2 reduction potential through continued development of this technology. This paper considers the future development of gasoline engine downsizing in the short to medium term and the various technologies that can be applied to further increase the efficiency of operation. As such this paper covers, among other areas, fundamental engine layout and design, alternative boosting systems, methods of increasing part load efficiency and vehicle modelling, and uses analysis tools and engine test results to show the benefits achievable.

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Section: Boosting Systemsmentioning

confidence: 99%

Challenges for Increased Efficiency through Gasoline Engine Downsizing

Fraser¹,

Blaxill²,

Lumsden³

et al. 2009

SAE Int. J. Engines

177

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“…This is usually realized through the employment of 1D codes [10], which can also provide the boundary conditions for more refined 3D CFD analyses [11]. These procedures require the specification of the turbine and compressor characteristic maps, provided by the manufacturer.…”

Section: Introductionmentioning

confidence: 99%

Unsteady 1D Simulation of a Turbocharger Compressor

Bozza¹,

Gimelli²

2009

SAE Int. J. Engines

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The one-dimensional (1D) modeling of a turbocharged engine requires the availability of the turbine and compressor characteristic maps. This leads to two main problems: • performance maps of the turbocharger device are usually limited to a reduced number of rotational speeds, pressure ratios and mass flow rates. Extrapolation of maps’ data is commonly required; • performance maps are experimentally derived on stationary test benches, while the turbocharger usually operates under unsteady conditions, when coupled to an internal combustion engine (ICE). To overcome the above problems, in the present paper the flow inside a rotating pipe of a centrifugal compressor is simulated within a 1D modeling approach, with the aim of predicting its characteristic map. The main improvement with respect to the employment of a steady experimental map consists in the absence of data extrapolation and in the possibility of fully characterizing the unsteady operation of the component. In this way it is also possible to handle on a physical point of view surge phenomena (backflows) which may arise particularly at low engine speed and high load. To this aim, the actual evolution of the blade-to-blade duct profile is specified through the assignment of proper data which define the duct orientation in the space along its curvilinear abscissa. Flow equations are next generalized to include additional terms arising as a consequence of pipe rotation. The whole compressor is schematized as a number of rotating channels in parallel, linked at the impeller inlet and outlet by a constant pressure boundary condition. The velocity triangles are employed to handle the transition between the absolute and the relative motion occurring at the impeller inlet and outlet. The presence of a vaneless diffuser is also considered at the exit section of the rotor blades. The procedure includes some correlations to keep into account slip effects, incidence and distributed losses. The above methodology is utilized to directly compute the stationary map of the device, starting from the specification of its geometry and rotating speed. A comparison with experimental data shows a good agreement with the predicted performance curves. The same procedure can be easily extended to the simulation of a radial turbine, too. A one-dimensional model of a centrifugal compressor was described in detail under both isentropic and real flow conditions. Classical correlations for the various flow losses and slip effects were introduced in the model, and their effect on the computed results was discussed with reference to a test compressor. The model was then applied to the simulation of a backswept vanes compressor constituting the turbocharger of a small displacement SI engine. The numerical procedure, after a limited adjustment of few tuning constants, was proven to furnish the steady performance map of the device all over its operating region. Both the pressure ratio and the outlet temperature showed a very good agreement with the test data. The stable operating limit o...

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“…For total flow in the combustion chamber, the kinetic energy associated with the average movement is [32,33]: (12) In the above equation, m is the total mass in the cylinder and K cyl production terms are mainly related to the kinetic energy of intake, exhaust flows and swirl. In Equation (12), swirl term is defined as: Diagram of the energy balance in the combustion chamber.…”

Section: Two States Turbulence Model: Modified K-k Modelmentioning

confidence: 99%

“…The assumption for the energy balance equation in the spray volume is that swirl does not induce mass transfer between the surrounding air and the spray volume, but only dissipates energy. By writing the energy conservation equations, the rate of kinetic energy of average and turbulent movement in the spray are [32,33]:…”

Section: Two States Turbulence Model: Modified K-k Modelmentioning

confidence: 99%

A Physics and Tabulated Chemistry Based Compression Ignition Combustion Model: from Chemistry Limited to Mixing Limited Combustion Modes

Bordet

Caillol

Higelin

et al. 2011

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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Résumé -Un modèle de combustion à allumage par compression basé sur la physique et la chimie tabulée : des modes de combustion contrôlés par la chimie jusqu'aux modes contrôlés par le mélange -Ce papier présente une nouvelle approche 0D phénoménologique pour prédire le déroulement de la combustion dans les moteurs Diesel à injection directe pour toutes les conditions d'utilisation usuelles. Le but de ce travail est de développer une approche physique en vue d'améliorer la prédiction de la pression cylindre et du dégagement d'énergie, avec un nombre minimum d'essais nécessaires à la calibration. Les contributions principales de cette étude sont la modélisation de la phase de pré-mélange de la combustion et une extension du modèle pour les stratégies d'injections multiples. Dans ce modèle, le taux de dégagement d'énergie dû à la combustion pour la phase pré-mélangée est relié à un taux de réaction moyen du carburant. Ce taux de réaction moyen de carburant est évalué à l'aide d'une approche basée sur un taux de réaction local de carburant tabulé et la détermination d'une fonction de densité de probabilité (PDF) de la fraction de mélange (Z). Cette PDF permet de prendre en compte la distribution de richesse existante dans la zone pré-mélangée. L'allure de cette PDF présumée est une β-fonction standardisée. Les fluctuations de la fraction de mélange sont décrites avec une équation de transport pour la variance de Z. La définition standard de la fraction de mélange, établie dans le cas de flammes de diffusion, est ici adaptée à une combustion pré-mélangée de type Diesel pour décrire l'inhomogénéité de la richesse dans le volume de contrôle. La chimie détaillée est décrite au travers de la tabulation du taux de réaction relatif à la flamme principale et du délai d'auto-inflammation relatif à la flamme froide, ces tabulations sont fonction de la variable d'avancement c, du taux de gaz brûlé ainsi que des grandeurs thermodynamiques telles que la température et la pression. Le modèle de combustion de diffusion est basé sur l'évaluation d'une fréquence de mélange qui est fonction du taux de turbulence dans la chambre et fonction de la masse de carburant vapeur disponible. Ce modèle de combustion est l'un des sous-modèles inclus dans le modèle thermodynamique de chambre de combustion basé sur une approche 2 zones différentiant gaz frais et gaz brûlés. De plus, un sous-modèle concernant la multi-injection a été développé pour prendre en compte les interactions entre les jets et pour décrire l'impact de la multi-injection sur le mélange air/carburant. Les résultats numériques ont été comparés aux mesures réalisées sur un moteur Diesel Renault de 2 litres. Pour l'ensemble des points de fonctionnement explorés, une bonne correspondance a été obtenue entre les résultats issus des simulations et les mesures expérimentales. Oil & Gas Science and Technology -Rev. IFP Energies nouvelles, Vol. 66 (2011) and Technology -Rev. IFP Energies nouvelles, Vol. 66 (2011) , No. 5, pp. 823-843 Copyright © 2011, IFP Energies nouvelles DOI: 10.25...

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Steady-State and Transient Operation Simulation of a “Downsized” Turbocharged SI Engine

Cited by 33 publications

References 10 publications

Challenges for Increased Efficiency through Gasoline Engine Downsizing

Challenges for Increased Efficiency through Gasoline Engine Downsizing

Unsteady 1D Simulation of a Turbocharger Compressor

A Physics and Tabulated Chemistry Based Compression Ignition Combustion Model: from Chemistry Limited to Mixing Limited Combustion Modes

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