Improved δ-SPH Scheme With Automatic and Adaptive Numerical Dissipation

[Abstract] In this work we present a δ-Smoothed Particle Hydrodynamics (SPH) scheme for weakly compressible flows with automatic adaptive numerical dissipation. The resulting scheme is a meshless self-adaptive method, in which the introduced artificial dissipation is designed to increase the dissipation in zones where the flow is under-resolved by the numerical scheme, and to decrease it where dissipation is not required. The accuracy and robustness of the proposed methodology is tested by solving several numerical examples. Using the proposed scheme, we are able to recover the theoretical decay of kinetic energy, even where the flow is under-resolved in very coarse particle discretizations. Moreover, compared with the original δ-SPH scheme, the proposed method reduces the number of problem-dependent parameters.This research was funded by the Ministerio de Ciencia, Innovación y Universidades of the Spanish Government, grant number #RTI2018-093366-B-I00, by the Consellería de Educación e Ordenación Universitaria of the Xunta de Galicia (grant number #ED431C 2018/41). Xesús Nogueira has also been funded by the Xunta de Galicia through the program Axudas para a mellora, creación, recoñecemento e estruturación de agrupacións estratéxicas do Sistema Universitario de Galicia (grant number # ED431E 2018/11)Xunta de Galicia; ED431C 2018/41Xunta de Galicia; ED431E 2018/1

Caractérisation numérique et expérimentale des performances d'un turbocompresseur automobile aux bas régimes de rotation

Très courante sur les moteurs diesel, la suralimentation des moteurs automobiles s étend moteurs à allumage commandé. La zone de fonctionnement à bas régime du turbocompresseur est mal connue bien qu elle représente l utilisation urbaine d'un véhicule. Afin de progresser sur la connaissance des performances des turbocompresseurs aux bas régimes de rotation, un banc d'essai original de turbocompresseurs a été mis au point. Equipé d un couplemètre et d un système magnétique de contrôle de l effort axial, il permet de tracer le champ compresseur à bas régime et de mesurer les pertes par frottements en conditions adiabatiques. Les mesures réalisées ont permis de mettre en évidence l influence de la vitesse de rotation, de la température et de la pression d alimentation d huile et de l effort axial sur la butée. Les paliers lisses et la butée hydrodynamiques ont également été modélisés. Après avoir montré l impossibilité d utiliser des méthodes simples et isotherme, l équation de Reynolds est résolue simultanément avec l équation de l énergie sur des géométries très simplifiées de palier et de butée. Une modélisation similaire est également réalisée avec le logiciel Fluent. Cette modélisation est améliorée pour le palier pour prendre en compte la complexité de la géométrie comprenant la gorge d alimentation, les quatre orifices, la convection dans les films d huile intérieur et extrérieur et la conduction dans le coussinet. Enfin une comparaison des résultats est effectuée. Les différentes méthodes de mesures donnent des résultats comparables et qui corrèlent avec les résultats de calculs.PARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Surge detection on an automotive turbocharger during transient phases

International audienceThe surge limit on automotive turbocharger needs to be avoided to prevent operations with pressure and mass flow oscillations. Mild surge is accompanied by noise which is disturbing. Deep surge can cause significant loss of engine power and severe drivability issues. It is necessary to know the stationary limit in order to match a turbocharger with an engine, ensuring enough surge margin. However, this choice does not guarantee surge free operation during transient functioning. In this paper, the surge onset of a compressor while closing a downstream valve is studied. Various tests have been carried out varying the closing time, the position of the initial operating point and the volume of the circuit. The inlet and outlet signals of physical parameters are analyzed with spectral and temporal methods in order to define the instant of the surge occurrenc

Surge detection on an automotive turbocharger during transient phases

International audienceThe surge limit on automotive turbocharger needs to be avoided to prevent operations with pressure and mass flow oscillations. Mild surge is accompanied by noise which is disturbing. Deep surge can cause significant loss of engine power and severe drivability issues. It is necessary to know the stationary limit in order to match a turbocharger with an engine, ensuring enough surge margin. However, this choice does not guarantee surge free operation during transient functioning. In this paper, the surge onset of a compressor while closing a downstream valve is studied. Various tests have been carried out varying the closing time, the position of the initial operating point and the volume of the circuit. The inlet and outlet signals of physical parameters are analyzed with spectral and temporal methods in order to define the instant of the surge occurrenc

Automotive compressor: effect of an electric throttle in the upstream circuit on the surge limit

On vehicles equipped with a turbocharged engine, there is a risk of compressor surge. This surge generates instabilities that lead to driving inconvenience, or even mechanical failure of the supercharging system. In general, the surge appears rather in transient operation: sudden closing of the throttle valve on gasoline engine, regulation of the EGR on diesel engine linked also to turbine regulation (VNT device or Waste Gate). On a turbocharger test stand, we set up the surge line in a “conventional way”: stationary experiments. Then we set up this line in transient conditions for different positions of an electric throttle placed upstream the compressor. It appears that: the surge limit is pushing back to lower flow rates when it is determined in transient; the surge limit is pushing back to lower flow rates when closing the throttle valve. The tests were carried on by the transient analysis of the surge during a quick closing-opening of the electric throttle valve