Spray Atomization Models in Engine Applications, from Correlations to Direct Numerical Simulations

Sprays are among the very main factors of mixture formation and combustion quality in almost every (IC) engine. They are of great importance in pollutant formation and energy efficiency although adequate modeling is still on development. For many applications, validation and calibration of models are still an open question. Therefore, we present an overview of existing models and propose some trends of improvement. Models are classified in zero dimensional and dimensional classes ranging from simple formulations aimed at close-to-real-time applications to complete detailed description of early atomization stages

Fonctionnement transitoire et controle de la richesse des moteurs à allumage commandé à injection multipoint Transient Operation and Air-Fuel Ratio Control of Spark-Ignition Port-Injected Engines

Sur les moteurs à allumage commandé à injection multipoint on observe des désadaptations de richesse lors de fonctionnement transitoire. Ces désadaptations sont dues au dépôt, sous forme de film liquide, du carburant injecté dans le collecteur. Elles peuvent être compensées par une gestion adéquate de la masse injectée. Ainsi, afin d'obtenir la masse de carburant qui maintient la richesse constante, nous avons développé un modèle bidimensionnel des écoulements dans le collecteur au cours du cycle moteur. Ce modèle décrit l'écoulement des gaz frais, des gouttes injectées, des gaz brûlés refoulés vers l'admission et du film sur les parois, sur le principe de la séparation des phases. Nous montrons que le modèle reproduit correctement le signal de richesse et comment il permet de supprimer les désadaptations. La mesure de richesse est faite à l'échappement avec une sonde à oxygène dont nous validons le fonctionnement en transitoire avec une corrélation à la pression maximale du cycle dans le cylindre. <br> Air-fuel ratio excursions are observed on port-injected spark ignition engines during transients. This excursions result from the liquid fuel film deposited on intake port. They can be compensated by controlling the injected fuel mass. In order to have the amount of fuel that keeps air-fuel ratio constant, we have developed a 2D model of flows in the intake port during engine cycle. This separate phases model describes the flow of fresh gases, injected droplets, hot burned gases and film on port walls. We show that the model effectively predicts the equivalence ratio and how it allows to eliminate excursions. Equivalence ratio measures are made with an oxygen sensor which functioning is validated during transients by correlating it to maximal pressure during engine cycle

Fonctionnement transitoire et controle de la richesse des moteurs à allumage commandé à injection multipoint

International audienceSur les moteurs à allumage commandé à injection multipoint on observe des désadaptations de richesse lors de fonctionnement transitoire. Ces désadaptations sont dues au dépôt, sous forme de film liquide, du carburant injecté dans le collecteur. Elles peuvent être compensées par une gestion adéquate de la masse injectée. Ainsi, afin d'obtenir la masse de carburant qui maintient la richesse constante, nous avons développé un modèle bidimensionnel des écoulements dans le collecteur au cours du cycle moteur. Ce modèle décrit l'écoulement des gaz frais, des gouttes injectées, des gaz brûlés refoulés vers l'admission et du film sur les parois, sur le principe de la séparation des phases. Nous montrons que le modèle reproduit correctement le signal de richesse et comment il permet de supprimer les désadaptations. La mesure de richesse est faite à l'échappement avec une sonde à oxygène dont nous validons le fonctionnement en transitoire avec une corrélation à la pression maximale du cycle dans le cylindre

Model and Measure of Flows at the Intake of Engines

A simple physical model is developed to simulate the annular dispersed multiphase flow observed at the intake of spark ignition port-injected engines. The model is a separate phase 2D model taking into account gas, droplets and liquid film phases. It is validated by the results of different measurements made on engine. Temperature, pressure and velocity measurements are made in the intake manifold of a production engine in order to characterize the flows of gaseous phases. Velocity measurements are also made for injected fuel droplets. Global equivalence ratio measurements are made to validate modeling of deposited fuel film on manifold walls

Development and validation of a 5 stroke engine for range extenders application

International audienc

3D electro-thermal modelling and experimental validation of lithium polymer-based batteries for automotive applications

Summary This article presents an electro-thermal model of a stack of three lithium ion batteries for automotive applications. This tool can help to predict thermal behaviour of battery cells inside a stack. The open source software OpenFOAM provides the possibility to add heat generation because of Joule losses in a CFD model. Heat sources are introduced at the connectors and are calculated as a function of battery discharge current and internal resistance. The internal resistance is described in function of temperature. Simulation results are validated against experimental results with regard to cooling air flow field characteristic and thermal behaviour of the cell surface. The validation shows that the simulation is capable to anticipate air flow field characteristics inside the battery box. It also predicts correctly the thermal behaviour of the battery cells for various discharge rates and different cooling system conditions. The simulation supports the observation that batteries have a higher temperature close to the connectors and that the temperature increase depends highly on discharge rate and cooling system conditions

Simulation of primary atomization with an octree adaptive mesh refinement and VOF method

International audienceWe present different simulations of primary atomization using an adaptive Volumeof-Fluid method based on octree meshes. The use of accurate numerical schemesfor mesh adaptation, Volume-of-Fluid advection and balanced force surface tensioncalculation implemented in Gerris, the code used to perform the simulationsincluded in this work, has made possible to carry out accurate simulations withcharacteristic scales spreading over several orders of magnitude. The code isvalidated by comparisons with the temporal linear theory for moderate densityand viscosity ratios, which basically corresponds to atomization processes inhigh pressure chambers. In order to show the potential of the code in differentscenarios related to atomization, preliminary results are shown in relation withthe study of the two-dimensional and 3D temporal and spatial problem, theinfluence of the injector and the vortex generated inside the chamber, and theeffect of swirling at high Reynolds numbers