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We present an extensive experimental study focused on understanding the impact of cavitation in a high-pressure diesel nozzle on the macroscopic properties of fuel spray. Several high-speed videos of the liquid flow through a transparent, asymmetric cylindrical nozzle with a single orifice (phi = 0.35 mm) are recorded along with the videos of the resulting spray in the near-nozzle region, issued with an injection pressure of 300 bar at a frame-rate of 75 kHz. The high-repetition images of the internal flow are then used to estimate the onset of cavitation inside the transparent nozzle and the probability of development of cavitation in different regions of the nozzle with an average estimate of the amount of cavitation with time. On the other hand, recorded spray images are used to study spray penetration, cone-angles and velocity from the start of fuel injection. A novel approach is proposed for the measurement of perturbations that occur in form of big liquid structures along the spray boundary., in 27th European Conference on Liquid Atomization and Spray Systems, Sep 2016, Brighton, United Kingdom. 2016

National audience; La complexité des moteurs diesel modernes contrôlés par l'électronique, avec un nombre croissant de capteurs et d'actionneurs, nécessite des systèmes de mesure et de diagnostic améliorés et automatisés à bord des véhicules utilisant ces moteurs. La surveillance appropriée et la détection précoce des défauts nécessite de disposer de modèles de bon fonctionnement des composants et, dans cette communication, on s'intéresse à la boucle des gaz d'un moteur diesel à injection directe. On établit des modèles des composants de cette boucle, on identifie leurs paramètres et on procède à la validation du modèle complet de la boucle. Les essais effectués sur un moteur réel montrent une bonne adéquation entre les grandeurs élaborées par ce modèle et les informations correspondantes fournies par les capteurs.

International audience; Le système d'injection à rampe commune a été développé pour obtenir, sur un moteur diesel, une augmentation des performances ainsi qu'une réduction du bruit, des émissions polluantes et de la consommation de carburant. De tels objectifs ne sont obtenus que lorsque l'ensemble du système est parfaitement contrôlé. Or, la moindre défaillance dans celui-ci peut engendrer une dégradation significative des performances du moteur ainsi qu'une augmentation de ses émissions polluantes. Un système de diagnostic basé sur les tests d'hypothèses structurés est ici proposé afin de détecter et d'isoler différents défauts susceptibles d'intervenir au niveau du contrôle de la pression d'un système d'injection diesel à rampe commune.

International audience; Common rail injection system has been developed to increase diesel engine performances and to reduce noise, emission and fuel consumption. Such goals are possible only if the whole system is perfectly controlled. But, any system component failure can lead to significant engine performances decrease and degraded emission control. A fault diagnosis system based on structured hypothesis tests is proposed in this paper, in order to detect and isolate different types of failures which are able to affect the pressure control loop in a common rail diesel injection system.

[EN] Cavitation inception is very sensitive to the nozzle geometry. Two diesel-like transparent nozzles with sharp and round inlet edge were investigated under moderate injection pressure. By means of backlight imaging technique, images were recorded in two regions near the orifice: within ten orifice diameter downstream the nozzle and inside the nozzle, for different times after start of the injection. A cross-correlation technique was applied to images downstream the orifice to estimate the average velocity of the spray. The development of the spray was studied at the transient and full-opened stage, related to the needle lift motion. To analyse the flow inside the nozzle, the relative size of the vapour pockets was measured on the image and the relative frequency of the occurrence of cavitation was determined over image series. This approach permits to examine the time variation of the cavitation occurrence from the inlet to the outlet of the orifice. The results highlight the sensitivity of the cavitating flow to the shape of the inlet edge. Moreover, the trends of the variation over time of the velocity and of the cavitation frequency are very similar to each other but different for each geometry, indicating that the characteristics of the diesel spray in the near field is closely affected by the way cavitation is developing in the nozzle., This work was supported by CANNEx program (ANR-13-TDMO-03), funded from French National Research Agency (ANR).