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Numerical investigation of the spray characteristics during pilot injection of a dual fuel injector

Frühhaber J, Peter A, Schuh S, Lauer T, Wensing M, Winter F, Priesching P, Pachler K (2018)

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Publication Language: English

Publication Type: Conference contribution, Conference Contribution

Publication year: 2018

Event location: Glasgow

Abstract

Due to the introduction of the so called Emission Controlled Areas within the IMO Tier III legislation, dual fuel combustion will become more important in the field of maritime propulsion. To meet the stringent emission targets ships propelled with HFO may switch to dual fuel operation mode in the protected areas. The combustion process is characterised by the injection of a small amount of fuel oil which ignites a lean natural gas air mixture. The resulting short injection durations, oblige the injector into the ballistic working regime. This influences spray penetration, mixture formation and ignition behaviour.

In the present work a CFD model of a dual fuel injector was developed using the commercial code AVL FIRE. Due to the ballistic working regime the main challenge for the modelling is to capture the opening and closing behaviour of the injector. Therefor optical investigations were carried out in an injection bomb to characterize the liquid and the vapor phase at an early stage of spray propagation. Based on the experimental observations a methodology assuming constant momentum along the spray axis was applied to estimate the initial velocity of the droplets. Further on the measured injection rate shape is adjusted for different fuel amounts to predict the spray characteristics for different substitution rates. To realise the observed dependencies of the spray penetration from chamber conditions and to depict the decrease of liquid length after the end of injection, a suitable initial droplet spectrum was defined. The developed model is able to predict the experimental observed penetration and contour of the spray plume really well.

In a further step the model was extended by a detailed reaction mechanism to simulate the combustion process of the diesel jet. The ignition delay was validated using measurements of the OH* emission of the flame. Further on the recorded OH* intensity enables a detailed characterisation of the development and the propagation of the first flame structures. The distribution of the simulated OH concentration shows a good

correlation with the experimental data concerning the contour und the penetration behaviour of the flame.

The developed knowledge will be transferred to a CFD model of a single cylinder research engine to investigate the dual fuel combustion process, especially in the limiting areas of knocking and flame quenching.

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How to cite

APA:

Frühhaber, J., Peter, A., Schuh, S., Lauer, T., Wensing, M., Winter, F.,... Pachler, K. (2018). Numerical investigation of the spray characteristics during pilot injection of a dual fuel injector. In Proceedings of the 7th European Conference on Computation Fluid Dynamics (ECFD). Glasgow, GB.

MLA:

Frühhaber, Jens, et al. "Numerical investigation of the spray characteristics during pilot injection of a dual fuel injector." Proceedings of the 7th European Conference on Computation Fluid Dynamics (ECFD), Glasgow 2018.

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