Real-fluid simulation of ammonia cavitation in a heavy-duty fuel injector

TL;DR

This study uses advanced real-fluid simulations to analyze ammonia cavitation in a heavy-duty fuel injector, revealing vapor pocket formation primarily of ammonia vapor, which differs from hydrocarbon fuel behavior.

Contribution

It introduces a novel multi-component real-fluid model for simulating ammonia cavitation, considering effects of non-condensable gases, and provides new insights into phase change phenomena in ammonia fuel injectors.

Findings

Cavitation pockets are mainly ammonia vapor due to high vapor pressure.

The model effectively captures phase transition phenomena.

Dissolved nitrogen has minimal impact on cavitation pockets.

Abstract

The reduction of greenhouse gases (GHG) emitted into the earth's atmosphere, such as carbon dioxide, has obviously become a priority. Replacing fossil fuels with cleaner renewable fuels (such as ammonia) in internal combustion engines for heavy-duty vehicles is one promising solution to reduce GHG emissions. This paper aims to study the cavitation formation in a heavy-duty injector using ammonia as fuel. The simulation is carried out using a fully compressible two-phase multi-component real-fluid model (RFM) developed in the CONVERGE CFD solver. In the RFM model, the thermodynamic and transport properties are stored in a table which is used during the run-time. The thermodynamic table is generated using the in-house Carnot thermodynamic library based on vapor-liquid equilibrium calculations coupled with a real-fluid equation of state. The RFM model allows to consider the effects of the dissolved non-condensable gas such as nitrogen on the phase change process. The obtained numerical results have confirmed that the model can tackle the phase transition phenomenon under the considered conditions. In contrast to previous numerical studies of the cavitation phenomenon using hydrocarbon fuels, the formed cavitation pockets were found to be primarily composed of ammonia vapor due to its high vapor pressure, with minimal contribution of the dissolved non-condensable nitrogen.