“Abstract

A Computational Fluid Dynamics (CFD) model is developed and validated against experimental data to predict the critical diameter and stability limits of non-premixed turbulent methane flames. The critical diameter defines the orifice size beyond which a stable flame persists at all driving pressures and below this pressure stability is pressure-dependent. Flame stability follows a “peninsula” curve of pressure versus release diameter, with sustained flames above the upper and below the lower pressure limits, while the intermediate region represents a blow-out zone where combustion is not sustained. The critical diameter, at the curve’s rightmost point, is crucial for predicting sustained flames. Methane releases have been simulated for conditions in the region of the critical diameter, and for diameters and pressures ranging from 15 to 45 mm and 0.01 to 20 MPa, respectively, corresponding to the upper and lower flame stability limits using the realizable k − ε model and EDC combustion model. The simulations accurately captured blow-out and sustained flames, yielding a critical diameter of 42 mm, consistent with experiments. A methane flame at 5.88 MPa gauge through a 50 mm orifice was also simulated, showing flame length and lift-off distance in agreement with experimental observations. These results confirm the model’s reliability in predicting methane flame stability, providing valuable insights for safety and combustion applications. This study presents the first CFD-based reproduction of the full methane flame stability curve, validating model reliability across a wide pressure range and providing a predictive tool for future applications, including the assessment of flame stability in methane‑hydrogen mixtures.”

 

The full report is accessible via: https://doi.org/10.1016/j.fuproc.2025.108249

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

This study aims to develop and validate a CFD model for large eddy simulations of gaseous ammonia released from the ullage space of a storage tank through the piping system to the atmosphere under realistic wind conditions measured experimentally. The simulations are validated against Test No.1 conducted by INERIS (Bouet et al., 2005) of 460 s release duration with ammonia concentration decay measured up to 800 m downwind of the release nozzle. The computational domain was designed to represent a large-scale atmospheric dispersion scenario in conditions of meandering wind currents. The atmospheric turbulence is simulated by incorporating real-time meteorological data on wind direction and speed oscillations. The proposed methodology accounts for meandering wind currents. This methodology, combined with sub-grid scale Smagorinsky-Lilly turbulence modelling, enables accurate simulations of ammonia dispersion observed in the experiment. The simulations reproduced measured in the near-field (20 m from the release nozzle) transient ammonia concentration with high accuracy. The simulations also accurately captured the average concentration decay up to 800 m downwind of the release location. The hazard distance defined by the flammability of the ammonia-air mixture is estimated as 13.2 m from the release. The maximum toxicity cloud envelope extends to 205 m downwind, 9.5 m vertically, and 21.3 m laterally for the fatality threshold and increasing to 837 m, 18 m, and 53 m, respectively, for the injury limit. The study highlights the importance of proper modelling and simulations of real wind meandering currents for predicting realistic hazard distances.”

 

The full report is accessible via: https://doi.org/10.1016/j.jhazmat.2025.138712

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

Blast wave structure of boiling liquid expanding vapour explosions (BLEVE) for liquid hydrogen (LH₂) storage is not fully understood. There is a lack of experimental and numerical studies on underlying physical phenomena. This study develops a CFD model able to simulate multiple pressure peaks of the blast wave accounting for both the effect of combustion on the strength of blast wave generated by the compressed gaseous hydrogen (CGH₂) in ullage space, and the slower process of flashing boiling of the liquid phase resulted from pressure drop. The simulations reproduced the measured overpressures and multi-peak structure of blast wave observed in the BLEVE tests performed by BMW. It is confirmed that the larger first pressure peak is produced by the CGH₂ shock fed by combustion. The flash boiling of LH₂ during pressure drop produces a series of follow-up pressure waves. Combustion contribution to the entire blast wave dynamics is demonstrated.”

 

D. Cirrone, D. Makarov, V. Molkov, The multi-peaks structure of the blast wave generated by a liquid hydrogen storage tank BLEVE. International Journal of Hydrogen Energy 2025;133:416-430.

The full report is accessible via: https://doi.org/10.1016/j.ijhydene.2024.10.392

For related publications please see Resources – UK National Clean Maritime Research Hub

“Abstract

The aim of this study is to develop a contemporary CFD model of the multiphase flow of ammonia from a bulk liquid part of the storage vessel through the release piping to the atmosphere. The model is validated against the experiment with a 12 m3 tank pressurised to 0.5357 MPa(g), i.e. Test No.4 of 560 s duration conducted by INERIS with release from the liquid bulk. The volume-of-fluid (VOF) method is applied for shared velocity and temperature of liquid and vapour phases of ammonia. The heat and mass transfer between liquid and vapour is simulated by modified Lee’s evaporation-condensation model, accounting for the heat transfer from/to equipment and environment. A unique feature of the model is the phase change mechanism with varying mass transfer rates based on the transient volume fractions of liquid and vapour in a multiphase flow. This allowed to account for computationally unaffordable simulations of changing in time contact surface area between dispersed liquid and gaseous phases and avoid associated numerical complications. The model effectively captures the complex heat and mass transfer phenomena, including the cooling effect of evaporation in the piping and at the nozzle. The value of the time relaxation parameter and a multiplier accounting for the increase of contact surface between liquid and vapour in the pipe flow are defined by the inverse problem method through the comparison of simulations with the experiment. Simulations accurately reproduced experimental pressure and temperature dynamics in the storage tank, piping system and nozzle, and the total released mass of ammonia of 2352 kg.”

 

The full report is accessible via: https://doi.org/10.1016/j.ijheatmasstransfer.2025.127097

For related publications please see Resources – UK National Clean Maritime Research Hub