## 1 Introduction  
The maritime industry plays a crucial role in international trade, transporting approximately 80% of global cargo. However, it consumes over 300 million tons of fossil fuels annually and accounts for approximately 2-3% of total global greenhouse gas (GHG) emissions [1]. Large vessels (representing approximately 20% of the global fleet) are responsible for 85% of the sector's total GHG emissions. This emphasizes the urgent need to implement decarbonisation strategies to promote sustainable development in the shipping industry [2, 3, 4]. In this context, international organizations, including the International Maritime Organization (IMO), have emphasized the transition to eco-friendly marine fuels. Among these, ammonia has emerged as a potential highly advanced carbon-free marine fuel [5]. Ammonia is a carbon-free fuel. It provides a higher volumetric energy density than hydrogen and can be produced and transported using the existing infrastructure. Furthermore, it serves as an effective hydrogen carrier and has the potential to be pivotal in enabling a future hydrogen-based economy [6; 7; 8; 9]. Based on these advantages, institutions such as the International Transport Forum (ITF) and the International Energy Agency (IEA) have projected that ammonia will become a key marine fuel by 2050. Consequently, the amounts of global research and technological investments in ammonia-powered ships are rapidly increasing [10; 11]. Nevertheless, one of the most significant challenges in ammonia commercialization is safety concerns due to its high toxicity and explosiveness [12; 13; 14]. Although no major accidents involving ammonia-fuelled vessels have been reported, various incidents in land-based facilities provide crucial insights into the potential risks in maritime applications. According to the U.S. Occupational Safety and Health Administration (OSHA), 306 incidents of ammonia leakage have occurred since 1984. Of these, 58 involved fatalities [15]. For example, in 2013, a significant ammonia release at the Yara facility in Texas resulted in 15 deaths and more than 100 injuries. Similarly, in 1992, a catastrophic explosion of an ammonia tank in Dakar, Senegal, resulted in 129 deaths and over 1150 injuries [16; 17; 18; 19]. These severe land-based incidents indicate the need for stringent safety management systems when employing ammonia as a marine fuel. Fuel preparation rooms (FPRs), which are confined spaces where ammonia is stored, supplied, and mixed, are considered high-risk areas for explosions. To quantitatively assess the explosion hazards in such environments, a systematic analysis of the effect of the ignition location on explosion characteristics is crucial. Prior studies have identified the ignition position as a key parameter that influences the explosion pressure, rate of pressure increase, flame propagation characteristics, combustion behaviour, and thermal losses [20; 21; 22]. For example, [PERSON] et al. [20] observed that central ignition in methane-air mixtures generated the highest explosion pressure and lowest heat loss. In contrast, ignition near the walls or bottom produced lower pressures and higher heat dissipation. [PERSON] et al. [21] observed that the ignition location significantly influences the flame dynamics and pressure distribution in hydrogen-air mixtures. Similarly, [PERSON] et al. [22] reported that the ignition position affects pressure wave interactions and the explosion-induced vibrations in methane-air mixtures. This study provides important insights into the management of flammable gases. These observations collectively emphasize the role of the ignition location as a critical variable in explosion dynamics, regardless of the gas type. However, existing studies have focused primarily on methane or hydrogen explosions, and investigations of ammonia explosions in confined environments remain limited.