## 2 Materials and Methods  
### 3D Geometry of Pressurized Cabin  
Figure 1 illustrates the architectures of a conventional open-cathode fuel cell (OCFC) system (top) and a novel pressurized cabin-based OCFC system (bottom). These architectures are designed for hydrogen-based energy generation, with distinct configurations for air and hydrogen supply management. The conventional OCFC system consists of a simple and straightforward layout. A hydrogen tank provides the fuel supply, regulated by a pressure regulator and controlled by a solenoid-actuated supply valve. The hydrogen is delivered to the OCFC stack, where it reacts with oxygen from the surrounding air to produce electricity. The airflow is managed by three fan blades located above the OCFC stack, which direct ambient air at atmospheric pressure into the system without any pressurized cabin. A purge valve is included to remove exhaust gases, ensuring optimal operation. However, this configuration limits performance due to the reliance on ambient air pressure. The novel system introduces a pressurized air cabin to address the limitations of the conventional design. An air compressor replaces the fan blades to intake ambient air and increase its pressure. The pressurized air is then delivered to the OCFC stack, which operates within the pressurized cabin. This design enhances oxygen availability and improves reaction  
efficiency. The hydrogen supply system remains similar to the conventional configuration, with the fuel tank, pressure regulator, and solenoid-actuated supply valve feeding the stack. The purge valve also serves the same purpose of exhaust management. Additionally, the air outlet ensures proper airflow dynamics within the pressurized cabin. The primary goal of the novel pressurized cabin design is to significantly enhance the oxygen pressure at the stack, thereby improving the overall performance of the OCFC system compared to the conventional setup. This modification is expected to enable better operational efficiency under varying environmental conditions.  
Effective air supply management is essential for optimizing the performance of proton exchange membrane fuel cells (PEMFCs), as the oxygen excess ratio (OER) significantly influences system efficiency and stability. Since the optimal OER varies with the operating current, maintaining an appropriate oxygen supply is crucial to prevent oxygen starvation while avoiding excessive air intake. An inadequate OER can lead to reduced electrochemical reaction rates and irreversible cell damage, whereas an excessively high OER increases parasitic power loss, reducing overall system efficiency. Therefore, real-time control strategies for OER, such as self-tuning and adaptive management techniques, have been developed to dynamically adjust oxygen supply under varying load conditions. These methods enhance system voltage stability, efficiency, and longevity by mitigating transient overshoots and improving energy utilization. In this study, the focus will be on increasing the uniformity index and reducing pressure loss to minimize the impact of the OER. The cabin design will be developed in line with these objectives.  
Figure 1: Conventional OCFC architecture (**top**) and novel pressurized cabin architecture (**bottom**).