The challenges of high-humidity operating conditions for aircraft environmental control systems: Dehumidification adaptability and improvement strategies

High-humidity environments challenge aircraft environmental control systems (ECS) by inducing outlet free water droplet and pipe icing/clogging, endangering flight safety. To address ECS dehumidification limitations under high-humidity conditions, this study employs the enthalpy method and endoreversible thermodynamic analysis to investigate three typical configurations (three-wheel, split four-wheel, enhanced split four-wheel bootstrap systems) and derive their thermal characteristic expressions, thereby revealing the mechanism of heat-moisture-work conversion. Comparative analysis yields wet condition design strategies: staged expansion can mitigate the extremely low temperature caused by single-stage expansion, while an additional water separator is required to remove condensed water in the turbines. Furthermore, the effects of environmental parameters and key components on the dehumidification performance of ECS are systematically investigated. Sensitivity analysis identifies critical components, revealing the secondary heat exchanger effectiveness and compressor pressure ratio as most influential on dehumidification. Slight parameter optimization of these components improves the enhanced split four-wheel bootstrap system's ambient dew point adaptability from 20 °C to 27 °C. This study innovatively provides a comprehensive assessment of ECS thermal performance, improvement directions, and potential under high-humidity conditions, filling gaps in systematic thermodynamic analysis of ECS dehumidification limits and laying a solid theoretical foundation for enhancing ECS high-humidity adaptability.