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The study investigates the effect of water injection on compressor efficiency and relative humidity in a fuel cell system, achieving up to 7.83% reduction in specific work and 2.3% reduction in mechanical power.

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Coulombic efficiency7.83%

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What they did

System
MEC

What worked

Coulombic efficiency7.83%best of 2

Abstract

Hydrogen fuel cells offer a promising and environmentally friendly solution for future ground transportation systems, especially for heavy-duty truck applications. The fuel cell system generates electricity to power the vehicle through the chemical reaction between hydrogen and oxygen in the fuel cell stack. Oxygen is supplied by pumping compressed air into the fuel cell stack. To achieve optimal performance with minimal electrochemical losses, precise control of air and hydrogen flow within the fuel cell stack is crucial. One key factor affecting fuel cell performance is the air relative humidity (RH). In this study, we focus on developing an efficient air humidity management system through the direct injection of water into a twin vortices series compressor (TVS R1320). The goal is to experimentally measure the effect of water injection on compressor efficiency and the attainable RH without water droplet formation at the inlet of the fuel cell stack. The experimental results show that for high air mass flow rates, specific work and mechanical power can be reduced by up to 7.83% and 2.3%, respectively, while the system isothermal efficiency improved by 2.95%. However, the RH required by fuel cells cannot be achieved solely by direct water injection without the risk of water droplet formation that can lead to fuel cell flooding. Other operating points will be discussed in detail. Furthermore, modeling activities were conducted to identify trends and better explain the effects of injected water. Limitations were also found in 1D simulation codes when modeling evaporation. A simplex nozzle was positioned at the compressor inlet to continuously inject water, and optically accessible sections located upstream and downstream of the compressor allowed for recording the air-water flow status.

Key findings

  • Water injection reduces compressor efficiency by up to 7.83% for high air mass flow rates.
  • The system isothermal efficiency improves by up to 2.95% with water injection.
  • Compressor performance is affected by water injection, but the impact on fuel cell performance is not fully explored.

Keywords

Gas compressorHumidityAutomotive engineeringRoot (linguistics)

Identifiers

DOI
10.1177/14680874251338922
Journal
International Journal of Engine Research
Year
2025