The new hydrogen flow and concentration sensor from Allengra is designed for use in the anode recirculation of PEM fuel cells and is intended to capture all the necessary parameters that need to be measured at this point.
A well-adjusted recirculation of unreacted hydrogen ensures optimal utilization of the fuel and minimizes water accumulation. Nitrogen crossover is also an important parameter to measure in order to prevent its accumulation in the stack. These data can be used to determine the operating point that best balances efficiency and service life. However, conventional calorimetric and thermal measurement methods reach their limits in PEM fuel cells, according to Allengra. High humidity and condensate attack the technology. In addition, these measurement methods cannot detect the gas composition. If this fluctuates – which is particularly the case during purging (purge cycle) – conventional measurement methods cannot respond appropriately.
Allengra, on the other hand, relies on ultrasound as a robust measurement principle. According to the manufacturer, the new sensor is the only one on the market that simultaneously measures mass and volume flow and analyzes the composition of the gas from hydrogen, nitrogen and water vapor in real time. Integrated sensors also measure temperature, pressure and humidity.
At high hydrogen concentrations, it achieves an accuracy of < 0.5% for gas composition and 3% of the measured value for volume flow measurement. The measured values and additional diagnostic data are transmitted via CAN bus and Modbus interfaces.
The housing is made of stainless steel 316L. The operating range extends up to 85 °C, up to 16 bar pressure and up to 100% relative humidity. The sensor tolerates liquid water in droplet form “to a certain extent”.
The hydrogen flow meter is available in two versions: DN15 for flow rates from 10 to 1,000 L/min and DN20 for 20 to 1,700 L/min. Both models are 173 mm long and have standard threaded connections. Potential applications include automotive, stationary systems such as emergency power supplies, and aviation.
For series applications, Allengra offers customized adaptations of the hydrogen sensor. 
More information: allengra.eu
