Study on the concentration changes of superfine powder extinguishing agent calibration device and the effect of probe contamination under different inlet airflows

The calibration process of superfine powder extinguishing agent probe affects the measurement accuracy, which is related to the accuracy of spatial concentration distribution measurement. In this paper, the effect of inlet airflow on concentration changes and probe contamination was investigated by means of a falling calibration device using NaHCO3 superfine powder extinguishing agent, which has a high potential for application in the engine compartment of an aircraft, as an example. It was found that the inlet airflow and belt velocity determined the occurrence concentration of superfine powder extinguishing agent in the calibration device. The relationship between concentration and belt velocity was found to be an exponential function for different airflows. The least probe contamination was observed at concentration c=50 g/m3 and inlet airflow q=186.35 L/min. Larger concentrations of extinguishing agent and lower inlet airflows lead to increased contamination during probe calibration. Reducing the contamination of the measuring probe improves the accuracy of the superfine powder extinguishing agent calibration.