Abstract
Hydrogen has a wide range of energy applications, but hydrogen energy systems can suffer from high-concentration leaks that pose security risks, therefore making the measurement of high-concentration hydrogen very important. Traditional ultrasonic gas-detection methods are based mainly on ultrasonic time-of-flight measurements and can be divided into threshold-detection and phase-difference techniques. Threshold detection suffers from low resolution and a complex structure in gas detection, while the phase-difference technique has high resolution and a simple structure but can only measure the time of flight within one period of the ultrasonic signal. In this study, a dual-frequency phase-difference technique is proposed that solves the problem of multi-period phase detection with the phase-difference technique and can be used to detect high-concentration hydrogen. Simulation analysis and an experiment show that the proposed technique can measure the multi-period phase difference accurately. The maximum hydrogen concentration can reach 50% with an uncertainty of less than 5%, which meets commercial requirements.
Highlights
As an efficient and pollution-free source of clean energy, hydrogen is regarded as the most likely candidate to replace traditional fossil fuels
The relationship between the true PD and hydrogen concentration in the air at 300 K is shown in Fig. 7, where the triangles indicate the experimental PD values measured by the DFPD method and the solid line indicates the theoretical PD values calculated using Eq (7)
We found that the relative error in the results of the DFPD measurements was approximately half the error yielded by time of flight (TOF), which is a significant improvement in accuracy
Summary
As an efficient and pollution-free source of clean energy, hydrogen is regarded as the most likely candidate to replace traditional fossil fuels. Two methods are currently used to ultrasonically measure the concentration of hydrogen gas based on acoustic attenuation and sound velocity. The former is based on the fact that acoustic attenuation varies with gas concentration, and the latter involves measuring the peak value of the signal at the ultrasonic receiver.. The measurements of gas concentration based on sound velocity are based on the fact that the velocity of sound differs in gas mixtures of different concentrations This method has the advantages of a fast response, low power consumption, wide range of detection, and simple structure. The range of measurement of hydrogen concentration is limited by the fact that the PD can reflect only the TOF within one period of the ultrasonic signal used. The results of simulations and an experiment show that the DFPD method can be used for the measurement of high concentrations of hydrogen–air mixtures
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