Transmission detection of the visibility in the tunnel
As a semi-closed columnar space, the tunnel has the characteristics of long depth, poor air circulation, coupled with the friction between vehicle tires and the ground as well as exhaust emissions are easy to cause visibility decline, seriously endangering the safety of the passengers. And blind ventilation will cause energy waste. Therefore, real-time monitoring of the visibility in the tunnel is of great significance. At present, various visibility detection instruments at home and abroad have many shortcomings and defects, such as the scattering measuring instrument has a limited detection range and cumbersome data processing, while the traditional transmission-type measuring instrument has a long optical path and is difficult to adjust, and is affected by the fluctuation of light source and background light, so the measurement accuracy is poor. At present, most of the visibility detection instruments in the market are imported from abroad. Their accuracy and measuring range do not fully meet the requirements of the tunnel detection in China, and they are expensive and inconvenient to maintain. According to the requirements of the visibility detection index in highway tunnel design specification, the joint research team of Guilin University of Electronic Technology and Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, designed the transmission-type visibility detection instrument to meet the requirements of the visibility detection under different air transmittance conditions, and to control the tunnel fans according to the real-time measurement results.
The joint scientific research team of Guilin University of Electronic Technology and Anhui Institute of Optics and Fine Mechanics has been committed to the design and research of optical detection instruments, including the detection of atmospheric OH free radical and the detection of Raman spectrum of dangerous substances, among which the detection of atmospheric visibility has achieved remarkable results. Aiming at the fluctuation of the light source of the traditional visibility detector, this paper proposes a method of double-light path measurement with reversion, and introduces a reference light path to monitor the light power of the light source in real time, reducing the measurement error. In order to meet the measurement requirements under the condition of low visibility, high-responsivity silicon detectors and cross-impedance amplifying circuit were used to complete the conversion and amplification of photoelectric signals. After analog-to-digital conversion of the collected photoelectric signal, the corresponding visibility value is calculated by the single chip microcomputer, which is carried out by variety of ways according to the site needs. The results of indoor simulation experiments show that the extinction coefficient measurement range is 3.7-118.82 km-1 (corresponding to visibility 25-900 m), the maximum relative measurement error is 8.4%, and the system stability is better than 0.12 km-1. It meets the requirements of tunnel visibility detection index in China.
Fig.1 Schematic of optical structure
Fig.2 Schematic diagram of visibility test experiment
About The Group
The joint scientific research team of Guilin University of Electronic Technology and Anhui Institute of Optics and Fine Mechanics is mainly engaged in the field of optical instrument design and application. Currently, there are 22 core members, including 2 senior titles, 8 intermediate titles, 6 PhD students, and 6 master students. In recent years, the research team has undertaken a number of national and provincial projects, focusing on scientific research and achievement transformation. The team has successfully developed the middle and upper atmosphere OH free radical super-resolution space heterodyne spectrometer , and the first domestic prototype of remote space heterodyne Raman spectrometer. In addition, they cooperated with many research teams and trained many excellent graduate students.
Ye Song, Bai Yunfei, Li Zhiwei, et al. Design of visibility detection system for tunnel based on transmission method[J]. Opto-Electronic Engineering, 2019, 46(10): 180607.