Study on measurement of diesel Exhaust Velocity based on Absorption spectroscopy and Doppler effect

Non-contact on-line measurement of gas velocity is of great significance in the experimental research of high-speed flow field such as engine. Based on the Doppler frequency shift effect of absorption spectrum, a high-speed airflow velocity measurement system was designed and built, and the high-speed airflow velocity accelerated by compressor nozzle was detected online in real time. The experiment chooses H2O characteristic absorption lines near 1392 nm. Then the experimental measurement was carried out to obtain the data. Through the calculation and analysis of the data, the flow rate of about 70m/s was obtained, and the relative error could be controlled within 5.8%. Using Origin software, connected with the experimental system, the corresponding absorption spectrum line was obtained, which realized the real-time on-line measurement of flow velocity that the traditional method could not do. This paper analyzes the shortcomings of the system and lists several possible solutions. On this basis, the lower limit of measurement that the system can achieve is 25.9 m/s, which lays a foundation for the further optimization of the system and the development of the whole device.