[Study on Line CARS for Temperature Measurement in Combustion Flow Field].

Some laser beams meet at a single point by a convex len in normal coherent anti-Stokes Raman scattering (CARS), and the CARS signal with temperature information of the focal piont yields under phase matching. Normal CARS can only get the temperature of one spatial piont in one measurement, which can not meet the needs of deep research on combustion flow field. In order to get more information in one test and improve the measuring capacity of CARS, line CARS (L-CARS) was presented. In L-CARS, convex lens are replaced by cylindrical convex lens to get a focal line, and nearly all the points on the line meet the phase matching. So, the CARS signal of each point on the line yield in one test. Cylindrical convex lens are also used in subsequent beam path to focus the CARS signals into spectrometer, and ICCD camera transfers the signals to computer to acquire the temperature of each point. Then, the measuring capacity of CARS is advanced from piont measuring to line measuring. Experimental results based on plain flame furnace suggest that L-CARS can acquire about 200 points' temperatures effectively in one test, and the length of the measuring line is about 3.6mm. The spatial resolution is about 18µm and the uncertainty is less than 7%, which is as the same as the ordinary CARS's.

[Vibrational and rotational spectrum of carbon monoxide at high temperature].

The total partition function was calculated for carbon monoxide with approximation. Using the dipole moment function and the wave function with Morse approximation, we computed the matrix elements of vibrational-rotational transition and absorption coefficient at normal and high temperature. The computed results agreed with the HITRAN database and literature, which shows that the calculation of total partition function and matrix elements of vibrational-rotational transition is reliable. Furthermore, the absorption coefficient and radiant spectrum are also presented at higher temperature of 4 000 and 6 000 K.

[Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system].

In the present paper, the signal of a tunable diode laser absorption spectroscopy (TDLAS) trace gas sensing system, which has a wavelength modulation with a wide range of modulation amplitudes, is studied based on Fourier analysis method. Theory explanation of spectrum distortion induced by laser intensity amplitude modulation is given. In order to rectify the spectrum distortion, a method of synchronous amplitude modulation suppression by a variable optical attenuator is proposed. To validate the method, an experimental setup is designed. Absorption spectrum measurement experiments on CO2 gas were carried out. The results show that the residual laser intensity modulation amplitude of the experimental system is reduced to -0.1% of its original value and the spectrum distortion improvement is 92% with the synchronous amplitude modulation suppression. The modulation amplitude of laser intensity can be effectively reduced and the spectrum distortion can be well corrected by using the given correction method and system. By using a variable optical attenuator in the TDLAS (tunable diode laser absorption spectroscopy) system, the dynamic range requirements of photoelectric detector, digital to analog converter, filters and other aspects of the TDLAS system are reduced. This spectrum distortion correction method can be used for online trace gas analyzing in process industry.