The Brief Introduction of Different Laser Diagnostics Methods Used in Aeroengine Combustion Research

Table 1

Summary of different laser diagnostics for gas turbines.

Type	Merits	Drawbacks
PLIF	(i) It can be combined with PIV to measure the species concentration and velocity simultaneously.	(i) Fluorescence interferences are from other species, especially from hydrocarbons in high pressure reacting flows.; (ii) It is difficult for quantitative measurement.
CARS	(i) CARS signal could be detected in the presence of a strong fluorescent background.; (ii) Low absorption of the near-infrared excitation beams would significantly reduce the damage in samples.	(i) At very low concentrations, the advantages of the coherent addition for the CARS signal are reduced and the presence of the incoherent background becomes a problem.
RS	(i) It can measure multispecies concentration simultaneously.; (ii) It has high spatial and time resolution.; (iii) It has high accuracy results.	(i) The signal from a single molecule is weaker than the CARS signal.; (ii) The measurement zone is only a point.; (iii) The laser source is relatively expensive.
TDLAS & TDLAT	(i) Low detection limits.; (ii) Determining the temperature, pressure, and velocity.	(i) Any noise introduced by the light source or the optical system will deteriorate the detectability and precision.
MTV	(i) It has high spatial and time resolution.; (ii) Multipoint in the flow field is measured simultaneously.; (iii) It is especially suitable for supersonic flow field measurement.	(i) The system equipment is relatively expensive.; (ii) Some tagging molecule species are costly or toxic.