CARS setup for exhaust gas and combustion analysis

Coherent anti-stokes Raman spectroscopy (CARS) is introduced, and several existing CARS methods are discussed and compared. Application in vehicle research is attempted through necessary modification on the basis of classical CARS theory. Classical theoretical spectrum calculation model is still suitable for the new situation. The design of CARS setup, which provides solutions for not only exhaust gas analysis but also engine combustion evaluation, is put forward. As the typical probe molecule, N₂ is modeled for combustion evaluation while CO₂ is emphasized on exhaust gas analysis. For multi-species analysis, several advanced CARS methods are introduced and expanded setup design using dual-pump CARS is shown. Elementary analysis has demonstrated that CARS has the capabilities of combustion evaluation and exhaust gas analysis. Temperature measurement accuracy can be plusmn10 K or higher and spatial resolution can be 1 cm or higher according to the instrument performance. Despite of some drawbacks the setup we developed can be useful for vehicle detection.