Development of laser combustion diagnostic techniques for ground aero-engine testing

Laser-based diagnostic techniques have the characteristics of non-intrusiveness, high temporal-spatial resolution and abundant measurement information, and have been demonstrated as powerful and indispensable tools for the turbulent combustion research of various engine devices.This paper reviews the basic principle, research status and development trend of several laser spectroscopic techniques, which have been used successfully in the measurements of engine combustion.Since there is no single laser diagnostic technique that can be applied under all circumstances, the particular application must be carefully considered according to the type of combustion flow and measurement requirements.For the temperature measurements, Coherent Anti-stokes Raman Scattering (CARS), as a point-wise technique, yields the best accuracy of less than 5% uncertainty for single-shot measurements.And the two color Planar Laser Induced Fluorescence (PLIF) technique may be employed to study temperature gradients or temperature fields but may lead to reduced absolute accuracy.For the velocity measurements, the Particle Image Velocimetry (PIV) technique is suitable for fine measurements of low-speed flow field, while the Hydroxyl Tagging Velocimetry (HTV) technique has been applied in high-temperature supersonic and even hypersonic flow fields with uncertainty less than 4%.In species concentration measurements, the Spontaneous Raman Scattering (SRS) and PLIF are used to measure the main components and the distribution of intermediate products, respectively.In terms of the high-temporal-spatial-resolution measurements of temperature, velocity and species concentrations in the aero-engine combustor, this paper reviews the basic principle, research status and development trend of relevant laser combustion diagnostic techniques.