In-situ noncontact measurement system for nozzle throat deformation in high-temperature gas heating via laser speckle digital image correlation with wavelet smoothing of displacement field

The shape of nozzle throat in an engine could greatly change the amount of thrust or heat transfer performance. To in-situ evaluate nozzle throat deformation in high-temperature gas heating tests, a non-contact full-field deformation measurement system via laser speckle Digital Image Correlation with wavelet smoothing of displacement field is proposed. For high-temperature thermal radiation suppression, high-power laser speckle pattern is used for digital image correlation calculation and multi-step filters with polarizers are used. A displacement field wavelet smoothing algorithm is proposed to mitigate imaging distortion caused by airflow disturbance. Gas heating experiments on a nozzle sample made of carbon fiber high silica phenolic resin com-posites were carried out. The full-field displacement measurement results show that compared with the commonly used air blade method, the proposed method can provide smoother displacement field for deformation evaluation, the displacement measurement difference of the proposed method and a dial indicator was within 0.01 mm.

Automated summary

This paper proposes a non-contact full-field deformation measurement system for evaluating nozzle throat deformation in high-temperature gas heating tests. By using laser speckle Digital Image Correlation with wavelet smoothing of displacement field, a smoother displacement field for deformation evaluation can be obtained.