Noncontact Quantitative Temperature Field Reconstruction of Axisymmetric Flames With Phase Measurement Deflectometry

The increasing demand for precise measurement of high-temperature, high-speed flow fields in aerospace applications highlights the limitations of traditional contact-based methods, which often suffer from poor dynamic response and the risk of disrupting the flow field. To address these challenges, this article proposes a temperature reconstruction deflectometry (TRD) method for noncontact measurement of axisymmetric temperature fields. By employing orthogonal sinusoidal fringe patterns to encode the absolute spatial coordinates on the LCD, the light ray deflection angles can be derived from position shifts and related to refractive index gradients, providing the foundation for accurate temperature reconstruction without relying on Gaussian imaging assumptions. To validate this method, an inverse ray-tracing simulation is conducted to confirm its accuracy through numerical results. Experimental results demonstrate that the TRD method provides higher reconstruction resolution and shows good agreement with K-type thermocouple measurements. While sharing the low-cost and noncontact advantages of traditional background-oriented schlieren (BOS) methods, the proposed approach achieves higher spatial resolution and enhanced displacement detail capture through absolute position encoding. This provides a robust solution for accurate, real-time temperature measurements, making it a promising tool for applications in aerospace, fluid dynamics, industrial diagnostics, and thermal process monitoring.