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Combined thermographic measurement and heat-flux compensation methods for aerodynamic heating evaluation in hypersonic flight

Kento Inokuma, Aiko Yakeno, Yoshiyuki Watanabe, Kiyonobu Ohtani

Abstract

Novel thermographic measurement and heat-flux compensation methods combined for evaluating aerodynamic heating in hypersonic flight were developed using high-speed thermography. A hypersonic spherical projectile with a diameter of 8 mm was launched at approximately Mach 5 in the test section of a ballistic range. Shadowgraph imaging was conducted to visualize the flight trajectory and the shock layer. Thermographic measurement was performed using a high-speed infrared (IR) camera to obtain the surface temperature distribution of the projectile. The temperature distribution on the spherical surface was reconstructed from the thermographic data, by considering the photoresponse time of the photodetector of the IR camera and the geometric characteristics of the projectile trajectory. Furthermore, to validate the shock-layer geometry and aerodynamic heating characteristics, a computational fluid dynamics (CFD) simulation was also performed. The shadowgraph results showed that a detached shock wave and a shock layer were formed in front of the projectile, consistent with the CFD result. From the thermographic result, it was found that the maximum surface temperature rise during the flight was 24.4 K above the ambient temperature and it decreased with increasing distance from the stagnation point. The Stanton number distribution was estimated from the reconstructed surface temperature by assuming a one-dimensional transient heat conduction caused during the flight. The stagnation Stanton number was calculated to be 0.00366, which was also consistent with both the CFD result and a previously reported empirical correlation.

Combined thermographic measurement and heat-flux compensation methods for aerodynamic heating evaluation in hypersonic flight

Abstract

Novel thermographic measurement and heat-flux compensation methods combined for evaluating aerodynamic heating in hypersonic flight were developed using high-speed thermography. A hypersonic spherical projectile with a diameter of 8 mm was launched at approximately Mach 5 in the test section of a ballistic range. Shadowgraph imaging was conducted to visualize the flight trajectory and the shock layer. Thermographic measurement was performed using a high-speed infrared (IR) camera to obtain the surface temperature distribution of the projectile. The temperature distribution on the spherical surface was reconstructed from the thermographic data, by considering the photoresponse time of the photodetector of the IR camera and the geometric characteristics of the projectile trajectory. Furthermore, to validate the shock-layer geometry and aerodynamic heating characteristics, a computational fluid dynamics (CFD) simulation was also performed. The shadowgraph results showed that a detached shock wave and a shock layer were formed in front of the projectile, consistent with the CFD result. From the thermographic result, it was found that the maximum surface temperature rise during the flight was 24.4 K above the ambient temperature and it decreased with increasing distance from the stagnation point. The Stanton number distribution was estimated from the reconstructed surface temperature by assuming a one-dimensional transient heat conduction caused during the flight. The stagnation Stanton number was calculated to be 0.00366, which was also consistent with both the CFD result and a previously reported empirical correlation.
Paper Structure (14 sections, 4 equations, 14 figures, 3 tables)

This paper contains 14 sections, 4 equations, 14 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Methodology
  3. Ballistic range
  4. Shadowgraph
  5. Thermography
  6. Experimental conditions
  7. Numerical method
  8. Results and discussions
  9. Shadowgraph results
  10. Thermographic results
  11. Temperature dirstibution
  12. Stanton number distribution
  13. Measurement uncertainty
  14. Conclusions

Figures (14)

  • Figure 1: Schematic of the ballistic range (adapted from numata2008experimental)
  • Figure 2: Schematic of the optical setup for the shadowgraph experiment
  • Figure 3: Schematic of the experimental apparatus for the thermography measurement
  • Figure 4: Schematics of the computational domain: (a) Boundary geometries and (b) central cross-sectional view of the computational mesh
  • Figure 5: Shadowgraph snapshots of the projectile in flight; the time interval between frames was 45 $\mathrm{\mu}$s
  • ...and 9 more figures