Pressure and Heat Flux Calibration of the Long-test-duration Hypervelocity Detonation-driven Shock Tunnel

2017 ◽  
Author(s):  
Qiu Wang ◽  
Ji Wei Li ◽  
Pan Lu ◽  
Jin Ping Li ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Heat Flux ◽  
Shock Tunnel ◽  
Test Duration ◽  
Flux Calibration

Aerodynamic Drag Measurement in a High-Enthalpy Shock Tunnel

2018 ◽  
Author(s):  
Yunpeng Wang ◽  
Zonglin Jiang ◽  
Honghui Teng
Keyword(s):  
Natural Frequencies ◽  
Aerodynamic Drag ◽  
Aerodynamic Force ◽  
Mechanical Vibration ◽  
Low Frequency ◽  
Shock Tunnel ◽  
Test Time ◽  
Test Duration ◽  
Flow State ◽  
High Enthalpy

Shock tunnels create very high temperature and pressure in the nozzle plenum and flight velocities up to Mach 20 can be simulated for aerodynamic testing of chemically reacting flows. However, this application is limited due to milliseconds of its test duration (generally 500 μs–20 ms). For the force test in the conventional hypersonic shock tunnel, because of the instantaneous flowfield and the short test time [1–4], the mechanical vibration of the model-balance-support (MBS) system occurs and cannot be damped during a shock tunnel run. The inertial forces lead to low frequency vibrations of the model and its motion cannot be addressed through digital filtering. This implies restriction on the model’s size and mass as its natural frequencies are inversely proportional the length scale of the model. As to the MBS system, sometimes, the lowest natural frequency of 1 kHz is required for the test time of typically 5 ms in order to get better measurement results [2]. The higher the natural frequencies, the better the justification for the neglected acceleration compensation. However, that is very harsh conditions to design a high-stiffness MBS structure, particularly a drag balance. Therefore, it is very hard to carried out the aerodynamic force test using traditional wind tunnel balances in the shock tunnel, though its test flow state with the high-enthalpy is closer to the real flight condition.

Schmidt-Boelter Heat Flux Gage Sensitivity Coefficients in Radiative and Convective Environments

2011 ◽  
Author(s):  
James T. Nakos ◽  
Alexander L. Brown
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat ◽  
Radiative Heat ◽  
Sensitivity Coefficient ◽  
Calibration Standard ◽  
Convective Heat Flux ◽  
Sensitivity Coefficients ◽  
Theoretical Sensitivity ◽  
Flux Calibration

Commercial Schmidt-Boelter heat flux gages are always calibrated by using a radiative heat flux source where convection is minimized. This is because one can establish a reliable link to a National Institute of Standards and Technology (NIST) calibration standard. To the authors’ knowledge, no NIST traceable link exists for convective heat flux calibration. When heat flux gages are used in typical applications, convection is often not negligible. It has been common practice to assume that the sensitivity coefficient supplied by the manufacturer also applies for convective environments. This assumption is believed to be incorrect. If incorrect, this would result in uncertainties larger than typically reported (e.g., ±3%). This paper analyzes the heat transfer from an idealized Schmidt-Boelter heat flux gage. The analysis shows that the theoretical sensitivity coefficients in purely radiative and convective environments are not the same and, in fact, differ by the emissivity of the gage surface. The implication of this difference is that the accuracy specification supplied by the manufacturer (typically ± 3%) is not correct for measurement applications where convection is not negligible.

A New Thermophysical Property Estimation Approach Based on Calibration Equations and Rescaling Principle

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Y. Y. Chen ◽  
M. Keyhani ◽  
J. I. Frankel
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Diffusivity ◽  
Thermophysical Property ◽  
Slab Thickness ◽  
Temperature Calibration ◽  
Calibration Equation ◽  
Property Estimation ◽  
Calibration Equations ◽  
Flux Calibration

A novel thermophysical property estimation method is proposed, which incorporates both calibration and rescaling principles for estimating both unknown thermal diffusivity and thermal conductivity of materials. In this process, temperature and heat flux calibration equations are developed, which account for temperature-dependent thermophysical property combinations. This approach utilizes a single in-depth temperature measurement and a known set of boundary conditions. To acquire both thermal diffusivity and thermal conductivity, two distinct stages are proposed for extracting these properties. The first stage uses a temperature calibration equation for estimating the unknown thermal diffusivity. This process determines the thermal diffusivity by minimizing the residual of the temperature calibration equation with respect to the thermal diffusivity. The second stage uses the estimated thermal diffusivity and a heat flux calibration equation for estimating the unknown thermal conductivity. This stage produces the desired thermal conductivity by minimizing the residual of the heat flux calibration equation with respect to the thermal conductivity. Results verify that the proposed estimation process works well even in the presence of significant measurement noise for the chosen two representative materials. The relative error between the exact properties and the estimated values is shown to be small. For both test materials (stainless steel 304 and a representative carbon composite), the maximum relative prediction error is approximately 2–3%. Finally, as an added benefit, this method does not require explicit knowledge of the slab thickness or sensor position which further reduces systematic errors.

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