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This study presents a single-line absorption spectroscopy method for the simultaneous measurement of gas pressure and temperature through diode laser absorption spectroscopy using a single absorption line. In the proposed method, the absorbance loss of an absorption line that may occur during baseline subtraction is predicted, and the gas properties are determined by matching a calculated absorbance to a recovered absorbance using the predicted loss. To verify the proposed method, gas property measurements are conducted for air conditions with a pressure range of 10–100 kPa and a temperature range of 300–500 K. An absorption line in the oxygen A band is selected to measure the gas properties of air. Using the proposed method, it is confirmed that the gas pressure and temperature could be measured within errors of 25 % and 18 %, respectively. When the gas pressure is predetermined using a pressure gauge, the gas temperature can be measured within an error of 14 %. [ABSTRACT FROM AUTHOR]

The performance evaluation of a model scramjet intake according to the isolator height was conducted numerically under a free-stream Mach number 6. The numerical results were verified using the wall pressure and shock wave angle at the scramjet intake for a single case with a 4 mm isolator height. It was confirmed that the difference between the measured values and numerical results for the scramjet intake was less than 10 %. Upon verifying the reliability of the numerical analysis, the performance of the model scramjet intake was investigated using scramjet intake performance parameters, such as the shock wave pattern, static pressure ratio, static temperature ratio, total pressure recovery, air capture ratio, intake drag coefficient, and adiabatic kinetic energy efficiency for 3–5 mm isolator height. The performance of the model scramjet intake has a trade-off relationship with the height of the isolator. [ABSTRACT FROM AUTHOR]

A single-body typed TDLAS sensor was developed, and its robustness and performance were experimentally evaluated under harsh thermal and mechanical environments which could be formed in scramjet intake. To confirm integrity and operability of the TDLAS sensor in the harsh thermal environments, high-thermal gradient, long-duration heating, and aero-heating tests were conducted. The high-thermal gradient, long-duration heating, and aero-heating tests were performed using high-temperature torch, furnace, and supersonic wind tunnel, respectively. In addition, vibration, mechanical shock, and acceleration tests were performed to analyze the durability and operating performance of the TDLAS sensor in the harsh mechanical environments. The vibration/mechanical shock, and acceleration tests were carried out using shaker and centrifuge, respectively. The TDLAS sensor did not experience any damage and had a stability of signal measurement under these severe thermal and mechanical environments. The experimental test results showed that the single-body TDLAS sensor in this paper could be used in the extreme thermal and mechanical conditions which could be formed in the scramjet intake. [ABSTRACT FROM AUTHOR]

This study presents an absorption-area-based method for the measurement of gas flow velocity using diode laser absorption spectroscopy. In the proposed method, the gas flow velocity is determined using the area difference between the absorption lines. To verify the proposed method, flow velocity measurements are conducted for test conditions with a velocity range of 5–30 m/s in a low-speed wind tunnel, and the results are compared with those of the conventional method using the Doppler-shifted peak. Oxygen in the air is selected as the target gas. By comparing the flow velocity measurement results of the conventional method and the proposed area-based method, it is confirmed that the measurement precision is improved when the proposed area-based method is used. Moreover, the measurement accuracy of the proposed area-based method is significantly improved at a relatively low-speed range of 5–10 m/s compared to the conventional method. [ABSTRACT FROM AUTHOR]

The ablation characteristics of aluminum alloy 7075 wings with and without a coating were analyzed experimentally using an oxy—kerosene torch. The wing surface coating was fabricated using the thermal spray coating method using yttria partially—stabilized zirconia as a coating material. The thickness of the coated layer was approximately 200 μm. The test condition was the heat flux of 4.12 MW/m2, the stagnation pressure of 130 kPa, and the static temperature of 1,350 K. The ablation characteristics were investigated by analyzing the ablation rate, and the shape and surface changes after the test. The uncoated and coated wings began to ablate after 1.5 and 8 sec heating, respectively. The ablation rates were 176±1.2 mg/sec for the uncoated wing and 11±1.1 mg/sec for the coated wing after 2 sec of heating. The surface morphology was investigated by analyzing the microstructures and atomic compositions of the wing before and after the test. The surface microstructure and atomic composition of the uncoated wing were completely changed, while the coated wing remain relatively unchanged within the 2 sec of heating. [ABSTRACT FROM AUTHOR]

In this study, temperatures of multiple gas slabs are measured from a single absorption line using a tunable diode laser absorption spectroscopy technique. While typical laser absorption spectroscopy techniques require two or more absorption lines to determine the gas temperatures, however, this study presents the temperature determination method using an absorption line and its conditions for successful application. To generate two air slabs along with a single laser path, a gas heating apparatus composed of two chambers is used. The air is used as a test gas and a tunable diode laser absorption spectroscopy system is set up to detect an absorption line of the oxygen molecule in the air. Using the spectroscopic characteristics that the line shape and absorption strength are functions of gas properties and beam path length, temperature values of multiple gas slabs are experimentally determined by matching a measured spectral absorbance with a calculated one with known pressure and beam path length values. The determined temperatures are compared with temperature values set using thermocouples. It is observed that the temperatures of the gas slabs can be successfully measured when the pressures of the gas slabs are considerably different. The effect of gas properties and beam path length on the temperature determination is discussed. Measurement uncertainty due to random noise in the signal is investigated through a simulation approach. • Temperature measurement methodology for multiple gas slabs is proposed using the laser absorption spectroscopy technique. • Only a single absorption line is utilized for temperature measurement. • Gas condition for good measurement accuracy is analyzed through experimental and simulation analysis. • Using the proposed procedure, the gas temperatures of the gas slabs can be determined when the pressures of the gas slabs certainly differ. [ABSTRACT FROM AUTHOR]