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Li Yin

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Proceedings Article | 26 July 2024 Paper

The impact of chemical non-equilibrium models on the ultraviolet spectral radiation characteristics of shock layers

Huigang Shi, Lu Bai, Jun Zhou, Yin Li, Ligong Zhang

Proceedings Volume 13189, 131890F (2024) https://doi.org/10.1117/12.3032240

KEYWORDS: Ultraviolet radiation, Chemical reactions, Vibration, Data modeling, Chemical analysis, Ionization, Chemistry, Performance modeling, Thermodynamics, Temperature distribution

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The primary purpose of this research is to analyze the impact of different chemical reaction models on the characteristics of NO ultraviolet spectral radiation in the shock layer of hypersonic vehicles. The study is conducted from two main aspects. Firstly, three different non-equilibrium chemical reaction models—Gupta, Park, and the modified Ozawa model—were used to simulate the non-equilibrium flow field in the shock layer of the vehicle. Secondly, we further analyzed the effects of different chemical reaction models on the formation of substances in the shock layer and the characteristics of NO ultraviolet spectral radiation. In this paper, we conducted an in-depth study and analysis using the typical flight case of the BSUV (Bow-shock Ultraviolet) flight experiment, which revealed that the non-equilibrium chemical reaction models in the shock layer significantly influence the concentration and distribution of substances, thereby affecting the ultraviolet spectral radiation. By comparing the computational results with the experimental detection spectra, the Park model showed better agreement with the experimental data, with a weighted error below 10%, outperforming the Gupta chemical reaction model. The Park model exhibits comprehensive performance in the current computational cases.

Proceedings Article | 26 July 2024 Paper

A super-resolution reconstruction method for hypersonic target flow field

Zhou Jun, Bai Lu, Li Yin, Huigang Shi, Jingyu Bai

Proceedings Volume 13189, 131890E (2024) https://doi.org/10.1117/12.3032238

KEYWORDS: Super resolution, Image restoration, Feature extraction, Convolutional neural networks, Deep learning, Data modeling, Data acquisition, Target recognition, Signal to noise ratio, Image quality

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With the rapid advancement of hypersonic flight technology, the high-precision measurement of hypersonic flow field parameters has become an urgent issue. The computational fluid dynamics (CFD) method for obtaining high-resolution flow field data requires high grid quality and involves complex numerical solving processes, leading to significant computational costs. There is a growing need to quickly obtain high-resolution flow field data with less effort. Leveraging the powerful nonlinear fitting capabilities of neural networks, it is possible to perform fine super-resolution reconstruction of low-resolution flow field data in a data-driven manner. In this study, we propose an improved Enhanced Super-resolution Convolutional Neutral Network (ESRCNN) model tailored for hypersonic target flow fields. This enhanced model is applied to the super-resolution reconstruction of low-resolution flow fields of blunt body aircraft targets and compared with interpolation methods and traditional deep learning methods. Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity Index (SSIM) are used as evaluation metrics. The results validate the accuracy and superiority of this model in reconstructing hypersonic target flow fields. This method provides an effective approach for the precise measurement and reconstruction of hypersonic flow fields, thereby contributing to the advancement of hypersonic flight technology.

Proceedings Article | 6 November 2023 Paper

Analysis of scattering characteristics of ablation particles

Ligong Zhang, Lu Bai, Yin Li

Proceedings Volume 12921, 129211J (2023) https://doi.org/10.1117/12.2688440

KEYWORDS: Ablation, Particles, Mie scattering, Lithium

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The study of hypersonic aircraft and their tail flames is an important area of research in the field of aerodynamics. The tail flame of such aircraft is an important characteristic, as it affects the aerodynamic stability of the aircraft and has implications for the safety and efficiency of flight. In order to accurately simulate the tail flame and calculate its spectral radiation characteristics, it is necessary to analyze the scattering characteristics of the ablative particles in detail. This involves studying the changes in optical properties that occur as a result of variations in the proportion of mixed ablation products, specifically B₂O3 and SiO₂, during the early stages of the reaction. The paper under consideration focuses on the analysis of this process, with particular attention given to the properties of the new modified material ZrB2-SiC. The researchers used MIE scattering theory combined with independent scattering approximation to compare and analyze the process. Their findings indicate that the extinction coefficient decreases with the increase of ablation time during this early transition stage, while the difference in scattering image function is not significant. Therefore, it is suggested that the difference of scattering phase function can be ignored in future studies. The phase function of SiO₂ particles is directly taken as the final result. This study is of great significance for the development of more accurate simulation models of flame in the tail of hypersonic aircraft, as it emphasizes the need for a detailed understanding of the scattering properties of ablative particles. By analyzing the optical properties of these particles, we can better understand the situation of tail flame and predict its spectral radiation characteristics more accurately. This information can be used to improve the safety and efficiency of hypersonic aircraft and may have wider applications in the field of aerodynamics.

Proceedings Article | 31 May 2023 Paper

An inversion temperature method based on the relative radiance of the OH spectrum in the ultraviolet band

Danmeng Zhang, Lu Bai, Mengjun Sun, Yin Li

Proceedings Volume 12711, 127110S (2023) https://doi.org/10.1117/12.2684887

KEYWORDS: Vibration, Molecules, Temperature metrology, Ultraviolet radiation, Electronic components, Data modeling

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In non-steady and high-speed flowing high-temperature environments, local thermal non-equilibrium phenomena are widely present. Therefore, if the Boltzmann distribution, which uses a single temperature to describe the energy level distribution of molecules, is adopted, a large error may exist. To solve this problem, a two-temperature / three-temperature model is often used to calculate the spectral radiation characteristics of OH in local thermodynamic non-equilibrium states. In this paper, taking the BSUV-2 aircraft at a flight altitude of 100 km as an example, The OH radiation characteristics in shock waves with a wavelength range of 305nm-315nm were calculated using the two-temperature model. By comparing the relative spectral radiance of experimental spectra and calculated spectra of OH, the optimal calculation range of vibrational temperature was determined to be 2000K-4000K. This method of measuring rotational temperature has significant advantages in low-resolution situations. After determining the rotational temperature, by simulating and calculating the normalized OH spectral radiance corresponding to different vibrational temperatures in the wavelength range of 270nm-340nm, it was found that the maximum intensity peak G1 is not affected by temperature, while the second largest intensity peak G2 has a linear relationship with temperature. Therefore, we can use the ratio of G1 to G2 to invert the range of rotational temperature. This study shows that using a two-temperature thermodynamic non-equilibrium model in local thermodynamic non-equilibrium states can achieve temperature inversion and accurately describe the spectral radiation characteristics of OH molecules, providing an important reference for related research fields.

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