摘要
试验研究是掌握舰船排气烟羽红外辐射特征的主要手段,对排气系统设计和优化具有重要作用。实际试验系统往往对排气系统进行缩放以降低试验成本,因而,研究缩比前后排气系统的红外辐射特征相似性将为试验结果运用提供重要支撑。文中针对3~5μm波段下烟羽红外辐射特征相似性开展研究。首先以一维介质为对象,分析得出在温度和介质浓度分布一致、光学厚度相等条件下,缩比前后辐射系统具有很好红外辐射相似性。同时,分析了光学厚度变化时,缩比前后系统辐射相似性变化特点。接着,以实际烟囱排气为对象开展不同缩比条件下红外辐射特征相似性研究。结果表明,在满足烟气温度场和流场相似、同时介质光学厚度相等条件下,缩比前后系统具有很好的辐射相似性,烟气区域面积积分红外辐射强度与缩比比例平方成正比,不同缩比比例下最大偏差为2.15%。当缩比试验过程中,气体摩尔分数难以等比例调整,介质光学厚度有明显变化条件下,缩比前后系统红外辐射强度最大偏差10.47%,缩比试验结果对原尺寸红外辐射特征预测仍有较好的指导意义。
Objective With the continuous advancement of infrared thermal imaging detection and guidance technologies,research on infrared radiation has become pivotal for mitigating threats to ships.The exhaust plume is one of the main sources of infrared radiation,the suppression of the plume is critical for the overall infrared stealth characteristic of ships.Experimental investigations serve as the principal means for understanding the infrared radiative characteristics of ship exhaust plumes and are important for the design and optimization of exhaust systems.In practical applications,experimental systems are often scaled down to reduce testing costs.Consequently,examining the similarity in infrared radiative characteristics between scaled and full-scale systems provides a foundation for applying experimental results.Existing studies mainly consider the similarity of temperature and concentration fields as prerequisites for achieving radiative similarity.However,whether optical thickness should remain consistent before and after scaling remains unresolved.In practical scaled model experiments,when the exhaust gas composition is consistent across scaled and full-scale systems,variations in geometric dimensions often result in changes to optical thickness.Exploring the impact of optical thickness on radiative similarity is therefore of significant academic and practical importance for validating and applying the results of scaled model experiments.Methods Radiative similarity is investigated firstly in one-dimensional media.The analytical solution for radiative intensity is derived through solving the radiative transfer equation.Single-layer media with only high temperature gas and multi-layer media containing high temperature and surrounding low temperature gases are considered.Similarity conditions including consistent temperature and medium concentration distribution as well as equal optical thickness are examined.In order to check the applicability of the radiative similarity rules in a practical system,the plume of a ship exhaust system is investigated.Computational fluid daynamic are conducted to obtain the temperature field and the molar fraction fields of CO_(2) and H_(2)O in the plume.The reverse Monte Carlo method is then employed to compute the radiative intensity of the exhaust system.This approach enables a detailed analysis of the infrared radiative similarity of different scaled models under actual exhaust conditions.Results and Discussions For one-dimensional media,under the condition of the same temperature and gas concentration distribution as well as equal optical thickness,the maximum deviation between scaled and full-scale systems is 1.37%,regardless of whether the medium consists of a single layer or multiple layers of gas.When the gas concentration remains unchanged(resulting in significant variations in optical thickness),the infrared radiative intensity exhibits some differences between scaled and full-scale systems.For two-layer and three-layer media where there is a low temperature surrounding media,the deviation is less than 10%.The spectral distributions are illustrated in Fig.2 and Fig.3,while the results of the spectrally integrated radiative intensity are summarized in Tab.1.For the plume of a ship exhaust system,the infrared images are shown in Fig.9.Radiative intensity results in Tab.3 show that if the optical thickness is the same for scaled and full-scale systems,the biggest deviation is 2.15%.If the Mole fractions of the gases keep unchanged(with optical thickness changed),the biggest deviation is 10.47%.Conclusions Under the conditions of consistent temperature distribution and similar flow fields as well as the same optical thickness,the scaled and full-scale exhaust systems exhibit high similarity in their infrared radiation characteristics.The integrated radiative intensity of the exhaust plume area is proportional to the square of the scaling ratio.When the scaled and full-scale systems satisfy similar temperature and flow fields but maintain a constant Mole fraction of the gas medium(resulting in changes in optical thickness),deviations in infrared radiation intensity are observed.Nevertheless,the results from the scaled model remain valuable for predicting the infrared radiation characteristics of the full-scale system.In scaled experiments of exhaust system,ensuring similar temperature and flow fields is crucial for maintaining radiation similarity.Although changes in optical thickness introduce some impact on radiative similarity,the deviations are relatively small and do not undermine the predictive value of the scaled model results.
作者
刘志凌
杨斌
李智伟
王振
安一峰
黄志锋
LIU Zhiling;YANG Bin;LI Zhiwei;WANG Zhen;AN Yifeng;HUANG Zhifeng(School of Power and Mechanical Engineering,Wuhan University,Wuhan 430072,China;China Ship Development and Design Center,Wuhan 430064,China)
出处
《红外与激光工程》
北大核心
2025年第6期71-79,共9页
Infrared and Laser Engineering
基金
国家自然科学基金项目(52476086)。
关键词
舰船排气烟羽
缩比模型
辐射特征
辐射相似
ship exhaust plume
scaled model
radiative characteristics
radiative similarity
