Research On Propagation Characteristics Of Terahertz Waves In Fire Smoke Environment

Fire environment imaging technology has become one of the important technologies for fire detection.Existing imaging detection equipment is greatly affected by smoke in a low-visibility fire environment,which makes imaging difficult in a fire environment.Terahertz waves are electromagnetic waves located between the infrared and microwave bands,taking into account both transmittance and resolution.If terahertz wave technology is applied to fire environment imaging detection,it will have excellent detection characteristics.However,the terahertz wave will be affected by the fire smoke environment.Therefore,this paper studies the transmission characteristics of the terahertz wave in the fire smoke environment,and provides a theoretical basis for the application of the terahertz wave technology to the fire environment detection.The main research contents and results are as follows:(1)Based on the unique fractal aggregate structure of the smoke particles,the optical properties of the smoke particles were analyzed,and the transmission mechanism of the terahertz wave was studied based on the optical characteristics of the smoke environment in the fire field.The transmission of the terahertz wave in the smoke environment was analyzed by the radiation transfer equation.transformation.Two numerical simulation methods are proposed.The discrete dipole approximation method is used to simulate and solve the attenuation characteristics of smoke particles to terahertz waves,and the discrete ordinate method is used to simulate and solve the transmission characteristics of terahertz waves in the flue gas environment.(2)Taking the particle size of smoke particles and the incident wavelength of terahertz as variables,based on the unique fractal aggregate structure of smoke particles,the attenuation law and transmission characteristics of terahertz waves in the smoke environment are studied through theoretical analysis and numerical simulation.The transmission attenuation law of terahertz waves under different smoke particle structure parameters,particle size distribution and smoke concentration simulated and analyzed.The radiation transfer equation was used as the theoretical model to analyze the transmission characteristics of terahertz waves under different working conditions.The results show that,transmittance of terahertz waves in the common fire smoke environment is above 80%.(3)Considering the influence factors of the fire smoke environment on the transmission of terahertz waves,different smoke experimental environments were designed to conduct experimental research on the transmission characteristics of terahertz waves.A small-sized experimental box was built on the optical platform to simulate a uniform smoke environment,and the smoke was built.The corridor simulates a flue gas environment with a non-uniform flow field.Taking different experimental fuel and flue gas concentrations as control quantities,taking into account the influence of different sampling point heights,combustion times,and flame and temperature,an experimental study on the transmission characteristics of terahertz waves was carried out to analyze the changes of terahertz wave transmission under different working conditions.The established terahertz wave transmission model is verified.