Theory And Experimental Study On The Smoke Total Obscuring Power

This research derived partly from the co-operation between Qiqihaer JianHua Machinery Research Institute and the key project of National Natural Science Foundation(Serial Number:50336010). Its intention is to study the obscuring effect and effectual obscurant area following the formation of the smoke and to develop the examining system of Total Obscuring Power. Therefore it is possible to distinguish objects from the smoke obscuring condition and provide simulation technology, theory model and experimental platform for electronic interference.The smoke interference is a most widely-used passive photoelectric interference method. It discharges lots of aerosol particles in the air in order to change the atmospheric transmissible characteristic of ray radiation and to protect the object. Because the research of mechanism in the light elimination of the smoke is the basis of the development of the smoke technology, the western countries, especially the USA, attach importance to the basic theory research while developing smoke equipments. The research of modern smoke technology in our country got off to a late start, and the research is mainly based on large amounts of experiments. So the probe on mechanism in the light elimination of the smoke is very little. For the lack of basic research, the backwardness of the theory research, the choices of the smoke materials need theoretical guidance. Formulas were always determined by experiments and experiences, and this situation, to some extent, restricted the development of smoke technology in our country.The TOP(Total Obscuring Power) value of the smoke issuing reagent is one characteristic parameter which shows the smoke obscuring effect on human vision by the smoke in the domain of smoke technology at home and abroad. The factors which affect smoke TOP are complicated. The humidity and temperature of the testing surroundings, testing time, subsiding velocity of the smoke and other factors will affect the testing results of TOP value of the smoke. Based on the measurement and evaluation of TOP value, and with analysis to the development of the TOP value testing system of visible light, this thesis deeply elaborates TOP testing theory, TOP testing method, light scattering theory, testing model, uncertainty in the testing process and other contents which involved in the system. Some finished research works are listed below:1. Research of the smoke obscuring characteristics. The obscuring effect of smoke was analyzed in details to human eyes, low light level imagery system, passive IR imagery system and imagery guided system. And some models were compared and analyzed, such as the model of penetrating rate, the model of absorbing coefficient, and the calculating model of total obscuring power of the smoke.2. Testing system design of TOP of the smoke. A TOP testing system of the smoke has been developed based on the irradiance testing method and vision contrasting scope of human eyes. Under the condition of 26℃and 60% relative humidity, a test of TOP with phosphoric smoke showed that the error was less than 4% compared to the empirical value.3. Testing results analysis of TOP of visible light through smoke on the condition of different particle size distribution. The different composition of smoke, relative humidity and temperature, and formation time and state of the smoke had an effect on the particle size distribution and on the effective light-absorption area and scattering area. In view of different models of particle size distribution and calculating results, the model was established based on the Mie theory, the responding function of TOP to different particle size distribution was also provided. Therefore the direction of the testing system and the reliability of the testing results were improved.4. Expanding application and parameter test of TOP mathematical model to three IR wave band,1-3μm,3-5μm,8-12μm and laser 10.6μm. Considering the development of IR-proof smoke technology and the limitation of this testing system, it is possible to expand IR wave band and do some experimental research on TOP testing system of visible light through smoke under the condition that lots of researchers are positively exploring the penetration capacity of IR through smoke.5. Calculating method research on the edge of effective area of the smoke image. By analyzing the radioactive characteristic of the object and the background, the SNR of received IR image was calculated, and then the effective obscuring area of the smoke was also calculated by the method of morphologic ecology. Finally, the simulation experiment was done based on the analysis results mentioned above.This thesis provides theoretic basis which are important for analyzing the smoke formula and developing effective smoke interference material. On the basis of the perfect theory model and the improved system precision, the unified smoke obscuring power was improved and the test standard of the obscuring power of smoke issuing reagent may be established.