Study On The CO₂ Gas Concentration Monitoring Of Key Techniques Of Aircraft Fire Detection Based On NDIR

Because of the aircraft fire has serious hazard when it’s in flight, put forward the research direction of fire alarm in the early stage of the fire. According to the characteristics of early stage of the fire:the ambient temperature has almost no increase, no visible smoke, no fire, the main products of combustion are carbon monoxide and carbon dioxide gas. gas detector had applied in the fire early stage. Because of the combustion of the fire early stage, and Non-Dispersive Infrared gas detection technology has the most widely been used, the Non-Dispersive Infrared gas fire detection technology had applied in the aircraft fire alarm. The environment temperature of the aircraft is low, and the environment temperature has obvious effect to the detection accuracy of Non-Dispersive Infrared gas detector. This paper put forward key technologies to solve the problem.First aircraft CO2 Non-Dispersive Infrared fire detector structure had special designed, in the inner part of the detector added temperature sensor detector, also installed a heating element, the outer of detector had externally wrapped insulation material to avoid the loss of heat detector. Second the detector had designed temperature compensation model. These two methods can eliminate the influence of environmental temperature on the measurement results.Non-Dispersive Infrared detector output measuring voltage, reference voltage and temperature. According to the experimental data at the time of CO2 concentration is 0 or 1000ml/m3, the difference between reference voltage and measuring voltage, temperature compensation model of CO2 Non-Dispersive Infrared detector had built using polynomial partial least squares method. CO2 gas concentration computational model had established under the condition of the environment calibration temperature is 20℃. According to the model fitting results, the difference between the reference voltage and measuring voltage had been same after temperature compensating, under different temperature conditions. At the conditions of low temperature, room temperature or high temperature, CO2 gas concentration curves had coincided. Furthermore, this paper also presents basic fire CO2 aircraft fire detector alarm algorithm, this algorithm had self adapted to environmental background of CO2 gas concentration, according to the environmental background of CO2 gas concentration change rate and the concentration value, then judging the fire or non fire.