Smoke Sensor Research Based On Regional Dehumidification

Smoke sensors play an important role in fire prevention.Photoelectric smoke sensors detect the occurrence of fire and issue alarms based on the intensity of light scattered by smoke particles,and are the current mainstream products.However,the high humidity and temperature variations in the environments of underground coal mines,underground pipe corridors and hydroelectric power plant applications make the sensor extremely susceptible to internal condensation,which often leads to false alarms and distress to normal working life.To address this problem,a method is proposed to use a heating film with positive temperature coefficient characteristics to heat the regional inside the smoke detector to reduce humidity in order to avoid false alarms.The main work of the thesis are as follows:(1)According to the internal structure of the photoelectric smoke sensor,regional heating and humidification system was proposed and designed.Based on the working principle of the photoelectric smoke sensor,the condensation of the photoelectric smoke sensor in high humidity environment was simulated and analyzed by using the COMSOL software,which explained the reasons for the false alarm of the sensor in a high humidity environment.(2)A thin film heating and humidity reduction method based on the positive temperature coefficient characteristic is designed.The fuzzy PID control is applied to the heating and humidification process of resistance wire,and the simulation model of fuzzy PID and temperature control system is established.The results show that the fuzzy PID control is better than the control effect of conventional PID in terms of error accuracy,response speed and steady-state effect.Based on Mie scattering theory and discrete dipole approximation theory,the optical properties of spherical water droplets and spherical wood cathodic combustion fire smoke particles are analyzed computationally.(3)The software and hardware design of the regional heating and dehumidification system was completed.The hardware side uses STC12 microcontroller as the main control chip,and designs the circuit with temperature acquisition,humidity acquisition and film heating temperature control function based on positive temperature coefficient characteristics.The software side designed the temperature acquisition subroutine,humidity acquisition subroutine,AD conversion,digital filtering and other modules;the software programming of the control algorithm was realized.(4)The sample machine was developed and debugged and performance tested.The results show that when working in a high humidity environment,the photoelectric smoke sensor with area heating and humidity reduction system can automatically start heating according to the humidity condition,and the developed control system effectively reduces the internal relative humidity by about 15% and the false alarm rate by about 80.25%.After heating,condensation will not occur in the photoelectric smoke sensor,so as to effectively avoid false alarm in high humidity environment.Compared with the traditional photoelectric smoke sensor,the reliability of smoke fire detection is greatly improved.The proposed thin film heating and dehumidification method based on the positive temperature coefficient characteristic and the developed regional heating and dehumidification system improve the stability of the photoelectric smoke sensor,can effectively avoid the false alarm caused by high humidity,is easy to upgrade the oldstyle photoelectric sensor,and has great application prospects in coal mines,underground pipelines and hydropower stations.