| With the development of the economy,the odorous gas pollution in the atmosphere has attracted people’s attention.Traditional malodorous gas monitoring mainly relies on the manual scenting method.The method which has low precision and subjective influence,and the electronic nose system lies in the detection of malodorous gas.The shape and structure of the reaction chamber in the detection system have a very substantial impact on the accuracy and repeatability of the system.However,most of the reaction chambers of the current malodor detection system are designed base on experience,and the chemical reaction inside the gas chamber is not fully considered,resulting in poor detection of the electronic nose system,which limits the application in the detection of malodor.This thesis relies on the national major instrument special "complex odor detection",in response to the deficiencies of the malodorous gas detection system.In this thesis a parallel structure of the reaction chamber is designed,has been used in the malodor detection electronic nose system,improving the system repeatability and accuracy.In view of the problems in the repeatability and accuracy of the current malodor detection system,the following viewpoints are proposed: the current serial air chamber structure is affected by factors such as temperature in the gas chamber,reactant consumption,and gas leakage,influencing the accuracy of the electronic nose system.In this thesis,the computational fluid dynamics technique is used to simulate the chemical reaction process inside the serial gas chamber.The data shows that the reaction of the front-end sensor in the current serial reaction chamber causes the temperature in the gas path to rise by 0.2 °C while consuming 10% of the gas to be tested,and generating 10% of sulfur dioxide,which interferes with the response of the latter sensor.The idea that the serial air chamber affects the repeatability and accuracy of the malodorous electronic nose system is proved.Built on the simulation results of the original air chamber,a set of parallel,sensor positions are completely symmetrical,and a good interchangeable reaction chamber structure is obtained.The numerical simulation of the newly designed reaction chamber shows that the newly designed parallel reaction chamber can avoid the problems of temperature,reactant consumption and new gas generation in the innovative gas chamber.With a parallel reaction chamber core,design circuit and embedded program,a set of malodor detection electronic nose systems were designed for experimental verification.The experiment uses methyl sulfide gas as the gas to be the subject,and the response curve trend is the same as the simulation result.The relative standard deviation of the response values.In the replicate experiments were 0.5%.The odor detection was based on the parallel gas chamber was used to calibrate the methyl sulfide gas.The data showed that the correlation coefficient of the linear fitting of the PID sensor and the TGS2600 sensor is above 0.92,and the correlation coefficient of the nonlinear fitting of the TGS2602 is above0.94.The reaction chamber designed based on CFD technology can avoid the interaction between sensors and increase the accuracy and repeatability of the malodorous electronic nose system. |
