The Design And Application Of A High-Precis Ion Detection System For The Concentration Of Urea Solution

With the continuous improvement of automobile exhaust emission standards,it is imperative to upgrade the post-treatment of automobile exhaust emissions.At present,the selective catalytic reduction route is adopted in the post-treatment of diesel vehicle exhaust in China,and the nitrogen oxides in the exhaust are revivified by 32.5% concentration of urea solution.The concentration of urea solution has a very important impact on the treatment efficiency.Therefore,the online high-precision detection of the concentration of urea solution is of great significance for the improvement of the treatment efficiency of the exhaust post-treatment system.Under the circumstances,this paper developed a set of vehicle urea solution concentration detection system based on the principle of ultrasonic detection,and achieved the online detection and real-time feedback of the temperature,liquid level and concentration information of the solution in the diesel urea solution box.Based on the principle that ultrasonic waves travel in different concentrations of solutions with different speeds,the relationship between ultrasonic sound velocity and the concentration and the temperature of urea solution were studied in detail,and this principle was employed to achieve online and real-time detection of solution concentration.Considering the non-stationary errors of the traditional ultrasonic time-difference method,the entropy weight method was used to preprocess the test data,then the processed data was fitted and sampled by cubic spline function to reduc non-stationary errors,the accurate concentration model was finally obtained by least square surface method with the surface fitting of the sampled data.Compared with traditional time-difference method and direct surface fitting method,our method can achieve higher accuracy for the detection of solution concentration.Moreover,the system design of hardware platform and the work of software development were completed in this thesis to achieve various functional requirements.The design system has the advantages of low hardware cost,high detection accuracy,convenient detection,online measurement and so on,and has a wide application prospect in the field of liquid concentration detection.