Design And Application Of Measurement System For Droplet Quantity Based On Solution Conductivity Principle

The droplet quantity(droplet flow rate and deposition)is important characteristic quantity in the spray field and its accurate measurement are basis to research spray regulation and evaluate sprayer operation performance.The commonly used method to measure droplet quantity is tracer method with paper card.As it is convenient to arrange the paper card,this method has been widely used in the spray field while it still has some shortages:many steps are needed to finish the measurement process,it is time consuming,and one paper card cannot be used for multi measurements.As for other measurement systems to measure droplet quantity based on capacitance and resistance principle,despite that it is more quickly to obtain results,the remaining droplets on the sensor surface should be cleaned after each measurement,and again these types of methods cannot be used for multi continuous measurements,which reduces efficiency.If the collecting droplet quantities are large,the droplets will fall down from the surface of paper cards or sensors,and this will reduce measurement precision.Therefore,it is necessary to develop a measurement system which can measure droplet quantity of different dirctions quickly,accurately and continuously.In this article,a measurement system was developed and its application researches were conducted.The main contents were as follows:The relationship between the solution conductivity and droplet quantity was researched and the test results showed that there was a good correlation between them in dilute solution with a determination coefficient of 0.99.The relative model was constructed with SPSS 20.0 software to provide theoretical basis for the development of measurement system.Combining the theories of solution electric conduction,diffusion and droplet collision with tests,the parameters of the system were determined.The measurement system consisted of hardware(the measurement device and the positioning platform)and software system.The measurement device consisted of droplet collecting box,solution conductivity meter,thermometer,relay control panel,current transmission module and PC.The solution conductivity meter measured the solution conductivity and sent the analog current signal corresponding to the measured solution conductivity to current transmission module;the model transmitted the analog current signal into digital signal and sent it to the PC;the PC displayed the droplet quantity data.The positioning platform was mainly developed to position the measurement device in the spatial space quickly.For the software system,it consisted of the design of key program to achieve main functions and the design of interface to make experimental operations more conveniently and data regulation analysis more clear.The error analysis theory was used to validate the precision of the measurement system.The developed system and the tracer method with paper cards were compared with each other indoors,and the precision of measurement system was primitively validated by comparing the relative errors of these two methods.The results showed that the relative error was 6.08%for horizontal droplet quantity measurement and 7.75%for vertical droplet quantity measurement.Besides,the results of the measurement system were compared with those of active droplet collector,and by this way,the systematic error of the measurement system was analyzed with hypothesis testing principle.The results showed that the collection and recovery rate were 84.31%and 91.47%respectively for measurement on vertical plane;the collection and recovery rate were 86.18%and 94.68%respectively for measurement on horizontal plane.After that,the droplet collection and recovery rate of the measurement system were researched in different spray parameters(outlet air velocity,droplet size,measurement direction),designing parameters(inclined angle of droplet intercepting plate)and solution evaporation to validate the measurement stability.Finally,methods on how to improve measurement precision were analyzed.In the second part,application researches of the measurement system were conducted.The contents were:In chapter four,the influence of number and interval of nozzles along the vertical height on the droplet quantity distribution was researched by using the measurement system,which could provide basis and methods for the designing of multi air ducts sprayer.In chapter five,by using the measurement system,the influence of foliage density,cannon sprayer outlet air velocity and penetration distance on the droplet penetration,deposition and drift characteristics in pear tree canopy were researched.The suitable outlet air velocity was determined based on experimental results and the travelling speed of sprayer was estimated with air flow displacement principle and droplet deposition requirement in tree canopy,which could provide reference for the sprayer setting for trees canopy of different foliage densities.In chapter six,the pesticide application experiments were conducted on graperfruit tree with the 3WZ air-assisted sprayer.The measurement system and the paper card method were used to measure the droplet deposition on leaves,the deposition on the ground and drift in the air.The measurement results were compared with each other to further validate the measurement system;besides,the influence of spray parameters(fan speed and travelling speed)on droplet deposition on leaves,deposition on the ground and drift in the air was researched to provide basis for parameter settings in pesticide application.In chapter seven,the measurement system was used to research the droplet penetration model of different types of tree canopies and sprayers.Large amounts of data were obtained with the measurement system,which provided data resources for the determination of model fitting coefficients and validation of the model prediction precision.Then,the constructed penetration model was employed to predict the droplet distribution in the tree canopy,analyze the uniform of droplet distribution in the tree canopy and optimize outlet air velocity of sprayer.Overall,the measurement system could be used in many fields including droplet flow rate and deposition in different directions,droplet deposition on leaves,droplet penetration rate in the tree canopy.It could also be used to research the spray regulation of sprayer in field.These showed that the measurement had a good practicability and provided new ideas and methods to research droplet quantity distribution with experimental methods.