Study On Detecting Method And Technology Of Fluid Compositions Based On Permittivity

Permittivity can well reflect the performance of dielectric materials. Permittivitymeasuring techniques have been developed mainly for solid materials. Most existingpermittivity sensors provide only one piece of information–apparent EC or dielectricconstant at a given frequency, only measuring single or a few characteristic parameters withina particular range, and are unable to fully uederstand the frequency characteristics of thedielectric parameters of the test sample. Thus, these instruments are incapable ofdistinguishing multiple ingredients that influence the permittivity in dielectric materials.In order to apply permittivity sensors to measurement of composition and properties ofliquid and gas dielectric materials, and to provide a new method and technique for real-timedetection of water and air pollutants, in this paper, the detecting method and technology offluid compositions based on permittivity have been studied to detect multiple properties offluid dielectric simultaneously and identify a variety of compositions on the basis ofanalyzing the properties of liquids and gases dielectric. And through a large number ofexperimental research and analysis, the frequency-response pattern and detecting models ofdifferent compositions in fluid have been obtained.The main contents and conclusions in this study are including as follows:1. On the basis of analysis detection technology of soil dielectric properties and materialproperties of liquid and gas dielectric, the principle and the detection performance of the newfrequency response permittivity detection system based on microcontroller developed by theInstrumentation and Control Laboratory of Biological and Agricultural EngineeringDepartment of Kansas State University used to detect multiple properties of fluid dielectricsimultaneously and identify a variety of compositions have been researched and analized. Thesensor probes have been made selecting different materials according to the characteristics ofthe detection medium and testing need. According to the needs in test and research, thepositioning plate has been designed and made.The main factors of the detection signal havebeen analyzed so as to achieve optimum control on these factors in test study. The detectionaccuracy of the system was analyzed by contast.2. According to functional requirements of detection hardware system, and differentneed in test and research, the corresponding fluid permittivity detection software system and controngling programs have been designed reference to the Soil Detecting Softwaredeveloped by K.H. Lee of Biological and Agricultural Engineering Department of KansasState University. Programs for measurement system controlling and data acquisition werewritten and compiled using C language. The programs were edited and debugged withsoftware developing tool Tasking C166/ST10, and were downloaded to kitCON167microcontroller for running through EDE and Flash Tools16W. Functions to producesinusoidal voltage signals with different number and different frequencies, different waitingtime of signal, colletting data continuously and automatically under different time intervals etal. have been achieved. The detection system has been ensured for a good run. Based on thefeature of frequency response data with large amount of informations, the data processingmethods of partial least squares (PLS) and stepwise regression have been studied. Dataprocessing program has been designed using Matlab software, and the accuracy and efficiencyof data processing have been improved.3．In connection with the requirements of detection the fuel mixing ratio and quality fastand accurately for exerting the best power performance and exhaust emission control to blendfuel engine of biodiesel and diesel, a new method to detect the mixing ratio of diesel/biodiesel blends rapid and accurately based on the dielectric properties was proposed. Thepermittivity detection system developed for fluid dielectric materials was used to study on therelationship of blend ratio and frequency-response characteristics of biodiesel and dieselblends through experiment. The frequency-response pattern of biodiesel blend fuel has beenanalyzed. With PLS and stepwise regressions, the blend ratio detecting models have beenconstructed. The results show that correlation of mixing ratio and frequency-response are veryhigh. R-square values are greater than0.99while RMSE are less than0.9%for both trainingand validation of PLS regression models. The use of stepwise regression method significantlyreduces the amount of data needed to measure the bend ratio, also have a high accuracy.Using the permittivity and frequency response method to measure the mixing ratio ofbiodiesel blend can get high precision and can meet the requirement of fast detecting.4. In connection with the requirements of detection the fuel mixing ratio and quality fast,accurately and conveniently for adjusting the engine's optimal ignition time and exhaustemission control to engine of Hybrid vehicle, the permittivity detection system developed forfluid dielectric materials was used to study on the relationship between mixing ratio, watercontent and dielectric characteristics of ethanol/gasoline blends through experiment. Thefrequency-response pattern of ethanol/gasoline blend fuel has been analyzed. With PLS andstepwise regressions, the mixing ratio detecting models have been constructed. R-square values are greater than0.99while RMSE are less than1.2%for both training and validationof PLS regression models.Study results show that using the dielectric property and frequencyresponse method to measure the mixing ratio of biogasoline can get high precision and canmeet the requirement of fast detecting, which laid the foundation for real-time and accuratemeasurement of biogasoline mixing ratio.5. In connection with the urgent needs for real-time monitoring technology to waterquality with high efficiency and low cost so as to protect environmental safety and humanhealthy, the permittivity detection system developed for fluid dielectric materials was used tostudy on the relationship between concentration of different ion or cation in potassium,nitratesalt solutions and dielectric properties by large number of experiments. Thefrequency-response pattern of different ion or cation has been analyzed. Study was done onthe rapid and accurate method of concentration detection of potassium salt, nitrates, herbicideresidual and other pollutants in water based on the dielectric properties. With PLS regression,the concentration prediction models of various ion or cation in potassium salt and nitratesolutions have been established. Based on a principal component analysis, characteristicfrequencies for potassium cation and nitrate ion were identified from the frequency-responsepatterns. The new prediction models at the characteristic frequencies for concentration ofpotassium cation and nitrate ion in water have been established. The results showed that eachion or cation has its unique frequency-response pattern; frequency-response properties ofdifferent types of salt solution are significant difference at the low frequency region.Prediction accuracy of PLS regression models for potassium cation concentration and nitrateion concentration in mixed solution with low concentration are all very high. Principalcomponent analysis and identification of the characteristic frequencies reduce the amount ofdata significantly, and also have a high accuracy. The study laid the foundation for real-timemonitoring technology of water pollutants with high efficiency and low cost.6. In connection with the issues of long sampling time, tedious pre-processing step,volatile substances for analysis to be easily lost, and the high cost of measurement and lack ofcontinuous measurement capacity which present in traditional air pollutants measurementtechniques, the permittivity detection system developed for fluid dielectric materials was usedto make a preliminary study and probing on detection of several types of air pollutants such asparticulate air pollutants, diesel exhaust, and volatile organic compounds. Preliminaryexperimental results show that air samples changes in the patterns of frequency response,mainly in the middle and high frequency region. In most of the air samples, the role ofdielectric capacitance dominates, and the conductivity of the air is very small. 7. Advantages and disadvantages of the frequency response sensor were analyzed.Further studies to improve the sensor performance were recommended.