Influence of Urea Concentration on Refractive Index of AdBlue fluid Evaluated by Regression Analysis

Abstract

The article deals with the influence urea concentration in the AdBlue fluid on the refractive index. The AdBlue fluid is an aqueous solution of urea and demineralized water. It is used as a reducing agent for SCR (Selective Catalytic Reduction) system. Due to temperature fluctuation of AdBlue during the measurement of refractive index, the multi-dimensional linear regression had to be used to determine the effect of the two factors – concentration and temperature. This article describes in detail the individual steps of the regression model construction done using the so-called regression triplet. The task of this method was to create a regression model which describes the influence urea concentration and small changes in temperature on refractive index of AdBlue fluid. As the results of the multi-dimensional regression analysis show, the temperature factor is statistically insignificant because of small range of temperature fluctuation during measurement, and thus only the urea concentration in the fluid had the major effect on the refractive index.

Keywords

• refractive index
• multi-dimensional regression analysis
• regression triplet
• regression model
• method of least squares