Investigation of processes in the WLTC test of a passenger car with a diesel engine

The test results and their analysis was discussed in this article. The tests were carried out in accordance with the WLTP (Worldwide Light Duty Test Procedure), on a passenger car with a compression ignition engine. The analysis was conducted doe the following variables: vehicle speed, exhaust emission rate and fuel consumption volumetric rate. The subject of the research are exhaust emission components that are harmful to the health of living organisms: carbon monoxide, hydrocarbons and nitrogen oxides, as well as greenhouse gases. The research results have shown a very large range of values for carbon monoxide, organic compounds and nitrogen oxides emission rate characteristics. The average distance-specific emissions values of carbon monoxide, organic compounds and nitrogen oxides were very small and were in line with the Euro 6 requirements within a large margin. Correlation studies of the measured variables were conducted - between vehicle speed and exhaust emission rate as well as volumetric fuel consumption rates, and between exhaust emission rates and volumetric fuel consumption rates. The correlation studies have shown that the highest coefficient of determination in relation to vehicle speed was found for volumetric fuel consumption and carbon dioxide emission rate, and the weakest correlation for carbon monoxide emission rate and nitrogen oxides emission rate. The correlation between the rate of volumetric fuel consumption and carbon dioxide emission, as well as for hydrocarbon emission and methane emission rates, was found to be the strongest. The carbon monoxide emission rate was the least correlated with all the other measured variables. Dimensionless statistical characteristics of the measured variables were determined, such as: extreme values, range, mean value, median, standard deviation, kurtosis, skewness and coefficient of variation. For all of them, the mean value was much greater than the median, and the standard deviation was greater still, than both of those values. The numerical distributions for the values of exhaust emission rate and volumetric fuel consumption turned out to be leptokurtic and have right-sided asymmetry. The coefficient of variation analysis made it possible to assess that the most dynamic properties could be observed in organic compounds emission rate, followed by carbon monoxide and nitrogen oxides emission rates, and finally - the vehicle speed. Histograms of the examined processes were determined. The vehicle speed histogram was characterized by relative uniformity apart from the dominance of the idle speed. Histograms of exhaust emission rate variables were most frequently dominated by small values. The zero values occurred less frequently for the fuel consumption volumetric rate histogram. Based on the conducted research and the obtained data, a set of conclusions was drawn.