In-situ major und trace element detection of exhaust emissions from combustion engine

This project aims to develop a sensitive laser based optical method the Laser Induced Breakdown Spectroscopy (LIBS) for fast and accurate compositional analyses of exhaust emissions from the Diesel engine personal vehicle. The element composition of the exhaust emissions and particulate matter from the engine combustion process is obtained by means of laser induced plasma optical emission spectroscopy. LIBS technique provides a sensitive and rapid analytical non-destructive measurement without sample pre-treatment in the range of sub- parts per million, depending on the sample composition. Here we propose a state-of-the-art laser analytical method which enables measuring directly in-situ with full stream exhaust emission without the need for dilution or the use of a sampling cell. Current existing commercial or laboratory technique requires modification of exhaust gas flow or it measures only a partial stream, in order to maintain constant measurement conditions. Diluting the exhaust gas can negatively influence low concentration measurements and moreover fast transient emission might be lost and not detected. However fast transient emission peaks from combustion process, form the main fraction of total emissions during standardized engine test cycles. An additional important requirement for fast transient emissions is a high temporal resolution of the measurement. By developing an in-situ full stream LIBS technique it would be possible to systematically study the exhaust emission composition and time evolution of fast transient emission peaks in a very short - nanosecond time-resolved domain. Such a technique will be very beneficial for fast major and minor element detection in pollutant emissions; for transient emission diagnostics and also for dynamic emission modelling; for understanding and optimisation of the combustion process and thereby meeting the future EU directives and regulations for reduction of overall pollutant emission from combustion engine driven vehicles.

Current existing emission standards for diesel-engine driven vehicles specify the maximum allowable values for hydrocarbons, carbon monoxide, nitrogen oxides, Particulate Matter (PM) number and PM size from exhaust emissions. However, these emission standards do not concern any additional compounds or chemical elements contained in PM or in soot emissions formed by in-use Diesel engine vehicles. Nevertheless, chemical elements adsorbed by carbonus particles present significant portion of Diesel Particulate Matter (DPM) or soot emission content. Since PM emissions from combustion vehicles are considered as dominant source of air pollution in urban areas and in the cities with heavy traffic; accurate in-situ technique for on-line / off-line measurement of chemical compound of PM from automotive emissions would be desirable. The aim of this project is to develop a sensitive laser based optical method - the Laser Induced Breakdown Spectroscopy (LIBS) for fast and accurate compositional analyses of exhaust emissions from Diesel engine vehicles. Therefore in this research we spectrochemicaly analyse chemical composition of Particle Matter emissions from in-use Diesel engine passenger vehicles. For that reason, we have extracted DPM from many different vehicles. We have applied high resolution LIBS analytical technique to sensitively analyse chemical elements in different DPM matrices. We find out that PM is composed of major, minor and trace chemical elements. The major compound of PM is not entirely Carbon or Carbon Black (CB/BC) element but further other adsorbed metallic nanoparticles such as Iron, Magnesium, Aluminium, Chromium, Zinc, Calcium, as well as other atomic elements like Hydrogen, Nitrogen and Oxygen. Beside these major elements of DPM there are also minor chemical elements like: Silicon, Nickel, Titan, Potassium, Strontium, Molybdenium and others. Additionally in DPM are further adsorbed atomic trace elements of Barium, Boron, Cobalt, Copper, Phosphorus, Manganese and Platinum. All these chemical elements are forming significant composition of PM from in-use Diesel engine vehicles. To understand composition of different DPM matrices we performed qualitative as well as quantitative LIBS analytical measurements. Additionally we have also used other comparative analytical method such as EDX/XEDS. To obtain quantitative results we performed calibration procedure of LIBS spectral signal. From calibration functions we provide concentrations of major and minor elements in various DPM matrices, as well as limits of detection (LOD) for these elements. Different concentrations of detected elements were measured with respect to the type of complex particulate matter matrices. Further details we provide in our publications. The exact composition of DPM is related to different processes involved during the engine combustion. Due to the complex processes within the combustion the agglomeration of chemical elements in exhaust emissions occurred. These processes depend on engine type, engine size, engine operation conditions, type of fuel, quality of fuel, additives, lubricants and aftertreatment devices.