Mätning av partikelmassa i avgaser från en dieselmotor
This master thesis was a continuation of a previous study in the diesel exhaust characterization, which is part of the academical work embedded in the EMIR-1 project. The main objective of this thesis work was to finish the installation and make the proper modifications of the particulate mass measuring system located in one of the engine test cells at KTH, in order to be able to measure the mass of the particles from the exhaust of diesel engines.This experiment requires a diluted flow sample from the exhaust that should be sent to the device that makes possible the measurement of particle mass, called TEOM. In the first stage of this project, the objective was to study and make the proper modifications in the existing KTH diluter because there were several problems to obtain a constant dilution ratio from it during tests.This modifications were made and it resulted in a great improvement in the maximum inlet and outlet flow that this diluter can handle. Therefore another modification is proposed for controlling the inlet exhaust flow so it will be possible to regulate the dilution ratio and make it constant along a wide range of engine loads and speeds.The second and most important stage was to make particulate mass measurements possible by analyzing the frequency signal from the TEOM device. The idea was to obtain the frequency of oscillation from the tapered element in the TEOM, and therefore with the proper correlations, be able to predict the particulate mass concentration in the exhaust flow from the engine.An electrical problem in the TEOM circuit was detected and corrected, so the signal that carries the frequency from the TEOM can be analyzed properly. The frequency signal can be measured in a time interval with minor disturbances. In that way, it has been found an efficient way to predict the particle mass concentration in the exhaust.Although this method is efficient, there are still some issues yet to be solved. The condensation of water and hydrocarbons inside the pipelines that affects the particulate measurements should be avoided by heating the sample flow. The idea is to get the most diluted and dry flow.As a continuation of the present master thesis, a new thesis work has been initiated. The purpose of this future work is to implement other dilution devices as the rotating disk diluter and also a particle counter, to make it work together with the KTH diluter operating with heated lines, to avoid condensation problems.This investigation shows that the system for measuring particulate mass works appropriately in the range studied. Some ways for improving the sampling system have also been proposed to get even more accurate results in the future research.