<p>Modelling combustion engines is an important tool in engine research. Development and modelling of ionization current has potential in developing virtual pressure sensors based on ionization measurements. Previous models has problem when predicting the true relationshipbetween the pressure peak location and ionization peak location, and both too early and too late predictions has been observed. An explanation for these discrepancies are provided and a model where the experimental mismatch has been reduced to less than one CAD is also presented. This is well within the measurement uncertainty.</p>

Modelling combustion engines is an important tool in engine research. Development and modelling of ionization current has potential in developing virtual pressure sensors based on ionization measurements. Previous models has problem when predicting the true relationshipbetween the pressure peak location and ionization peak location, and both too early and too late predictions has been observed. An explanation for these discrepancies are provided and a model where the experimental mismatch has been reduced to less than one CAD is also presented. This is well within the measurement uncertainty.

It is desirable to measure engine performance for several reasons, e.g. when computing the spark advance setting in spark-ignited (SI) engines. There exists two methods, among others, of measuring the performance, such as measuring the pressure and the ionization current. Since the ionization current reflects the pressure, it is interesting to study if it is possible to extract information from the ionization current about the combustion and pressure. Three different algorithms for extracting information from the ionization current are studied. The first algorithm, ion peak, searches the \second peak" in the ionization signal. The second algorithm computes the centroid. In the third algorithm a model of the ionization signal structure is fitted to the ionization signal. The algorithms are tested in four operating conditions. The first algorithm uses the local information around the second peak and is sensitive to noise. The second algorithm uses a larger portion of the ionization signal, which is more stable. It provides promising results for engines with a clear post flame phase. The third algorithm, ion structure analysis, fits an ideal model to the ionization signal. The algorithm provides promising results, but the present implementation requires much computational effort.

Les variations de la composition des gaz naturels nécessitent un system de réglage automatique de la richesse de flamme pour des chaudières domestiques à gaz. Dans ce travail,deux solutions potentielles sont étudiées, à savoir la chimiluminescence de flamme et le courant d’ionisation. Des indicateurs de richesse sont déduits des signaux de chimiluminescence obtenus expérimentalement. L’impact de l’échange de chaleur entre la flamme et le brûleur sur des signaux de chimiluminescence est ensuite étudié. Une analyse est également faite des principaux facteurs pouvant perturber la caractérisation du signal de chimiluminescence. Le courant d’ionisation est ensuite étudié sur une flamme conique pour comprendre l’évolution de son intensité avec la position de sonde et avec les conditions de flamme. Il est montré ensuite que ces évolutions sont corrélées avec le changement de la distance entre la flamme et le brûleur. Enfin, une boucle de contrôle est développée pour démontrer la faisabilité d’un réglage automatique de richesse en exploitant le signal de chimiluminescence. / The variations of natural gas composition call for an automatic equivalence ratio regulation system for domestic gas boilers. Two potential techniques for this purpose are investigated, i.e. the flame chemiluminescence and ionization current. Equivalence ratio indicators are inferred from the chemiluminescence signal based on the experiments. The investigation proceeds by examining effects of the flameburner heat exchange on the chemiluminescence signal. The interference of several disturbing factors for the chemiluminescence signal characterization is also analyzed. The flame ionization current is investigated on a conical flame to understand the evolution of its intensity with the probe position and flame conditions. These changes are then attributed to modifications of the distance between the flame base and the burner rim. Finally a control loop is developed to demonstrate the feasibility of equivalence ratio self-regulation with the chemiluminescence signal.