Search Results (2)

To determine the timing of inflammation in gas and gasoline combustion engines, the point of 10% mass fraction conversion of fuel (MFB10) is commonly used. The MFB10 can be determined from the heating curve, which in turn is calculated from the in-cylinder pressure curve. However, the cylinder pressure is an indirect parameter with regard to inflammation, as it is the result of the combustion that follows the inflammation. An attempt is made to derive a new, direct parameter of inflammation based on optical measurements in order to detect inflammation more rapidly and accurately. The background-oriented Schlieren technique (BOS) in combination with high-magnification optics and a high-speed camera is used to detect local density changes coming from the particle wave around the ignition kernel of a hydrogen combustion inside a combustion chamber. Via BOS and regular high-magnification high-speed imaging, the influence of ignition coil dwell time and in-cylinder pressure on the spark phases and the inflammation itself are evaluated. As a potential direct parameter for inflammation, the size of the particle wave resulting from the expanding ignition kernel is evaluated. It was found that a higher coil energy supports a faster propagation of the particle wave at ambient pressure. At higher pressures, general combustion effects override the effect of the influence of the coil energy on the propagation speed of the particle wave. In addition, the presence of successful inflammation was found to influence the spark phases. A directly measurable parameter for ignition could be found at a basic level, which will serve as a starting point for further detailed investigations. Full article

The production of CO₂-neutral fuels is a key technology to achieve the European Union’s targets of greenhouse gas reduction in the transport sector. For a straightforward application such as drop-in fuel, regenerative gasoline must meet emission requirements without causing significant changes in engine parameters. The objective of this work was to demonstrate the emission reduction potential of fuel from the bioliq^® plant by reducing the content of heavy aromatics in the product refinement. For three blends with varying contents of bioliq^® fuel, the spray behavior was studied in a pressurized chamber and the particulate and hydrocarbon emissions were investigated using a single-cylinder research engine. With increasing bioliq^® fuel content, atomization was degraded by lower flash boiling at low pressure. This effect vanished at higher chamber pressures. Measurements of particulate and hydrocarbon emissions showed significant improvements of 50% to 100% and 10%, respectively, compared to previously investigated bioliq^® fuel fractions from 2017. The formation of particulate emissions is virtually unaffected by the blending of bioliq^® fuel, due to the absence of heavy aromatics in the refined bioliq^® product. Hydrocarbon emissions increased by 20% with higher bioliq^® fuel content and late injection timings due to inferior mixture formation as a result of slightly reduced atomization. However, near the optimum injection timing, the hydrocarbon emissions are independent of the bioliq^® fuel admixture. Full article