Effects of fuel properties, injector conditions and impingement on the sprays of direct injection engines

Abstract

The concept of gasoline direct injection engines is at the forefront of modern research. Two major concerns with the design are the incomplete evaporation of the injected fuel that leads to increased engine-out emissions and the process of injector fouling caused by the direct exposure of the injector to the flame. The latter also reduces the lifetime of this component and also increases emissions at the same time. These are critical issues for OEMs as emissions legislations around the world demand increasingly stricter thresholds. The research presented is split into two separate parts, to tackle both concerns. First, a series of fuel blends and operating conditions and their effect towards spray shape, droplet size and velocity as well as wall wetting will be investigated in a dedicated injection chamber. In order to quantify the amount of fuel that forms a liquid deposit on the surface a novel measurement technique is presented. The data gathered in these measurements is then used to show trends between the blends investigated and to give suggestions for potential improvements of future engine designs and modified engine operating conditions to reduce the amount of particulate emissions. In the second part of the research a series of injectors that were previously fouled are investigated. The fouling caused a significant increase of particulate emissions in test engines and the focus here is to provide possible explanations for this drift. Additionally, some of the injectors were treated with a detergent fuel which reverted the change in emissions. A comparison of these injectors shall provide information about potential applications of such blends and how they would benefit the longevity of modern engines.