Search Results

In DISI engines spray distribution and atomization directly influence mixture formation, the quality of combustion and the resulting emissions. Constant Volume Chambers (CVC) are commonly used to characterize sprays of gasoline injectors. The CVCs provide good optical access but the flow condition of the engine cannot be reproduced. Optically accessible engines in contrast deliver realistic flow conditions but have restricted optical access. In former investigations we compared the spray propagation of different injectors in constant volume chambers and in optical accessible engines. These results showed a clear difference of the spray propagation in the CVC and the engine, especially at high charge motion conditions in the engine. To find an appropriate way to investigate the impact of different charge motion a flow channel was built with adjustable crossflow velocities from 5-50 m/s. The spray propagation during the injection process was measured with high-speed shadowgraphy.

Jet-to-jet interaction has a strong influence on the targeting and spray behavior of injection nozzles for DISI engines. In the superheated flashboiling regime especially, the spray shape and properties can change drastically due to interaction between spray jets. In this work, two setups are shown to investigate this effect, using shadowgraphy, phase doppler anemometry (PDA) and laser-induced fluorescence (LIF). The influence of spray properties and ambient conditions can be shown by comparing a commonly used multi-hole injector with a colliding jet atomization concept with well-known and significantly differing spray properties.

Spray- and flame-wall interactions were investigated in a combustion chamber with diesel engine conditions. Several techniques were used to perform time and spatially resolved measurements of the liquid fuel phase, the premixed and diffusion-controlled combustion close to a wall. Different wall and gas temperature variations were investigated. It was found that low temperature variations of 25K have a significant impact on the combustion process: The lower the gas temperatures, the more liquid fuel and larger vortex structures arise. Also, the ignition delay is elongated. Consequently, the premixing period is longer, which can lead to the complete disappearance of sooty combustion. The colder the wall, larger cooling of the spray and larger vortex structures of liquid fuel on the wall develop. The ignition delays again are noticeable longer at the colder wall. Therefore, the premixing period is longer and there is also much less sooty combustion when the wall temperature is lower.