Atomization and mixing performance of swirl-venturi lean direct injection

The rising cost of fuels and greater concern for the environment drive efforts in the laboratory to investigate the physics and chemistry of cleaner, more fuel efficient sources of power. Lean combustion has proven to decrease emissions and improve fuel efficiency. In order to achieve the benefits of lean combustion, the method in which fuel and air is mixed becomes critical to the overall performance of the engine. This paper is focused on fuel injection technology for aircraft engines. The objective of this work is to provide qualitative insight into the atomization and mixing process of the Lean Direct Injection. Mie scattering of liquid water was used to identify the location of water droplets in a cross section of the injector spray. High speed photography was used to capture the spray pattern. Experiments were performed with varied the swirl number from 0.58 to 1.0 and air-to-liquid ratios from 15.8 to 35.6 to investigate the effects these have on spray performance. It was found that the spray pattern is sensitive to swirl intensity, that as swirl number increases the spray penetration length decreases and spray pattern moves upstream toward the injector. Both improved atomization and mixing performance are a result of increasing the swirl number. The results of varied air-to-liquid ratio show the mixedness and dispersion of droplets increase with increasing momentum ratio. The results also show decreasing spray penetration length with increasing momentum ratio.