It is known that in spark ignition (SI) engines with external mixture formation a certain part of injected fuel impinges internal surfaces of the intake manifold. This part of the fuel deposits on the manifold surface in the form of a liquid film, which is crawling to cylinders at substantial lower velocity than the main air/fuel mixture stream. This leads to variations in the mixture quality under transient operating conditions, thus causing difficulties in the engine control, because only a part of the injected fuel enters the combustion chamber during the corresponding cycle. When using heavy fuels, such as diesel or JP, in spark ignition engines is considered (for example, in UAV applications), the fuel film formation and fuel/air mixing problems increase and become even more challenging. The main goal of the presented study was preventing fuel film formation by ultrasonic activation of the fuel spray impingement surface. We present results of experiments carried out with a single fuel drop and a real fuel spray formed by the fuel-port injector. In the experiments with a single drop, effects of the drop size, fuel type, ultrasound performance etc. on the drop behavior were studied using a high-speed photography. In experiments with a real fuel spray, phenomena of fuel film formation and size distribution of the impinging and rebound droplets were studied using a high-speed photography and PDPA/LDV technique. Obtained results showed a high efficiency of the suggested method of fuel impingement surface activation for preventing fuel film formation.
