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Spray evaporation characteristics have an important influence on air-fuel mixing and the optimization of combustion to achieve high performances and ultra-low emissions. This study aims to compare and analyze the evaporation characteristics of five-hole gasoline direct injection injectors with different hole arrangements under flash-boiling conditions. The holes of two injectors are arranged as a pentagon. The hole arrangement of injector A (standard type) is similar to a regular pentagon, whereas two holes on the sides of the pentagon corresponding to injector B (skew type) are shifted toward the inside and bottom of the pentagon. In this study, Schlieren and Mie-scattering techniques are used to visualize the evaporation of spray. Although this method is difficult to extract the vapor area from the vapor-liquid mixing zone, it can accurately calculate the area of the pure evaporation zone by subtracting the area of the liquid phase mixing zone from the global area. Therefore, this study compared the spray evaporation characteristics of the two injectors relatively, by calculating the area of the pure evaporation zone. Experiments were compared with different injector directions (0° and 90°) and under a wide range of superheat conditions (0°C–130 °C). Only a slight difference is found between the evaporation characteristics of the standard- and skew-type injectors in the 0° direction. However, in the 90 direction, before the spray collapses, the larger plume spacing of the skew-type injector, determined by the injector hole arrangement, promotes air-flow in the spray center, leading to larger evaporation ratio. After the spray collapses, the spray structure difference caused by the hole arrangement is reduced, and the two injectors exhibit similar evaporation characteristics. |
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