An investigation of the effect of chamber temperature on macroscopic spray characteristic under GCI engine conditions

Abstract

Spray characteristics play an important role in the application of gasoline compression ignition (GCI) engines because it affects engine performance as well as engine design. In this study, the influence of temperature on the non-vaporizing spray process was evaluated through the experimental process on the constant volume chamber (CVC) with simulated conditions of the GCI engine. The experimental matrix was constructed by varying key factors, including chamber temperature, fuel injection pressure, and chamber gas density. The CVC with built-in heaters allows for temperature variations at 323 K, 398 K, and 423 K. To accommodate low load conditions, the fuel injection pressure is varied between 50 MPa and 110 MPa. Simultaneously, chosen variations of gas density, including two levels of chamber density are selected at 15 kg/m3 and 30 kg/m3 respectively. In addition, the injector angles are arranged at 90° (vertical) and 180° (horizontal) to create an overview of the spray characteristics for the case study of GCI engine conditions, viable for future studies using a constant-volume combustion chamber (CVCC), or even rapid compression engine machine (RCEM) in which the injector is commonly set horizontally. The gasoline blended with biodiesel by volume percentage consisting of 80% gasoline and 20% biodiesel was used as the main fuel in this study, namely the GB20 blend. The results of the spray characteristics collected through the images of the spray process based on the Schlieren optical method and the highspeed camera, consisting of the spray evolution and penetration length, spray penetration rate, spray area, as well as the spray cone angle are investigated. The difference in the spray process is denoted as the chamber temperature is increased. The spray penetrates to the chamber wall limit more quickly at elevated temperatures. The results were recorded as a decrease in impingement time by 12% and 9.5%, respectively, at the injection pressure of 50 MPa together with an ambient gas density value of 15 kg/m3. The cone angle of the spray tends to reduce by approximately around 3° to 10° in all experimental cases when the chamber temperature is high. However, when entering the post-phase at 450–600 μs, cone angle differences are negligible during the injection reaching the stable phase.