This paper focuses on the gasoline spray characteristics added biodiesel 5% to apply in gasoline compression ignition engines. Spray macroscopic visualization was performed by planar laser-induced fluorescence (PLIF) technique. The spray characteristics were, therefore, conducted by varying high injection pressures with the common rail diesel system of a diesel engine and controlling ambient pressure (back pressure) by filling nitrogen gas in the constant volume combustion chamber (CVCC). The test fuel, gasoline blended with biodiesel 5% (GB05), and conventional diesel as the reference were performed to compare its behavior. Chemical and physical properties of the GB05, gasoline, and biodiesel including viscosity, density, lubricity, cloud and pour point were measured. A high-speed video camera was employed to record the spray pattern with frame speed 10,000 f/s. The spray penetration length and cone angle were measured and analyzed by image processing. Structure and density profiles were analyzed. As expected, 5% concentration of biodiesel significantly affected to enhance lubricity property of the GB. With small biodiesel concentration, the lubricity improves. When injection pressure was increased, the spray-penetration length was increased whereas the spray cone angle was slightly decreased. Under higher injection pressure, the turbulent structures are remarkable.
Spray macroscopic features are among the variables that have a direct impact on both engine performance and engine design, and they significantly affect the ignition and emission parameters of diesel engines. In this work, experimental procedures in a constant volume chamber that replicated conditions similar to those seen in diesel engines were used to determine how the addition of ethanol in diesel fuel affected the spray processes. The experimental design matrix was established by altering the proportion of ethanol added, pressure of injection, and also ambient pressure. The injection pressure is set to 50, 80 and 110 MPa, while the injection duration is fixed to 1600μs, moreover the ambient pressure inside the chamber is varied to 1.5 MPa and 3 MPa. Within these parameters, the consequences of the diesel and ethanol (DE) blending ratio on the spray macroscopic feature is emphasized. This influence is assessed by adjusting the blending ratio to 10%, 20%, and 30%, respectively, in order to observe its effects on the macroscopic characteristics of the spray. The spray evolution is analyzed through captured images taken from high-speed camera with the aid of shadowgraph optical method which utilizes two concave mirrors. Investigations are conducted into the spray formation, spray cone angle, spray penetration length, and spray area behaviors. The results indicate that ethanol in diesel affects the spray's macroscopic characteristics. The increase in ethanol content in diesel alters the fuel's physicochemical properties, resulting in a reduction not only in kinematic viscosity but also surface tension, thereby modifying the spray's macroscopic features. Consequently, the average spray penetration length is reduced, ranging from a minimum of 3% on DE10 to a maximum of 17% on DE30 under a 1.5 MPa ambient pressure and 50 MPa of injection pressure. Meanwhile, a broader spray cone angle is demonstrated, with the average difference ranging from 9º to 11º compared to pure diesel. Furthermore, slight variations in the spray area values are observed across all tested fuels, as the spray area is influenced not only by the spray penetration but also by the spray cone angles, with the largest differences exhibited by DE30, showing a 16% difference compared to D100. A thorough discussion of the mechanism underlying these events will be provided.
Efforts have been made to develop efficient and alternative powertrains for internal combustion engines including combustion at low-temperature (LTC) concepts. LTC has been widely studied as a novel combustion mode that offers the possibility to minimize both nitrogen oxide (NOx) and particulate matter (PM) via enhanced air-fuel mixing and intake charge dilution, resulting in lower peak combustion temperatures. Gasoline compression ignition (GCI) is a new ignition method related to the extensive classification of combustion at low-temperature approaches. In this method of ignition, a fuel with high evaporation characteristics and low autoignition sensitivity, for instance gasoline, is burned in a high pressure process. Despite many research efforts, there are still many challenges related with GCI performance for compression ignition (CI) engines. Unstable combustion for idle- to low-load operation was observed because of the low reactivity characteristics of gasoline, and this will affect the efficiency and emissions of the engine. This paper contributes a detailed review of several topics associated with GCI engines and the effort to improve its efficiency and emissions, including its potential when using gasoline-biodiesel blends. Some recommendations are proposed to encourage GCI engines improvement and development in the near future.
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