Gas-to-Liquid Sprays at Different Injection and Ambient Conditions

Abstract

Alternative fuels exhibit potential as a clean fuel and suitable to address problems of energy security and environmental pollution. The main objective of this research was to provide the fundamental data of ignition delay and combustion characteristics for gas-to-liquid (GTL) fuels. Experiments were carried out in a constant-volume vessel under diesel-engine conditions to study the effects of various injection and ambient conditions on ignition and combustion characteristics. The results showed that all tested fuels exhibited similar ignition-delay trends: Ignition delay increased as ambient temperature, ambient pressure, and oxygen concentration decreased. The result of changing injection pressures and nozzle-hole diameters did not significantly affect ignition-delay values for all tested fuels. The variation in ignition-delay values was small at temperatures higher than 700 K but large at temperatures less than 700 K. In addition, the result showed that GTL fuels with high cetane number corresponded to shorter ignition delay and smoother heat-release rate than those for gas-oil (conventional diesel fuel) at the same temperature, pressure, and oxygen concentration. The blend GTL fuel improved ignition quality and combustion than that of gas-oil. Shadowgraph images showed that GTL fuels exhibited shorter spray penetration and mixed with the hot air quicker than gas-oil. In addition, GTL fuels showed suitability for premixed charge compression-ignition operations owing to ignitability at low temperature. The obtained results provide useful information for finding the optimal conditions for the design and control of diesel engines fuelled by synthetic GTL fuels.