Effects of shape and surface roughness on icing and condensation characteristics of an injector in a liquid phase LPG injection system

• We observe icing and condensation phenomena occurring on an LPG injector.
• We propose a design guideline for an icing-free LPG injector.
• Not only icing but condensation is suppressed via a polishing process.
• Numerical simulations and analytical investigation are carried out.

The liquid phase LPG injection (LPLi) system has been considered as one of the most promising fuel supply systems, however, its fuel supply characteristic is not stable due to formation of ice and condensed water droplets, resulted from instant vaporization of LPG at the tip of the injector. Formation and detachment of water–fuel-mixed ice and droplets have adverse influences on combustion stability of an engine by affecting air/fuel (A/F) ratio of air–fuel mixture supplied into the engine and on long-term durability of the fuel supply system. In this study, design guidelines of deicing injectors for LPLi systems were proposed based on the icing characteristics of a conventional LPLi injector and the deicing performance is experimentally evaluated for various engine working conditions. Furthermore, formation of not only ice but droplets on the injector was prevented by eliminating nucleation sites through polishing processes that decrease surface roughness of the tip of the injector to submicroscale.