Characteristics of Droplet and Icing Formation of an injector for Liquid Phase LPG Injection System

The use of clean gaseous fuel in automotive engines has been continuously increased in order to meet the reinforcing emission regulations and to efficiently utilize limited natural resources. Since the liquid phase LPG injection (LPLI) system has an advantage of higher power and lower emission characteristics than the mixer type fuel supply system, many studies and applications have been conducted. However, the heat extraction, due to the evaporation of liquid LPG fuel, causes not only a dropping of LPG fuel but also icing phenomenon that is a frost of moisture in the air around the nozzle tip. Because both lead to a difficulty in the control of accurate air fuel ratio, it can result in poor engine performance and a large amount of HC emissions.

The main objective of this study is to examine the characteristics of icing phenomenon and also aims to improve it through the use of anti-icing injection tip. An experimental investigation was carried out on the bench test rig in this study. Droplet and icing phenomena were visualized through a charge-coupled device (CCD) camera. It was found that n-butane, that has a relatively high boiling point (-0.50C) in comparison with propane and iso-butane, was a main species of droplet composition and also found that the droplet problem was improved by the use of a large inner to outer bore ratio nozzle whose surface roughness is smooth. The icing phenomena were decreased with an engine head temperature was increased, although a large amount of icing deposit was still observed in the case of 87°C. Also, it was observed that the icing phenomenon is improved by using aluminum anti-icing injection tip.