Performance of an Liquid Phase LPG Injection Engine for Heavy duty Vehicles

A LPG engine for heavy duty vehicle has been developed using liquid phase LPG injection (hereafter LPLI) system, which has a strong potential as a next generation LPG fuel supply system. It has been revealed in this work that an LPLI system generates higher power, efficiency, and emits lower emission pollutants than the conventional mixer type system.

As a preliminary study on the LPLI system applicable to a heavy duty LPG engine, the engine output and combustion performance were investigated with various operating conditions using a single cylinder engine equipped with the different fuel supply systems. Experimental results showed that no problems occurred and the volumetric efficiency and engine output increased, respectively by about 10%, when the LPLI system is used. A decrease of the intake manifold temperature by the LPLI system has also been observed. These characteristics make it enable to decrease the exhaust gas temperature and perform better control of knocking phenomena, spark timing and compression ratio. An LPLI engine also has been successfully operate under λ = 1.5 or 30% EGR. An optimized swirl ratio for the heavy duty LPG engine was found around R_s = 2.0. Visualized in-cylinder flow near piston surface showed that high swirl ratios above 2.3 did not contribute to breaking swirl flow down into one with small turbulence scale.