On the optimization of the air-LPG mixing system of a Diesel bus engine converted to gas

This paper investigates the air-LPG (Liquefied petroleum gas) engine mixer geometry effect on performance of a six-cylinder, heavy duty, IVECO engine, which is used to power urban buses. This engine was retrofitted from its Diesel version into bi-fuel gaseous fueling. Investigations were performed by numerical and experimental methods. A three-dimensional numerical modeling of the turbulent flow through two mixer geometries (17 holes mixer with a premixing room and 8 holes mixer) was undertaken using the 3D CFD code FloWorks. This modeling made it possible to provide a fine knowledge of the flow structures through the mixers, and to predict its operating feature fields. This model allowed the selection of the optimum mixer. The results indicated that mixer with 17 holes can produce a better homogenous mixture than those of 8 holes mixer. Experimental measurements are also carried out to validate this mixer by measuring the important engine performances. Comparative analysis of the experimental results showed that the 17 holes mixer presence into LPG engine has improved brake power (BP) and brake torque (BT) by 6.25 % and 3 % respectively.