Application of field synergy principle to analysis of flow field in underhood of LPG bus

Abstract

Overheating in the underhood of liquefied petroleum gas (LPG) buses not only increases gas consumption, but also deteriorates dynamic performance and undermines fuel economy and reliability. In this study, the thermal performance in the LPG bus underhood is examined according to heat transfer theory and field synergy principle. First, the air flow field in the underhood is numerically analyzed using the three dimensional computational fluid dynamics. Then, the formation mechanism of flow field is studied to account for high local temperature, low flow rate, and circulation heating in the underhood. In addition, the interaction among the underhood components, velocity field, and temperature field is explored. According to the field synergy principle, the layout of the underhood is adjusted to improve the heat transfer capability of the compartment and to reduce the temperature, with the ultimate goal of improving power performance and fuel economy. Simulation results show that significant reduction in temperature can be achieved. Moreover, a decrease in synergy angle between the air velocity and heat flow was obtained at different locations in the improved layout of components in the underhood. The simulation results verify the contribution of the field synergy control theory to optimization of the underhood flow field.