A Vehicle Level Transient Thermal Analysis of Automotive Fuel Tanks

Maintaining the fuel temperature and fuel system components below certain values is an important design objective. Predicting these temperatures is therefore one of the key parts of the vehicle’s thermal management process. One of the physical processes affecting fuel tank temperature is fuel vaporization, which is controlled by the vapor pressure in the tank, fuel composition and fuel temperature. Models are developed to enable the computation of the fuel temperature, fuel vaporization rate in the tank, fuel temperatures along the fuel supply lines, and follow its path to the charcoal canister and into the engine intake. For diesel fuel systems where a fuel return line is used to return excess fluid back to the fuel tank, an energy balance will be considered to calculate the heat added from the high-pressure pump and vehicle under-hood and underbody. In this work, a transient heat transfer model is developed to compute the heat transfer between the in-tank fuel and the vehicle under-hood or underbody where the effect of exhaust and convection are considered. A fuel vaporization model is applied to compute the vaporization rate and the resulting cooling effect occurring in the fuel tank based on the fuel Reid Vapor Pressure (RVP), fuel temperature and pressure inside the tank. The model will also predict transient temperatures for fuel tank surface, in-tank fuel and fuel supply and return lines. Analysis is conducted for various driving conditions and for a range of fuel RVP values. The analysis will assist in determining required heat shielding to the fuel tank, exhaust system and rerouting of fuel lines.