Ignition and combustion behaviors of the engine compartment fluids are presented based on their thermophysical and fire properties. The thermophysical properties considered are flash point (Tflash), autoignition temperature (Ta), hot metal surface ignition temperature (Thot), initial boiling point (Tib) and the final boiling point (Tfb). The fire properties considered are the heat release parameter, HRP (ratio of the chemical heat of combustion, ΔHch, to heat of vaporization, ΔHv) and product release parameter, PRP (ratio of the yield of the product, yj to ΔHv).
In operating vehicles, the temperatures of metal surfaces in the engine compartment exceed the Tflash, Ta, Thot, Tib and Tfb values for most of the engine compartment fluids. Thus, in vehicle crashes, the fluids are capable of starting engine compartment fires as they encounter the hot surfaces, as was observed in the crash and vehicle burn tests in the GM studies.
The fire properties of the engine compartment fluids (HRP and PRP) indicate that hydrocarbon-based fluids would burn with intensity comparable to or higher than gasoline and release large amounts of CO and smoke. However, the non-hydrocarbon based fluids would burn with lower intensity than gasoline and release lower amounts of CO and smoke. Fire retardation of the engine compartment fluids is generally not practical, however, providing fire suppression system in the engine compartment and fire barriers between the engine and passenger compartments would be effective in enhancing the passenger survivability.
The Tflash, Ta, Thot, Tib and Tfb values of the fluids are interrelated and thus a regulatory standard could be developed for the engine compartment fluids, where limits for only Tib, Tfb and HRP could be specified for the acceptance of the fluids.