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Simulation Method for the Fire Suppression Process Inside the Engine Core and APU Compartments

Fire dangers exist inside engine core and auxiliary power unit compartments of commercial airplanes where jet fuel or lubricant oil leaks can catch fire on hot engine surfaces. Fire suppressants need to be quickly dumped into the compartments to prevent any eruption of fire. To quickly deliver fire suppressant from a storage bottle through a distribution pipe and injection nozzles to vented engine compartments, a fire extinguishing system should be designed and installed effectively. In certification tests of a fire extinguishing system, the optimum installation of multiple injection nozzles is an important factor contributing to successful fire suppression. At the present time, the selection of the nozzle locations and orientations for fire extinguishing systems depends primarily on a series of ground tests continued until the optimum installation conditions are found that satisfy the minimum performance standard. The certification test process is time consuming and relies greatly on empiricism. This paper deals with a simulation method for a fire suppression process that is based on the computational fluid dynamics method of modeling the two-phase flow physics. The method has been applied to simulate the tests of engines, auxiliary power units, and the FAA’s Nacelle Fire Simulator. Analysis results so far reveal excellent correlation with the test data, demonstrating the validity of the simulation method. It is anticipated that the method would serve as a useful tool not only for designing efficient firex systems, but also for guiding certification tests.