CFD modeling of cargo compartment fire extinguishing system onboard electric aircraft

Abstract

Today, when an aircraft is to be certified and approved to ensure safe flight, a series of physical tests of safety critical systems and components are carried out. Among these systems is the fire suppression system for the cargo compartment of the aircraft. The existing fire extinguishing system designs depend primarily on experience and physical tests. These tests are both costly and time consuming and usually end up with the systems being over dimensioned to ensure they meet the requirements for certification. The aviation industry has seen the potential in applying computational fluid dynamics (CFD) simulation as a scientific design tool for these systems, in order to reduce the number, and thus the cost, of physically performed tests. The objective of this thesis is to develop a first CFD model of the cargo compartment fire extinguishing system. The model can then be adjusted in terms of parameters and design to optimize the system efficiency before certification testing. The modeling of the fire extinguishing system is divided into two separate models; one for the discharge bottle and piping system, and one for the cargo compartment. The Halon outlet parameters from the piping system are then used as inlet parameters to the cargo compartment. The cargo compartment is simulated for four configurations where the inlet flow is varied between being straight or angled and with or without simplified discharge nozzles. The simulations show that an angled discharge of Halon is preferred because it spreads Halon more evenly compared to a straight discharge flow. Among the angled inlet flow and nozzles, 90 degree nozzles provide the highest degree of coverage by having the most probes that detect Halon. It is also this nozzle design that best mimics those designs provided by nozzle suppliers.