Other Projects

Ullage Flammability in Aircraft Fuel Tanks

For the Navy, BlazeTech reviewed a model and test data on the flammability of ullage in an aircraft fuel tank.  The model assumed well-stirred ullage and equilibrium thermodynamics, which limited its applicability.  We showed that a zonal model is more realistic and provides the generality sought after by the Navy while being simple enough to run on a personal computer.  In this model, stratification was related to tank inclination and a Rayleigh number. Out-gassing of dissolved oxygen and nitrogen was related to heat and mass transport processes in the fuel.  These effects enable predictions of dynamics effects (climb/dive rates, altitude and fuel temperature) during a mission profile as well as fuel tank design features such as nitrogen inerting and oxygen scrubbing. (See also BlazeTank.)

Simulation of External In-Flight Aircraft Fires

For the Air Force, we conceived of a novel approach to simulate fires external to aircraft in flight using scale model planes in a wind tunnel. We formulated a plan to validate this approach in a unique test facility (500 lb/sec) operated by the Air Force. Also, we carried out the fire safety aspects of a national study on the impact of switching aircraft fuels from JP4 to heavier hydrocarbons. The study was led by General Electric. We also participated in a study led by Boeing on the ignition potential of aircraft fuels by friction and impact sparks.

Effect of Clutter on Aircraft Fire Suppression Systems

For the Air Force, we modeled the thermodynamics and dispersion of fire suppression agents in aircraft bays.  Our focus was on candidate Halon replacement agents with minimum ozone depletion potential such as FC-31-10, PFC-614, FC-218, and HFC-227; and on dry bays and engine nacelles containing "clutter".  We modeled liquid flashing, droplet formation, spray behavior, droplet impingement on clutter surfaces, drag effects of clutter, and flame stabilization in the wake of clutter.  The model was used to compare agent performance with and without clutter. Also, we designed a clutter simulant consisting of a uniform network of thin, orthogonal, baffles placed normal to the direction of flow in a staggered fashion.  Tests were conducted at the Air Force using this network with various baffle widths and spacings.  The results showed significant improvements in the simulation of clutter effects over previous configurations.

 Conclusions

• Effects of clutter depend on physical and thermodynamic properties of agent
• Tests showed that clutter had a significant effect on agent selection
• ranking of agent performance with/without clutter was not the same
• clutter requires more agent mass to extinguish fire
• Real life performance is complex and requires detailed evaluation by engineering and computational models such as MIFAC

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