Computational Fluid Dynamics (CFD) Analysis and Development of Halon- Replacement Fire Extinguishing Systems (Phase 2).

摘要

Many Halon replacement fire extinguishing agents have been proposed and are being tested. Replacement agents have different properties than Halon, and thus perform differently in existing application hardware. Computational Fluid Dynamics (CFD) is ideally suited to analyze agent flow through application hardware and also agent flow after discharge from the hardware. In previous (Phase I) work, CFD Research Corporation developed a computational model for a 20 lb handheld fire extinguisher with Halon 1211. The model was improved in this Phase II work to more accurately reflect the pressure-density relationship of Halon 1211 in an expansion driven phase change. The model was used to investigate the velocity, pressure and gas/liquid mixture throughout the assembly. Benchmark data were also taken to calibrate the assembly, and velocities were measured at six location outside the nozzle. CFD analysis agrees with measurements fairly well. Pressure and velocity at the nozzle exit are in good agreement. However, the velocity decay 50 and 75 mm downstream of the nozzle exit are underpredicted. Causes of the underprediction are explained, and ways to improve the model in Phase III are discussed.