Utilizing CFD for Prediction of HD1.3 Pressure Loads in a Cell with Venting

摘要

A methodology was presented at DDESB-2006 for the calculation of gas loading inside a room resulting from the ignition and burning of Hazard Class/Division (HD) 1.3 materials. That methodology, implemented in a spreadsheet, included thermodynamic sub-models for the burning material's creation of products, radiation heat loss to the walls, and time dependent venting to connected enclosures, such as a vestibule. The resulting pressure- time history was useful for the design of blast resistant walls and doors typically found in propellant containment or handling facilities. This paper describes an improved method which uses computational fluid dynamics (CFD) to describe the HD 1.3 burning, gas loading, and venting. Advantages over the spreadsheet method include the ability to model convective heat transfer and water spray deluge along with being able to resolve local flow field characteristics using fundamental flow equations as opposed to treating the entire room as a single control volume as was done in the spreadsheet method. The CFD method presented includes how the HD1.3 source term was modeled, including the important effects of burn rate, burning chemistry, sympathetic propagation, and the potential after burning of products in atmospheric air. Model setup is described for a recent analysis of a proposed chemical weapons disposal room processing solid rocket motors (SRMs) with and without venting and water spray. Details revealed by the model including venting size requirements and vent placing are reviewed. CFD results are compared to both the spreadsheet method and BlastX. Finally, model limitations are discussed, which include vent inertia and high speed flows.