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Influence of Test Configuration on the Combustion Characteristics of Polymers as Ignition Sources
| Content Provider | Semantic Scholar |
|---|---|
| Author | Julien, Howard L. |
| Copyright Year | 1993 |
| Abstract | ABSTRACTThe experimental evaluation of polymers as ignition sources for metals has beenaccomplished at the NASA White Sands Test Facility OVSTF) using a standard promotedcombustion test. These tests involve the transient burning of materials in high-pressureoxygen environments. They have provided data from which design decisions can be made;data include video recordings of ignition and non-ignition for specific combinations of metalsand polymers. Other tests provide the measured compositions of combustion products forpolymers at select burn times and an empirical basis for estimating burn rates. With thecurrent test configuration, the detailed analysis of test results requires modeling a three-dimensional, transient convection process involving fluid motion, thermal conduction andconvection, the diffusion of chemical species, and the erosion of the sample surface. At thehigh pressure extremes, it even requires the analysis of turbulent, transient convection wherethe physics of the problem are not well known and the computation requirements are notpractical at this time.An alternative test configuration that can be analyzed with a relatively-simpleconvection model was developed during the summer period. The principal change constitutesreplacing a large-diameter polymer disk at the end of the metal test rod with coaxial polymercylinders that have a diameter nearer to that of the metal rod. The experimental objective isto assess the importance of test geometries on the promotion of metal ignition by testing withdifferent lengths of the polymer and, with an extended effort, to analyze the surfacecombustion in the redesigned promoted combustion tests through analytical modeling of theprocess. The analysis shall use the results of cone-calorimeter tests of the polymer materialto model primary chemical reactions and, with proper design of the promoted combustiontest, modeling of the convection process could be conveniently limited to a quasi-steadyboundary layer analysis where the economical solution of parabolic equations is involved.The products for the summer period are: (1) a conceptual-level redesign of the testapparatus, and (2) the development and use of an approximate integral boundary layeranalysis to demonstrate the influence of geometry changes prior to testing. A computer codeSTAN5, an accurate numerical boundary layer model whose earlier versions were developedfor the NASA Lewis Research Center by the Fellow, also was installed and validated on theWSTF and New Mexico State University |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940020883.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
