Flame structure, uncertainties

The discrepancies among the existing experimental results may be attributed to the uncertainties associated with measurements under different types of experimental conditions. It is clearly evident that more measured data is needed for model validation. Nonetheless, the present model provides detailed insight into the key physiochemical processes involved in the laser-induced ignition of RDX, and can be effectively used to estimate ignition delay, heat release mechanisms, and flame structure. 

This radiative recombination is observed in flames181,213, electric arcs214, shock tubes194,215,216, and atomic flames192,217-219. In flames and arcs, the emission consists of diffuse bands on a continuum, whereas in atomic flames (the reaction of O with CO at low pressures and room temperature) there is no continuum and clear vibrational structure extends from below 3000 A out to at least 6000 A. The process has not been studied as thoroughly as O+NO, but enjoys the same complexities and uncertainties. 

Criteria for the validity of the flame-sheet approximation may be developed by analyzing the structure of the sheet (see Section 3.4). For calculation of flame shapes in the Burke-Schumann problem, the approximation usually is well justified, although uncertainties arise for strongly sooting flames. 

ABSTRACT The determination of loads from accidental fires with realistic accuracy in the oil gas industry offshore and petrochemical industry onshore is important for the prediction of exposure of persoimel, equipment and structures to the fires. Standards, Codes of Practice and other similar publications refer to thermal loading from jet fires from 100 to 400kW/m and from 50 to 250kW/m for pool fires. The application of inappropriate fire loads may lead to incorrect predictions of fatalities, explosion of pressure vessels and collapse of structures. Further uncertainties are associated with heat transfer from the flame to pressure equipment and strucmres, and their behaviour when affected by accidental fires. The Paper presents results of a review of fire models from various Standards and Codes of Practice, and data obtained from full scale tests. A parametric study of the various methods used in the industry is presented. A simulation-based reliability assessment (SBRA) method has been applied to quantify potential accuracy range and its consequences to fire effects on structures. 

Accidental fires interact with their environment, should this be pipework, equipment and structures in process plants in petrochemical industry, or facilities on offshore oil and gas installations. For plant design and risk assessment, cautious best estimates and uncertainty ranges are required for a number of combustion parameters. These include release rates, flame size and shape, heat output, thermal radiation to its environment, and the heating-up of structures, pipework and items of equipment. The estimate can result in the assessment of time to loss of functionality of these structures and pressurized equipment. 

---