On probabilistic-physical and entropy approaches to combustion processes and determination of fire hazard

Introduction. The article provides an overview of the existing approaches to solving the problem of combustion of substances and materials, for their adequacy in determining their fire hazard of products and objects. The relevance of the work is due to the need to move from latent forms in determining the fire hazard of materials and products made from them (degrees of fire resistance, flammability groups, groups of the effectiveness of fire retardant coatings, etc.) to analytical forms describing the processes in the combustion theory. Problem statement. The task of the research is to determine the relationship between the theory of combustion of substances and materials and to assess their fire hazard in natural and man-made systems. Theoretical part. The system analysis of solutions to the combustion theory problems is performed. Its results became the basis of probabilistic-physical and entropy approaches, as well as proposals for changing standards designed to provide protection from fires. Conclusions. The results of the study showed the need to revise empirical approaches in assessing the fire hazard of materials and products made from them, which includes using thermoanalytic and acoustic methods and means.

Combustion Modeling Software Development, Verification and Validation

Historically, combustion modeling is important for many transportation- and ground-based applications. More recently, modeling has been offered as an early screening tool in the evaluation of a potential alternative aviation jet fuel. This combustion evaluation path would in theory be conducted by gas turbine Original Equipment Manufacturers (OEMs) on proprietary geometries and conditions. Ideally, OEMs would have access to the latest combustion theory models and would thus have the highest predictive confidence in their model predictions. Unfortunately, the latest combustion theory codes are not written for commercial purposes. This work identifies and develops a conduit for OEM usage of latest flamelet theory for use in the evaluation of alternative jet fuel combustion properties. A so-called “common format routine” (CFR) software with two low-dimensional manifold combustion models that can be used for laminar and turbulent applications is developed, which can be implemented by OEMs on proprietary hardware. The two models are the flamelet prolongation of the intrinsic low-dimensional manifold (FPI), used for premixed combustion, and the flamelet progress variable (FPV), utilized for nonpremixed combustion. The three branches of combustion are computed using a hybrid tool that combines homotopic flamelet calculations with scaling laws and the two- and one-point flamelet continuation methods in order to resolve bifurcations. The mixture fraction and progress variable definitions can be chosen to be any summation of atomic and species composition, respectively. Diffusivity coefficients can be computed using unity Lewis number, mixture-averaged and multicomponent species composition. The turbulence-chemistry interaction is tabulated a priori using Beta probability density function (PDF) for the mixture fraction and Beta or Dirac-delta PDF for the progress variable. Parallel computing is necessary for industrial quality tabulation. The tabulated table can be used for k-ε and k-ω RANS, SAS, DES, and LES simulations. The software can also interact with liquid spray and exchange mass between the liquid and gaseous phase. The software is verified against previous numerical simulations of canonical triple flames, piloted flames and single-cup combustor. The numerical results are validated against experimental measurements of temperature and species mass fractions. The CFR software advances Cantera 2.3. Hence, the software contains an inner layer of C++ code, an intermediate layer of Python wrappers, and an upper layer (GUI) of C# code. The pre-tabulated chemistry is used for CFD simulations. The tables are bi-linearly interpolated for laminar simulations and tri-linearly interpolated for turbulent simulations. The tabulated chemistry can be hooked to commercial software such as Fluent through C and Scheme codes. The simulated flames presented here were computed with this software. The developed software is reliable for modeling and simulation of complex combustion phenomena.