Hybrid finite-volume/transported PDF method for the simulation of turbulent reactive flows

A novel computational scheme is formulated for simulating turbulent reactive flows in complex geometries with detailed chemical kinetics. A Probability Density Function (PDF) based method that handles the scalar transport equation is coupled with an existing Finite Volume (FV) Reynolds-Averaged Navier-Stokes (RANS) flow solver. The PDF formulation leads to closed chemical source terms and facilitates the use of detailed chemical mechanisms without approximations. The particle-based PDF scheme is modified to handle complex geometries and grid structures. Grid-independent particle evolution schemes that scale linearly with the problem size are implemented in the Monte-Carlo PDF solver. A novel algorithm, in situ adaptive tabulation (ISAT) is employed to ensure tractability of complex chemistry involving a multitude of species. Several non-reacting test cases are performed to ascertain the efficiency and accuracy of the method. Simulation results from a turbulent jet-diffusion flame case are compared against experimental data. The effect of micromixing model, turbulence model and reaction scheme on flame predictions are discussed extensively. Finally, the method is used to analyze the Dow Chlorination Reactor. Detailed kinetics involving 37 species and 158 reactions as well as a reduced form with 16 species and 21 reactions are used. The effect of inlet configuration on reactor behavior and product distribution is analyzed. Plant-scale reactors exhibit quenching phenomena that cannot be reproduced by conventional simulation methods. The FV-PDF method predicts quenching accurately and provides insight into the dynamics of the reactor near extinction. The accuracy of the fractional time-stepping technique in discussed in the context of apparent multiple-steady states observed in a non-premixed feed configuration of the chlorination reactor

Perturbation Dynamics in Turbulent Flames

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143054/1/6.2017-1100.pd

CFD Analysis of Premixed Methane Chlorination Reactors with Detailed Chemistry

With the implementation of efficient algorithms for the accurate calculation of reaction source terms, computational fluid dynamics (CFD) is now a powerful tool for the simulation and design of chemical reactors with complex kinetic schemes. The example studied in this work is the methane chlorination reaction for which the detailed chemistry scheme has 152 reactions and 38 species. The adiabatic, jet-stirred chlorination reactor used for the CFD simulations is an insulated right cylinder with a coaxial premixed feed stream at one end. In order for this reactor to remain lit, recirculation of hot products is crucial, and hence, reactor stability is sensitive to both macroscale and microscale mixing. By neglecting density variations, a Lagrangian composition probability density function (PDF) code with a novel chemistry tabulation algorithm (in-situ adaptive tabulation or ISAT) for handling complex reactions is used to simulate the species concentrations and temperature field inside of the reactor. In addition, a reduced mechanism with 21 reactions and 15 species is tested for accuracy against the detailed chemistry scheme, a simplified CSTR model is used to illustrate the shortcomings of zero-dimensional models, and a pair-wise mixing stirred reactor (PMSR) model is used to show the stabilizing effect of micromixing on reactor stability. The CFD simulations are generally in good agreement with results from pilot-scale reactors for the outlet temperature and major species

Numerical investigation of vibrational relaxation coupling with turbulent mixing

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143099/1/6.2017-0663.pd

Effect of Feed-Stream Configuration on Gas-Phase Chlorination Reactor Performance

Chlorination of hydrocarbons is an industrially important process used for the production of commercially viable environmentally friendly chemicals. The highly exothermic nature of these reactions necessitates a thorough study of reactor stability and product feasibility. Here, computational fluid dynamics (CFD) is used to analyze the performance of a coaxial rightcylindrical insulated reactor for different inlet flow configurations. Chlorination reactions involve a large number of radicals and other intermediates, and hence, direct simulations using traditional CFD techniques are difficult because of the stiff nature of the reaction scheme involved. A novel algorithm for reaction computation, in situ adaptive tabulation (ISAT), is used to obtain considerable computational gains. The joint probability density function (JPDF) transport equation for the scalars with closed terms for reaction is solved using a Monte Carlo particle algorithm in tandem with a finite-volume (FV) Reynolds-averaged Navier-Stokes (RANS) method. The particle method handles transport of 15 scalars along with enthalpy and feeds back mean field values of temperature and molecular weight that are used by the FV code to correct the flow for reaction. The scalar scatter plots conditioned on the mixture fraction are used to study the details of the kinetics in different reactor zones. Comparison of premixed and segregated inlets is done to determine reactor stability and product yield. Conclusions are then drawn about fundamental properties of the reactor and broad considerations for reactor design

Turbulent Mixing and Combustion of Supercritical Jets

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143049/1/6.2017-0141.pd

Hybrid finite-volume/transported PDF method for the simulation of turbulent reactive flows

A novel computational scheme is formulated for simulating turbulent reactive flows in complex geometries with detailed chemical kinetics. A Probability Density Function (PDF) based method that handles the scalar transport equation is coupled with an existing Finite Volume (FV) Reynolds-Averaged Navier-Stokes (RANS) flow solver. The PDF formulation leads to closed chemical source terms and facilitates the use of detailed chemical mechanisms without approximations. The particle-based PDF scheme is modified to handle complex geometries and grid structures. Grid-independent particle evolution schemes that scale linearly with the problem size are implemented in the Monte-Carlo PDF solver. A novel algorithm, in situ adaptive tabulation (ISAT) is employed to ensure tractability of complex chemistry involving a multitude of species. Several non-reacting test cases are performed to ascertain the efficiency and accuracy of the method. Simulation results from a turbulent jet-diffusion flame case are compared against experimental data. The effect of micromixing model, turbulence model and reaction scheme on flame predictions are discussed extensively. Finally, the method is used to analyze the Dow Chlorination Reactor. Detailed kinetics involving 37 species and 158 reactions as well as a reduced form with 16 species and 21 reactions are used. The effect of inlet configuration on reactor behavior and product distribution is analyzed. Plant-scale reactors exhibit quenching phenomena that cannot be reproduced by conventional simulation methods. The FV-PDF method predicts quenching accurately and provides insight into the dynamics of the reactor near extinction. The accuracy of the fractional time-stepping technique in discussed in the context of apparent multiple-steady states observed in a non-premixed feed configuration of the chlorination reactor.</p