Abstract
The multiple mapping conditioning (MMC) approach is applied to two non-piloted CH 4 / H 2 / N 2 turbulent jet diffusion flames with Reynolds numbers of Re = 15,200 and 22,800. The work presented here examines primarily the suitability of MMC to simulate CH 4 / H 2 flames with varying Re numbers. The equations are solved in a prescribed Gaussian reference space with only one stochastic reference variable emulating the fluctuations of mixture fraction. The mixture fraction is considered as the only major species on which the remaining minor species are conditioned. Fluctuations around the conditional means are ignored. It is shown that the statistics of the mapped reference field are an accurate model for the statistics of the physical field for both flames. A transformation of the Gaussian reference space introduced in previous work on MMC is used to express the MMC model in the same form as CMC. The most important advantage of this transformation is that the conditionally averaged scalar dissipation term is in a closed form. The corresponding temperature and reactive species predictions are generally in good agreement with experimental data. The application to real laboratory flames and the assessment of the new conditional scalar dissipation model for the closure of the singly conditioned CMC equation is the major novelty of this paper. The results are therefore primarily examined with respect to changes of the conditionally averaged quantities in mixture fraction space.
Highlights
The primary focus of new model development in turbulent reacting flows is the accurate description of the coupling between reaction and molecular mixing and the associated closure problems for the terms representing these two processes
The multiple mapping conditioning (MMC) equation is solved with a Gaussian reference field and successful modelling for the Probability Density Function (PDF) of the mapping function has been achieved
MMC provides an implicit closure for the conditionally averaged scalar dissipation and the mixture fraction PDF which are needed for Conditional Moment Closure (CMC), and MMC is closed
Summary
The primary focus of new model development in turbulent reacting flows is the accurate description of the coupling between reaction and molecular mixing and the associated closure problems for the terms representing these two processes. In the simplest formulation, the mixture fraction can be selected as the only major species and MMC is equivalent to singly conditioned CMC but with the advantage that the conditional dissipation term appears in closed form. Ozarovsky et al [23] implemented a joint PDF approach closed at the joint scalar level for DLR A and DLR B and explored different methods of flame ignition. They reported problems in predictions at the nozzle where steep gradients in mixture fraction necessitate accurate scalar dissipation estimates.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
