Numerical Investigation of premixed turbulent flames in staged Combustion gas turbine at high operationg pressures

A turbulent combustion model assumes that the flame in an explosion is a library of flamelets. The reaction model is usually segmented into two: the reaction subclosure of turbulent flame speed ST, and the reaction closure with the transport equations(s), reaction rate expression and other related expansive terms. The combustion model relies on the concept that the flame propagates into the unburned mixture with a defined velocity (which of course differs with respect to the chosen relative position, for e.g., along the unburned or burned side of the flame brush). The global quantity ST increases with decreasing Le and/or increasing preferential diffusion (PD). Expectedly, in lean H2 mixtures characterized by substantial differences in thermal diffusivity, and among mass diffusivities of governing fuel and oxidant, the effects (of Le and/or PD) are very strong even if the turbulence intensity is exceedingly higher than unstretched laminar flame speed – a perspective of H2 explosion modelling.

Substantiating the ST model for Ignition and Time-evolution phenomena allow in understanding and locating the zone of ignition, and the inception phase of flame propagation. Inclusion of the DL instabilities still furthers in picturing out the flame instabilities, an important occurrence in H2 modelling following its high diffusive nature. Moreover, of course the success of explosion simulation depends on the selection of the turbulence models; with LES retaining the edge over RANS in handling wake-generated turbulence.

In a developing flame (or explosion), pressure evolution is to be trapped, which therefore requires that the reaction model be sensitive to pressure effects. A turbulent combustion model assumes that the flame in an explosion is a library of flamelets. The reaction model is usually segmented into two: the reaction subclosure of turbulent flame speed ST, and the reaction closure with the transport equations(s), reaction rate expression and other related expansive terms. Substantiating the ST model for Ignition and time-evolution phenomena allow in understanding and locating the zone of ignition, and the inception phase of flame propagation. Inclusion of the DL instabilities still furthers in picturing out the flame instabilities, an important occurrence in H2 modelling following its high diffusive nature. Moreover, of course the success of explosion simulation depends on the selection of the turbulence models; with LES retaining the edge over RANS in handling wake-generated turbulence.

In a developing flame (or explosion), pressure evolution is to be trapped, which therefore requires that the reaction model be sensitive to pressure effects. The AFSW reaction model holds advantage by invoking the high-pressure effects explicitly. But the model remains to be tested from a comparative study using some measurable quantities as: maximum pressure, time to build the maximum pressure, and duration of pressure pulse and so on from the experiments. Ironically, the reaction models based on the effects due to the Markstein number, flamelet quenching, or small-scale wrinkling provide no clue to predicting the leading-edge speed, a concept viable to H2 explosion and consequent pressure build-up evaluation.

Investigate the effects of operating pressures above atmospheric in sequential increase up to 32 bar. In three different configurations will be studied for mixing quality of fresh mixtures: simple Annular, Radial jets, and Lobe mixers. The best of three will be chosen to further investigate for low emissions.

First year:

1. Literature review
2. Understanding the physics of turbulence, RANS turbulent models, and reaction kinetics of hydrogen.
3. Numerical set up of tutorial cases and analysing the results by graphical plots.

Second year:

1. Literature review continued
2. Understanding the Darrieus-Landau instabilities in turbulent flames, and its effect on flame evolution.
3. Generation of actual numerical cases, grid independency tests and do parametric studies of effect of various solvers, discretization schemes, different kinetic mechanisms and influence of pressure on ignition and hydrogen flame evolution.
4. Oral presentation in an international conference and one Q1 journal paper

Third and last year:

1. Continue review of accumulated literature
2. Cay out Large-eddy simulations for above test cases
3. Publication of one Q1 journal
4. Doctoral thesis.