The CSP/PSR approach in reduced chemistry of premixed ammonia combustion

In order to fire gas turbine engines on ammonia, knowledge is acquired about the combustion characteristics and model possibilities of this carbon free fuel. To this end in this paper the projection of detailed chemistry of ammonia on a low dimensional chemistry model is investigated at atmospheric pressure and temperature conditions. On basis of this turbulent combustion models for ammonia can developed on basis of available modeling procedures for hydrocarbon combustion. These turbulent combustion models are based on a projection of the high dimensional detailed chemistry on a single dimension reaction progress variable. This work describes a methodology to define an optimal expression of the reaction progress variable in the context of tabulated chemistry on basis of laminar premixed combustion. Two methods are used: the Computational Singular Perturbation (CSP) method and a sensitivity analysis of the time scales evaluated with a Perfectly Stirred Reactor (PSR). The thermo-chemical databases computed with these techniques are compared in the cases of a freely propagating flame, in the laminar premixed regime and under stoichiometric conditions. The accuracy of the chemical projection is evaluated on basis of a comparison of predicted species concentration and temperature profiles in a freely propagating flame based on detailed chemistry and the single reaction progress variable. It is found that the projection is very accurate and hence the combustion of ammonia can be predicted on basis of one dimensional tabulated chemistry.