Publications

Proposed for publication in Elsevier.

Prager, Jens; Najm, H.N.; Sargsyan, Khachik S.; Safta, Cosmin S.

Abstract not provided.

Prager, Jens; Najm, H.N.; Zador, Judit Z.

Abstract not provided.

Prager, Jens; Najm, H.N.

Abstract not provided.

Combustion and Flame

Prager, Jens; Najm, H.N.

Abstract not provided.

Proceedings of the Combustion Institute

Prager, Jens; Najm, H.N.; Valorani, Mauro; Goussis, Dimitris A.

An automated procedure has been previously developed to generate simplified skeletal reaction mechanisms for the combustion of n-heptane/air mixtures at equivalence ratios between 0.5 and 2.0 and different pressures. The algorithm is based on a Computational Singular Perturbation (CSP)-generated database of importance indices computed from homogeneous n-heptane/air ignition solutions. In this paper, we examine the accuracy of these simplified mechanisms when they are used for modeling laminar n-heptane/air premixed flames. The objective is to evaluate the accuracy of the simplified models when transport processes lead to local mixture compositions that are not necessarily part of the comprehensive homogeneous ignition databases. The detailed mechanism was developed by Curran et al. and involves 560 species and 2538 reactions. The smallest skeletal mechanism considered consists of 66 species and 326 reactions. We show that these skeletal mechanisms yield good agreement with the detailed model for premixed n-heptane flames, over a wide range of equivalence ratios and pressures, for global flame properties. They also exhibit good accuracy in predicting certain elements of internal flame structure, especially the profiles of temperature and major chemical species. On the other hand, we find larger errors in the concentrations of many minor/radical species, particularly in the region where low-temperature chemistry plays a significant role. We also observe that the low-temperature chemistry of n-heptane can play an important role at very lean or very rich mixtures, reaching these limits first at high pressure. This has implications to numerical simulations of non-premixed flames where these lean and rich regions occur naturally. © 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Najm, H.N.; Prager, Jens

We present computations of a methane-air edge flame stabilized against an incoming flow mixing layer, using detailed methane-air chemistry. We analyze the computed edge flame, with a focus on NO-structure. We examine the spatial distribution of NO and its production/consumption rate. We investigate the breakdown of the NO source term among the thermal, prompt, N{sub 2}O, and NO{sub 2} pathways. We examine the contributions of the four pathways at different locations, as the edge flame structure changes with downstream distance, tending to a classical diffusion flame structure. We also examine the dominant reaction flux contributions in each pathway. We compare the results to those in premixed, non-premixed, and opposed-jet triple flames.

Prager, Jens

Abstract not provided.