Title

Effect of air extraction for cooling and/or gasification on combustor flow uniformity

Abstract

Reducing emissions is on important issue facing gas turbine manufacturen. Almost all of the previous and current research and development for reducing emissions bas focused, however, on flow, heal transfer, and combustion behavior in the combustors or on the uniformity of fuel injection without placing strong emphasis on the flow uniformity entering the combustors. In response to the incomplete understanding of the combustor's inlet air flow field, experiments were conducted in a 48% scale, 360° model of the diffuser-cotnbustor section of an industrial gas turbine. In addition, the effect of air extraction fnr cooling or gasification on the flow distributions at the combustors' inlets was also investigated. Three different air extractioa rates were studied: 0% (baseline), 5% (airfoil cooling), and 20% (for coal gasification). The flow uniformity was investigated for two aspects: (a) global uniformity, which compared the mass flow rate} of combustors at different locations relative to the extraction port, and (b) local uniformity, which examined the circumferential flow distribution into each combustor. The results indicate that even for the baseline case with no air extraction there was an inherent local flow aonuniformity of 10 ∼20% at the inlet of cacb combustor due to the complex flow field in the dump diffuser and the blockage effect of the cross-flame tube. More flow was seen in the portion further away from tha gas turbine center axis. The effect of 5% air extnctioa was small. Twenty-percent air extraction introduced approximately 35% global flow asymmetry diametrically across the dump diffuser. The effect of air extraction on the combustor's local flow uniformity varied with the distances between the extraction port and each individual combustor. Longer top hats were installed with the initial intention of increasing flow mixing prior to entering the combustor. However, the results indicated that longer top hats do not improve the flow uniformity; sometimes, adverse effects can be seen. Although a specific geometry was selected for this study, the results provide sufficient generality to benefit other industrial gas turbines.

Publication Date

1-1-1998

Publication Title

Proceedings of the ASME Turbo Expo

Volume

3

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

DOI Link

https://doi.org/10.1115/98-GT-102

Socpus ID

84971617613 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84971617613

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