This week a new paper has been published in the IFRF Combustion Journal (http://www.journal.ifrf.net), entitled:

Design, evaluation measurements and modelling of a small swirl stabilised laboratory burner

By: N. G. Orfanoudakis, A. Hatziapostolou, K. Krallis, E. Mastorakos, K. Sardi, D. G. Pavlou & N. Vlachakis

CORRESPONDING AUTHOR

N. G. Orfanoudakis
TEI Chalkis
Mechanical Engineering Department
Laboratory for Steam Boilers
Turbines & Thermal Plants, Greece

Email: norfan@teihal.gr

This paper discusses the method of scaling up of pilot-scale tests of a swirl-stabilized coal burner to full-scale burner performance.  The authors use pilot-scale measurements, constant velocity scaling and computational fluid dynamic simulations to investigate the performance of the full-scale burner. Particular attention was given to the effect of swirl on the particle trajectories. Both the RNG and k-ε  turbulence modeling was investigated in the CFD analysis. This type of burner study is shown to give the authors an insight into the performance of the coal burner at the larger scale and can be used to refine the burner design.

Summary:
The effect of swirl on the motion of coal particles in the near-burner region of a multi-fuel swirl-stabilised laboratory burner of total thermal input of 100kW was investigated experimentally and also by the use of CFD.  The burner was designed as a scale model of a 10MW coal burner operating in a cement rotary kiln or boiler and was able to burn a combination of gaseous, liquid and pulverised solid fuels.  Temperature and Laser Doppler measurements of all three velocity components were obtained in reacting single and multiphase flows as a function of swirl number in the range of 0.6 to 0.9 and confirmed the ability of the burner to produce close-to-industrial conditions making it a powerful tool in the field of combustion research. 

In detail, the velocity measurements showed that the flow field was axisymmetric and an internal recirculation zone (IRZ) in the shape of a toroidal vortex was formed around the centreline for swirl numbers of at least 0.65.  A 60ncrease in the swirl number, from 0.65 to 0.9, resulted in a 30idening of the IRZ.  Solid particle measurements revealed that the width of the zone where coal particles recirculate is by 20arger than that formed in the single phase case and that most of the coal particles are centrifuged away from the IRZ, particularly at high swirl numbers.
A numerical investigation on the effect of the swirl number on the fluid and particle motion downstream the burner in isothermal flows has also been performed.  The flow field was modelled as 2D axisymmetric and results were obtained with both the renormalisation group (RNG) and k-ε turbulence models and compared to measurements obtained in non combusting flows. As expected, the RNG model provided a more realistic description of the flow field than the k-ε turbulence model, with numerical results being in good agreement with the measurements even at the high swirl number.  Lagrangian tracking of coal particles in the range of 1 to 150 μm has also been performed as a function of swirl number.  The calculations revealed that particles of diameter larger than about 20 μm are centrifuged away from the IRZ in accordance to the measurements, while particles larger than 100 μm, due to their high inertia remain on the IRZ boundary and are neither centrifuged, nor entrained inside the recirculation zone. In accordance with the measurements, the calculations also showed that the effect of centrifuging is decreased when the swirl number is reduced.

An attempt to scale-up the results, through the application of Stokes number similarity and of the standard “constant velocity scaling” concept, has also been pursued and comparisons of the present findings to the flow field downstream a 120 kW and a 12 MW industrial burner were made.

Key Words:
Coal combustion, burner design, turbulence modeling, Scale-up, particle tracking, measurements.

FULL PAPER:
The full paper may be downloaded from the server, in the “New Papers” section (http://www.journal.ifrf.net/articles.html), by clicking on the Acrobat PDF icon alongside the title.

Publication in the Journal
The Editor-in-Chief would like to remind all potential authors that publication in the Journal is open to all. If you have interesting results to publish in the field of, or related to, industrial combustion, we invite you to prepare a paper according to the guidelines given in the Author’s Guide on the website (http://www.journal.ifrf.net/).

Papers may be regular “articles” (typically up to 20 pages) or Communications (typically up to 4/5 pages). Review papers can of course be longer. Remember that figures and graphics in general can be in full color. This advantage should be encouraged.

All manuscripts and associated files, proposed for publication should be sent by the Corresponding Author in a compressed/zip file, as an email attachment to journal@ifrf.net. This file should include a statement that the proposal’s content is unpublished material that has not being submitted for publication elsewhere. When an article by the author(s) is cited in the proposed article as “in press”, a copy of this article should accompany the proposed article and should be included in the compressed file.
The Editor-in-Chief looks forward to receiving your proposals.