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Title: Near field flow structure of isothermal swirling flows and reacting non-premixed swirling flames

Two confined lean non-premixed swirl-stabilized flame typologies were investigated in order to achieve detailed information on the thermal and aerodynamic field in the close vicinity of the burner throat and provide correlation with the exhaust emissions. Previous finding indicated the generation of a partially premixed flame with radial fuel injection and a purely diffusive flame with co-axial injection in a swirling co-flow. In the present work, the experimental study is reported which has been conducted on a straight exit laboratory burner with no quarl cone, fuelled by natural gas and air, and fired vertically upwards with the flame stabilized at the end of two concentric pipes with the annulus supplying swirled air and the central pipe delivering the fuel. Two fuel injection typologies, co-axial and radial (i.e., transverse), leading to different mixing mechanisms, have been characterized through different techniques: particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) for a comprehensive analysis of the velocity field, still photography for the detection of flame front and main visible features, and thermocouples for the temperature distribution. Isothermal flow conditions have been included in the experimental investigation to provide a basic picture of the flow field and to comprehend the modifications induced bymore » the combustion process. The results indicated that, although the global mixing process and the main flame structure are governed by the swirl motion imparted to the air stream, the two different fuel injection methodologies play an important role on mixture formation and flame stabilization in the primary mixing zone. Particularly, it has been found that, in case of axial injection, the turbulent interaction between the central fuel jet and the backflow generated by the swirl can induce an intermittent fuel penetration in the recirculated hot products and the formation of a central sooting luminous plume, a phenomenon totally absent in the case of radial injection. (author)« less
Authors:
; ; ;  [1]
  1. Dipartimento di Energetica, Politecnico di Milano, via La Masa 34, 20156 Milano (Italy)
Publication Date:
OSTI Identifier:
20864947
Resource Type:
Journal Article
Resource Relation:
Journal Name: Experimental Thermal and Fluid Science; Journal Volume: 31; Journal Issue: 5; Conference: MCS-4: 4. Mediterranean combustion symposium, Lisbon (Portugal), 6-10 Oct 2005; Other Information: Elsevier Ltd. All rights reserved
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INJECTION; NATURAL GAS; AIR; FLAMES; BURNERS; COMBUSTION; MIXING; TEMPERATURE DISTRIBUTION; JETS; CORRELATIONS; MODIFICATIONS; VELOCITY; GASEOUS WASTES; PARTICLES; STABILIZATION; GAS TURBINES; FURNACES