The Influence of Premixed Combustion Flame Stabilizer Geometry on Flame Stability and Emissions

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

1985

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Emission results are presented for a jet shear layer flame stabiliser design consisting of a 90° conical flame stabiliser with an array of holes and a central annular vaporiser fuel injection system. This design was tested with premixed propane and air and with direct propane injection into the vaporiser at two blockages and approach velocities. The results showed that an array of jet shear layers could be fuelled by a single fuel injector without incurring excessive NOx emissions. An increase in the primary zone residence time was found to result in an improved combustion efficiency, with no increase in NOx, provided that the stabiliser blockage was increased to maintain the pressure loss.

Section: Premixed Combustionmentioning

confidence: 99%

“…This indicates that the stabiliser aerodynamics are good. Previous work has shown that premixed combustion with large recirculation zone systems such as baffles (1) or swirlers (6) result in a high combustion inefficiency and hence an inadequate basis for the design of weak primary zone systems.…”

Section: Premixed Combustionmentioning

confidence: 99%

Conical Grid Plate Flame Stabilizers for Combustor Primary Zones

Ali

Volume 2: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

1985

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“…The 76 mm diameter combustion test facility has been described by Al-Dabbagh and Andrews (18). It consists of an air supply from a fan, venturi flow metering, electrical preheater, 1.5 m long 76 mm diameter approach pipe, flange mounted swirler with integral central fuel injector, 330 mm long 76 mm diameter combustor and an exhaust system with a flame observation window located a short distance from the combustor exit.…”

Section: Combustion Test Equipment and Conditionsmentioning

confidence: 99%

Gas and Liquid Fuel Injection Into an Enclosed Swirling Flow

Ahmad

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

1984

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A swirler with good premixed performance has been tested with direct central propane injection and with direct central kerosene and gas oil injection using the swirler air for atomisation. The results have been compared with non swirling flow systems at the same test conditions. Direct propane injection results in a major extension of the stability limits compared with the premixed situation, but with liquid fuel injection the stability limits are generally worse than for premixed fuel and air. It is argued that the cause of this is the action of the centrifugal forces on the liquid droplets in the swirl flow which results in vaporisation in the outer swirl flow and weaker mixtures in the core recirculation region than for propane injection. The gas composition results support this conclusion. Direct propane injection caused a deterioration in the combustion efficiency and a large increase in NO x . The poor stability limits with liquid fuels prevented a high combustion efficiency and low NO x situation from being achieved. A comparison of the performance with non swirling systems showed that all emissions were higher with swirl for propane but that the swirler may have some advantages for liquid fuels.The SW3 swirl number was sufficiently low to ensure a good combustion efficiency, whilst being high enough to ensure a central recirculation zone (5,6). The full swirler design details are given in Table 1 and the test geometry is shown in Fig. 1. The premixed

“…Although these have some advantages, Ahmad et al (5)(6)(7)(8)(9) have shown that the NOx emissions and combustion efficiency of weak mixtures is not as good as in the present jet shear layer designs. The authors have extensively investigated various designs of jet shear layer fuelled systems for low emissions wide stability combustor primary zones (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). This work has concentrated on investigating factors that influence mixing, especially the number of air and fuel injection points (13) and the influence of pressure loss (12,14,15,19).…”

Section: Introductionmentioning

confidence: 99%

“…In the present work the -Jet Mix" design of interacting radial and axial jets was used (10,11,(16)(17)(18)(19)(20). This has been shown to have a good premixed performance (10) with a capability for direct fuel injection with the radial air that extends the stability whilst retaining low NOx emissions (11,(18)(19)(20).…”

Section: Introductionmentioning

confidence: 99%

Low NOx Primary Zones Using Jet Mixing Shear Layer Combustion

Hussain

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations

Cheung

et al. 1988

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An interacting radial and axial multi jet shear layer combustion system is described that has the rapid fuel and air mixing characteristics necessary for low NOx emissions. The radial jet has the fuel mixed with a proportion of the total primary zone flow and a 30% proportion was investigated. This radial jet was fuel rich at most primary zone operating conditions and ensured a flame stability far superior to the premixed situation. The scale up of the design from a 76mm to a 140mm diameter combustor was investigated. It was demonstrated that the distance the radial jet travelled before encountering the rapid mixing with the axial jets, had a strong influence on the combustion efficiency and NOx emissions. For both the 76 and 140mm combustors it was shown that the NOx emissions with propane were 50% greater than those for natural gas. It was also demonstrated that the low NOx emissions of the 76mm system were retained in the larger combustor with the same single central fuel injector design. There was a significant increase in NOx for some 140mm combustor configurations, but the emissions corrected to 15% oxygen below 10ppm were demonstratred, with a high combustion efficiency. The design thus demonstrated, in a practical combustor size, the potential for a dry solution to the NOx emissions problem of natural gas fired industrial gas turbines.