Ongoing Development of a Low Emission Axisymmetric Annular Vortex Combustor for an Industrial Gas Turbine

Abstract

An axisymmetric annular vortex combustor was tested atmospherically to determine the feasibility of meeting the 1977 proposed EPA emission standards for stationary gas turbines. Flame stabilization was achieved solely by swirl induced recirculation without the jet assisted recirculation of conventional practice. Buoyancy forces are used to enhance or diminish turbulent mixing. It was found that by uniformly mixing gaseous fuel and air prior to combustion and burning fuel lean it was possible to meet the proposed emission standards. The resultant narrow range of flame stability necessitated fuel staging for light-off and off-design operation. Fuel staging was achieved by stratified charge combustion (diffusion flame). Changes in combustor geometry were made and extensive traversing of the flame zone was carried out to measure concentrations of chemical species.

Performance Testing of a Low Emissions, Natural-Gas Fired, Small Gas Turbine Combustor

“…The combustor development effort extended earlier work that had established a baseline of design and performance information for lean-premixed, natural gas combustion (Smith, 1987;Smith, 1986, andSood, andShekleton, 1980). These earlier studies had documented the ability to achieve ultra-low NOx emissions with lean-premixed combustion when firing natural gas in a test rig environment.…”

Gas and Liquid Fuel Injection Into an Enclosed Swirling Flow

“…However, generally only a small portion of the total combustor air flow passes through the swirler, usually approximately 10%, with the major proportion of the primary zone air entering through radial jets (6). Many recent experimental combustor designs for low emissions and future fuels have advocated the use of swirl flame stabilisation with the majority of the combustor air flow passing through the swirler (8)(9)(10)(11)(12). The present work attempts to assess whether these swirl dominated systems have definite advantages over the aerodynamically simpler grid plate stabilised systems which have been investigated by one of the authors (13,14).…”

Emissions From Enclosed Swirl Stabilised Premixed Flames

“…In recent years the problem of emissions from gas turbines has led to the use of arrays of swirlers, each with its own fuel injector, as a basis for the primary zone aerodynamics (2). Alternatively, large single swirler and fuel injector combinations have been proposed, generally for industrial gas turbines, for the primary zone (3,4). This paper presents the combustion efficiency and emissions results for four enclosed axial swirler designs and compares the results with those of Al-Dabbagh and Andrews (5) for a non-swirling flow grid plate stabilised flame at equivalent test conditions.…”

“…Ahmad and Andrews (7) have identified one of the major influences of D/d to be that due to the centrifugal forces on the spread of combustion. Large D/d ratios enable a large initial corner recirculation zone to be established which acts as an ignition source and centrifugal effects force the light hot gases inwards and the heavier burnt gases outwards and a rapid flame spreading occurs (4,9). However, with small D/d ratios the corner recirculation is small and with high swirl numbers may not exist.…”