Gas and Liquid Fuel Injection Into an Enclosed Swirling Flow

Abstract

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

Lean Low NOx Primary Zones Using Radial Swirlers

“…The vane angle used, 45°, was the same as that previously used for axial swirlers (9)(10)(11)(12) and was well into the region where the swirl would generate an inner recirculation zone. It was a similar radial swirler design to that currently in use in the Ruston Tornado combustor.…”

Low NOx Primary Zones Using Jet Mixing Shear Layer Combustion

“…Many of the proposed designs involve swirl based systems. 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).…”

Conical Grid Plate Flame Stabilizers: Number and Size of Jet Shear Layers

“…Andrews et al (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) have investigated three lean primary zone designs that have shown promise, all of them based on fuel and air mixing in and flame stabilisation by jet shear layers. The first of these was a simple flat grid plate jet shear layer combustion system (4,5) with each shear layer individually fuelled.…”

“…Swirl systems have also been investigated for their good stability characteristics. With central fuel injection they were found to have poor combustion efficiency, high NOx and no better stability than for the jet shear layer systems (9,10). However, by injecting the fuel at the wall it was found that centrifugal forces acting on the density differences enhanced the mixing and produced improved combustion and lower NOx (11,12).…”