GB1352823A - Combustion apparatus - Google Patents

Abstract

1352823 Gas turbine combustion apparatus GENERAL MOTORS CORP 11 Jan 1973 [25 Jan 1972] 1472/73 Heading F1L To reduce formation of nitrogen oxides in a gas turbine combustion apparatus 4 at least some of the combustion gases are recirculated from a downstream to an upstream region of the apparatus through an annular duct 49, Fig. 1. defined between the outer wall 36 of a doublewalled combustion liner 32 and a surrounding casing 22. The latter is itself surrounded by a casing 11 to define a dilution air duct 30 and by an outer housing 2 defining a primary air space 3. The upstream end of the combustion region is defined by a front plate assembly 19 consisting of axially spaced plates 50, 52 mounted at their centres on a ferrule 51 surrounding fuel nozzle 20. Plate 52 has angularly spaced ports (59), Fig. 4 (not shown) which can be obturated by an angularly movable valve plate 62, Figs. 1, 2, having corresponding ports 69 so as to control the flow of primary air. Valve plate 62 also has further ports 63 which co-operate with, but do not throttle air-flow through, corresponding ports 60 in plate 52. The primary air-flow after passing through the control ports flows radially outwardly in the space between plates 50, 52, over an intermediate ring 76 supported from plate 50 by fins 77, 78, Fig. 5, and thence into angularly spaced tubes 80 containing liners 94 supported by brackets 95. The downstream ends of tubes 80 open into an annular manifold 34 which has apertures (88, 90, 91), Fig. 3, 6 (not shown) discharging primary air into duct 40 defined between the walls 36, 38 of combustion liner 32. An annular nozzle 42 at the downstream end of the latter discharges the primary air, the curved portion 35 of wall 36 tending by virtue of the Coanda effect to cause the air to flow into recirculation duct 49 together with entrained combustion gases. The latter are cooled as they flow forwardly by heat exchange with primary air in duct 40 and with dilution air which has flowed into duct 30 through ports 27, 28 in casing 11. The recirculated mixture of cooled gases and primary air flows through the spaces between adjacent tubes 80 and into the area of fuel nozzle 20 so as to reduce the oxygen concentration and temperature in the combustion zone and thus the formation of nitrogen oxides. The combustion gases which are not recirculated leave through outlet 7 and are cooled by dilution air entering from duct 30 through ports 100. Means may be provided to control air-flow through the latter. To improve heat transfer, surfaces of plate 50, tubes 80, walls 36, 38 and casing 22 are roughened by etching nets of intersecting grooves (98), Fig. 13 (not shown). Casings 11, 22 are supported within housing 2 by angularly spaced pins 16 with provision for thermal expansion. Spacing ribs 31, 39 are provided on casing 22 and wall 38 respectively.