JPS622216B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to combustors used in land-based turbines, and more particularly, the present invention relates to combustors for use in land-based turbines, and more particularly, the present invention relates to combustors for use in land-based turbines, and more particularly, the present invention relates to combustors for use in land-based turbines. The present invention relates to a catalytic combustor that is required to be substantially uniform. Premixing of fuel and air in a premix combustor is necessary to extend combustor life, increase combustor efficiency, and reduce emissions through proper combustion operating temperatures and proper reactions. Catalytic combustors are a practical commercial option for operating combustion turbines with low pollution, i.e., low _NOx , in power plants and other land-based applications.
Proper catalytic combustion, in particular, requires substantially uniform premixing of fuel and air within the mixing region of the combustor. Given the compressor exhaust pressure levels in most engine designs, some fuel premixing is necessary for proper catalytic combustion. A catalytic combustor may include a tubular enclosure having a primary combustion zone, followed in sequence first by a secondary fuel injection and mixing zone and finally by a catalytic zone.
The primary combustion zone operates, for example, during startup when operating temperatures do not adequately sustain catalytic combustion. During the catalytic combustion phase of operation, secondary fuel is injected into the mixing region where it mixes with air for transport through the catalytic region and into the flow channel. The secondary fuel injector is typically disposed circumferentially surrounding the mixing region, and the secondary fuel injector is
The secondary fuel injector may inject fuel radially inward at 90 degrees or other predetermined angle into the mixing region of the combustor. Also, the fuel must preferably be completely evaporated before entering the catalyst, which requires the fuel nozzle to create very fine particulates that can be quickly evaporated. Particulates can be produced either by creating a very high pressure drop across the fuel nozzle (pressure atomization), by using a small amount of high-energy atomizing air (air assist), or by using a relatively large amount of low-energy atomizing air ( air blast). In either case, the momentum of the resulting fuel spray is very large. In fact, the momentum of the fuel spray is so great with respect to the momentum of the counterflow air inside the combustor that the fuel tends to pass through to the center (axis) of the combustor. This effect creates a rich core of fuel, ie, a fuel-air ratio profile with only one central peak at either end of the nominal diameter of the cross-section of the combustor mixing region. The fuel-air ratio is greatest axially at the fuel injection surface or region and decreases in the radially outward direction. As the mixture flows downstream through the mixing region, additional mixing action takes place to somewhat smooth the fuel-air ratio. However, fuel penetration in the injection region has generally resulted in axial fuel concentrations that are too high to utilize downstream mixing to provide a substantially uniform fuel-air ratio distribution at the catalyst inlet face. In accordance with the invention, a combustor, by means of a structure that aids in the deflection of the injected fuel in the axial direction, resulting in a uniform mixture of fuel and air in a mixing region immediately upstream of the region in which combustion occurs; An improved performance is obtained especially in catalytic combustors. Preferably, the structure, airflow directing device, includes a plurality of circumferentially distributed air holes in the combustor wall upstream of the fuel injector such that the incoming airflow is angled downstream. The incoming airflow has a high velocity due to the pressure drop at the combustor wall, so that the internal gas flow axially deflects the injected fuel to substantially alter the fuel-air ratio profile at the catalyst inlet face. It greatly helps in uniformity. Preferred embodiments of the invention will now be described with reference to the accompanying drawings. In particular, the catalytic combustor 10 shown in FIG. 1 is for land-based combustion turbines, typically used in power generation and other industrial plants. Combustor 10 includes a tubular structure consisting of a generally tubular sidewall 12 having sequential circumferential rows of openings or holes 14, 16 for the introduction of air used in the combustion process. In the head 18 of the combustor 10, a primary fuel nozzle 20 introduces fuel into the primary region 2 to generate the energy required for start-up until operating conditions are such that sustaining catalytic combustion.
Burn it in step 2. In addition, the primary fuel nozzle 2
0 during catalyst operation to provide the preheating necessary to maintain the gas temperature at the catalyst inlet face (mixing zone outlet) 24 at the temperature required for efficient catalytic combustion (i.e., approximately 982-1065°C). Supply some fuel for the next combustion. 1 included in the entire operation of the combustor
The amount of combustion of the following fuel is such that the amount of _NOx produced is sufficiently lower than environmental standards. The outer end 26 of the side wall 12 is open to the outside and connected to a conventional catalytic element 28 of honeycomb structure. The outlet 30 of the catalyst region is also connected to an intermediate duct (not shown) that guides the hot gas to a turbine (not shown).
It is connected to the. Secondary fuel is delivered to the combustor 1 during the zone combustion phase of operation by a set of circumferentially spaced sparge devices or nozzles 32 at the downstream end of the primary combustion zone 22.
Injected within 0. Air may or may not be introduced into the combustor 10 at a location of the nozzle. A combustor mixing region 34 between the primary region and the catalytic element 28 provides for mixing of the secondary fuel and air before entering the catalytic element 28 . This region 34 is called the mixing region, in which combustion is avoided and does not occur since flashbacks would damage the combustor and/or the catalytic element 28. As will be fully explained with reference to FIGS. 2 and 4,
Airflow directing devices or holes 36 arranged in a circumferential row immediately upstream of the secondary fuel injection in the combustor sidewall are angled to admit air in a downstream direction, and are angled to admit air in a downstream direction. Provides uniform mixing of secondary fuel and air. As shown enlarged in FIG. 2, an angled tube 37 is provided to assist in deflecting the secondary fuel to create a substantially uniform fuel and air mixture relative to the catalytic element 28. It is provided inside and gives an inclination to the air flow (booster air flow) 39 passing through the air hole 36. As shown in FIG. 2, the angled airflow 39 clearly assists the crossflow air 41 in deflecting the fuel spray by the secondary fuel nozzle 32. In FIG. 3, an alternative embodiment is shown in which an external tube 33 performs a similar fuel and air mixing function. Generally, by utilizing the pressure drop across the combustor sidewalls 12, the fuel and air distribution is controlled and a peaked fuel and air mixing situation is avoided. This pressure drop is typically large enough that the velocity of the air entering the combustor 10 through the air vents is greater than the velocity of the air already flowing inside the combustor 10. Therefore, the momentum flux (momentum per unit area in unit time) of the incoming air increases. A recessed air hole or tube positioned just upstream of the fuel spray and sloped downstream avoids a non-uniform fuel-air mixing situation where the high velocity of air entering through the air hole peaks in the center. Become the root. In practice, the angle of the air holes can be varied to control the mixing profile of fuel and air entering the catalytic element 28. With the angled air entry configuration described above, sidewall injection of fuel into the catalytic combustor can provide the required uniformity of the fuel and air mixture approaching the catalyst. As shown in the test results in FIG. 4, the catalyst outlet temperature, which reflects the fuel-air ratio profile at the catalyst inlet, is relatively uniform in the embodiment of the present invention compared to the prior art distribution with a peak in the center. various distribution curves 44
(i.e., a generally flat shape). Fifth
The figure shows the structure used in the prior art during testing, while FIG. 2 shows the structure of the invention used in testing. The angled airflow in the structure of the present invention is the main improvement. The improvement in mixing may be as a result of spraying the fuel with an angled air stream into a favorable mixing location, or perhaps as a result of air-boosted turbulent kinetic energy in the region where the secondary fuel spray enters the combustor. , seems to happen. The conditions applicable to the test shown in Figure 4 are as follows. 【table】

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway cross-sectional view of a catalytic combustor constructed according to the present invention, FIG. 2 is an enlarged cross-sectional view of a portion of FIG. 1, and FIG. a sectional view corresponding to FIG. 2 of another embodiment having a section;
FIG. 4 is a curve diagram showing test results obtained using the present invention in comparison with the prior art, and FIG. 5 is a cross-sectional view of the prior art used to obtain the comparative test results. 10... Turbine combustor, 12... Side wall of tubular structure, 14, 16... Opening, 20... Primary region,
24... Outlet of mixing region (catalyst inlet surface), 32...
... Spraying device (nozzle), 34 ... Mixing area, 36
...Air flow directing device (air hole), 33, 37...
Air flow directing device (cylindrical part), 39... Booster air flow, 41... Cross flow air.

Claims (1)

[Claims] 1. A tubular structure having a side wall with an opening,
a downstream mixing region in which a mixture of fuel and air spreads for downstream combustion; and an upstream primary region, through which air enters the primary region to inject downstream secondary fuel. a tubular structure for creating an axial primary air flow that mixes with the primary air flow; passing radially inwardly through the sidewall at a location between the mixing region and the primary region to mix with the primary air flow; a dispersion device for dispersing fuel in fine particles that are prone to rapid evaporation; and a dispersion device for dispersing fuel in fine particles that are prone to rapid evaporation; an air flow directing device for directing a booster air flow having a higher velocity than the crossflow air downstream at a predetermined angle with respect to the axis of the tubular structure to promote mixing of fuel and air; Turbine combustor.