RU2249118C2 - Low-pressure nozzle and method of fuel atomizing - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to devices and methods of combustion of fuel-air mixture in air-jet engines, small-size gas-turbine engines and gas-turbine plants. Proposed low-pressure nozzle contains annular atomizing edges, body accommodating central air swirler, channel to feed fuel with auger swirler, and outer air swirler arranged on nozzle body. Channel to supply swirled high-pressure air is arranged around fuel feed channel. Two-tier jet outer air swirler is provided with outer and inner inclined holes, air vortex stabilizer and annular outer and inner atomizing edges. Method of fuel atomizing by low-pressure nozzle comes to delivery of fuel and pressure feeding of air through central swirler and outer swirler. Fuel is fed between two swirler air flows formed by central swirler and channel to supply swirler high-pressure air. Flows of air and fuel getting to annular atomizing edges of nozzle form finely dispersed fuel air-mixture. Drops of mixture are atomized by air jets of outer swirler first on its inner annular atomizing edge, and then on outer edge. Said peculiarities of proposed invention increase payload capacity of aircraft, reduce exhaust of harmful substances.

EFFECT: reduced energy losses and expenses.

3 cl, 1 dwg

Description

The invention relates to mechanical engineering, and in particular to devices for burning a fuel-air mixture in air-jet engines, small-sized gas turbine engines and gas turbine installations.

A serious defect encountered in gas turbine engines is not the launch of the combustion chamber in terrestrial and high-altitude conditions. When determining the flow part of the combustion chamber and the nozzle design, the most important are the engine operation at maximum air pressure behind the compressor and the start mode. These modes determine the maximum and minimum fuel pressure. The increase in pressure and air temperature behind the compressor leads to a decrease in the size of the combustion chambers and, in particular, the size of the nozzles and the diameters of their nozzles. However, technological processes, for example coking or simple blockage, do not allow setting nozzle diameters less than d _c = 0.4 mm.

Special studies have shown that an increase in the degree of compression in the compressor and a decrease in the coefficient of excess air at maximum modes leads to an increase in the ratio of fuel consumption at maximum operating mode to its consumption at start-up mode. Due to the fact that the fuel overpressure at the maximum mode is usually limited to 30-50 ati, then at start-up modes it turns out to be less than 0.5 ati, and the nozzles of the traditional schemes provide satisfactory fuel atomization only when the differential pressure of the fuel is greater than 1-1, 5 atmospheres Under these conditions, it is practically impossible to ensure a good fuel atomization and, accordingly, start the chamber. Therefore, for gas turbine engines and, especially, for small-sized gas turbine engines with a high degree of compression, low-pressure nozzles (Δ P≤ 0.5 ati) that are well atomizing fuel are required for starting modes.

Known fuel injector, patent EP No. 0444811 from 02.19.91, which consists of concentrically arranged: central air swirler, a fuel channel with a spray edge and a traditional external blade air swirl with a flow separator. During the operation of such a nozzle, the fuel film is broken by a swirling central air stream supplied from a considerable distance, falling onto a single spraying edge of the nozzle, and tearing off from it into the stream leaving the external swirler.

The disadvantages of this one-stage atomization are: the inability to guarantee good mixing of the fuel with the air supplied through an external swirl and to obtain the required fineness of atomization of the fuel, as well as the inability to reduce the unevenness of the spray pattern in the cross section both in concentration and in droplet size, since this nozzle the scheme is close to traditional; and due to the lack of air flow guides, the geometric stability of the fuel-air torch decreases and its tendency to pulsations increases, which in turn leads to a decrease in the zone of stable operation of the combustion chamber.

The closest technical solution to the claimed and adopted as a prototype is the “Fuel nozzle”, patent RU No. 2107177 dated 07/06/98, which contains a rack with fuel supply openings and a nozzle with a surface for creating a liquid film with a spray edge, as well as an internal and an external air swirl in the form of axial concentric channels with open ends and blades inside, while the surface of the nozzle with a spray edge and the inner surface of the external air swirl are alternately direction at different angles to the axis of the nozzle and are formed by rotation around the nozzle axis of the envelope of the set of geodetic lines intersecting with the axis of the nozzle along the spray edges at an angle equal to the swirl angle of the fuel film.

The disadvantage of this technical solution is that a thin ring swirling film of fuel, falling on the external corrugated channel edges, will not be evenly distributed along the spraying edges, but will merge into thicker jets, located along a larger radius of the corrugated surface, while the edges will be torn off both small and large drops. As a result of this, it is impossible to obtain the required fineness of fuel atomization; there will be no reduction in the non-uniformity of the spray jet in the radial section both in concentration and in droplet size, which will lead to an increase in the propensity of the air-fuel jet to pulsations, which in turn will lead to a decrease in the area of stable operation of the combustion chamber .

The technical task of the proposed technical solution is to ensure high quality atomization of fuel, as well as reducing the level of emission of harmful impurities at the exit of gas turbine engines.

The technical result is achieved by a low-pressure nozzle containing annular spray edges, a housing in which the central air swirl is located, a fuel supply channel having a screw swirl, and an external air swirl is located on the nozzle body, and around the fuel supply channel having a screw swirl a channel for supplying swirling high-pressure air, while the external air swirl is made in two-tier jet and has external and internal inclined holes ment, air vortex stabilizer and annular inner and outer edge of the spray, the fuel spray and the way in which fuel atomization at the injector at the start mode fuel is injected through the channel between the two swirling air jets. Moreover, the air is supplied from the inside using a central swirler, and from the outside using a high-pressure air swirl. The resulting air-fuel mixture is sprayed on the annular spraying edges of the low-pressure nozzle and forms a finely dispersed air-fuel mixture, and the droplets of the resulting mixture are crushed by air jets of an external swirl made by a two-tier jet, first on its inner annular spray edge, and then on the outer one.

The drawing shows a diagram of the inventive low-pressure nozzle.

The low-pressure nozzle consists of a housing 1 with a supply of external high-pressure air 2 to the channel 3 of the air flow swirling by a screw swirl 4 of high-pressure air, an annular spray edge 5 is located at the outlet of channel 3. Also, a fuel supply 6 to the channel is located on housing 1 7 of a fuel swirl with a screw swirler 8 located therein, an annular spray edge 9 is located at the outlet of channel 7. A sealing cylinder 10 is installed inside the housing 1, separating the air supply channel 3 in and the high pressure fuel passage 7. The sealing cylinder 10 is fixed in the housing 1 by means of an axial guide 11 containing a central air swirler 12 and a swirling air supply channel 13 with an edge 14 coaxially disposed with spray edges 9 and 5. The external swirl 15 is made of a two-tier jet, in which there are inner and outer inclined holes 16 and 17, respectively, between their exits there is a spray edge 18, and the stabilizer 19 of the air vortex and the annular outer spray edge 20 are located outside uzhnyh inclined holes 17.

The method of spraying fuel with a low-pressure nozzle is as follows.

Through the central swirl 12 of air in the process of spinning the engine along the channel 13, swirling air is supplied to the edge 14. When certain engine speeds are reached through the fuel supply 6 and the fuel swirl channel 7 through the screw swirl 8, fuel is supplied to the annular spray edge 9, at the same time (in case of difficult starting conditions), by supplying 2 high-pressure external air and the air flow swirl channel 3 through the screw swirl 4, high pressure air is supplied to the spray edge 5. In this case, the fuel is between two swirling air streams formed by the central swirler 12 and screw high-pressure air swirler 4, crushing on two spray edges 5 and 9, in contrast to conventional centrifugal nozzles, where Δ P _t ≤ 1 at a low pressure drop over the nozzle , 5 and a film of fuel forms a fuel bell and coagulates. With the proposed spraying method, the air supplied through the central swirler 12 opens and stabilizes the air-fuel jet, providing it to the inner 18 and outer 20 annular spray edges of the outer swirl 15 made by a two-tier jet. Getting on these last ones, blown by air jets from the outer and inner inclined holes 16 and 17 of the outer swirler 15, the droplets of the air-fuel mixture are further crushed, forming a finely dispersed mixture and thereby reducing the size separation of the droplets. The air and fuel in the nozzle swirl in the swirls in one direction. The stabilizer 19 of the air vortex is used to stabilize the geometric stability of the fuel-air torch.

When starting the engine on the ground, depending on the starting conditions, two nozzle operation modes can be used: the first is the start without high pressure air supply, the second is the start is made while high pressure spray air is supplied and air is supplied through the central channel and air channels swirler. The launch option using high pressure air is only necessary under very difficult launch conditions: high launch altitude and low air temperature. The chamber is launched without high-pressure air supply in autorotation mode and at normal atmospheric air pressure.

Thus, the proposed technical solution allows, upon starting the engine, to provide good atomization of fuel into droplets with a diameter of up to 50-30 μm with a fuel pressure drop of more than 5 kPa, as well as to improve the geometric stability of the fuel-air torch, which allows to expand the area of stable start-up of a gas turbine engine, and also reduces emissions of harmful impurities at the outlet of gas turbine engines and gas turbine installations. Moreover, the inventive low-pressure nozzle containing an external swirl made by a two-tier jet allows the combustion chamber of the air-jet engine to be launched in high-altitude conditions, on the ground and in flight at low differences in fuel pressure Δ P _t <0.5. Due to the low fuel pressure, there is no need to use bulky fuel equipment designed for high pressures.

These features of the proposed technical solutions increase the payload of the aircraft, reduce emissions of harmful impurities, reduce energy losses and, accordingly, reduce economic costs.

Claims (2)

1. A low-pressure nozzle containing annular spray edges, a housing in which the central air swirl is located, a fuel supply channel having a screw swirl, and an external air swirl located on the nozzle body, characterized in that a swirl channel is located around the fuel supply channel high-pressure air, while the external air swirl is made of two-tier jet and has external and internal inclined openings, an air vortex stabilizer, and also a ring s outer and inner edges of the spray. 2. The method of atomization of fuel, carried out by a low-pressure nozzle, which consists in supplying fuel and pumping air through a central swirl and an external swirl, characterized in that the fuel is produced between two swirling air flows formed by the central swirl and a channel for supplying high-pressure swirling air , and the air and fuel flows entering the annular spraying edges of the nozzle form a finely divided air-fuel mixture, while dropping the resulting mixture air jets outer swirler configured bunk jet, first at its inner circumferential edge of the spray, and then - on the outside.