RU2802115C1 - Gas turbine combustion chamber - Google Patents

Abstract

FIELD: gas turbine plants.

SUBSTANCE: invention can be used in the combustion chambers of aircraft gas turbine engines. The combustion chamber of the gas turbine plant contains a flame tube with a front device, an additional front device installed on the wall of the flame tube. The additional front device consists of a body with outer and inner walls, with a mixing chamber installed between them and interconnected pylons. The pylons are wedge-shaped in cross section and with a flat wall, installed evenly around the circumference with gaps between them. The outer wall of the housing contains a fuel cavity communicated with the fuel supply channels. The mixing chamber is connected at the inlet with channels for supplying air through the gaps between the pylons, and at the outlet it is in communication with the channel for supplying the air-fuel mixture to the flame tube. The mixing chamber is equipped with a fairing installed on the outer wall of the body of the additional front device. The wedge-shaped pylons face the mixing chamber with their flat wall; a calibrated hole for fuel supply is made in the flat wall of each pylon. The pylons are provided with a channel communicated on one side with the fuel cavity, and on the other side with the mixing chamber through a calibrated hole.

EFFECT: increased efficiency and reliability of the combustion chamber of a gas turbine plant in the conditions of its operation at high temperatures and air pressure at the inlet to the combustion chamber, expansion of the range of low-emission operation of the gas turbine combustion chamber.

3 cl, 3 dwg

Description

The invention relates to gas turbine plants (GTP) and can be used in the combustion chambers of aircraft gas turbine engines.

One of the most important tasks in the development of the combustion chamber is to reduce the level of emissions of harmful substances that pollute the atmosphere. The focus is on reducing the concentration of nitrogen oxides (NO _x ) and carbon monoxide (CO) in the combustion products. High emission of these substances is typical for diffusion combustion chambers of any thermal engine running on natural hydrocarbon fuel. When creating a low-emission combustion chamber (MECS), the main problem is to achieve efficient pre-mixing of fuel with air and organize the supply of lean homogenized fuel-air mixtures (FA) into the chamber with the achievement of stable combustion at a minimum, but sufficient for efficient combustion of the residence time of combustion products in areas with high temperatures. Under conditions of high-temperature gas turbines, in order to expand the range of low-emission operation without the use of special control methods in throttle modes, leading to a decrease in the efficiency of gas turbines in these modes, as well as to reduce emissions in the most heat-intensive operation modes, two-zone combustion schemes of lean premixed mixtures are used. Moreover, additional fuel combustion zones in the MEKS are located downstream of the main zones, closer to the end of the flame tube.

A low-emission combustion chamber with a two-zone scheme for organizing low-emission fuel combustion is known, which contains a flame tube with a front device, an additional front device mounted on the wall of the flame tube, consisting of external and internal walls, with a mixing chamber installed between them (Rolls-Royce Industrial Trent: combustion and other technologies / C. Barkey, S. Richards, N. Harrop, P. Kotsiopriftis, R. Mastroberardino, D. Squires, T. Scarinci // Proceedings of International Sumposium of Air Breathing Engines, 1999, Paper No. ISABE 997285 ). The additional front device consists of channels for supplying air and channels for supplying fuel to the mixing chamber, as well as a system of channels for supplying jets of fuel assemblies from the mixing chamber at an angle to the walls of the flame tube for their subsequent combustion in the second MEKS combustion zone. In this case, the system for mixing air and fuel jets is an annular expanding channel for supplying an air flow and an annular channel for supplying fuel jets perpendicular to the air flow through a number of holes located along the air channel. At the exit from the mixing chamber, the FA flow is divided by means of separate tubes into a number of smaller flows, which feed the FA jets at an angle to the walls of the flame tube for their combustion in the additional combustion zone.

A disadvantage of the well-known two-zone MEX is the complexity of the design and the length of the channels for supplying fuel assemblies from the mixing chamber to the flame tube, which leads to an increase in boundary layers, to separation of the flow from the walls and periodically leads to ignition of the fuel assemblies or flashback of the flame from the flame tube into the mixing chamber, which is accompanied by their overheating or burnout.

A low-emission combustion chamber with two zones of kinetic combustion is known, which contains a flame tube with a front device, an additional front device mounted on the wall of the flame tube (RU 2753202, 2020). The combustion chamber consists of modular elements arranged in a circle concentric to the engine rotor outside with respect to the last stages of its compressor. Inside each modular element is installed: a front device with concentrically located internal diffusion pilot burner with an adjustable fuel supply and an external main pre-mixing burner with a radial bladed air swirler and with two - main and corrective - independent adjustable fuel supply systems, the outlet channels of which are located in the interblade cavities of the specified bladed air swirler, as well as a flame tube adjacent to the front device with a flame section and a gas outlet section.

Intensive swirling of the fuel assembly flow in the additional front device, as well as an increase in its cross-sectional area at the outlet, lead to the formation of a reverse current zone (RFC) with an increased residence time and ignition of the fuel assembly in this zone, the formation of which begins immediately after the swirler inside the additional front device, and not in the flow of combustion products of the primary zone, which degrades the quality of mixing fuel assemblies before the start of the combustion process and increases the emission characteristics.

Intensive swirling of the FA flow and expansion of the area of the outlet channel of additional front devices also lead to a decrease in the depth of penetration of the FA flow into the main zone combustion products flow and to the distribution of high temperatures of the combustion products of the additional zone near the walls of the flame tube, which causes overheating of the walls behind the additional front devices and worsens the temperature fields in front of the turbine, because the maximum temperature of the combustion products is formed near the walls of the flame tube, and not in the center of the flow.

The closest analogue, selected as a prototype, is a multi-fuel combustion chamber of a gas turbine plant, which contains a flame tube with a front device, an additional front device mounted on the wall of the flame tube, consisting of a housing with outer and inner walls, with a mixing chamber installed between them and interconnected by pylons made wedge-shaped in cross section and with a flat wall, installed evenly around the circumference with gaps between them, and the outer wall of the housing contains a fuel cavity in communication with the fuel supply channels, and the mixing chamber is in communication with the air supply channels through gaps between the pylons, and at the outlet it communicates with the channel for supplying the air-fuel mixture to the flame tube (US 9400113, 2016). The channels for supplying fuel to the additional front device are located on the surface of the body in sections between the pylons and supply fuel jets perpendicular to the air flows formed between the pylons of the additional front device. The fuel assembly is formed in the mixing chamber by the interaction of fuel and air jets. For transporting fuel assemblies to the flame tube, the fuel assemblies supply channel is used, which is fixed on the inner wall of the additional front device. The quality of mixing and the uniformity of the fuel concentration fields are largely determined by the depth of penetration of fuel jets flowing from the walls of the housing into air flows. With an increase in the operating modes of the gas turbine, the fuel consumption in the additional front device and the depth of penetration of the fuel jets into the air flows also increase. Optimal for mixing is the depth of penetration of fuel jets to half the height of the pylons of the additional front device.

In the well-known combustion chamber, there is a sharp turn in the direction of the flow of fuel assemblies from radial to axial by 90 degrees, which leads to separation of the fuel assemblies flow from the walls and the formation of a CAP, which can cause fuel assemblies to ignite inside the additional front device and burn out. At the same time, the supply of fuel jets into air flows from the mixing chamber in the presence of two fuel supply subsystems does not provide a high quality of mixing in all modes and creates uneven radial and circumferential fields of fuel concentrations, which leads to an increase in emission characteristics.

The technical problem solved by the claimed invention is to reduce the concentration of nitrogen oxides and carbon monoxide in the combustion products.

The technical result provided by the invention is to increase the efficiency and reliability of the combustion chamber of a gas turbine plant under conditions of its operation at high temperatures and air pressure at the inlet to the combustion chamber, as well as to expand the range of low-emission operation of the gas turbine combustion chamber.

The claimed technical result is achieved due to the fact that in the combustion chamber of a gas turbine plant containing a flame tube with a front device, an additional front device mounted on the wall of the flame tube, consisting of a housing with outer and inner walls, with a mixing chamber installed between them and interconnected pylons made wedge-shaped in cross-section and with a flat wall, installed evenly around the circumference with gaps between them, and the outer wall of the housing contains a fuel cavity communicated with the fuel supply channels, the mixing chamber is connected at the inlet with the air supply channels through the gaps between the pylons, and at the outlet it communicates with the channel for supplying the air-fuel mixture to the flame tube, according to the proposed technical solution, the mixing chamber is equipped with a fairing installed on the outer wall of the body of the additional front device, the wedge-shaped pylons face the mixing chamber with a flat wall, a calibrated hole is made in the flat wall of each pylon for fuel supply, the pylons are equipped with channels communicated on one side with the fuel cavity, and on the other side with the mixing chamber through a calibrated hole.

The significance of the distinctive features of the claimed technical solution is confirmed by the fact that only the totality of all design features describing the invention is sufficient to solve the specified technical problem and achieve the claimed technical result.

Significant features may develop and continue, namely:

The width of the flat wall B of the pylons can be determined from the condition

B \u003d 10 ^-4 p ^-1.8 e ^{29600 / RTv} _,

and the total area of all gaps F ₃ for the passage of air between the pylons can be determined from the expression:

in this case, the distance between the pylons δ is selected from the condition:

δ=(0.15-0.25) V,

Where:

B - width of the pylon of the additional front device, m;

T _B - air temperature at the inlet to the additional front device, K;

R - gas constant for air, J/kg K;

p is the air pressure at the inlet to the additional front device, Pa;

e is the Euler number;

G _в2 - total air flow through the gaps between the pylons of the additional front device, kg / s;

N _DFU - the number of selected gaps between the pylons of the additional front device;

ρ _in - air density at the entrance to the additional front device, kg/m ³ ;

M _B - Mach number in a narrow section between the pylons of the additional front device;

a is the speed of sound in the air flow between the pylons of the additional front device, m/s;

F ₃ - the total area of all gaps for the passage of air between the pylons in the additional front device, m ² ;

δ - minimum distance between the pylons of the additional front device, m.

The minimum diameter D of the channel for supplying the air-fuel mixture at the outlet can be determined from the expression:

The present invention will be explained by the following detailed description of the design of the combustion chamber of a gas turbine plant and its operation with reference to the illustrations presented in Figs. 1-3 where:

in fig. 1 shows a longitudinal section of the gas turbine combustion chamber with an additional front device and a flame tube;

in fig. 2 - general view of the additional front device;

in fig. 3 is a section A-A of the additional front device in FIG. 2.

The combustion chamber of a gas turbine plant contains a flame tube 1 with a front device 2, an additional front device 3 mounted on the wall of the flame tube 1 (Fig. 1). Additional front device 3 consists of a body with outer 4 and inner 5 walls, with a mixing chamber 6 installed between them and interconnected pylons 7 (Fig. 2). The outer wall 4 of the body of the additional front device 3 contains the fuel cavity 8, communicated with the channels 9 for supplying fuel. The pylons 7 are wedge-shaped in cross section with a flat wall 10 and are installed evenly around the circumference with gaps 11 between them (Fig. 3). The width of the flat wall B of the pylons 7 can be determined from the condition:

B \u003d 10 ^-4 p ^-1.8 e ^{29600 / RTv}

and the total area of all gaps 11 F ₃ for the passage of air between the pylons 7 is determined from the expression:

in this case, the distance between the pylons 7 δ is selected from the condition:

δ=(0.15-0.25) V.

Wedge-shaped pylons 7 face the mixing chamber 6 with their flat wall 10. A calibrated hole 12 for fuel supply is made in the flat wall 10 of each pylon 7. The pylons 7 are provided with a fuel supply channel 9 connected on one side with the fuel cavity 8, and on the other side with the mixing chamber 6 through a calibrated hole 12. at the outlet it is connected with the channel 14 for supplying the air-fuel mixture to the flame tube 1. The minimum diameter D of the channel for supplying the air-fuel mixture at the outlet is determined from the expression:

The mixing chamber 6 is equipped with a fairing 15 installed on the outer wall 4 of the body of the additional front device 3. The combustion chamber of the gas turbine plant contains a manifold 16 for supplying fuel to the main front device 2 and a manifold 17 for supplying fuel to the additional front device 3, and also has a main combustion zone 18 and additional combustion zone 19.

The combustion chamber of a gas turbine plant operates as follows. At the minimum low-emission mode N=50%, the main fuel is supplied through the fuel supply manifold 16 to the front device 2. The combustion process is implemented only in the main combustion zone 18, maintaining the temperature of the combustion products in the main zone in the range of 1500-1700K. Only additional air flow passes through the additional front device 3, which, entering the flame tube 1, reduces the gas temperature at its outlet and at the turbine inlet.

When power is set (at N≥50%), additional fuel through the fuel cavity 8 and fuel supply channels 9 begins to be supplied to the additional front device 3 while maintaining a constant fuel consumption in the front device 2 and the temperature in the main combustion zone 18. Fuel through the fuel cavity 8 enters the channels 9 for supplying fuel located in the pylons 7, then through the calibrated holes 12 in the SOT, formed during the flow around the pylons 7 with air jets formed between the pylons 7 when air flows into the inlet to the additional front device 3. Air jets formed during the passage of air in the gaps 11, 5 wide between the pylons 7, they form, when flowing around the pylons 7, a ZOT with high turbulent characteristics. The interaction of fuel jets supplied from the flat walls 10 of the pylons 7 in the ZOT with air flows flowing in these zones, a rich homogenized fuel assembly is formed. This rich fuel assembly is ejected from the FA into the air jets flowing around the pylons 7, mixes with the air in these jets, and the fuel concentration in the fuel assembly decreases below the stoichiometric level, which creates a lean homogenized fuel assembly at the outlet of the mixing chamber 6. This poor homogenized FA is sent to the flame tube 1 with the help of the channel 14 for supplying the air-fuel mixture and, after mixing with the high-temperature combustion products of the main combustion zone 18, ignites from them and burns out, creating an additional combustion zone 19.

Maintaining low concentrations of NO _x and CO at low throttle modes N=50% is implemented due to the optimal and relatively low temperature regimes of combustion (1500-1700 K) of poor homogenized fuel assemblies in the main combustion zone 18 of the combustion chamber, which also provide conditions for rapid ignition of poor fuel assemblies additional combustion zone 19. At GTP operating modes N≥50%, low emission characteristics are ensured when organizing combustion in the main 18 and additional 19 zones due to the high residence time of combustion products in the additional high-temperature combustion zone 19. At the same time, low levels of NO _x and CO in the additional combustion zone 19 are implemented due to the good quality of mixing of fuel and air in the additional front device 3 and the formation of a homogeneous lean fuel assembly at the outlet of the additional front device 3. Low emissions of _NOx and CO in the additional combustion zone 19 are ensured by minimizing the residence time combustion products in this zone, which is implemented in the absence of flow swirling in the additional front device 3, which can lead to the formation of a HFZ with long residence times in the jet at the outlet of the additional front device 3. In addition, the reduction of NO _x and CO emissions in the additional combustion zone 19 is associated with the location of this zone at the end of the flame tube 1.

Expansion of the range of low-emission operation of the combustion chamber is achieved by transferring the combustion of a part of the fuel from the main zone and the THB, which has a long residence time of combustion products in this zone and leads to a high rate of increase in NO _x and CO emissions with an increase in gas temperature in this zone, into the gas flow an additional combustion zone characterized by a short residence time and a low rate of increase in the concentration of NO _x and CO with an increase in the temperature of the combustion products.

Thus, the presence of a fairing in the mixing chamber, installed on the outer wall of the body of the additional front device, a calibrated hole in the flat wall of each pylon and a channel connected on one side with the fuel cavity, and on the other hand with the mixing chamber through a calibrated hole, reduces the concentration nitrogen oxides and carbon monoxide in the combustion products and thereby increases the efficiency and reliability of the combustion chamber of a gas turbine plant under conditions of its operation at high temperatures and air pressure at the inlet to the combustion chamber, and also provides an extension of the range of low-emission operation of the gas turbine combustion chamber.

Claims (22)

1. The combustion chamber of a gas turbine plant, containing a flame tube with a front device, an additional front device mounted on the wall of the flame tube, consisting of a housing with outer and inner walls, with a mixing chamber installed between them and interconnected pylons made of a wedge-shaped shape in transverse section and with a flat wall, installed evenly along the circumference with gaps between them, and the outer wall of the housing contains a fuel cavity in communication with the fuel supply channels, the mixing chamber is connected at the inlet with the air supply channels through the gaps between the pylons, and at the outlet it is connected with the supply channel air-fuel mixture into the flame tube, characterized in that the mixing chamber is equipped with a fairing installed on the outer wall of the body of the additional front device, the wedge-shaped pylons face the mixing chamber with a flat wall, a calibrated hole for fuel supply is made in the flat wall of each pylon, the pylons are equipped with a channel, communicated on one side with the fuel cavity, and on the other side with the mixing chamber through a calibrated hole. 2. The combustion chamber of a gas turbine plant according to claim 1, characterized in that the width of the flat wall B of the pylons is determined from the condition: B \u003d 10 ^-4 p ^-1.8 e ^{29600 / RTV} _, and the total area of all gaps F ₃ for the passage of air between the pylons is determined from the expression: in this case, the distance between the pylons δ is selected from the condition: δ=(0.15-0.25) V, Where: B - width of the pylon of the additional front device, m; T _in - air temperature at the inlet to the additional front device, K; R - gas constant for air, J/kg K; p is the air pressure at the inlet to the additional front device, Pa; e is the Euler number; G _в2 - total air flow through the gaps between the pylons of the additional front device, kg / s; N _DFU - the number of selected gaps between the pylons of the additional front device; ρ _in - air density at the entrance to the additional front device, kg/m ³ ; M _B - Mach number in a narrow section between the pylons of the additional front device; a is the speed of sound in the air flow between the pylons of the additional front device, m/s; F ₃ - the total area of all gaps for the passage of air between the pylons in the additional front device, m ² ; δ - minimum distance between the pylons of the additional front device, m. 3. The combustion chamber of a gas turbine plant according to claim 1, characterized in that the minimum diameter D of the air-fuel mixture supply channel at the outlet is determined from the expression: