Combustion chamber fuel injection and oil-gas mixing system suitable for low-temperature environment

Abstract

The invention discloses a combustion chamber fuel injection and oil-gas mixing system suitable for a low-temperature environment, and belongs to the field of combustion chambers of gas turbines, the combustion chamber fuel injection and oil-gas mixing system comprises a flame tube, a centrifugal nozzle and a two-stage cyclone which are coaxially arranged, after fuel is atomized through the centrifugal nozzle and enters, the fuel is further atomized through rotational flow of an inner ring of the two-stage cyclone and enters the flame tube, and the fuel is injected into the combustion chamber through the centrifugal nozzle. External high-pressure air is swirled through the outer ring of the two-stage swirler to form swirling air, and internal fuel spray is crushed, atomized and mixed; a venturi tube is arranged at the end, close to the flame tube, of the inner ring of the two-stage cyclone, vortex generators are evenly arranged on the inner wall of the expansion section of the venturi tube in the circumferential direction, and oil mist with the small and even particle size is formed after the atomized mist is acted. Through multi-stage rotational flow, oil mist with fine and uniform granularity is formed, the atomization effect is optimized, and the fuel oil atomization quality and combustion stability in a low-temperature environment are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of diesel engine design, and relates to the testing of hydraulic tappets, in particular to a combustion chamber fuel injection and oil-gas mixing system suitable for low-temperature environments. BACKGROUND

[0002] Gas turbines are widely used in aviation, ship propulsion, power generation and other fields due to their high efficiency and cleanliness. Based on the principle of gas turbines, the applicant and the inventor previously applied for a patent with the patent number 202311263959X, which proposes a turbo-type combined heat and power device based on a supercharger for vehicle-mounted auxiliary devices, which can provide heat and electric energy for the vehicle power system. The combustion chamber, as a core component of the turbo-type combined heat and power device, undertakes the key task of converting fuel chemical energy into heat energy, and its performance is directly related to the efficiency, stability and emission level of the entire engine. A typical combustion chamber is located between the compressor and the turbine, adopting an annular or tubular structure, mainly including a combustion zone, a mixing zone, a cooling system and a fuel nozzle. Among them, the performance of the fuel nozzle, especially its fuel atomization ability, is the primary factor determining the working quality of the combustion chamber.

[0003] In the patent CN202110308236.1, a kind of combustion chamber head structure of centrifugal nozzle and cyclone integration, a kind of ignition structure is disclosed, which mentions the structure and principle, but the combustion start in low-temperature environment cannot be guaranteed.

[0004] However, the starting problem of the combustion chamber in low-temperature environments seriously restricts its reliability. In low-temperature environments, the evaporation performance of fuel deteriorates, and the uniformity of air mixing decreases significantly, making it difficult to form stable combustible mixture, reducing the ignition success rate and flame propagation stability in the combustion chamber. Conventional swirl cup nozzles perform well in normal temperature environments, but in low-temperature environments, the fuel atomization quality decreases significantly, the Sauter mean diameter of liquid droplets increases by more than 30%, and the combustion efficiency decreases by 5%~10%. Therefore, there is a need in the field for a solution that can improve low-temperature atomization performance while maintaining simple, reliable and durable mechanical structure. SUMMARY

[0005] To solve the above problems in the prior art, the present application proposes a combustion chamber fuel injection and oil-gas mixing system suitable for low-temperature environments. In view of the technical problems in the background art, the system forms fine and uniform oil mist through multi-stage swirl, optimizes the atomization effect, and improves the fuel atomization quality and combustion stability in low-temperature environments.

[0006] The combustion chamber fuel injection and oil-gas mixing system suitable for low-temperature environment comprises a flame tube, a centrifugal nozzle and a double-stage swirler which are coaxially and matchedly arranged, fuel is atomized into the flame tube through the double-stage swirler after being atomized by the centrifugal nozzle, and high-pressure air outside is formed into swirled air after being swirled by the outer ring of the double-stage swirler, so as to break, atomize and mix the fuel spray inside; The inner ring of the double-stage swirler is provided with a venturi near one end of the flame tube, and vortex generators are uniformly arranged on the inner wall of the expansion section of the venturi in a circumferential direction. The fuel spray impacts the wall surface of the venturi to form a liquid film, the liquid film is disturbed and torn by vortexes generated by the vortex generators when flowing through the expansion section of the venturi, so as to form a broken liquid film with a large number of liquid filaments and liquid strips, and the liquid film is further sheared by the reverse rotating air flow of the outer ring of the double-stage swirler when leaving the tail edge of the venturi, so as to form an oil mist with fine and uniform particle size.

[0007] Further, the double-stage swirler comprises an inner-stage axial swirler and an outer-stage axial swirler, the upper end surface of the flame tube is connected with the outer ring wall surface of the lower end of the outer-stage swirler, the inner-stage axial swirler comprises a plurality of inner-stage swirler blades arranged in an annular array to form an inner-stage swirler channel, the outer-stage axial swirler comprises a plurality of outer-stage swirler blades arranged in an annular array to form an outer-stage swirler channel, and the inner-stage swirler blades and the outer-stage swirler blades are arranged in reverse.

[0008] Further, the installation angle of the inner-stage swirler blades is 30°-45°, and the installation angle of the outer-stage swirler blades is 40°-60°.

[0009] Further, the outlet of the centrifugal nozzle is aligned with the inlet of the double-stage swirler, and the centrifugal nozzle, the double-stage swirler and the venturi form a swirled cup nozzle.

[0010] Further, the centrifugal nozzle has a multi-stage disturbance structure, comprising a fuel flow channel and a nozzle outer shell, the fuel flow channel has a pre-swirl-main-swirl structure, and the fuel flow channel is provided with built-in swirler blades to form a pre-swirl stage. The centrifugal nozzle further comprises a tangential groove and a swirler chamber to form a main-swirl stage, and the flow channel between the pre-swirl stage and the main-swirl stage is connected in a smooth transition.

[0011] Further, the installation angle of the swirler blades is 15°-25°, the tangential groove is designed in a spiral shape, the cross-sectional area is increased by 10%-25% compared with conventional design, and the radius of the swirler chamber is increased by 5%-15%, and the swirler intensity of the pre-swirl stage is 20%-40% of that of the main-swirl stage.

[0012] Further, the lower end flow channel of the cyclone chamber comprises a contraction section, a straight pipe section and an expansion nozzle in sequence, the contraction section is a horn structure with upward opening, connecting the straight pipe section and the cyclone chamber, and the expansion nozzle is a horn structure with downward opening, used for fuel flow and injection.

[0013] Further, the venturi adopts a contraction-expansion structure and is integrated with the double-stage cyclone.

[0014] Further, the number of the vortex generators is 12 and the vortex generators are arranged in a single row, and the vortex generators are triangular wing type vortex generators, and the height of the vortex generators from the lower end surface of the venturi is 2% of the throat diameter of the venturi.

[0015] Further, the upper end side wall surface of the flame tube is uniformly arranged with main combustion holes of the same aperture in the circumferential direction, and the lower end side wall surface of the flame tube is uniformly arranged with mixing holes of the same aperture in the circumferential direction; wherein the aperture of the main combustion hole is 70% to 85% of the conventional aperture, and the distance of the mixing hole from the outlet of the flame tube is 1 / 5 to 1 / 4 of the total length of the flame tube.

[0016] Compared with the prior art, the combustion chamber fuel injection and oil-gas mixing system suitable for low-temperature environment has the following beneficial effects: The fuel is sprayed from the self-centrifugal nozzle to form a pressure spray, the spray is further broken under the action of the rotating airflow passing through the inner-stage cyclone, and the spray impacts the wall surface of the venturi to form a liquid film, the liquid film is severely disturbed and torn by the vortex system generated by the vortex generators when flowing through the expansion section of the venturi, forming a broken liquid film with a large number of liquid filaments and liquid strips, and when the part of the pretreated liquid film leaves the trailing edge of the venturi, it is further sheared by the reverse rotating airflow of the outer-stage cyclone to form an oil mist with fine and uniform particle size, further optimizing the atomization effect.

[0017] The present application adopts pre-swirl-main-swirl design for the inner flow channel of the fuel nozzle, enhances the disturbance of the fuel, and corrects the size of the tangential groove and the cyclone chamber by using the fuel viscosity theory, increases the cross-sectional area of the tangential groove and the cyclone radius within a reasonable range, avoids the flow stagnation of the fuel due to high viscosity at low temperature, and at the same time, the nozzle adopts a contraction-expansion type nozzle to improve the fuel injection speed to optimize the flowability of the fuel.

[0018] The present application simultaneously utilizes the central backflow area formed by the inner and outer stage high-speed rotating airflow to realize stable combustion, designs the main combustion hole of the flame tube to be smaller than the conventional aperture to reduce the amount of cold air intake, and arranges the mixing hole close to the outlet of the flame tube to slow down the mixing speed of the cold air and the high-temperature gas, avoiding the flame being extinguished due to the sudden drop of the gas temperature, through the above design, both the low-temperature fuel atomization effect and the flame blowout prevention during the propagation process are realized, and the reliable start and stable combustion of the combustion chamber are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which form a part of this application, are intended to provide further understanding of the application and are incorporated herein in their entirety, and together with the general description of the application and its detailed description help to explain the present application. In the drawings: Figure 1 Structure schematic diagram of cross section of existing combustion chamber fuel injection and oil-gas mixing system suitable for low temperature environment; Figure 2 Structure schematic diagram of combustion chamber fuel injection and oil-gas mixing system suitable for low temperature environment of the present application; Figure 3 Cross-sectional view of centrifugal nozzle of the present application; Figure 4 Cross-sectional view of two-stage swirler and venturi of the present application; Figure 5 Cross-sectional view of flame tube of the present application.

[0020] Explanation of reference signs: 1, centrifugal nozzle; 2, two-stage swirler; 3, venturi; 4, flame tube; 5, fuel flow channel; 6, nozzle shell; 7, swirler blade; 8, flow dividing groove; 9, nozzle tangential groove; 10, swirler chamber; 11, convergent section; 12, straight pipe section; 13, divergent nozzle; 14, inner stage swirler; 15, outer stage swirler; 16, vortex generator; 17, main combustion hole; 18, mixing hole. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear and understandable, the present application is further described in detail below with reference to specific embodiments and the accompanying drawings.

[0022] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should be understood as the common meanings understood by those skilled in the art to which the present application belongs. The terms "first", "second" and similar terms used in the embodiments of the present application do not represent any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms cover the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships may also change accordingly.

[0023] Explain the professional terms as follows: Venturi, also known as Venturi tube, cleverly changes the gas flow from thick to thin, thereby achieving uniform distribution of gas and acceleration of flow rate.

[0024] like Figures 1-5 As shown, a combustion chamber fuel injection and fuel-air mixing system suitable for low-temperature environments is located at the head of the combustion chamber and can achieve reliable engine ignition in low-temperature environments. It includes a coaxial and matched flame tube 4, centrifugal nozzle 1, and two-stage cyclone separator 2. After the fuel is atomized by the centrifugal nozzle 1, it is further atomized by the inner ring of the two-stage cyclone separator 2 and enters the flame tube 4. The external high-pressure air is swirled by the outer ring of the two-stage cyclone separator 2 to form swirling air, which breaks, atomizes and mixes the internal fuel spray. The inner ring of the double-stage cyclone separator 2 is equipped with a venturi tube 3 near the end of the flame tube 4. The venturi tube 3 adopts a contraction-expansion structure and is integrated with the double-stage cyclone separator 2 to simplify the structure, reduce the number of parts, and reduce the failure rate of the assembly. Vortex generators 16 are evenly arranged circumferentially on the inner wall of the expansion section of the venturi tube 3. The vortex generators 16 are commercially available products. There are 12 vortex generators 16 arranged in a single row. They are delta airfoil type vortex generators 16. The height of the vortex generators 16 from the lower end face of the venturi tube 3 is 2% of the throat diameter of the venturi tube 3, which can achieve better vortex effect. Fuel spray impacts the wall of the venturi tube 3 to form a liquid film. As the liquid film flows through the expansion section of the venturi tube 3, it is disturbed and torn by the vortex system generated by the vortex generator 16, forming an unstable, broken liquid film with a large number of liquid filaments and liquid bands. When this pre-treated liquid film leaves the tail edge of the venturi tube 3, it is immediately further sheared by the reverse rotating airflow of the outer ring of the two-stage cyclone separator 2, forming a fine and uniform oil mist.

[0025] Preferably, the dual-stage cyclone separator 2 includes an inner-stage axial cyclone separator and an outer-stage axial cyclone separator. The upper end face of the flame tube 4 is connected to the outer ring wall of the lower end of the outer-stage cyclone separator 15. The inner-stage axial cyclone separator includes multiple inner-stage cyclone blades 7 arranged in a ring array to form an inner-stage cyclone channel. The outer-stage axial cyclone separator includes multiple outer-stage cyclone blades 7 arranged in a ring array to form an outer-stage cyclone channel. The inner-stage cyclone blades 7 and the outer-stage cyclone blades 7 are arranged in opposite directions. More preferably, the installation angle of the inner-stage cyclone blades 7 is 30°~45°, and the installation angle of the outer-stage cyclone blades 7 is 40°~60°. By optimizing these parameters, a better cyclone effect is achieved, and the fuel atomization is improved.

[0026] Preferably, the outlet of the centrifugal nozzle 1 is aligned with the inlet of the dual-stage cyclone separator 2; the centrifugal nozzle 1, the dual-stage cyclone separator 2 and the venturi tube 3 form a cyclone cup nozzle, and the flame tube 4 is coaxially arranged with the cyclone cup nozzle, forming an overall multi-stage cyclone arrangement to optimize the atomization effect.

[0027] Preferably, the centrifugal nozzle 1 is a multi-stage disturbance structure, including a fuel flow channel 5 and a nozzle outer shell, the fuel flow channel 5 is a pre-swirl-main-swirl structure, the fuel flow channel 5 is provided with swirl vanes 7 to form a pre-swirl stage; the centrifugal nozzle 1 further includes a tangential slot and a swirl chamber 10 to form a main-swirl stage, the flow channel between the pre-swirl stage and the main-swirl stage is connected by a smooth transition, and the fuel is sprayed out after two-stage swirling in the centrifugal nozzle 1 to form a better atomization effect than the original structure. More preferably, the installation angle of the swirl vane 7 is 15°-25°, the tangential slot is designed in a spiral shape, the cross-sectional area is increased by 10%-25% compared with the conventional design, and the radius of the swirl chamber 10 is increased by 5%-15%; the swirling intensity of the pre-swirl stage is 20%-40% of that of the main-swirl stage, and the parameters are set to further improve the swirling effect on the basis of two-stage swirling, and the inflow and outflow are fully matched to realize the structure.

[0028] Preferably, the lower end flow channel of the swirl chamber 10 includes a contraction section 11, a straight pipe section 12 and an expansion nozzle 13 in sequence, the contraction section 11 is a horn-shaped structure with an upward opening, connecting the straight pipe section 12 and the swirl chamber 10, and the expansion nozzle 13 is a horn-shaped structure with a downward opening, used for fuel flow and injection, to improve the fuel injection speed and optimize the fuel flowability.

[0029] Preferably, the upper end side wall surface of the flame tube 4 is circumferentially uniformly arranged with main combustion holes 17 of the same aperture, and the lower end side wall surface of the flame tube 4 is circumferentially uniformly arranged with mixing holes 18 of the same aperture; wherein the aperture of the main combustion hole 17 is 70%-85% of the conventional aperture, and the distance between the mixing hole 18 and the outlet of the flame tube 4 is 1 / 5-1 / 4 of the total length of the flame tube 4, so as to mix the slow cooling air and the high-temperature gas at a proper speed and avoid the flame being extinguished due to sudden temperature drop of the gas.

[0030] In a specific application process, the flow channel is designed by pre-swirl-main-swirl, the fuel first enters the pre-swirl stage and generates swirling through the swirl vane 7. Then the fuel enters the main-swirl stage through the flow dividing groove 8, the main-swirl stage is composed of the spiral nozzle tangential slot 9 and the swirl chamber 10, and the fuel is sprayed out through the nozzle contraction section 11, the straight pipe section 12 and the expansion nozzle 13 after high-intensity swirling in the main-swirl stage; the double-stage swirler 2 is divided into an inner-stage swirler 14 and an outer-stage swirler 15; the downstream venturi 3 adopts a contraction-expansion structure, and the inner wall of the venturi expansion section is arranged with vortex generators 16 uniformly distributed in the circumferential direction; the flame tube 4 is circumferentially arranged with a plurality of arrayed main combustion holes 17 and mixing holes 18.

[0031] The fuel flow channel 5 realizes a pre-swirl design by using the swirler vane 7, cooperates with the main swirl design composed of the rotating nozzle tangential groove 9 and the swirl chamber 10 to further enhance the fuel disturbance, and corrects the size of the tangential groove 9 and the swirl chamber 10 by using the fuel viscosity theory, increases the cross-sectional area of the tangential groove and the swirl radius in a reasonable range, avoids the flow delay of the fuel due to high viscosity at low temperature, and simultaneously uses the contraction 11-expansion type nozzle 13 inside the nozzle to improve the fuel injection speed to optimize the fuel flowability.

[0032] The fuel spray is further broken by the rotating air flow passing through the inner swirler 14, and impacts the wall of the venturi 3 to form a liquid film. The liquid film is severely disturbed and torn by the vortex generated by the vortex generator 16 when passing through the expansion section of the venturi, forming a broken liquid film with a large amount of liquid filaments and liquid strips. When this part of the pretreated liquid film leaves the trailing edge of the venturi, it is further sheared by the reverse rotating air flow of the outer swirler to form an oil mist with fine and uniform particle size, further optimizing the low-temperature atomization effect.

[0033] The inner and outer high-speed rotating air flows generated by the inner swirler 14 and the outer swirler 15 form a central recirculation zone to realize stable combustion. The main combustion hole 17 of the flame tube 4 is designed to have a smaller diameter than the conventional diameter to reduce the amount of cold air intake, and the mixing hole 18 is located close to the outlet of the flame tube to slow down the mixing speed of the cold air and the high-temperature gas, avoiding the flame being extinguished due to the sudden drop in gas temperature.

[0034] Through the above design, the low-temperature fuel atomization effect can be optimized, and the flame can not be blown out during propagation, ensuring the reliable start and stable combustion of the combustion chamber.

[0035] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

[0036] The embodiments of the present application are intended to cover all such replacements, modifications and variations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A fuel injection and fuel-air mixing system for a combustor suitable for use in a cryogenic environment, characterized in that: The fuel oil is atomized by the centrifugal nozzle and further atomized by the double-stage cyclone to enter the flame tube, and the high-pressure air outside is formed into a swirling air after being swirled by the outer ring of the double-stage cyclone, and the fuel oil spray inside is broken, atomized and mixed; The inner ring of the double-stage cyclone is provided with a venturi tube at one end close to the flame tube, and vortex generators are uniformly arranged on the inner wall of the expansion section of the venturi tube. The fuel oil spray impacts the wall of the venturi tube to form a liquid film, which is disturbed and torn by the vortex system generated by the vortex generators when flowing through the expansion section of the venturi tube, forming a broken liquid film with a large number of liquid filaments and liquid strips.

2. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The double-stage cyclone comprises an inner-stage axial cyclone and an outer-stage axial cyclone, and the upper end surface of the flame tube is connected with the outer ring wall surface of the lower end of the outer-stage cyclone.

3. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 2, wherein: The installation angle of the inner-stage cyclone vane is 30°-45°, and the installation angle of the outer-stage cyclone vane is 40°-60°.

4. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The outlet of the centrifugal nozzle is aligned with the inlet of the double-stage cyclone, and the centrifugal nozzle, the double-stage cyclone and the venturi tube form a swirl cup nozzle.

5. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The centrifugal nozzle has a multi-stage disturbance structure, comprising a fuel flow channel and a nozzle outer shell, and the fuel flow channel has a pre-swirl-main-swirl structure. The centrifugal nozzle further comprises a tangential groove and a swirl chamber, which constitute a main swirl stage, and the flow channel between the pre-swirl stage and the main swirl stage is connected by a smooth transition.

6. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 5, wherein: The installation angle of the swirl vane is 15°-25°, the tangential groove is designed in a spiral shape, the cross-sectional area is increased by 10%-25% compared with conventional design, and the radius of the swirl chamber is increased by 5%-15%.

7. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The lower end flow channel of the swirl chamber comprises a contraction section, a straight pipe section and an expansion nozzle in sequence.

8. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The venturi tube has a contraction-expansion structure and is integrated with the double-stage cyclone.

9. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The number of vortex generators is 12 and they are arranged in a single row, and the vortex generators are triangular wing type vortex generators, and the height of the vortex generators from the lower end surface of the venturi tube is 2% of the throat diameter of the venturi tube.

10. The combustion chamber fuel injection and fuel-air mixing system suitable for use in cryogenic environments of claim 1, wherein: The upper end side wall surface of the flame tube is uniformly arranged with main combustion holes of the same aperture, and the lower end side wall surface of the flame tube is uniformly arranged with mixing holes of the same aperture. The aperture of the main combustion hole is 70%-85% of the conventional aperture, and the distance of the mixing hole from the outlet of the flame tube is 1 / 5-1 / 4 of the total length of the flame tube.

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