H2 combustion chamber head structure applied to high-altitude low-pressure environment

Abstract

The H2 combustion chamber head structure applied to the high-altitude low-pressure environment comprises a head body, the head body is provided with a plurality of air channels which are evenly arranged and distributed, and a stabilizer with a V-shaped cross section is arranged at one end of an air outlet of each air channel; a fuel cavity for accommodating H2 is formed in the stabilizer; the V-shaped tip of the stabilizer is close to one end of an air inlet of the air channel, air nozzles are formed in two opposite outer walls of one end of a V-shaped opening of the stabilizer, and penetrating and mixing gaps are formed between the air nozzles and the inner wall of the air channel; and the air nozzle is communicated with the fuel cavity. The diffusion combustion mode is adopted, the phenomenon that the head is burnt by tempering of hydrogen can be avoided, uniform temperature distribution is achieved by arranging the stabilizer, hydrogen / air mixing is enhanced, and the combustion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of phase change energy storage technology, and in particular to an H2 combustion chamber head structure applied to a high altitude low pressure environment. Background Art

[0002] With the continuous development and progress of science and technology, countries around the world have successively launched exploration operations in the high-altitude field. High-altitude and long-endurance aircraft, as an important tool for exploring high altitudes, have attracted widespread attention from scientific researchers.

[0003] The power systems currently used in high-altitude, long-flight aircraft mainly include: solar power technology, fuel cell propulsion technology, and H2 fuel combustion chamber technology. However, the conversion rate of solar energy is low. In order to increase the solar irradiation area and make the aspect ratio of the aircraft larger, this not only affects its maneuverability, but also puts higher requirements on the overall structural strength. Fuel cells still have the problems of large size, heavy weight and limited storage capacity. The H2 fuel combustion chamber is a solution proposed based on the analysis of the impact of high-altitude environmental characteristics on the combustion chamber inlet parameters and combustion performance, and has great potential.

[0004] However, the combustion chamber head structure of a traditional fuel gas turbine is an integral combustion chamber divided by multiple inclined guide plates, and liquid fuel is introduced at the air outlet to achieve combustion. If the combustion chamber head of a traditional fuel gas turbine is directly applied to the combustion of H2, there will be the following shortcomings: (1) Due to the high flame propagation speed of H2, premixed combustion and strong swirl combustion are prone to flashback risks; (2) H2 has a high calorific value and adiabatic flame temperature, which easily produces local high-temperature areas, which not only increases the burden of regulating temperature, but also increases the risk of high NOx emissions; (3) Due to the large altitude span and wide range of combustion chamber inlet parameters, the wide operating condition adjustment capability is also a huge test for the traditional combustion chamber structure. This will affect the combustion efficiency, outlet temperature distribution characteristics, and applicability of the wide operating range of the combustion chamber. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a H2 combustion chamber head structure for use in a high altitude low pressure environment.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A H2 combustion chamber head structure for use in a high-altitude, low-pressure environment comprises a head body, the head body is provided with a plurality of evenly arranged and distributed air passages, an air outlet end of the air passage is provided with a stabilizer with a V-shaped cross section; a fuel cavity for accommodating H2 is provided in the stabilizer; the V-shaped tip of the stabilizer is close to an air inlet end of the air passage, two opposite outer walls of the V-shaped opening end of the stabilizer are provided with jets, and a mixing gap is provided between the jets and the inner wall of the air passage; the jets are communicated with the fuel cavity.

[0008] Furthermore, two opposite inner walls of the air passage are inclined and gradually expand from the air inlet end to the air outlet end; the two inclined side walls of the stabilizer are respectively opposite to the two inclined inner walls of the air passage, and the end walls of the stabilizer are respectively fixedly connected to the other two opposite inner walls of the air passage.

[0009] Furthermore, the stabilizer includes an inner V-plate and an outer V-plate, the outer V-plate is stacked on the outside of the inner V-plate and has the same center line as the inner V-plate; an open end of the inner V-plate is connected to an open end of the outer V-plate through a horizontal plate to form the fuel chamber; the horizontal plate is parallel to the center lines of the inner V-plate and the outer V-plate respectively; and the jet port is opened on the horizontal plate.

[0010] Furthermore, at least four air jets are provided, and the four air jets are arranged in groups of two and are respectively arranged on two opposite horizontal plates.

[0011] Furthermore, one end of the horizontal plate connected to the outer V-plate is opposite to the air outlet of the air channel, and one end of the horizontal plate connected to the inner V-plate is relatively located outside one end of the air outlet of the air channel.

[0012] Furthermore, the inner angle of the outer V-plate is α=30°~60°; the blocking ratio of the stabilizer is w b / w a =0.25~0.55, where w b is the opening width of the inner V-plate, w a is the circumferential length of the air outlet of the air channel; the length of the horizontal plate outside the air channel is l bo =3mm~10mm.

[0013] Furthermore, the air inlet aspect ratio of the air channel is w / h=0.7-1.35, wherein w is the circumferential length, h is the radial length, and h=10 mm-15 mm.

[0014] Furthermore, the diameter of the air jet hole is d0=0.6mm-1.2mm, and the distance between two adjacent air jet holes on the horizontal plate is d1=3mm-6mm.

[0015] Furthermore, the number of the air channels and the stabilizers is 6 to 9.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The H2 combustion chamber head structure disclosed by the present invention for use in a high altitude low pressure environment is provided with a plurality of evenly arranged and distributed air channels and a V-shaped stabilizer is provided at one end of the air outlet of the air channel, so that a plurality of combustion units are formed in the head body, and a jet port is provided through the stabilizer for ejecting H2, so that the large H2 flame can be dispersed into a plurality of small flames to avoid local high temperature, and there is a mixing gap between the stabilizer and the inner wall of the air channel, so that H2 and the air flowing in the air channel can be penetrated and mixed to achieve good mixing between hydrogen / air; by providing a stabilizer at the hydrogen / air cross jet outlet, the gas flow rate is changed to form a recirculation zone, the turbulence intensity is increased, and the spanwise vortex is generated to strengthen the mixing of hydrogen and air, so that the temperature distribution is more uniform, the NOx emission is lower, and the combustion efficiency is improved. The present application can avoid hydrogen flashback and burn the head by adopting the diffusion combustion method, and achieves uniform temperature distribution and strengthens the mixing of hydrogen / air by providing a stabilizer, so as to improve the combustion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the combustion chamber head structure of the present invention;

[0019] Figure 2 is a circumferential-axial schematic diagram of a stabilizer of the present invention;

[0020] Figure 3 is a radial-axial schematic diagram of a stabilizer of the present invention;

[0021] Figure 4 It is a front view of the combustion chamber head structure of the present invention.

[0022] Figure symbols: 1-head body, 2-air channel, 3-stabilizer, 31-inner V-plate, 32-outer V-plate, 33-horizontal plate, 34-fuel chamber, 35-injection port. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0024] It should be noted that the H2 fuel combustion chamber is a solution proposed based on the analysis of the impact of high-altitude environmental characteristics on the combustion chamber inlet parameters and combustion performance, and has great potential. Specifically, under high-altitude environmental characteristics, the impact of high-altitude environmental characteristics on the combustion chamber performance is analyzed as follows:

[0025] The characteristics of the high-altitude environment are: first, as the altitude increases, the temperature decreases linearly at an altitude of 0 to 11 km. The atmospheric temperature remains unchanged at an altitude of 11 to 20 km, but as the altitude continues to increase, the atmospheric temperature begins to rise. The relationship between atmospheric temperature and altitude is shown in formula (1); second, the atmospheric pressure decreases exponentially with increasing altitude. The relationship between atmospheric pressure and altitude is shown in formula (2). The density can be obtained based on the ideal gas state equation, so the density also decreases exponentially with increasing altitude. For example, at an altitude of 11 km, the air pressure is 22.6 kPa, and at an altitude of 20 km, the air pressure is only 5.47 kPa, and the air density increases from 0.364 kg / m 3 Down to 0.088kg / m 3 .

[0026]

[0027] Among them, P0 is the surface atmospheric pressure; g is the acceleration of gravity; R is the gas constant of air; z is the altitude, all in the International System of Units.

[0028] Characteristics of combustion chamber inlet parameters under high altitude environment. Since the engine compression ratio is determined by the speed and blade structure of the compressor, the compressor compression ratio can reach 25-50, and the upper limit of the compression ratio is fixed. Therefore, as the altitude increases, the compressor outlet pressure becomes lower and lower, which leads to huge changes in the inlet pressure and air mass flow rate between the ground operating parameters and the high altitude operating parameters. According to the law of mass action, there is a relationship between the reaction rate and the partial pressure (or concentration) of the reactants as shown in formula (3). Under constant temperature conditions, the reaction rate is proportional to the nth power of the pressure (n=a+b, reaction order). Low pressure conditions reduce the chemical reaction rate, thereby reducing the combustion efficiency.

[0029]

[0030] The influence of high-altitude environment on Reynolds number (Re, formula (4)). The speed of decrease of air density in high altitude is faster than the speed of decrease of air temperature. According to Sutherland formula (formula (5)), the dynamic viscosity of the medium is related to temperature. When the temperature change is not large and the density decreases greatly, the viscosity increases during the flow process. The characteristic scale in Re is only related to the structure as a constant (the characteristic scale of the vortex flowmeter is generally 10mm). Generally, the intake volume flow rate is basically the same under different working conditions, so the flow rate (U, according to the pressure ratio, the compressor outlet pressure is obtained, and the total pressure loss of the flame tube is generally 3%, according to the dynamic pressure, the jet velocity through the flame tube is about 100m / s), which can be considered basically unchanged, Re = 68471 on the ground, Re = 25601 at an altitude of 11km, and Re = 6188 at an altitude of 20km. The Re in the ground environment is 2.675 times the Re at an altitude of 11km, and 11 times the Re at an altitude of 20km. The Reynolds number is low in the high-altitude environment. The low Reynolds number causes the turbulence intensity to affect the mixing of air and fuel, which in turn has an adverse effect on the combustion chamber performance parameters such as the outlet temperature distribution characteristics, combustion efficiency, and pollutant emission concentration.

[0031]

[0032] Where B is a constant related to the type of gas, and B of air is 110.4K.

[0033] In summary, high altitude, low pressure, and low Re have adverse effects on chemical reaction rate, fuel-air mixing, and combustion efficiency. H2, as a clean fuel with high calorific value (120 kJ / kg) that only produces water when burned, has the characteristics of low density, high diffusivity, high adiabatic flame temperature, high laminar flame speed, and wide flammable limit. It not only provides a solution to the problem of high altitude and long flight time of aircraft, but also helps to achieve the goal of alleviating the global greenhouse effect.

[0034] Example

[0035] like Figure 1-4 The head structure of an H2 combustion chamber used in a high altitude and low pressure environment is shown, comprising:

[0036] The head body 1 is provided with a plurality of evenly arranged and distributed air channels 2, which penetrate the head body 1, with one end being an air inlet and the other end being an air outlet; a stabilizer 3 with a V-shaped cross section is provided at one end of the air outlet of the air channel 2; the stabilizer 3 has a fuel cavity 34 for accommodating H2, and the stabilizer 3 is used to spray hydrogen at the outlet to mix with the air flowing in the air channel 2 to achieve diffusion combustion, and the diffusion combustion form can avoid the traditional structure directly applied to hydrogen to cause flashback, thereby burning the head body 1; and by setting the air channel 2 and the stabilizer 3 to a structure in which a plurality of unit bodies are evenly arranged in a one-to-one correspondence, the hydrogen of the large flame can be dispersed into a plurality of small flames for spraying, so as to achieve a good mixing between hydrogen / air, and also avoid local high temperature. Preferably, the number of the above-mentioned unit bodies is 6 to 9, that is, the number of the air channel 2 and the stabilizer 3 are 6 to 9 respectively, which can have a good combustion effect and combustion efficiency.

[0037] The V-shaped tip of the stabilizer 3 is close to one end of the air inlet of the air channel 2. Two opposite outer walls of one end of the V-shaped opening of the stabilizer 3 are provided with jet ports 35, and there is a mixing gap between the stabilizer 3 and the inner wall of the air channel 2; the jet ports 35 are connected to the fuel cavity 34. There is a mixing gap between the stabilizer 3 and the inner wall of the head body 1, that is, there is a space for air and hydrogen to penetrate and mix. Hydrogen is injected from one end of the V-shaped opening to both sides, penetrates into the flowing air to achieve mixing, and due to the existence of the V-shaped structure, a recirculation zone is generated, the turbulence intensity is increased, and the mixed airflow of hydrogen and air forms a spanwise vortex in the recirculation zone to strengthen mixing, which is conducive to uniform temperature distribution and improved combustion efficiency.

[0038] It should be noted that the uniform temperature distribution not only refers to the outlet temperature distribution characteristics, but also refers to the temperature distribution of the main combustion zone (the main combustion zone and the combustion chamber outlet are located in sequence behind the head body 1). The outlet temperature distribution characteristics represent the service life of the turbine (the turbine is directly connected to the combustion chamber outlet), while the temperature distribution of the main combustion zone reflects the NOx emission. The fewer hot spots in the main combustion zone, the less likely it is to generate thermal NOx. In order to strengthen the H2 / air mixing, the flame can achieve good mixed combustion in the main combustion zone, making the temperature distribution more uniform and the NOx emission lower, and at the same time reducing the burden on the characteristics of the mixing hole to adjust the temperature distribution (the mixing hole is a through hole set on the side wall of the main combustion zone to adjust the temperature distribution), by drawing on the idea of ​​micro-diffusion combustion, the large hydrogen flame is discretized into many small flames to achieve good mixing between H2 / air. In order to further improve the mixing of H2 / air, a V-shaped stabilizer 3 structure is added at the hydrogen / air cross jet outlet, in order to strengthen the mixing of H2 and air through the generated spanwise vortex.

[0039] As an example, the two opposite inner walls of the air passage 2 are inclined and gradually expand from the air inlet end to the air outlet end; the two inclined side walls of the stabilizer 3 are respectively opposite to the two inclined inner walls of the air passage 2, and the end walls of the stabilizer 3 are respectively fixedly connected to the other two opposite inner walls of the air passage 2.

[0040] The air channel 2 is designed to be inclined relative to the two inner walls, that is, the air outlet of the air channel 2 is designed to be an oblique jet, and the two inclined side walls of the stabilizer 3 are opposite to it to guide the air and fuel mixture to present an expansion flow to ensure the flame connection between adjacent units.

[0041] The other two end walls of the stabilizer 3 are fixedly connected to the air passage 2 so as to support and fix it; and a through hole can be opened on the fixed connection surface, and a plurality of delivery pipes are arranged on the head body 1, and the delivery pipes continuously deliver the fuel to the stabilizer 3 in each unit body, and the stabilizer 3 sprays it out.

[0042] As an example, the stabilizer 3 includes an inner V-plate 31 and an outer V-plate 32, wherein the outer V-plate 32 is stacked outside the inner V-plate 31 and has the same center line as the inner V-plate 31; an open end of the inner V-plate 31 is connected to an open end of the outer V-plate 32 through a horizontal plate 33 to form a fuel chamber 34; the horizontal plate 33 is parallel to the center lines of the inner V-plate 31 and the outer V-plate 32 respectively; and the jet port 35 is opened in the horizontal plate 33. Through the above structural design, the stabilizer 3 forms a V-shaped structure, and the hydrogen is ejected vertically from the stabilizer 3 to form a lateral jet with the air flow, so as to improve the penetration effect with the air, thereby improving the mixing effect.

[0043] As an example, one end of the horizontal plate 33 connected to the outer V-plate 32 is opposite to the air outlet of the air channel 2, and one end of the horizontal plate 33 connected to the inner V-plate 31 is relatively located outside one end of the air outlet of the air channel 2. That is, the horizontal plate 33 is partially arranged outside the air outlet of the air channel 2, which is convenient for processing the jet port 35 on the one hand, and the hydrogen lateral jet flow can penetrate the air flow without obstruction on the other hand, and assist the oblique jet flow to cross flame, thereby improving the cross flame effect.

[0044] As an example, the air inlet aspect ratio of the above-mentioned air channel 2 is w / h=0.7~1.35, wherein w is the circumferential length (the distance between the two inclined inner wall inlet ends), h is the radial length (the width of the inclined inner wall inlet end), and h=10mm~15mm.

[0045] As an example, the inner angle of the outer V-plate 32 is α=30°~60°; the blocking ratio of the stabilizer 3 is w b / w a =0.25~0.55, where w bis the opening width of the inner V-plate 31, w a The length of the horizontal plate 33 outside the air channel 2 is l bo =3mm~10mm.

[0046] As an example, at least four jet ports 35 are provided, and the four jet ports 35 are arranged in pairs on two opposite horizontal plates 33. The diameter of the jet ports is d0 = 0.6 mm to 1.2 mm, and the distance between two adjacent jet ports on the horizontal plate 33 is d1 = 3 mm to 6 mm.

[0047] The expansion angle of the air channel 2 can be calculated by using the inlet aspect ratio, radial length, circumferential length and other data of the air channel 2. Limiting the expansion angle to the above range can avoid flow separation between hydrogen / air and improve the mixing effect.

[0048] The angle α of the outer V plate of the stabilizer 3 and the expansion width l of the inner V plate 31 are bo And the blocking ratio is w b / w a And other data, combined with the size data of the air inlet and air outlet of the air channel 2 and the number and size of the jet holes, the air inlet area and the air outlet area can be limited, and then the air outlet flow rate and the hydrogen injection flow rate can be limited to ensure that hydrogen and air have a good mixing effect, and can have a stable momentum ratio under different working conditions, that is, a wide working range requires that the momentum ratio of hydrogen / air jet under different working conditions is relatively close, where different working conditions refer to the changes in the combustion chamber inlet parameters at different altitudes. It should be noted that due to the high-altitude environment, to prevent the engine from stalling, and to increase the success rate of stalling and re-ignition, the head body 1 is designed with an equivalent ratio close to 1.

[0049] In order to make the penetration effects of H2 and air closer under different working conditions, the jet momentum ratio under different altitude conditions was calculated (see Table 1).

[0050] Table 1: H2 / air momentum ratio at different altitudes

[0051]

[0052] From the results, we can see that the momentum ratios under different parameter conditions are in the same order of magnitude, ranging from 3.3 to 6.5, which are relatively close.

[0053] In a specific embodiment, the embodiment of the present application calculates the cold flow field and hot field of the combustion chamber under different working conditions through numerical simulation. The results show that in the cold flow field, hydrogen fuel and air have a good mixing effect under different working conditions, and are basically mixed evenly 40 mm downstream of the air channel outlet; in the hot flow field, ignition can be successful, the H2 transverse jet flame is stable downstream of the V-shaped stabilizer, the adjacent heads can be successfully flame-linked, and no backfire or flameout occurs under the studied working conditions. The H2 flame can operate stably in a wider working boundary, the outlet temperature distribution is uniform (OTDF<0.2, RTDF<0.1), and the combustion efficiency is high.

[0054] Beneficial effects of the embodiments of the present application:

[0055] The traditional large head structure is discretized into several units, making the combustion organization modular. This is not only conducive to the basic research of single head units to provide technical support for the performance improvement of the combustion chamber, but also has the advantage of easy maintenance at the application level. By adjusting the combustion organization, the problems of poor fuel / air mixing and low combustion efficiency in the combustion chamber caused by low pressure and low Reynolds number are solved. At the same time, due to the reasonable structure, the layout of the combustion chamber is improved, making the combustion chamber more compact, and a wider stable working boundary can be achieved than the existing combustion chamber, with the advantages of simple structure and low production cost.

[0056] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A H2 combustion chamber head structure used in a high altitude low pressure environment, characterized in that: The invention comprises a head body, wherein the head body is provided with a plurality of air passages evenly arranged and distributed, and an air outlet end of the air passage is provided with a stabilizer with a V-shaped cross section; a fuel cavity for accommodating H2 is provided in the stabilizer; the V-shaped tip of the stabilizer is close to the air inlet end of the air passage, and two opposite outer walls of the V-shaped opening end of the stabilizer are provided with jets, and a mixing gap is provided between the jets and the inner wall of the air passage; the jets are connected with the fuel cavity.

2. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 1, characterized in that: The two opposite inner walls of the air passage are arranged obliquely and gradually expand from the air inlet end to the air outlet end; the two inclined side walls of the stabilizer are respectively opposite to the two inclined inner walls of the air passage, and the end walls of the stabilizer are respectively fixedly connected to the other two opposite inner walls of the air passage.

3. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 1, characterized in that: The stabilizer includes an inner V-plate and an outer V-plate, wherein the outer V-plate is stacked outside the inner V-plate and has the same center line as the inner V-plate; an open end of the inner V-plate and an open end of the outer V-plate are connected through a horizontal plate to form the fuel chamber; the horizontal plate is parallel to the center lines of the inner V-plate and the outer V-plate respectively; and the jet port is opened on the horizontal plate.

4. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 3 is characterized in that: At least four air jets are provided, and the four air jets are arranged in groups of two on two opposite horizontal plates.

5. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 3 or 4, characterized in that: One end of the horizontal plate connected to the outer V plate is opposite to the air outlet of the air channel, and one end of the horizontal plate connected to the inner V plate is relatively located outside one end of the air outlet of the air channel.

6. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 5, characterized in that: The inner angle of the outer V-plate is α=30°~60°; the blocking ratio of the stabilizer is w b / w a =0.25~0.55, where w b is the opening width of the inner V-plate, w a is the circumferential length of the air outlet of the air channel; the length of the horizontal plate outside the air channel is l bo =3mm~10mm.

7. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 6, characterized in that: The air inlet aspect ratio of the air passage is w / h=0.7-1.35, wherein w is the circumferential length, h is the radial length, and h=10 mm-15 mm.

8. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 4 or 7, characterized in that: The diameter of the air jet hole is d0=0.6mm-1.2mm, and the distance between two adjacent air jet holes on the horizontal plate is d1=3mm-6mm.

9. The H2 combustion chamber head structure for use in a high altitude low pressure environment according to claim 1, characterized in that: The number of the air channels and the stabilizers is 6 to 9.

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