A H2 combustion chamber head structure for high altitude and low pressure environments

Abstract

The present invention discloses an H2 combustion chamber head structure for use in high-altitude, low-pressure environments. The head body comprises a head body, the head body being provided with a plurality of evenly distributed air passages. A stabilizer having a V-shaped cross section is provided at one end of the air passage's air outlet. The stabilizer contains a fuel chamber for accommodating H2. The V-shaped tip of the stabilizer is positioned adjacent to the air passage's air inlet end. Jet ports are formed on two opposing outer walls of the V-shaped open end of the stabilizer, with a mixing gap formed between the two opposing outer walls and the inner wall of the air passage. The jet ports are connected to the fuel chamber. By employing diffusion combustion, the present invention prevents hydrogen from flashing back and burning the head. The provision of the stabilizer achieves uniform temperature distribution and enhances hydrogen / air mixing, thereby improving combustion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion chambers, and in particular to an H2 combustion chamber head structure used in 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 carried out exploration activities in the high-altitude field. High-altitude long-endurance aircraft, as an important tool for exploring high altitudes, have attracted widespread attention from scientific researchers.

[0003] The main propulsion systems currently used in high-altitude, long-endurance aircraft include solar power, fuel cell propulsion, and H2-fueled combustor technology. However, the conversion efficiency of solar energy is low. To maximize the area of ​​solar exposure, the aircraft's aspect ratio must be increased, which not only affects maneuverability but also places higher demands on overall structural strength. Fuel cells still suffer from large size, heavy weight, and limited storage capacity. The H2-fueled combustor, a solution developed based on an analysis of the impact of high-altitude environmental characteristics on combustor inlet parameters and combustion performance, holds great potential.

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

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

[0006] In order 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 high-altitude, low-pressure environments comprises a head body, the head body being provided with a plurality of evenly arranged and distributed air passages, a stabilizer having a V-shaped cross section being provided at one end of the air outlet of the air passage; a fuel cavity for accommodating H2 being contained within the stabilizer; the V-shaped tip of the stabilizer being adjacent to one end of the air inlet of the air passage, an air jet opening being provided on two opposing outer walls of one end of the V-shaped opening of the stabilizer, a mixing gap being formed between the two opposing outer walls and the inner wall of the air passage; and the air jet opening being in communication with the fuel cavity.

[0008] Furthermore, two opposite inner walls of the air channel 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 channel, and the end walls of the stabilizer are respectively fixedly connected to the other two opposite inner walls of the air channel.

[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; the open end of the inner V-plate and the 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; 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 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=10mm~15mm.

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

[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 is applied to a high altitude low pressure environment. By setting a plurality of evenly arranged and distributed air channels and setting a V-shaped stabilizer at one end of the air outlet of the air channel, a plurality of combustion units are formed in the head body. A jet nozzle is set through the stabilizer for ejecting H2, which can disperse the large H2 flame into many small flames to avoid local high temperature. 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 setting 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 generated is used to strengthen the mixing of hydrogen and air, so that the temperature distribution is more uniform and the NOx emission is lower, thereby improving the combustion efficiency. The present application can avoid the backfire of hydrogen and burn the head by adopting the method of diffusion combustion, and achieves uniform temperature distribution and strengthens the mixing of hydrogen / air by setting the stabilizer, thereby improving 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 the stabilizer of the present invention;

[0020] Figure 3 is a radial-axial schematic diagram of the 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 examples and drawings. The exemplary embodiments of the present invention and their descriptions 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 combustor is a solution proposed based on an analysis of the impact of high-altitude environmental characteristics on combustor inlet parameters and combustion performance, and it has great potential. Specifically, the impact of high-altitude environmental characteristics on combustor performance is analyzed as follows:

[0025] The characteristics of the high-altitude environment are as follows: first, as the altitude increases, the temperature decreases linearly at an altitude of 0-11 km. The atmospheric temperature remains unchanged at an altitude of 11-20 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). 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] (1)

[0027] (2)

[0028] 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.

[0029] The combustion chamber inlet parameter characteristics under high-altitude conditions. Since the engine compression ratio is determined by the compressor speed and blade structure, 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 Equation (3). Under constant temperature conditions, the reaction rate is proportional to the pressure to the power of n (n = a + b, the reaction order). Low pressure conditions reduce the chemical reaction rate, thereby reducing combustion efficiency.

[0030] (3)

[0031] 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 viscous force increases during the flow process. The characteristic scale in Re is only related to the structure as a constant value (the characteristic scale of the vortex finder 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 The Reynolds number is 3%, and the jet velocity through the flame tube, calculated from the dynamic pressure, is approximately 100 m / s. This can be considered essentially unchanged. Re = 68471 on the ground, 25601 at 11 km, and 6188 at 20 km. The Reynolds number on the ground is 2.675 times that at 11 km and 11 times that at 20 km. The Reynolds number is low at high altitudes. The low Reynolds number leads to turbulence intensity that affects the mixing of air and fuel, which in turn adversely affects combustor performance parameters such as outlet temperature distribution, combustion efficiency, and pollutant emission concentrations.

[0032] (4)

[0033] (5)

[0034] Where B is a constant related to the type of gas, and B for air is 110.4K.

[0035] In summary, high altitude, low pressure, and low Re negatively impact chemical reaction rates, fuel-air mixing, and combustion efficiency. H2, a clean fuel with a high calorific value (120 kJ / kg) that produces only water, offers low density, high diffusivity, a high adiabatic flame temperature, a high laminar flame speed, and a wide flammability limit. This provides a solution for aircraft operating at high altitudes and for long flight times.

[0036] Example

[0037] like Figure 1-4 The H2 combustor head structure shown is applied to a high altitude low pressure environment, including:

[0038] 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 above-mentioned air channel 2; a fuel chamber 34 for accommodating H2 is provided in the stabilizer 3, 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. The diffusion combustion method can avoid the backfire of hydrogen directly applied to the traditional structure, thereby burning the head body 1; and by arranging the air channels 2 and stabilizers 3 in a one-to-one correspondence as a structure in which multiple units are evenly arranged, the hydrogen of the large flame can be dispersed into multiple small flames for injection, so as to achieve good mixing between hydrogen and air, while also avoiding local high temperature. Preferably, the number of the above-mentioned units is 6 to 9, that is, the number of the air channels 2 and stabilizers 3 is 6 to 9 respectively, which can achieve good combustion effect and combustion efficiency.

[0039] The V-shaped tip of the stabilizer 3 is located near the air inlet end of the air passage 2. Jet ports 35 are formed on opposing outer walls of the V-shaped opening of the stabilizer 3, creating a mixing gap between the stabilizer 3 and the inner wall of the air passage 2. The jet ports 35 communicate with the fuel chamber 34. The mixing gap between the stabilizer 3 and the inner wall of the head body 1 provides space for air and hydrogen to penetrate and mix. Hydrogen is ejected from one end of the V-shaped opening to both sides, penetrating the flowing air and mixing with it. The V-shaped structure creates a recirculation zone, increasing turbulence intensity. The hydrogen-air mixture forms spanwise vortices in the recirculation zone, enhancing mixing and promoting uniform temperature distribution and improved combustion efficiency.

[0040] It should be noted that the uniform temperature distribution described above refers not only to the outlet temperature distribution characteristics, but also to the temperature distribution in the main combustion zone (the main combustion zone and the combustion chamber outlet, respectively, are located 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 in the main combustion zone reflects NOx emissions. Fewer hot spots in the main combustion zone indicate less likely to generate thermal NOx. To enhance H2 / air mixing and ensure good mixed combustion in the main combustion zone, resulting in a more uniform temperature distribution and lower NOx emissions, while also reducing the burden on the mixing holes (through holes located in the sidewalls of the main combustion zone for temperature adjustment) to adjust the temperature distribution, the large hydrogen flame is dispersed into numerous smaller flames, drawing on the principles of micro-diffusion combustion to achieve good H2 / air mixing. To further enhance H2 / air mixing, a V-shaped stabilizer 3 is added to the hydrogen / air cross-jet outlet to generate spanwise vortices that enhance H2-air mixing.

[0041] As an example, the two opposite inner walls of the above-mentioned air channel 2 are arranged obliquely 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 channel 2, and the end walls of the stabilizer 3 are respectively fixedly connected to the other two opposite inner walls of the air channel 2.

[0042] By designing the air channel 2 to be inclined relative to the two inner walls, that is, designing the air outlet of the air channel 2 to be an oblique jet, the two inclined side walls of the stabilizer 3 are opposite to it, so as to guide the air and fuel mixture to present an expansion flow, thereby ensuring the flame connection between adjacent units.

[0043] 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 multiple delivery pipes are set on the head body 1. The delivery pipes continuously deliver fuel to the stabilizer 3 in each unit body, and the fuel is sprayed out by the stabilizer 3.

[0044] As an example, the stabilizer 3 comprises an inner V-plate 31 and an outer V-plate 32. The outer V-plate 32 is stacked outside the inner V-plate 31 and shares the same centerline with the inner V-plate 31. The open ends of the inner V-plate 31 and the outer V-plate 32 are connected by a horizontal plate 33 to form a fuel chamber 34. The horizontal plate 33 is parallel to the centerlines of the inner V-plate 31 and the outer V-plate 32, respectively. The jet port 35 is located in the horizontal plate 33. This structural design creates a V-shaped structure for the stabilizer 3, allowing hydrogen to be ejected vertically from the stabilizer 3, forming a transverse jet with the airflow, thereby enhancing air penetration and mixing.

[0045] As an example, the end of the horizontal plate 33 connected to the outer V-plate 32 is opposite the air outlet of the air channel 2, and the end of the horizontal plate 33 connected to the inner V-plate 31 is relatively located outside the air outlet of the air channel 2. In other words, the horizontal plate 33 is partially positioned outside the air outlet of the air channel 2. This not only facilitates the processing of the air jet 35, but also allows the horizontal jet of hydrogen to penetrate the air flow unimpeded, assisting the oblique jet in cross-flaming, thereby improving the cross-flaming effect.

[0046] As an example, the air inlet aspect ratio of the above-mentioned air channel 2 is w / h=0.7~1.35, where 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.

[0047] 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 located outside the air channel 2 is l bo =3mm~10mm.

[0048] As an example, at least four air jets 35 are provided, and the four air jets 35 are arranged in pairs on two opposing horizontal plates 33. The diameter of the air jets is d0 = 0.6 mm to 1.2 mm, and the spacing between two adjacent air jets on the horizontal plate 33 is d1 = 3 mm to 6 mm.

[0049] The expansion angle of the air channel 2 can be calculated based on 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 and air and improve the mixing effect.

[0050] 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 By combining these data with the dimensions of the air inlet and outlet of air passage 2, as well as the number and dimensions of the jet nozzles, the air inlet and outlet areas, and thus the air outlet flow rate and hydrogen jet flow rate, can be limited. This ensures good mixing of hydrogen and air, and a stable momentum ratio under different operating conditions. This wide operating range requires similar hydrogen / air jet momentum ratios under different operating conditions, where different operating conditions refer to variations in combustion chamber inlet parameters at different altitudes. It should be noted that due to the high-altitude environment, to prevent engine stall and increase the probability of successful re-ignition after stall, the head body 1 is designed with an equivalence ratio close to 1.

[0051] In order to make the penetration effects of H2 and air closer under different working conditions, the jet momentum ratio under different altitude working conditions was calculated (see Table 1).

[0052] Table 1: H2 / air momentum ratio at different altitudes

[0053]

[0054] The results show that the momentum ratios under different parameter conditions are all in the same order of magnitude, ranging from 3.3 to 6.5, which are relatively close.

[0055] In a specific embodiment, the embodiment of the present application calculated 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.

[0056] Beneficial effects of the embodiments of the present application:

[0057] By discretizing the traditional large head structure into several units, the combustion organization is modularized. This not only facilitates basic research on single head units and provides technical support for improving combustion chamber performance, but also offers the advantage of ease of 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 its rational structure, the layout of the combustion chamber is improved, making it more compact and achieving a wider stable working margin than existing combustion chambers. This has the advantages of simple structure and low production cost.

[0058] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art 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 high altitude low pressure environment, characterized in that: The head body comprises a head body having a plurality of evenly distributed air passages, an air outlet end of each air passage having a stabilizer with a V-shaped cross section; a fuel cavity for accommodating H2 is provided within the stabilizer; the V-shaped tip of the stabilizer is adjacent to the air inlet end of the air passage; air jets are formed on two opposing outer walls of the V-shaped open end of the stabilizer, and a mixing gap is formed between the two opposing outer walls of the V-shaped open end of the stabilizer and the inner wall of the air passage; the air jets are in communication with the fuel cavity; The two opposing 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 opposing inner walls of the air passage; 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 centerline as the inner V-plate; an open end of the inner V-plate and an open end of the outer V-plate are connected by a horizontal plate to form the fuel chamber; the horizontal plate is parallel to the centerlines of the inner V-plate and the outer V-plate respectively; the jet port is opened on the horizontal plate; 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.

2. The H2 combustion chamber head structure for use in high altitude and low pressure environments according to claim 1 is characterized in that: There are at least four air jets, and the four air jets are arranged in groups of two on two opposite horizontal plates.

3. The H2 combustion chamber head structure for use in high altitude and low pressure environments according to claim 2 is 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.

4. The H2 combustion chamber head structure for use in high altitude and low pressure environments according to claim 3 is characterized in that: 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=10mm~15mm.

5. The H2 combustion chamber head structure for use in high altitude and low pressure environments according to claim 2 is characterized in that: The diameter of the air jet is d0 = 0.6 mm to 1.2 mm, and the distance between two adjacent air jets on the horizontal plate is d1 = 3 mm to 6 mm.

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

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