Main combustion stage outlet speed optimization method and combustion chamber

Abstract

The main combustion stage outlet speed optimization method comprises the following steps that S1, a main combustion stage rotational flow area is divided into an inner rotational flow area and an outer rotational flow area, and the inner rotational flow area and the outer rotational flow area are divided into a plurality of height areas distributed at equal intervals according to the radial height; s2, a calculation formula of the rotational flow speed of the main combustion stage outlet in each height area is obtained, the independent variable of the calculation formula is a structural pneumatic input parameter and / or a rotational flow speed model input parameter, and the dependent variable is the rotational flow speed of the main combustion stage outlet in the height area; s3, the independent variables are adjusted, and the adjusted corresponding main combustion stage outlet rotational flow speed is obtained; and S4, forming a speed distribution curve distributed along the radial height according to the rotational flow speed of the main combustion stage outlet in each height area, and stopping the independent variable adjustment process in the step S3 until the speed distribution curve meets the requirement. According to the method, the rotational flow speed of the main combustion stage outlet can be predicted and optimized. A combustion chamber is also provided.

Description

Technical Field

[0001] The present invention relates to the field of aero-engine combustors, and more particularly to the field of design methods. Background Art

[0002] Advanced civil aero-engine combustors usually adopt a lean-premixed pre-vaporized combustion organization method to meet the increasingly stringent pollutant emission standards of ICAO. In order to balance combustion stability under small operating conditions and pollutant emission indicators under large operating conditions, this low-pollution combustor head adopts a central staging structure, with the head intake air accounting for nearly 80% of the combustor intake air, and the remaining nearly 20% of the air volume being used for flame tube cooling.

[0003] Since the mixing holes are cancelled on the flame tube, and the film cooling air is limited near the wall surface, its outlet temperature depends to a large extent on the structure and aerodynamic design of the head and the flame tube, which involves many factors such as the head swirler, nozzle characteristics, staging and zoning methods, fuel distribution ratio, fuel / air matching, air flow distribution, and flame tube structure. However, adjusting these parameters will also affect other performances such as combustion efficiency and combustion stability, thus leading to hot spots in the combustor and increasing the difficulty of controlling the outlet temperature distribution.

[0004] Chinese Patent CN111425294 discloses a fuel staging device, an engine combustor, and an aero-engine. The combustor air and fuel staging device it provides includes a central pre-combustion stage and a peripheral main combustion stage. The pre-combustion stage includes an inner radial swirler and an outer radial swirler, and fuel is injected, atomized, and mixed with the pre-combustion stage air from the nozzle. The main combustion stage includes an inner axial swirler and an outer radial swirler, and fuel is injected, atomized, and mixed with the main combustion stage air from a plurality of circumferentially discretely distributed injection points. When the combustor operates at high power, most of the fuel is ejected from the main combustion stage, so it has the most important influence on the temperature distribution in the combustor.

[0005] When the combustor operates at high power, the inlet temperature and pressure of the combustor are high. After the main combustion stage fuel and air are mixed, an oil-gas mixture with an equivalence ratio in the lean combustion range is formed. The combustion characteristics such as flame stability and chemical reaction heat release downstream are mainly determined by the flow field characteristics at the outlet of the main combustion stage.

[0006] However, in actual operation, there are the following contradictions between the outlet velocity distribution of the main combustion stage and combustion performance: When the swirl velocity type at the outlet of the main combustion stage is Figure 1 the weak swirl distribution of curve A in the figure, the flame stability is strong, but due to the long flame distribution, the high-temperature zone tends to be downstream of the combustor, which is likely to cause the outlet temperature to be too high; when the swirl velocity at the outlet of the main combustion stage is Figure 1 the strong swirl distribution of curve B in the figure, the flame stability is weak, but due to the strong swirl increasing the gas residence time, it is beneficial to both combustion efficiency and the outlet temperature distribution of the combustor.

[0007] Therefore, how to adjust the swirl velocity at the main combustion stage outlet to meet the design requirements of both flame stability and combustion chamber temperature is a technical problem that urgently needs to be solved. Summary of the Invention

[0008] An object of the present invention is to provide a method for optimizing the outlet velocity of the main combustion stage.

[0009] The method for optimizing the outlet velocity of the main combustion stage to achieve the above object includes the following steps: S1. Divide the swirl region of the main combustion stage into an inner swirl region and an outer swirl region, and divide the inner swirl region and the outer swirl region into a plurality of height regions with equally spaced distribution according to the radial height; S2. Obtain the calculation formula for the swirl velocity at the outlet of the main combustion stage in each of the height regions, where the independent variables of the calculation formula are structural aerodynamic input parameters and / or swirl velocity model input parameters, and the dependent variable is the swirl velocity at the outlet of the main combustion stage in that height region; S3. Adjust the independent variables to obtain the adjusted corresponding swirl velocity at the outlet of the main combustion stage; S4. Form a velocity distribution curve along the radial height according to the swirl velocity at the outlet of the main combustion stage in each height region, and stop the process of adjusting the independent variables in step S3 until the velocity distribution curve meets the requirements.

[0010] In one or more embodiments, in step S1, the extension line of the outer wall surface of the inner swirler is used as the demarcation line for dividing the inner swirl region and the outer swirl region.

[0011] In one or more embodiments, in step S2, the axial velocity segmented calculation formula for the swirl at the outlet of the main combustion stage in the inner swirl region and the outer swirl region is:

[0012]

[0013] where r represents the radial height of each height region, u free is the free jet velocity, H is the flow channel height, R p is the height of the jet core from the inner wall surface, n is the turbulent power law order, u free,4 represents the free jet velocity in the outer swirl region, u free,3 represents the free jet velocity in the inner swirl region, R p,4 is the height of the jet core from the inner wall surface representing the outer swirl region, R p,3 is the height of the jet core from the inner wall surface representing the inner swirl region.

[0014] In one or more embodiments, in step S2, the tangential velocity of the swirl at the outlet of the main combustion stage and the axial velocity satisfy the following formula:

[0015]

[0016] where βi is the swirling deflection angle, which is ω i Tangential velocity, u i is the axial velocity, β r represents the deflection angle at the blade root or the inner diameter of the channel of the swirler, β t represents the deflection angle at the blade top or the outer diameter of the channel, R r represents the circumferential radius at the blade root or the inner diameter of the channel, and i is the i-th height region.

[0017] In one or more embodiments, in step S1, the number of height regions divided in the inner swirling flow region and the outer swirling flow region is different.

[0018] In one or more embodiments, in step S2, the structural aerodynamic input parameters include the inner swirler flow rate ratio, the effective area of the swirler, the dimensionless height at the outlet, the relative height of the auxiliary line at the outlet, the form of the inner axial swirler blades, the form of the outer radial swirler blades, the blade installation angle, and the channel deflection angle.

[0019] In one or more embodiments, in step S2, the input parameters of the swirling velocity model include the turbulent power-law order, the relative height of the inner swirling jet core region, and the relative height of the outer swirling jet core region.

[0020] In one or more embodiments, in step S4, the velocity distribution curve is the distribution curve between the ratio of the tangential velocity to the average velocity and the radial height.

[0021] In one or more embodiments, in step S4, a target optimized velocity distribution curve is set, and when the velocity distribution curve obtained in step S3 is consistent with the optimized velocity distribution curve, the independent variable adjustment process of step S3 is stopped.

[0022] Another object of the present invention is to provide a combustion chamber, including a main combustion stage and a pre-combustion stage. The main combustion stage includes an inner swirler, an outer swirler, and a spray point, and is characterized in that the main combustion stage is designed using the above-mentioned main combustion stage outlet velocity optimization method.

[0023] The calculation formula distribution model obtained by the above-mentioned main combustion stage outlet velocity optimization method can predict the velocity distribution after the mixing of the two-stage swirl, and by adjusting the structural aerodynamic input parameters and / or the input parameters of the swirling velocity model, a velocity distribution curve that meets the requirements can be obtained, and the main combustion stage outlet velocity that takes into account both the flame stability and the quality of the combustion chamber outlet temperature distribution can be obtained. Brief Description of the Drawings

[0024] The above-mentioned and other features, properties, and advantages of the present invention will become more obvious through the following description in conjunction with the drawings and embodiments, where:

[0025] Figure 1 It is a schematic diagram of the central cross-section of the combustion chamber head;

[0026] Figure 2 It is a schematic diagram of the outlet swirl velocity distribution curve;

[0027] Figure 3 It is a schematic diagram of the inner swirl region and the outer swirl region;

[0028] Figure 4 It is a schematic diagram of the height region division with equal spacing distribution;

[0029] Figure 5 It is a comparison diagram of the optimized swirl velocity distribution and the unoptimized swirl velocity distribution;

[0030] Figure 6A It is a schematic diagram of the swirler;

[0031] Figure 6B It is a schematic diagram of the swirl velocity;

[0032] Figure 7 It is a flow chart of the method for optimizing the outlet velocity of the main combustion stage. Detailed implementation manners

[0033] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention is obviously capable of being implemented in many other ways different from this description. Those skilled in the art can make similar generalizations and deductions according to the actual application situation without departing from the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0034] It should be noted that these and subsequent other drawings are only examples, and they are not drawn according to the condition of equal proportion, and should not be used to limit the actual claimed protection scope of the present invention.

[0035] Figure 1 A schematic diagram showing the central cross-section of the combustion chamber head includes a nozzle 11, injection points 12, a pre-combustion stage 1, and a main combustion stage 2. The pre-combustion stage 1 includes a first inner-layer radial swirler 21 and a first outer-layer radial swirler 22. The main combustion stage 2 includes a second inner-layer axial swirler 31 and a second outer-layer radial swirler 32 to achieve staged swirling flow. Here, the inner and outer layers refer to the side relatively closer to the center and the side farther from the center in the radial direction. Fuel is injected, atomized from the nozzle 11 and mixed with the pre-combustion stage air. At the same time, fuel is injected, atomized from a plurality of injection points 12 distributed circumferentially and mixed with the main combustion stage air.

[0036] In the following introduction, the second inner axial swirler 31 is simplified to an inner swirler, and the second outer radial swirler 32 is simplified to an outer swirler.

[0037] The main combustion stage outlet velocity optimization method described in the present invention constructs a calculation formula distribution model of the swirl velocity at the main combustion stage outlet, which can predict the velocity distribution after the mixing of the two-stage swirls, and by adjusting the input parameters, obtain a swirl velocity distribution that balances flame stability and the combustion chamber outlet temperature distribution.

[0038] The method includes the following steps: S1. Divide the main combustion stage swirl region into an inner swirl region and an outer swirl region, and divide the inner swirl region and the outer swirl region into a plurality of height regions with equally spaced distributions according to the radial height; S2. Obtain the calculation formula of the swirl velocity at the main combustion stage outlet in each height region, where the independent variables of the calculation formula are the structural aerodynamic input parameters and / or the swirl velocity model input parameters, and the dependent variable is the swirl velocity at the main combustion stage outlet in this height region; S3. Adjust the independent variables to obtain the adjusted corresponding swirl velocity at the main combustion stage outlet; S4. Form a velocity distribution curve along the radial height according to the swirl velocity at the main combustion stage outlet in each height region, and stop the independent variable adjustment process of step S3 until the velocity distribution curve meets the requirements.

[0039] Figure 3 For Figure 1 The enlarged view at A in the figure is an analysis model of the two-stage swirl velocity distribution constructed based on the main combustion stage structure. The auxiliary line 40 is preferably the extension line of the outer wall surface 34 of the second inner axial swirler 31, which divides the main combustion stage swirl region, that is, the internal flow field of the swirler, into an inner swirl region 3 and an outer swirl region 4. The boundaries enclosing the inner swirl region 3 include the auxiliary line 40, the second flow channel inlet wall surface 34, the inner swirl region outlet 41, and the flow channel inner wall surface 33; the boundaries enclosing the outer swirl region 4 include the auxiliary line 40, the first flow channel inlet wall surface 35, the flow channel outer wall surface 36, and the outer swirl region outlet 42.

[0040] Continue to refer to Figures 2 to 4 As shown, the radial height of the main combustion stage outlet section is divided into two sections, an inner region 41 located in the inner swirl region 3 and an outer region 42 located in the outer swirl region 4, by the auxiliary line 40. They are divided with the same radial interval, and the total number of equally spaced regions is K, such as K = 20, and the height region where the auxiliary line 40 is located at the outlet is marked as k.

[0041] For example, the heights of each section in the inner region 41 of the inner swirl region 3 are sequentially marked as (1, 2, 3... k - 1) from the inside to the outside, and the heights of each section in the outer region 42 of the outer swirl region 4 are sequentially marked as (k + 1, k + 2, k + 3... K) from the inside to the outside. The number of height regions divided in the inner swirl region and the outer swirl region can be the same or different.

[0042] K can be divided into fewer or more sections according to the size of the outlet height.

[0043] Among them, Figure 2 and Figure 3 in, Ri represents the position where the inner wall surface 33 of the flow channel is located, Rm represents the position where the auxiliary line 40 is located, and Ro represents the position where the outer wall surface 36 of the flow channel is located. The height H of the inner region 41 is between Ri and Rm 3 , and the height H of the outer region 42 is between Rm and Ro 4 .

[0044] From Ri to Ro, it is divided into K height regions (1, 2, 3... K) with equally spaced distribution.

[0045] Since the inner and outer swirl mixing regions are short and the flow Reynolds number is high, ignoring the influence of the two-stage swirl shear on the swirl jet core region, an n-power law model for the axial velocity radial distribution in the inner and outer swirl regions is established:

[0046]

[0047] Among them, r represents the radial height of the swirl region, r = 0 represents the radial inner side of the swirl region, and u free is the free jet velocity, and the relationship with the average flow velocity u mean is u free / u mean = 1 + 1 / n, and u mean is calculated according to the mass flow rate divided by the density divided by the cross-sectional area; R p is the height of the jet core from the inner wall surface, H is the height of the flow channel, and generally R p of a fully developed pipe flow is equal to 50%H. The turbulent power law order, that is, the larger the exponent n value, the closer the flow is to a fully developed turbulent flow. For example, the fully developed turbulent flow in most industrial pipes approximates the 1 / 7 power law (n = 7).

[0048] Near the auxiliary line 40, the wall shear layers of the inner swirl region 3 and the outer swirl region 4 shed and fuse. It can be reasonably assumed that the shear stress in the mixing region is constant. Thus, the axial velocity distribution formula in the shear layer can be obtained according to the principles of mass and momentum continuity The subscripts 3 and 4 represent the numerical values of the inner swirl region and the outer swirl region respectively. For example, u free,4 represents the free jet velocity in the outer swirl region 4, and R p,4 is the height of the jet core from the inner wall surface in the outer swirl region 4, and u free,3 represents the free jet velocity in the inner swirl region 3 described, and R p,3 is the height of the jet core from the inner wall surface in the inner swirl region 3.

[0049] According to the above two swirl axial velocity calculation formulas and The axial velocity distributions of the inner and outer swirl regions are superimposed, and the axial velocity segment distribution formula is obtained according to the radial height:

[0050]

[0051] Wherein, r represents the radial height starting from the inner wall surface 33 of the flow channel. t,3 (r) represents the 50% flow channel height H from the inner wall surface 33 of the flow channel to the inner swirl flow area 3 3 The flow velocity in the area; u m (r) represents the 50% to 100% flow channel height H of the inner swirl zone 3 3 50% flow channel height H to the outer vortex flow zone 4 4 The flow velocity in the area; u t,4 (r) represents the 50% to 100% flow channel height H of the outer vortex flow zone 4 4 It should be noted that the above partition range is based on the height R of the jet core from the inner wall. p The prerequisite for dividing the flow channel height H by 50% is that when R p When the height of the mountain changes, the above partition range also changes accordingly.

[0052] Further, we get

[0053] The air passing through the swirler blades or slots generates a tangential (circumferential) velocity component, such as Figure 6B As shown. The second inner axial swirler 31 adopts axial air intake, and the second outer radial swirler 32 adopts radial air intake. In order to adjust the swirl velocity distribution at the main combustion stage outlet, the structural aerodynamic input parameters and / or the swirl velocity model input parameters are adjusted, as shown in Table 1.

[0054] Table 1 Input parameters of graded swirl velocity model

[0055]

[0056] The structural aerodynamic input parameters include the flow ratio of the inner swirler, the effective area of ​​the swirler, the dimensionless height of the outlet, the relative height of the outlet auxiliary line, the inner axial swirler blade form, the outer radial swirler blade form, the blade installation angle, and the groove deflection angle.

[0057] The inner cyclone flow ratio is the percentage of the inner cyclone flow to the total flow of the main combustion stage, and the calculation formula of the outlet dimensionless height is (Ro-Ri) / Ri.

[0058] The inner axial swirler blades 100 may be in the form of straight blades or swept blades, and the outer radial swirler blades may be in the form of straight channels or swept channels.

[0059] The input parameters of the swirl velocity model include the turbulence power law order, the relative height of the inner swirling jet core area, and the relative height of the outer swirling jet core area.

[0060] The turbulence power law order n (the same for internal and external cyclones) is generally taken as 7. The relative height of the core area of ​​the internal cyclone is calculated as Rp / H, and the relative height of the core area of ​​the external cyclone is calculated as Rp / H.

[0061] The swirler is designed with a variable blade installation angle or a slot deflection angle.

[0062] By twisting the installation angle θ of the axial blades of the inner swirler 31 along the blade height scheme, or twisting the deflection angle of the radial channel of the outer swirler 32 along the radial direction, the swirl deflection angle β of the outlet swirl at each height can be adjusted. i , also the angle between the outlet airflow direction and the axis, such as Figure 6B shown.

[0063] Using formula Calculate the linear torsion vortex finder blade installation angle and slot deflection angle, where the subscript i corresponds to the number of the outlet radial height region (1, 2, 3...K), marking the i-th height region, β r represents the deflection angle at the blade root or the inner diameter of the channel of the swirler, β t represents the deflection angle at the blade tip or the outer diameter of the slot, R r Represents the blade root radius or the inner diameter of the groove.

[0064] The tangential velocity of the swirl flow at the main combustion stage outlet is i With axial speed u i Approximately satisfies the formula ω i =u i tan(β i ),like Figure 6B shown.

[0065] According to the formula Calculate the swirl velocity distribution at the main combustion stage outlet and obtain the optimized velocity distribution. Figure 5 The three-dimensional CFD calculation results shown determine the adjustment effect and adjustment accuracy of the swirl velocity calculation model parameters.

[0066] The velocity distribution curve along the radial height distribution is formed according to the swirl velocity of the main combustion stage outlet in each height area. Figure 2 Compare the curves A and B shown to determine whether the optimized speed meets the design requirements of flame stability and combustion chamber temperature.

[0067] For example, the blade installation angle of the inner cyclone in Table 1 is adjusted to make and ω i =u itan(β i ) varies accordingly; reducing the outer diameter of the main combustion stage outlet changes the calculated variable R p,4 . After adjusting the structural aerodynamic input parameters and / or the swirl velocity model input, the adjusted swirl velocity is calculated.

[0068] Figure 5 Shows the velocity distributions calculated according to the model and the respective three-dimensional CFD simulation results for the original and optimized schemes. The diamonds represent the tangential swirl velocity distribution calculated by CFD before optimization; the solid lines represent the velocity distributions calculated by the above velocity formula before optimization; the triangles represent the velocity distributions calculated by CFD after adjusting the vane installation angle and the outer diameter parameter of the main combustion stage outlet; the dashed lines represent the velocity distributions calculated by the above velocity formula after adjusting the vane installation angle and the outer diameter parameter of the main combustion stage outlet.

[0069] By Figure 5 comparison, it can be seen that the velocity calculated by the velocity formula is very close to the velocity calculated by CFD, proving that the calculation accuracy of the above velocity formula can be guaranteed, and the calculation formula distribution model has good prediction ability.

[0070] The optimized velocity is also shown in Figure 2 the schematic diagram of the outlet swirl velocity distribution shown. The dashed line C represents the swirl velocity at the outlet of the main combustion stage after optimization. By comparison, it can be obtained that compared with curve A and curve B, the optimized swirl velocity meets the design requirements, and can balance the design requirements of flame stability and combustion chamber temperature, neither being too weak in flame stability nor causing too high an outlet temperature.

[0071] In some embodiments, a target optimized velocity distribution curve can be preset, and the target optimized velocity distribution curve has better performance. When the velocity distribution curve obtained after adjusting the independent variable is generally consistent or consistent with the target optimized velocity distribution curve, the independent variable adjustment process is stopped.

[0072] The present invention uses specific terms to describe the embodiments of the present application. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification is not necessarily the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the present application can be appropriately combined.

[0073] Although the present invention is disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, all modifications, equivalent changes and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention fall within the protection scope defined by the claims of the present invention.

Claims

1. Main combustion stage outlet velocity optimization method, the main combustion stage includes an inner swirler and an outer swirler, Characterized in that, It includes the following steps: S1. Divide the swirler region of the main combustion stage into an inner swirler region and an outer swirler region, and divide the inner swirler region and the outer swirler region into a plurality of height regions with equally spaced distribution according to the radial height; S2. Obtain the calculation formula for the outlet swirl velocity of the main combustion stage in each of the height regions, where the independent variables of the calculation formula are structural aerodynamic input parameters and / or swirl velocity model input parameters, and the dependent variable is the outlet swirl velocity of the main combustion stage in that height region; S3. Adjust the independent variables to obtain the adjusted corresponding outlet swirl velocity of the main combustion stage; S4. Form a velocity distribution curve along the radial height according to the outlet swirl velocity of the main combustion stage in each height region, and stop the independent variable adjustment process of step S3 until the velocity distribution curve meets the requirements.

2. The method according to claim 1, Characterized in that, In step S1, the extension line of the outer wall surface of the inner swirler is used as the demarcation line for dividing the inner swirler region and the outer swirler region.

3. The method according to claim 1, Characterized in that, In step S2, the axial velocity segmented calculation formula for the outlet swirl of the main combustion stage in the inner swirler region and the outer swirler region is: Among them, r represents the radial height of each height region, u free is the free jet velocity, H is the flow channel height, R p is the height of the jet core from the inner wall surface, n is the turbulent power-law order, u free,4 represents the free jet velocity in the outer swirl flow region, u free,3 represents the free jet velocity in the inner swirl flow region, R p,4 is the height representing the jet core from the inner wall surface in the outer swirl flow region, R p,3 is the height representing the jet core from the inner wall surface in the inner swirl flow region.

4. The method according to claim 3, Characterized in that, In step S2, the tangential velocity and the axial velocity of the outlet swirl of the main combustion stage satisfy the following formula: ω i = u i tan(β i ) where β i is the swirl deflection angle, ω i is the tangential velocity, u i is the axial velocity, β r represents the deflection angle at the blade root or the inner diameter of the channel of the swirler, β t represents the deflection angle at the blade top or the outer diameter of the channel, R r represents the circumferential radius at the blade root or the inner diameter of the channel, and i is the i-th height region.

5. The method according to claim 1, Characterized in that, In step S1, the number of height regions divided in the inner swirler region and the outer swirler region is different.

6. The method according to claim 1, Characterized in that, In step S2, the structural aerodynamic input parameters include the inner swirler flow rate ratio, the effective area of the swirler, the dimensionless height of the outlet, the relative height of the outlet auxiliary line, the form of the inner axial swirler blade, the form of the outer radial swirler blade, the blade installation angle, and the channel deflection angle.

7. The method according to claim 1, Characterized in that, In step S2, the swirl velocity model input parameters include the turbulent power law order, the relative height of the inner swirling jet core region, and the relative height of the outer swirling jet core region.

8. The method according to claim 1, Characterized in that, In step S4, the velocity distribution curve is the distribution curve between the ratio of the tangential velocity to the average velocity and the radial height.

9. The method according to claim 1, Characterized in that, In step S4, set a target optimized velocity distribution curve, and stop the independent variable adjustment process of step S3 when the velocity distribution curve obtained in step S3 is consistent with the target optimized velocity distribution curve.

10. Combustor, including a main combustion stage and a pilot combustion stage, the main combustion stage includes an inner swirler, an outer swirler and a spray point, Characterized in that, The main combustion stage is designed using the main combustion stage outlet velocity optimization method according to any one of claims 1-9.

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