Three-dimensional curved surface isolation section structure with turning section and design method

Abstract

The invention discloses a three-dimensional curved surface isolation section structure with a turning section and a design method, the isolation section comprises an isolation section part, a turning section part and a connected transition section, and the height, position and midpoint parameters of a two-dimensional molded line of a symmetry plane of an isolation section inlet section and a combustion chamber inlet section are given; an isolation section outlet section having a certain offset distance and expansion ratio with an isolation section inlet molded line is constructed as a transition section, an isolation section is a molded surface section which is relatively straight from an isolation section inlet to the transition section, and a turning section is a molded surface turning part extending from the transition section to a combustion chamber inlet; smooth transition from an isolation section inlet to a combustion chamber inlet can be achieved by adjusting the position and the rotation angle of the transition section, compared with other configurations, the configuration can flexibly adjust the contraction degree of the side wall of the isolation section so as to meet the overall layout requirement of an engine, and an aircraft can be more compact in structure, higher in volume ratio and higher in engineering application value.

Description

Technical Field

[0001] The present invention relates to the field of aircraft isolation section structure layout, in particular to a three-dimensional curved surface isolation section structure with a turning section. Background Art

[0002] As a propulsion system for air-breathing hypersonic vehicles, scramjets involve a complex series of internal aerodynamic issues. Their performance and stability are crucial to overall aircraft performance and flight safety. The separator, a crucial component of a scramjets engine, connects its outlet to the combustion chamber, which is typically circular or rectangular in cross-section. The separator's inlet cross-section is determined by the inlet duct and is typically different from its outlet cross-section. Therefore, the separator must achieve a smooth transition from inlet to outlet cross-section.

[0003] In the early days of scramjet technology research, liquid hydrogen fuel was the most widely used. With the continuous development and improvement of engine technology, hydrocarbon fuels such as aviation kerosene have gradually replaced liquid hydrogen fuel as engine propellants. Compared to engines using liquid fuel, engines using solid fuel have the following advantages: simple structure, low manufacturing and maintenance costs; propellant can be stored inside the engine for a long time, which reduces reaction time; high propellant energy density; high engine volume specific impulse, etc. Among them, the powder fuel ramjet, a new concept engine using high-energy metal or non-metallic powder as fuel, combines the advantages of solid fuel ramjet engines with the advantages of liquid fuel ramjet engines, such as thrust and adjustable flow, and has broad application prospects in the aerospace field.

[0004] Solid-fuel scramjets are similar in structure to liquid-fuel scramjets, primarily consisting of an inlet, an isolating section, a combustion chamber, and a tail nozzle. The differences lie in the fuel storage, supply, and combustion organization. Currently, solid-fuel scramjets can be broadly categorized into three types: wall-loaded solid-fuel scramjets, dual-combustion chamber solid-fuel scramjets, and solid rocket scramjets. Solid rocket scramjets use an oxygen-depleted solid propellant as fuel, self-sustaining combustion within a gas generator. The resulting high-temperature, high-pressure, primary fuel-rich gas is injected through the gas generator throat into the supersonic combustion chamber, where it mixes and burns with the supersonic mainstream air. This overcomes the challenges of the previous two configurations, including ignition and flame stabilization difficulties, low mixing efficiency, low combustion efficiency, and difficulty adjusting the engine's air-fuel ratio. Through continuous research and development, the technology has matured. However, since oxygen-depleted solid propellants use a gas generator for primary combustion, its placement impacts the vehicle's structural layout, increasing length and limiting three-dimensional space.

[0005] To this end, it is necessary to develop a more flexible isolation section configuration that is more adaptable to intake systems that are subject to higher overall layout restrictions, so as to meet the overall layout and volume ratio requirements of the solid powder scramjet engine. Summary of the Invention

[0006] In order to solve the problems arising from the existing technology, the present invention provides a three-dimensional curved isolation section structure with a turning section, which can achieve a smooth transition of the complex cross-sectional shape and position of the turning section outlet where the isolation section inlet is connected to the combustion chamber inlet, solve the problems of the isolation section in the intake system being limited in three dimensions, and the configuration and flow field characteristics being significantly different from those of conventional isolation sections, and meet the overall layout and volume ratio requirements of the solid powder scramjet engine.

[0007] The present invention also provides a design method for the configuration of the three-dimensional curved surface isolation segment with a turning segment, so as to obtain the three-dimensional curved surface isolation segment structure.

[0008] In order to achieve the above-mentioned purpose, the three-dimensional curved isolation section structure with a turning section of the present invention can adopt the following technical solutions:

[0009] A three-dimensional curved isolation section structure with a turning section comprises an isolation section portion, a turning section portion and a transition section connecting the two portions, wherein the front of the isolation section portion is an isolation section entrance, and the rear of the turning section portion is a turning section exit; the isolation section portion is a straight section of the profile extending from the isolation section entrance to the transition section, and the turning section portion is a turning section of the profile extending from the transition section to the turning section exit; the straight section of the profile refers to an upper profile line or a lower profile line of any longitudinal section of the upper profile or the lower profile of the isolation section portion, which is a straight line, and the turning section of the profile refers to an upper profile line or a lower profile line of any longitudinal section of the upper profile or the lower profile of the turning section portion, which is a curve.

[0010] Furthermore, the expansion ratio H between the isolating section outlet profile and the isolating section inlet profile is satisfied. DS-out / H th >1. Offset Y e ≤1.

[0011] Furthermore, the expansion ratio H DS-out / H th It is 1.4 to 1.8.

[0012] Furthermore, the side walls of the isolation section and the turning section are rounded.

[0013] Compared to conventional straight or slightly expanded isolators, the three-dimensional curved isolator structure with a curved section described in this invention achieves a smooth aerodynamic transition between the isolator and combustion chamber inlet cross-sections by constructing a transition curve and cross-section, while maintaining the fixed shape and position of the isolator and combustion chamber inlet cross-sections. This improves the three-dimensional curved isolator flow field and enhances aerodynamic performance. Compared to other configurations, this design allows for a more compact aircraft structure, a higher volume ratio, and greater engineering application value.

[0014] The design method of the three-dimensional curved isolation section configuration with a turning section provided by the present invention adopts the following technical solutions:

[0015] Determine the height, position and center point of the two-dimensional profile of the symmetry surface through the given inlet and outlet sections;

[0016] The isolator section outlet profile, which has a certain expansion ratio and offset from the isolator section inlet profile, is determined as a transition curve. Based on the upper and lower vertices of the two-dimensional profile, the isolator section inlet profile and the isolator section outlet profile are connected by a straight line as the symmetric surface profile of the upper and lower walls of the isolator section. The isolator section outlet and the turning section outlet are connected by a curve as the symmetric surface profile of the upper and lower walls of the turning section.

[0017] The outlet profile of the isolation section on the symmetry surface is taken as the object and rotated counterclockwise around the central axis by a certain angle to obtain the outlet section of the isolation section as the transition section of the three-dimensional model; the upper wall profile on the symmetry surface is taken as the object, and the inlet section of the isolation section, the outlet section of the isolation section and the upper wall surface of the inlet section of the combustion chamber are used as guide lines to sweep, thereby obtaining the upper wall surface and the lower wall surface of the isolation section and the turning section; the upper and lower wall surfaces of the isolation section and the turning section are taken as the objects, and the inlet section of the isolation section, the outlet section of the isolation section and the side wall of the inlet section of the combustion chamber are used as guide lines to sweep, and then the edge chamfering with a variable radius is performed to obtain the side wall surface of the isolation section and the side wall surface of the turning section.

[0018] Furthermore, the transition section is formed by rotating the isolating section outlet profile with a certain offset and expansion ratio around the central axis at a certain rotation angle Z in a counterclockwise direction. e Get, adjust Z e Controls the shrinkage of the side walls of the isolation section.

[0019] The design method proposed in this paper achieves a smooth transition from the inlet of the isolation section to the combustion chamber inlet by adjusting the position and rotation angle of the transition section. The degree of contraction of the isolation section's sidewalls can also be flexibly adjusted to meet the overall engine layout requirements. Controlling the rotation angle of the transition curve controls the area expansion ratio between the inlet and outlet of the isolation section, as well as the contraction of the isolation section's sidewalls, thereby improving the three-dimensional curved isolation flow field and enhancing aerodynamic performance. Compared to other configurations, this design results in a more compact aircraft structure, a higher volume ratio, and greater engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a three-dimensional curved isolation section with a turning section according to the present invention.

[0021] Figure 2 It is a schematic diagram of the original configuration of the isolation section inlet cross section and the combustion chamber inlet cross section of the present invention.

[0022] Figure 3 It is a schematic diagram of the two-dimensional profile of the symmetric surface of the three-dimensional curved isolation section with a turning section of the present invention.

[0023] Figure 4 It is a schematic diagram of the three-dimensional profile of the three-dimensional curved isolation section with a turning section of the present invention.

[0024] Figure 5 To verify the Mach cloud diagram of the symmetry surface of the three-dimensional curved isolation segment with turning segments under different expansion ratio conditions in the experiment.

[0025] Figure 6 To verify the Mach cloud diagram and velocity streamlines of the lower wall of the turning section in the experiment.

[0026] Figure 7 To verify the cloud diagram of the total pressure recovery coefficient at the turning section outlet under different expansion ratio conditions in the experiment.

[0027] Figure 8 To verify the symmetrical surface wave system structure of the three-dimensional curved isolation section with turning sections under different offset conditions in the experiment.

[0028] Figure 9 To verify the changes in velocity streamlines and recirculation zones in the separation zone of the turning section under different offset conditions in the experiment.

[0029] Figure 10 To verify the cloud diagram of the total pressure recovery coefficient at the turning section outlet under different offset conditions in the experiment.

[0030] Figure 11 To verify the curve of the Mach number / total pressure recovery coefficient at the outlet of the three-dimensional curved isolation section with a turning section changing with the expansion ratio under different offset conditions in the experiment. DETAILED DESCRIPTION

[0031] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0032] See also Figures 1 to 4As shown, the present invention discloses a three-dimensional curved isolation section structure with a turning section, including an isolation section part 1 and a turning section part 2, which are connected by a transition section 5; the front of the isolation section part is the isolation section inlet, and the rear of the turning section part is the turning section outlet; the isolation section part 1 is a straight section of the profile extending from the isolation section inlet section 3 to the transition section 5, and the transition section 5 is the isolation section outlet; the turning section part 2 is a turning section of the profile extending from the transition section 5 to the combustion chamber inlet section 4. The straight section of the profile refers to the upper or lower profile line of any longitudinal section of the upper or lower profile of the isolation section part, which is a straight line; the turning section of the profile refers to the upper or lower profile line of any longitudinal section of the upper or lower profile of the turning section part, which is a curve; the isolation section inlet section 3 and the turning section outlet section 4 are fixed, and there is an angle between the two in both the horizontal and vertical directions. The turning section outlet section 4 is used to connect to the combustion chamber inlet.

[0033] A specific design method for a three-dimensional curved surface isolation section structure with a turning section is as follows:

[0034] (1) Given the inlet cross-section 3 of the isolation section and the inlet cross-section 4 of the combustion chamber, determine the height, position, and center point of the two-dimensional profile of the symmetry plane;

[0035] (2) Determine the isolation section inlet profile 6 and the combustion chamber inlet profile 7, and determine the isolation section outlet profile 8 with a certain expansion ratio and offset from the isolation section inlet profile as the transition curve, and the expansion ratio H between the isolation section outlet profile and the isolation section inlet profile is satisfied. DS-out / H th >1. Offset Y e ≤1; according to the upper and lower vertices of the two-dimensional profile, the isolation section inlet profile 6 and the isolation section outlet profile 8 are connected by a straight line to obtain the isolation section upper wall symmetry surface profile 10 and the isolation section lower wall symmetry surface profile 11; the isolation section outlet profile 8 and the combustion chamber inlet profile 7 are connected by a curve to obtain the symmetry surface profile 12 of the upper wall of the turning section and the symmetry surface profile 13 of the lower wall of the turning section;

[0036] (3) Take the outlet profile 8 of the isolation section as the object and rotate it counterclockwise around the central axis 9 by a certain angle Z eThe outlet section 5 of the isolation section is obtained as the transition section of the three-dimensional curved isolation section structure with the turning section; the two-dimensional profile line 10 of the symmetric surface of the upper wall of the isolation section and the symmetric surface profile line 12 of the upper wall of the turning section are used as objects, and the upper wall profile lines of the isolation section inlet section 3, the isolation section outlet section 5 and the combustion chamber inlet section 4 are used as guide lines to sweep, thereby obtaining the upper wall of the isolation section and the upper wall of the turning section; the two-dimensional profile line 11 of the symmetric surface of the lower wall of the isolation section and the symmetric surface profile line 13 of the lower wall of the turning section are used as objects. Taking the isolation section inlet section 3, isolation section outlet section 5 and combustion chamber inlet section 4 as the object, sweeping is performed with the lower wall profile of the isolation section as the guide line, thereby obtaining the lower wall surface of the isolation section and the lower wall surface of the turning section; taking the upper and lower wall surfaces of the isolation section and the turning section as the object, sweeping is performed with the side wall profile of the isolation section inlet section 3, isolation section outlet section 5 and combustion chamber inlet section 4 as the guide line, and then performing variable radius edge chamfering processing to obtain the side wall surface 14 of the isolation section and the side wall surface 15 of the turning section;

[0037] By controlling the rotation angle Z of the isolation section outlet profile 8 around the central axis 9 e , the degree of contraction of the side wall surface 14 of the isolation section can be flexibly controlled to meet the requirements of the overall layout; the curved surface of the turning section can better transition the position difference between the inlet section 3 of the isolation section and the inlet section 4 of the combustion chamber, while meeting the requirements of the overall layout and volume ratio and introducing the airflow into the combustion chamber.

[0038] See also Figures 5 to 7 As shown, it is an embodiment for verifying the influence of the expansion ratio on the flow field characteristics of a three-dimensional curved isolation section with a turning section. The detailed implementation steps of designing the isolation section using the present invention are described below.

[0039] (1) The inlet boundary condition of the isolation section is the pressure far field, and the inlet Mach number is 3.14, the static pressure is 17549.16 kPa, and the static temperature is 459.58 K. The outlet boundary condition of the turning section is the pressure outlet. The outlet section of the isolation section as the transition section is the internal surface. The internal flow field of the isolation section is the main analysis object, and the aerodynamic parameters of the turning section outlet are the important reference objects for aerodynamic performance.

[0040] (2) According to step (3) in the design method, take the rotation angle Z e =69°, eccentricity Y e =0.4H th As a fixed parameter, the models with expansion ratios of 1.4, 1.5, 1.65, and 1.8 are studied. The flow field characteristics near the symmetric surface of the three-dimensional curved isolation section with a turning section and the aerodynamic parameters of the turning section outlet are compared under different expansion ratios. The influence of the expansion ratio change on the three-dimensional curved isolation section is evaluated, and the schlieren patterns of the symmetric surface of the three-dimensional curved isolation section with different expansion ratios under the flow state are obtained, namely, Figure 5, Mach cloud diagram and velocity streamlines of the lower wall of the turning section, that is, Figure 6 , the total pressure recovery cloud diagram of the turning section outlet under different expansion ratio conditions, that is Figure 7 , and the aerodynamic parameters of the turning section exit under different expansion ratio conditions, namely Table 1, H Ds-out / H th is the expansion ratio, M zw is the Mach number, σ zw is the total pressure recovery coefficient, p / p ent is the pressure ratio.

[0041] Figure 5 It can be seen that the wave system structure of the isolation section under different expansion ratios is similar, and the offset distance remains unchanged. When the expansion is large, the compressibility of the upper wall of the turning section to the airflow becomes stronger, and a strong compression wave is generated on the upper wall to interact with the boundary layer, forcing the boundary layer to separate, and a separation zone with obvious low-energy flow convergence appears on its lower wall.

[0042] Figure 6 It can be seen that the range of the separation zone where the low-energy flow converges increases with the increase of the expansion ratio;

[0043] Figure 7 It can be seen that the low total pressure recovery area and the high total pressure recovery area at the turning section outlet increase with the increase of the expansion ratio;

[0044] As shown in Table 1, as the expansion ratio increases, the outlet Mach number first increases and then decreases, the total pressure recovery coefficient at the outlet of the turning section gradually increases, and the overall pressure ratio does not change much. When the expansion ratio is 1.8, a more obvious separation zone appears in the turning section, resulting in an increase in the total pressure loss. The total pressure recovery coefficient has a smaller increase than that when the expansion ratio is 1.65.

[0045] The reasons why the exit Mach number first increases and then decreases with the increase of the expansion ratio are as follows:

[0046] When the offset is small, the expansion ratio is too large, which will form a large separation zone on the lower wall of the turning section, resulting in the narrowing of the flow channel and the reduction of the Mach number.

[0047] Under the same offset, the increase in the expansion ratio causes the inlet area of ​​the turning section to expand while the outlet area of ​​the turning section remains unchanged. As a result, when the expansion is larger, the pipe profile of the turning section shrinks more sharply and the outlet Mach number decreases faster.

[0048] Table 1 Main aerodynamic parameters of the turning section exit under different expansion ratios

[0049]

[0050] The overall analysis shows that when the offset is constant and the expansion ratio is large, the interaction between the shock wave and the boundary layer intensifies, forcing the boundary layer to separate, resulting in a separation zone with obvious low-energy flow convergence near the lower wall of the turning section. In particular, when the expansion ratio is 1.8, the separation zone is the largest.

[0051] See also Figures 8 to 11 As shown, it is an embodiment for verifying the influence of offset on a three-dimensional curved isolation segment with a turning segment. The detailed implementation steps of designing the isolation segment using the present invention are described below.

[0052] (1) The inlet boundary condition of the isolation section is the pressure far field, and the inlet Mach number is 3.14, the static pressure is 17549.16 kPa, and the static temperature is 459.58 K. The outlet boundary condition of the turning section is the pressure outlet. The outlet section of the isolation section as the transition section is the internal surface. The internal flow field of the isolation section is the main analysis object, and the aerodynamic parameters of the turning section outlet are the important reference objects for aerodynamic performance.

[0053] (2) Take the expansion ratio as 1.8, the isolation section rotation angle Z e =69°, the flow field characteristics near the symmetric surface of the three-dimensional curved isolation section with a turning section and the aerodynamic parameters of the turning section outlet are compared under different offset conditions, and the influence of the offset change on the three-dimensional curved isolation section is evaluated. The schlieren images of the symmetric surface of the three-dimensional curved isolation section with a turning section under different offsets are obtained, namely Figure 8 , the velocity streamlines in the separation zone of the turning section and the change diagram of the recirculation zone at different offsets under the flow state, that is, Figure 9 , cloud diagram of total pressure recovery coefficient at the turning section outlet under different offset conditions, that is Figure 10 , aerodynamic parameters of the turning section outlet under different offset conditions, that is, Table 2, three-dimensional surface isolation outlet Mach number / total pressure recovery coefficient cloud diagram with turning section under different offset conditions, that is, Figure 11 .

[0054] Figure 8 It can be seen that the two-dimensional wave system structures of the different offset models are similar, but when the offset is large, the shock waves and expansion waves generated by the deflection of the upper and lower walls of the inlet are stronger and the reflection phenomenon near the symmetry plane is more obvious;

[0055] Figure 9 It can be seen that as the offset increases, the separation gradually weakens, the separation packet gradually becomes smaller, and the separation center gradually moves downstream, and the corresponding recirculation area decreases accordingly. The increase in offset is beneficial to improving the airflow separation phenomenon on the lower wall of the turning section with a large expansion ratio.

[0056] Figure 10 It can be seen that the fluid kinetic energy in the low total pressure area is low, which is sensitive to the downstream back pressure and has an adverse effect on the back pressure resistance of the three-dimensional curved isolation section. The increase of offset is beneficial to its back pressure resistance. When the expansion ratio is constant, the low total pressure recovery area at the lower left corner of the turning section outlet decreases with the increase of offset.

[0057] As shown in Table 2, the Mach number at the exit of the turning section increases with the increase of the offset, the total pressure recovery coefficient gradually increases, and the pressure ratio gradually decreases.

[0058] Table 2 Main aerodynamic parameters of the turning section exit under different offset conditions

[0059]

[0060] Figure 11 It can be seen that under the condition of large expansion ratio, the effect of offset is more obvious. The outlet Mach number and total pressure recovery coefficient increase significantly with the increase of offset. The reasons are as follows:

[0061] The increase in offset weakens the flow separation phenomenon on the lower wall of the turning section caused by the excessive expansion ratio. Moreover, with the increase in the expansion ratio of the isolation section, the proportion of the mainstream high-speed area is large, which makes the high-energy flow at the turning section outlet increase with the increase of the expansion ratio.

[0062] Combining the two experiments above, we can see that, at the same offset, as the expansion ratio increases, the velocity in the mainstream region of the isolator channel increases, the shock wave / boundary layer effect intensifies, and the separation zone near the lower wall of the turn increases. At the same expansion ratio, increasing the offset can improve flow separation in the turn caused by an excessively large expansion ratio. While ensuring the overall layout and volume ratio are met, properly selecting the expansion ratio and offset based on actual application is beneficial to the turning flow of the airflow in the turn section and can effectively improve the internal flow field and backpressure resistance of the isolator.

Claims

1. A three-dimensional curved isolation section structure with a turning section, characterized by: It includes an isolation section, a turning section and a transition section connecting the two sections. The front of the isolation section is the isolation section entrance, and the rear of the turning section is the turning section exit. The isolation section is a straight section of the profile extending from the isolation section entrance to the transition section, and the turning section is a turning section of the profile extending from the transition section to the turning section exit. The straight section of the profile refers to the upper profile line or lower profile line of any longitudinal section of the upper profile or lower profile of the isolation section, which is a straight line, and the turning section of the profile refers to the upper profile line or lower profile line of any longitudinal section of the upper profile or lower profile of the turning section, which is a curve.

2. The three-dimensional curved isolation section structure with a turning section according to claim 1, characterized in that: The isolation section is formed by the throat height H of the front part of the air inlet th As dimensionless parameters, the geometric surface parameters are dimensionless, and the inlet profile height H is isolated. ent =H th , the expansion ratio H is satisfied between the isolating section outlet profile and the isolating section inlet profile DS-out / H th >1. Offset Y e ≤1.

3. The three-dimensional curved isolation section structure with a turning section according to claim 2, characterized in that: Expansion ratio H DS-out / H th It is 1.4 to 1.

8.

4. The three-dimensional curved isolation section structure with a turning section according to claim 1, characterized in that: The side walls of the isolation section and the turning section are rounded.

5. A design method for a three-dimensional curved isolation segment structure with a turning segment according to any one of claims 1 to 4, characterized in that: The following steps are involved: Determine the height, position and center point of the two-dimensional profile of the symmetry plane by given inlet cross section (3) and outlet cross section (4); The isolating section outlet profile (8) having a certain expansion ratio and offset from the isolating section inlet profile is determined as a transition curve. According to the upper and lower vertices of the two-dimensional profile, the isolating section inlet profile (6) and the isolating section outlet profile (8) are connected by a straight line as the symmetric surface profile of the upper and lower walls of the isolating section. The isolating section outlet and the turning section outlet are connected by a curve as the symmetric surface profile of the upper and lower walls of the turning section. The isolating section outlet profile (8) of the symmetric surface is used as the object and rotated counterclockwise around the central axis (9) by a certain angle to obtain the isolating section outlet section (5) as the transition section of the three-dimensional model; the wall profile on the symmetric surface is used as the object and the isolating section inlet section (3), the isolating section outlet section (5) and the upper wall surface of the combustion chamber inlet section (4) are used as guide lines for sweeping, thereby obtaining the upper wall surface and the lower wall surface of the isolating section and the turning section; the upper and lower wall surfaces of the isolating section and the turning section are used as the objects and the side wall profiles of the isolating section inlet section (3), the isolating section outlet section (5) and the combustion chamber inlet section (4) are used as guide lines for sweeping, and then a variable radius edge filleting process is performed to obtain the side wall surface (14) of the isolating section and the side wall surface (15) of the turning section.

6. The design method according to claim 5, characterized in that: The transition section is formed by rotating the isolating section outlet profile line counterclockwise around the central axis at a certain rotation angle Z with a certain offset and expansion ratio from the isolating section inlet profile line. e Get, adjust Z e Controls the shrinkage of the side walls of the isolation section.

Images