A design method and structure of a rectangular active cooling channel

Abstract

The present invention belongs to the field of air-breathing ramjet engine cooling, and specifically relates to a rectangular active cooling channel design method and structure, including the following steps: obtaining the heat flux distribution of the flow channel in the engine; obtaining the required cross-sectional parameters of the highest temperature position and the lowest temperature position of the cooling channel; constructing a cooling channel width calculation model according to the preset cross-sectional parameters of the highest temperature position and the lowest temperature position of the cooling channel and the heat flux density of the highest temperature position and the lowest temperature position of the flow channel in the engine; substituting the heat flux density of each position in the flow direction of the flow channel in the engine into the cooling channel width calculation model, calculating the width of each position of the cooling channel along the flow direction, and constructing a cooling channel configuration according to the required cross-sectional area and the width of each position obtained. The present invention reasonably allocates the effective heat exchange area, and can gradually improve the heat exchange capacity of the system as the heat flux density increases, thereby achieving higher thermal protection performance.

Description

Technical Field

[0001] The invention belongs to the field of air-breathing ramjet engine cooling, and in particular relates to a design method and structure of a rectangular active cooling channel. Background Art

[0002] The impact of the heat load of the inner flow channel on the air-breathing ramjet engine can easily cause structural deformation, and also cause the operating temperature of the components to exceed the rated range. Therefore, the thermal protection problem has become the key to restricting the long-term reliable operation of the engine. There are two main types of thermal protection technologies, namely passive cooling using high-temperature resistant composite materials and active cooling based on cooling fluids. In actual engineering problems, the thermal protection technology combining active / passive cooling is more often used. Considering the high cost of high-temperature resistant composite materials and the maximum withstand temperature of about 2000K, it is difficult to achieve thermal protection of the entire engine system under high Mach flight conditions. Regenerative cooling using liquid fuel as a working fluid is considered to be one of the most promising engine thermal protection technologies at present. The recovered heat can continue to participate in work, thereby improving the global performance of the propulsion system.

[0003] Existing cooling channels mainly adopt fixed geometric configuration schemes, the cross-sectional area along the flow direction remains unchanged, and is evenly distributed around the engine. For details, please refer to Figure 1 . This scheme adopts a rectangular cooling channel with equal cross-section. Its most significant advantage is that the geometric configuration is simple and easy to process and produce. It can be realized using traditional machining technology, which can significantly save costs. However, the effective heat exchange area between the cooling medium and the inner flow channel in the fixed geometric configuration scheme is relatively fixed, that is, the convective heat transfer capacity of the entire flow channel system is basically the same. However, the heat flux density in the actual engine gradually changes along the flow direction, especially in the combustion chamber where the heat flux density is very high. The existing scheme will cause the coolant to absorb more heat in the low heat flux density area, resulting in insufficient heat absorption capacity in the high heat flux area, so the local maximum temperature of the structure is too large. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a design method and structure of a rectangular active cooling channel that is adapted to the heat flow distribution of an engine inner flow channel for adaptive cooling.

[0005] The present invention provides a rectangular active cooling channel design method, comprising the following steps:

[0006] Obtaining heat flux distribution in the flow channel of the engine, the heat flux distribution including heat flux density in the flow direction of the flow channel of the engine;

[0007] Determine the maximum value of the heat flux density and the highest temperature position of the flow channel in the engine, and the minimum value of the heat flux density and the lowest temperature position of the flow channel in the engine;

[0008] Obtaining required cross-sectional parameters of the highest temperature position of the cooling channel and the lowest temperature position of the cooling channel, wherein the required cross-sectional parameters include a required cross-sectional area and a required width;

[0009] A cooling channel width calculation model is constructed according to preset cross-sectional parameters of the highest temperature position and the lowest temperature position of the cooling channel and the heat flux density of the highest temperature position and the lowest temperature position of the flow channel in the engine, wherein the cooling channel width obtained in the cooling channel width calculation model is proportional to the heat flux density and ensures that the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction;

[0010] The heat flux density at each position in the flow direction of the engine flow channel is substituted into the cooling channel width calculation model to calculate the width of the cooling channel at each position along the flow direction, and the cooling channel configuration is constructed according to the required cross-sectional area and the width of each position obtained.

[0011] Furthermore, the cooling channel configuration is constructed according to the required cross-sectional area and the widths at each position obtained:

[0012] Any cross section of the cooling channel configuration is rectangular.

[0013] Furthermore, the cooling channel configuration is constructed according to the required cross-sectional area and the widths at each position obtained:

[0014] Ensure that the cooling channel close to the engine inner flow channel is at a consistent distance from the engine inner wall.

[0015] Furthermore, the required cross-sectional area in the required cross-sectional parameters includes:

[0016] The required cross-sectional area is calculated based on the flow rate of the cooling channel and the required density and required velocity of the cooling medium.

[0017] Furthermore, determining the maximum heat flux density and the highest temperature position of the flow channel in the engine includes:

[0018] The highest temperature position is the cooling channel outlet position.

[0019] Furthermore, determining the minimum heat flux density and the lowest temperature position of the flow channel in the engine includes:

[0020] The lowest temperature position is the cooling channel entrance position.

[0021] The present invention also provides a rectangular active cooling channel structure, including an engine inner wall, wherein a cooling channel is arranged in the engine inner wall, the width of the cooling channel is proportional to the heat flux density of the flow channel in the engine, and the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction.

[0022] Furthermore, the cooling channel is close to the inner flow channel of the engine and has a consistent distance from the inner wall of the engine.

[0023] Furthermore, any cross section of the cooling channel is rectangular.

[0024] Furthermore, a plurality of cooling channels are arranged in a ring array along the axis of the inner wall of the engine.

[0025] The beneficial effect of the present invention is that, under the condition of ensuring that the cross-sectional area of ​​the cooling pipeline remains unchanged, the present invention allocates the width of the cooling channel according to the heat flux density of the engine, and then reasonably allocates the effective heat exchange area, which can gradually improve the heat exchange capacity of the system as the heat flux density increases, thereby achieving higher thermal protection performance, and reasonably allocating the heat dissipation efficiency according to the spatial characteristics of the engine structure temperature, and finally achieving the requirement of reducing the local maximum temperature, solving the problem that the conventional cooling channel causes the refrigerant to absorb too much heat at low heat flux density, resulting in insufficient heat absorption capacity in the high heat flux area. In addition, ensuring that the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction can ensure that the side wall of the flow channel in the engine meets the strength requirements, and at the same time ensure that the flow velocity in the pipe does not change with the cross section. In addition, the length of the cooling channel of the present invention remains unchanged. Without changing the overall layout of the cooling system and without introducing other structures, the purpose of reducing the local maximum temperature of the structure is achieved by changing the size of the cooling channel, thereby reducing the cost of cooling structure design and processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attached Figure 1 This is a schematic diagram of the structure of a conventional cooling channel.

[0027] Attached Figure 2 It is a schematic diagram of the structure of the cooling channel of the present invention.

[0028] Attached Figure 3 It is the temperature distribution cloud diagram on the central cross section of the conventional cooling channel and the cooling channel of the present invention.

[0029] Attached Figure 4 It is the temperature distribution cloud diagram of the bottom wall of the conventional cooling channel and the cooling channel of the present invention.

[0030] Attached Figure 5 It is a schematic diagram of the process of the present invention.

[0031] In the figure, 1-inner wall of engine; 2-cooling channel. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0037] As attached Figure 1-5 As shown, the present invention provides a rectangular active cooling channel design method, comprising the following steps:

[0038] Obtaining the heat flux distribution of the engine inner flow channel, the heat flux distribution includes the heat flux density in the flow direction of the engine inner flow channel, the engine inner flow channel refers to the flow channel space in the engine inner wall, the cooling channel can be attached to the outer side of the engine inner wall, preferably directly arranged in the engine inner wall, the heat flux density distribution of the engine inner flow channel is consistent with the distribution of heat on the engine inner wall;

[0039] Determine the maximum value of the heat flux density and the highest temperature position of the flow channel in the engine, and the minimum value of the heat flux density and the lowest temperature position of the flow channel in the engine;

[0040] Obtaining the required cross-sectional parameters of the highest temperature position and the lowest temperature position of the cooling channel, wherein the required cross-sectional parameters are standard cross-sectional parameters set to meet the basic requirements of heat dissipation, so as to ensure that the cooling medium flowing into the cross-sectional area can take away the required heat from the engine and ensure the normal use of the engine, and the required cross-sectional parameters include the required cross-sectional area and the required width;

[0041] A cooling channel width calculation model is constructed according to preset cross-sectional parameters of the highest temperature position and the lowest temperature position of the cooling channel and the heat flux density of the highest temperature position and the lowest temperature position of the flow channel in the engine, and the cooling channel width obtained in the cooling channel width calculation model is proportional to the heat flux density; the cross-sectional area of ​​the cooling channel is ensured to remain unchanged along the flow direction, so the cross-sectional area is required to be the area of ​​any cross section of the cooling channel;

[0042] The calculation model of cooling channel width is:

[0043]

[0044] Among them, w x is the cooling channel width at the position to be determined, q max is the maximum heat flux density, q min is the minimum heat flux density, q x is the heat flux density of the engine at the position to be determined, a is q min The required width of the location, b is q max The required width of the location.

[0045] In this way, the heat flux density at each position in the flow direction of the flow channel in the engine is substituted into the cooling channel width calculation model, and the width of the cooling channel at each position along the flow direction can be calculated. Since the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction, and the width of the cooling channel at each position is calculated by the cooling channel width calculation model, the height of the cooling channel at each position can be calculated, and then a cooling channel configuration suitable for this heat flux distribution is constructed according to the required cross-sectional area and the width of each position. This cooling channel configuration can dissipate more heat in the high heat flux density area.

[0046] Under the condition that the cross-sectional area of ​​the cooling pipeline remains unchanged, the present invention allocates the width of the cooling channel according to the heat flux density of the engine, and then reasonably allocates the effective heat exchange area, which can gradually improve the heat exchange capacity of the system as the heat flux density increases, thereby achieving higher thermal protection performance, and reasonably allocating the heat dissipation efficiency according to the spatial characteristics of the engine structure temperature, and finally achieving the requirement of reducing the local maximum temperature, solving the problem that the conventional cooling channel causes the refrigerant to absorb too much heat at low heat flux density, resulting in insufficient heat absorption capacity in the high heat flux area. In addition, ensuring that the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction can ensure that the side wall of the flow channel in the engine meets the strength requirements, and at the same time ensure that the flow velocity in the pipe does not change with the cross section. In addition, the length of the cooling channel of the present invention remains unchanged. Without changing the overall layout of the cooling system and without introducing other structures, the purpose of reducing the local maximum temperature of the structure is achieved by changing the size of the cooling channel, thereby reducing the cost of cooling structure design and processing.

[0047] In one embodiment, the cooling channel configuration is constructed according to the required cross-sectional area and the width of each position obtained:

[0048] Any cross section of the cooling channel configuration is rectangular. The cooling channel adopts a rectangular structure, which is convenient for rapid design and processing, thereby reducing design and production costs.

[0049] In one embodiment, the cooling channel configuration is constructed according to the required cross-sectional area and the width of each position obtained:

[0050] Ensure that the cooling channel close to the engine inner flow channel is at a consistent distance from the engine inner wall, that is, the lower surface of the rectangular cooling channel is always kept horizontal and the normal direction points to the inside of the engine, thereby ensuring the heat absorption efficiency of the cooling channel.

[0051] In one embodiment, the required cross-sectional area in the required cross-sectional parameters includes:

[0052] The required cross-sectional area is calculated based on the flow rate of the cooling channel and the required density and required speed of the cooling medium. Specifically, since the cross-sectional area, flow rate and cooling medium satisfy the following formula:

[0053]

[0054] Where A is the cross-sectional area, is the flow rate of a single cooling channel, ρ is the density of the cooling medium, and u is the speed of the cooling medium. In this embodiment, the required cross-sectional area can be obtained according to the flow rate required by the heat flux density and the density and flow rate required by the cooling medium. At the same time, since the cross-sectional area A remains unchanged along the flow direction, the flow rate at each position in the cooling channel is It remains unchanged to achieve control of a single variable, thus ensuring that the flow rate of the cooling medium is only a function of the temperature and does not depend on changes in the profile, which further explains that the heat transfer result will change with the heat transfer area.

[0055] In one embodiment, determining the maximum heat flux density and the highest temperature position of the flow channel in the engine includes:

[0056] The highest temperature position is the cooling channel outlet position.

[0057] In one embodiment, determining the minimum heat flux density and the lowest temperature position of the flow channel in the engine includes:

[0058] The lowest temperature position is the cooling channel entrance position.

[0059] The present invention also provides a rectangular active cooling channel structure, including an engine inner wall 1, wherein a plurality of cooling channels 2 are arranged in the engine inner wall 1, wherein the width of the cooling channel 2 is proportional to the heat flux density of the flow channel in the engine, and the cross-sectional area of ​​the cooling channel 2 remains unchanged along the flow direction.

[0060] Under the condition that the cross-sectional area of ​​the cooling pipeline remains unchanged, the present invention allocates the width of the cooling channel 2 according to the heat flux density of the engine, and then reasonably allocates the effective heat exchange area, which can gradually improve the heat exchange capacity of the system as the heat flux density increases, thereby achieving higher thermal protection performance, and reasonably allocating the heat dissipation efficiency according to the spatial characteristics of the engine structure temperature, and finally achieving the requirement of reducing the local maximum temperature, solving the problem that the conventional cooling channel 2 causes the refrigerant to absorb too much heat at low heat flux density, resulting in insufficient heat absorption capacity in the high heat flux area. In addition, ensuring that the cross-sectional area of ​​the cooling channel 2 remains unchanged along the flow direction can ensure that the side wall of the flow channel in the engine meets the strength requirements, and at the same time ensure that the flow velocity in the pipe does not change with the cross section. In addition, the length of the cooling channel 2 of the present invention remains unchanged, and the purpose of reducing the local maximum temperature of the structure is achieved by changing the size of the cooling channel 2 without changing the overall layout of the cooling system and without introducing other structures.

[0061] The cooling channel 2 is close to the inner flow channel of the engine and is at the same distance from the inner wall of the engine, that is, the lower surface of the rectangular cooling channel 2 is always kept horizontal and the normal direction points to the inside of the engine, ensuring the heat absorption efficiency of the cooling channel 2. The cross section of any part of the cooling channel 2 is rectangular, and the cooling channel 2 adopts a rectangular structure, which is convenient for rapid design and processing, and reduces the design and production costs. The cooling channels 2 are arranged in a ring array along the axis of the inner wall of the engine to improve the overall heat dissipation efficiency of the engine.

[0062] Taking the linear distribution of heat flux density of the engine as an example, the heat flux density of the engine combustion chamber gradually increases from the inlet to the outlet, that is, the heat flux density at the inlet of the combustion chamber is the smallest, and the heat flux density at the outlet of the combustion chamber is the largest. The configuration design of the cooling channel 2 is as follows: Figure 2 The specific design method is as follows:

[0063] The heat flux distribution in the flow channel of the air-breathing ramjet engine is determined by theoretical calculation or experimental acquisition. The heat flux density satisfies a linear relationship with the width of the cooling channel 2. The calculation model is based on the width of the cooling channel 2:

[0064]

[0065] It can be seen that the width of the cooling channel 2 gradually widens from the inlet direction to the outlet direction of the cooling channel 2, while the height of the cooling channel 2 (the length of the short axis of the rectangle) gradually decreases from the inlet direction to the outlet direction of the cooling channel 2.

[0066] There are several cooling channels arranged in a circular array along the engine axis. The total coolant flow required by the cooling system is given according to the thermodynamic cycle analysis. Calculate the flow rate of a single channel

[0067]

[0068] Where N is the number of cooling channels 2. The inlet and outlet cross-sectional area A can be estimated based on the physical parameters of the cooling channel inlet position and the design flow rate:

[0069]

[0070] Where ρ and u are the density and velocity of the cooling medium at the inlet, respectively. The area A is determined at the beginning of the design, and the solid area A is a constant.

[0071] In order to reduce flow resistance and facilitate processing, the upper boundary of the cross section adopts an axisymmetric line segment f z For a fixed area geometry,

[0072]

[0073] According to the geometric characteristics of the rectangle, the area is calculated as follows:

[0074] A=w x h

[0075] Where h is the length of the minor axis of the rectangle, we can get:

[0076]

[0077] According to the cross-sectional width w of the cooling channel 2 x The variation of the height h along the flow direction and the determination of the rectangular configuration can generate the following Figure 2 The structure of the cooling channel 2 with a fixed area and variable geometry depending on the wall heat flux density is shown.

[0078] After numerical simulation verification, Figure 2 The inlet profile of the fixed area variable geometry cooling channel 2 shown is a 3×3mm square, the outlet profile is a 4.5×2mm rectangle, the total length is 380mm, the flow rate of supercritical kerosene on the inlet section of the cooling channel 2 is 0.018kg / s, the pressure is 3.0MPa, the temperature is 333K, the average heat flux density of the lower wall is 815kW, and other boundaries are treated according to adiabatic no-slip conditions. The average temperature distribution cloud diagram on the central section of the conventional cooling channel 2 of the present invention is compared with the average temperature distribution cloud diagram on the central section of the conventional cooling channel 2 of the present invention. Figure 3 As shown, the temperature distribution of the bottom wall of the conventional cooling channel 2 and the bottom wall of the cooling channel 2 of the present invention is compared. Figure 4 As shown, the temperature on the bottom wall of the present invention is significantly reduced, and more heat can be taken away.

[0079] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A rectangular active cooling channel design method, characterized in that: The steps include: Obtaining heat flux distribution in the flow channel of the engine, the heat flux distribution including heat flux density in the flow direction of the flow channel of the engine; Determine the maximum value of the heat flux density and the highest temperature position of the flow channel in the engine, and the minimum value of the heat flux density and the lowest temperature position of the flow channel in the engine; Obtaining required cross-sectional parameters of the highest temperature position of the cooling channel and the lowest temperature position of the cooling channel, wherein the required cross-sectional parameters include a required cross-sectional area and a required width; A cooling channel width calculation model is constructed according to preset cross-sectional parameters of the highest temperature position and the lowest temperature position of the cooling channel and the heat flux density of the highest temperature position and the lowest temperature position of the flow channel in the engine, wherein the cooling channel width obtained in the cooling channel width calculation model is proportional to the heat flux density and ensures that the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction; The cooling channel width calculation model is: ； in, is the cooling channel width at the position to be determined, is the maximum value of heat flux density, is the minimum heat flux density, is the heat flux density of the engine at the position to be determined, for The required width of the location, for The required width of the location; The heat flux density at each position in the flow direction of the engine flow channel is substituted into the cooling channel width calculation model to calculate the width of the cooling channel at each position along the flow direction, and the cooling channel configuration is constructed according to the required cross-sectional area and the width of each position obtained.

2. The rectangular active cooling channel design method according to claim 1, characterized in that: The cooling channel configuration is constructed based on the required cross-sectional area and the width at each location: Any cross section of the cooling channel configuration is rectangular.

3. The rectangular active cooling channel design method according to claim 2, characterized in that: The cooling channel configuration is constructed based on the required cross-sectional area and the width at each location: Ensure that the cooling channel close to the engine inner flow channel is at a consistent distance from the engine inner wall.

4. The method for designing a rectangular active cooling channel according to any one of claims 1 to 3, characterized in that: The required cross-sectional area in the required cross-sectional parameters includes: The required cross-sectional area is calculated based on the flow rate of the cooling channel and the required density and required velocity of the cooling medium.

5. The rectangular active cooling channel design method according to any one of claims 1 to 3, characterized in that: Determining the maximum heat flux density and the highest temperature position in the engine flow channel includes: The highest temperature position is the cooling channel outlet position.

6. The rectangular active cooling channel design method according to any one of claims 1 to 3, characterized in that: Determining the minimum heat flux density and the lowest temperature position in the engine flow channel includes: The lowest temperature position is the cooling channel entrance position.

7. A rectangular active cooling channel structure designed using the rectangular active cooling channel design method according to any one of claims 1 to 6, characterized in that: It comprises an inner wall of an engine, wherein a cooling channel is arranged in the inner wall of the engine, wherein the width of the cooling channel is proportional to the heat flux density of the flow channel in the engine, and the cross-sectional area of ​​the cooling channel remains unchanged along the flow direction.

8. The rectangular active cooling channel structure according to claim 7, characterized in that: The cooling channel is close to the inner flow channel of the engine and has a consistent distance from the inner wall of the engine.

9. The rectangular active cooling channel structure according to claim 8, characterized in that: The cross section of the cooling channel at any location is rectangular.

10. The rectangular active cooling channel structure according to any one of claims 7 to 9, characterized in that: A plurality of cooling channels are arranged in a ring array along the axis of the inner wall of the engine.

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