Cooling channel with partitioned micro-rib structure for enhancing heat exchange and design method of cooling channel

Abstract

The invention discloses a cooling channel with a partitioned micro-rib structure for enhancing heat exchange and a design method of the cooling channel, and belongs to the field of scramjet engine design. The cooling channel comprises a micro-rib structure and a smooth channel, wherein the micro-rib structure is arranged in the interval that the supercritical hydrocarbon fuel of the regenerative cooling channel is lower than the quasi-critical temperature, and the smooth channel is arranged in the interval that the supercritical hydrocarbon fuel of the regenerative cooling channel is higher than the quasi-critical temperature. The design method comprises the following steps: simulating enhanced heat exchange and pressure loss effects of the micro-ribs in a small section of channel only containing a single micro-rib, and selecting the sizes of the micro-ribs; solving a quasi-critical temperature interval of the regenerative cooling channel according to the thermal environment of the regenerative cooling channel; the length of a low-temperature section below the quasi-critical temperature is estimated based on the equivalent constant-pressure specific heat capacity of the supercritical hydrocarbon fuel, micro-ribs are added to the low-temperature section, micro-ribs are not added to the high-temperature section, and a subarea micro-rib adding channel is obtained. According to the energy conservation analysis method based on the fuel quasi-critical temperature interval, the regenerative cooling channel is subjected to subarea micro-rib arrangement, and effective enhanced heat exchange under low pressure loss is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of scramjet engine design, and in particular relates to a cooling channel with a partitioned micro-rib structure for enhanced heat exchange and a design method thereof. Background Art

[0002] Hypersonic aircraft with a flight speed greater than Mach 5 have high flight speed and penetration capability, and have become a research hotspot in the civil and military fields of various countries. As the power system of hypersonic aircraft, the scramjet engine provides sufficient thrust to ensure that the aircraft can fly at high speed. However, under high Mach number flight, the temperature of the outer wall of the scramjet engine combustion chamber can reach 2500K, far exceeding the temperature resistance limit of metal materials. The regenerative cooling channel system that uses fuel to cool the combustion chamber wall is a prerequisite for the stable operation of the scramjet engine. The micro-rib structure used in the regenerative cooling channel system can increase the turbulence of the fluid on the one hand, and on the other hand, it can make the fluid flow to the wall where the micro-rib structure is located, which can effectively enhance the heat exchange and is an important way to improve the heat exchange capacity of the fuel in the cooling channel. However, the micro-rib structure will cause a certain amount of pressure loss on the other hand. At present, most of the micro-rib structures in the regenerative cooling channel are not considered in the design of the micro-rib structure, and it is difficult to achieve a satisfactory heat exchange effect. Summary of the invention

[0003] In order to solve the problem that the existing regenerative cooling channels with micro-rib structures are generally ribbed throughout the channel, and there is an inability to balance the enhanced heat exchange capacity of the micro-rib structure and the additional pressure loss, the present invention provides a cooling channel with partitioned micro-rib structure for enhanced heat exchange and a design method thereof. The present invention arranges the regenerative cooling channel with partitioned micro-ribs based on the energy conservation analysis method of the pseudo-critical temperature range of the fuel, thereby achieving effective enhanced heat exchange under low pressure loss.

[0004] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0005] The present invention provides a cooling channel with a partitioned micro-rib structure for enhanced heat exchange, comprising: a micro-rib structure arranged in a temperature range below the pseudo-critical temperature of supercritical hydrocarbon fuel in the regenerative cooling channel and a smooth channel arranged in a temperature range above the pseudo-critical temperature of supercritical hydrocarbon fuel in the regenerative cooling channel.

[0006] Furthermore, the micro-rib structure is a triangular prism micro-rib structure with an aspect ratio of 1.2.

[0007] The present invention provides a method for designing a cooling channel with a partitioned micro-fin structure for enhanced heat exchange, comprising the following steps:

[0008] Step S1: simulating the enhanced heat transfer and pressure loss effect of micro-fins in a small section of the channel containing only a single micro-fin, and selecting the size of the micro-fin;

[0009] Step S2: solving the pseudo-critical temperature range of the regenerative cooling channel according to the thermal environment of the regenerative cooling channel;

[0010] Step S3: estimating the length of the low-temperature section below the pseudo-critical temperature based on the equivalent constant-pressure specific heat capacity of supercritical hydrocarbon fuel, adding micro-ribs to the low-temperature section and not adding micro-ribs to the high-temperature section, to obtain a zoned micro-ribbed channel.

[0011] Furthermore, in step S2, the lower limit T of the pseudo-critical temperature range is pr1 , and the upper limit T pr2 )pass is defined as, ρ is the density, and T is the temperature.

[0012] Furthermore, in step S2, the energy conservation equation in the regenerative cooling channel is:

[0013]

[0014] Among them, q heated is the heat flux density of the heating surface, w heated is the width of the heating surface, l rib is the length of the partition to be solved plus the micro-rib channel, is the equivalent specific heat capacity at constant pressure, is the mass flow rate, ΔT is the inlet temperature T in The lower limit of the pseudo-critical temperature range T pr1 The difference.

[0015] Further, in step S3, the supercritical hydrocarbon fuel has an equivalent constant pressure specific heat capacity of Select the pseudo-critical temperature range (T pr1 ,T pr2 )The arithmetic mean of the specific heat capacity at constant pressure, that is:

[0016]

[0017] Among them, c p is the specific heat at constant pressure.

[0018] Furthermore, in step S3, the calculation formula of the partition plus micro-rib channel length is:

[0019]

[0020] Among them, q heated is the heat flux density of the heating surface, w heated is the width of the heating surface, is the equivalent specific heat capacity at constant pressure, is the mass flow rate, ΔT is the inlet temperature T in The lower limit of the pseudo-critical temperature range T pr1The difference is , d is the channel width, and G is the mass flow rate.

[0021] The beneficial effects of the present invention are:

[0022] The present invention provides a cooling channel with partitioned micro-rib structure for enhanced heat exchange and a design method thereof, which can meet the requirements of enhanced heat exchange under low pressure loss conditions. The present invention partitions the regeneration cooling channel based on the energy conservation analysis method of the pseudo-critical temperature range of supercritical hydrocarbon fuels, arranges partitioned micro-rib channels (triangular prism micro-rib structure with an aspect ratio of 1.2) in the low-temperature section, and arranges a cooling channel structure with smooth pipes in the high-temperature section, which can effectively reduce the degree of heat exchange deterioration and reduce additional flow resistance, and achieve a more satisfactory enhanced heat exchange effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The cross-sectional views of a smooth channel, a full-section micro-ribbed channel, and a partitioned micro-ribbed channel designed by the present invention are shown in FIG. (a) Smooth channel; (b) Full-section micro-ribbed channel; (c) Partitioned micro-ribbed channel designed by the present invention.

[0024] Figure 2 The geometric structure of the regenerative cooling channel. In the figure, (a) is a schematic diagram of the longitudinal section of the regenerative cooling channel; (b) is a schematic diagram of the cross section of the regenerative cooling channel.

[0025] Figure 3 Schematic diagram of a single micro-fin structure. In the figure, (a) single micro-fin regenerative cooling channel; (b) schematic diagram of micro-fin structure.

[0026] Figure 4 The temperature distribution along the heating surface of the smooth channel, the whole section micro-ribbed channel and the zoned micro-ribbed channel designed by the present invention. In the figure, (a) the temperature distribution along the working condition A; (b) the temperature distribution along the working condition B; (c) the temperature distribution along the working condition C; (d) the temperature distribution along the working condition D; (e) the pressure loss distribution along the working condition E; (f) the temperature enlarged diagram of the micro-ribs of the optimized structure channel.

[0027] Figure 5 The pressure loss distribution along the smooth channel, the whole section micro-ribbed channel and the partitioned micro-ribbed channel designed by the present invention. In the figure, (a) pressure loss distribution along the working condition A; (b) pressure loss distribution along the working condition B; (c) pressure loss distribution along the working condition C; (d) pressure loss distribution along the working condition D; (e) pressure loss distribution along the working condition E. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0029] The cumulative effect of the additional pressure loss caused by the micro-fin structure in the multi-micro-fin structure cannot be ignored, and the purpose of the regenerative cooling channel to enhance the heat exchange structure is to reduce the degree of heat exchange deterioration caused by supercritical hydrocarbon fuel near the quasi-critical temperature. Therefore, in order to meet the technical requirements, the present invention proposes a cooling channel with partitioned micro-fin structure to enhance heat exchange and a design method thereof.

[0030] The present invention discloses a method for designing a cooling channel with a partitioned micro-rib structure to enhance heat exchange. The main design idea is to use a micro-rib structure to enhance heat exchange in a supercritical hydrocarbon fuel temperature range below the pseudo-critical temperature, and to use a smooth structure to reduce flow resistance in a supercritical hydrocarbon fuel temperature range above the pseudo-critical temperature. The cross-sectional diagrams of a smooth channel, a full-section micro-ribbed channel, and a partitioned micro-ribbed channel designed by the present invention are shown in FIG. Figure 1 The specific design process includes the following steps:

[0031] Step S1: simulating the enhanced heat transfer and pressure loss effect of micro-fins in a small section of the channel containing only a single micro-fin, and selecting the size of the micro-fin;

[0032] Step S2: Solve the quasi-critical temperature range of the regenerative cooling channel according to the thermal environment of the regenerative cooling channel. The energy conservation equation in the regenerative cooling channel is as follows:

[0033]

[0034] Among them, q heated is the heat flux density of the heating surface, w heated is the width of the heating surface, l rib is the length of the partition to be solved plus the micro-rib channel, is the equivalent specific heat capacity at constant pressure, Δ is the mass flow rate, ΔT is the inlet temperature T in The lower limit of the pseudo-critical temperature range T pr1 The difference between the pseudo-critical temperature range (T pr1 ,T pr2 ) in the lower limit T pr1 and upper limit T pr2 )pass is defined as, ρ is the density, and T is the temperature.

[0035] Step S3: Based on the equivalent constant pressure specific heat capacity of supercritical hydrocarbon fuel, the length of the low temperature section below the pseudo-critical temperature is estimated, micro-ribs are added to the low temperature section, and no micro-ribs are added to the high temperature section, thereby obtaining a zoned micro-ribbed channel; equivalent constant pressure specific heat capacity Select the pseudo-critical temperature range (T pr1 ,T pr2 )The arithmetic mean of the specific heat capacity at constant pressure, that is:

[0036]

[0037] Among them, c p is the specific heat capacity at constant pressure, d is the channel width, and T is the temperature.

[0038] The length l of the partition plus micro-rib channel can be obtained by solving the above formulas (1) and (2): rib The calculation formula is as follows:

[0039]

[0040] Where G is the mass flow rate.

[0041] The following will be combined with 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 making creative work are within the scope of protection of the present invention.

[0042] In the numerical simulation process, for a regenerative cooling channel with a length of 600 mm, a hydraulic diameter of 1.2 mm, a wall thickness of 0.4 mm, and a cross-sectional side length of 2.0 mm, an insulated inlet and outlet section with a length of 150 mm was added at both ends, such as Figure 2 The cooling medium is n-decane, the flow rate is 1.88 g / s, the experimental section is heated on the ground, and the heat flux is 2.5 MW / m 2 Firstly, a single section of 60 mm in the regenerative cooling channel was selected for numerical simulation to select the micro-rib size. The n-decane with inlet temperatures of 400 K, 600 K, and 800 K was selected respectively. The rib height e of the micro-rib structure was rib =0.1mm, rib width w of micro-rib structure rib The range of variation is 0.02mm~0.24mm, such as Figure 3 shown.

[0043] After calculation, it is found that the heat transfer enhancement effect of a single micro-rib structure with an aspect ratio of 1.2 on supercritical hydrocarbon fuels exceeding the pseudo-critical temperature is 11.15%, but it causes an additional pressure loss of 4%; the heat transfer enhancement effect of a single micro-rib structure with an aspect ratio of 1.2 on supercritical hydrocarbon fuels at the pseudo-critical temperature reaches 36.87%, while causing an additional pressure loss of 3.6%; the heat transfer enhancement effect of a single micro-rib structure with an aspect ratio of 1.2 on supercritical hydrocarbon fuels below the pseudo-critical temperature reaches 20.68%, while causing an additional pressure loss of 2.4%. In summary, the micro-rib structure with a single aspect ratio of 1.2 has the best heat transfer enhancement effect on supercritical hydrocarbon fuels below the pseudo-critical temperature. On this basis, according to the above formula (3), the partitioned micro-rib channel l can be solved rib About 425mm.

[0044] When the heat flux is 2.5~3.5MW / m 2 , inlet speed is 1.75~2.25m / s, bottom surface heating or top surface heating, pressure 3MPa, a total of five groups of working conditions (working conditions are: working condition A: 2.5MW / m 2 , 1.75m / s, bottom heating; Condition B: 3.0MW / m 2 , 1.75m / s, bottom heating; working condition C: 3.0MW / m 2 , 2.25m / s, bottom heating; working condition D: 3.5MW / m 2 , 1.75m / s, bottom heating; working condition E: 3.5MW / m 2 , 1.75m / s, top surface heating) to verify the enhanced heat transfer effect of a cooling channel with a partitioned micro-rib structure for enhanced heat transfer designed by the present invention. Figure 4 As shown in the figure, the temperature distribution of the heating surface of the smooth channel, the whole section micro-ribbed channel and the partitioned micro-ribbed channel designed by the present invention is very similar to the temperature distribution of the partitioned micro-ribbed channel and the whole section micro-ribbed channel in the micro-rib interval, which can delay the position of the starting point of heat exchange deterioration and reduce the temperature peak of the heat exchange deterioration section by 100-150K to protect the regenerative cooling channel from thermal ablation. Figure 5 As shown in the figure, the partitioned micro-ribbed channel designed by the present invention can significantly reduce the additional pressure loss of the fluid. The pressure loss of the micro-ribbed section of the partitioned micro-ribbed channel designed by the present invention is greater than that of the corresponding smooth channel, while the pressure loss of the smooth section is less than that of the corresponding smooth channel, which shows that the early disturbance effect helps to reduce the pressure loss downstream. This phenomenon makes the 3.5MW / m 2 Under working conditions, the partitioned and micro-ribbed channels designed by the present invention only incur an additional pressure loss of 1.7% compared with the smooth channels, but achieve the effect of enhanced heat exchange.

[0045] In summary, the present invention arranges a triangular prism micro-fin structure with an aspect ratio of 1.2 in the low-temperature section of the regeneration cooling channel and arranges a smooth channel in the high-temperature section, which can effectively reduce the degree of heat exchange deterioration and reduce the additional flow resistance.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cooling channel with partitioned micro-fin structure to enhance heat exchange, characterized in that: include: A micro-rib structure is arranged in a temperature range where the supercritical hydrocarbon fuel of the regenerative cooling channel is lower than a pseudo-critical temperature, and a smooth channel is arranged in a temperature range where the supercritical hydrocarbon fuel of the regenerative cooling channel is higher than a pseudo-critical temperature.

2. The cooling channel with partitioned micro-fin structure for enhanced heat exchange according to claim 1, characterized in that: The micro-rib structure is a triangular prism micro-rib structure with an aspect ratio of 1.

2.

3. A method for designing a cooling channel with a partitioned micro-fin structure for enhanced heat exchange as claimed in claim 1 or 2, characterized in that: The following steps are involved: Step S1: simulating the enhanced heat transfer and pressure loss effect of micro-fins in a small section of the channel containing only a single micro-fin, and selecting the size of the micro-fin; Step S2: solving the pseudo-critical temperature range of the regenerative cooling channel according to the thermal environment of the regenerative cooling channel; Step S3: estimating the length of the low-temperature section below the pseudo-critical temperature based on the equivalent constant-pressure specific heat capacity of supercritical hydrocarbon fuel, adding micro-ribs to the low-temperature section and not adding micro-ribs to the high-temperature section, to obtain a zoned micro-ribbed channel.

4. The design method of a cooling channel with partitioned micro-fin structure for enhanced heat exchange according to claim 3, characterized in that: In step S2, the lower limit T of the pseudo-critical temperature range is pr1 , and the upper limit T pr2 )pass is defined as, ρ is the density, and T is the temperature.

5. The design method of a cooling channel with partitioned micro-fin structure for enhanced heat exchange according to claim 3, characterized in that: In step S2, the energy conservation equation in the regenerative cooling channel is: Among them, q heated is the heat flux density of the heating surface, w heated is the width of the heating surface, l rib is the length of the partition to be solved plus the micro-rib channel, is the equivalent specific heat capacity at constant pressure, Δ is the mass flow rate, ΔT is the inlet temperature T in The lower limit of the pseudo-critical temperature range T pr1 The difference.

6. The design method of a cooling channel with partitioned micro-fin structure for enhanced heat exchange according to claim 3, characterized in that: In step S3, the supercritical hydrocarbon fuel equivalent constant pressure specific heat capacity Select the pseudo-critical temperature interval (T pr1 ,T pr2 ) is the arithmetic mean of the specific heat capacity at constant pressure, that is: Among them, c p is the specific heat at constant pressure.

7. The design method of a cooling channel with partitioned micro-fin structure for enhanced heat exchange according to claim 3, characterized in that: In step S3, the calculation formula of the partition plus micro-rib channel length is: Among them, q heated is the heat flux density of the heating surface, w heated is the width of the heating surface, is the equivalent specific heat capacity at constant pressure, Δ is the mass flow rate, ΔT is the inlet temperature T in The lower limit of the pseudo-critical temperature range T pr1 The difference is , d is the channel width, and G is the mass flow rate.

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