A liquid hydrogen subcooling system and method for an inner-parallel hybrid scramjet and ramjet combined power system

Abstract

The application discloses a liquid hydrogen staged cooling system and method of an inner-parallel turbofan scramjet combined power system, and belongs to the technical field of combined cycle propulsion and hydrogen fuel thermal management of hypersonic aircrafts. The combined power system shares a downstream air inlet section to form a turbofan channel and a scramjet channel through an adjustable splitter plate. Liquid hydrogen is first cooled by a liquid hydrogen wall cooler arranged on the upstream of the bifurcated flow channel of the shared air inlet section to complete the first stage heat exchange, and then enters a pre-cooling hydrogen supply branch or a regenerative cooling hydrogen supply branch according to the working mode. In the turbofan mode, low-temperature hydrogen enters a low-temperature hydrogen pre-cooler before the fan to pre-cool the fan inlet air. In the scramjet mode, low-temperature hydrogen enters a hydrogen fuel regenerative cooling channel to absorb the heat of the heated wall and then participates in combustion. Through the cooperation of the adjustable splitter plate and the flow regulating mechanism of the two branches, the air flow and the liquid hydrogen cooling capacity are coordinately distributed according to the working mode, and the thermal management support is provided for the thrust relay of the two types of engines.

Description

Technical Field

[0001] This invention relates to the field of combined cycle propulsion and hydrogen fuel thermal management technology for hypersonic vehicles, specifically to a liquid hydrogen staged cooling system and method for an internally parallel turbofan scramjet combined propulsion system. Background Technology

[0002] Turbine-based combined cycle engines leverage the performance advantages of turbine engines and ramjet engines across different flight speed ranges. The turbine engine handles propulsion during low- to medium-high speed flight phases, while the scramjet engine handles propulsion during higher speed phases. For combined propulsion systems employing parallel flow path structures, the two types of engines need to switch operating modes and relay thrust within a certain flight speed range.

[0003] As flight speed increases, the shared air intake section is significantly affected by aerodynamic heating, leading to a continuous rise in the fan inlet temperature of the turbofan channel and a high thermal load on the combustion chamber walls of the scramjet channel. The increased fan inlet temperature reduces the high Mach number operating margin of the turbofan engine, while the scramjet combustion chamber's heated walls require continuous thermal protection. Therefore, the shared air intake walls, the fan inlet air, and the scramjet combustion chamber's heated walls have different cooling requirements.

[0004] In existing combined cycle power systems using liquid hydrogen as a cold source, precooling heat exchange and combustion chamber regeneration cooling are typically set up separately for different heat load targets. If different cooling targets are configured with independent hydrogen supply paths, there is no clear sequential relationship between the utilization of liquid hydrogen cooling capacity in different cooling stages, and the coordination between the hydrogen supply diversion location and the propulsion mode switching is weak. This makes it difficult to coordinate the basic thermal protection of the shared heating area and the targeted cooling of the current working channel within the same hydrogen supply topology. At the same time, multiple independent cooling paths also increase the complexity of pipeline layout, flow regulation, and mode switching control.

[0005] Liquid hydrogen serves as both a propulsion fuel and possesses a relatively low storage temperature and strong heat absorption capacity. If the cooling capacity of liquid hydrogen is utilized in stages according to a clear sequence, such that before entering the secondary cooling units corresponding to different propulsion channels, liquid hydrogen is first used for basic cooling of the shared intake section's heated walls, and then, downstream of this common primary heat exchange unit, it enters the corresponding secondary heat exchange branch based on either the turbofan or scramjet operating mode, then shared thermal protection, mode-dependent cooling, and subsequent fuel supply can be unified into a single hydrogen supply topology.

[0006] Therefore, there is a need for a liquid hydrogen staged cooling system and method that uses a common intake section liquid hydrogen wall cooler as a common primary heat exchange unit, performs mode selection and diversion after the first stage of heat exchange is completed, and matches the pre-cooling branch in front of the fan or the regenerative cooling branch of the scramjet combustion chamber with the working mode of the combined power system. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a liquid hydrogen staged cooling system and method for an internally parallel turbofan scramjet combined power system, in order to solve the problem that the shared intake section heating wall, the turbofan fan inlet air and the scramjet combustion chamber heating wall in the combined power system have different thermal management requirements, and the hydrogen cooling capacity is difficult to coordinate and distribute according to the working mode.

[0008] This invention sets up a common intake section liquid hydrogen wall cooler as a shared primary heat exchange unit for both the pre-cooling hydrogen supply branch and the regenerative cooling hydrogen supply branch. Before entering the two mode-dependent secondary cooling branches, the liquid hydrogen first absorbs heat from the shared intake section heating wall and completes the first stage of heat exchange. After completing the first stage of heat exchange, the cryogenic hydrogen then enters the cryogenic hydrogen pre-cooler before the fan or the hydrogen fuel regenerative cooling channel in the scramjet combustion chamber, depending on the combined power system's operating mode. This forms a series-branched cooling utilization path of "common primary heat exchange - primary heat exchange followed by branching - mode-dependent secondary heat exchange - heat exchange followed by combustion," ensuring continuous connection between the basic cooling of the shared heating area and the targeted cooling under different propulsion modes within the same hydrogen supply topology.

[0009] Technical solution: A liquid hydrogen staged cooling system for an internally parallel turbofan scramjet combined power system, comprising a liquid hydrogen storage and supply unit, a common intake section liquid hydrogen wall cooler, a cryogenic hydrogen supply pipeline, a pre-cooling hydrogen supply branch, a regenerative cooling hydrogen supply branch, a cryogenic hydrogen pre-cooler in front of the fan, a hydrogen fuel regenerative cooling channel, and flow regulation mechanisms respectively installed on the pre-cooling hydrogen supply branch and the regenerative cooling hydrogen supply branch.

[0010] The combined power system includes a common intake section, a turbofan channel, and a scramjet channel. A flow channel bifurcation point is located downstream of the common intake section, and an adjustable splitter plate is installed at the flow channel bifurcation point. The turbofan channel and the scramjet channel are respectively connected to the split outlet downstream of the common intake section, forming an internal parallel flow channel structure after the common intake section.

[0011] The pre-cooled hydrogen in front of the fan is located in the turbofan channel and before the fan inlet of the afterburning turbofan engine; the hydrogen fuel regeneration cooling channel is located at the heated wall of the scramjet chamber in the scramjet channel.

[0012] The liquid hydrogen storage and supply unit includes a liquid hydrogen storage tank and a hydrogen supply pump. A shared inlet section liquid hydrogen wall cooler is located at the heated wall surface of the shared inlet section, upstream of the flow channel bifurcation point. The liquid hydrogen outlet of the liquid hydrogen storage and supply unit is connected to the inlet of the shared inlet section liquid hydrogen wall cooler, and the outlet of the shared inlet section liquid hydrogen wall cooler is connected to a cryogenic hydrogen supply pipeline. The cryogenic hydrogen supply pipeline forms a branch point downstream of the shared inlet section liquid hydrogen wall cooler and is connected to both a pre-cooling hydrogen supply branch and a regeneration cooling hydrogen supply branch.

[0013] Therefore, the shared inlet section liquid hydrogen wall cooler constitutes a common primary heat exchange unit for both the pre-cooling hydrogen supply branch and the regenerative cooling hydrogen supply branch. Hydrogen fuel supplied to any secondary cooling branch first passes through the shared inlet section liquid hydrogen wall cooler, absorbing heat from the heated walls of the shared inlet section and completing the first stage of heat exchange. Only then is it diverted downstream according to the combined power system operating mode, thus ensuring that the common primary cooling is retained in different propulsion modes.

[0014] The precooling hydrogen supply branch is connected to the hydrogen fuel inlet of the low-temperature hydrogen precooler in front of the fan, and the hydrogen fuel outlet of the low-temperature hydrogen precooler in front of the fan is connected to the main combustion chamber and the afterburner of the turbofan engine through the hydrogen fuel distribution pipeline.

[0015] The regenerative cooling hydrogen supply branch is connected to the inlet of the hydrogen fuel regenerative cooling channel, and the outlet of the hydrogen fuel regenerative cooling channel is connected to the hydrogen supply port of the supercombustion combustion chamber through the supercombustion hydrogen supply branch.

[0016] The pre-cooling hydrogen supply branch and the regenerative cooling hydrogen supply branch are each equipped with a flow regulation mechanism. The adjustable splitter plate is used to regulate the airflow distribution into the turbofan channel and the scramjet channel, and the flow regulation mechanisms on the two hydrogen supply branches are used to regulate the hydrogen fuel flow into the corresponding secondary heat exchange unit. In turbofan operating mode, the adjustable splitter plate ensures that the incoming flow mainly enters the turbofan channel, the pre-cooling hydrogen supply branch is in hydrogen supply mode, and the regenerative cooling hydrogen supply branch is closed or has its flow reduced. In scramjet operating mode, the adjustable splitter plate ensures that the incoming flow mainly enters the scramjet channel, the regenerative cooling hydrogen supply branch is in hydrogen supply mode, and the pre-cooling hydrogen supply branch is closed or has its flow reduced. During the transition between the two operating modes, as the adjustable splitter plate gradually changes the airflow distribution between the two channels, the hydrogen supply flow of the two hydrogen supply branches is continuously adjusted accordingly, so that the pre-cooling demand before the fan is gradually reduced and the regenerative cooling demand of the scramjet combustion chamber is gradually established, thereby achieving a coordinated match between the airflow distribution in the propulsion channel and the liquid hydrogen cooling capacity distribution.

[0017] Furthermore, the shared intake section liquid hydrogen wall cooler has a liquid hydrogen wall cooling channel disposed inside or adjacent to the heated wall of the shared intake section, through which liquid hydrogen indirectly exchanges heat with the incoming air in the shared intake section. In a preferred embodiment, the flow direction of liquid hydrogen in the liquid hydrogen wall cooling channel is opposite to the flow direction of the incoming air in the shared intake section, forming a counter-current heat exchange relationship. The low-temperature hydrogen precooler before the fan adopts a partitioned heat exchange structure, in which low-temperature hydrogen flows inside the heat exchange tube and the air in the turbofan channel flows outside the heat exchange tube, so that the two working fluids exchange heat through the tube wall and do not mix directly. The hydrogen fuel regeneration cooling channel forms a heat exchange relationship with the heated wall of the supercombustion chamber and is not directly connected to the combustion gas in the supercombustion chamber.

[0018] Furthermore, an adjustable lip mask is installed at the inlet of the common intake section, an adjustable splitter is installed at the bifurcation position of the flow channel downstream of the common intake section, and adjustable tail nozzles are installed in the turbofan channel and scramjet channel respectively, so as to distribute airflow in accordance with different working modes and rectify the non-working channel.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The common intake section liquid hydrogen wall cooler is set as a common primary heat exchange unit for two mode-dependent hydrogen supply branches. This allows the liquid hydrogen to complete the basic cooling of the common heated parts before entering either secondary cooling branch, forming a series-branched cold energy utilization topology of "common primary heat exchange first, then mode-selective diversion". This helps to reduce the system complexity caused by configuring independent hydrogen supply circuits for different cooling objects.

[0021] 2. By coordinating the adjustable flow divider with the flow regulation mechanisms of the two hydrogen supply branches, the air flow distribution and liquid hydrogen cooling capacity distribution are adjusted synchronously with the working mode of the combined power system, thereby ensuring the continuous existence of shared basic cooling and prioritizing the use of secondary cooling capacity for the main heat load objects in the current working propulsion channel, thus improving the matching degree between the cooling objects, hydrogen supply paths and propulsion modes.

[0022] 3. In the same hydrogen supply topology, the heat absorption capacity of liquid hydrogen at different heat exchange stages is continuously utilized to successively undertake the cooling of the shared intake section heated wall and the pre-cooling of the fan air or the regeneration cooling of the scramjet combustion chamber, which are related to the mode. This enables the staged utilization of the liquid hydrogen cold source and allows the hydrogen fuel after heat exchange to continue to be used in the corresponding combustion process.

[0023] 4. In turbofan operation mode, low-temperature hydrogen precooling before the fan can reduce the air temperature at the fan inlet, improving the adaptability of afterburning turbofan engines at higher flight Mach numbers; in scramjet operation mode, hydrogen fuel regeneration cooling can absorb heat from the heated walls of the combustion chamber, improving the thermal protection conditions of the high-speed passage.

[0024] 5. By continuously connecting the common primary cooling and mode-dependent secondary cooling, the pre-cooling requirement before the fan can be gradually reduced and the regenerative cooling requirement of the scramjet combustion chamber can be gradually established during the switching of the combined power system's operating mode, providing thermal management conditions that are coordinated with the propulsion mode for the thrust relay between the afterburning turbofan engine and the scramjet engine. Attached Figure Description

[0025] Figure 1 This is a general configuration diagram of the present invention.

[0026] exist Figure 1The components are labeled as follows: 1. Forebody; 2. Adjustable splitter; 3. Turbofan channel; 4. Cryogenic hydrogen precooler in front of the fan; 5. Afterburning turbofan engine; 6. Aftbody; 7. Adjustable turbofan nozzle; 8. Adjustable scramjet nozzle; 9. Scramjet combustion chamber; 10. Hydrogen fuel regeneration cooling channel; 11. Isolation section; 12. Scramjet channel; 13. Common inlet liquid hydrogen wall cooler; 14. Adjustable lip.

[0027] Figure 2 This is a diagram illustrating the working mode of the turbofan engine of the present invention.

[0028] Figure 3 This is a diagram illustrating the working mode of the superheated ramming process of the present invention.

[0029] Figure 4 This is a schematic diagram of the liquid hydrogen flow path and staged cooling system of the present invention.

[0030] exist Figure 4 The components are labeled as follows: 4. Pre-cooled hydrogen in front of the fan; 9. Scrammed combustion chamber; 10. Hydrogen fuel regeneration cooling channel; 13. Common intake section liquid hydrogen wall cooler; 15. Liquid hydrogen storage tank; 16. Hydrogen supply pump; 17. Liquid hydrogen supply branch; 18. Cryogenic hydrogen supply pipeline; 19. Pre-cooling hydrogen supply branch; 20. Hydrogen fuel distribution pipeline; 21. Main combustion chamber hydrogen supply branch; 22. Afterburner hydrogen supply branch; 23. Regeneration cooling hydrogen supply branch; 24. Scrammed hydrogen supply branch; 25. Turbofan engine main combustion chamber; 26. Afterburner.

[0031] Figure 5 This is a partial structural schematic diagram of the liquid hydrogen wall cooler for the common intake section of the present invention.

[0032] exist Figure 5 The markings are as follows: 27, common air intake section airflow channel; 28, common air intake section heated wall surface; 29, liquid hydrogen wall cooling channel; 30, cryogenic hydrogen outlet; 31, liquid hydrogen inlet.

[0033] Figure 6 This is a schematic diagram of the internal heat exchange structure of the low-temperature hydrogen precooler in front of the fan of the present invention.

[0034] exist Figure 6 The following are the markings: 32, air side channel; 33, cryogenic hydrogen heat exchange tube; 34, air inlet; 35, air outlet; 36, cryogenic hydrogen inlet; 37, hydrogen outlet after heat exchange.

[0035] Figure 7 This is a partial structural diagram of the regenerative cooling system of the supercombustion chamber of the present invention.

[0036] exist Figure 7The markings are as follows: 38, combustion gas side; 39, combustion chamber heated wall; 40, regeneration cooling channel; 41, hydrogen fuel outlet; 42, hydrogen fuel inlet.

[0037] Figure 8 This diagram illustrates the combined effects of the inlet section liquid hydrogen wall cooler, the fan-front cryogenic hydrogen precooler, and the supercombustion chamber regenerative cooling in an embodiment of the present invention. Figure 8 (a) Cooling effect of the heated wall surface of the shared inlet section liquid hydrogen wall cooler. Figure 8 (b) shows the air precooling effect of the low-temperature hydrogen precooler in front of the fan. Figure 8 (c) shows the hydrogen fuel regeneration cooling effect in the scramjet combustion chamber.

[0038] Figure 9 This is an extended diagram showing the usable thrust range of an afterburning turbofan engine under pre-cooling conditions in an embodiment of the present invention.

[0039] Figure 10 This is a comparison diagram of the available thrust of the combined propulsion system and the acceleration thrust requirement of the aircraft in an embodiment of the present invention. Detailed Implementation

[0040] The specific embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that these embodiments are used to illustrate the technical solutions of the present invention, and not to limit the scope of protection of the present invention.

[0041] In this specification, directional terms such as "front," "rear," "up," and "down" are used to describe the relative positions of the components based on the directions shown in the accompanying drawings. "Cryogenic hydrogen" refers to cryogenic hydrogen fuel that retains its heat-absorbing capacity even after heat exchange. Under the calculation conditions of this embodiment, the liquid hydrogen absorbs heat through the shared intake section liquid hydrogen wall cooler to form cryogenic gaseous hydrogen, which then continues to enter the pre-cooling hydrogen supply branch or the regeneration cooling hydrogen supply branch.

[0042] I. Overall Structure of Combined Power System

[0043] like Figure 1As shown, the combined propulsion system of this embodiment includes an aircraft forebody 1, an adjustable splitter 2, a turbofan channel 3, a pre-cooled cryogenic hydrogen preheater 4, an afterburning turbofan engine 5, an aircraft aftbody 6, an adjustable turbofan nozzle 7, an adjustable scramjet nozzle 8, a scramjet combustion chamber 9, a hydrogen fuel regeneration cooling channel 10, an isolation section 11, a scramjet channel 12, a common intake section liquid hydrogen wall cooler 13, and an adjustable lip 14. The adjustable lip 14 is located at the inlet of the common intake section. After being compressed by the aircraft forebody 1, the incoming air enters the common intake section, and the intake geometry and capture flow rate are changed by the adjustable lip 14. The common intake section liquid hydrogen wall cooler 13 is located at the heated wall surface of the common intake section. Liquid hydrogen flows along the cooling channel provided inside or adjacent to the wall surface and indirectly exchanges heat with the heated area through the wall surface. In this embodiment, the flow direction of liquid hydrogen in the wall cooling channel is opposite to the direction of the incoming air in the common air intake section, and a counter-current heat exchange arrangement is adopted.

[0044] The adjustable splitter 2 is located at the downstream bifurcation position of the common intake section. The turbofan channel 3 and the scramjet channel 12 are respectively connected to the common intake section, forming an internal parallel structure; by changing the position of the adjustable splitter 2, the airflow distribution between the two channels can be adjusted.

[0045] Along the airflow direction, the turbofan channel 3 is sequentially equipped with a pre-cooled hydrogen heater 4, an afterburning turbofan engine 5, and an adjustable turbofan nozzle 7. The pre-cooled hydrogen heater 4 is located before the fan inlet of the afterburning turbofan engine 5 and employs a tubular indirect heat exchange structure. The cryogenic hydrogen and the air in the turbofan channel exchange indirectly through the heat exchange tube walls, thus lowering the temperature of the air entering the fan. Its internal heat exchange structure is as follows: Figure 6 As shown. The afterburning turbofan engine 5 includes a turbofan engine main combustion chamber 25 and an afterburning combustion chamber 26 located downstream therefrom.

[0046] like Figure 6 As shown, the pre-cooled hydrogen inlet 4 includes an air-side flow channel 32 and a low-temperature hydrogen heat exchange tube 33 disposed within the air-side flow channel 32. Air enters the air-side flow channel 32 through the air inlet 34, flows outside the low-temperature hydrogen heat exchange tube 33, and exchanges heat with the low-temperature hydrogen inside the tube. After pre-cooling, it flows out through the air outlet 35. Low-temperature hydrogen enters the low-temperature hydrogen heat exchange tube 33 through the low-temperature hydrogen inlet 36, flows inside the tube, absorbs heat from the air, and flows out through the hydrogen outlet 37 after heat exchange. The low-temperature hydrogen and air are separated by the tube wall of the low-temperature hydrogen heat exchange tube 33, and direct mixing does not occur.

[0047] exist Figure 6 In the embodiment shown, the low-temperature hydrogen heat exchange tube 33 is formed by arranging multiple U-shaped tube segments along the air flow direction to form a heat exchange tube bundle. Figure 6For ease of illustration, only one layer of U-shaped heat exchange tubes is shown. In actual implementation, multiple layers of U-shaped heat exchange tubes can be arranged in a direction perpendicular to the plane shown, depending on the heat exchange load, the cross-sectional dimensions of the air-side flow channel 32, and the allowable pressure drop. The heat exchange tubes in each layer together constitute the low-temperature hydrogen heat exchange tube bundle. The number of U-shaped heat exchange tube layers, the tube spacing, and the arrangement can be adjusted according to the heat exchange requirements. The structure shown does not constitute a limitation on the specific number of layers and arrangement of the heat exchange tube bundle.

[0048] The scramjet channel 12 is sequentially arranged with an isolation section 11, a scramjet combustion chamber 9, and a scramjet adjustable tail nozzle 8 along the airflow direction. The hydrogen fuel regenerative cooling channel 10 is located at the heated wall surface of the scramjet combustion chamber 9, and its local regenerative cooling structure is as follows: Figure 7 As shown, hydrogen fuel absorbs heat from the heated walls of the combustion chamber in the regenerative cooling channel before entering the scramjet combustion chamber 9 to participate in combustion.

[0049] like Figure 7 As shown, the combustion gas side 38 of the supercombustion chamber is located on one side of the combustion chamber heating wall 39. The regenerative cooling channel 40 is located on the side of the combustion chamber heating wall 39 opposite to the combustion gas side 38 and forms direct heat transfer contact with the combustion chamber heating wall 39. The high-temperature gas generated by combustion exchanges heat with the combustion chamber heating wall 39, and the heat is transferred from the combustion gas side 38 through the combustion chamber heating wall 39 to the hydrogen fuel in the regenerative cooling channel 40. The hydrogen fuel enters the regenerative cooling channel 40 through the hydrogen fuel inlet 42 located on the right and flows from right to left. During the flow, it absorbs heat from the combustion chamber heating wall 39 and flows out through the hydrogen fuel outlet 41 located on the left after heat exchange. The regenerative cooling channel 40 and the combustion gas side 38 are separated by the combustion chamber heating wall 39, and the hydrogen fuel does not come into direct contact with the combustion gas. Figure 7 The diagram only shows a partial structure of a single regenerative cooling channel. In actual implementation, multiple regenerative cooling channels can be arranged in parallel or continuously according to the heat load of the combustion chamber and the structural dimensions.

[0050] II. Liquid Hydrogen Series-Branched Staged Cooling Flow Path

[0051] like Figure 4 As shown, the liquid hydrogen in the liquid hydrogen storage tank 15 is pressurized by the hydrogen supply pump 16 and then enters the common intake section liquid hydrogen wall cooler 13 through the liquid hydrogen supply branch 17; its local heat exchange structure is as follows: Figure 5 As shown. Liquid hydrogen enters the liquid hydrogen wall cooling channel 29 through the liquid hydrogen inlet 31, absorbs the heat from the shared inlet section heated wall 28, and after completing the first stage of heat exchange, flows out through the cryogenic hydrogen outlet 30 and enters the cryogenic hydrogen supply pipeline 18.

[0052] like Figure 5As shown, a shared intake section heating wall 28 is formed on one side of the shared intake section airflow channel 27. A liquid hydrogen wall cooling channel 29 is located on the side of the shared intake section heating wall 28 away from the airflow channel 27 and is in direct contact with it. In the illustrated embodiment, the incoming air in the shared intake section flows from left to right along the airflow channel 27, while liquid hydrogen enters the liquid hydrogen wall cooling channel 29 from the right liquid hydrogen inlet 31 and flows from right to left, forming a counter-current indirect heat exchange. Heat from the air is transferred to the liquid hydrogen in the liquid hydrogen wall cooling channel 29 via the shared intake section heating wall 28. The liquid hydrogen absorbs heat and heats up during its flow, and may undergo a phase change. The cooled hydrogen after heat exchange flows out from the left cooled hydrogen outlet 30. The liquid hydrogen and the incoming air are separated by the shared intake section heating wall 28, preventing direct mixing. The liquid hydrogen inlet 31 is connected to the liquid hydrogen supply branch 17, and the cooled hydrogen outlet 30 is connected to the cooled hydrogen supply pipeline 18.

[0053] The cryogenic hydrogen supply line 18 has a branch point downstream of the common inlet section liquid hydrogen wall cooler 13, and connects to the pre-cooling hydrogen supply branch 19 and the regeneration cooling hydrogen supply branch 23 respectively. Therefore, the common inlet section liquid hydrogen wall cooler 13 is not arranged in parallel with the two secondary heat exchange units, but is located upstream of the two mode-related secondary heat exchange branches; in any operating mode, the liquid hydrogen first completes the first stage heat exchange on the heated wall of the common inlet section, and then selects the corresponding second stage heat exchange path according to the operating mode.

[0054] The pre-cooling hydrogen supply branch 19 is connected to the low-temperature hydrogen inlet 36 of the low-temperature hydrogen precooler 4 before the fan. After the low-temperature hydrogen is pre-cooled and heat-exchanged through the low-temperature hydrogen heat exchange tube 33, it enters the hydrogen fuel distribution pipeline 20 through the heat exchange hydrogen outlet 37, and is supplied to the main combustion chamber 25 and the afterburner combustion chamber 26 of the turbofan engine through the main combustion chamber hydrogen supply branch 21 and the afterburner hydrogen supply branch 22, respectively.

[0055] The regenerative cooling hydrogen supply branch 23 is connected to the hydrogen fuel inlet 42 of the hydrogen fuel regenerative cooling channel 10. Low-temperature hydrogen enters the regenerative cooling channel 40 through the hydrogen fuel inlet 42, absorbs the heat from the combustion chamber heated wall 39 of the supercombustion chamber 9, flows out through the hydrogen fuel outlet 41, and enters the supercombustion chamber 9 through the supercombustion hydrogen supply branch 24 to participate in combustion.

[0056] The pre-cooling hydrogen supply branch 19 and the regenerative cooling hydrogen supply branch 23 are each equipped with a flow regulation mechanism. This flow regulation mechanism, in conjunction with the adjustable splitter plate 2, adjusts the hydrogen supply flow of the two branches and the air flow entering the turbofan channel 3 and the scramjet channel 12, respectively, so that the low-temperature hydrogen after the first-stage heat exchange enters the corresponding second-stage heat exchange unit according to the combined power system's operating mode. Thus, the basic thermal protection and mode-dependent cooling of the shared heating area form a continuous series-branched cooling capacity utilization relationship, rather than independent cooling loops.

[0057] III. Turbofan Operating Mode

[0058] like Figure 2 As shown, in turbofan operating mode, the adjustable splitter 2 is in the position where the turbofan channel is open, the scramjet channel is closed, or the flow rate is low. After passing through the common intake section, the airflow mainly enters the turbofan channel 3.

[0059] Liquid hydrogen first undergoes the first stage of heat exchange through the common intake section liquid hydrogen wall cooler 13; then the pre-cooling hydrogen supply branch 19 is in the hydrogen supply state, the regeneration cooling hydrogen supply branch 23 is closed or the flow rate is reduced, and the low-temperature hydrogen enters the low-temperature hydrogen pre-cooler 4 before the fan to perform indirect heat exchange on the air before the fan inlet.

[0060] After pre-cooling and heat exchange, the hydrogen fuel is distributed through the hydrogen fuel distribution pipeline 20 and supplied to the main combustion chamber 25 and afterburner combustion chamber 26 of the turbofan engine through the main combustion chamber hydrogen supply branch 21 and the afterburner hydrogen supply branch 22, respectively. At this time, the turbofan adjustable tail nozzle 7 opens, and the scramjet adjustable tail nozzle 8 can retract to form a straightened shape.

[0061] IV. Supercharged stamping working modes and mode switching

[0062] like Figure 3 As shown, in the scramjet operating mode, the adjustable splitter 2 is in the position where the turbofan channel is closed or the flow rate is low and the scramjet channel is open. After passing through the common intake section, the incoming flow mainly enters the scramjet channel 12.

[0063] Liquid hydrogen first undergoes the first stage of heat exchange through the common intake section liquid hydrogen wall cooler 13; then the regeneration cooling hydrogen supply branch 23 is in hydrogen supply mode, the pre-cooling hydrogen supply branch 19 is closed or the flow rate is reduced, and low-temperature hydrogen enters the regeneration cooling channel 40 from the hydrogen fuel inlet 42, absorbs the heat from the combustion chamber heated wall 39 of the supercombustion chamber 9, and flows out from the hydrogen fuel outlet 41, and enters the supercombustion chamber 9 through the supercombustion hydrogen supply branch 24 to participate in combustion.

[0064] During the transition from turbofan to scramjet operation, the adjustable splitter 2 gradually adjusts the airflow distribution into the turbofan channel 3 and the scramjet channel 12. Simultaneously, the hydrogen supply flow of the pre-cooling hydrogen supply branch 19 and the regenerative cooling hydrogen supply branch 23 is continuously adjusted accordingly. This causes the pre-cooling demand before the fan to gradually decrease as the airflow in the turbofan channel decreases, while the regenerative cooling demand in the scramjet combustion chamber gradually increases as the airflow in the scramjet channel increases. Thus, the transition of airflow in the propulsion channel corresponds to the distribution of liquid hydrogen cooling capacity between the two secondary cooling branches. After the thrust takeover is completed, the adjustable scramjet nozzle 8 remains open, while the adjustable turbofan nozzle 7 closes and transitions seamlessly with the shape of the rear body 6 of the aircraft.

[0065] V. Calculation Examples of Cooling Effect and Propulsion Performance

[0066] In one computational embodiment, the cooling effects of the shared intake section liquid hydrogen wall cooler 13, the fan-front cryogenic hydrogen precooler 4, and the hydrogen fuel regeneration cooling channel 10 were calculated, and the results are as follows: Figure 8 As shown. Figure 8 (a) indicates that after the liquid hydrogen wall cooling of the common intake section is turned on, the temperature of the heated wall of the common intake section is significantly reduced, indicating that liquid hydrogen wall cooling can effectively improve the thermal state of the heated wall of the common intake section. Figure 8 (b) indicates that the air temperature in front of the fan is significantly reduced under a given hydrogen supply flow rate; Figure 8 (c) indicates that within the indicated flight Mach number range, after the hydrogen fuel flows through the regenerative cooling channel 10 and absorbs the heat from the heated wall surface of the scramjet combustion chamber, the temperature of the heated wall surface is lower than that of the uncooled state, indicating that regenerative cooling can reduce the temperature of the heated wall surface of the scramjet combustion chamber and improve its thermal state.

[0067] Furthermore, the thrust of an afterburning turbofan engine under pre-cooling is calculated as a function of flight Mach number, and the results are as follows: Figure 9 As shown, when the afterburning turbofan engine is pre-cooled with cryogenic hydrogen before the fan is turned on, its high-speed operating range is limited by factors such as the inlet temperature; after the pre-cooling is turned on, the inlet air temperature of the fan decreases, and the afterburning turbofan engine still has usable thrust under higher flight Mach numbers.

[0068] A comparison was made between the available thrust of the combined propulsion system and the acceleration thrust requirements of the aircraft, and the results are as follows: Figure 10 As shown. In this calculation embodiment, cryogenic hydrogen precooling before the fan is used to broaden the high-speed operating range of the afterburning turbofan engine. Subsequently, the scramjet engine gradually builds up thrust and completes thrust takeover, thereby forming a thrust relay range between the two types of engines.

Claims

1. A liquid hydrogen staged cooling system for an internally parallel turbofan scramjet combined propulsion system, characterized in that, It includes a liquid hydrogen storage and supply unit, a common inlet section liquid hydrogen wall cooler, a cryogenic hydrogen supply pipeline, a pre-cooling hydrogen supply branch, a cryogenic hydrogen pre-cooler in front of the fan, a regenerative cooling hydrogen supply branch, a hydrogen fuel regenerative cooling channel, and flow regulation mechanisms respectively installed in the pre-cooling hydrogen supply branch and the regenerative cooling hydrogen supply branch. The combined power system includes a common intake section, a turbofan channel, and a scramjet channel. A flow channel bifurcation position is provided downstream of the common intake section, and an adjustable flow divider is provided at the flow channel bifurcation position. The turbofan channel and the scramjet channel are respectively connected to the flow outlet downstream of the common intake section to form an internal parallel flow channel structure after the common intake section. The common intake section liquid hydrogen wall cooler is located at the heated wall surface of the common intake section and upstream of the flow channel bifurcation position. The liquid hydrogen outlet of the liquid hydrogen storage and supply unit is connected to the inlet of the common intake section liquid hydrogen wall cooler, and the outlet of the common intake section liquid hydrogen wall cooler is connected to the cryogenic hydrogen supply pipeline. The cryogenic hydrogen supply pipeline forms a branch position downstream of the liquid hydrogen wall cooler in the common intake section, and is connected to the pre-cooling hydrogen supply branch and the regeneration cooling hydrogen supply branch respectively, so that the hydrogen fuel supplied to the pre-cooling hydrogen supply branch or the regeneration cooling hydrogen supply branch first absorbs the heat of the heated wall surface of the common intake section through the liquid hydrogen wall cooler in the common intake section, thus completing the first stage of heat exchange. The pre-cooled hydrogen precooler is located in the turbofan channel and before the fan inlet of the afterburning turbofan engine. The precooling hydrogen supply branch is connected to the inlet of the pre-cooled hydrogen precooler, and the outlet of the pre-cooled hydrogen precooler is connected to the main combustion chamber and the afterburning combustion chamber of the afterburning turbofan engine, respectively. The hydrogen fuel regeneration cooling channel is located at the heated wall surface of the supercombustion chamber within the supercombustion ramming channel. The regeneration cooling hydrogen supply branch is connected to the inlet of the hydrogen fuel regeneration cooling channel, and the outlet of the hydrogen fuel regeneration cooling channel is connected to the hydrogen supply port of the supercombustion chamber. The flow regulation mechanism works in conjunction with the adjustable splitter plate and adjusts the hydrogen supply flow of the two branches according to the working mode of the combined power system. In turbofan working mode, the precooling hydrogen supply branch is in hydrogen supply state and the regenerative cooling hydrogen supply branch is closed or the flow is reduced. In scramjet working mode, the regenerative cooling hydrogen supply branch is in hydrogen supply state and the precooling hydrogen supply branch is closed or the flow is reduced.

2. The liquid hydrogen staged cooling system for the internally parallel turbofan scramjet combined power system according to claim 1, characterized in that, During the transition from turbofan operating mode to scramjet operating mode, the adjustable splitter plate gradually adjusts the airflow distribution into the turbofan channel and the scramjet channel. The flow regulation mechanisms of the precooling hydrogen supply branch and the regenerative cooling hydrogen supply branch respectively adjust the hydrogen supply flow of the two branches, so as to gradually reduce the precooling demand in front of the fan and gradually establish the regenerative cooling demand of the scramjet combustion chamber.

3. The liquid hydrogen staged cooling system for the internally parallel turbofan scramjet combined power system according to claim 1, characterized in that: The common intake section liquid hydrogen wall cooler has a liquid hydrogen wall cooling channel disposed inside or adjacent to the heated wall of the common intake section, and the liquid hydrogen wall cooling channel indirectly exchanges heat with the incoming air in the common intake section through the heated wall of the common intake section. The low-temperature hydrogen precooler in front of the fan is a partitioned heat exchanger that prevents hydrogen fuel from directly mixing with the air in the turbofan channel. The hydrogen fuel regeneration cooling channel is heat exchanged with the heated wall surface of the supercombustion chamber, but is not directly connected to the gas inside the supercombustion chamber.

4. A method for staged cooling of liquid hydrogen in an internally parallel turbofan scramjet combined propulsion system, characterized in that, include: Liquid hydrogen first enters the common intake section liquid hydrogen wall cooler located at the common intake section heating wall, absorbs the heat from the common intake section heating wall, and after completing the first stage of heat exchange, the low-temperature hydrogen enters the low-temperature hydrogen supply pipeline. According to the working mode of the combined power system, the adjustable splitter plate located at the bifurcation position of the downstream flow channel of the common intake section is adjusted to adjust the air flow distribution into the turbofan channel and the scramjet channel, and the hydrogen supply flow of the pre-cooling hydrogen supply branch and the regeneration cooling hydrogen supply branch located downstream of the liquid hydrogen wall cooler of the common intake section is adjusted accordingly. In turbofan operation mode, the low-temperature hydrogen after completing the first stage of heat exchange enters the low-temperature hydrogen precooler before the fan inlet of the afterburning turbofan engine through the precooling hydrogen supply branch, and performs indirect heat exchange on the air before the fan inlet. The hydrogen fuel after heat exchange is supplied to the main combustion chamber and afterburning chamber of the afterburning turbofan engine. In the scramjet operating mode, the low-temperature hydrogen that has completed the first stage of heat exchange enters the hydrogen fuel regeneration cooling channel located on the heated wall of the scramjet combustion chamber through the regeneration cooling hydrogen supply branch, absorbs the heat from the heated wall of the scramjet combustion chamber, and the hydrogen fuel that has completed the heat exchange enters the scramjet combustion chamber to participate in combustion.

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