Low-energy-consumption double-flow-path wide-working-condition heat transfer characteristic experiment system

Abstract

The invention belongs to the technical field of gas turbine engine part heat transfer characteristic analysis, and relates to a low-energy-consumption double-flow-path wide-working-condition heat transfer characteristic experiment system. The effect of the turbojet engine is fully utilized, a plurality of heating and pressurizing devices are replaced, the experiment system is simplified, and the experiment cost is reduced; fuel gas generated by the turbojet engine is used as a mainstream working medium, components of the fuel gas are closer to a real engine part working environment, and an experimental result is more credible; high-temperature fuel gas is directly used as a main flow working medium, the energy conversion efficiency is high, secondary flow is heated through main flow exhaust waste heat, and energy consumption is reduced; the secondary flow temperature adjusting system is simple in structure, large in adjusting range and high in safety; according to the invention, through the combined structure design of the switching pipeline and the adjusting pore plate, the matching between the engine performance and various experiment conditions is flexibly and effectively realized; the application range of experimental working conditions is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of heat transfer characteristic analysis of gas turbine engine parts and relates to a low-energy consumption double-flow-path wide-operating-condition heat transfer characteristic experimental system. Background Art

[0002] As the performance of gas turbine engines continues to improve, the temperature of the gas before the turbine is increasing, far exceeding the temperature resistance limit of the blade material. In this extremely high temperature environment, in order to ensure the safe and long-term operation of the turbine blades, they must be efficiently cooled. Obtaining the heat transfer characteristics of turbine blades through scientific experimental methods is an indispensable part of the blade cooling structure design. Compared with numerical simulation and pipe network calculation methods, it has the advantage of being more intuitive and accurate.

[0003] In the field of heat transfer research, the dual-flow heat transfer experimental system has a wide range of applications. Typical experimental schemes include Figure 1 This type of experimental scheme has two flow paths with different pressures, flow rates and temperatures: the mainstream and the secondary flow. The mainstream flow inhales air working fluid through the mainstream fan 1 and increases its pressure, and the mainstream working fluid mass flow m is measured by the mainstream flowmeter 3. g After that, the temperature is increased by the mainstream electric heater 6, and then the working fluid enters the mainstream pressure stabilizing section 11, and after the flow is stabilized, it enters the mainstream measuring section 12, where the mainstream pressure sensor 13 and the mainstream thermocouple 14 respectively measure the mainstream inlet pressure P of the experimental section. g1 and the mainstream inlet temperature T g1 Then it enters the main channel 15 of the double-sided blowing test section, flows through both sides of the double-sided blowing test piece 27 (typically such as a hollow turbine blade), and finally is discharged from the test section pipeline outlet. The secondary flow path sucks in air working medium through the secondary flow fan 16 and increases its pressure. The secondary flow working medium mass flow m is measured by the secondary flow flow meter 17. c After that, the temperature is raised by the secondary flow electric heater 18. Then, the working fluid enters the secondary flow stabilizing section 23, and after the stabilizing flow, enters the secondary flow measuring section 24, where the secondary flow pressure sensor 25 and the secondary flow thermocouple 26 respectively measure the secondary flow inlet pressure P of the experimental section. c1 and the secondary flow inlet temperature T c1 , and then enters the internal channel of the double-sided blowing test piece 27, exchanges heat with it and flows out from the outlet of the test piece, finally merges into the mainstream and then exits the test section pipeline. During the experiment, the flow rate, pressure and temperature are continuously adjusted, and the surface temperature T of the double-sided blowing test piece 27 is w Measurements are taken (e.g. using calibrated thermocouples) to calculate and judge the quality of the experimental piece cooling design. The heated pipes of the main and secondary flows are covered with a thermal insulation layer 28 to reduce heat loss in the experimental system and prevent the experimental personnel from being burned by the high temperature pipes.

[0004] As mentioned above, the background experimental scheme generally equips the main flow path and the secondary flow path with fans and electric heaters respectively to meet the requirements of the two flow paths for the working fluid pressure and temperature. These two devices tend to have a large volume. For the electric heater, a large power supply and power control equipment are also required, which further increases the complexity of the experimental system and the required space. In addition, from the perspective of energy utilization, the process of the electric heater converting electrical energy into thermal energy and transferring it to the gas working fluid will be accompanied by a certain amount of energy loss. If the electrical energy comes from thermal power generation that burns fuel, the thermal efficiency ultimately transferred to the experimental working fluid is usually only less than 60%. From the perspective of energy loss, the heated high-temperature mainstream still has a high heat content after being discharged from the outlet of the experimental section pipeline, but the existing experimental scheme usually directly discharges it into the atmosphere without secondary utilization of energy, resulting in a complete loss of this part of the energy. In summary, the existing heat transfer experimental system has the disadvantages of complex design, large volume, high cost, and high energy consumption, and is in urgent need of improvement. Summary of the invention

[0005] In response to the above problems, the present invention provides a low-energy dual-flow path wide-operating condition heat transfer characteristic experimental system, which uses a turbojet engine as the gas source and heat source in the mainstream path, and uses a relatively small device to simultaneously replace the functions of the fan and electric heater in the background scheme, which not only meets the dual requirements of the mainstream for temperature and pressure, but also reduces the space required for the entire experimental bench. In addition, the secondary flow temperature regulation system adopted by the present invention utilizes the waste heat of the mainstream exhaust to increase and adjust the temperature of the secondary flow, eliminating the secondary flow heating device and its energy input, further simplifying the experimental system, while saving experimental costs and reducing energy consumption. Compared with the background heat transfer experimental scheme, the experimental system of the present invention reduces the length of the experimental bench pipeline and the floor space by more than 40% and reduces energy consumption by about 30% under the premise of achieving the same operating conditions.

[0006] The present invention adopts the following technical solutions:

[0007] A low-energy dual-flow wide-condition heat transfer characteristic experimental system consists of a pipeline system and a measurement and control system. The pipeline system includes two flow paths: the main flow and the secondary flow. Figure 2 As shown. Different from the background scheme using a fan and an electric heater, the main flow path of the present invention provides high-temperature and high-pressure gas working medium through a turbojet engine. After the turbojet engine is ignited, air is sucked into the pipeline through the main flow inlet section, and its mass flow m is measured after flowing through the main flow flow meter. a Then it passes through the engine inlet adapter and enters the turbojet engine. At the same time, the turbojet engine sucks fuel from the fuel tank through the fuel pump, and its mass flow rate m is measured by the fuel flow meter. f. Subsequently, the turbojet engine ejects high-temperature and high-pressure combustion gas as the mainstream working fluid into the expansion engine outlet transition section, where its pressure is increased and its flow rate is reduced by gradually expanding the cross-sectional area of ​​the pipeline along the way, and then it flows through the regulating orifice plate, where the pressure is reduced to about atmospheric pressure while maintaining the flow rate, and is rectified. Through the joint regulation of the above-mentioned transition pipeline and orifice plate structure, the mainstream meets the working conditions required for the experiment, and then the working fluid enters the mainstream pressure stabilization section, and after stabilization, it enters the mainstream measurement section, where the mainstream pressure sensor and mainstream thermocouple respectively measure the mainstream inlet pressure P of the experimental section. g1 and the mainstream inlet temperature T g1 , and then enters the main channel of the double-side blowing test section, flows through both sides of the double-side blowing test piece, and finally is discharged from the outlet of the test section pipeline.

[0008] The secondary flow path sucks in air through the secondary flow fan and increases its pressure, flows through the secondary flow flow meter and measures its mass flow m c , and then enters the spiral heat exchange tube through the metal hose. The spiral heat exchange tube is placed downstream of the main channel outlet of the double-sided blowing test section through the pipe clamping device and the displacement mechanism, and is heated by the waste heat of the mainstream exhaust gas. The displacement mechanism is used to control the depth of the spiral heat exchange tube intruding into the mainstream exhaust gas to adjust the secondary flow temperature. After passing through the spiral heat exchange tube, the secondary flow medium flows into the secondary flow stabilization section through the metal hose, and enters the secondary flow measurement section after stabilization. Here, the secondary flow inlet pressure P of the test section is measured by the secondary flow pressure sensor and the secondary flow thermocouple respectively. c1 and the secondary flow inlet temperature T c1 , and then enters the internal channel of the double-sided blowing test piece, exchanges heat with it and flows out from the outlet of the test piece, finally merges into the mainstream and is then discharged from the test section pipeline.

[0009] The pipelines after the mainstream and secondary flow heating are covered with thermal insulation layers to reduce the heat loss of the experimental system and prevent the experimenters from being scalded by the high-temperature pipelines.

[0010] The circuit connection scheme of the measurement and control system of the present invention is as follows Figure 3 The main measurement scheme includes: using mainstream flow meter, fuel flow meter and secondary flow meter to measure the mainstream intake air mass flow m a , Engine fuel mass flow m f And the secondary flow mass flow rate m c , where the mainstream inhaled air mass flow rate m a and engine fuel mass flow m f The sum is the mainstream working fluid mass flow rate m g ; The mainstream inlet pressure P of the experimental section is measured by the mainstream pressure sensor and the secondary flow pressure sensor respectively g1 and the secondary flow inlet pressure P of the experimental sectionc1 ; The mainstream inlet temperature T of the experimental section was measured by the mainstream thermocouple and the secondary flow thermocouple respectively g1 and the secondary flow inlet temperature T c1 ;Install infrared glass and infrared thermal imager above the experimental piece to measure the average wall temperature T w ; Open several thermocouple installation slots on the surface of the test piece to be tested, and bury the calibrated thermocouples to obtain the wall surface temperature T with sufficient accuracy. wi , used as a reference benchmark for the correction of infrared measurement results. Among them, the flow meter, pressure sensor and thermocouple are connected to the data acquisition instrument through signal lines, the data acquisition instrument is connected to the computer to transmit, process and store data, and the infrared thermal imager is directly connected to the computer to collect temperature field data. The main control scheme includes: controlling the speed of the secondary flow fan through the fan speed governor to achieve the regulation of the secondary flow flow; the lines of the turbojet engine and the oil pump are connected to the engine console to achieve remote control of the turbojet engine start and stop and the throttle; in addition, the position of the spiral heat exchange tube is adjusted through the displacement mechanism console.

[0011] The pipeline system and the measurement and control system maintain a sufficient safety distance in space, and effective safety protection measures are set for the turbojet engine to ensure the safety of the experimental operators.

[0012] Now combined Figure 4(a) to Figure 4(c) , the mainstream pipeline design and connection scheme after the turbojet engine in the present invention are further described. As shown in Figure 4 (a), the original tail nozzle of the turbojet engine is a convergent nozzle, which is connected to the turbine outlet of the turbojet engine. Its function is to convert the pressure energy of the fuel gas into kinetic energy, so that the nozzle outlet emits a high-speed normal-pressure airflow, thereby providing sufficient thrust. When the mainstream pipeline is not connected, that is, when the turbojet engine works alone, the pressure change along the flow direction in the original tail nozzle is shown by the dotted line in Figure 4 (c), and it is gradually reduced to atmospheric pressure along the way and then discharged into the atmosphere.

[0013] In the present invention, the original tail nozzle is removed from the adopted turbojet engine, and a new pipeline (mainstream measurement section, etc.) is designed as a replacement according to the mainstream pressure and speed requirements in the experimental section. As shown in Figure 4 (b), the turbojet engine is connected to the expansion engine outlet adapter section, and its inlet cross-section is the same as the original tail nozzle, which is a circular cross-section and is provided with a rectifying cone, and is connected to the turbine outlet of the engine; after a smooth transition, the outlet becomes a rectangular cross-section with a larger area relative to the inlet, and an expansion pipeline is formed as a whole. An adjustment orifice plate is installed after the expansion engine outlet adapter section, and its function is to provide a suitable pressure drop for the pipeline system, so that it matches the engine operation characteristics, prevents the turbine from over-rotating, and also plays a rectifying role. When the pressure drop required by the pipeline is large, a multi-layer series of adjustment orifices can be set, typically such as a straight hole adjustment orifice plate and an expansion hole adjustment orifice plate, and an orifice plate spacing adjustment flange is installed between two adjacent orifice plates, and the orifice plate spacing and airflow pressure drop are adjusted by the thickness of the flange. The pressure change along the flow direction in the mainstream pipeline refers to the solid line in Figure 4(c). When the mainstream working fluid flows through the expansion engine outlet transition section, the kinetic energy of the working fluid is converted into pressure energy due to the gradual increase in the cross-sectional area, the flow rate decreases, and the pressure increases. Then, after passing through one or more layers of regulating orifice plates, the pressure quickly decreases to near atmospheric pressure, and then enters the mainstream pressure stabilization section to maintain stable flow, providing the required low-speed and normal-pressure mainstream working conditions for the experimental section pipeline. This scheme increases the pressure in the mainstream pipeline first and then decreases, and the overall pressure drop value is the same as the original tail nozzle, thereby replacing the original tail nozzle and ensuring the safe and stable operation of the turbojet engine under the required experimental conditions.

[0014] Combination Figure 5(a) to Figure 5(b) , the structure of the regulating orifice plate is further described. As shown in FIG5(a), the regulating orifice plate is a thin plate with multiple openings in the middle area, and the openings are evenly distributed in the main channel area. The hole shape can be circular, elliptical or rectangular, etc., and along the flow direction, it can be a straight hole structure with a constant opening cross section, and the typical structure is a straight hole regulating orifice plate shown on the left side of the center line of FIG5(a), or an expansion hole structure with a gradually increasing cross-sectional area, and the typical structure is an expansion hole regulating orifice plate shown on the right side of the center line of FIG5(a). In order to ensure the pressure reduction effect, the openings of the two adjacent layers of orifice plates are arranged in a staggered manner to avoid forming a smooth air flow channel. The typical assembly scheme of the multi-layer orifice plate is shown in FIG5(b), which is connected to the front and rear pipes through flanges, and an orifice plate spacing adjustment flange is installed between the two layers of orifice plates. Along the flow direction of the working medium, the hydraulic diameter of the openings of the multi-layer orifice plate gradually decreases, and the thickness of the orifice plate spacing adjustment flange between the two adjacent layers of orifice plates gradually decreases, which can improve the pressure drop effect. As shown in Figure 4(c), for the expansion hole regulating orifice plate, since the flow area of ​​its opening gradually increases along the way, the working fluid pressure is restored to a certain extent after being drastically reduced, which has a better rectification effect and is beneficial to improving the uniformity of subsequent flow.

[0015] Furthermore, the relative aperture of the adjustment orifice plate is defined

[0016] For straight hole conditioning orifice plates,

[0017] For expansion hole adjustment orifice plate,

[0018] Where, d o is the hydraulic diameter of a single hole of the straight hole regulating orifice plate, d o1 is the hydraulic diameter of the small end of the expansion hole regulating orifice plate, d m It is the hydraulic diameter of the main channel section with equal cross section.

[0019] Define the opening ratio of the regulating orifice plate k = A o / A m

[0020] In the formula, A o A is the total opening area of ​​the orifice plate. For expansion hole adjustment orifice plates, it is calculated based on the small end of the hole. m is the cross-sectional area of ​​the main channel with equal cross-sectional area.

[0021] Define the opening taper of the expansion hole adjustment orifice plate c = (d o2 -d o1 ) / t

[0022] Where, d o2 is the hydraulic diameter of the large end of the single hole of the expansion hole regulating orifice plate, and t is the thickness of the regulating orifice plate.

[0023] Under the premise of ensuring sufficient strength, adjust the relative aperture of the orifice plate It can be 0.03-0.15, the opening ratio k can be 0.2-0.7, and the opening taper c can be 0-0.4.

[0024] Now combined Figure 6(a) to Figure 6(b), the double-sided blowing test section scheme is further explained. The assembly process is shown in Figure 6 (a). The main channel of the double-sided blowing test section is connected to the main flow measurement section. An infrared window is opened on the wall above it. After the infrared glass is installed, it is fixed by a flange cover. A double-sided blowing test piece mounting hole is set in the middle position of the side of the main flow channel. The mounting hole has the same shape as the cross-section of the test piece, and sufficient assembly clearance is guaranteed. Several thermocouple mounting grooves are set on the measured surface of the double-sided blowing test piece, and calibration thermocouples are buried to correct the infrared measurement results. Before installing the test piece, first insert the lead of the calibration thermocouple into the double-sided blowing test piece mounting hole on the side and lead it out from the flow channel outlet. Then push the double-sided blowing test piece from the double-sided blowing test piece mounting hole into the main flow channel of the double-sided blowing test section and fix it on the pipeline through the flange structure so that the upper and lower sides of the test piece are in contact with the main flow. Then the secondary flow channel of the test piece is connected to the secondary flow measurement section through the flange structure. After the pipeline is assembled, the infrared thermal imager is fixed above the test area to measure the surface temperature field of the test piece. The assembled test section is shown in Figure 6(b).

[0025] Now combined Figure 7(a) to Figure 7(d) , the structure and working principle of the secondary flow temperature regulation system are further explained. As shown in Figure 7(a), the spiral heat exchange tube has a spiral coil in the middle, which is the main part for heat exchange with the mainstream, and straight pipes extend from both ends to connect with the front and rear metal hoses. The length of the spiral section of the heat exchange tube is l s and the outer diameter of the heat exchange tube spiral d s Slightly smaller than the main channel width w m and main channel height h m , to ensure that the middle spiral section of the pipe can be completely covered by the mainstream exhaust range. Furthermore, l s / w m and d s / h m The preferred value is within the range of 0.80 to 0.95.

[0026] Temperature regulation process Figure 7(b) and 7(c) As shown in the figure, the spiral heat exchange tube is placed downstream of the main channel outlet of the double-sided blowing test section, and the distance s between the heat exchange tube and the main channel outlet is kept at an appropriate value, which can prevent the flow in the main channel from being blocked due to being too close, and avoid the heat transfer effect from being reduced due to being too far. m The range of 0.3 to 2.0 has a relatively ideal effect. The two ends of the spiral heat exchange tube are fixed on the displacement mechanism through the pipe clamping device, and the position is adjusted as the displacement mechanism slide moves up and down, thereby changing the depth of the heat exchange tube intruding into the mainstream exhaust gas, and using the changed heated area of ​​the spiral heat exchange tube to change the heating power and secondary flow temperature. The secondary flow inlet temperature T of the experimental section c1The curve of the change of the depth h of the heat exchange tube inserted into the mainstream is shown in Figure 7(d). When the spiral heat exchange tube is completely outside the mainstream exhaust range, that is, the depth h of the heat exchange tube inserted into the mainstream is 0, the secondary flow is not heated by the mainstream, T c1 is the minimum value, which is approximately the atmospheric temperature. As the spiral heat exchange tube gradually penetrates into the mainstream, the heat exchange with it increases, causing the secondary flow temperature to gradually rise. s When the spiral section of the heat exchange tube is completely within the mainstream exhaust range, T c1 When the maximum value is reached and h continues to increase, the temperature stops increasing until h is equal to the main channel height h m After that, h continues to increase, and the spiral heat exchange tube gradually moves out of the mainstream exhaust range, T c1 It changes in a trend opposite to the curve in the figure.

[0027] Beneficial effects of the present invention:

[0028] 1. Make full use of the effect of turbojet engine, replace multiple heating and pressurizing equipment, simplify the experimental system and reduce the experimental cost;

[0029] Existing heat transfer experimental methods usually adopt separate solutions when facing the temperature and pressure requirements of the working fluid. First, the working fluid pressure is increased by a fan to generate flow, and then the working fluid temperature is increased by an electric heater. These two types of equipment are often characterized by high cost and large size. Especially for high-power electric heaters, large power supplies and power control equipment are usually required. The present invention uses a turbojet engine to supply air to the mainstream. Due to its large power density, it occupies a small space, and can simultaneously achieve pressurization and heating to meet the temperature and pressure requirements of the mainstream working fluid. A single device replaces the functions of the mainstream fan and the mainstream electric heater. In addition, the present invention also uses the waste heat of the mainstream exhaust to heat and adjust the temperature of the secondary flow, eliminating the secondary flow heating device and its energy input. Therefore, compared with the background experimental scheme, the experimental system of the present invention reduces the length of the experimental bench pipeline and the floor area by more than 40% under the premise of achieving the same working conditions, simplifies the experimental system, and reduces the experimental cost.

[0030] 2. Using the gas generated by the turbojet engine as the mainstream working fluid, its composition is closer to the working environment of the real engine parts, and the experimental results are more credible;

[0031] The experimental system of the present invention adopts high-temperature combustion gas generated by the combustion of a turbojet engine as the mainstream working fluid. Compared with the air working fluid heated by an electric heater in the background scheme, it is closer to the actual working environment of engine parts, reduces the experimental error caused by the difference in the physical properties of the working fluid, and increases the credibility of the experimental results.

[0032] 3. Directly use high-temperature fuel gas as the mainstream working fluid, with high energy conversion efficiency, and use the waste heat of mainstream exhaust to heat the secondary flow, reducing energy consumption;

[0033] The electric heater in the background scheme first needs to extract electricity from the power grid, then convert the electricity into heat energy, and then transfer the heat energy to the gas working fluid flowing through. This process will be accompanied by a certain amount of energy loss. If the electricity comes from thermal power generation that burns fuel, the thermal efficiency finally transferred to the experimental working fluid is usually only less than 60%, and the fuel is not fully utilized. The experimental system of the present invention uses the high-temperature gas directly burned by the turbojet engine as the mainstream working fluid. All the heat generated by the fuel can be absorbed by the working fluid to produce a heating effect. The conversion efficiency is close to 100%. Compared with the electric heater method, the energy conversion is more direct and the utilization rate is higher. In addition, the present invention uses the secondary flow temperature regulation system to heat the secondary flow using the mainstream waste heat discharged from the experimental section, thereby realizing the secondary utilization of energy, eliminating the energy input for heating the secondary flow, and improving the total energy utilization rate. Compared with the background heat transfer experimental scheme, the experimental system of the present invention reduces energy consumption by about 30% under the premise of achieving the same working conditions.

[0034] 4. The secondary flow temperature regulation system has a simple structure, a large adjustment range and high safety;

[0035] The secondary flow temperature regulation system of the present invention changes the heating power of the mainstream exhaust gas to the secondary flow by controlling the depth of the spiral heat exchange tube intruding into the mainstream exhaust gas, thereby converting the temperature change of the secondary flow into the change of the depth of the heat exchange tube inserted into the mainstream. On this basis, the remote regulation function of the secondary flow temperature is flexibly and effectively realized through a displacement control device with a simple structure. In addition, the present invention adopts a spiral heat exchange tube with high heat exchange efficiency, and fully considers and designs the length of its spiral section, the outer diameter of the spiral and the distance from the outlet of the mainstream channel, so that the secondary flow and the mainstream have a good heat exchange effect, so the scheme has a large temperature regulation range. From the perspective of safety, the spiral heat exchange tube in the present invention is located outside the outlet of the mainstream channel, and a reasonable range is set for the distance between the heat exchange tube and the outlet of the mainstream channel, ensuring that the heat exchange tube will not interfere with the mainstream in the pipeline and affect the safe operation of the turbojet engine. In addition, through the secondary flow temperature regulation system of the present invention, the working fluids of the two flow paths only exchange heat, and there is no need to transfer the heat of the mainstream to the secondary flow by transferring mass, which not only avoids complex pipeline design, but also prevents certain dangers when drawing out high-temperature gas. At the same time, the present invention adjusts the secondary flow temperature through remote control, which has higher safety for experimental operators.

[0036] 5. The combined structural design of the transfer pipe and the regulating orifice plate flexibly and effectively achieves the matching of engine performance with various experimental conditions;

[0037] The experimental scheme of the present invention adopts a turbojet engine as the gas source and heat source of the mainstream path, and the primary problem faced is the matching of the experimental working conditions with the engine performance. Based on the principle of fluid mechanics, the connection between the engine operating characteristics and various experimental working conditions is fully considered, and a combined structural scheme of a transfer pipe and an adjusting orifice plate is proposed to solve it. When a low-speed and normal-pressure mainstream working condition is required, an expansion transfer pipe and an adjusting orifice plate are used after the engine outlet, and the flow rate and pressure in the mainstream pipeline of the experimental section are adjusted to the required low-speed and normal-pressure level under the premise of ensuring that the overall pressure drop value is the same as that of the original tail nozzle; when the required mainstream working condition becomes low-speed and high-pressure, the installation position of the adjusting orifice plate can be moved back to the outlet of the mainstream channel of the experimental section on the basis of the above scheme, and the mainstream working condition of the experimental section is adjusted to a low-speed and high-pressure level under the premise that the overall pressure drop value of the mainstream pipeline remains unchanged; when a high-speed and normal-pressure mainstream working condition is required, a contraction transfer pipe is used after the engine outlet to reduce the pressure and increase the speed of the mainstream working fluid, and provide the required high-speed and normal-pressure mainstream working condition for the experimental section under the condition that the overall pressure drop of the mainstream pipeline remains unchanged. By changing the structure of the transition section and the installation position and combination of the regulating orifice plate, the flexible adjustment of parameters such as pressure and flow rate of the mainstream working fluid can be achieved simply and effectively. At the same time, it can ensure that the turbojet engine can operate safely and stably under different experimental conditions, thereby expanding the scope of application of the experimental conditions.

[0038] 6. The experimental system has wide applicability;

[0039] The experimental system described in the present invention is suitable for heat transfer characteristic experiments of dual flow paths with two hot and cold fluids, including but not limited to heat transfer characteristic experiments of double-sided blowing experimental pieces, which can be applicable to turbine blades or support plate parts; single-sided blowing experimental pieces heat transfer characteristic experiments, which can be applicable to combustion chambers and nozzle barrel walls; heat exchanger experiments, which are applicable to air system regulation parts, etc. In addition, the experimental system of the present invention can flexibly adjust parameters such as temperature, flow rate and pressure of the mainstream and secondary flows to achieve a wider range of working conditions, and the device has a simple structure, flexible and ingenious design, low experimental cost, low energy consumption, and good universality for various heat transfer characteristic experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the dual-flow path heat transfer characteristics experimental setup in the background.

[0041] Figure 2 Schematic diagram of the low-energy dual-flow path wide working condition heat transfer characteristics experimental device.

[0042] Figure 3 Schematic diagram of measurement and control system line connections.

[0043] Figure 4 (a) Schematic diagram of the turbojet engine and tail nozzle assembly.

[0044] Figure 4(b) Schematic diagram of the turbojet engine and subsequent pipeline assembly under low-speed, normal-pressure mainstream conditions.

[0045] Figure 4(c) is a graph showing the pressure variation in the mainstream pipeline under low-speed and normal-pressure mainstream conditions.

[0046] Figure 5 (a) Schematic diagram of the structure of the straight hole adjustment orifice plate and the expansion hole adjustment orifice plate.

[0047] Fig. 5(b) Assembly diagram of the double-layer regulating orifice plate.

[0048] Fig. 6(a) Schematic diagram of the experimental section assembly for the heat transfer characteristics experiment of the double-sided blowing test piece.

[0049] Fig. 6(b) Experimental section of the heat transfer characteristics experiment of the double-sided blowing test piece.

[0050] Figure 7(a) Schematic diagram of the spiral heat exchange tube structure.

[0051] Fig. 7(b) Assembly diagram of the secondary flow temperature regulation system.

[0052] Fig. 7(c) Schematic diagram of the secondary flow temperature adjustment process.

[0053] Figure 7 (d) Secondary flow inlet temperature T of the experimental section c1 Curve diagram of changes with insertion mainstream depth h.

[0054] Figure 8 Characteristic curve of the relationship between exhaust temperature and speed of a certain type of turbojet engine.

[0055] Fig. 9 Variation trend of the experimental specimen wall cooling efficiency η with flow ratio ζ and temperature ratio κ.

[0056] Fig.10 Schematic diagram of the heat transfer characteristics experiment of the single-sided blowing test piece.

[0057] Fig.11 Schematic diagram of the heat transfer characteristics experiment of the heat exchanger.

[0058] Fig. 12(a) Schematic diagram of the turbojet engine and subsequent pipeline assembly under low-speed and high-pressure mainstream conditions.

[0059] Figure 12(b) is a graph showing the pressure variation in the mainstream pipeline under low-speed and high-pressure mainstream conditions.

[0060] Fig. 13(a) Schematic diagram of the turbojet engine and subsequent pipeline assembly under high-speed, normal-pressure mainstream conditions.

[0061] Figure 13(b) is a graph showing the pressure variation in the mainstream pipeline under high-speed, normal-pressure mainstream conditions.

[0062] In the figure: 1. mainstream fan, 2. mainstream inlet section, 3. mainstream flow meter, 4. engine inlet adapter section, 5. turbojet engine, 6. mainstream electric heater, 7. oil pump, 8. fuel flow meter, 9. expansion engine outlet adapter section, 10. adjustment orifice plate, 10-1. straight hole adjustment orifice plate, 10-2. orifice plate spacing adjustment flange, 10-3. expansion hole adjustment orifice plate, 11. mainstream pressure stabilizing section, 12. mainstream measurement section, 13. mainstream pressure sensor, 14. mainstream thermocouple, 15. double-side blowing Main channel of the test section, 16. Secondary flow fan, 17. Secondary flow flow meter, 18. Secondary flow electric heater, 19. Metal hose, 20. Spiral heat exchange tube, 21. Pipe clamping device, 22. Displacement mechanism, 23. Secondary flow pressure stabilizing section, 24. Secondary flow measurement section, 25. Secondary flow pressure sensor, 26. Secondary flow thermocouple, 27. Double-side blowing test piece, 28. Thermal insulation layer, 29. Calibration thermocouple, 30. Original tail nozzle, 31. Main channel area, 32. Straight hole adjustment orifice plate single hole hydraulic diameter d o , 33. Hydraulic diameter d of the small end of the single hole of the expansion hole regulating orifice plate o1 , 34. Hydraulic diameter d of the large end of the single hole of the expansion hole regulating orifice plate o2 , 35. Adjustment orifice plate thickness t, 36. Infrared glass, 37. Flange cover, 38. Double-sided blowing test piece installation hole, 39. Infrared thermal imager, 40. Length of the spiral section of the heat exchange tube l s , 41. Heat exchange tube spiral outer diameter d s , 42. Main channel width w m , 43. Main channel height h m , 44. Distance s between the heat exchange tube and the main channel outlet, 45. Depth h of the heat exchange tube inserted into the main channel, 46. Main channel of the single-sided blowing test section, 47. Single-sided blowing test piece, 48. Main channel of the heat exchanger test section, 49. Heat exchanger, 50. Contraction type engine outlet transition section. DETAILED DESCRIPTION

[0063] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0064] A low-energy dual-flow wide-condition heat transfer characteristic experimental system consists of a pipeline system and a measurement and control system. The pipeline system includes two flow paths: the main flow and the secondary flow. Figure 2 As shown. Different from the background scheme using a fan and an electric heater, the main flow path of the present invention provides high-temperature and high-pressure gas working medium through a turbojet engine 5. After the turbojet engine 5 is ignited, air is sucked into the pipeline through the main flow inlet section 2, and its mass flow m is measured after flowing through the main flow flow meter 3. aThen, it passes through the engine inlet adapter section 4 and enters the turbojet engine 5. At the same time, the turbojet engine 5 sucks fuel from the fuel tank through the fuel pump 7, and its mass flow rate m is measured by the fuel flow meter 8. f . Subsequently, the turbojet engine 5 ejects high-temperature and high-pressure combustion gas as the mainstream working fluid into the expansion engine outlet transition section 9, where its pressure is increased and its flow rate is reduced by gradually expanding the cross-sectional area of ​​the pipeline along the way, and then it flows through the regulating orifice plate 10, where the pressure is reduced to about atmospheric pressure while maintaining the flow rate, and is rectified. Through the joint regulation of the above-mentioned transition pipeline and orifice plate structure, the mainstream meets the working conditions required for the experiment, and then the working fluid enters the mainstream pressure stabilizing section 11, and after stabilizing the flow, it enters the mainstream measuring section 12, where the mainstream pressure sensor 13 and the mainstream thermocouple 14 respectively measure the mainstream inlet pressure P of the experimental section. g1 and the mainstream inlet temperature T g1 , and then enters the main channel 15 of the double-side blowing test section, flows through both sides of the double-side blowing test piece 27, and finally is discharged from the test section pipeline outlet.

[0065] The secondary flow path sucks in air through the secondary flow fan 16 and increases its pressure, flows through the secondary flow flow meter 17 and measures its mass flow m c , and then enters the spiral heat exchange tube 20 through the metal hose 19. The spiral heat exchange tube 20 is placed downstream of the outlet of the main channel 15 of the double-sided blowing test section through the pipe clamping device 21 and the displacement mechanism 22, and is heated by the waste heat of the mainstream exhaust gas, and the depth of the spiral heat exchange tube 20 invading the mainstream exhaust gas is controlled by the displacement mechanism 22 to adjust the secondary flow temperature. After passing through the spiral heat exchange tube 20, the secondary flow medium flows into the secondary flow stabilizing section 23 through the metal hose 19, and enters the secondary flow measuring section 24 after stabilizing the flow, where the secondary flow inlet pressure P of the test section is measured by the secondary flow pressure sensor 25 and the secondary flow thermocouple 26 respectively. c1 and the secondary flow inlet temperature T c1 , and then enters the internal channel of the double-sided blowing test piece 27, exchanges heat with it and flows out from the outlet of the test piece, finally merges into the mainstream and is then discharged from the test section pipeline.

[0066] The pipelines after the main flow and the secondary flow are heated are covered with a thermal insulation layer 28 to reduce the heat loss of the experimental system and prevent the experimental personnel from being scalded by the high-temperature pipelines.

[0067] The circuit connection scheme of the measurement and control system of the present invention is as follows Figure 3 The main measurement scheme includes: using the mainstream flow meter 3, the fuel flow meter 8 and the secondary flow meter 17 to measure the mainstream intake air mass flow m a , Engine fuel mass flow m f And the secondary flow mass flow rate m c, where the mainstream inhaled air mass flow rate m a and engine fuel mass flow m f The sum is the mainstream working fluid mass flow rate m g The mainstream inlet pressure P of the experimental section is measured by the mainstream pressure sensor 13 and the secondary flow pressure sensor 25 respectively. g1 and the secondary flow inlet pressure P of the experimental section c1 ; The mainstream inlet temperature T of the experimental section was measured by the mainstream thermocouple 14 and the secondary flow thermocouple 25 respectively g1 and the secondary flow inlet temperature T c1 ; Install infrared glass 36 and infrared thermal imager 39 above the experimental piece to measure the average wall temperature T of the experimental piece w Several thermocouple installation slots are opened on the surface of the test piece to be tested, and calibration thermocouples 29 are embedded to obtain the wall surface temperature T with sufficient accuracy. wi , used as a reference benchmark for the correction of infrared measurement results. Among them, the flow meter, pressure sensor and thermocouple are connected to the data acquisition instrument through signal lines, the data acquisition instrument is connected to the computer for transmission, processing and storage of data, and the infrared thermal imager is directly connected to the computer to collect temperature field data. The main control scheme includes: controlling the speed of the secondary flow fan 16 through the fan speed governor to achieve the regulation of the secondary flow flow; the lines of the turbojet engine 5 and the oil pump 7 are connected to the engine control console to achieve remote control of the turbojet engine start and stop and the throttle; in addition, the position of the spiral heat exchange tube 20 is adjusted through the displacement mechanism console.

[0068] The pipeline system and the data acquisition and control system are kept at a sufficient safety distance in space, and effective safety protection measures are set for the turbojet engine 5 to ensure the safety of the experimental operators.

[0069] Now combined Figure 4a ~ Figure 4c , the mainstream pipeline design and connection scheme after the turbojet engine in the present invention are further explained. Figure 4a As shown in FIG. 1 , the original tail nozzle 30 of the turbojet engine 5 is a convergent nozzle, which is connected to the turbine outlet of the turbojet engine 5 and is used to convert the pressure energy of the fuel gas into kinetic energy, so that the nozzle outlet emits a high-speed, normal-pressure airflow, thereby providing sufficient thrust. When the turbojet engine is not connected to the mainstream pipeline, that is, when the turbojet engine is working alone, the pressure change in the original tail nozzle 30 along the flow direction is as follows: Figure 4c As shown by the dotted line in the figure, it gradually decreases to atmospheric pressure along the way and then is discharged into the atmosphere.

[0070] In the present invention, the original tail nozzle 30 is removed from the adopted turbojet engine 5, and a new pipeline expansion type engine outlet adapter section 9 to mainstream measurement section 12 are designed as a replacement according to the mainstream pressure and speed requirements in the experimental section. Figure 4bAs shown, the turbojet engine 5 is connected to an expansion engine outlet adapter section 9, whose inlet cross-section is the same as the original tail nozzle, which is a circular cross-section and is provided with a rectifying cone, connected to the turbine outlet of the engine; after a smooth transition, the outlet becomes a rectangular cross-section with a larger area than the inlet, forming an expansion pipeline as a whole. An adjusting orifice plate 10 is installed after the expansion engine outlet adapter section 9, and its function is to provide a suitable pressure drop for the pipeline system to match the engine operating characteristics and prevent the turbine from over-rotating, while also playing a rectifying role. When the required pressure drop of the pipeline is large, multiple layers of serial adjusting orifice plates can be set, typically such as a straight hole adjusting orifice plate 10-1 and an expansion hole adjusting orifice plate 10-3, and an orifice plate spacing adjusting flange 10-2 is installed between two adjacent orifice plates, and the orifice plate spacing and airflow pressure drop are adjusted by the thickness of the flange. Reference for pressure changes along the flow direction in the mainstream pipeline Figure 4c The solid line in the figure shows that when the mainstream working fluid flows through the expansion engine outlet adapter section 9, the kinetic energy of the working fluid is converted into pressure energy due to the gradual increase in the cross-sectional area, the flow rate decreases, and the pressure increases. Then, after passing through one or more layers of regulating orifice plates, the pressure quickly decreases to near atmospheric pressure, and then enters the mainstream pressure stabilization section to maintain a stable flow, providing the required low-speed and normal-pressure mainstream working conditions for the experimental section pipeline. This scheme increases the pressure in the mainstream pipeline first and then decreases it, and the overall pressure drop value is the same as that of the original tail nozzle, thereby replacing the original tail nozzle and ensuring the safe and stable operation of the turbojet engine under the required experimental working conditions.

[0071] Combination Figure 5a ~ Figure 5b , the structure of the regulating orifice plate 10 is further described. Figure 5a As shown, the regulating orifice plate 10 is a thin plate with multiple openings in the middle area, and the openings are evenly distributed in the main channel area 31. The hole shape can be circular, elliptical or rectangular, etc., and the opening cross section can be a straight hole structure with a constant along the flow direction. The typical structure is as follows Figure 5a The straight hole adjustment orifice plate 10-1 shown on the left side of the center line, or the expansion hole structure with gradually increasing cross-sectional area, the typical structure is as follows Figure 5a The expansion hole regulating orifice plate 10-3 shown on the right side of the center line. In order to ensure the pressure reduction effect, the openings of the two adjacent layers of orifice plates are arranged in a staggered manner to avoid forming a smooth air flow channel. The typical assembly scheme of the multi-layer orifice plate is as follows Figure 5b As shown, it is connected to the front and rear pipes through flanges, and a plate spacing adjustment flange 10-2 is installed between the two layers of orifice plates. Along the flow direction of the working medium, the hydraulic diameter of the openings of the multi-layer orifice plates gradually decreases, and the thickness of the orifice spacing adjustment flange 10-2 between the adjacent two layers of orifice plates gradually decreases, which can improve the pressure drop effect. Figure 4c As shown, for the expansion hole regulating orifice plate, since the flow area of ​​its opening gradually increases along the process, the working fluid pressure is restored to a certain extent after being drastically reduced, which has a better rectification effect and is beneficial to improving the uniformity of subsequent flow.

[0072] Define the relative aperture of the regulating orifice plate

[0073] For straight hole conditioning orifice plates,

[0074] For expansion hole adjustment orifice plate,

[0075] Where, d o The hydraulic diameter of a single hole of the straight hole regulating orifice plate is 32, d o1 The hydraulic diameter of the small end of the single hole of the expansion hole adjustment orifice plate is 33,d m It is the hydraulic diameter of the main channel section with equal cross section.

[0076] Define the opening ratio of the regulating orifice plate k = A o / A m 3

[0077] In the formula, A o A is the total opening area of ​​the orifice plate. For expansion hole adjustment orifice plates, it is calculated based on the small end of the hole. m is the cross-sectional area of ​​the main channel with equal cross-sectional area.

[0078] Define the opening taper of the expansion hole adjustment orifice plate c = (d o2 -d o1 ) / t 4

[0079] Where, d o2 is the hydraulic diameter of the large end of the single hole of the expansion hole regulating orifice plate 34, and t is the thickness of the regulating orifice plate 35.

[0080] Under the premise of ensuring sufficient strength, adjust the relative aperture of the orifice plate It can be 0.03-0.15, the opening ratio k can be 0.2-0.7, and the opening taper c can be 0-0.4.

[0081] Now combined Figure 6a ~ Figure 6b , the double-sided blowing test section scheme is further explained. The assembly process is as follows Figure 6aAs shown, the main channel 15 of the double-sided blowing test section is connected to the main flow measurement section 12, and an infrared window is opened on the wall above it. After the infrared glass 36 is installed, it is fixed by a flange cover 37. A double-sided blowing test piece mounting hole 38 is set in the middle position of the side of the main flow channel. The mounting hole has the same cross-sectional shape as the test piece, and sufficient assembly clearance is guaranteed. A number of thermocouple mounting grooves are set on the measured surface of the double-sided blowing test piece 27, and a calibration thermocouple 29 is buried to correct the infrared measurement results. Before installing the test piece, first insert the lead wire of the calibration thermocouple 29 into the double-sided blowing test piece mounting hole 38 on the side and lead it out from the flow channel outlet, then push the double-sided blowing test piece 27 from the double-sided blowing test piece mounting hole 38 into the main flow channel of the double-sided blowing test section, and fix it on the pipeline through the flange structure, so that the upper and lower sides of the test piece are in contact with the main flow, and then the secondary flow channel of the test piece is connected to the secondary flow measurement section 24 through the flange structure. After the pipeline is assembled, the infrared thermal imager 39 is fixed above the measured area to measure the surface temperature field of the test piece. Figure 6b shown.

[0082] Now combined Figure 7a ~ Figure 7d , the structure and working principle of the secondary flow temperature control system are further explained. Figure 7a As shown, the spiral heat exchange tube 20 has a spiral coil in the middle, which is the main part for heat exchange with the mainstream, and straight pipes extend from both ends to connect with the front and rear metal hoses 19. s 40 and the outer diameter of the heat exchange tube spiral d s 41 are slightly smaller than the main channel width w m 42 and main channel height h m 43, to ensure that the middle spiral section of the pipe can be completely covered by the mainstream exhaust range. s / w m and d s / h m The preferred value is within the range of 0.80 to 0.95.

[0083] Temperature regulation process Figure 7b As shown in FIG. 7c, the spiral heat exchange tube 20 is placed downstream of the outlet of the main channel 15 of the double-sided blowing test section, and the distance s44 between the heat exchange tube and the outlet of the main channel is kept at an appropriate value, which can prevent the flow in the main channel from being blocked due to being too close, and avoid the heat exchange effect from being reduced due to being too far. mThe range of 0.3 to 2.0 has a relatively ideal effect. The two ends of the spiral heat exchange tube 20 are fixed on the displacement mechanism 22 by the pipe clamping device 21, and the position is adjusted as the displacement mechanism slide moves up and down, thereby changing the depth of the heat exchange tube intruding into the mainstream exhaust gas, and using the changed heated area of ​​the spiral heat exchange tube 20, the heating power and secondary flow temperature are changed. The secondary flow inlet temperature T of the experimental section c1 The curve of the change of the heat exchange tube insertion depth h45 is as follows Figure 7d As shown in the figure, when the spiral heat exchange tube 20 is completely outside the mainstream exhaust range, that is, the heat exchange tube is inserted into the mainstream depth h45 is 0, the secondary flow is not heated by the mainstream, T c1 is the minimum value, which is approximately the atmospheric temperature. As the spiral heat exchange tube 20 gradually penetrates into the mainstream, the heat exchange with it increases, causing the secondary flow temperature to gradually rise. s At 41, the spiral sections of the heat exchange tubes are all within the mainstream exhaust range, T c1 When the maximum value is reached and h continues to increase, the temperature stops increasing until h is equal to the main channel height h m 43. After that, h continues to increase, and the spiral heat exchange tube 20 gradually moves out of the mainstream exhaust range, T c1 It changes in a trend opposite to the curve in the figure.

Claims

1. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system, characterized in that: The invention comprises a pipeline system and a measurement and control system, wherein the pipeline system comprises a main flow path and a secondary flow path, wherein the main flow path provides a high-temperature and high-pressure gas working medium through a turbojet engine (5); after the turbojet engine (5) is ignited, air is sucked into the pipeline through a main flow inlet section (2), and after flowing through a main flow flow meter (3), its mass flow m is measured. a , and then enters the turbojet engine (5) through the engine inlet adapter section (4); at the same time, the turbojet engine (5) sucks fuel from the fuel tank through the fuel pump (7), and its mass flow rate m is measured by the fuel flow meter (8) f Subsequently, the turbojet engine (5) ejects high-temperature and high-pressure combustion gas, which enters the expansion engine outlet transfer section (9) as the mainstream working medium, and then flows through the regulating orifice plate (10). After the joint regulation of the above-mentioned transfer pipeline and orifice plate structure, the mainstream reaches the working condition required for the experiment. Subsequently, the working medium enters the mainstream pressure stabilizing section (11), and after the stabilization flow, enters the mainstream measuring section (12), where the mainstream pressure sensor (13) and the mainstream thermocouple (14) respectively measure the mainstream inlet pressure P of the experimental section. g1 and the mainstream inlet temperature T g1 , then enters the main channel (15) of the double-sided blowing test section, flows through both sides of the double-sided blowing test piece (27), and finally is discharged from the test section pipeline outlet; The secondary flow path sucks in air working medium through the secondary flow fan (16) and increases its pressure, and flows through the secondary flow flow meter (17) to measure its mass flow rate m c , and then enters the spiral heat exchange tube (20) through the metal hose (19); the spiral heat exchange tube (20) is placed downstream of the outlet of the main channel (15) of the double-sided blowing test section through the pipe clamping device (21) and the displacement mechanism (22), and is heated by the waste heat of the main exhaust gas, and the depth of the spiral heat exchange tube (20) invading the main exhaust gas is controlled by the displacement mechanism (22) to adjust the secondary flow temperature; after passing through the spiral heat exchange tube (20), the secondary flow medium flows from the metal hose (19) into the secondary flow stabilizing section (23), and after stabilizing the flow, enters the secondary flow measuring section (24), and the secondary flow inlet pressure P of the test section is measured by the secondary flow pressure sensor (25) and the secondary flow thermocouple (26) respectively. c1 and the secondary flow inlet temperature T c1 , and then enters the internal channel of the double-sided blowing test piece (27), exchanges heat with it and flows out from the outlet of the test piece, finally merges into the mainstream and is then discharged from the test section pipeline.

2. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system as claimed in claim 1, characterized in that: The measurement and control system comprises a mainstream flow meter (3), a fuel flow meter (8) and a secondary flow meter (17); the mainstream flow meter (3), the fuel flow meter (8) and the secondary flow meter (17) are used to respectively measure the mainstream intake air mass flow m a , Engine fuel mass flow m f And the secondary flow mass flow rate m c The mainstream inlet pressure P of the experimental section is measured by the mainstream pressure sensor (13) and the secondary flow pressure sensor (25). g1 and the secondary flow inlet pressure P of the experimental section c1 The mainstream inlet temperature T of the experimental section is measured by the mainstream thermocouple (14) and the secondary flow thermocouple (25). g1 and the secondary flow inlet temperature T c1 ; Install infrared glass (36) and infrared thermal imager (39) above the experimental piece to measure the average wall temperature T of the experimental piece w A number of thermocouple mounting slots are opened on the surface of the experimental piece to be tested, and calibration thermocouples (29) are embedded to obtain the wall surface temperature T wi , used as a reference benchmark to correct infrared measurement results.

3. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system as claimed in claim 1, characterized in that: The turbojet engine (5) is connected to an expansion engine outlet adapter section (9) at the rear, and its inlet cross section is a circular cross section and is provided with a rectifying cone, and is connected to the turbine outlet of the engine; after a smooth transition, the outlet becomes a rectangular cross section with a larger area than the inlet, and an expansion pipeline is formed as a whole; an adjustment orifice plate (10) is installed at the rear of the expansion engine outlet adapter section (9), and the adjustment orifice plate (10) includes a straight hole adjustment orifice plate (10-1) and an expansion hole adjustment orifice plate (10-3).

4. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system as claimed in claim 3, characterized in that: The regulating orifice plate (10) is a thin plate with a plurality of openings in the middle region, wherein the openings are evenly and densely distributed in the main channel region (31), and the hole shape is circular, elliptical or rectangular, and has a straight hole structure with a constant opening cross section along the flow direction, i.e., a straight hole regulating orifice plate (10-1); or an expanded hole structure with a gradually increasing cross-sectional area, i.e., an expanded hole regulating orifice plate (10-3).

5. A low-energy consumption dual-flow-path wide working condition heat transfer characteristic experimental system as claimed in claim 4, characterized in that: The relative aperture of the regulating orifice plate (10) For the straight hole adjustment orifice plate (10-1), For the expansion hole adjustment orifice plate (10-3), Where, d o is the hydraulic diameter of a single hole of the straight hole regulating orifice plate (32), d o1 is the hydraulic diameter of the small end of the expansion hole adjusting orifice plate (33), d m is the hydraulic diameter of the section of equal cross section of the main channel; The opening ratio of the regulating orifice plate (10) is k=A o / A m (3) In the formula, A o A is the total opening area of ​​the orifice plate. For the expansion hole adjustment orifice plate, it is calculated based on the small end of the hole; m is the cross-sectional area of ​​the main channel with equal cross-sectional area; The opening taper c of the expansion hole regulating orifice plate (10-3) is (d o2 -d o1 ) / t(4) Where, d o2 is the hydraulic diameter (34) of the large end of the expansion hole regulating orifice plate, and t is the thickness (35) of the regulating orifice plate.

6. A low-energy consumption dual-flow-path wide working condition heat transfer characteristic experimental system as claimed in claim 5, characterized in that: The relative aperture of the regulating orifice plate (10) It is 0.03~0.15, the opening rate k is 0.2~0.7, and the opening taper c is 0~0.

4.

7. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system as claimed in claim 1, characterized in that: The spiral heat exchange tube (20) has a spiral coil in the middle, and straight pipes extend from both ends to connect with the front and rear metal hoses (19); the length of the spiral section of the heat exchange tube is l s (40) and the outer diameter of the heat exchange tube spiral d s (41) are respectively smaller than the main channel width w m (42) and main channel height h m (43).

8. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system as claimed in claim 7, characterized in that: The said s / w m and d s / h m The range is 0.80~0.

95.

9. A low energy consumption dual flow path wide working condition heat transfer characteristic experimental system as claimed in claim 4, characterized in that: The openings of the regulating orifice plates (10) of two adjacent layers are arranged in a staggered manner, and an orifice plate spacing regulating flange (10-2) is installed between the two adjacent orifice plates. The orifice plate spacing and airflow pressure drop are regulated by the thickness of the flange.

10. The low energy consumption dual flow path wide working condition heat transfer characteristic experimental system according to claim 1, characterized in that: The heated pipes of the main flow path and the secondary flow path are coated with a thermal insulation layer (28).

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