Gas film hole and test system for inhibiting gas turbine resonance-induced flow coefficient pulsation

Abstract

The present application relates to the technical field of heating, heat insulation, cooling or vibration prevention device of blade or element, and discloses a gas film hole and a test system for inhibiting resonance-induced flow coefficient pulsation of a gas turbine, wherein the gas film hole structure can effectively weaken the non-dissipative space structure formed by resonance near the hole, so as to restore the sensitivity of the upstream pressure to the flow, inhibit the dramatic fluctuation of the outflow coefficient of the gas film hole, finally reduce the negative influence on the gas film cooling efficiency, and guarantee the stable cooling effect of the hot end part of the gas turbine; the test system can generate the pulse jet flow required for detecting the fluid flow characteristics of the gas film hole under pulse flow, the frequency, amplitude, waveform and duty cycle of the pulse flow can be adjusted, and the pulse jet flow is injected into the steady fluid along the hole plate which can be disassembled at any time, so that the performance of different gas film holes can be judged through the test without preparing an actual gas turbine, and a basis is provided for design.

Description

Technical Field

[0001] This invention relates to the field of heating, insulation, cooling or vibration prevention devices for blades or components, and in particular to a film pore and testing system for suppressing flow coefficient pulsations caused by gas turbine resonance. Background Technology

[0002] In the field of high-end power equipment such as aero-engines and gas turbines, increasing the turbine inlet temperature is a core technological path to overcome the bottleneck of cycle thermal efficiency and increase the overall power output of the turbine. Currently, the turbine inlet temperature of advanced gas turbines has exceeded 1600℃, far exceeding the tolerance limit of turbine blade materials. This extreme high-temperature environment exposes turbine blades to multiple failure risks, including high-temperature oxidation, thermal corrosion, and thermal fatigue. Therefore, it is urgent to develop efficient and stable advanced cooling technologies to prevent blade overheating.

[0003] In turbine blade cooling technology, film cooling (FSU) exhibits irreplaceable advantages due to its unique working principle: by injecting low-temperature cooling gas into the blade wall through pre-designed cooling channels, a continuous and dense "film barrier" is formed on the blade surface. This barrier not only physically blocks direct heat exchange between the high-temperature combustion gases and the blade wall, but also further removes heat from the wall through convective heat transfer of the cooling gas, thereby achieving efficient and uniform temperature control of the blade. Currently, FSU has become a core cooling technology for turbine blades in advanced aero-engines and heavy-duty gas turbines.

[0004] In actual operation, the dynamic operating conditions of a gas turbine can induce system resonance. On the one hand, resonance causes periodic vibrations in the cooling channels, leading to pressure and flow pulsations in the cooling gas. More importantly, these periodic fluctuations induce non-dissipative spatial structures (vortex systems or standing wave structures induced by resonance, characterized by low energy dissipation and strong spatiotemporal stability) in the cooling channels and outlet flow field. These structures, with their low energy dissipation and strong spatiotemporal stability, continuously interfere with the flow pattern of the cooling gas. They alter the velocity distribution of the cooling gas within the channels, causing localized flow accumulation or deficits, and create irregular flow interference at the interface between the cooling hole outlet and the mainstream gas flow, disrupting the uniformity of the jet flow. This flow pattern distortion caused by non-dissipative spatial structures directly leads to fluctuations in the flow coefficient, which in turn causes periodic fluctuations in the temperature field of turbine components, exacerbating alternating thermal stress and accelerating thermal fatigue damage to the components.

[0005] Current research indicates that the flow coefficient in pulsed flow is influenced by various factors, including pulse frequency, amplitude, waveform (square wave, sine wave, sawtooth wave, etc.), duty cycle (the percentage of time a valve is open within a cycle), average velocity, and system pressure. While average velocity and system pressure can be easily adjusted by changing the gas source, adjusting frequency, amplitude, waveform, and duty cycle is more difficult. If a plunger pump is used to directly generate pulsed flow, the waveform and duty cycle are completely unadjustable; amplitude can only be adjusted in absolute terms, not relative terms; and frequency has a definite upper limit. Other pulsed flow generation methods generally suffer from similar problems. Each method can only generate a specific type of pulsed flow with limited parameter adjustments. This significantly restricts research on pulsed flow, requiring the development of one or more dedicated pulse generators for each type of pulsed flow, severely hindering research efficiency.

[0006] To date, there is a lack of both film pores capable of overcoming the various adverse effects of pulsed flow and experimental systems for conducting hydrodynamic tests on film pores under pulsed flow. Summary of the Invention

[0007] This invention provides a film pore and testing system for suppressing flow coefficient pulsation caused by gas turbine resonance.

[0008] The technical problem to be solved is that there is currently no suitable film pore for overcoming the various adverse effects of pulsed flow, nor is there a suitable experimental system for conducting hydrodynamic tests on film pores under pulsed flow.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a film gas vent that suppresses flow coefficient pulsation caused by gas turbine resonance is composed of three integral and coaxially arranged cylindrical segments, namely an initial segment with diameter D1, an expansion segment with diameter D2, and a contraction segment with diameter D3, where D2 > D3 > D1; the initial segment is connected to the cold side; the expansion segment is abruptly connected to the initial segment, and the contraction segment is abruptly connected to the expansion segment and is connected to the hot side. Through the connection method and size ratio design of the three-segment cylindrical structure, an inner groove structure is formed inside the film gas vent.

[0010] Furthermore, D1≤2mm, 1.05≤D2 / D1≤1.5, 1.0<D3 / D1≤1.1.

[0011] Furthermore, the ratio of the length Le of the expansion section to the total length L of the air film pore is: 0.25≤Le / L≤0.75; L≥5mm.

[0012] Furthermore, the geometric center of the expansion section coincides with the geometric center of the entire film pore.

[0013] A test system for measuring the flow characteristics of film gas orifices under pulsed flow, used for the above-mentioned hydrodynamic test of film gas orifices to suppress flow coefficient pulsation caused by gas turbine resonance, includes a hot-side simulation section and a cold-side simulation section, wherein the film gas orifices are formed in an orifice plate, the orifice plate is detachably clamped between the hot-side simulation section and the cold-side simulation section, and allows the airflow in the secondary flow chamber to enter the main flow chamber along the film gas orifices; The hot-side simulation section includes a high-flow-rate gas source system and a main flow chamber located at the outlet of the high-flow-rate gas source system and used to provide airflow to simulate the hot side of the gas turbine. The cold-side simulation section includes a pressure-stabilized gas source system, a pulse flow generator for rectifying the steady-state airflow provided by the pressure-stabilized gas source system into the required pulse flow, and a secondary flow chamber located at the outlet of the pulse flow generator and used to provide airflow simulating the cold side of the gas turbine.

[0014] Furthermore, the main flow chamber is a square tube with a panel hole for embedding a perforated plate at the bottom side, and the secondary flow chamber is a square tube with a panel hole for embedding a perforated plate at the top side. The bottom of the main flow chamber and the top of the secondary flow chamber are attached together. The upper and lower edges of the perforated plate are engaged with the edges of the panel holes in the main flow chamber and the secondary flow chamber respectively through a stop. The engaging surfaces are coated with vacuum sealing mud for sealing. The upper surface of the orifice plate is flush with the upper surface of the bottom plate of the main flow chamber. The bottom plate of the main flow chamber and the top plate of the secondary flow chamber are respectively provided with multiple corresponding upper and lower ear plates. The ear plates are arranged around the perforated plate. The main flow chamber and the secondary flow chamber are tightly fitted together by bolts passing through the ear plates. During the experiment, the airflow from the high-flow-rate air source system enters the main flow chamber from one end of the main flow chamber, constructs a uniform steady-state flow field in the main flow chamber, and leaves from the other end of the main flow chamber; the secondary flow chamber is open at one end and sealed at the other end, and the pulsed nitrogen flow from the pulse flow generator enters the secondary flow chamber along the open end of the secondary flow chamber and is injected into the main flow chamber through the air film hole.

[0015] Furthermore, the high-flow-rate air source system includes a variable frequency fan, a vibration damping joint connected to the outlet of the variable frequency fan, and a honeycomb tube flow equalizer connected to the outlet of the vibration damping joint and used to eliminate eddies in the air entering the main flow chamber. The shock-absorbing joint is a shock-absorbing throat, and the honeycomb tube flow equalizer is a variable diameter tube with a cross-section in the middle section larger than that at both ends. The variable diameter tube is provided with a honeycomb core facing the same direction as the variable diameter tube.

[0016] Furthermore, the pressure-stabilized gas source system includes a nitrogen cylinder with a pressure-reducing valve, and the outlet pipeline of the pressure-reducing valve is fed into the pulse flow generator after passing through a pressure proportional valve and a buffer tank.

[0017] Furthermore, the pulse current generator includes a stepper reciprocating motor fixed on the base and electrically connected to the frequency converter, a piston cylinder with two open ends detachably fixed on the base, and a perforated piston that is driven by the stepper reciprocating motor to reciprocate in the piston cylinder with two open ends. The end of the perforated piston is detachably connected to the crank connecting rod of the stepper reciprocating motor. When the perforated piston moves in the piston cylinder with two open ends, the position when it is pulled out to the limit is recorded as the initial position of the piston. The stroke of the stepper reciprocating motor is adjustable; The piston cylinder with open ends has two aligned cylinder wall holes on its side wall. A rectifier tube connector is screwed into the two cylinder wall holes. The two rectifier tube connectors are of the same specification and their central axes are collinear. The central axis of the rectifier tube connector is perpendicular to and intersects the central axis of the piston cylinder with open ends. The punched piston has at least one piston hole, which is a through hole perpendicular to the punched piston. The geometric center line of the piston hole is perpendicular to and intersects the central axis of the punched piston. The rectifier tube connector has a constant diameter DC channel inside, which is called the outer channel. The channel in the piston hole is called the inner channel. During the reciprocating motion of the punching piston, the outer channel is intermittently connected to each inner channel.

[0018] Furthermore, the pulse flow generator and the secondary flow chamber are connected by a constant-diameter pipe without any diameter changes, valves, or sudden contractions or expansions, and there are no structures inside the pipe that would cause boundary layer detachment.

[0019] Compared with existing technologies, the film pore and testing system of this invention for suppressing flow coefficient pulsations caused by gas turbine resonance have the following advantages: The film cooling hole structure of the present invention can effectively weaken the non-dissipative space structure formed near the hole by resonance, thereby restoring the sensitivity of upstream pressure to flow rate, suppressing the violent fluctuation of the film cooling hole outflow coefficient, and ultimately reducing the negative impact on film cooling efficiency, ensuring the stable cooling effect of hot end components of gas turbine. The test system in this invention can generate a pulse jet required for detecting the fluid flow characteristics of film gas pores under pulsed flow. The frequency, amplitude, waveform, and duty cycle of the pulse jet can be adjusted. The pulse jet is injected into the steady fluid along a removable orifice plate. Thus, the performance of different film gas pores can be judged by test without the need to build an actual gas turbine, providing a basis for design. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the gas film orifice structure for suppressing flow coefficient pulsation caused by gas turbine resonance in this invention; Figure 2 This is a schematic diagram showing the pulsation of the flow coefficient of the air film orifice in this invention and a conventional cylindrical air film orifice under the same conditions. Figure 3The velocity contour plots of the air film orifice in this invention and a conventional cylindrical air film orifice under the same conditions at the peak flow rate in the region near the orifice. Figure 4 The pressure cloud map shows the peak flow rate in the vicinity of the air film orifice in this invention and a conventional cylindrical air film orifice under the same conditions. Figure 5 This is a schematic diagram of the streamlines of the air film pore in this invention and a conventional cylindrical air film pore under the same conditions; Figure 6 This is a schematic diagram of the structure of a test system for measuring the flow characteristics of a film gas pore under pulsed flow, according to the present invention. Figure 7 A three-dimensional view of the main chamber; Figure 8 This is a three-dimensional view of the secondary flow chamber; Figure 9 This is a schematic diagram of the pulse flow generator in this invention; Figure 10 An exploded view of the structure of the perforated piston and the piston cylinder with openings at both ends; Figure 11 The figures show waveforms of pulse streams generated using the adjustable frequency, amplitude, waveform, and duty cycle pulse stream generator of this invention. In the figures, T represents the pulse period (the reciprocal of the frequency), and P... avg The average static pressure of the pulsed flow; In the diagram, 1-orifice plate, 11-initial section, 12-expansion section, 13-contraction section, 2-secondary flow chamber, 21-insertion plate hole, 22-ear plate, 3-main flow chamber, 31-honeycomb tube flow equalizer, 4-thermal mass flow meter, 5-variable frequency fan, 51-vibration damping joint, 6-pulse flow generator, 61-stepper reciprocating motor, 62-piston cylinder with open ends, 621-limiting pin hole, 622-cylinder wall hole, 63-perforated piston, 631-piston hole, 632-piston ring groove, 633-limiting slide groove, 64-rectifier tube joint, 65-anti-rotation pin, 66-three-way valve, 7-secondary flow valve, 8-nitrogen cylinder, 81-pressure proportional valve, 82-buffer tank. Detailed Implementation

[0021] like Figure 1 As shown, the film gas vent that suppresses flow coefficient pulsation caused by gas turbine resonance consists of three interconnected and coaxially arranged cylindrical sections: an initial section 11 with a diameter of D1, an expansion section 12 with a diameter of D2, and a contraction section 13 with a diameter of D3, where D2 > D3 > D1. The initial section 11 is connected to the cold side; the expansion section 12 is abruptly connected to the initial section 11, and the contraction section 13 is abruptly connected to the expansion section 12 and is connected to the hot side. Through the connection method and size ratio design of the three-section cylindrical structure, an inner groove structure is formed inside the film gas vent.

[0022] In this structure, the appropriate range of parameter values ​​is as follows: D1≤2mm, 1.05≤D2 / D1≤1.5, 1.0<D3 / D1≤1.1.

[0023] The ratio of the length Le of the expansion section 12 to the total length L of the air film pore is: 0.25≤Le / L≤0.75; L≥5mm.

[0024] Within this range, the pulse amplitude can be effectively reduced.

[0025] Furthermore, the initial section 11, the expansion section 12, and the contraction section 13 are arranged coaxially, and the geometric center of the expansion section 12 coincides with the geometric center of the entire film pore, thereby ensuring that no meaningless pressure loss is generated.

[0026] like Figure 2-3 As shown, two specific embodiments are listed to illustrate the principle and effect of the air film pore in this invention: In Example I, the diameter D1 of the initial segment 11Ⅰ is 2 mm, the diameter ratio D2 / D1 of the expansion segment 12Ⅱ to the initial segment 11Ⅰ is 1.2, the diameter ratio D3 / D1 of the contraction segment 13Ⅲ to the initial segment 11Ⅰ is 1, the length ratio Le / L of the expansion segment 12Ⅱ to the total length of the air film pore is 0.6, and the total length L of the air film pore is 5 mm.

[0027] In Example II, the diameter D1 of the initial segment 11Ⅰ is 2 mm, the diameter ratio D2 / D1 of the expansion segment 12Ⅱ to the initial segment 11Ⅰ is 1.5, the diameter ratio D3 / D1 of the contraction segment 13Ⅲ to the initial segment 11Ⅰ is 1, the length ratio Le / L of the expansion segment 12Ⅱ to the total length of the air film pore is 0.6, and the total length L of the air film pore is 5 mm.

[0028] Under the same flow rate pulsation conditions, the pulsation of the outflow coefficient was simulated using both the film gas orifice from this embodiment and the classic cylindrical film gas orifice. The operating conditions were: main flow rate of 0.03 kg / s, a branch pipe in the upstream region, outlet flow rate controlled by a solenoid valve, and a sinusoidally time-varying flow rate (m = 0.01147216 * (1 + sin(π * (t - 0.5))))) with a fluctuation period of 2 s. The calculation process used Spaceclaim for modeling, ICEM to generate a structured mesh, and Fluent for solving.

[0029] Figure 2The outflow coefficients of the two embodiments and a cylindrical film gas orifice of the same diameter were compared over time. The horizontal axis represents time, and the vertical axis represents the outflow coefficient Cd. It can be seen that the outflow coefficient pulsation of the film gas orifices in Embodiments I and II is lower than that of the ordinary cylindrical film gas orifice. Using the difference between the maximum and minimum values ​​of the outflow coefficient as the parameter for evaluating pulsation, the pulsation of the outflow coefficient in Embodiment I was reduced by 13%, and the pulsation of the outflow coefficient in Embodiment II was reduced by 22%, fully demonstrating the effectiveness of this patent.

[0030] Figure 3 and Figure 4 The diagrams show velocity and pressure contours near the flow peak of two embodiments of the present invention and a cylindrical film gas orifice of the same diameter. It can be seen that the non-dissipative spatial structure induced by periodic pulsations distributed at the inlet and outlet of the film gas orifice leads to a non-uniform flow distribution and a strong suppression effect on pressure pulsations. Ultimately, this results in pressure pulsations and flow pulsations not maintaining the same amplitude, thus causing significant fluctuations in the flow coefficient. Embodiments I and II effectively enhance the pressure change response capability of the upstream region, restoring the pressure sensitivity to flow, and thus improving the pulsation of the outflow coefficient.

[0031] Figure 5 The diagram shows streamlines of two embodiments of the present invention and a cylindrical film gas orifice of the same diameter at the peak flow rate near the orifice. It can be seen that, due to the groove design, the film gas orifice in this embodiment actively forms a vortex structure in the groove region; and the distribution and intensity of this vortex structure exhibit a clear pattern. As the diameter of the groove increases, the vortex structure gradually shifts from the upstream region to the downstream region of the film gas orifice, while the intensity of the vortex structure significantly increases. On the one hand, the vortex structure enhances the pressure pulsation effect in the upstream region by perturbing the flow field; on the other hand, the enhanced upstream pressure pulsation further optimizes the coordination between pressure and flow pulsation, ultimately achieving an effective improvement in the amplitude of the outflow coefficient pulsation.

[0032] like Figure 6 As shown, a test system for measuring the flow characteristics of film gas orifices under pulsed flow is used for the above-mentioned fluid dynamics test of film gas orifices to suppress flow coefficient pulsation caused by gas turbine resonance. The system includes a hot-side simulation section and a cold-side simulation section. The film gas orifice is opened in the orifice plate 1. The orifice plate 1 is detachably clamped between the hot-side simulation section and the cold-side simulation section, and allows the airflow in the secondary flow chamber 2 to enter the main flow chamber 3 along the film gas orifice. The hot-side simulation section includes a high-flow-rate gas source system and a main flow chamber 3 located at the outlet of the high-flow-rate gas source system and used to provide airflow to simulate the hot side of the gas turbine. The cold-side simulation section includes a pressure-stabilized gas source system, a pulse flow generator 6 for rectifying the steady-state airflow provided by the pressure-stabilized gas source system into the required pulse flow, and a secondary flow chamber 2 located at the outlet of the pulse flow generator 6 and used to provide airflow for simulating the cold side of the gas turbine.

[0033] There are two significant improvements compared to conventional secondary flow test benches. First, the orifice plate 1 that carries the air film orifice can be quickly replaced. Second, the secondary flow is an adjustable pulsed flow.

[0034] like Figure 7-8 As shown, the main flow chamber 3 is a square tube with a panel hole 21 for the orifice plate 1 to be inserted into the bottom side, and the secondary flow chamber 2 is a square tube with a panel hole 21 for the orifice plate 1 to be inserted into the top side. The bottom of the main flow chamber 3 and the top of the secondary flow chamber 2 are close together. The upper and lower edges of the orifice plate 1 are engaged with the edges of the panel hole 21 of the main flow chamber 3 and the edges of the panel hole 21 of the secondary flow chamber 2 through a stop (that is, a stepped edge). The engaging surfaces are coated with vacuum sealing mud for sealing. To ensure sealing and control the cross-sectional size of the secondary flow chamber (a large cross-section would weaken the pulse amplitude), vacuum sealing mud is also filled in the secondary flow chamber 2 at a position away from the orifice plate 1.

[0035] The upper surface of the orifice plate 1 is flush with the upper surface of the bottom plate of the main flow chamber 3; Multiple ear plates 22 are respectively provided on the bottom edge of the main flow chamber 3 and the top plate of the secondary flow chamber 2. The ear plates 22 are arranged around the perforated plate 1. The main flow chamber 3 and the secondary flow chamber 2 are tightly fitted together by bolts passing through the ear plates 22. During the experiment, the airflow from the high-flow-rate air source system enters the main flow chamber 3 from one end of the main flow chamber 3, constructs a uniform steady-state flow field in the main flow chamber 3, and leaves from the other end of the main flow chamber 3; the secondary flow chamber 2 is open at one end and sealed at the other end, and the pulsed nitrogen flow from the pulse flow generator 6 enters the secondary flow chamber 2 along the open end of the secondary flow chamber 2 and is injected into the main flow chamber 3 through the air film hole.

[0036] Here, the main flow chamber 3 and the secondary flow chamber 2 are also the locations for sensor installation. In this embodiment, the temperature sensor and the pressure sensor are respectively installed through holes in the main flow chamber 3 and the secondary flow chamber 2, and the holes are sealed with glue.

[0037] The high-flow air source system includes a variable frequency fan 5, a vibration damping joint 51 connected to the air outlet of the variable frequency fan 5, and a honeycomb tube flow equalizer 31 connected to the outlet of the vibration damping joint 51 and used to eliminate eddies in the air entering the main flow chamber 3. The shock-absorbing joint 51 is a shock-absorbing throat, and the honeycomb tube flow equalizer 31 is a reducing pipe with a cross-section in the middle section larger than that at both ends. The reducing pipe is equipped with a honeycomb core with the same orientation as the reducing pipe.

[0038] The high-flow-rate air supply system here is used to generate high-flow-rate airflow of tens or even hundreds of meters per second. It is essentially a small wind tunnel. However, unlike conventional wind tunnels, the uniformity of airflow inside is required to be much higher. Therefore, it is necessary not only to ensure that the flow rate is sufficient, but also to ensure that it is not affected by vibration or eddies.

[0039] The pressure-stabilized gas source system includes a nitrogen cylinder 8 with a pressure reducing valve. The outlet pipeline of the pressure reducing valve passes through a pressure proportional valve 81 and a buffer tank 82 before being fed into the pulse flow generator 6.

[0040] The reason nitrogen cylinder 8 is used as the gas source is that conventional air compressors and other air sources actually output unsteady fluids with large fluctuations in temperature, flow rate, and pressure, which would cause unnecessary interference to our subsequent research. In contrast, the airflow output from nitrogen cylinder 8 is a relatively stable flow with velocity and pressure decreasing slowly over time. The pressure proportional valve 81, a special automatic valve incorporating PID control, is ideally suited for handling this type of fluid with slowly decreasing pressure and velocity, perfectly rectifying it into a steady-state flow. The reason nitrogen cylinder 8 is used instead of compressed air cylinders is that using air in the state equations during subsequent calculations would result in calculations affected by compositional fluctuations.

[0041] The reason for setting up an additional buffer tank 82 is not to make the gas flowing out of the pressure proportional valve 81 more stable, but to prevent downstream pressure fluctuations from being transmitted upwards and thus affecting the PID control process of the pressure proportional valve 81.

[0042] like Figure 9 As shown, the pulse current generator 6 includes a stepper reciprocating motor 61 fixed on the base and electrically connected to the frequency converter, a piston cylinder 62 with two open ends fixed on the base, and a perforated piston 63 driven by the stepper reciprocating motor 61 to reciprocate in the piston cylinder 62 with two open ends. The end of the perforated piston 63 is detachably connected to the crank connecting rod of the stepper reciprocating motor 61. When the perforated piston 63 moves in the piston cylinder 62 with two open ends, the position when it is pulled out to the limit is recorded as the initial position of the piston. The reason for using the piston cylinder 62 with openings at both ends is twofold: first, to ensure a sufficiently large stroke adjustment range, and second, to avoid repeatedly compressing air at one end during the movement of the perforated piston 63. The reason for using the stepper reciprocating motor 61, the perforated piston 63, and the piston cylinder 62 with openings at both ends to achieve the on / off switching of the pipeline is to achieve sufficient dynamic sealing while realizing high-frequency on / off switching.

[0043] The stepper reciprocating motor 61 used in this embodiment was designed and manufactured by Shengda Machinery. It uses a closed-loop motor as its power source, and converts the circular motion into reciprocating motion via a crank-connecting rod with a flywheel. The installation position of the crank-connecting rod is adjustable, thereby achieving adjustable stroke. The end of the crank-connecting rod of the stepper reciprocating motor 61 is screwed to the end of the perforated piston 63.

[0044] The adjustable stroke of the stepper reciprocating motor 61 is a prerequisite for many subsequent adjustments. Most manufacturers of stepper reciprocating motors 61 on the market can produce machines that achieve this effect, and can directly customize them.

[0045] The reason a stepper motor is used as the power source is that the speed of a conventional motor is affected by resistance, but a stepper motor is not. The speed of a stepper motor is only controlled by the frequency converter and is not affected by resistance, thus allowing the punching piston 63 to move at a specified frequency. However, stepper motors also have limitations. Their speed is relatively low; the frequency of most stepper motors cannot exceed 1000 revolutions per minute. This means that if the frequency of the pulse current is controlled solely by the frequency of the stepper motor, the upper limit of the pulse current frequency is 50 / 3Hz. Therefore, it is necessary to combine it with other types of frequency regulation designs to achieve higher frequencies.

[0046] like Figure 10 As shown, two aligned cylinder wall holes 622 are provided on the side wall of the piston cylinder 62 with open ends. A rectifier tube connector 64 is screwed into the two cylinder wall holes 622. The two rectifier tube connectors 64 are of the same specification and their central axes are collinear. The central axis of the rectifier tube connector 64 is perpendicular to and intersects the central axis of the piston cylinder 62 with open ends. The rectifier tube connector 64 must be easily replaceable, as different rectifier tube connectors 64 are needed to adjust the waveform. A screw connection is a convenient replacement method that avoids air leakage. In this embodiment, the rectifier tube connector 64 is an internally threaded pagoda head that screws into the cylinder wall hole 622.

[0047] The perforated piston 63 has at least one piston hole 631, which is a through hole perpendicular to the perforated piston 63. The geometric center line of the piston hole 631 is perpendicular to and intersects the central axis of the perforated piston 63. The geometric center line, that is, the line connecting the centers of the cross-sections, is similar to the concept of the central axis. However, considering that the piston hole 631 is not necessarily a circular hole, it cannot be described by the central axis when it is not a circular hole. Therefore, the geometric center line is used here. The central axis of the rectifier tube connector 64 is perpendicular to and intersects the central axis of the piston cylinder 62 with open ends, and the geometric center line of the piston hole 631 is perpendicular to and intersects the central axis of the perforated piston 63. This ensures that the movement direction of the perforated piston 63 is perpendicular to the fluid flow direction, thereby achieving flow cutoff. The perforated piston 63 also needs to be replaceable. Perforated pistons 63 with different numbers and shapes of piston holes 631 can be used to adjust the frequency and waveform.

[0048] The inside of the rectifier tube connector 64 is a straight channel of equal diameter, which is called the outer channel. The channel in the piston hole 631 is called the inner channel. During the reciprocating motion of the perforated piston 63, the outer channel is intermittently connected to each inner channel.

[0049] Existing solenoid valves rely on the intermittent reciprocating motion of the valve core to operate. There is an irreconcilable physical contradiction between high frequency and high flow rate – high flow rate requires a long valve core stroke and large mass, while high frequency requires low valve core inertia and a short stroke; both cannot be simultaneously achieved. The difference in this invention is that instead of the valve core performing the "start-stop, start-stop" reciprocating motion itself, a motor drives a high-inertia flywheel to rotate continuously. This rotational motion is forcibly converted into the reciprocating motion of the valve core through a crank-connecting rod or cam mechanism. In this way, the speed of the valve core's movement is determined by the motor speed, and the amplitude of the valve core's movement is determined by the mechanism dimensions; both can be adjusted independently and no longer mutually restrictive. Simultaneously, the previously harmful reciprocating inertia of the valve core is replaced by the beneficial rotational inertia of the flywheel, making the system operate more smoothly. Therefore, this invention can simultaneously achieve full opening and closing of the valve port and high flow rate output within the pipeline over a wide frequency range, solving a long-standing technical bottleneck that traditional solenoid valves have been unable to overcome. Meanwhile, in this invention, the flow rate at the valley point can be 0, while the flow rate at the peak point is 100%, which means that 100% flow rate modulation depth can be achieved.

[0050] Furthermore, while conventional pistons do not specifically suppress rotation, this one must. If the perforated piston 63 rotates, the outer and inner flow channels cannot align when needed. During operation, the perforated piston 63 can suppress rotation in the following way: Limit pin holes 621 are provided on the sides of the piston cylinder 62, which has openings at both ends. Anti-rotation pins 65 are inserted into limit grooves 633 along the limit pin holes 621. During the reciprocating motion of the perforated piston 63, the anti-rotation pins 65 slide in the limit grooves 633, preventing the perforated piston 63 from rotating.

[0051] During the operation of the perforated piston 63, the following feasible solutions for dynamic sealing are provided: the perforated piston 63 is provided with piston ring grooves 632 arranged around the perforated piston 63, with piston rings embedded inside for sealing; each piston hole 631 is provided with a piston ring groove 632 on each side for sealing when the outer flow channel and the inner flow channel are connected, and at least one piston ring groove 632 is provided between each end of the perforated piston 63 and the piston hole 631 adjacent to that end for sealing when the outer flow channel and the inner flow channel are not connected.

[0052] The specific usage method of this pulse current generator 6 is as follows: Of the two rectifier tube connectors 64, one is the inlet and the other is the outlet, with the inlet receiving steady-state fluid. During the reciprocating motion of the perforated piston 63, the outer flow channel is intermittently connected to each inner flow channel, causing the steady-state fluid to become a pulsed flow.

[0053] The frequency H of the pulse current can be adjusted in the following three ways: Method 1: Adjust the frequency A of the stepper reciprocating motor 61; Method 2: Adjust the number B of piston holes 631 on the perforated piston 63; Method 3: Adjust the initial position of the piston and the stroke of the stepper reciprocating motor 61 so that the number of times C of each inner flow channel and outer flow channel are connected changes for each rotation of the stepper reciprocating motor 61; here C is 1 or 2 (both the outward and return strokes can be connected); Where H = A × B × C.

[0054] The amplitude of the pulse stream can be adjusted in the following ways: An instantaneous pulse pre-regulation device is installed before the inlet pipe. This device includes a three-way valve 66 with one inlet and two outlets. One inlet of the valve 66 connects to a regulated gas source system, one outlet connects to the inlet of the pulse flow generator 6, and the other outlet connects to the outlet of the pulse flow generator 6. When it is necessary to adjust the pulse flow amplitude, the fluid flow rate entering the outlet of the pulse flow generator 6 is adjusted through the three-way valve 66. The smaller the fluid flow rate allocated to the outlet, the larger the final output pulse flow amplitude. This adjustment method is very intuitive; a portion of the fluid is released without rectification and then combined with the rectified fluid to adjust the amplitude. The adjustment range is 0-100% flow modulation depth, meaning that in the extreme condition (100% flow modulation depth), the flow valley value can be 0.

[0055] Adjust the duty cycle of the pulse stream using the following method: By adjusting the initial position of the piston, the stroke of the stepper reciprocating motor 61, and the spacing of the piston holes 631 when there are multiple piston holes 631, the ratio of the time the outer and inner flow channels are connected to the time they are not connected during one reciprocating motion of the perforated piston 63 is changed. Precise dimensional design is required during the design phase. The entire perforated piston 63 is vertically cut downwards along its central axis, and the vertical downward projection of the section is a horizontal line segment X. The portion of the inner flow channel projected onto line segment X is marked and denoted as line segment XA. The cross-section of the outer flow channel is also vertically projected downwards as a horizontal line segment Y. The mutual movement of the two line segments is simulated, and the overlap between line segment Y and line segment XA is observed. The position and size adjustments of each part are calculated to ensure that the proportion of the overlap time between line segment Y and line segment XA during the movement meets the requirements.

[0056] The waveform of the pulsed flow is adjusted by modifying the shape and size ratio of the outer and inner flow channels. For example, such as Figure 11As shown, to generate a sine wave, circular outer and inner channels of the same size are used, and during the reciprocating motion of the perforated piston 63, the outer and inner channels completely overlap at certain moments. To generate a square wave, a rectangular outer channel with a width not exceeding two millimeters and a rectangular inner channel with a length not less than 10 times the width of the outer channel are used. The length directions of the outer and inner channels are perpendicular, and their upper and lower edges are aligned. The width of the rectangular outer channel is narrow enough to achieve the step-like changes characteristic of square waves. The rectangular outer channel here is equivalent to a vertical slit, while the rectangular inner channel is equivalent to a long, horizontally positioned square hole.

[0057] After the pulse flow is generated, in order to avoid it being weakened or interfered with by the pipeline, the pulse flow generator 6 and the secondary flow chamber 2 need to be a constant diameter pipeline without diameter change, valves, or sudden contraction and expansion, and there should be no structure in the pipeline that would cause the boundary layer to detach.

[0058] This means that the secondary flow valve 7, used to regulate the secondary flow rate, must be placed in front of the pulse flow generator, and the flow rates of both the main flow and the secondary flow must be measured using a thermal mass flow meter 4 (this type of flow meter can measure the flow rate of high-frequency pulse flow, and the internal flow channel can be made into a straight pipe with the same diameter as the pipes before and after it, without any structure that causes boundary layer separation).

[0059] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A film pore for suppressing flow coefficient pulsation caused by gas turbine resonance, characterized in that: It consists of three interconnected and coaxially arranged cylindrical segments, namely the initial segment (11) with diameter D1, the expansion segment (12) with diameter D2, and the contraction segment (13) with diameter D3, where D2 > D3 > D1; the initial segment (11) is connected to the cold side; the expansion segment (12) is suddenly connected to the initial segment (11), and the contraction segment (13) is suddenly connected to the expansion segment (12) and is connected to the hot side. Through the connection method and size ratio design of the three-segment cylindrical structure, an inner groove structure is formed inside the air film hole.

2. The film gas pore for suppressing flow coefficient pulsation caused by gas turbine resonance according to claim 1, characterized in that: D1≤2mm, 1.05≤D2 / D1≤1.5, 1.0<D3 / D1≤1.

1.

3. The film pore for suppressing flow coefficient pulsation caused by gas turbine resonance according to claim 1, characterized in that: The ratio of the length Le of the expansion section (12) to the total length L of the air film pore is: 0.25≤Le / L≤0.75; L≥5mm.

4. The film gas pore for suppressing flow coefficient pulsation caused by gas turbine resonance according to claim 1, characterized in that: The geometric center of the expansion section (12) coincides with the geometric center of the entire air film pore.

5. A test system for measuring the flow characteristics of a film gas pore under pulsed flow, characterized in that: The fluid dynamics test for the film gas orifice for suppressing flow coefficient pulsation caused by gas turbine resonance as described in claim 1 includes a hot-side simulation section and a cold-side simulation section. The film gas orifice is opened in an orifice plate (1). The orifice plate (1) is detachably clamped between the hot-side simulation section and the cold-side simulation section, and allows the airflow in the secondary flow chamber (2) to enter the main flow chamber (3) along the film gas orifice. The hot-side simulation section includes a high-flow-rate gas source system and a main flow chamber (3) located at the outlet of the high-flow-rate gas source system and used to provide airflow for simulating the hot side of the gas turbine. The cold-side simulation section includes a pressure-stabilized gas source system, a pulse flow generator (6) for rectifying the steady-state airflow provided by the pressure-stabilized gas source system into the required pulse flow, and a secondary flow chamber (2) located at the outlet of the pulse flow generator (6) and used to provide the airflow for simulating the cold side of the gas turbine.

6. The test system for measuring the flow characteristics of a film gas pore under pulsed flow according to claim 5, characterized in that: The main flow chamber (3) is a square tube with a panel hole (21) for the orifice plate (1) to be inserted at the bottom of the side, and the secondary flow chamber (2) is a square tube with a panel hole (21) for the orifice plate (1) to be inserted at the top of the side. The bottom of the main flow chamber (3) and the top of the secondary flow chamber (2) are attached together. The upper and lower edges of the orifice plate (1) are respectively engaged with the edges of the panel hole (21) of the main flow chamber (3) and the edges of the panel hole (21) of the secondary flow chamber (2) through a stop. The engaging surfaces are coated with vacuum sealing mud for sealing. The upper surface of the orifice plate (1) is flush with the upper surface of the bottom plate of the main flow chamber (3); The bottom edge of the main flow chamber (3) and the top plate of the secondary flow chamber (2) are respectively provided with multiple corresponding upper and lower ear plates (22). The ear plates (22) are arranged around the perforated plate (1). The main flow chamber (3) and the secondary flow chamber (2) are tightly fitted together by bolts passing through the ear plates (22). During the experiment, the air flow from the high-flow gas source system enters the main flow chamber (3) from one end of the main flow chamber (3), constructs a uniform steady flow field in the main flow chamber (3), and leaves from the other end of the main flow chamber (3); the secondary flow chamber (2) is open at one end and sealed at the other end, and the pulsed nitrogen gas flow from the pulse flow generator (6) enters the secondary flow chamber (2) along the open end of the secondary flow chamber (2) and is injected into the main flow chamber (3) through the gas film hole.

7. The test system for measuring the flow characteristics of a film gas pore under pulsed flow according to claim 5, characterized in that: The high-flow air source system includes a variable frequency fan (5), a shock-absorbing joint (51) connected to the air outlet of the variable frequency fan (5), and a honeycomb tube flow equalizer (31) connected to the outlet of the shock-absorbing joint (51) and used to eliminate eddies in the air entering the main flow chamber (3). The shock-absorbing joint (51) is a shock-absorbing throat, and the honeycomb tube flow equalizer (31) is a variable diameter tube with a cross-section in the middle section larger than that at both ends. The variable diameter tube is provided with a honeycomb core facing the same direction as the variable diameter tube.

8. The test system for measuring the flow characteristics of a film gas pore under pulsed flow according to claim 5, characterized in that: The pressure-stabilized gas source system includes a nitrogen cylinder (8) with a pressure reducing valve. The outlet pipe of the pressure reducing valve passes through a pressure proportional valve (81) and a buffer tank (82) before being fed into the pulse flow generator (6).

9. A test system for measuring the flow characteristics of a film gas pore under pulsed flow according to claim 5, characterized in that: The pulse current generator (6) includes a stepper reciprocating motor (61) fixed on the base and electrically connected to the frequency converter, a piston cylinder (62) with two open ends fixed on the base, and a perforated piston (63) driven by the stepper reciprocating motor (61) to reciprocate in the piston cylinder (62) with two open ends. The end of the perforated piston (63) is detachably connected to the crank connecting rod of the stepper reciprocating motor (61). When the perforated piston (63) moves in the piston cylinder (62) with two open ends, the position when it is pulled out to the limit is recorded as the initial position of the piston. The stroke of the stepper reciprocating motor (61) is adjustable; The piston cylinder (62) with two open ends has two aligned cylinder wall holes (622) on its side wall. A rectifier tube connector (64) is screwed into the two cylinder wall holes (622). The two rectifier tube connectors (64) are of the same specification and their central axes are collinear. The central axis of the rectifier tube connector (64) is perpendicular to and intersects with the central axis of the piston cylinder (62) with two open ends. The perforated piston (63) has at least one piston hole (631), which is a through hole perpendicular to the perforated piston (63). The geometric center line of the piston hole (631) is perpendicular to and intersects the central axis of the perforated piston (63). The rectifier tube connector (64) has a straight channel of equal diameter inside, which is called the outer channel. The channel in the piston hole (631) is called the inner channel. During the reciprocating motion of the perforated piston (63), the outer channel is intermittently connected to each inner channel.

10. A test system for measuring the flow characteristics of a film gas pore under pulsed flow according to claim 5, characterized in that: The pulse flow generator (6) and the secondary flow chamber (2) are connected by a constant diameter pipe without diameter changes, valves, or sudden contraction or expansion, and there are no structures in the pipe that would cause the boundary layer to detach.

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