Nozzle structure, control method, control system and turbo expander

Abstract

The invention provides a nozzle structure, a control method, a control system and a turbo expander, the nozzle structure comprises an annular nozzle body and a plurality of blades arranged in the circumferential direction of the nozzle body, and a flow channel is formed between every two adjacent blades; the blade comprises a driving layer driven based on shape memory alloy, and the driving layer is connected with an external driving circuit. The external driving circuit sends a target driving electrical parameter control signal to the driving layer based on the target width of the throat part of the flow channel, the driving layer drives the blades to generate directional deformation under the driving of the target driving electrical parameter, and the throat part width of the flow channel is converted into the target width; wherein the target width is determined based on the flow parameter of the fluid flowing through the flow channel. Under the driving action of an external driving circuit, the blades can generate continuous flexible deformation, so that the width of the throat part of the flow channel reaches the target width, the dynamic adjustment of the throat part width is realized, the adjustment does not cause leakage, and the strict requirement of the high-parameter turbo expander on the variable working condition efficiency is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluid control, in particular to a nozzle structure, a control method, a control system and a turboexpander. BACKGROUND

[0002] In the field of fluid control of turboexpander, the traditional nozzle is usually of fixed structure, which has the main defect that the physical width of the throat of the flow passage cannot be dynamically adjusted, resulting in significant decline in nozzle efficiency under variable working conditions. Specifically, under low flow working conditions, fixed throat width will lead to reduced flow velocity, causing flow separation and thickening of the boundary layer, resulting in efficiency loss; while under high flow working conditions, shock loss is prone to occur due to supercritical flow velocity. In addition, the mechanically driven adjustable nozzle has problems such as response lag and leakage of working medium caused by the gap between the moving pairs, especially under partial load conditions, the leakage loss accounts for a large proportion. SUMMARY

[0003] The purpose of the embodiments of the present application is to provide a nozzle structure, a control method, a control system and a turboexpander.

[0004] The embodiments of the present application adopt the following technical solutions: a nozzle structure comprising:

[0005] an annular nozzle body and a plurality of vanes arranged along the circumferential direction of the nozzle body, a flow passage being formed between adjacent two vanes;

[0006] The vane comprises a driving layer based on shape memory alloy driving, and the driving layer is connected with an external driving circuit;

[0007] The external driving circuit sends a target driving electric parameter control signal to the driving layer based on a target width of the throat of the flow passage, and the driving layer drives the vane to occur directional deformation under the driving of the target driving electric parameter, so as to change the throat width of the flow passage to the target width;

[0008] The target width is determined based on the flow parameter of the fluid flowing through the flow passage.

[0009] In some embodiments, the vane comprises, from outside to inside, an outer thermal insulation layer, a flexible deformation wall layer and the driving layer;

[0010] A sensor is arranged on the inner side of the driving layer, and the sensor is used to determine the deformation of the vane at the throat position of the flow passage and the throat width of the flow passage.

[0011] In some embodiments, the driving layer is arranged in a wave-shaped topological path, or arranged in two wave-shaped topological paths arranged side by side.

[0012] In some embodiments, the driving layer comprises a shape memory alloy layer and an elastic substrate layer stacked together.

[0013] In some embodiments, the driving layer is electrically connected to the external driving circuit through a control line, and an insulating sleeve is arranged outside the control line.

[0014] The embodiments of the present application also provide a nozzle control method, comprising:

[0015] obtaining a current fluid flow parameter at an inlet of a flow channel in real time;

[0016] determining a target width of a throat of the flow channel based on a first model, wherein the first model is a relationship model between the fluid flow parameter at the inlet of the flow channel passing through the nozzle and the target width of the throat of the flow channel;

[0017] determining a target driving electrical parameter based on a current width of the throat of the flow channel and the target width;

[0018] sending the target driving electrical parameter to a driving layer of a blade of the nozzle, and driving the driving layer to drive the blade to occur directional deformation, so that the width of the throat of the flow channel is changed to the target width, wherein the driving layer is driven based on a shape memory alloy.

[0019] In some embodiments, the determining of the target driving electrical parameter based on the current width of the throat of the flow channel and the target width comprises:

[0020] obtaining a current width of the throat of the flow channel;

[0021] in a case where the current width of the throat of the flow channel is less than the target width, determining the driving electrical parameter as a forward current, and the blade occurs first direction deformation;

[0022] in a case where the current width of the throat of the flow channel is greater than the target width, determining the driving electrical parameter as a reverse current, or cutting off the forward current, and the blade occurs second direction deformation, the first direction being opposite to the second direction.

[0023] In some embodiments, the determining of the target driving electrical parameter based on the current width of the throat of the flow channel and the target width comprises:

[0024] in a case where a difference between the current width of the throat of the flow channel and the target width is a first difference, determining the driving electrical parameter as a first current value;

[0025] in a case where the difference between the current width of the throat of the flow channel and the target width is a second difference, determining the driving electrical parameter as a second current value; wherein the first current value is greater than the second current value.

[0026] determining that the target driving electrical parameter maintains a third current value when a difference between the current width of the throat of the flow passage and the target width is within a set threshold range, wherein the third current value is less than the second current value.

[0027] In some embodiments, the driving layer drives the whole blade to be deformed directionally to change the throat width of the flow passage to the target width, including:

[0028] obtaining a deformation amount of the blade;

[0029] adjusting a duty ratio and an amplitude of the driving electrical parameter based on the deformation amount of the blade to compensate for driving hysteresis of the driving layer.

[0030] Embodiments of the present application also provide a nozzle control system, including:

[0031] a flow monitoring module configured to obtain a current fluid flow parameter at an inlet of a flow passage in real time;

[0032] a determining module configured to determine a target width of a throat of the flow passage based on a first model, wherein the first model is a relationship model between a fluid flow parameter at the inlet of the flow passage flowing through the nozzle and the target width of the throat of the flow passage;

[0033] a driving module configured to determine a target driving electrical parameter based on a current width of the throat of the flow passage and the target width;

[0034] sending the target driving electrical parameter to a driving layer of a blade of the nozzle to drive the driving layer to drive the whole blade to be deformed directionally to change the throat width of the flow passage to the target width, wherein the driving layer is driven based on a shape memory alloy.

[0035] In some embodiments, the nozzle control system further includes:

[0036] a feedback module configured to detect the width of the throat of the flow passage in real time and send a detection result to the driving module.

[0037] Embodiments of the present application also provide a turbo expander including the nozzle structure as described in any of the above embodiments.

[0038] Embodiments of the present application have the following beneficial effects:

[0039] The target width of the throat of the flow channel can be determined according to the fluid flow parameter of the flow channel, the blade on the nozzle ring is designed as a structure with a driving layer based on a shape memory alloy, so that the driving layer can drive the blade to continuously deform flexibly under the driving action of an external driving circuit, and then the width of the throat of the flow channel reaches the target width, the throat width dynamic adjustment can be realized, and the adjustment will not leak due to the deformation of the blade, and the strict requirements of the high-parameter turboexpander on the variable working condition efficiency are met. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0041] Figure 1 The schematic diagram of the nozzle structure of the present application is shown in the figure.

[0042] Figure 2 The schematic diagram of the nozzle blade arrangement of the present application is shown in the figure.

[0043] Figure 3 The schematic diagram of the driving layer structure of the present application is shown in the figure.

[0044] Figure 4 The schematic diagram of another structure of the driving layer of the present application is shown in the figure.

[0045] Figure 5 The schematic diagram of the relationship between the throat width before and after the change of the present application is shown in the figure.

[0046] Figure 6 The flow chart of the nozzle control method of the present application is shown in the figure.

[0047] Figure 7 Another flow chart of the nozzle control method of the present application is shown in the figure.

[0048] Reference signs: 1, nozzle body; 2, blade; 21, outer thermal insulation layer; 22, flexible deformation wall surface layer; 23, driving layer; 231, shape memory alloy layer; 232, elastic matrix layer; 3, flow channel; 31, inlet section; 32, outlet section; 33, throat; 4, displacement sensor. DETAILED DESCRIPTION

[0049] The various schemes and features of the present application are described herein with reference to the accompanying drawings.

[0050] It is to be understood that various modifications can be made to the embodiments described herein. Thus, the description is not to be considered as limiting, but merely as a description of exemplary embodiments. Other modifications of the application will occur to those skilled in the art upon reading the description of the application.

[0051] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and, together with the general description of the application given above, and the detailed description of the embodiments given below, serve to explain the principles of the present application.

[0052] These and other characteristics of the present application will become apparent upon consideration of the following detailed description of preferred forms of the application, given by way of non-limiting example, with reference to the accompanying drawings.

[0053] It should also be understood that, although the present application has been described in relation to certain specific examples, many other equivalents and modifications are possible.

[0054] The above and other aspects, features and advantages of the present application will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, when considered in conjunction with the following detailed description.

[0055] Specific embodiments of the present application are described hereinafter, by way of non-limiting example; however, it should be understood that many other embodiments can be implemented in accordance with the teachings of the present application. Functionally similar or equivalent components have not been described in detail, in order to avoid obscuring the present application unnecessarily. Thus, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present application in virtually any appropriate detailed structure.

[0056] The present specification can use the phrases "in one embodiment," "in another embodiment," "in yet another embodiment," or "in at least one embodiment" which can refer to one or more of the same or different embodiments of the application.

[0057] Firstly, the basic structure of the nozzle in the present application is introduced. The channel cross section of the scaling nozzle is in the shape of first contraction and then expansion from the inlet to the outlet. Along the flow direction of the fluid, it mainly includes the inlet section, the contraction section, the throat, the expansion section and the outlet section.

[0058] Take the nozzle of a turboexpander as an example. The inlet section is located at the front end of the nozzle and is usually designed as a smooth bell mouth or a cylinder, which is used to guide the high-pressure gas (fluid) to enter the nozzle smoothly, reduce the impact and vortex loss of the gas flow, and ensure the stability of the gas flow. The contraction area after the inlet section is the contraction section, and the cross-sectional area of the passage gradually changes from large to small. The generatrix of the contraction section is usually in the form of a circular arc, a parabola or a double clothoid curve (rather than a straight line), which is used to make the velocity of the gas increase uniformly and the pressure decrease smoothly during the contraction process, so as to avoid local flow separation. The connection point between the contraction section and the expansion section corresponds to the throat, which is the smallest part of the nozzle passage cross section and is also called the "critical cross section". The gas velocity at this point is equal to the local sound velocity (Mach number Ma = 1), which is the key position for the transition of the gas from subsonic speed to supersonic speed. The size precision of the throat has a great influence on the performance of the nozzle, and the processing error usually needs to be controlled within 0.01 mm. The expansion area after the throat corresponds to the expansion section, and the cross-sectional area of the passage continuously increases from small to large. The generatrix of the expansion section is also a smooth curve (such as the Vitousevsky curve), which is used to accelerate the gas at supersonic speed and further convert the pressure energy of the gas into kinetic energy, so that the gas flow velocity at the outlet reaches supersonic speed (Ma > 1) to meet the demand of the high-speed gas flow of the working wheel. The end of the expansion section corresponds to the outlet section, and the cross-sectional shape needs to match the inlet blade angle of the working wheel to ensure that the high-speed gas flow can enter the blade passage of the working wheel at the best angle, reduce the impact loss of the gas flow and the blade, and improve the energy transfer efficiency.

[0059] In a turboexpander, the nozzle usually exists in the form of a nozzle ring - a plurality of separate nozzles are uniformly distributed in the circumferential direction and are fixed on the nozzle seat by welding, bolting or inlaying to form an annular passage. The number of nozzle rings is determined according to the flow and power requirements of the expander. The number of nozzles of a small expander is generally 10-20, and the number of nozzles of a large expander can exceed 30.

[0060] Some turboexpanders have adjustable nozzles, which can adjust the cross-sectional area or flow direction of the nozzle outlet (such as rotating the nozzle blade angle) to adjust the working condition of the expander to meet the operating requirements under different loads. For example, the adjustable nozzle structure in the background art.

[0061] To solve the problems in the background art, the present application provides a nozzle structure, which combines Figure 1 The nozzle structure includes an annular nozzle body 1 and a plurality of blades 2 arranged along the circumferential direction of the nozzle body 1, and a flow passage 3 is formed between adjacent two blades 2. The size of the part of the flow passage 3 close to the inlet section 31 is larger, and the size of the part of the flow passage 3 close to the outlet section 32 is smaller, so as to form the flow passage 3 structure as described above (tapered streamline type, wide inlet and narrow outlet). The blade 2 is in a smooth streamline structure, and the fluid (or medium) can flow through the inlet section 31, the contraction section, the throat 33, the expansion section and the outlet section 32 of the flow passage 3 in sequence along the flow direction of the fluid.

[0062] The vane 2 in the application comprises a driving layer 23 driven by a shape memory alloy (SMA), which is electrically connected with an external driving circuit (not shown in the figure). Under the driving of the driving circuit, the driving layer 23 can be deformed in a certain direction, and in turn the vane 2 is also deformed in a certain direction, so as to directly change the physical width of the throat 33 of the flow passage 3, and continuously adjust the width of the flow passage 3. Moreover, the deformation process does not need mechanical transmission structure, so as to realize zero leakage sealing. In addition, compared with the mechanical transmission type adjusting nozzle, the application has the advantage of rapid response to the adjustment of the cross-sectional width of the throat 33.

[0063] In some examples, the vane 2 can be formed as a thin-walled structure of a high-temperature elastic alloy (for example, a nickel-based high-temperature alloy).

[0064] The external driving circuit sends a target driving electrical parameter control signal to the driving layer 23 based on the target width of the throat 33 of the flow passage 3, and the driving layer 23 drives the vane 2 to deform in a certain direction under the driving of the target driving electrical parameter, so as to change the width of the throat 33 of the flow passage 3 to the target width. In the application, the SMA-based driving layer 23 has a bidirectional driving function, and can deform in different directions under the stimulation of different target driving electrical parameters. For example, in combination with Figure 5 In the case that the target driving electrical parameter is a positive current, the SMA-based driving layer 23 can make the vane 2 contract, so as to make the vane 2 contract inward, increase the cross-sectional width of the flow passage 3, and increase the cross-sectional width at the position of the throat 33. That is, the original wall surface of the vane 2 contracts inward to the position of the changed wall surface, and the width of the throat 33 increases from the original throat 33 width to the changed throat 33 width. In the case that the driving of the driving circuit is cut off or the target driving electrical parameter is a negative current, the SMA-based driving layer 23 can make the vane 2 return to the original state or deform outward, so as to reduce the cross-sectional width of the flow passage 3, and reduce the cross-sectional width at the position of the throat 33.

[0065] The target width is determined based on the flow parameter of the fluid flowing through the flow passage 3. For example, the target width can be determined by the flow rate or the flow velocity of the fluid flowing through the flow passage 3. In the case of low flow rate, the cross-sectional width of the throat 33 of the flow passage 3 can be appropriately reduced, the flow rate is increased, and flow separation and boundary layer thickening are avoided, so as to avoid efficiency loss. In the case of high flow rate, the cross-sectional width of the throat 33 of the flow passage 3 can be appropriately increased, so as to avoid shock loss caused by supercritical flow velocity.

[0066] The target width of the throat 33 of the flow passage 3 can be determined by the fluid flow parameter of the flow passage 3, the blade 2 on the nozzle ring is designed to have a structure with a driving layer 23 driven by a shape memory alloy, so that the driving layer 23 can drive the blade 2 to continuously deform under the driving action of the external driving circuit, and then the width of the throat 33 of the flow passage 3 reaches the target width, which can realize the dynamic adjustment of the width of the throat 33, and the adjustment will not leak due to the deformation of the blade 2, which meets the strict requirements of the variable working condition efficiency of the high-parameter turboexpander.

[0067] In some embodiments, in combination Figure 2 , the blade 2 comprises, from outside to inside, an outer thermal insulation layer 21, a flexible deformation wall layer 22 and a driving layer 23. The cross sections of the outer thermal insulation layer 21, the flexible deformation wall layer 22 and the driving layer 23 are all annular, and the inner side of the driving layer 23 has a space that can deform inward.

[0068] The inner side of the driving layer 23 can be provided with a sensor, which can be a displacement sensor 4. The sensor is used to determine the deformation of the blade 2 at the throat 33 position of the flow passage 3 and the width of the throat 33 of the flow passage 3. The displacement sensor 4 can be fixed on the inner side of the driving layer 23.

[0069] The outer thermal insulation layer 21 can be a thermal insulation coating layer arranged on the outer side of the flexible deformation wall.

[0070] In some embodiments, in combination Figure 3 and Figure 4 , the driving layer 23 is arranged in a wave-shaped topological path, or arranged in two parallel wave-shaped topological paths. As shown in Figure 4 , the convex and concave parts of the two wave shapes can be one-to-one corresponding, so that Figure 4 the upper and lower wave shapes can be symmetrically arranged.

[0071] The driving layer 23 is arranged in a spatial expansion path (such as a wave shape, a double wave shape) to convert its linear strain into macro displacement, which helps to improve the deformation efficiency and stroke range.

[0072] The driving layer 23 can include a shape memory alloy layer 231 and an elastic substrate layer 232 stacked together. The shape memory alloy can use a TiNi-based alloy wire, and the elastic substrate can be made of a silicone compatible material. The TiNi-based alloy wire can form a network structure, which can be used as the shape memory alloy layer 231. The shape memory alloy layer 231 and the elastic substrate layer 232 can be fixed together to form the driving layer 23. Of course, it can be understood that other materials can also be used to make the above-mentioned driving layer 23, which is only used as an example and does not constitute a limitation to the scope of protection of the claims.

[0073] In the case that the shape memory alloy layer 231 of the driving layer 23 is made of TiNi-based alloy wires, the end portions of the TiNi-based alloy wires can be electrically connected to an external driving circuit through control lines, and an insulating sleeve is arranged outside the control lines.

[0074] In addition, based on the same inventive concept, the application further provides a nozzle control method, which can be a method for controlling the nozzle structure.

[0075] In combination Figure 6 and Figure 7 The method comprises:

[0076] S10, obtaining a current fluid flow parameter at the inlet of the flow passage in real time.

[0077] S20, determining a target width of the throat of the flow passage based on a first model, wherein the first model is a relationship model of the fluid flow parameter at the inlet of the flow passage passing through the nozzle and the target width of the throat of the flow passage.

[0078] S30, determining a target driving electrical parameter based on the current width of the throat of the flow passage and the target width.

[0079] S40, sending the target driving electrical parameter to the driving layer of the blade of the nozzle, driving the driving layer to drive the blade to occur directional deformation, so that the width of the throat of the flow passage is changed to the target width, wherein the driving layer is driven based on a shape memory alloy.

[0080] For example, the control method can determine the quantitative relationship between the real-time flow and the target throat width by pre-establishing a mathematical model of the fluid flow parameter (such as flow or flow rate) and the throat width of the flow passage. The mathematical model can be understood as the first model described above. The relevant parameters of the first model can also be updated in real time according to the actual working conditions, so that the first model is more suitable for the nozzle structure.

[0081] The mapping relationship between the driving electrical parameter (such as driving current) of the driving layer and the displacement of the blade is calibrated by experiment, and a driving electrical parameter reference table is generated.

[0082] When the real-time adjustment of the cross-sectional width of the throat of the flow passage is performed, step S10 can be performed, that is, the current fluid flow parameter at the inlet of the flow passage is obtained in real time. For example, a flow meter or other flow or flow rate sensor can be arranged at the inlet of the flow passage to obtain the fluid flow at the inlet of the flow passage.

[0083] After obtaining the fluid flow, step S20 can be performed to calculate the target width of the cross section of the throat of the flow passage according to the first model described above.

[0084] After determining the target width of the throat section of the flow passage, step S30 can be performed to determine the target driving electric parameter based on the above-mentioned driving electric parameter reference table. Then, step S40 is performed to send the target driving electric parameter to the driving layer through the driving circuit to drive the driving layer to cause the blade to be oriented deformed to change the throat width of the flow passage to the target width.

[0085] When real-time adjustment is performed, a multi-stage voltage driving strategy can be adopted:

[0086] For example, a strong driving stage: a short-time high voltage is applied to quickly trigger the SMA phase change.

[0087] A maintenance stage: switch to the rated voltage, and finely adjust the deformation amount with the help of the displacement sensor.

[0088] A reset stage: the SMA is prompted to recover by cutting off or reversing the current.

[0089] An adaptive compensation mechanism: a physical model is established by calibrating the current-deformation-throat width relationship, and the parameters of the related model and the driving electric parameter are dynamically corrected in combination with real-time displacement feedback.

[0090] In some embodiments, the target driving electric parameter is determined based on the current width of the throat of the flow passage and the target width, including:

[0091] S301: obtaining the current width of the throat of the flow passage.

[0092] S302: in the case where the current width of the throat of the flow passage is less than the target width, determining the driving electric parameter as a forward current, and the blade is deformed in a first direction.

[0093] In the case where the current width of the throat of the flow passage is greater than the target width, the driving electric parameter is determined as a negative current, or the forward current is cut off, and the blade is deformed in a second direction, the first direction being opposite to the second direction.

[0094] For example, the current width of the throat section of the flow passage is L1, and the target width is L2.

[0095] If L1 is less than L2, it means that the current width of the throat section of the flow channel needs to be increased, and the target driving electrical parameter is determined as I1 (such as current). Since the width of the throat section of the flow channel is continuously adjusted in the present application, as the width of the throat section continuously increases, when the value approaches L2, the driving stimulation of the driving layer by the driving circuit (such as turning off the driving circuit switch) or the application of the target driving electrical parameter I2 opposite to I1 by the driving circuit can be cut off. Since the driving layer is made of shape memory alloy, after the driving stimulation of the driving layer by the driving circuit is cut off or the reverse current is applied, the driving layer will return to L2.

[0096] Similarly, if L1 is greater than L2, it means that the current width of the throat section of the flow channel needs to be adjusted, and the target driving electrical parameter can be determined as I3. Similarly, as the adjustment proceeds, when L1 approaches L2, the driving circuit can be cut off or the target driving electrical parameter I4 opposite to I3 can be applied.

[0097] During the adjustment, the displacement of the vane can be continuously obtained by the displacement sensor, that is, the displacement sensor can continuously feedback the detection result.

[0098] In some embodiments, the target driving electrical parameter is determined based on the current width of the throat of the flow channel and the target width, including:

[0099] When the difference between the current width of the throat of the flow channel and the target width is a first difference, the driving electrical parameter is determined as a first current value.

[0100] When the difference between the current width of the throat of the flow channel and the target width is a second difference, the driving electrical parameter is determined as a second current value; wherein the first current value is greater than the second current value.

[0101] That is, if the measured width of the throat section is less than the target width, a positive high-voltage pulse can be output to drive the SMA to contract to increase the throat width. If the measured width of the throat section is greater than the target width value, the current can be cut off, and the elastic reset is used to reduce the throat width.

[0102] When the difference between the current width of the throat of the flow channel and the target width is within a set threshold range, the target driving electrical parameter is determined to maintain a third current value, wherein the third current value is less than the second current value. That is, when the difference between the current width of the throat of the flow channel and the target width is within a set threshold range, steady-state maintenance can be performed, and when the throat width deviation is lower than the set threshold value, it is determined to enter the steady state; switch to a low-voltage maintenance mode to lock the throat width with the minimum current and reduce the system energy consumption.

[0103] In some embodiments, the driving layer drives the whole blade to deform to change the throat width of the flow passage to the target width, including:

[0104] The deformation amount of the blade is obtained, and the duty cycle and amplitude of the driving electrical parameter are adjusted based on the deformation amount of the blade to compensate for the driving hysteresis of the driving layer. The driving hysteresis refers to the time difference or state deviation between the actual response (deformation) of the driving layer and the input electrical signal instruction (target driving electrical parameter) (for example, the electrical signal instruction has deformed the SMA to the target width, but the deformation needs to be delayed for a period of time to reach the target width).

[0105] For example, it is required that the blade accurately reaches the target width within 0.5 seconds after the target driving electrical parameter is input.

[0106] Without compensation at the beginning, there is a significant hysteresis problem:

[0107] After power-on (initial parameters: amplitude 12V, duty cycle 50%), the SMA needs 0.3 seconds to start shrinking, and finally takes 0.8 seconds to deform the blade (0.3 seconds of over-target time). After power-off, the SMA cools slowly, and the blade needs 1.2 seconds to recover to 5mm (0.7 seconds of over-target time), and there is a deformation stagnation in the middle (almost no recovery in the first 10 seconds of cooling).

[0108] The deformation hysteresis in the power-on heating stage can be compensated by adjusting the amplitude.

[0109] The deformation of the SMA depends on the heating to reach the phase transition temperature (such as the austenite transition temperature A s ≈60℃) of TiNi alloy”. When the initial amplitude (12V) is too low, the heating rate is slow, and it takes a longer time to reach the phase transition temperature, resulting in a start-up hysteresis after power-on.

[0110] The driving voltage amplitude can be increased from 12V to 15V (while keeping the duty cycle unchanged at 50%) in the initial power-on stage. A higher amplitude means a larger current (according to Ohm's law I=U / R), and the SMA heating rate is accelerated, and the phase transition temperature (A s ) can be reached faster, shortening the hysteresis time.

[0111] After adjustment, the SMA only needs 0.1 seconds to reach the phase transition temperature and start shrinking, and the total deformation time of the blade is shortened to 0.3 seconds, accurately matching the target response time.

[0112] The deformation hysteresis in the power-off cooling stage can also be compensated by adjusting the duty cycle.

[0113] For example, after the SMA is powered off, it relies on environmental cooling to restore the deformation. If the cooling rate is slow, it will cause the deformation recovery to lag. At this time, the duty cycle can be adjusted by intermittent low-amplitude power supply to balance the power generation and environmental heat dissipation, avoid the recovery stagnation caused by too low temperature of the SMA, and accelerate the deformation recovery.

[0114] After the SMA is powered off, the SMA wire is quickly cooled to room temperature (such as 25℃), which is lower than the martensite recovery temperature (M s ≈30℃), which causes the atomic arrangement to be difficult to recover, the deformation to stagnate (almost no displacement in the first 0.5 seconds), and the total recovery time to be 1.2 seconds. Therefore, instead of directly cutting off the power, a low-amplitude (8V) + low-duty-cycle (20%) pulse electrical signal can be used (i.e., only 0.2 seconds of power-on and 0.8 seconds of power-off in 1 second). The low amplitude (8V) ensures that the heat generated during power-on is small, so that the SMA does not shrink again. The intermittent power-on with a 20% duty cycle can maintain the temperature of the SMA near the M s (30℃), and at the same time, the environmental heat dissipation during the power-off interval can make the SMA slowly and continuously recover the original length, thereby accelerating the deformation recovery. After adjustment, the SMA starts to recover the deformation within 0.2 seconds after being powered off, and the total time of the deformation of the blade is shortened to 0.3 seconds, thereby solving the lag of the deformation recovery in the cooling stage.

[0115] The duty cycle and the amplitude can also be adjusted cooperatively, which will not be described here.

[0116] The nozzle control system provided by the embodiments of the present application comprises:

[0117] A flow monitoring module configured to obtain the current fluid flow parameter at the inlet of the flow channel in real time.

[0118] A determination module configured to determine the target width of the throat of the flow channel based on a first model, wherein the first model is a relationship model between the fluid flow parameter at the inlet of the flow channel passing through the nozzle and the target width of the throat of the flow channel.

[0119] A driving module configured to determine the target driving electrical parameter based on the current width of the throat of the flow channel and the target width.

[0120] The target driving electrical parameter is sent to the driving layer of the blade of the nozzle, and the driving layer is driven to drive the whole blade to occur directional deformation, so that the width of the throat of the flow channel is changed to the target width, wherein the driving layer is driven based on the shape memory alloy.

[0121] For example, the control system can determine the quantitative relationship between the real-time flow rate and the target throat width by pre-establishing a mathematical model of the fluid flow parameter (e.g. flow rate or flow velocity) and the throat width of the flow passage. The mathematical model can be understood as the first model described above. The relevant parameters of the first model can also be updated in real time according to the actual working conditions, so that the first model is more suitable for the nozzle structure.

[0122] The mapping relationship between the driving electrical parameter (e.g. driving current) of the driving layer and the displacement of the blade is calibrated by experiment, and a driving electrical parameter reference table is generated.

[0123] When adjusting the throat section width of the flow passage in real time, the flow monitoring module can be used to obtain the current fluid flow parameter at the inlet of the flow passage in real time. For example, a flow meter or other flow or flow rate sensor can be arranged at the inlet of the flow passage to obtain the fluid flow at the current inlet of the flow passage.

[0124] After obtaining the fluid flow, the determination module can calculate the target width of the throat section of the flow passage according to the first model described above.

[0125] After determining the target width of the throat section of the flow passage, the driving module can determine the target driving electrical parameter based on the driving electrical parameter reference table described above. Then the driving circuit of the driving module sends the target driving electrical parameter to the driving layer to drive the driving layer to drive the blade to occur directional deformation, so that the throat width of the flow passage changes to the target width.

[0126] In real-time adjustment, a multi-stage voltage driving strategy can be used:

[0127] For example, the strong driving stage: a short-time high voltage is applied to quickly trigger the SMA phase change.

[0128] The maintenance stage: switch to the rated voltage, and finely adjust the deformation amount with the help of the displacement sensor.

[0129] The reset stage: promote the SMA to recover by cutting off or reversing the current.

[0130] Adaptive compensation mechanism: establish a physical model by calibrating the current-deformation-throat width relationship, and dynamically correct the parameters of the related model and the driving electrical parameter combined with real-time displacement feedback.

[0131] In some embodiments, the nozzle control system further comprises:

[0132] A feedback module for real-time detection of the width of the throat of the flow passage, and sending the detection result to the driving module. The feedback module can use a displacement sensor, and the feedback module can be arranged on the driving layer of the nozzle structure.

[0133] The embodiment of the present application further provides a turboexpander comprising the nozzle structure as described in any of the above embodiments.

[0134] The above describes in detail the embodiments of the present application, but the present application is not limited to the specific embodiments, and the skilled in the art can make various modified embodiments on the basis of the concept of the present application, and the modified embodiments shall fall within the scope of the present application.

Claims

1. A nozzle structure, characterized in that, include: The annular nozzle body and multiple blades arranged along the circumference of the nozzle body form a flow channel between two adjacent blades; The blade includes a drive layer driven by a shape memory alloy, and the drive layer is connected to an external drive circuit. The external drive circuit sends a target drive electrical parameter control signal to the drive layer based on the target width of the throat of the flow channel. Under the drive of the target drive electrical parameters, the drive layer causes the blade to undergo directional deformation, transforming the throat width of the flow channel into the target width. The target width is determined based on the fluid flow parameters flowing through the channel.

2. The nozzle structure according to claim 1, characterized in that, The blade comprises, from the outside to the inside, an outer heat insulation layer, a flexible deformable wall layer, and the driving layer; A sensor is provided on the inner side of the drive layer. The sensor is used to determine the deformation of the blade at the throat position of the flow channel and the throat width of the flow channel.

3. The nozzle structure according to claim 1, characterized in that, The driving layer is arranged in a wave-shaped topological path, or in two parallel wave-shaped topological paths.

4. The nozzle structure according to claim 1, characterized in that, The driving layer comprises stacked shape memory alloy layers and an elastic substrate layer.

5. The nozzle structure according to claim 1, characterized in that, The driving layer is electrically connected to the external driving circuit via a control line, and an insulating sleeve is provided outside the control line.

6. A nozzle control method, characterized in that, include: Real-time acquisition of current fluid flow parameters at the inlet of the flow channel; Based on the first model, the target width of the throat of the flow channel is determined, wherein the first model is a model relating the fluid flow parameters at the inlet of the flow channel through the nozzle to the target width of the throat of the flow channel. Based on the current width of the throat of the flow channel and the target width, the target driving electrical parameters are determined; The target driving electrical parameters are sent to the driving layer of the nozzle blades to drive the driving layer to cause the blades to undergo directional deformation, so that the throat width of the flow channel is transformed into the target width, wherein the driving layer is driven based on shape memory alloy.

7. The method according to claim 6, characterized in that, The target driving electrical parameters are determined based on the current width of the throat of the flow channel and the target width, including: Obtain the current width of the throat of the flow channel; If the current width of the throat of the flow channel is less than the target width, the driving electrical parameter is determined to be a positive current, and the blade undergoes deformation in the first direction. If the current width of the throat of the flow channel is greater than the target width, the driving electrical parameter is determined to be a negative current, or the positive current is cut off, and the blade undergoes a second-direction deformation, the first direction being opposite to the second direction.

8. The method according to claim 6, characterized in that, The target driving electrical parameters are determined based on the current width of the throat of the flow channel and the target width, including: When the difference between the current width of the throat of the flow channel and the target width is a first difference, the driving electrical parameter is determined to be a first current value; When the difference between the current width of the throat of the flow channel and the target width is a second difference, the driving electrical parameter is determined to be a second current value; wherein, the first current value is greater than the second current value; When the difference between the current width of the throat of the flow channel and the target width is within a set threshold range, a third current value is determined to maintain the target driving electrical parameter, wherein the third current value is less than the second current value.

9. The method according to claim 6, characterized in that, The driving layer causes the blade to undergo directional deformation, so that the throat width of the flow channel is transformed into the target width, including: Obtain the deformation of the blade; Based on the deformation of the blade, the duty cycle and amplitude of the driving electrical parameters are adjusted to compensate for the driving lag of the driving layer.

10. A nozzle control system, characterized in that, include: The flow monitoring module is configured to obtain the current fluid flow parameters at the inlet of the flow channel in real time. The determination module is configured to determine the target width of the throat of the flow channel based on a first model, wherein the first model is a model relating the fluid flow parameters at the inlet of the flow channel through the nozzle to the target width of the throat of the flow channel. A drive module configured to determine target drive electrical parameters based on the current width of the throat of the flow channel and the target width; The target driving electrical parameters are sent to the driving layer of the nozzle blades to drive the driving layer to cause the blades to undergo directional deformation, so that the throat width of the flow channel is transformed into the target width, wherein the driving layer is driven by a shape memory alloy.

11. The nozzle control system according to claim 10, characterized in that, The nozzle control system also includes: The feedback module is used to detect the width of the throat of the flow channel in real time and send the detection result to the drive module.

12. A turbine expander, characterized in that, Includes the nozzle structure as described in any one of claims 1 to 5.

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