Annular vapor ejector with anti-condensation microwave heating device

Abstract

The application discloses a ring-shaped steam ejector with a condensation-proof microwave heating device, and relates to the technical field of steam ejectors.The ring-shaped steam ejector comprises an ejector body and a microwave heating device.The ejector body is provided with a Laval nozzle for spraying working steam.The microwave heating device comprises a microwave generator and a waveguide tube.The microwave generator is used for generating high-frequency microwaves with a frequency close to the resonance frequency of water vapor, and the waveguide tube is used for conducting the high-frequency microwaves to the Laval nozzle.The traditional steam ejector has the problem that accumulated water cannot be discharged in time, which has an adverse effect on the structure and performance of the ejector.Compared with the prior art, the application adds a microwave heating device, utilizes the characteristics of non-contact, rapidness, high efficiency and precise control of microwave heating, heats the steam at the Laval nozzle, and reduces the generation of condensed water.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steam ejector, and particularly relates to an annular steam ejector with a condensation-proof microwave heating device. BACKGROUND

[0002] The steam ejector is a kind of fluid mechanical device which uses high-pressure working steam to suck low-pressure ejecting steam and forms medium-pressure steam, has the characteristics of simple and reliable structure, low operating cost and remarkable energy-saving effect, and is widely applied to fields such as seawater desalination, refrigeration, chemical industry, rocket and jet aircraft propulsion system and energy storage. The working principle is as follows: the high-temperature and high-pressure working steam passes through a Laval nozzle, and its static pressure is converted into dynamic pressure, the fluid velocity is increased, reaches the sound velocity at the throat position of the nozzle, and continues to accelerate to supersonic velocity in the diverging section, so that a low-pressure area is formed at the nozzle outlet, and the ejecting steam is sucked into the mixing chamber by the high-speed and low-pressure steam. The mixed steam enters the diffuser chamber to expand and diffuse, the flow velocity is reduced, and the steam state required by the user is reached. However, in the acceleration process in the Laval nozzle, the fluid temperature also sharply decreases, and when the temperature is lower than the saturation temperature of the current pressure, condensation occurs. Condensation in the nozzle will cause congestion in the ejector, which will adversely affect the structure and performance of the ejector.

[0003] The utility model patent (CN201921798328.7) discloses a combined steam ejector with a hydrophobic function, which comprises a plurality of independent ejectors and connecting parts, each ejector is provided with a hydrophobic mechanism for separately controlling the discharge of water in each ejector. However, the problem of condensation in the steam ejector has not been fundamentally solved.

[0004] The above steam ejector solves the problem of water accumulation in the ejector by combining multiple ejectors and separately opening a hydrophobic mechanism for each ejector. However, for different working conditions, the degree of water accumulation is different, and if the accumulated water cannot be discharged in time, it will still have a great adverse effect on the performance of the ejector. In addition, some existing steam ejectors solve the internal condensation problem by increasing the superheat degree of the working steam, but a larger superheat degree will produce a larger thermal stress, which requires a higher structural strength of the ejector, and it is difficult to meet the changing working conditions. Therefore, the problem of condensation in the ejector needs to be solved. SUMMARY

[0005] To solve the problems in the prior art, the application provides an annular steam ejector with a condensation-proof microwave heating device.

[0006] The application adopts the following technical scheme:

[0007] The application discloses a ring-shaped steam ejector with a condensation-preventing microwave heating device, which comprises an ejector body, a Laval nozzle arranged on the ejector body for injecting working steam, and a mixing chamber and a diffuser chamber arranged on a pipeline downstream of the Laval nozzle; characterized in that a microwave heating device is arranged at the Laval nozzle.

[0008] The microwave heating device comprises a microwave generator and a waveguide, wherein the microwave generator is used for generating high-frequency microwaves with a frequency close to a resonance frequency of water vapor; and the waveguide is used for conducting the high-frequency microwaves generated by the microwave generator to the Laval nozzle and heating the working steam at the Laval nozzle.

[0009] Spiral blades are arranged in the pipeline between the Laval nozzle and the mixing chamber, so as to promote mixing of the working steam and the ejecting steam and reduce condensation.

[0010] As a preferred scheme of the application, the ejector body is provided with an ejecting steam inlet at an upstream thereof and a mixed steam outlet at a downstream thereof; and the ejector body is further provided with a working steam inlet connected with the Laval nozzle.

[0011] As a preferred scheme of the application, the Laval nozzle is composed of a converging section, a throat section and a diverging section, which are sequentially connected, wherein the inlet of the converging section is the inlet of the Laval nozzle, and the outlet of the diverging section is the outlet of the Laval nozzle; a plurality of waveguides are uniformly distributed between the throat section of the Laval nozzle and the outlet of the Laval nozzle; the Laval nozzle accelerates expansion of the working steam, the pressure of the working steam is converted into kinetic energy, the working steam is accelerated to supersonic speed, and the pressure of the working steam at the outlet of the Laval nozzle is lower than the pressure of the ejecting steam.

[0012] As a preferred scheme of the application, the microwave generator comprises a transformer, a magnetron, a signal acquisition and transmission device and a control switch; the signal acquisition and transmission device acquires temperature and pressure data at different positions of the diverging section of the Laval nozzle; the control switch controls the working state and the output power of the magnetron through the transformer, and the magnetron is used for generating microwaves.

[0013] As a preferred scheme of the application, the microwave generator further comprises a monitoring system mainly composed of a computer and a signal transmission line; the monitoring system receives the temperature and pressure data at different positions of the diverging section of the Laval nozzle acquired by the signal acquisition and transmission device; and the monitoring system feeds back the acquired temperature and pressure data to the control switch to control the working state and the output power of the magnetron.

[0014] As a preferred scheme of the present application, the waveguide tube comprises a waveguide tube shell, a temperature probe, a pressure probe and a ceramic cover; the waveguide tube shell is connected with a magnetron of a microwave generator to conduct the microwave generated by the magnetron to a Laval nozzle; the temperature probe measures temperature data at a divergent section of the Laval nozzle; the pressure probe measures pressure data at the divergent section of the Laval nozzle; the temperature probe and the pressure probe are respectively connected with a signal acquisition and transmission device and are both fixed on the ceramic cover; the ceramic cover allows the microwave to penetrate into the divergent section of the Laval nozzle and isolates the waveguide tube from the Laval nozzle to prevent steam from entering the waveguide tube.

[0015] As a preferred scheme of the present application, the spiral blade is in the form of a fin arranged in the ejector body.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) The traditional steam ejector solves the internal condensation problem by increasing the superheat degree of the working steam, but a larger superheat degree generates a larger thermal stress, which has a larger requirement for the structural strength of the ejector and is difficult to meet the variable working conditions. In addition, some steam ejectors currently combine multiple ejectors, each of which is separately provided with a drainage mechanism to solve the problem of water accumulation in the ejector. However, there is a problem that the accumulated water cannot be drained in time. The present application adds a microwave heating device at the Laval nozzle, utilizes the characteristics of non-contact, rapid, high efficiency and precise control of microwave heating to heat the steam at the Laval nozzle, which can effectively reduce the condensation of steam at the nozzle throat and the divergent section to reduce the generation of condensed water.

[0018] (2) Through the action of the spiral blade in the mixing chamber, the working steam and the injected steam can be uniformly mixed, and the energy and mass exchange of the two streams of steam can be more sufficient, and the generation of condensation can be reduced.

[0019] (3) By opening a water guide groove at the rear half of the mixing chamber and the lower part of the diffuser chamber, the condensed water condensed in the ejector can be promptly drained away, avoiding the blockage of the condensed water in the ejector and the decline of the performance of the ejector.

[0020] (4) The monitoring system is used to monitor the temperature and pressure changes in the nozzle in real time, and the magnetron is controlled by a computer, which can be turned on as needed to avoid the waste of electric power caused by long-time opening of the microwave heating device. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is an overall structural view of the annular steam ejector with the anti-condensation microwave heating device.

[0022] Figure 2 It is a left view of the A-A cross section.

[0023] Figure 3 is a left view at the B-B section;

[0024] Figure 4 is a diagram of the microwave heating device;

[0025] Figure 5 is an enlarged view of the waveguide and the ejector shell connection at C;

[0026] Figure 6 is an enlarged view of the Laval nozzle and the waveguide connection at D.

[0027] Reference signs: 1 - microwave generator, 2 - waveguide, 3 - Laval nozzle, 4 - mixing chamber, 5 - diffuser, 6 - water channel, 7 - spiral blade, 8 - drain pipe, 9 - monitoring system, 10 - sealing device;

[0028] Transformer 1-1, magnetron 1-2, signal acquisition and transmission device 1-3, power plug 1-4, control switch 1-5, shell 1-6;

[0029] Waveguide shell 2-1, temperature probe 2-2, pressure probe 2-3, ceramic cover 2-4;

[0030] Laval nozzle tapered section 3-1, throat 3-2, diverging section 3-3;

[0031] Metallic sealing ring 10-1, two semicircular metallic covers 10-2 and clamps 10-3. DETAILED DESCRIPTION

[0032] The present application will be further described and illustrated in conjunction with the specific embodiments. The embodiments are only exemplary and do not define the scope of the disclosure. The technical features of the various embodiments of the present application can be combined as appropriate without conflict, provided that the combinations are not mutually exclusive. The present application uses the structure of an annular steam ejector to design, so as to add a microwave heating device to the ejector while minimizing the impact on the flow field in the pipe.

[0033] As shown in Figure 1 , one of the embodiments of the annular steam ejector with anti-condensation microwave heating device of the present application, which specifically comprises: an ejector body, a microwave generator 1, a waveguide 2, a Laval nozzle 3, a mixing chamber 4, a diffuser 5, a water channel 6, a spiral blade 7, a drain pipe 8, a monitoring system 9 and a sealing device 10.

[0034] The ejector body is provided with a Laval nozzle 3 for injecting working steam, and a mixing chamber 4 and a diffuser 5 are arranged on the pipeline downstream of the Laval nozzle 3; a microwave heating device is arranged at the Laval nozzle 3.

[0035] As shown in Figure 4 The microwave heating device includes a microwave generator 1 and a waveguide 2.

[0036] The microwave generator 1 includes a transformer 1-1, a magnetron 1-2, a signal acquisition and transmission device 1-3, a power plug 1-4, a control switch 1-5, and a shell 1-6.

[0037] The transformer 1-1 is used to convert the 380V AC power used in the factory into a direct current of about 4000V; the magnetron 1-2 is used to generate high-frequency microwaves close to the resonance frequency of water vapor; the signal acquisition and transmission device 1-3 is used to acquire temperature and pressure data at different positions of the Laval nozzle 3 and transmit them to the monitoring system 9; the power plug 1-4 is used to connect the power supply and is connected with the control switch 1-5; the control switch 1-5 can control the working state and the output power of the magnetron 1-2 at different positions according to the data fed back by the monitoring system 9; and the shell 1-6 is a support and protection device of the microwave generator 1.

[0038] The waveguide 2 includes a waveguide shell 2-1, a temperature probe 2-2, a pressure probe 2-3, and a ceramic cover 2-4.

[0039] The waveguide shell 2-1 is connected with the magnetron 1-2 of the microwave generator 1, and is used to conduct the microwaves generated by the magnetron 1-2 to the nozzle; there are five waveguides uniformly distributed from the throat position of the Laval nozzle 3 to the nozzle outlet; the temperature probe 2-2 is located at the right position in the waveguide 2, and is used to measure the temperature data at the divergent section of the Laval nozzle 3; the pressure probe 2-3 is located at the left position in the waveguide 2, and is used to measure the pressure data at the divergent section of the Laval nozzle 3; the temperature probe 2-2 and the pressure probe 2-3 are respectively connected with the signal acquisition and transmission device 1-3 and are both fixed on the ceramic cover 2-4; the ceramic cover 2-4 can make the microwaves penetrate into the divergent section of the Laval nozzle 3 and can isolate the waveguide 2 from the Laval nozzle 3 to prevent the steam from entering the waveguide 2.

[0040] The upstream of the ejector body is provided with an injection steam inlet, and the downstream is provided with a mixed steam outlet; the ejector body is also provided with a working steam inlet connected with the Laval nozzle 3.

[0041] The Laval nozzle 3 is composed of a convergent section, a throat, and a divergent section, so that the working steam is accelerated and expanded, the pressure energy of the steam is converted into kinetic energy and accelerated to supersonic speed, and the pressure of the steam at the nozzle outlet is lower than that of the injection steam, so as to entrain the low-pressure steam.

[0042] Spiral vanes 7 are arranged in the pipeline between the Laval nozzle 3 and the mixing chamber 4 to promote the mixing of working steam and ejecting steam and reduce the generation of condensate.

[0043] The spiral vanes 7 can not only promote the mixing of working steam and ejecting steam and make the energy and mass exchange of the two steam more sufficient, but also reduce the generation of condensate. The spiral vanes 7 used in the embodiment are in the form of in-pipe fins, which are located at a position about 500 mm from the outlet of the Laval nozzle 3, have a blade height of 15 mm, a thickness of 3 mm, a pitch of 150 mm and 8 turns.

[0044] The mixing chamber 4 is an equal-section mixing chamber for uniformly mixing supersonic working steam and the ejecting steam sucked.

[0045] The diffuser chamber 5 is a gradually expanding pipe section located downstream of the mixing chamber 4 for increasing the pressure of the mixed steam in the mixing chamber 4 and reducing the steam speed to reach the required steam state.

[0046] The water guide groove 6 is arranged on the pipe wall of the ejector body downstream of the spiral vanes 7. For example, in a preferred embodiment, the water guide groove 6 is arranged starting from the mixing chamber pipe wall 100 mm downstream of the spiral vanes 7 and passes through the diffuser chamber 5 to guide the condensate generated in the ejector to the low-speed low-pressure straight pipe section downstream of the diffuser chamber 5 and then discharged through the drain pipe 8 arranged on the low-speed low-pressure straight pipe section.

[0047] The drain pipe 8 is provided with a drain valve which can be opened at intervals to discharge the condensate generated in the ejector. In addition, due to the effect of the microwave heating device, less condensate is generated, and the drain valve can be opened at a longer interval.

[0048] The microwave generator 1 further comprises a monitoring system 9, and the microwave heating device further comprises a sealing device 10.

[0049] The monitoring system 9 mainly comprises a computer and a signal transmission line. The monitoring system 9 is connected with the signal acquisition and transmission device 1-3 of the microwave generator 1 and mainly used for monitoring the temperature and pressure data at different positions of the gradually expanding section of the Laval nozzle 3 in real time, comparing the temperature at different positions with the saturated temperature under the current pressure through the computer, and transmitting the signal to the control switch 1-5 to control the working state of the magnetron 1-2 at different positions and the size of the output power so as to avoid the waste of power resources.

[0050] As shown in Figure 1 The overall structure of the annular steam ejector with the anti-condensation microwave heating device is shown in Figure 1As shown, the leftmost inlet of the ejector is the inlet for ejector steam, the lower inlet is the inlet for working steam, and the rightmost outlet is the outlet for mixed steam.

[0051] like Figure 2 The left view at section AA is shown. At the position of the Laval nozzle 3 of the ejector, four sets of microwave heating devices are evenly distributed around its circumference, which can uniformly heat the water vapor in the nozzle. Temperature probe 2-2 and pressure probe 2-3 are arranged in each waveguide 2. There are 4 temperature and pressure data on each waveguide section. The average value is calculated to reduce the influence of gravity.

[0052] like Figure 3 The figure shows the left view at section BB. It can be seen from the figure that while ensuring the strength of the blade, the impact on the flow field is small. The width and thickness of the helical blade 7 should be reasonably selected.

[0053] like Figure 5 The image shown is a partially enlarged view of the connection between the waveguide 2 and the ejector housing at point C. It includes the sealing device 10, the waveguide 2, and the ejector housing.

[0054] The sealing device 10 includes a metal sealing ring 10-1, two semi-circular metal caps 10-2, and a clamp 10-3.

[0055] The metal sealing ring 10-1 is used to ensure the sealing of the waveguide 2; the semi-circular metal cap 10-2 is used to fix the metal sealing ring 10-1 and the waveguide 2; the clamp 10-3 is used to fasten the metal cap 10-2.

[0056] A gap of about 2 mm is left between the ejector housing and the waveguide 2, which allows the temperature probe 2-2 and the pressure probe 2-3 to be inserted for measurement, but without having a significant impact on the flow field.

[0057] like Figure 6 The image shown is a partial enlarged view of the connection between the Laval nozzle and the waveguide at point D. It includes the waveguide 2, the Laval nozzle 3, the ejector housing, and the sealing device 10.

[0058] The Laval nozzle 3 includes a tapering section 3-1, a throat 3-2, and a diffusing section 3-3.

[0059] Subsonic working steam enters through the converging section 3-1 of the Laval nozzle 3. As the cross-sectional area of ​​the flow channel continuously decreases, but the flow rate remains constant, the velocity increases, reaching the speed of sound at the throat 3-2 position. After reaching the speed of sound, the airflow at the diverging section 3-3 will continuously decrease in pressure and expand as the flow channel area increases, further accelerating to supersonic speed. It is then ejected from the outlet of the Laval nozzle 3.

[0060] The working method of the annular steam ejector with the anti-condensation microwave heating device can adopt the following steps:

[0061] The injection steam enters from the injection steam inlet upstream of the ejector body, and the working steam enters from the working steam inlet and is sprayed into the ejector body through the Laval nozzle 3;

[0062] The temperature probe 2-2 and the pressure probe 2-3 respectively measure the temperature data and the pressure data at the divergent section of the Laval nozzle 3 in real time, and transmit the data to the signal acquisition and transmission device 1-3; the monitoring system 9 monitors the temperature data and the pressure data in the signal acquisition and transmission device 1-3 in real time, compares the temperature at different positions with the saturated temperature under the current pressure through the computer, and then transmits the signal to the control switch 1-5 to control the working state of the magnetron 1-2 at different positions and the size of the output power; the microwave is generated by the magnetron 1-2 and conducted to the divergent section 3-3 of the Laval nozzle 3 through the waveguide shell 2-1;

[0063] The working steam at the Laval nozzle 3 is heated, the heated working steam is sprayed into the pipe through the Laval nozzle 3, and the injection steam is sucked in, then passes through the spiral blade 7 and the mixing chamber 4, is uniformly mixed, and the mixed steam is expanded and decelerated in the diffuser 5, and finally is output at the mixed steam outlet;

[0064] The water diversion groove 6 diverts the condensate water generated in the ejector to the low-speed and low-pressure straight pipe section behind the diffuser 5 of the ejector, and is discharged through the drain pipe 8.

[0065] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. For ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A ring-shaped steam ejector with anti-condensation microwave heating device, comprising an ejector body, on which a Laval nozzle (3) is arranged for injecting working steam, and a mixing chamber (4) and a diffuser chamber (5) are arranged on the pipeline downstream of the Laval nozzle (3); characterized in that, A microwave heating device is arranged at the Laval nozzle (3); The microwave heating device comprises a microwave generator (1) and a waveguide (2), wherein the microwave generator is used to generate high-frequency microwaves with a frequency close to the resonance frequency of water vapor; the waveguide is used to conduct the high-frequency microwaves generated by the microwave generator to the Laval nozzle (3) and heat the working steam at the Laval nozzle; the waveguide (2) comprises a waveguide shell (2-1), a temperature probe (2-2), a pressure probe (2-3) and a ceramic cover (2-4); the ceramic cover (2-4) allows microwaves to penetrate into the diverging section of the Laval nozzle (3) and isolates the waveguide (2) from the Laval nozzle (3), preventing steam from entering the waveguide (2); the temperature probe (2-2) measures the temperature data at the diverging section of the Laval nozzle (3); the pressure probe (2-3) measures the pressure data at the diverging section of the Laval nozzle (3); the temperature probe (2-2) and the pressure probe (2-3) are connected to a signal acquisition and transmission device (1-3) and are both fixed on the ceramic cover (2-4). A spiral blade (7) is arranged in the pipeline between the Laval nozzle (3) and the mixing chamber (4) to promote the mixing of working steam and injected steam and reduce the generation of condensate; the spiral blade (7) is in the form of a fin arranged in the ejector body; a water guide groove (6) is arranged on the wall of the ejector body downstream of the spiral blade (7); the water guide groove (6) guides the condensate generated in the ejector to the low-speed low-pressure straight pipe section downstream of the diffuser chamber (5) and is discharged through the drain pipe (8) arranged on the low-speed low-pressure straight pipe section; a drain valve is installed on the drain pipe (8) to intermittently open and discharge the condensate generated in the ejector; The microwave generator comprises a transformer (1-1), a magnetron (1-2), a signal acquisition and transmission device (1-3) and a control switch (1-5); the signal acquisition and transmission device (1-3) acquires temperature and pressure data at different positions of the diverging section of the Laval nozzle (3); the control switch (1-5) controls the working state and output power of the magnetron (1-2) through the transformer (1-1), and the magnetron (1-2) is used to generate microwaves; The microwave generator further comprises a monitoring system (9) mainly composed of a computer and a signal transmission line; the monitoring system (9) receives the temperature and pressure data at different positions of the diverging section of the Laval nozzle (3) acquired by the signal acquisition and transmission device (1-3); and feeds back the acquired temperature and pressure data to the control switch (1-5) to control the working state and output power of the magnetron (1-2).

2. The annular vapor ejector with anti-condensation microwave heating device according to claim 1, characterized in that, The upstream of the ejector body is provided with an injected steam inlet, and the downstream is provided with a mixed steam outlet; the ejector body is further provided with a working steam inlet connected with the Laval nozzle (3).

3. The annular vapor ejector with anti-condensation microwave heating device according to claim 1, characterized in that, The Laval nozzle (3) is composed of a converging section, a throat section and a diverging section, which are connected in sequence, wherein the inlet of the converging section is the inlet of the Laval nozzle, and the outlet of the diverging section is the outlet of the Laval nozzle; a plurality of waveguide tubes are evenly distributed between the throat section of the Laval nozzle (3) and the outlet of the Laval nozzle. The Laval nozzle (3) accelerates the working steam to expand, the pressure of the working steam can be converted into kinetic energy, and the working steam is accelerated to supersonic speed, and the pressure of the working steam at the outlet of the Laval nozzle is lower than the pressure of the ejector steam.

4. The annular vapor ejector with anti-condensation microwave heating device according to claim 1, characterized in that, The waveguide tube shell (2-1) is connected with the magnetron (1-2) of the microwave generator (1), and the microwave generated by the magnetron (1-2) is conducted to the Laval nozzle.

5. The annular vapor ejector with anti-condensation microwave heating device according to claim 1, characterized in that, The microwave heating device further comprises a sealing device (10), which comprises a metal sealing ring (10-1), two semicircular metal covers (10-2) and a clamp (10-3); the metal sealing ring (10-1) is used to ensure the sealing of the waveguide tube (2); the semicircular metal cover (10-2) fixes the metal sealing ring (10-1) and the waveguide tube (2); and the clamp (10-3) fastens the metal cover (10-2).

6. A method of operating the annular vapor ejector with anti-condensation microwave heating device of claim 4, wherein, The working method comprises the following steps: The ejector steam enters from the ejector steam inlet upstream of the ejector body, and the working steam enters from the working steam inlet and is injected into the ejector body through the Laval nozzle (3); The temperature probe (2-2) and the pressure probe (2-3) measure the temperature data and the pressure data at the diverging section of the Laval nozzle (3) in real time, and transmit the data to the signal acquisition and transmission device (1-3); the monitoring system (9) monitors the temperature data and the pressure data in the signal acquisition and transmission device (1-3) in real time, compares the temperature at different positions with the saturation temperature under the current pressure, and then transmits the signal to the control switch (1-5) to control the working state of the magnetron (1-2) at different positions and the size of the output power; the microwave is generated by the magnetron (1-2) and conducted to the diverging section (3-3) of the Laval nozzle (3) through the waveguide tube shell (2-1); The working steam at the Laval nozzle (3) is heated, the heated working steam is injected into the pipe through the Laval nozzle (3), and the ejector steam is sucked in, then passes through the spiral blade (7) and the mixing chamber (4), is uniformly mixed, and the mixed steam is expanded, decelerated and output in the diffuser (5). The water guide groove (6) guides the condensed water generated in the ejector to the low-speed and low-pressure straight pipe section behind the diffuser (5) of the ejector, and is discharged through the drain pipe (8).

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