Variable frequency pulse detonation ash cleaning device with self-adaptive pressure relief function

Abstract

The application discloses a variable-frequency pulse detonation ash cleaning device with a self-adaptive pressure relief function, and belongs to the cleaning field.The variable-frequency pulse detonation ash cleaning device comprises a two-stage self-adaptive pressure relief device and a detonation ash cleaning structure; the airflow converging tube, the self-adaptive return spring, the thrust roller bearing, the two-stage pressure relief main body and the two-stage pressure relief shell are sequentially positioned and connected along the axial direction of the main flow channel; the detonation ash cleaning structure comprises a one-stage pressure relief section, a mixing section, an ignition section and a detonation chamber provided with a Shchelkin spiral which are in communication; the oxidant is branched by the two-stage self-adaptive pressure relief device, mixed with the fuel at the equal-diameter throat of the mixing inner cylinder, and the explosive mixed gas is generated; under the regulation of the ignition system, simultaneous and time-sharing ignition is realized to form the deflagration flame, the stable self-sustaining detonation wave is obtained by the Shchelkin spiral, and the ash is cleaned by the detonation wave; the high-temperature and high-pressure gas generated by the detonation is returned to the upstream, a part of the gas is released through the one-stage pressure relief section, the remaining gas is collected into the two-stage self-adaptive pressure relief device and drives the main body to perform spiral ascending movement, the high-pressure gas is discharged when the gas discharge channel of the two-stage pressure relief main body and the two-stage pressure relief shell is coincident, the flow relief is realized, and the influence of the detonation back transmission on the normal working of the ash cleaning device is reduced.

Description

A variable frequency pulse detonation cleaning device with adaptive pressure relief function Technical Field

[0001] This invention belongs to the field of cleaning, specifically relating to a variable frequency pulse detonation cleaning device with adaptive pressure relief function. Background Technology

[0002] During boiler operation, the complex composition of the fuel produced generates a large amount of fly ash. The ash molecules interact with the heat exchange surfaces and between ash molecules through various forces, including surface tension, viscosity, molecular adhesion, electrostatic attraction, and chemical forces. This causes the fly ash to accumulate and coke on the heat exchange surfaces of the furnace, flue, superheater, and economizer as it flows with the flue gas. Since the thermal resistance of ash is 400 to 1000 times that of metal, after a period of boiler operation, the wall heat exchange capacity decreases by 30% to 60%, and the flue gas temperature rises, significantly reducing thermal efficiency (studies show that for every 15-20°C increase in boiler flue gas temperature, boiler thermal efficiency decreases by 1%). Furthermore, uneven ash distribution leads to uneven heating of the ash-accumulating parts, easily causing localized hot spots and thermal corrosion, which can result in tube rupture and severe economic losses. The problems caused by ash accumulation and coking, such as high-temperature corrosion, flue blockage, and tube rupture, prevent boilers from operating stably for a long time. They need to be shut down for a week every three months for maintenance and ash cleaning. Therefore, the research and development of boiler ash cleaning technology and even online ash cleaning technology is of great significance.

[0003] To address the problems of ash accumulation and coking in combustion products, various methods have been sought. Current ash removal devices mainly include mechanical vibrators, steam soot blowers, acoustic soot blowers, and gas shockwave soot blowers. Mechanical vibrators involve manually or mechanically striking the ash-accumulating surface of the boiler to detach the ash from the wall. However, they have significant drawbacks: firstly, they damage the surface of the ash-accumulating components, reducing their service life; secondly, they are ineffective at removing sticky ash and coking. Steam soot blowers, like mechanical vibrators, are an early ash removal technology. Their principle is to use high-temperature, high-pressure superheated steam, accelerated through a venturi tube to form high-speed steam, which then blows away ash from the heated surface. High-temperature steam effectively solves the problem of sticky ash accumulation, but its cleaning effect drops sharply when it encounters obstacles, creating cleaning dead zones, such as better cleaning of the windward side of the heat exchanger tube bundle than the leeward side. Acoustic soot blowers, on the other hand, have the advantage of sound waves having good refraction, diffraction, and superposition characteristics, allowing for effective removal of ash from any direction on the ash-accumulating components, with no dead zones in the working area. They utilize sound energy to clean the ash-accumulating components. Repeated action of the ash layer causes it to fall off when it reaches its fatigue limit. However, sonic soot blowers are only suitable for loose ash and are not effective for coking or sticky ash. Furthermore, the single-frequency sonic wave creates a weak sound field due to multiple reflections, resulting in a weak ash removal zone. Gas shock wave soot blowers, developed by the Institute of Mechanics of the Chinese Academy of Sciences in the 1990s, utilize the strong kinetic, thermal, and acoustic energy generated by the deflagration or explosion of hydrocarbon fuels for ash removal. However, the high-temperature jet has a very short time after exiting the device, resulting in a weak effect on the thermal stress of the ash. In addition, traditional gas shock wave soot blowers have a long single working cycle time, while explosions are instantaneous, and the acoustic fatigue effect similar to that of sonic soot blowers does not exist. Furthermore, unreasonable structural design can lead to poor ash removal effect and low space utilization of some equipment (such as the shock wave generator).

[0004] The pulse detonation soot blowing device is developed from the traditional gas shock wave soot blower, but the shock wave generation principle is completely different. It adopts a detonation (detonation) combustion mode. After the detonation wave is transmitted from the detonation soot blowing device, it is decoupled, generating a detonation shock wave and a high-temperature and high-pressure detonation gas jet. The detonation shock wave applies a strong force of compression followed by tension on the ash accumulation surface, causing the ash layer to break and detach due to kinetic energy impact. The refracted pressure wave is continuously reflected and transmitted within the ash accumulation layer, generating transverse shear stress at the junction of the ash layer base and wall, accelerating the ash layer fracture and detachment. The high-temperature, high-pressure, high-speed gas jet ejected after the detonation shock wave also acts on the ash coking surface. Under the action of thermal stress, the bonding strength and fatigue strength decrease, and the ash breaks and falls off under the action of the gas jet with the same high kinetic energy. At the same time, the strong sound waves generated by the propagation of the detonation shock wave, the attenuation of the shock wave propagation, and the injection of the hot jet (turbulence noise) also have a superior soot blowing effect.

[0005] Different types of ash accumulation equipment, or even different types of ash accumulation within the same equipment, often require detonation shock waves of varying intensities and gas jets of varying temperatures. Therefore, effectively mitigating the shortcomings of traditional ash removal technologies and achieving "on-demand ash removal" is a pressing issue. Furthermore, due to the unique self-pressurizing combustion characteristics of detonation, the gas pressure is significantly higher than the incoming flow pressure. After each combustion cycle, a large amount of high-temperature, high-pressure gas flows back into the oxidizer supply pipeline, severely hindering the filling of fuel and oxidizer in the next working cycle, increasing the single-cycle working time, and consequently reducing the operating frequency of the detonation combustion chamber and lowering ash removal efficiency. Summary of the Invention

[0006] The technical problem to be solved: In order to effectively avoid the shortcomings of traditional detonation cleaning technology and solve the problem of gas backflow during high-frequency operation of detonation cleaning devices, this invention provides a variable frequency pulse detonation cleaning device with adaptive pressure relief function. The frequency adjustment design of the detonation chambers in the device can work simultaneously or in shifts, which effectively solves the shortcomings of previous detonation cleaning technologies, such as the weak sound field of acoustic soot blowers and the long single working cycle time of traditional gas shock wave soot blowers. The multi-stage adaptive pressure relief device solves the problem that gas backflow causes the detonation cleaning device to work at a low frequency and the detonation cleaning effect to be poor.

[0007] The technical solution of this invention is: a variable frequency pulse detonation cleaning device with adaptive pressure relief function, comprising a two-stage adaptive pressure relief device and a detonation cleaning structure; the two-stage adaptive pressure relief device includes a main flow channel, an airflow convergence tube, an adaptive return spring, a thrust roller bearing, a two-stage pressure relief body, and a two-stage pressure relief shell; the detonation cleaning structure includes a primary pressure relief section, a mixing section, an ignition section, and a detonation chamber with a Shchelkin spiral, all connected in series; several adaptive return springs are circumferentially distributed on the outer protrusion of the main flow channel, and the thrust roller bearing and the two-stage pressure relief body are connected downstream in sequence; the two-stage pressure relief body and the two-stage pressure relief shell have multiple venting channels of the same size, and the two are connected by spiral ribs and spiral grooves; the mixing section includes a mixing inner cylinder and a mixing outer cylinder;

[0008] A further technical solution of the present invention is: the adaptive return springs are evenly distributed in multiple circumferentially according to the required return spring force;

[0009] A further technical solution of the present invention is: the adaptive return spring and the secondary pressure relief body are axially positioned and connected by a thrust roller bearing;

[0010] A further technical solution of the present invention is: the adaptive return spring has a long and short outer wall structure, and the axial length of the long and short outer walls when closed is equal to the movement distance of the secondary pressure relief body from rest to the upper dead point;

[0011] A further technical solution of the present invention is: the secondary pressure relief body and the secondary pressure relief shell are provided with 4 to 8 venting channels of the same size and number; the spiral rib on the outer wall of the secondary pressure relief body is a spiral column structure; during the process of rising along the spiral groove on the inner wall of the secondary pressure relief shell, the secondary pressure relief body can be designed to rotate 45° to 90° depending on the number of venting channels.

[0012] A further technical solution of the present invention is that the outlet radius of the airflow convergence tube is 0.3 to 0.5 times the radius of the main flow channel;

[0013] A further technical solution of the present invention is: the first-stage pressure relief section includes an inner bend pipe structure, the central axis of the inner bend pipe structure coincides with the central axis of the detonation cleaning structure, and the central axis of the outer pipe of the pressure relief section forms a 90° to 150° angle with the central axis of the detonation cleaning structure.

[0014] A further technical solution of the present invention is: the inner bend structure of the first-stage pressure relief section is an expansion structure, and the maximum expansion area is less than 40% of the cross-sectional area of ​​the detonation tube;

[0015] A further technical solution of the present invention is: the inner wall of the mixing inner cylinder is a shrinkage-equal diameter-expansion structure, and 4 to 8 gas inlets of 0.8 to 2 mm are opened on the equal diameter throat channel, and the outer wall corresponding to the equal diameter throat is a spiral groove type fuel storage structure.

[0016] A further technical solution of the present invention is that the secondary adaptive pressure relief device can connect to 3 to 6 circumferentially arranged detonation cleaning structures, which can work simultaneously or at different times. Beneficial effects

[0017] The beneficial effects of this invention are as follows: it effectively avoids the damage to the ash accumulation device caused by mechanical vibrators, the dead zone in steam soot blowers, the poor ability of sonic soot blowers to remove sticky ash, and the long single working cycle time of traditional gas shock wave soot blowers; the multi-tube parallel design effectively solves the problem of excessively large shock wave generator volume and low space utilization in traditional gas shock wave soot blowers, with the volume occupied by 2 to 6 detonation chambers arranged circumferentially being the same as the volume of the shock wave generator in one traditional gas shock wave soot blower; for different ash removal needs, multiple detonation chambers of the pulse detonation ash removal device can work simultaneously and at different times in the same working cycle, such as a single tube working at 20Hz, and a three-tube combination with a maximum working frequency of 60Hz. The arrangement and combination of the working sequence of multiple detonation chambers can achieve effective ash removal without making the device redundant and wasting too many resources; the multi-stage adaptive pressure relief structure effectively solves the problem that the detonation ash removal device has a low working frequency and poor ash removal effect due to the backflow of high-temperature and high-pressure gas.

[0018] The high-temperature, high-pressure backflow gas generated by the single-detonation ash removal structure releases a portion of the backflow gas after passing through the first-stage pressure relief section, reducing backflow pressure. The remaining backflow gas merges into the second-stage adaptive pressure relief device. The high-pressure gas after 90% merging pushes the second-stage pressure relief body to move along the spiral groove on the second-stage pressure relief shell. The outer wall structure of the adaptive return spring determines the upper dead point of the movement of the second-stage pressure relief body. When the second-stage pressure relief body moves to the upper dead point, it completely overlaps with the gas release channel on the second-stage pressure relief shell, achieving the purpose of flow reduction and pressure relief, and reducing the impact of detonation backflow on the normal operation of the ash removal device. When the gas pressure is less than the return spring force, the secondary pressure relief body returns along the original path, the gas release channel is closed, and the next cycle oxidant passes through the main channel and the gas flow convergence pipe in sequence, and then enters the detonation cleaning structure directly or after diversion. The fuel passes through the spiral groove-type fuel storage structure at the throat of the mixing inner cylinder and the fuel inlet hole and is mixed with the oxidant in the equal diameter throat channel. Then the explosive mixture is ignited in the ignition section to form deflagration. A stable self-sustaining detonation wave is obtained by the Shchelkin spiral explosion aid, and the detonation wave is used for cleaning. Attached Figure Description

[0019] Figure 1: Cross-sectional view of an embodiment of the present invention;

[0020] Figure 2: A quarter-section view of the main channel, airflow convergence tube, adaptive return spring, thrust roller bearing and secondary pressure relief body assembly of the present invention;

[0021] Figure 3: Quarter cross-sectional view of the secondary pressure relief casing of the present invention;

[0022] Figure 4: Cross-sectional view of the first-stage pressure relief section of the present invention;

[0023] Figure 5: A quarter-section view of the blending inner cylinder of the present invention;

[0024] Figure 6: Structural diagram of an embodiment of the present invention

[0025] Explanation of reference numerals in the attached drawings: 1—Secondary adaptive pressure relief device, 2—Detonation cleaning structure, 3—Adaptive return spring, 4—Thrust roller bearing, 5—Secondary pressure relief main body, 6—Secondary pressure relief outer shell, 7—Primary pressure relief section, 8—Mixing section, 9—Ignition section, 10—Detonation chamber, 11—Mixing inner cylinder, 12—Mixing outer cylinder, 13—Airflow convergence pipe. Detailed Implementation

[0026] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0027] Please refer to Figure 1. The multi-tube pulse detonation cleaning device with adaptive pressure relief function of the present invention includes a two-stage adaptive pressure relief device 1 and a detonation cleaning structure 2. The two-stage adaptive pressure relief device 1 includes a main flow channel, an adaptive return spring 3, a thrust roller bearing 4, a two-stage pressure relief body 5, a two-stage pressure relief shell 6, and an airflow convergence tube 13. The detonation cleaning structure 2 includes a primary pressure relief section 7, a mixing section 8, an ignition section 9, and a detonation chamber 10 with a Shchelkin spiral, all connected in series. The mixing section 8 includes a mixing inner cylinder 11 and a mixing outer cylinder 12.

[0028] Please refer to Figures 2 and 3. Eight circumferentially distributed adaptive return springs 3 are installed under the outer protrusion of the main channel, and are axially positioned and connected to the secondary pressure relief body 5 through thrust roller bearings 4. The downstream secondary pressure relief body 5 and the secondary pressure relief shell 6 are connected by spiral ribs and spiral grooves, and both have six venting channels of the same size. When the secondary pressure relief body 5 is working, after spiraling up 60°, its upper venting channel completely overlaps with the upper venting channel of the secondary pressure relief shell 6, and the long and short outer walls of the adaptive return springs 3 close, so that it reaches the upper dead point of the movement. The airflow convergence tube 13 with an outlet radius of 0.4 times the radius of the main channel is fixed to the tail end of the main channel by threads.

[0029] Please refer to Figure 4. The first-stage pressure relief section 7 contains an inner bend pipe structure. The central axis of the inner bend pipe structure coincides with the central axis of the detonation cleaning structure. The central axis of the outer pipe of the pressure relief section forms a 90° angle with the central axis of the detonation cleaning structure. In order to effectively reduce the total backflow pressure in a short time, the inner bend pipe structure is an expansion structure to increase the venting flow rate.

[0030] Please refer to Figure 5. The inner wall of the mixing inner cylinder 11 has a shrinkage-equal diameter-expansion structure. There are 6 1 mm gas inlet holes on the equal diameter throat channel. The outer wall corresponding to the equal diameter throat has a spiral groove type fuel storage structure.

[0031] Please refer to Figure 6. The secondary pressure relief device 1 connects three circumferentially arranged detonation cleaning structures 2 to form a complete three-tube pulse detonation cleaning device. The high-temperature and high-pressure backflow gas generated by the operation of a single detonation cleaning structure 2 releases part of the backflow gas after passing through the primary pressure relief section 7, reducing the backflow pressure. The remaining backflow gas merges into the secondary adaptive pressure relief device. The high-pressure gas after 90% merging pushes the secondary pressure relief body 5 to move along the spiral groove on the secondary pressure relief shell 6. The outer wall structure of the adaptive return spring 3 determines the upper dead point of the movement of the secondary pressure relief body 5. When the secondary pressure relief body 5 moves to the upper dead point and completely overlaps with the gas release channel on the secondary pressure relief shell 6, the purpose of flow reduction and pressure relief is achieved, reducing the impact of detonation backflow on the normal operation of the cleaning device. When the gas pressure is less than the return spring force, the secondary pressure relief body 5 returns along the original path, the gas release channel is closed, and the next cycle oxidant passes through the main channel and the gas flow convergence pipe in sequence, and then enters the detonation cleaning structure 2 directly or after diversion. The fuel passes through the inverted trapezoidal groove at the throat of the mixing inner cylinder 11 and the fuel inlet hole in sequence and is mixed with the oxidant in the equal diameter throat channel. Then the explosive mixture is ignited in the ignition section 9 to form deflagration. A stable self-sustaining detonation wave is obtained by the Shchelkin spiral explosion aid, and the detonation wave is used for cleaning.

[0032] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A variable frequency pulse detonation cleaning device with adaptive pressure relief function, characterized in that, The system includes a two-stage adaptive pressure relief device and a detonation cleaning structure. The two-stage adaptive pressure relief device includes a main flow channel, adaptive return springs, thrust roller bearings, a two-stage pressure relief body, a two-stage pressure relief shell, and an airflow convergence tube. The detonation cleaning structure includes a primary pressure relief section, a mixing section, an ignition section, and a detonation chamber with a Shchelkin spiral, all connected in series. Several adaptive return springs are circumferentially distributed on the outer protrusion of the main flow channel, and the thrust roller bearing and the two-stage pressure relief body are connected downstream of each other. The two-stage pressure relief body and the two-stage pressure relief shell have multiple venting channels of the same size, and the two are connected by spiral ribs and spiral grooves. The mixing section includes a mixing inner cylinder and a mixing outer cylinder.

2. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, Multiple adaptive return springs are evenly distributed circumferentially according to the required adaptive return spring force magnitude.

3. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The adaptive return spring and the secondary pressure relief body are axially positioned and connected along the main channel via thrust roller bearings.

4. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The adaptive return spring has a structure with long and short outer walls. When the long and short outer walls are closed, the axial length is equal to the distance the secondary pressure relief body moves from rest to the top dead center.

5. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The secondary pressure relief body and the secondary pressure relief shell have 4 to 8 venting channels of the same size and number. The spiral ribs on the outer wall of the secondary pressure relief body are spiral column structures. During the process of rising along the spiral groove on the inner wall of the secondary pressure relief shell, the secondary pressure relief body can be designed to rotate 45° to 90° depending on the number of venting channels.

6. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The outlet radius of the airflow convergence tube is 0.3 to 0.5 times the radius of the main flow channel.

7. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The first-stage pressure relief section includes an inner bend pipe structure, the central axis of which coincides with the central axis of the detonation cleaning structure, and the central axis of the outer pipe of the first-stage pressure relief section forms an angle of 90° to 150° with the central axis of the detonation cleaning structure.

8. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 7, characterized in that, The inner bend of the first-stage pressure relief section is an expansion structure, with the maximum expansion area being less than 40% of the cross-sectional area of ​​the detonation chamber.

9. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The inner wall of the mixing inner cylinder has a contraction-equal diameter-expansion structure, with 4 to 8 gas inlets of 0.8 to 2 mm in diameter on the equal diameter throat channel, and the outer wall corresponding to the equal diameter throat has a spiral groove type fuel storage structure.

10. The variable frequency pulse detonation cleaning device with adaptive pressure relief function according to claim 1, characterized in that, The secondary adaptive pressure relief device can connect to 3 to 6 circumferentially arranged detonation cleaning structures, enabling time-sharing or simultaneous ignition.

Images