Direct Mixing Heat Exchanger

Abstract

A direct mixing heat exchanger is a supporting equipment for a burner, and has an air barrier between its inner and outer tubes; the two ends of the outer tube are sealed and fixedly connected to the two ends of the inner tube along the circumference, and the outer tube is provided with an inlet pipe connected to the air barrier; a first fire inlet hole is provided at the front end of the inner tube, and a heat mixing outlet is provided at the rear end of the inner tube; the internal space section at the front end of the inner tube is set as a preheating chamber, and the remaining internal space section at the rear end of the inner tube is set as a mixing chamber, and a plurality of nozzles are provided on the inner tube wall located in the mixing chamber, each nozzle having a nozzle at one end, and the other end of each nozzle being connected to the air barrier; this device has the significant advantage of replacing a traditional hot water boiler or a hot air furnace, and has the advantages of small size, simple structure, low cost and high thermal efficiency.

Description

Technical Field

[0001] The invention relates to a heat exchange device suitable for use with a combustion engine, in particular to a direct mixing heat exchanger. Background Art

[0002] Traditional hot water boilers or hot air furnaces mostly send water or air through pipes into the furnace. The heat source in the furnace indirectly exchanges heat energy with the water or air in the pipe by heating the pipe wall. In order to improve the heat exchange efficiency of the boiler, the method of increasing the surface area of ​​the pipe is usually adopted to increase the heat exchange surface area between the heat source and the pipe. For example, the tube structure often used in the boiler increases the contact area with the heat source by increasing the number of pipes, so as to better absorb heat energy and avoid heat loss. Some boilers also use a maze structure to improve their heat exchange efficiency. The above means make the internal structure of the traditional hot water boiler or hot air furnace gradually complicated, resulting in a large size of the boiler. The manufacturing process is complex, the material consumption is high, the manufacturing cost is high and the maintenance and repair are difficult. With the gradual improvement of people's environmental awareness, low-carbon, environmentally friendly and clean exhaust smoke burners are gradually becoming popular. Many traditional hot water boilers or hot air furnaces have also begun to use burners as heat sources. However, since the flame of the burner is ejected at high speed in a straight line when it is working, it does not match the airflow characteristics of the internal structure of the traditional boiler well. It is usually necessary to optimize the internal structure of the boiler to extend the residence time of the flame heat in the furnace and make full use of the calorific value. This not only increases the cost of the transformation, but also does not significantly improve the heat exchange effect. Therefore, there is an urgent need for a heat exchange device suitable for the burner. Summary of the invention

[0003] The object of the present invention is to provide a direct mixing heat exchanger, which is suitable for use with a burner to replace a traditional hot water boiler or a hot air furnace. Compared with a traditional hot water boiler or a hot air furnace, the heat exchange device also has the advantages of small size, simple structure, low cost and high heat exchange efficiency.

[0004] The technical solution of the present invention is: a direct mixing heat exchanger, characterized in that: it has an inner tube and an outer tube that are connected in a sleeve, and an air barrier is provided between the inner and outer tubes; the two ends of the outer tube are sealed and fixedly connected to the two ends of the inner tube along the circumference, and the outer tube is provided with an inlet pipe connected to the air barrier; the front end of the inner tube is provided with a first fire inlet hole, the rear end of the inner tube is provided with a heat mixing outlet, the internal space section at the front end of the inner tube is set as a preheating chamber, and the remaining internal space section at the rear end of the inner tube is set as a mixing chamber, and a plurality of nozzles are provided on the inner tube wall located in the mixing chamber, each nozzle is provided with a nozzle at one end, and the other end of each nozzle is connected to the described air barrier.

[0005] The length of the preheating chamber is 1 / 5 to 1 / 3 of the length of the inner tube.

[0006] The spray direction of all or part of the nozzles is perpendicular to the axis of the inner tube.

[0007] The spraying direction of all or part of the nozzles is inclined toward the rear end of the inner tube.

[0008] The nozzle is a flat nozzle.

[0009] The pipe opening at the outlet end of the inlet pipe is located on the outer pipe wall at the junction of the preheating chamber and the mixing chamber.

[0010] The water inlet direction of the inlet pipe is inclined toward the rear end of the inner pipe.

[0011] A water-assisted combustion device for the burner is installed at the front end of the inner tube. The device has a water supply tank and a fire tube. A thermal insulation layer is provided on the inner wall of the fire tube, and a heat insulation layer is provided on the surface of the thermal insulation layer. A second fire inlet hole is provided at the front end of the fire tube, and a flame spray hole is provided at the rear end of the fire tube. The flame spray hole is opposite to the first fire inlet hole at the front end of the inner tube. A steam generating pipe and a steam distillation pipe are provided in the fire tube. The steam generating pipe is placed on the periphery of the steam distillation pipe, and a fire gap is provided between the steam generating pipe and the steam distillation pipe. The water inlet at the front end of the steam generating pipe is connected with the water supply tank, and the air outlet at the rear end of the steam generating pipe is connected with the air inlet at the rear end of the steam distillation pipe. A combustion-assisted nozzle located at the center of the fire tube is provided at the front end of the steam distillation pipe, and a plurality of heat collecting fins are provided in the steam distillation pipe at the combustion-assisted nozzle.

[0012] The working principle and advantages of the present invention are as follows: the device makes full use of the environmental protection performance and working characteristics of the burner, and places the flame nozzle of the burner opposite to the first fire inlet hole of the inner tube, so that the flame ejected by the burner is ejected and burned in the inner tube through the first fire inlet hole, and the pressurized water or wind is sent into the air-insulating layer. The flame ejected by the burner first heats the tube wall of the preheating cavity section of the inner tube, thereby preheating the water or wind in the air-insulating layer; at the same time, the low-temperature water or low-temperature air flowing in the air-insulating layer also has the comprehensive advantages of cooling and insulating the inner tube, which minimizes the loss of calorific value and significantly prolongs the service life of the inner tube. Normal use can achieve the significant advantage of lifetime maintenance-free of the tube body;

[0013] When used to replace traditional hot water boilers: the pressurized water in the air barrier is scattered and sprayed into the mixing chamber through each nozzle to form a curtain of water mist, and the flame sprayed from the burner at high speed is in direct contact with the suspended water droplets, so that the water droplets are directly wrapped by the high temperature of the flame for heat exchange, and the high-speed flame sprayed continuously blows the water droplets away to form smaller water droplets, thereby geometrically expanding the heat exchange area between the water droplets and the flame, and the heat exchange effect is extremely significant. At the same time, the multi-layer water curtain formed by the spraying of each nozzle has a retention resistance to the flame jet of the burner, which can effectively slow down the flame so that its heat energy can be fully exchanged with water, and the heated water is provided to the heat-using equipment through the mixed heat outlet; the water temperature can be conveniently controlled by adjusting the working condition of the burner or the water supply flow rate.

[0014] When used to replace the traditional hot air furnace: the pressure wind in the insulation layer is scattered and sprayed into the mixing chamber through each nozzle, and the pressure wind is cross-mixed with the flame to form turbulence, so that the flame heat energy and the pressure wind can be fully and evenly mixed in the mixing chamber, and the obtained hot air can be directly sent to the heat-using equipment for use through the mixing heat outlet, and the temperature of the hot air can be conveniently controlled by adjusting the working condition of the burner or the air supply flow rate.

[0015] In summary, the device of the present application has the significant advantages of replacing traditional hot water boilers and hot air furnaces, has strong versatility, fully utilizes the working characteristics of the burner, and replaces hot water boilers and hot air furnaces of different structures. Its main structure only has an inner tube and an outer tube. Compared with boilers of traditional structures, the device of the present application has the advantages of small size, simple structure, low cost and high heat exchange efficiency.

[0016] Through experimental calculation, the length ratio size limit of the preheating chamber and the mixing chamber is more conducive to improving the heat exchange efficiency of the device of the present application, and is used for commercial protection. The nozzle heel that is vertical or inclined toward the rear end of the inner tube is conducive to mixing and blending water or wind with the flame heat source. In the technical scheme provided with a water combustion-supporting device, the flame nozzle of the burner is opposite to the second fire inlet hole at the front end of the fire tube. After the flame is assisted by this device, it enters the first fire inlet hole at the front end of the inner tube and is transmitted backward. The water combustion-supporting device can increase the flame calorific value of the burner, and the tail smoke after combustion is colorless and odorless, with significant energy-saving and environmental protection effects.

[0017] The flat nozzle can spray out a fan-shaped water curtain or wind curtain, which contacts the flame head-on to further improve the heat exchange efficiency. The inlet pipe located at the junction of the preheating chamber and the mixing chamber can not only ensure the spraying pressure of each nozzle, but also send low-temperature water or wind into the air-insulating layer of the preheating chamber section. After the water or wind in the air-insulating layer is heated, it will flow upward and backward rapidly to form a virtuous cycle. Spraying water and wind obliquely into the air-insulating layer through the inlet pipe can form a vortex along the inner and outer pipe walls, reducing water inlet resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the longitudinal axial section structure of the direct mixing heat exchanger of the present invention.

[0019] Figure 2 This is a schematic diagram of the longitudinal section of the direct mixing heat exchanger of the present invention.

[0020] Figure 3 It is a schematic diagram of the application state of the direct mixing heat exchanger of the present invention.

[0021] Figure 4 It is a schematic diagram of another application state of the direct mixing heat exchanger of the present invention.

[0022] In the figure, 1 is an outer tube, 2 is an inner tube, 3 is an air-insulating layer, 4 is an inlet pipe, 5 is a nozzle, 6 is a nozzle, 7 is a first fire inlet hole, 8 is a heat mixing outlet, 9 is a mounting flange, 10 is a jet direction, 11 is an inner tube axis, 12 is a mixing chamber, 13 is a preheating chamber, 14 is a burner, 15 is a flame nozzle, 16 is a water storage tank, 17 is a water inlet pipe, 18 is a water distributor, 19 is a circulating pipe, 20 is a circulating pump, 21 is a water pump, 22 is a heat-using equipment, 23 is a second fire inlet hole, 24 is a front end water inlet of a steam generation pipeline, 25 is a water supply tank outlet pipe, 26 is a flow valve, 27 is a water supply tank, 28 is a heat-insulating layer, 29 is a heat-insulating layer, 30 is a steam generation pipeline, 31 is a steam dry distillation pipeline, 32 is a fire tube, 33 is a fire gap, 34 is a combustion-supporting nozzle, 35 is a flame nozzle, and 36 is a heat-collecting fin. DETAILED DESCRIPTION

[0023] Direct mixing heat exchanger, such as Figure 1 and Figure 2 As shown, it comprises an inner tube 2 and an outer tube 1 which are sleeved together, and an air barrier 3 is provided between the inner and outer tubes; two ends of the outer tube are sealed and fixedly connected to two ends of the inner tube along the circumference, and an inlet tube 4 connected to the air barrier is provided on the outer tube; a first fire inlet hole 7 is provided at the front end of the inner tube, and a heat mixing outlet 8 is provided at the rear end of the inner tube; the internal space section at the front end of the inner tube is set as a preheating chamber 13, and the remaining internal space section at the rear end of the inner tube is set as a mixing chamber 12, and a plurality of nozzles 5 are provided on the inner tube wall located in the mixing chamber, and a nozzle 6 is provided at one end of each nozzle, and the other end of each nozzle is connected to the air barrier.

[0024] The length of the preheating chamber is 1 / 5 to 1 / 3 of the length of the inner tube. For example, if the length of the inner tube is 3 meters, the length of the preheating chamber is limited to 0.6 to 1 meter, and the length of the mixing chamber is about 2 to 2.4 meters.

[0025] The design position of each nozzle and the spray direction of the nozzle on each nozzle give priority to the water or wind sprayed by each nozzle being able to cover or spread throughout the inner tube space located at the mixing chamber, thereby ensuring the heat exchange efficiency. The spray direction 10 of all or part of the nozzles is perpendicular to the inner tube axis 11, so that the nozzle sprays water or wind perpendicularly to the inner tube axis. The spray direction of all or part of the nozzles is inclined toward the rear end of the inner tube, so that the nozzle sprays water or wind inclined toward the rear end of the inner tube. The water or wind sprayed by each nozzle collides with the water or wind sprayed by other nozzles and the wall of the inner tube, bursts out, and is stirred and mixed with the flame of the burner. The above two types of nozzles with spray directions can also be used in combination, such as Figure 1As shown, a plurality of nozzles are evenly arranged in a ring along the circumference of the inner tube to form a group, and a plurality of groups of nozzles are spaced apart along the axial direction of the inner tube to form an array structure of a plurality of nozzles. One or more groups of nozzles with vertical jet nozzles are provided for every two groups of nozzles with inclined jet nozzles. The nozzles of the above structure form an array for spraying water or wind in the inner tube. The sprayed water or wind can form a maze structure, thereby prolonging the residence time of the flame heat source, thereby fully carrying out the heat exchange process of the mixture of fire and water or fire and wind.

[0026] The nozzle is a flat nozzle. The narrow end of the flat nozzle is placed horizontally in the inner tube, so that the sprayed water or wind is fan-shaped and contacts and mixes with the flame of the burner head-on. Furthermore, multiple nozzles are evenly arranged on the inner tube wall along the circumferential ring. The flat nozzles on each nozzle are deflected with a certain deflection angle with the axis of the corresponding nozzle as the axis. The deflection angle is preferably 2 to 5 degrees, so that the fan-shaped water or wind sprayed by the multiple nozzles arranged in an annular shape along the inner tube forms a structure similar to a spiral blade, which can not only prevent the fan-shaped water or wind sprayed by adjacent flat nozzles from interfering with each other, but also generate a narrow fire gap between the two, further prolonging the retention time of the flame heat source and significantly improving the heat exchange efficiency.

[0027] The outlet of the inlet pipe is located on the outer pipe wall at the junction of the preheating chamber and the mixing chamber. The water inlet direction of the inlet pipe is inclined toward the rear end of the inner pipe.

[0028] like Figure 4 As shown, a water-assisted combustion device for a burner is installed at the front end of the inner tube, and the device has a water supply box 27 and a fire tube 32. A heat-insulating layer 29 is provided on the inner wall of the fire tube, and a heat-insulating layer 28 is provided on the surface of the heat-insulating layer. A second fire inlet hole 23 is provided at the front end of the fire tube, and a flame-spraying hole 35 is provided at the rear end of the fire tube, which is opposite to the first fire inlet hole at the front end of the inner tube. A steam generating pipe 30 and a steam distillation pipe 31 are provided in the fire tube, and the steam generating pipe is placed on the periphery of the steam distillation pipe, and a fire gap 33 is provided between the steam generating pipe and the steam distillation pipe; the water inlet 24 at the front end of the steam generating pipe is connected with the water supply box, and the air outlet at the rear end of the steam generating pipe is connected with the air inlet at the rear end of the steam distillation pipe, and a combustion-assisted nozzle 34 located at the center of the fire tube is provided at the front end of the steam distillation pipe, and a plurality of heat collecting fins 36 are provided in the steam distillation pipe at the combustion-assisted nozzle.

[0029] The nozzle refers to a water curtain used to rectify and splash the high-pressure water in the nozzle into a scattered shape. Usually, the shape of the water curtain is umbrella-shaped, fan-shaped, spherical, etc. According to actual needs, commercially available high-pressure water mist nozzle products are preferably used; the front end of the outer tube or the inner tube is provided with a mounting flange 9 for connecting to the first fire inlet hole at the front end of the burner flame outlet or the fire tube in the water combustion-supporting device.

[0030] The trial product dimensions of the direct mixing heat exchanger of the present application are as follows: the inner diameter of the inner tube is 219 mm, the wall thickness of the inner tube and the outer tube is 6 mm, the inner diameter of the outer tube is 291 mm, the thickness of the air barrier between the inner and outer tubes is about 30 mm, the total length of the inner and outer tubes is about 3000 mm, the length of the preheating chamber at the front end of the inner tube is about 700 mm, and the remaining space at the rear end of the inner tube is a mixing chamber. Each nozzle adopts a standard 3-branch water pipe, and the nozzle of each branch pipe is processed into a flat mouth with a flat mouth width of 0.2±0.1 mm. The inlet pipe adopts a standard 2-inch water pipe. During the test, the water flow rate of the inlet pipe was 50 to 60 tons per hour. A domestic environmentally friendly burner with a power of 300,000 kcal was used. After the direct-mixed heat exchanger was running and tended to be in a stable and normal working state, the water inlet temperature at the inlet pipe was measured to be 25 to 30°C, and the water outlet temperature at the mixing outlet was measured to be 80 to 85°C. In the process of repeated tests, the thermal efficiency of the device of the present application can reach up to 98%, and the technical effect is remarkable.

[0031] like Figure 3 As shown, when the direct-mixing heat exchanger of the present application is used to replace the traditional hot water boiler, a water tank 16 is also provided. The water tank is a hot water storage device in the heat-using equipment. The mixed heat outlet is connected to the water inlet pipe 17 of the water tank, and the flame nozzle 15 of the burner 14 is connected to the first fire inlet hole. In this combined structure, the front end of the inner tube is slightly higher than the rear end or an inner convex edge is provided in the front end of the inner tube. The purpose is to allow the accumulated water in the tube to flow into the water tank by gravity. A water distributor 18 and a circulation pipe 19 are installed in the water tank. The outlet of the water inlet pipe of the water tank is placed below the water distributor, and the upper end of the circulation pipe is connected to the water inlet end of the water distributor. A circulation pump 20 is provided on the circulation pipe, and the lower end of the circulation pipe is placed at the bottom of the water tank for drawing stored water. The water in the water tank is supplied to the water distributor by a circulating pump for downward spraying to recover the calorific value of the flame introduced by the water inlet pipe, so as to further improve the thermal efficiency of the direct-mixed heat exchanger of the present application. The water in the water tank is supplied to the heat-using equipment 22 by a water pump 21. The water after use by the heat-using equipment can be used as circulating water and re-pressurized to supply the direct-mixed heat exchanger for use, so as to form a closed loop. In the structure utilizing water circulation, the water tank is provided with a water level sensor. When the water level sensor detects that the water level in the water tank is too low, the inlet pipe on the outer pipe is quantitatively replenished with water through an automatic water replenishing mechanism. The water inlet end of the inlet pipe or the water tank or the user pipeline is equipped with a multi-stage filter screen for filtering impurities in the water to avoid clogging the nozzle.

[0032] The burner preferably uses a burner with clean tail smoke or clean energy as fuel, such as a methanol burner, a natural gas burner, a smokeless particle burner, a low nitrogen burner, etc., so as to obtain clean hot water or hot air. Figure 4As shown, in order to further improve the technical effect of the direct-mixed heat exchanger of the present application, the direct-mixed heat exchanger of the present application also includes the water combustion-supporting device. The working principle of the water combustion-supporting device is as follows: the flame-spraying end of the burner is placed in the first fire inlet hole at the front end of the fire tube, so that the flame generated by the burner passes through the inside of the fire tube and is ejected from the flame-spraying hole at the rear end of the fire tube. The flame of the burner continuously heats the steam generating pipe and the steam distillation pipe. Water is added to the water supply tank and the water level is maintained. The water enters the steam generating pipe through the water outlet pipe of the water supply tank. The water in the steam generating pipe is heated to generate superheated steam and then enters the steam distillation pipe. The steam distillation pipe is closer to the center of the fire tube than the steam generating pipe, so it is heated by the burner flame. The temperature is higher. In the continuous heating process, the superheated distillation steam in the steam distillation pipeline is cracked into two hydrogen and one oxygen plasma by the high temperature of more than one thousand degrees. The heat energy in the hydrogen and oxygen ion state generated is mixed and burned with the fire ejected from the burner in the fire tube through the combustion-supporting nozzle. Oxygen is a combustion-supporting gas and hydrogen is a combustible gas. After the mixture participates in the combustion, it not only greatly improves the flame temperature and fire intensity, but also enables the unburned fuel in the burner flame to burn again; thereby achieving the technical effect of increasing the flame calorific value of the burner and making the tail smoke after combustion colorless and odorless. The installation of the water combustion-supporting device can make the mixed hot water or hot air cleaner, thereby reducing the frequency of changing water or changing the filter and reducing the cost of use.

[0033] In the water combustion-supporting device, the combustion-supporting nozzle is located at the center of the fire tube, which can directly send the decomposed hydrogen and oxygen into the middle of the flame of the burner for mixed combustion. The combustion-supporting nozzle can also serve as a spoiler to break up the flame sprayed from the cluster, stir the unburned fuel in the flame and combine it with hydrogen and oxygen for mixed combustion, further improve the combustion efficiency, and shorten the flame combustion distance. The heat collecting fins can effectively increase the contact area with the superheated dry distillation steam, thereby improving the decomposition efficiency of the superheated dry distillation steam. The inner wall of the fire tube is provided with a heat-insulating layer, and the surface of the heat-insulating layer is provided with a heat-insulating layer, which is used to gather the temperature generated by the flame in the fire tube, so that the device works stably. A burner connecting flange is mounted on the fire inlet, and the burner connecting flange is fixedly connected to the fire tube. The burner connecting flange is used to install the water combustion-supporting device at the flame-spraying hole of the burner. The water inlet at the front end of the steam generating pipeline is connected to the water supply tank through the water supply tank outlet pipe 25. A flow valve 26 is installed on the water supply tank outlet pipe. The flow valve is used to adjust the working condition of the water combustion-supporting device to achieve the best technical effect.

[0034] In the description of this application, the "front" refers to the direction close to the burner, and the "rear" is the opposite direction of the "front"; "inside" refers to the direction toward or close to the axis of the inner tube, and "outside" is the opposite direction of the "inside"; the "first" and "second" mentioned in the text are only used to distinguish and describe the characteristics, and do not represent the position order. In the description of this application, the terms "provided with", "connected" and so on should be understood in a broad sense in this field. For example: "The outer tube is provided with an inlet pipe connected to the air-insulating layer" means that the inlet pipe and the air-insulating layer can transmit the medium of water or wind. For ordinary technicians in this field, the outer tube must be processed with a through hole, and the inner side of the through hole is the air-insulating layer. The pipe mouth of the inlet pipe is opposite to the through hole, and the pipe mouth of the inlet pipe is sealed and fixedly connected to the through hole along the circumference by welding or flange docking; the specific meaning of each term in this application can be understood according to the specific situation.

Claims

1. Direct mixing heat exchanger, characterized by: The invention comprises an inner tube and an outer tube which are sleeved together, and an air barrier is arranged between the inner and outer tubes; two ends of the outer tube are sealed and fixedly connected with two ends of the inner tube along the circumference, and an inlet tube which is connected with the air barrier is arranged on the outer tube; a first fire inlet hole is arranged at the front end of the inner tube, and a heat mixing outlet is arranged at the rear end of the inner tube; the internal space section at the front end of the inner tube is set as a preheating chamber, and the remaining internal space section at the rear end of the inner tube is set as a mixing chamber; a plurality of nozzles are arranged on the wall of the inner tube in the mixing chamber, and a nozzle is arranged at one end of each nozzle, and the other end of each nozzle is connected with the air barrier; a water-assisted combustion device for a burner is arranged at the front end of the inner tube, and the device comprises a water supply tank and a fire tube; an insulation layer is arranged on the inner wall of the fire tube, and the insulation layer An insulating layer is provided on the surface, a second fire inlet hole is provided at the front end of the fire tube, and a flame spraying hole is provided at the rear end of the fire tube, the flame spraying hole is opposite to the first fire inlet hole at the front end of the inner tube, a steam generating pipe and a steam distillation pipe are provided in the fire tube, the steam generating pipe is placed on the periphery of the steam distillation pipe, and a fire gap is provided between the steam generating pipe and the steam distillation pipe; the water inlet at the front end of the steam generating pipe is connected with the water supply tank, the air outlet at the rear end of the steam generating pipe is connected with the air inlet at the rear end of the steam distillation pipe, a combustion-supporting nozzle is provided at the front end of the steam distillation pipe at the center of the fire tube, and a plurality of heat collecting fins are provided in the steam distillation pipe at the combustion-supporting nozzle.

2. The direct mixing heat exchanger according to claim 1, characterized in that: The length of the preheating chamber is 1 / 5 to 1 / 3 of the length of the inner tube.

3. The direct mixing heat exchanger according to claim 1, characterized in that: The spray direction of all or part of the nozzles is perpendicular to the axis of the inner tube.

4. The direct mixing heat exchanger according to claim 1, characterized in that: The spraying direction of all or part of the nozzles is inclined toward the rear end of the inner tube.

5. The direct mixing heat exchanger according to claim 1, characterized in that: The nozzle is a flat nozzle.

6. The direct mixing heat exchanger according to claim 1, characterized in that: The pipe opening at the outlet end of the inlet pipe is located on the outer pipe wall at the junction of the preheating chamber and the mixing chamber.

7. The direct mixing heat exchanger according to claim 1, characterized in that: The water inlet direction of the inlet pipe is inclined toward the rear end of the inner pipe.

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