WO2013166900A1

WO2013166900A1 - Driving device for sucking, compressing, expanding and exhausting strokes in steam power cycle

Info

Publication number: WO2013166900A1
Application number: PCT/CN2013/074158
Authority: WO
Inventors: 安瑞生; 安丰恺
Original assignee: An Ruisheng; An Fengkai
Priority date: 2012-05-07
Filing date: 2013-04-12
Publication date: 2013-11-14
Also published as: CN202560492U

Abstract

A driving device for sucking, compressing, expanding and exhausting strokes in a steam power cycle comprises a casing (25) having two chambers (26, 27) and a hollow piston (38) installed therein. Two telescopic pipes (30, 31) are connected with the hollow piston (38) and a master controlling valve (7). The master controlling valve (7) is connected with a supercharger (9) through a gas feeding main pipe. The supercharger (9) is connected with a pressure stabilizing box (4), which is connected with a first heat exchanger (2) and a second heat exchanger (3) via a first one-way valve (18) and a second one-way valve (19), respectively. The first heat exchanger (2) is communicated with the first chamber (26) via a fourth one-way valve (36). The second heat exchanger (3) is communicated with the second chamber (27) via a fifth one-way valve (37). A reservoir (8) is communicated with the first chamber (26) and the second chamber (27). The driving device is capable of utilizing solar power and low-temperature thermal energy to heat a low-temperature working medium, and has advantages of avoiding pollution and reducing cost.

Description

Steam power circulation suction, pressure, expansion and discharge drive device

Technical field

The utility model relates to a steam power circulation suction, pressure, expansion and discharge driving device.

Background technique

Solar energy and low-temperature heating can be widely found in nature, and have the advantages of large reserves and easy access. The low-temperature heating energy refers to the waste heat in the factories and mines, the heat of burning the crop straws in the vast rural and remote areas, and the waste heat of the central heating of the urban residential quarters. However, solar energy and low-temperature heating can be low-grade energy and cannot be used industrially. At present, it can only be wasted. Therefore, there is an urgent need to develop a device that converts solar energy and low temperature heating energy into industrially usable energy.

Utility model content

The purpose of the utility model is to provide a steam power circulation suction, pressure, expansion and discharge drive device. It is a device that converts solar or low-temperature heating energy into industrially-adapted pneumatic kinetic energy, and provides driving force for existing pneumatic industrial equipment, thereby solving the problems of the prior art.

The object of the utility model is achieved by the following technical solutions: a steam power circulation suction, pressure, expansion and discharge drive device, comprising a casing, a first heat exchanger, a second heat exchanger and a general control valve; The core piston has an air cavity on each side of the air core piston, and the two air chambers are not connected to each other, and the air core piston divides the inner cavity of the casing into the first cavity and the second cavity; a telescopic tube, the second telescopic tube is installed in the second cavity; the inner ends of the first telescopic tube and the second telescopic tube are respectively connected with the hollow core piston, and the first telescopic tube and the second telescopic tube are respectively respectively combined with the hollow core piston The air chambers are connected to each other; the outer ends of the first telescopic tube and the second telescopic tube are respectively connected to the main control valve through a gas supply branch pipe; the main control valve is connected to the air supply port of the supercharger through the gas supply main pipe; The intake port of the supercharger is connected to the surge tank through the intake manifold, the surge tank is directly connected to the two intake manifolds, or the surge tank is indirectly connected to the two intake manifolds through the summary tube; a pressure control valve or two pressure control valves on each of the two intake manifolds; The tank is connected to the coil of the first heat exchanger through a first check valve through an intake branch pipe; the surge tank is connected to the coil of the second heat exchanger through the second check valve through another intake branch pipe The coil of the first heat exchanger is connected to the first chamber through the first heat exchanger through the fourth one-way valve; the coil of the second heat exchanger is passed through the second heat exchanger The one-way valve is in communication with the second chamber; the first heat exchanger can be exhausted to the surge tank via the first one-way valve, and the second heat exchanger can be exhausted to the surge tank via the second one-way valve; The gas-liquid mixture inside can enter the coil of the first heat exchanger through the fourth one-way valve, and the gas-liquid mixture in the second chamber can enter the coil of the second heat exchanger through the fifth one-way valve; the supercharger The return air inlet and the return air port of the main control valve are respectively connected to the liquid storage tank through a return air pipe; the liquid storage tank communicates with the first cavity through a liquid supply pipe through the sixth check valve; the liquid storage tank passes through another The liquid supply pipe communicates with the second cavity through the seventh one-way valve; the liquid in the liquid storage tank can enter the first cavity or the second cavity through the sixth one-way valve or the seventh one-way valve.

In order to further achieve the object of the present invention, the following technical solution may also be adopted: the first heat exchanger is connected to the hot water tank through two hot water pipes, and the first sub-control valve is jointly installed on the two hot water pipes; The first heat exchanger is connected to the cold water tank through two cold water pipes, and the third branch control valve is jointly installed on the two cold water pipes; the water in the hot water tank and the cold water tank goes to the shell side of the first heat exchanger. The second heat exchanger is connected to the hot water tank through two hot water pipes, and the second sub-control valve is installed on the two hot water pipes; the second heat exchanger is connected to the cold water tank through two cold water pipes; The fourth sub-control valve is installed together on the cold water pipe; the water in the hot water tank and the cold water tank goes to the shell side of the second heat exchanger. A first mass flow meter is connected in series to the intake manifold between the first heat exchanger and the surge tank. A second mass flow meter is connected in series to the intake manifold between the second heat exchanger and the surge tank. a third check valve, a gas accelerator and a Rankor tube are connected in series from the supercharger to the return pipe between the supercharger and the liquid storage tank, and the air inlet and the liquid outlet of the Rank tube and the return pipe The air outlet of the Ranke tube is connected to the intake end of the air motor, and the air outlet end of the air motor is connected to the air return pipe.

The positive effect of the utility model is that it uses solar energy and low-temperature heating energy as a heat source to heat the low-temperature working medium, and utilizes the evaporation and condensation cycle of the low-temperature working medium to continuously convert the thermal energy into the kinetic energy of the high-pressure gas, thereby lowering the energy of the low-grade gas. Converted to high grade energy for industrial applications. It is not subject to geographical limitations, and does not need to consume natural resources such as coal and oil, and can avoid environmental pollution. It is a true green environmental protection device. The utility model also has the advantages of low cost, convenient installation and manipulation.

DRAWINGS

1 is a schematic front view showing the structure of a steam power circulation suction, pressure, expansion and discharge drive device according to the present invention; and FIG. 2 is a partial enlarged structural view of FIG.

LIST OF REFERENCE NUMERALS 1 host 2 first heat exchanger 3 second heat exchanger 4 surge tank 5 hot water tank 6 cold water tank 7 total control valve 8 liquid storage tank 9 supercharger 10 first pump 11 second pump 12 First mass flow meter 13 second mass flow meter 14 first sub-control valve 15 second sub-control valve 16 third sub-control valve 17 fourth sub-control valve 18 first check valve 19 second check valve 20 liquid collection 21 air motor 22 Rank tube 23 gas accelerator 24 third check valve 25 housing 26 first chamber 27 second chamber 28 first stroke switch 29 second stroke switch 30 first telescopic tube 31 second telescopic tube 32 A heat exchanger liquid supply pipe 33 second heat exchanger liquid supply pipe 34 sixth check valve 35 seventh check valve 36 fourth check valve 37 fifth check valve 38 air core piston 39 pressure control valve.

detailed description

The steam power circulation suction, pressure, expansion and discharge drive device of the utility model, as shown in FIG. 2, comprises a casing 25, a first heat exchanger 2, a second heat exchanger 3 and a master control valve 7. An air core piston 38 is disposed in the housing 25, and an air chamber is disposed on each side of the air core piston 38, and the two air chambers are not in communication with each other. The hollow core piston 38 divides the inner cavity of the housing 25 into a first chamber 26 and a second chamber 27. A first telescopic tube 30 is mounted in the first chamber 26, and a second telescopic tube 31 is mounted in the second chamber 27. The inner ends of the first telescopic tube 30 and the second telescopic tube 31 are respectively connected to the hollow core piston 38, and the first telescopic tube 30 and the second telescopic tube 31 are respectively communicated with the two air chambers of the hollow core piston 38. . As shown in FIG. 1, the outer ends of the first telescopic tube 30 and the second telescopic tube 31 are each connected to the main control valve 7 through a gas supply branch. The main control valve 7 is connected to the air supply port of the supercharger 9 through the air supply manifold. The intake port of the supercharger 9 is connected to the surge tank 4 through an intake manifold. The surge tank 4 can be directly connected to the two intake manifolds. As shown in FIG. 1, the surge tank 4 can also be indirectly connected to the two intake manifolds through the manifold. In order to ensure that the exhaust pressure of the two intake manifolds to the surge tank 4 is always set, as shown in Fig. 1, a pressure control valve may be installed on the manifold, or one of the two intake manifolds may be installed. Pressure control valve. The pressure control valve is the pressure control valve 39 shown in FIG. The surge tank 4 is connected to the coil of the first heat exchanger 2 via the first check valve 18 through an intake branch pipe; the surge tank 4 passes through the other intake manifold through the second check valve 19 and the second The coils of the heat exchanger 3 are connected. As shown in FIG. 1, the coil of the first heat exchanger 2 communicates with the first chamber 26 through the first heat exchanger supply pipe 32 via the fourth check valve 36. The coil of the second heat exchanger 3 communicates with the second chamber 27 through the second heat exchanger supply pipe 33 via the fifth check valve 37. The first heat exchanger 2 can be exhausted to the surge tank 4 via the first check valve 18 and the pressure control valve 39, and the second heat exchanger 3 can pass through the second check valve 19 and the pressure control valve 39 to the surge tank 4 exhaust. The gas-liquid mixture in the first chamber 26 can enter the coil of the first heat exchanger 2 via the fourth check valve 36, and the gas-liquid mixture in the second chamber 27 can enter the second heat exchange via the fifth check valve 37. The coil of the device 3. The return air port of the supercharger 9 and the air return port of the main control valve 7 are each connected to the liquid storage tank 8 through a return air pipe. As shown in FIGS. 1 and 2, the liquid storage tank 8 communicates with the first chamber 26 through a sixth supply valve through a sixth one-way valve 34. The liquid storage tank 8 communicates with the second chamber 27 through the other one of the liquid supply tubes via the seventh check valve 35. The liquid in the reservoir 8 can enter the first chamber 26 or the second chamber 27 via the sixth check valve 34 or the seventh check valve 35. The total control valve 7 can be a two-position four-way valve as shown in FIG. 1 , that is, an existing four-way reversing valve; or other existing valves that can change the air supply direction of the supercharger 9 . The housing 25, the hollow core piston 38, the first telescopic tube 30 and the second telescopic tube 31 are connected to form a main body 1.

During the whole working process of the driving device, the circulating water is heated by the solar energy or the low temperature heating, the circulating water is kept at a constant temperature, and the circulating water is used to heat the low temperature working medium, so that the driving device can heat the solar energy or the low temperature. Heat is converted to gas flow energy for industrial applications.

The working state of the driving device will be described below with the state shown in FIG. 1 as the starting state:

The first link: the main control valve 7 in this step causes the supercharger 9 to be electrically connected to the first telescopic tube 30, the second telescopic tube 31 to be electrically connected to the liquid storage tank 8, and the circulating hot water to go to the shell of the second heat exchanger 3 The coil of the second heat exchanger 3 is heated, and the first heat exchanger 2 stops supplying hot water. The main control valve 7 supplies air to the first telescopic tube 30 through a gas supply branch pipe, and the gas in the second telescopic tube 31 is returned to the liquid storage tank 8 through the other air supply branch pipe via the main control valve 7. The first telescopic tube 30 pushes the hollow core piston 38 to the right. On the one hand, a negative pressure is formed in the first chamber 26 to suck the liquid cryogenic working fluid in the liquid storage tank 8 into the first chamber through the sixth check valve 34. 26; on the other hand, the liquid cryogenic working medium in the second chamber 27 passes through the second heat exchanger liquid supply pipe 33 through the fifth one-way valve 37 into the coil of the second heat exchanger 3, the liquid low temperature working fluid After the heat is vaporized in the second heat exchanger 3 to generate high pressure gas, after the set pressure is reached, the high pressure gas enters the surge tank 4 through the second check valve 19 and the pressure control valve 39 through an intake branch pipe. The surge tank 4 passes a part of the high-pressure gas into the supercharger 9 through the intake manifold, and the supercharger 9 pressurizes the high-pressure gas and supplies it to the main control valve 7, and the main control valve 7 continuously supplies air to the first telescopic tube 30. Thereby, it is ensured that the first telescopic tube 30 can push the hollow core piston 38 to the right, and the voltage regulator box 4 outputs another portion of the high pressure gas to drive the industrial equipment to work and provide kinetic energy for the industrial equipment. When the air-core piston 38 moves to the set position at the rightmost end, the main control valve 7 is actuated, and the driving device enters the second step.

The second step: the main control valve 7 is operated to make the supercharger 9 and the second telescopic tube 31 conductive, the first telescopic tube 30 and the liquid storage tank 8 are turned on; the circulating hot water is taken away from the shell side of the first heat exchanger 2 The coil of the first heat exchanger 2 is heated, and the second heat exchanger 3 stops supplying hot water. The main control valve 7 supplies air to the second telescopic tube 31 through an air supply branch pipe, and the gas in the first telescopic tube 30 is returned to the liquid storage tank 8 through the other air supply branch pipe via the main control valve 7. The second telescopic tube 31 pushes the hollow core piston 38 to the left. On the one hand, a negative pressure is formed in the second chamber 27 to suck the liquid cryogenic working medium in the liquid storage tank 8 into the second chamber through the seventh check valve 35. 27; on the other hand, the liquid cryogenic working fluid in the first chamber 26 passes through the first heat exchanger liquid supply pipe 32 through the fourth one-way valve 36 into the coil of the first heat exchanger 2, and the liquid cryogenic working fluid is The first heat exchanger 2 absorbs heat to generate high-pressure gas. After the set pressure is reached, the high-pressure gas enters the surge tank 4 through the first check valve 18 and the pressure control valve 39 through an intake branch pipe. The surge tank 4 passes a part of the high-pressure gas into the supercharger 9 through the intake manifold, and the supercharger 9 pressurizes the high-pressure gas and supplies it to the main control valve 7, and the main control valve 7 continuously supplies air to the second telescopic tube 31. Thereby, it is ensured that the second telescopic tube 31 can push the hollow core piston 38 to the left. When the hollow core piston 38 moves to the set position at the leftmost end, it stops and re-enters the second link. The above two steps are repeated, so that the surge tank 4 can always output high pressure gas to the outside.

During the entire working process, the return port of the supercharger 9 is always returned to the liquid storage tank 8.

To achieve automated control, as shown in FIG. 2, a first travel switch 28 is mounted in the first chamber 26 and a second travel switch 29 is mounted in the second chamber 27. When the air core piston 38 is moved to the right to actuate the second limit switch 29, the second limit switch 29 transmits a signal to the controller, and the controller causes the main control valve 7 to operate to switch the working link of the driving device. Similarly, when the air core piston 38 is moved to the left to touch the first limit switch 28, the first limit switch 28 transmits a signal to the controller, and the controller causes the main control valve 7 to operate to switch the working link.

The main function of the first heat exchanger 2 and the second heat exchanger 3 is to enable the low temperature working fluid entering the heat to be vaporized by heat, so that the low temperature working fluid is taken away from the shell, and the hot water is taken away. The heat exchange effect is the same, and only the connection pipes of the first heat exchanger 2 and the second heat exchanger 3 are adjusted accordingly.

In order to facilitate the supply of hot water or cold water to the first heat exchanger 2 or the second heat exchanger 3, the efficiency of the driving device is increased. As shown in FIG. 1, the first heat exchanger 2 passes two heats. The water pipe is connected to the hot water tank 5 to form a circulating water path, and the first sub-control valve 14 is commonly installed on the two hot water pipes. The first heat exchanger 2 is connected to the cold water tank 6 through two cold water pipes, and the third branch control valve 16 is commonly installed on the two cold water pipes. The water in the hot water tank 5 and the cold water tank 6 goes to the shell side of the first heat exchanger 2. As shown in FIG. 1, the second heat exchanger 3 is connected to the hot water tank 5 through two hot water pipes, and the second sub-control valve 15 is commonly installed on the two hot water pipes. The second heat exchanger 3 is connected to the cold water tank 6 through two cold water pipes. A fourth sub-control valve 17 is commonly installed on the two cold water pipes. The water in the hot water tank 5 and the cold water tank 6 goes to the shell side of the second heat exchanger 3. The first sub-control valve 14, the second sub-control valve 15, the third sub-control valve 16 and the fourth sub-control valve 17 are all two-position four-way valves, and have two-wire simultaneous conduction and simultaneous disconnection. The heating direction of the hot water tank 5 and the cold water tank 6 can be controlled. The hot water tank 5 may be a water tank of a solar water heater, and collects solar energy through a solar heat collecting tube to heat the water therein. The hot water tank 5 may also be a common water tank in which a heat exchange coil is installed, and the heat exchange coil transfers the heat of the low temperature heating energy to the water in the hot water tank 5. The cold water tank 6 can cooperate with the water tower, and the water tower can fully cool and cool the water in the cold water tank 6. In the first step, the hot water tank 5 supplies hot water to the second heat exchanger 3 to vaporize the working fluid in the second heat exchanger 3 into a high pressure gas; meanwhile, the cold water tank 6 supplies the first heat exchanger 2 The cold water cools the coil of the first heat exchanger 2 so that a negative pressure is formed in the coil of the first heat exchanger 2, and the working medium in the first chamber 26 is facilitated to enter the coil of the first heat exchanger 2. In the second step, the hot water tank 5 supplies hot water to the first heat exchanger 2 to vaporize the working fluid in the first heat exchanger 2 into a high pressure gas; meanwhile, the cold water tank 6 supplies the second heat exchanger 3 The cold water cools the coil of the second heat exchanger 3 so that a negative pressure is formed in the coil of the second heat exchanger 3, and the working medium in the second chamber 27 is facilitated to enter the coil of the second heat exchanger 3. In order to facilitate the hot water and cold water circulation, as shown in FIG. 1, the first pump 10 or the second pump 11 is installed on the hot water pipe or the cold water pipe.

In order to facilitate control of the first heat exchanger 2 and the second heat exchanger 3 when hot water or cold water is introduced, as shown in FIG. 1 , the first heat exchanger 2 and the surge tank 4 are connected in series on the intake manifold. The first mass flow meter 12. As shown in FIG. 1 , a second mass flow meter 13 is connected in series to the intake manifold between the second heat exchanger 3 and the surge tank 4 . When the first mass flow meter 12 detects that the high pressure gas discharged from the first heat exchanger 2 reaches the set value, the first mass flow meter 12 signals the controller, and the controller stops supplying the hot water to the first heat exchanger 2. And the hot water supply to the second heat exchanger 3 is started. Similarly, when the second mass flow meter 13 detects that the high pressure gas discharged from the second heat exchanger 3 reaches the set value, the second mass flow meter 13 signals the controller, and the controller stops to the second heat exchanger 3. The hot water is supplied, and the hot water supply to the first heat exchanger 2 is started.

Since the gas discharged from the supercharger 9 has a certain temperature and pressure and has a certain amount of energy, it is necessary to make full use of this part of the energy. As shown in FIG. 1, the third check valve 24, the gas accelerator 23 and the Rank tube 22 are connected in series from the supercharger 9 on the return pipe between the supercharger 9 and the liquid storage tank 8, and the Rankor tube 22 The air inlet and the liquid outlet communicate with the air return pipe. The air outlet of the Rank tube 22 is connected to the intake end of the air motor 21, and the air outlet end of the air motor 21 is connected to the air return pipe. The gas returned by the supercharger 9 is accelerated by the gas accelerator 23, and then enters the Ranke tube 22 for hot and cold separation. The separated cryogenic liquid is directly returned to the liquid storage tank 8, and the separated high temperature gas pushes the air motor 21 to work. Return to the reservoir 8 again. In order to synchronously return the air motor 21 and the Rankor tube 22 to the liquid storage tank 8, a liquid trap 20 is connected in series to the return air tube, and the air outlet end of the air motor 21 and the liquid outlet of the Rankor tube 22 are both connected to the liquid trap 20. Unicom.

The technical solutions described in the present invention are not limited to the scope of the embodiments described in the present invention. The technical contents not described in detail in the present invention are all well-known techniques.

Claims

a steam power circulation suction, pressure, expansion and discharge drive device, comprising: a casing (25), a first heat exchanger (2), a second heat exchanger (3) and a total control valve (7); The air core piston (38) is installed in the body (25), and an air chamber is disposed on each side of the air core piston (38), the two air chambers are not connected to each other, and the air core piston (38) is to be the housing (25) The inner cavity is divided into a first cavity (26) and a second cavity (27); a first telescopic tube (30) is mounted in the first cavity (26), and a second telescopic tube (31) is mounted in the second cavity (27); The inner ends of the first telescopic tube (30) and the second telescopic tube (31) are respectively connected to the hollow core piston (38), and the first telescopic tube (30) and the second telescopic tube (31) are respectively associated with the air core piston The two air chambers of (38) are in communication; the outer ends of the first telescopic tube (30) and the second telescopic tube (31) are respectively connected to the main control valve (7) through a gas supply branch; the total control valve (7) The air supply manifold is connected to the air supply port of the supercharger (9); the air inlet of the supercharger (9) is connected to the surge tank (4) through the intake manifold, and the surge tank (4) and Two intakes The tube is directly connected, or the voltage regulator box (4) is indirectly connected to the two intake manifolds through the summary tube; a pressure control valve is installed on the summary tube, or a pressure control valve is installed on each of the two inlet manifolds; 4) connected to the coil of the first heat exchanger (2) through a first check valve (18) through an intake branch pipe; the surge tank (4) passes through the second check valve through the other intake branch pipe (19) being connected to the coil of the second heat exchanger (3); the coil of the first heat exchanger (2) passing through the first heat exchanger supply pipe (32) via the fourth check valve (36) The first chamber (26) communicates; the coil of the second heat exchanger (3) communicates with the second chamber (27) through the second heat exchanger liquid supply tube (33) via the fifth one-way valve (37); A heat exchanger (2) can be vented to the surge tank (4) via the first check valve (18), and the second heat exchanger (3) can pass through the second check valve (19) to the surge tank ( 4) Exhaust; the gas-liquid mixture in the first chamber (26) can enter the coil of the first heat exchanger (2) via the fourth check valve (36), and the gas-liquid mixture in the second chamber (27) The physical energy enters the second heat exchanger via the fifth one-way valve (37) 3) the coil; the return port of the supercharger (9) and the return port of the main control valve (7) are each connected to the liquid storage tank (8) through a return air pipe; the liquid storage tank (8) is passed through one The liquid pipe communicates with the first cavity (26) via the sixth check valve (34); the liquid storage tank (8) communicates with the second cavity (27) through the other liquid supply pipe via the seventh check valve (35) The liquid in the reservoir (8) can enter the first chamber (26) or the second chamber (27) via the sixth check valve (34) or the seventh check valve (35).
The steam power circulation suction, pressure, expansion and discharge driving device according to claim 1, wherein the first heat exchanger (2) is connected to the hot water tank (5) through two hot water pipes, two The first sub-control valve (14) is jointly installed on the hot water pipe; the first heat exchanger (2) is connected to the cold water tank (6) through two cold water pipes, and the third sub-control valve is jointly installed on the two cold water pipes. (16); the water in the hot water tank (5) and the cold water tank (6) goes to the shell side of the first heat exchanger (2).
The steam power circulation suction, pressure, expansion and discharge driving device according to claim 1 or 2, characterized in that the second heat exchanger (3) is connected to the hot water tank (5) through two hot water pipes a second sub-control valve (15) is installed on the two hot water pipes; the second heat exchanger (3) is connected to the cold water tank (6) through two cold water pipes; and the fourth sub-control is installed on the two cold water pipes The valve (17); the water in the hot water tank (5) and the cold water tank (6) goes to the shell side of the second heat exchanger (3).
The steam power circulation suction, pressure, expansion and discharge driving device according to claim 1, wherein the first heat exchanger (2) and the surge tank (4) are connected in series on the intake manifold. Mass flow meter (12).
The steam power circulation suction, pressure, expansion and discharge driving device according to claim 1, characterized in that: the second heat exchanger (3) and the surge tank (4) are connected in series with the intake manifold Mass flow meter (13).
The steam power circulation suction, pressure, expansion and discharge driving device according to claim 1, characterized in that: the self-pressurizer on the return pipe between the supercharger (9) and the liquid storage tank (8) The third check valve (24), the gas accelerator (23) and the Rankor tube (22) are connected in series, and the air inlet and the liquid outlet of the Rank tube (22) communicate with the return air tube; The air outlet of (22) is connected to the intake end of the air motor (21), and the air outlet end of the air motor (21) is connected to the air return pipe.