阅读说明：本技术 一种高膨胀比水平对置活塞式膨胀机及控制方法 (High-expansion-ratio horizontally-opposed piston type expansion machine and control method ) 是由 周乃君 石文君 欧少端 苏文 蒋梓涛 于 2020-07-31 设计创作，主要内容包括：一种高膨胀比水平对置活塞式膨胀机及控制方法,包括一组水平对置活塞、缸体、缸盖、连杆、曲轴及曲轴箱、进排气管、进排气阀及润滑系统和控制系统。本膨胀机通过输入高压工质推动活塞往复运动,达到被动进气和膨胀做功的目的。本装置可以用于由有机朗肯循环构成的发动机排气废热回收系统,并将工质热能转化为机械能输出。与现有活塞式膨胀机相比,本发明的特点在于将对置活塞与进排气管及进排气阀进行集成,从而减少结构件及由此产生的机械损失,具有膨胀比大、组件少、结构紧凑、热功转换效率高等优点,有较为广泛的应用前景。(A high expansion ratio horizontal opposed piston type expansion machine and a control method thereof comprise a group of horizontal opposed pistons, a cylinder body, a cylinder cover, a connecting rod, a crankshaft, a crankcase, an air inlet and exhaust pipe, an air inlet and exhaust valve, a lubricating system and a control system. The expander pushes the piston to reciprocate by inputting high-pressure working medium, thereby achieving the purposes of passive air intake and expansion acting. The device can be used for an engine exhaust waste heat recovery system formed by an organic Rankine cycle, and converts working medium heat energy into mechanical energy for output. Compared with the existing piston type expansion machine, the invention has the characteristics that the opposed pistons are integrated with the air inlet and outlet pipes and the air inlet and outlet valves, thereby reducing structural members and mechanical loss generated by the structural members, having the advantages of large expansion ratio, few components, compact structure, high heat-power conversion efficiency and the like, and having wider application prospect.)

1. The high-expansion-ratio horizontally-opposed piston type expansion machine is characterized by comprising an air inlet valve (12), an air outlet valve (13), a crankshaft (5), a first air cylinder and a second air cylinder which are evenly distributed on two sides of the crankshaft, wherein the air inlet valve (12) and the air outlet valve (13) are both three-way electric ball valves, connecting rods of the first air cylinder and the second air cylinder jointly drive the crankshaft (5) to rotate to do work, rodless cavities of the first air cylinder and the second air cylinder are communicated with two air outlets of the air inlet valve (12) through independent air inlet branch pipes (10), the rodless cavities of the first air cylinder and the second air cylinder are communicated with two air inlets of the air outlet valve (13) through independent air outlet branch pipes (11), the air inlet of the air inlet valve (12) is communicated with a high-pressure working medium outlet, and the air outlet of the air outlet valve (13) is communicated with an exhaust.

2. The high expansion ratio horizontal opposed piston type expansion machine according to claim 1, wherein the first cylinder and the second cylinder are identical in structure and each comprise a cylinder body (1), a cylinder cover (2), a piston head (3) and a connecting rod (4), the cylinder body (1) is hermetically connected with a crankcase (6), an inner cavity of the cylinder body (1) is communicated with an inner cavity of the crankcase (6), a crankshaft (5) is arranged in the crankcase (6), the piston head (3) is installed in the cylinder body (1), the piston head (3) is connected with the crankshaft (5) through the connecting rod (4), and an air inlet hole and an air outlet hole for installing an air inlet branch pipe (10) and an air outlet branch pipe (11) are formed in the cylinder cover (2).

3. The high expansion ratio horizontal opposed piston type expander according to claim 2, wherein the top of the piston head (3) is a plane, two oil rings and one gas ring are arranged on the contact surface of the piston head (3) and the cylinder body (1), and the piston head (3) is connected with the small end of the connecting rod (4) through a first pin (17); the big ends of the connecting rods (4) are connected through a crank (19) on the crankshaft (5) of the second column pin (18).

4. The high expansion ratio horizontal opposed-piston expander according to claim 2, further comprising a lubrication system including an oil pump (29), an oil delivery pipe (30), an oil return pipe (31), a filter (32), an air-cooled radiator (33), and an oil filler port (34); the oil pump (29) cools and cools lubricating oil in the oil storage tank through an air-cooled radiator (33) through an oil conveying pipe (30), then conveys the lubricating oil to the cylinder body (1), the air inlet valve (12) and the exhaust valve (13), and conveys the lubricating oil in the crankcase to the oil storage tank through a filter through an oil return pipe (31).

5. The high expansion ratio horizontal opposed-piston expander according to claim 4, wherein the cylinder (1), intake valve (12) and exhaust valve (13) are injection lubricated and the crankshaft is splash lubricated.

6. The high expansion ratio horizontal opposed piston type expansion machine according to any one of claims 1 to 5, wherein the three-way electric ball valve comprises a valve body (24), a valve core (25), a valve core shaft (26) and a motor (28) for driving the valve core (25) to rotate through the valve core shaft (26), a crankshaft position sensor (35) for detecting a crankshaft phase angle in real time is arranged on the crankshaft (5), a rotating shaft position sensor (38) for detecting a real-time rotating angle of the valve core in real time is mounted on the valve core shaft (26), the rotating shaft position sensor (38), the crankshaft position sensor (35) and the motor (28) are electrically connected with a control system, and the control system controls motor actions of the air inlet valve (12) and the exhaust valve (13) through data of the rotating shaft position sensor (38) and the crankshaft position sensor (35).

7. The high expansion ratio horizontal opposed piston type expansion machine according to claim 6, wherein a signal gear (8) linked with the crankshaft (5) is installed on the crankshaft (5), a signal wheel (27) linked with a spool shaft (26) is installed on a spool shaft of the three-way electric ball valve, the crankshaft position sensor (35) detects the signal gear (8) in real time, and the rotary shaft position sensor (38) detects the signal wheel (27) in real time.

8. The high expansion ratio horizontal opposed-piston expander according to claim 6, wherein the motor (28) rotates the spool (25) unidirectionally within the valve body (25).

9. A control method of a high expansion ratio horizontal opposed piston type expansion machine is used for controlling the high expansion ratio horizontal opposed piston type expansion machine as claimed in any one of claims 6 to 8, and is characterized in that a crankshaft position sensor (35) is used for measuring the tooth missing position on a signal gear (8), a control system is used for calculating the crankshaft rotation angle position and the actual rotation speed of the expansion machine, meanwhile, a rotating shaft position sensor (38) is used for detecting the positions of signal wheels (27) on valve core shafts of an air inlet valve and an exhaust valve, and the control system is used for sending a control command to control a motor to control the valve core positions and the pause duration of the air inlet valve and the exhaust valve, so that the crankshaft (5) is driven to rotate to do work by controlling the air inlet amount and the air exhaust amount of a first cylinder and.

10. The control method according to claim 9, wherein the working phases of the first cylinder and the second cylinder are 180 degrees out of phase, and the specific action process of the first cylinder and the second cylinder is as follows:

firstly, an air inlet valve controls a first air cylinder to be communicated with a high-pressure working medium, a second air cylinder is not communicated with the high-pressure working medium, the first air cylinder admits air and does work through expansion, meanwhile, an exhaust valve controls the second air cylinder to be communicated with an exhaust system, the first air cylinder is not communicated with the exhaust system, and the second air cylinder is in an exhaust state;

when the control system detects that the crank angle reaches a first set phase, the valve core of the air inlet valve rotates to ensure that the first cylinder and the second cylinder are not communicated with the high-pressure working medium, the air inlet is closed, the working medium in the first cylinder is in a free expansion working state, the second cylinder is still in a continuous exhaust state at the moment, and when the crank angle reaches a second set phase, the exhaust valve controls the first cylinder and the second cylinder to be not communicated with the exhaust system and exhaust is closed;

when the crank angle reaches a third set phase, the valve core of the exhaust valve rotates to enable the first cylinder to be conducted with the exhaust system, the second cylinder to be not conducted with the exhaust system, the first cylinder enters an exhaust state, meanwhile, the valve core of the intake valve rotates to enable the second cylinder to be conducted with the high-pressure working medium, the first cylinder to be not conducted with the high-pressure working medium, at the moment, the second cylinder admits air, the first cylinder is in a continuous exhaust state, and therefore the continuous exhaust of the first cylinder is achieved in a circulating mode, and shaft work is output alternately.

Technical Field

The invention belongs to the technical field of expansion machines, and particularly relates to a high-expansion-ratio horizontally-opposed piston type expansion machine and a control method.

Background

With the increasing prominence of the petroleum energy problem, the energy saving of the internal combustion engine is more and more emphasized, wherein, the technology of recovering the waste heat of the exhaust gas of the internal combustion engine and converting the waste heat into power by utilizing the organic Rankine cycle is widely researched due to high heat-power conversion efficiency. The expander is a key device in an energy recovery system, and the existing expander is in the forms of a turbine type, a vortex type, a screw type, a piston type and the like. Considering that the temperature of the tail gas of the internal combustion engine generally reaches about 600 ℃, in order to improve the energy recovery efficiency, the heat exchange temperature of the organic Rankine cycle needs to be adapted to the temperature of the tail gas as much as possible, so that the working pressure of the working medium needs to be improved. And the expansion ratio of the expander is increased (required to reach 20-40) due to the increase of the working medium pressure, so that the expander with a high expansion ratio is required. The turbine type, vortex type and screw type expanders are difficult to meet the requirement of high expansion ratio, and compared with the piston type expander, the piston type expander has obvious advantages.

The power of a common vehicle-mounted internal combustion engine of the existing small and medium-sized compact automobile is usually within the range of hundreds of kilowatts, if an organic Rankine cycle system can be adopted to recover the waste heat of the tail gas of the internal combustion engine, the recovered power is usually within the range of tens of kilowatts, and therefore, how to ensure high expansion ratio has great significance in researching the energy conservation of the vehicle-mounted internal combustion engine while reducing the volume of an expansion machine.

Disclosure of Invention

The invention aims to provide a high-expansion-ratio horizontal opposed-piston type expansion machine and a control method. The expander pushes a pair of horizontally opposite cylinders to move linearly in the expander cylinders by inputting a high-pressure working medium, converts reciprocating linear motion into rotary motion by a connecting rod and a crankshaft mechanism, and converts pressure energy of the working medium into shaft work to be output.

In order to achieve the purpose, the technical scheme adopted by the invention is that the high-expansion-ratio horizontally-opposed piston expander comprises an air inlet valve 12, an air outlet valve 13, a crankshaft 5, a first air cylinder and a second air cylinder which are evenly distributed on two sides of the crankshaft, wherein the air inlet valve 12 and the air outlet valve 13 are both three-way electric ball valves, connecting rods of the first air cylinder and the second air cylinder jointly drive the crankshaft 5 to rotate to do work, rodless cavities of the first air cylinder and the second air cylinder are respectively communicated with two air outlets of the air inlet valve 12 through independent air inlet branch pipes 10, the rodless cavities of the first air cylinder and the second air cylinder are also respectively communicated with two air inlets of the air outlet valve 13 through independent air outlet branch pipes 11, an air inlet of the air inlet valve 12 is communicated with a high-pressure working medium outlet, and an air outlet of the.

By adopting the structure, the device pushes the oppositely arranged cylinder pistons to reciprocate alternately by inputting a high-pressure working medium, achieves the purposes of passive air intake and expansion work, can be used for an engine exhaust waste heat recovery system formed by organic Rankine cycle, converts heat energy into mechanical energy to be output, takes two three-way electric ball valves as air intake and exhaust valves, has high valve concentration, reduces structural members, and has compact oppositely arranged cylinders and large expansion ratio, so that the device has fewer components, compact structure, high heat-power conversion efficiency and convenient vehicle-mounted installation.

In this embodiment, the same structure of first cylinder and second cylinder all includes cylinder body 1, cylinder cap 2, piston head 3 and connecting rod 4, cylinder body 1 and 6 sealing connection of crankcase to 1 inner chamber of cylinder body and 6 inner chambers intercommunication of crankcase, be equipped with bent axle 5 in the crankcase 6, piston head 3 installs in cylinder body 1, piston head 3 passes through connecting rod 4 and is connected with bent axle 5, is equipped with the inlet port and the exhaust hole that are used for installing air intake branch 10 and exhaust branch 11 on the cylinder cap 2. The piston is made of light alloy steel, and the crank shaft and the crank are made of carbon steel. The cylinder body, the cylinder cover, the crankcase, the air inlet branch pipe and the air outlet branch pipe are all made of carbon steel, and the outer sides of the cylinder body, the cylinder cover, the crankcase, the air inlet branch pipe and the air outlet branch pipe are all provided with heat insulation layers, so that the heat dissipation loss of the device is reduced. The heat-power conversion efficiency of the device is improved due to the reduction of mechanical friction loss and heat dissipation loss.

In the embodiment, the top of the piston head 3 is a plane, two oil rings and one gas ring are arranged on the contact surface of the piston head 3 and the cylinder body 1, and the piston head 3 is connected with the small end of the connecting rod 4 through a first pin 17; the big end of the connecting rod 4 is connected with a crank 19 on the crankshaft 5 through a second pin 18.

In the embodiment, the device further comprises a lubricating system, wherein the lubricating system comprises an oil pump 29, an oil delivery pipe 30, an oil return pipe 31, a filter 32, an air-cooled radiator 33 and an oil filling port 34; the oil pump 29 cools and cools the lubricating oil in the oil storage tank through an air-cooled radiator 33 through an oil delivery pipe 30, then delivers the lubricating oil to the cylinder body 1, the air inlet valve 12 and the exhaust valve 13, and delivers the lubricating oil in the crankcase to the oil storage tank through a filter through an oil return pipe 31.

In the present embodiment, the cylinder block 1, the intake valve 12, and the exhaust valve 13 are injection-lubricated, and the crankshaft is splash-lubricated.

In this embodiment, the three-way electric ball valve includes a valve body 24, a valve core 25, a valve core shaft 26 and a motor 28 for driving the valve core 25 to rotate through the valve core shaft 26, the crankshaft 5 is provided with a crankshaft position sensor 35 for detecting a crankshaft phase angle in real time, the valve core shaft 26 is provided with a rotating shaft position sensor 38 for detecting a real-time rotation angle of the valve core in real time, the rotating shaft position sensor 38, the crankshaft position sensor 35 and the motor 28 are electrically connected with a control system, and the control system controls motor actions of the intake valve 12 and the exhaust valve 13 through data of the rotating shaft position sensor 38 and the crankshaft position sensor 35.

In this embodiment, the crankshaft 5 is provided with a signal gear 8 linked with the crankshaft 5, the spool shaft of the three-way electric ball valve is provided with a signal wheel 27 linked with the spool shaft 26, the crankshaft position sensor 35 detects the signal gear 8 in real time, and the rotating shaft position sensor 38 detects the signal wheel 27 in real time.

In this embodiment, the motor 28 drives the valve core 25 to rotate in one direction in the valve body 25, and each stage of control is ensured to be executed in sequence through the rotation in one direction, so as to realize a cyclic process, and make each stage not to jump.

A control method of a high expansion ratio horizontal opposed piston type expansion machine is used for controlling the high expansion ratio horizontal opposed piston type expansion machine, a gear missing position on a signal gear 8 is measured through a crankshaft position sensor 35, a crankshaft rotation angle position and an actual rotation speed of the expansion machine are calculated through a control system, meanwhile, the positions of signal wheels 27 on valve core shafts of an air inlet valve and an air outlet valve are detected through a rotating shaft position sensor 38, and a control command is sent out through the control system to control a motor to control the valve core positions and the pause duration of the air inlet valve and the air outlet valve, so that a crankshaft 5 is driven to rotate to do work by controlling the air inflow and the air exhaust of a first cylinder and a second cylinder.

In this embodiment, the working phase difference between the first cylinder and the second cylinder is 180 degrees, and the specific operation process of the first cylinder and the second cylinder is as follows:

firstly, an air inlet valve controls a first air cylinder to be communicated with a high-pressure working medium, a second air cylinder is not communicated with the high-pressure working medium, the first air cylinder admits air and does work through expansion, meanwhile, an exhaust valve controls the second air cylinder to be communicated with an exhaust system, the first air cylinder is not communicated with the exhaust system, and the second air cylinder is in an exhaust state;

when the control system detects that the crank angle reaches a first set phase, the valve core of the air inlet valve rotates to ensure that the first cylinder and the second cylinder are not communicated with the high-pressure working medium, the air inlet is closed, the working medium in the first cylinder is in a free expansion working state, the second cylinder is still in a continuous exhaust state at the moment, and when the crank angle reaches a second set phase, the exhaust valve controls the first cylinder and the second cylinder to be not communicated with the exhaust system and exhaust is closed;

when the crank angle reaches a third set phase, the valve core of the exhaust valve rotates to enable the first cylinder to be conducted with the exhaust system, the second cylinder to be not conducted with the exhaust system, the first cylinder enters an exhaust state, meanwhile, the valve core of the intake valve rotates to enable the second cylinder to be conducted with the high-pressure working medium, the first cylinder to be not conducted with the high-pressure working medium, at the moment, the second cylinder admits air, the first cylinder is in a continuous exhaust state, and therefore the continuous exhaust of the first cylinder is achieved in a circulating mode, and shaft work is output alternately.

In conclusion, the invention adopts the opposed design of the two cylinders, so the structure is compact, the vehicle-mounted installation is convenient, the air inlet and exhaust mechanism of the traditional piston expander is replaced by the specially-made electric servo ball valve, the mechanism is greatly simplified, the mechanical friction loss is reduced, the air inlet and exhaust are controlled by the control system, the number and the volume of the mechanism are further reduced, and the invention has the advantages of large expansion ratio, few components, compact structure, high heat-power conversion efficiency and the like, and has wider application prospect.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a schematic view of the lubrication system of the present invention.

FIG. 3 is a schematic diagram of a control system according to the present invention.

Fig. 4(a) is a state diagram of one side of the three-way electric ball valve of the present invention being conducted.

Fig. 4(b) is a state diagram of the two sides of the three-way electric ball valve of the invention being non-conductive.

Fig. 4(c) is a state diagram of the other side of the three-way electric ball valve of the invention being conducted.

Fig. 5(a) is a control timing chart of the first cylinder of the invention.

Fig. 5(b) is a control timing chart of the second cylinder of the invention.

In the drawing, 1, a cylinder body, 2, a cylinder cover, 3, a piston head, 4, a connecting rod, 5, a crankshaft, 6, a crankcase, 7, an end cover, 8, a signal gear, 9, a belt pulley, 10, an air inlet branch pipe, 11, an air outlet branch pipe, 12, an air inlet valve, 13, an air outlet valve, 14, a first bolt, 15, a second bolt, 16, a bearing, 17, a first pin, 18, a second pin, 19, a crank, 21, an air inlet, 22, a first air outlet, 23, a second air outlet, 24, a valve body, 25, a valve core, 26, a valve core shaft, 27, a signal wheel, 28, a stepping motor, 29, an oil pump, 30, an oil conveying pipe, 31, an oil return pipe, 32, a filter, 33, an air cooling radiator, 34 and an oil injection.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1 to 3, a high expansion ratio piston type expander comprises an intake valve 12, an exhaust valve 13, a crankshaft 5, and a first cylinder and a second cylinder which are evenly distributed on two sides of the crankshaft, wherein the first cylinder and the second cylinder have the same structure and respectively comprise a cylinder body 1, a cylinder cover 2, a piston head 3 and a connecting rod 4, the cylinder body 1 is cylindrical, and a lubricating oil channel and a plurality of oil holes are arranged inside the cylinder body; the cylinder cover 2 is provided with an air inlet and an air outlet; the cylinder cover is connected with the cylinder body through a first bolt 14, and the sealing surface of the cylinder cover is a metal sealing ring; the crankshaft 5 is arranged in a crankcase 6, the crankcase 6 is cylindrical, the crankcase 6 is formed by butting two semicircular components through flanges, an end cover 7 of the crankcase 6 is connected with the crankcase through a second bolt 15, and a bearing 16 and a sealing element are arranged on the end cover 7; the main shaft of the crankshaft extends out of the end cover 7 at one side, and a signal gear 8 and a power transmission belt pulley 9 are arranged on the main shaft of the crankshaft; the cylinder body 1 and the crankcase 6 are welded into a whole; the piston head 3 is arranged in the cylinder body 1, the piston head 3 is connected with the crankshaft 5 through the connecting rod 4, the top of the piston head 3 is a plane, two oil rings and one gas ring are arranged on the contact surface of the piston head 3 and the cylinder body 1, and the piston head 3 is connected with the small end of the connecting rod 4 through the first pin 17; the big end of the connecting rod 4 is connected with a crank 19 on the crank shaft 5 through a second pin 18,

the utility model discloses a pneumatic valve, including admission valve 12 and discharge valve 13, connecting rod drive bent axle 5 rotation power of three-way electric ball valve, the connecting rod of first cylinder and second cylinder drives the rotation of bent axle jointly, the cylinder cap 2 of first cylinder respectively with the one end welding of branch pipe 10 and branch pipe 11 that admits air, the other end of branch pipe 10 and branch pipe 11 that admits air of first cylinder respectively with an air outlet 22 of admission valve 12 and a gas inlet intercommunication of discharge valve 13, the cylinder cap 2 of second cylinder also respectively with the one end welding of branch pipe 10 and branch pipe 11 that admits air, the other end of branch pipe 10 and branch pipe 11 that admits air of second cylinder respectively with another air outlet 23 of admission valve 12 and another air inlet intercommunication of discharge valve 13, the air inlet 21 and the high pressure working medium export intercommunication of admission valve 12, discharge valve 13's.

The embodiment also comprises a lubricating system, wherein the lubricating system comprises an oil pump 29, an oil delivery pipe 30, an oil return pipe 31, a filter 32, an air-cooled radiator 33 and an oil filling port 34; the oil pump 29 cools and cools lubricating oil in the oil storage tank through an air-cooled radiator 33 through an oil delivery pipe 30, then delivers the lubricating oil to the cylinder body 1, the air inlet valve 12 and the exhaust valve 13, and delivers the lubricating oil in the crankcase to the oil storage tank through a filter through an oil return pipe 31, wherein the cylinder body 1, the air inlet valve 12 and the exhaust valve 13 adopt injection lubrication, and the crankshaft adopts splash lubrication.

As shown in fig. 4(a), 4(b), and 4(c), the three-way electric ball valve includes a valve body 24, a valve core 25, a valve core shaft 26, and a motor 28 for driving the valve core 25 to rotate through the valve core shaft 26, the crankshaft 5 is provided with a crankshaft position sensor 35 for detecting a crankshaft phase angle in real time, the valve core shaft 26 is provided with a rotating shaft position sensor 38 for detecting a real-time rotating angle of the valve core in real time, the rotating shaft position sensor 38, the crankshaft position sensor 35, and the motor 28 are electrically connected to a control system, the control system controls motor actions of the intake valve 12 and the exhaust valve 13 through data of the rotating shaft position sensor 38 and the crankshaft position sensor 35, the crankshaft 5 is provided with a signal gear 8 linked with the crankshaft 5, the valve core shaft of the three-way electric ball valve is provided with a signal wheel 27 linked with the valve core shaft 26, and the crankshaft position, the rotating shaft position sensor 38 detects the signal wheel 27 in real time, and the motor 28 drives the valve core 25 to rotate in the valve body 25 in a single direction.

The present invention also includes a method of controlling a high expansion ratio horizontally opposed-piston expander for controlling the high expansion ratio horizontally opposed-piston expander,

the gear missing position on the signal gear 8 is measured by the crankshaft position sensor 35, the control system calculates the crankshaft angle position and the actual rotating speed of the expansion machine, meanwhile, the rotating shaft position sensor 38 detects the positions of the signal wheels 27 on the valve core shafts of the air inlet valve and the exhaust valve, and the control system sends out a control command to control the motor to control the valve core positions and the pause duration of the air inlet valve and the exhaust valve, so that the crankshaft 5 is driven to rotate to do work by controlling the air inflow and the air exhaust of the first cylinder and the second cylinder.

As shown in fig. 5(a), a cycle of the present application is set to 360 degrees, an intake advance angle is a, an exhaust advance angle is B, stages 1A to 1B of the first cylinder are intake stages, stages 1B to 1C are free expansion stages, stages 1C to 1D are exhaust stages, an intake start position 1A of the intake stage is between 350 degrees and 355 degrees, an intake end position 1B of the intake stage is between 20 degrees and 30 degrees, an exhaust start position 1C of the exhaust stage is between 170 degrees and 180 degrees, and an exhaust end position 1D of the exhaust stage is between 330 degrees and 345 degrees; as shown in fig. 5(B), the first cylinder 2A-2B stage is an intake stage, the 2B-2C stage is a free expansion stage, the 2C-2D stage is an exhaust stage, the working phases of the first cylinder and the second cylinder are 180 degrees out of phase, and the first cylinder and the second cylinder can be adjusted within a range according to actual conditions.

The following describes the operation of the first and second cylinders in detail:

as shown in fig. 4(a), firstly, the air inlet valve controls the first air cylinder to be communicated with the high-pressure working medium, the second air cylinder is not communicated with the high-pressure working medium, the first air cylinder admits air and expands to do work, meanwhile, the exhaust valve controls the second air cylinder to be communicated with the exhaust system, the first air cylinder is not communicated with the exhaust system, and the second air cylinder is in an exhaust state;

when the control system detects that the crank angle reaches a first set phase, as shown in fig. 4(b), the valve core of the air inlet valve rotates to ensure that the first cylinder and the second cylinder are not communicated with the high-pressure working medium, the air inlet is closed, the working medium in the first cylinder is in a free expansion working state, the second cylinder is still in a continuous exhaust state at the moment, and when the crank angle reaches a second set phase, the exhaust valve controls the first cylinder and the second cylinder to be not communicated with the exhaust system, and the exhaust is closed;

when the crank angle reaches the third set phase, as shown in fig. 4(c), the valve core of the exhaust valve rotates to make the first cylinder and the exhaust system both conduct, the second cylinder and the exhaust system do not conduct, the first cylinder enters the exhaust state, meanwhile, the valve core of the intake valve rotates to make the second cylinder and the high-pressure working medium conduct, the first cylinder and the high-pressure working medium do not conduct, at the moment, the second cylinder admits air, the first cylinder is in the continuous exhaust state, and therefore the operation is circulated, and the shaft work is alternately output.

The above description is only illustrative of the specific embodiments of the present invention, and the scope of the present invention is not limited thereto. All equivalent changes and modifications made according to the claims and the content of the specification of the present invention are within the protection scope of the present invention.