A Multi-Stage Stirling Cycle Machine And A Steady-State Operating Parameter Control Method Therefor

Abstract

The present invention relates to a multi-stage Stirling cycle machine and a steady-state operating parameter control method therefor. In the Stirling cycle machine, a mechanical energy input piston, a mechanical energy transfer double-acting free piston and a mechanical energy output piston constitute a plurality of Stirling working units which are arranged in stages. The mechanical energy input piston is connected to a mechanical energy input apparatus, and the mechanical energy output piston is connected to a mechanical energy output apparatus. When the Stirling cycle machine in the present invention is used as an engine, a relatively small amount of mechanical energy is input into a mechanical energy input piston in a set of pistons, the mechanical energy is amplified by a multi-stage Stirling unit, and a relatively large amount of mechanical energy is then output by a mechanical energy output piston. In the present invention, the required piston motion mode is realized by means of parameter calculation, selection and design, such that the multi-stage Stirling cycle machine can adapt to changes in an input condition and adjust an output power as required. The device in the present invention has a simple structure, a good adjustment performance, a small mechanical loss and a small deadvolume, is suitable for use with a large-diameter piston, and can be widely applied to waste heat power generation and distributed energy and renewable energy power generation.

Claims

1.-10. (canceled)

11. A multi-stage Stirling cycle machine, which comprises at least one set of piston working units, wherein said one set of piston working units comprises: a first cylinder and one mechanical energy input piston that is axially movable in the first cylinder; a second cylinder and one mechanical energy transfer double-acting free piston that is axially movable in the second cylinder; a last stage cylinder and one mechanical energy output piston that is axially movable in the last stage cylinder; the first cylinder is connected to the second cylinder in the axial direction through a first cooler, a first regenerator and a first heater, the second cylinder is connected to the last stage cylinder in the axial direction through a second cooler, a second regenerator, and a second heater, constituting a Stirling working unit with two stages, the mechanical energy transfer double-acting free piston is input the mechanical energy from the connected one stage Stirling working unit, in addition to overcoming the mechanical loss of the reciprocating motion of the piston and the working gas, all the mechanical energy is output to the connected next stage Stirling working unit during a complete operating period, realizing that the mechanical energy transfer double-acting free piston can only reciprocate under the action of the pressure change of the working gas of the Stirling working unit on both sides so as to achieve the purpose of canceling the piston rod apparatus.

12. The multi-stage Stirling cycle machine according to claim 11, wherein a mechanical energy input apparatus is arranged at one end of the multi-stage Stirling cycle machine, and the mechanical energy input apparatus is connected to the mechanical energy input piston and drives the mechanical energy input piston to act, a mechanical energy output apparatus is arranged at the other end of the multi-stage Stirling cycle machine, and the mechanical energy output apparatus is connected to the mechanical energy output piston.

13. The multi-stage Stirling cycle machine according to claim 11, wherein one or more cylinders are arranged in the axial direction between the second cylinder and the last stage cylinder, and each cylinder comprises one mechanical energy transfer double-acting free piston that can move in the axial direction, the cylinders are connected in the axial direction through a cooler, a regenerator and a heater so that the multi-stage Stirling cycle machine is a Stirling cycle machine with at least three stages.

14. The multi-stage Stirling cycle machine according to claim 12, wherein the mechanical energy input apparatus is selected from one or a combination of an electric motor, cyclically changing gas pressure difference, cyclically changing liquid pressure difference, a Stirling engine, connecting rod with mechanical energy output piston.

15. The multi-stage Stirling cycle machine according to claim 12, wherein the mechanical energy output apparatus is selected from one or a combination of a power generator, cyclically changing gas pressure difference, cyclically changing liquid pressure difference, a Stirling heat pump, connecting rod with mechanical energy input piston.

16. A steady-state operating parameter control method of the multi-stage Stirling cycle machine according to claim 11, wherein the parameter adjustment is carried out according to the following steps: (1) selecting the amplitude of the piston and the phase angle between the pistons, and the phase angle between the pistons should not exceed 75°; (2) selecting the average length of the back pressure chamber of the mechanical energy input piston and the average length of the back pressure chamber of the mechanical energy output piston, the average length should be such that the volume of the back pressure chamber is 3-8 times the volume of the adjacent Stirling unit; (3) selecting the parameters of the cooler, regenerator and heater and calculating the volume of the cooler, regenerator and heater corresponding to per unit area of the piston; (4) calculating and determining average pressure, area of each piston, piston mass of each Stirling unit by using forced vibration equations; and (5) adjusting the operating parameters of the multi-stage Stirling engine.

17. The method according to claim 16, wherein the step (4) calculates and determines average pressure, area of each piston, piston mass of each Stirling unit according to the following process: a. initially selecting the number of stages of the multi-stage Stirling cycle machine, the average pressure of each closed space and the area of each piston according to the mode that the area of the piston in the expansion chamber of the engine unit is larger than that of the piston in the compression chamber of the engine unit; b. under the condition that the area of the mechanical energy output piston remains unchanged, adjusting the area of other pistons to make that the resultant force acting on each mechanical energy transfer double-acting free piston is 0 by using the equivalent linear stiffness and damping calculation when this piston runs to the equilibrium position; c. calculating the driving force of the mechanical energy input apparatus and the damping of the mechanical energy output apparatus according to the condition that the resultant force acting on this piston is 0 by using the equivalent linear stiffness and damping calculation when the piston runs to the equilibrium position; d. calculating the mass of each piston according to the resultant force of the acting force calculated by using the equivalent linear stiffness and the acceleration of the piston when each piston runs to the maximum displacement; e. for vertically arranged multi-stage Stirling engines, adjusting the average pressure of each Stirling working unit and back pressure chamber according to the mass of each piston; f. repeating the calculation from step b to step e until the ideal calculation result is obtained; g. calculating mechanical energy input power and mechanical energy output power; h. calculating the power loss caused by the efficiency of the mechanical energy input apparatus, and judging whether the ratio of the power loss caused by the efficiency of the mechanical energy input apparatus to the total output power meets the requirement, generally, in order to keep the power loss caused by the efficiency of the mechanical energy input apparatus within 5% of the total output power, the mechanical energy output power is required to be more than 10 times the mechanical energy input power; and i. if the ratio of the power loss caused by the efficiency of the mechanical energy input apparatus to the total output power does not meet the requirement, increasing the number of stages of the multi-stage Stirling engine and repeating the above calculations.

18. The method according to claim 16, wherein the set of forced vibration equations of Stirling cycle machine in step (4) are:
m.sub.1x.sub.1″+c.sub.1x.sub.1′+(k.sub.10+k.sub.12)x.sub.1−k.sub.21x.sub.2=q sin(ωt)
m.sub.2x.sub.2″+c.sub.2x.sub.2′−k.sub.12x.sub.1+(k.sub.21+k.sub.23)x.sub.2−k.sub.32x.sub.3=0
m.sub.ix.sub.i″+c.sub.ix.sub.i′−k.sub.(i−1)ix.sub.(i−1)+(k.sub.i(i−1)+k.sub.i(i+1))x.sub.i−k.sub.(i+1)ix.sub.(i+1)=0
m.sub.nx.sub.n″+c.sub.nx.sub.n′−k.sub.(n−1)nx.sub.(n−1)+(k.sub.n(n−1)+k.sub.n(n+1))x.sub.n=0 wherein: m.sub.1, m.sub.2, . . . , m.sub.i, . . . , m.sub.n are the mass of per unit area of the mechanical energy input piston, each mechanical energy transfer double-acting free piston and the mechanical energy output piston; ω is the circular frequency of the driving force of the mechanical energy input apparatus; q is the maximum of the force of the mechanical energy input apparatus acting on the unit mechanical energy input piston; t is time; x.sub.1, x.sub.2, . . . , x.sub.i, . . . , x.sub.n are the displacements of the mechanical energy input piston, each mechanical energy transfer double-acting free piston and the mechanical energy output piston, which are functions of time t; x.sub.1′, x.sub.2′, . . . , x.sub.i′, . . . , x.sub.n′ are the speeds of the mechanical energy input piston, each mechanical energy transfer double-acting free piston and the mechanical energy output piston; x.sub.1″, x.sub.2″, . . . , x.sub.i″, . . . , x.sub.n″ are the accelerations of the mechanical energy input piston, each mechanical energy transfer double-acting free piston and the mechanical energy output piston; c.sub.1, c.sub.2, . . . , c.sub.i, . . . , c.sub.n are the equivalent damping of per unit area of piston of the mechanical energy input piston, each mechanical energy transfer double-acting free piston and the mechanical energy output piston; and k.sub.10, k.sub.12 are changes of pressure in the closed space on the upper and lower sides of the piston caused by the unit displacement of x.sub.1, k.sub.21, k.sub.23, k.sub.32, k.sub.34 . . . and so on.

19. The method according to claim 17, wherein the specific method of step (5) is as follows: A. adjusting the mechanical energy output power by adjusting the mechanical energy input power; B. adjusting the operating frequency requires adjusting the average pressure of the working gas at the same time; C. adjusting the phase angle between the pistons requires adjusting the volume of back pressure chamber of the mechanical energy input piston and the volume of back pressure chamber of the mechanical energy output piston at the same time; D. when the ratio of the absolute temperature of the heat source and the cold source increases, in order to maintain the output power unchanged, the mechanical energy input power needs to be reduced; and E. when the ratio of the absolute temperature of the heat source and the cold source decreases, in order to maintain the input power unchanged, the mechanical energy output power needs to be reduced.

20. A usage of a multi-stage Stirling cycle machine according to claim 11, wherein the multi-stage Stirling cycle machine is used for waste heat power generation, renewable energy power generation, building a distributed solar energy cogeneration apparatus and a small-scale cogeneration apparatus, microgrid power supply.

Description

DRAWINGS

[0085] FIG. 1 is the schematic diagram of the structure of the Stirling engine in the prior art;

[0086] FIG. 2 is the schematic diagram of the structure of the two-stage Stirling cycle machine according to the present invention;

[0087] FIG. 3 is the schematic diagram of the multi-stage Stirling cycle machine according to the present invention.

[0088] Wherein, 1—mechanical energy input apparatus, 2—mechanical energy input piston, 3—first cooler, 4—first regenerator, 5—first heater, 3′—second cooler, 4′—second regenerator, 5′—second heater, 6—mechanical energy transfer double—acting free piston, 7—mechanical energy output piston, 8—mechanical energy output apparatus; 101—first cylinder, 102—second cylinder, 103—last stage cylinder; 001—first—stage Stirling working unit, 002—second—stage Stirling working unit, 003—third-stage Stirling working unit, 004—fourth-stage Stirling working unit, 005—fifth-stage Stirling working unit, 006—sixth-stage Stirling working unit, 007—seventh-stage Stirling working unit.

DETAILED DESCRIPTION

Embodiment 1

[0089] A multi-stage Stirling cycle machine (as shown in FIG. 2), a mechanical energy input apparatus 1 is arranged at one end thereof, the mechanical energy input apparatus 1 is connected to a mechanical energy input piston 2, and the mechanical energy input piston 2 is arranged in a first cylinder 101; the first cylinder 101 is connected to a second cylinder 102 through a first cooler 3, a first regenerator 4 and a first heater 5, a mechanical energy transfer double-acting free piston 6 is arranged in the second cylinder 102; the second cylinder 102 is connected to a last stage cylinder 103 through a second cooler 3′, a second regenerator 4′ and a second heater 5′, a mechanical energy output piston 7 is arranged in the last stage cylinder 103; the other end of the mechanical energy output piston 7 is connected to the mechanical energy output apparatus 8. One closed working space is formed between the mechanical energy input piston 2 located in the first cylinder 101 and the mechanical energy transfer double-acting free piston 6 located in the second cylinder 102, constituting a first-stage Stirling working unit; the mechanical energy transfer double-acting free piston 6 located in the second cylinder 102 and the mechanical energy output piston 7 located in the last stage cylinder 103 form another closed working space, constituting a second-stage Stirling working unit. The mechanical energy input apparatus 1 is selected from various apparatuses that can drive the mechanical energy input piston to reciprocate, such as an electric motor, cyclically changing gas pressure difference, cyclically changing liquid pressure difference, a Stirling engine, etc., or a combination of several modes. The mechanical energy output apparatus is selected from various apparatuses for the output or utilization of mechanical energy, which can drive the mechanical energy output piston to reciprocate, such as power generator, cyclically changing gas pressure difference, cyclically changing liquid pressure difference, Stirling heat pumps, etc., or a combination of several modes. The above structures form one Stirling cycle machine of Stirling working units with two stages.

Embodiment 2

[0090] A multi-stage Stirling cycle machine, a mechanical energy input apparatus 1 is arranged at one end thereof, the mechanical energy input apparatus 1 is connected to a mechanical energy input piston 2, and the mechanical energy input piston 2 is arranged in a first cylinder 101; the first cylinder 101 is connected to a second cylinder 102 through a first cooler 3, a first regenerator 4 and a first heater 5, a mechanical energy transfer double-acting free piston 6 is arranged in the second cylinder 102; the second cylinder 102 is connected to a third cylinder through a second cooler 3′, a second regenerator 4′ and a second heater 5′, a mechanical energy transfer double-acting free piston is arranged in the third cylinder; the third cylinder is connected to a last stage cylinder 103 through a cooler, a regenerator and a heater, a mechanical energy output piston 7 is arranged in the last stage cylinder 103; the other end of the mechanical energy output piston 7 is connected to the mechanical energy output apparatus 8. One closed working space is formed between the mechanical energy input piston 2 located in the first cylinder 101 and the mechanical energy transfer double-acting free piston 6 located in the second cylinder 102, constituting a first-stage Stirling working unit; the mechanical energy transfer double-acting free piston 6 located in the second cylinder 102 and the mechanical energy transfer double-acting free piston located in the third cylinder form one closed working space, constituting a second-stage Stirling working unit; the mechanical energy transfer double-acting free piston located in the third cylinder and the mechanical energy output piston 7 located in the last stage cylinder 103 form another closed working space, constituting a third-stage Stirling working unit. The mechanical energy output piston at the last stage Stirling working unit is connected to the mechanical energy output apparatus. The mechanical energy input apparatus is selected from various apparatuses that can drive the mechanical energy input piston to reciprocate, such as an electric motor, cyclically changing gas pressure difference, cyclically changing liquid pressure difference, a Stirling engine, etc., or a combination of several modes. The mechanical energy output apparatus is selected from various apparatuses for the output or utilization of mechanical energy, which can drive the mechanical energy output piston to reciprocate, such as power generator, cyclically changing gas pressure difference, cyclically changing liquid pressure difference, Stirling heat pumps, etc., or a combination of several modes. The above structures form one Stirling cycle machine system with three stages.

Embodiment 3

[0091] A multi-stage Stirling engine that utilizes the waste heat of exhaust of an internal combustion engine. Biogas power generation generally uses an internal combustion engine, the exhaust temperature of the internal combustion engine is about 500° C., it is generally used for the thermal insulation of biogas tanks, due to the low waste heat required for thermal insulation in spring, summer and autumn every year, it is not fully utilized. In this embodiment, the exhaust is used to heat the temperature of the heat transfer oil from 300° C. to 350° C. as the heat source of the multi-stage Stirling engine, so as to realize the efficient utilization of the exhaust heat. The cold source adopts the thermal insulation water of the biogas tank, and the temperature of the thermal insulation water is heated from 50° C. to 90° C. to realize the utilization of low-temperature waste heat. The multi-stage Stirling engine of the present embodiment is shown in FIG. 3, the vertical arrangement is adopted, the mechanical energy input piston is arranged at the uppermost end, the mechanical energy output piston is arranged at the lowermost end, and mechanical energy transfer double-acting free pistons with six stages are arranged in between, forming Stirling engine with seven stages (001-007 in FIG. 3). The diameter of the mechanical energy input piston is 37.2 cm, the diameters of the mechanical energy transfer double-acting free pistons from top to bottom are 42.7 cm, 49.3 cm, 57.4 cm, 67.3 cm, 80 cm, 96 cm, and the diameter of the mechanical energy output piston is 120 cm. The mechanical energy input apparatus adopts a linear motor, and the mechanical energy output apparatus adopts a linear generator. The average pressure of the back pressure chamber of the mechanical energy input piston is 4 MPa, the average pressure of the gas in each closed space is gradually increased according to the weight of the piston per unit area, and the weight of each piston is borne by the pressure difference. The heat source medium passes through the heaters of the lower Stirling engine units with five stages in series from bottom to top, and then passes through the heaters of the upper Stirling engine units with two stages in parallel. The cold source is connected in a similar mode.

[0092] Operation mode: turn on the heat source and the cold source, adjust each piston to the equilibrium position, and the mechanical energy input apparatus applies periodic driving force with 30 HZ sinusoidal variation to the mechanical energy input piston, the mechanical energy input piston is input with a power of 27 kW for one cycle, and then the mechanical energy is input stably with a power of 38 kW, after 2 to 3 cycles, the mechanical energy output piston stably outputs a power of 380 kW, and the amplitude of each piston is about 2 cm.

[0093] Comparison solution is designed using the described prior art or other technologies similar thereto. Calculated according to the output power of per unit piston scavenging volume is the same as this embodiment, using the same piston amplitude to achieve the same effective output power, the comparison solution uses 600 double-acting pistons with a diameter of 7.7 cm.

[0094] The total area of the piston in this embodiment is 34147 cm.sup.2, the comparison solution is 27949 cm.sup.2, and the total area of the piston in this embodiment is 122% of the comparison solution; the total perimeter of the piston in this embodiment is 1726 cm, the comparison solution is 14514 cm, and the total perimeter of the piston in this embodiment is 12% of the comparison solution.

[0095] Although the piston area in this embodiment is slightly larger than that of the comparison solution, however, the surface processing area of the cylinder and piston is only 12% of the comparison solution; the gap between the piston and the cylinder of this embodiment is about 10 times that of the prior art, so that the machining accuracy requirement of this embodiment is lower than that of the prior art; in this embodiment, there are no parts with complicated shapes such as gas collecting pipes; this embodiment does not provide large springs. For the above reasons, the processing cost of this embodiment is much lower than that of the comparison solution.

[0096] The total length of the sealing ring in this embodiment is 12% of the prior art; the number of piston rods passing out of the cylinder is 2 in this embodiment, and 600 in the comparison solution. For the above reasons, the mechanical loss due to sealing in this embodiment is much lower than that in the prior art.

[0097] In this embodiment, one motor with 38 kW is used as the mechanical energy input apparatus, and one generator with 380 kW is used as the mechanical energy output apparatus; the comparison technology requires 600 generators with 0.57 kW or 100 generators with 3.42 kW and 100 sets of rotating mechanisms such as swash plates, etc. The above reasons make the cost of the motor and the supporting connecting mechanism in this embodiment far lower than that of the comparison solution.

[0098] In this embodiment, the stroke of each piston and the stroke of the mechanical energy input piston have a relatively fixed ratio relationship, and this ratio is less affected by external disturbances, the operation of this embodiment can be reliably controlled by adjusting the mechanical energy input apparatus, and the stability and adjustment performance of the operation of this embodiment are far superior to those of the prior art.

[0099] In this embodiment, the low-temperature waste heat meets the thermal insulation requirement of the biogas tank, and the total heating capacity of the thermal insulation water decreases by about 10%, the operating power of this embodiment needs to be reduced in order to ensure the heating capacity of the thermal insulation water only during the 20% or so of the year when the temperature is the lowest. Using this embodiment, the power generation of biogas power generation can be increased by more than 10%.

Embodiment 4

[0100] A multi-stage Stirling engine for realizing the combined supply of distributed electricity and hot water by using solar thermal energy. In factories with hot water needs, solar concentrators are installed on the factory floor to collect solar heat as a heat source for the multi-stage Stirling engine, so that electricity and hot water can be used nearby. Setting up a thermal energy storage system so that the power generation time and power can be adjusted as needed. The structure and parameters of the multi-stage Stirling engine are the same as the embodiment 3, and the following three operating modes are adopted as required:

[0101] 1. The combined supply mode of electricity and hot water, the operation mode is similar to that of the embodiment 3;

[0102] 2. The mode of pure power generation, in the time period when hot water is not needed, the cold source is changed to cooling water with 30° C., due to the increase in temperature difference, the mechanical energy input power is adjusted to 20 kW, and the mechanical energy output power is 380 kW.

[0103] 3. The mode of emergency power generation, when the external power supply of the factory fails to provide normal power supply and the thermal energy storage is insufficient, the thermal energy storage potential can be further tapped by reducing the temperature of the heat source to achieve continuous power supply and ensure the basic power supply requirements such as the safe shutdown of the main equipment of the factory, the output power decreases as the temperature of the heat source decreases.

[0104] Compared with the conventional solar thermal power generation, the main advantages of this embodiment include: increasing the profit of hot water; reducing the loss of long-distance transmission of electricity and equipment investment; the heat transfer medium transmission pipeline is short, which reduces the investment and heat dissipation loss; replacing emergency power sources such as diesel generators, etc. The overall benefit of this embodiment is obvious.