阅读说明：本技术 一种多级斯特林机及其稳态运行参数调控方法 (Multi-stage Stirling engine and steady-state operation parameter regulation and control method thereof ) 是由 王利 于 2020-07-06 设计创作，主要内容包括：本发明涉及一种多级斯特林机及其稳态运行参数调控方法,该斯特林机由机械能输入活塞、机械能传递双作用自由活塞、机械能输出活塞构成分级布置的多个斯特林工作单元。机械能输入活塞连接机械能输入装置,机械能输出活塞连接机械能输出装置。本发明的斯特林机作为发动机时,通过向一组活塞中的机械能输入活塞输入一个较小的机械能,机械能通过多级斯特林单元放大后由机械能输出活塞输出较大的机械能。本发明通过参数计算、选择、设计实现了所需要的活塞运动方式,使多级斯特林机能适应输入条件的改变和按需要调整输出功率。本发明设备结构简单、调节性好、机械损失小、无效容积小,适合采用大直径活塞,可广泛用于余热发电、分布式能源和可再生能源发电。(The invention relates to a multi-stage Stirling engine and a steady-state operation parameter regulating and controlling method thereof. The mechanical energy input piston is connected with the mechanical energy input device, and the mechanical energy output piston is connected with the mechanical energy output device. When the Stirling engine is used as an engine, a small mechanical energy is input into the mechanical energy input piston in the group of pistons, and the mechanical energy is amplified by the multi-stage Stirling unit and then is output by the mechanical energy output piston to output a large mechanical energy. The invention realizes the required piston motion mode through parameter calculation, selection and design, so that the multi-stage Stirling engine can adapt to the change of input conditions and adjust the output power as required. The device has the advantages of simple structure, good adjustability, small mechanical loss and small invalid volume, is suitable for adopting the large-diameter piston, and can be widely used for waste heat power generation, distributed energy and renewable energy power generation.)

1. A multi-stage stirling machine comprising at least one set of piston operating units, the set of piston operating units comprising:

(a) a first cylinder (101) and a mechanical energy input piston (2) axially movable within the first cylinder (101);

(b) a second cylinder (102), and a mechanical energy transmitting double acting free piston (6) axially movable within the second cylinder (102);

(c) a last stage cylinder (103), and a mechanical energy output piston (7) axially movable within the last stage cylinder (103);

the first cylinder (101) is communicated with the second cylinder (102) along the axial direction through the first radiator (3), the first heat regenerator (4) and the first heat absorber (5), and the second cylinder (102) is communicated with the last-stage cylinder (103) along the axial direction through the second radiator (3 '), the second heat regenerator (4 ') and the second heat absorber (5 '), so that a two-stage Stirling working unit is formed.

2. A multi-stage stirling machine according to claim 1, wherein a mechanical energy input device (1) is provided at one end of the multi-stage stirling machine, the mechanical energy input device (1) being connected to and driving a mechanical energy input piston (2), and a mechanical energy output device (8) is provided at the other end of the multi-stage stirling machine, the mechanical energy output device (8) being connected to the mechanical energy output piston (7).

3. A stirling machine according to claim 1 or 2, wherein one or more cylinders are axially disposed between the second cylinder (102) and the last cylinder (103), each cylinder comprising an axially movable mechanical energy transfer double acting free piston, the cylinders being axially connected by a heat sink, regenerator and heat sink, such that the stirling machine is a stirling machine having more than three stages.

4. A multi-stage stirling machine according to claim 2, wherein the mechanical energy input device (1) is selected from one or a combination of an electric motor, a cyclically varying gas pressure differential, a cyclically varying liquid pressure differential, a stirling engine, and a connecting rod between the mechanical energy output pistons.

5. A multi-stage stirling machine according to claim 2, wherein the mechanical energy output device (8) is selected from one or a combination of a generator, a cyclically varying gas pressure differential, a cyclically varying liquid pressure differential, a stirling heat pump, and a connecting rod between the mechanical energy input pistons.

6. The method for regulating and controlling stable operation parameters of a multi-stage stirling machine according to any one of claims 1 to 5, wherein the parameter regulation is performed according to the following steps:

(1) selecting the amplitude of the pistons and the phase angle between the pistons, wherein the phase angle between the pistons is not more than 75 degrees;

(2) selecting the average length of the back pressure cavity of the mechanical energy input piston and the mechanical energy output piston, wherein the average length is suitable for enabling the volume of the back pressure cavity to be 3-8 times of the volume of the adjacent Stirling unit;

(3) selecting parameters of a radiator, a heat regenerator and a heat absorber, and calculating the volumes of the radiator, the heat regenerator and the heat absorber corresponding to the unit piston area;

(4) calculating and determining the average pressure of each Stirling unit, the area of each piston and the mass of each piston by using a forced vibration equation set;

(5) the operating parameters of the multi-stage stirling engine of the present invention are adjusted.

7. The method of claim 6, wherein step (4) comprises the steps of calculating and determining the average pressure of each Stirling unit, the area of each piston, and the mass of each piston according to the following procedures:

a. preliminarily selecting the number of stages of the multi-stage Stirling engine, the average pressure of each closed space and the area of each piston according to the mode that the area of the piston of the expansion cavity of the engine unit is larger than that of the piston of the compression cavity;

b. under the condition that the area of the mechanical energy output piston is not changed, the areas of other pistons are adjusted to enable the resultant force, which is calculated by utilizing equivalent linear rigidity and damping and acts on the double-acting piston when each mechanical energy transmission double-acting piston operates to a balance position, to be 0;

c. calculating the driving force of the mechanical energy input device and the damping of the mechanical energy output device according to the condition that the resultant force acting on the piston is 0 calculated by utilizing equivalent linear rigidity and damping when the piston runs to a balance position;

d. calculating the mass of each piston according to the resultant force of the acting forces calculated by using the equivalent linear stiffness when each piston runs to the maximum displacement and the acceleration of the piston;

e. for a multi-stage Stirling engine which is vertically arranged, the average pressure of each Stirling working unit and the back pressure cavity is adjusted according to the mass of each piston;

f. repeating the calculation from b to e until an ideal calculation result is obtained;

g. calculating mechanical energy input power and mechanical energy output power;

h. calculating power loss caused by the efficiency of the mechanical energy input device, and judging whether the proportion of the power loss caused by the efficiency of the mechanical energy input device to the total output power meets the requirement or not, wherein the mechanical energy output power is required to reach more than 10 times of the mechanical energy input power in order to control the power loss caused by the efficiency of the mechanical energy input device within 5% of the total output power under the general condition;

i. if the ratio of the power loss caused by the efficiency of the mechanical energy input device to the total output power does not meet the requirement, the number of stages of the multi-stage Stirling engine is increased, and the calculation is repeated.

8. The method of claim 6, wherein the system of forced stirling machine vibration equations in step (4) is:

m₁x₁”+c₁x₁’+(k₁₀+k₁₂)x₁-k₂₁x₂＝qsin(ωt)

m₂x₂”+c₂x₂’-k₁₂x₁+(k₂₁+k₂₃)x₂-k₃₂x₃＝0

……

m_ix_i”+c_ix_i’-k_(i-1)ix_(i-1)+(k_i(i-1)+k_i(i+1))x_i-k_(i+1)ix_(i+1)＝0

……

m_nx_n”+c_nx_n’-k_(n-1)nx_(n-1)+(k_n(n-1)+k_n(n+1))x_n＝0

wherein m is₁、m₂、…、m_i、…、m_nThe unit area mass of the piston (2) for inputting mechanical energy, each mechanical energy transmission double-acting free piston and the mechanical energy output piston (7);

omega is the circular frequency of the driving force of the mechanical energy input device;

q is the maximum value of the acting force of the mechanical energy input device acting on the unit mechanical energy input piston;

t is time;

x₁、x₂、…、x_i、…、x_nthe displacement of the double-acting free piston for mechanical energy input piston (2), each mechanical energy transmission and the mechanical energy output piston (7) is a function of time t;

x₁’、x₂’、…、x_i’、…、x_nthe speed of a mechanical energy input piston (2), each mechanical energy transmission double-acting free piston and a mechanical energy output piston (7) is calculated;

x₁”、x₂”、…、x_i”、…、x_nthe acceleration of a mechanical energy input piston (2), each mechanical energy transmission double-acting free piston and a mechanical energy output piston (7) is obtained;

c₁、c₂、…、c_i、…、c_nequivalent unit piston area damping for a mechanical energy input piston (2), each mechanical energy transfer double-acting free piston and a mechanical energy output piston (7);

k₁₀、k₁₂is x₁The pressure change of the closed spaces at the upper side and the lower side of the piston caused by unit displacement, k₂₁、k₂₃、k₃₂、k₃₄… … and so on.

9. The method of claim 7, 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 a back pressure cavity of the mechanical energy input piston and the volume of a back pressure cavity of the mechanical energy output piston at the same time;

D. when the ratio of the absolute temperatures of the heat source and the cold source is increased, the input power of mechanical energy needs to be reduced to maintain the output power unchanged;

when the ratio of the absolute temperatures of the heat source and the cold source is reduced, the mechanical energy input power needs to be reduced in order to maintain the input power unchanged.

10. Use of a multi-stage stirling machine according to claims 1 to 5, wherein the multi-stage stirling machine is used for cogeneration, renewable energy generation, construction of distributed solar cogeneration, small cogeneration, micro grid power supply.

Technical Field

The invention belongs to the field of Stirling machines, and particularly relates to a multi-stage Stirling machine and a steady-state operation parameter regulating and controlling method thereof.

Background

Disclosure of Invention

The invention aims to research and design a Stirling engine which is simple in structure, convenient to control, strong in adjustability and anti-interference capability and suitable for large-scale operation. The concrete structure is as follows:

a multi-stage Stirling engine at least comprises a group of pistons and cylinders, wherein the group of pistons comprises a mechanical energy input piston, more than one mechanical energy transmission double-acting free piston and a mechanical energy output piston, and the group of pistons form more than two stages of Stirling working units.

Specifically, the invention relates to a multi-stage Stirling engine, which comprises at least one group of piston working units, wherein the group of piston working units comprises:

(a) a first cylinder 101, and one mechanical energy input piston 2 axially movable in the first cylinder 101;

(b) a second cylinder 102, and a mechanical energy transmitting double acting free piston 6 axially movable within the second cylinder 102;

(c) a last stage cylinder 103, and a mechanical energy output piston 7 axially movable in the last stage cylinder 103;

the first cylinder 101 is axially communicated with the second cylinder 102 through the first radiator 3, the first regenerator 4 and the first heat absorber 5, and the second cylinder 102 is axially communicated with the last-stage cylinder 103 through the second radiator 3 ', the second regenerator 4 ', the second heat absorber 5 ' to form a two-stage Stirling working unit.

Further, a mechanical energy input device 1 is arranged at one end of the multi-stage Stirling engine, and the mechanical energy input device 1 is connected with a mechanical energy input piston 2; and a mechanical energy output device 8 is arranged at the other end of the multi-stage Stirling engine, and the mechanical energy output device 8 is connected with a mechanical energy output piston 7.

Furthermore, the lower end of the second cylinder 102 is connected with at least one mechanical energy transmission double-acting free piston and cylinder which form a Stirling working unit through a radiator, a heat regenerator and a heat absorber, and a mechanical energy output device 8 is arranged on the mechanical energy output piston 7 of the last stage of Stirling working unit to form a multi-stage Stirling engine system with more than three stages.

The mechanical energy input device is selected from various devices which can drive the mechanical energy input piston to reciprocate, such as an electric motor, a circularly changed gas pressure difference, a circularly changed liquid pressure difference, a Stirling engine, a connecting rod between the mechanical energy input device and the mechanical energy output piston, and the like, or a combination of a plurality of modes.

The mechanical energy output device is selected from various devices which can output or utilize mechanical energy of the reciprocating motion of the mechanical energy output piston, such as a generator, a circularly changed gas pressure difference, a circularly changed liquid pressure difference, a Stirling heat pump, a connecting rod between the mechanical energy output device and the mechanical energy input piston, and the like, or a combination of a plurality of modes.

The operation mode of the multistage Stirling engine is as follows: under the drive of the mechanical energy input device, the mechanical energy input piston reciprocates in the cylinder, the mechanical energy which is in driving connection transmits the double-acting free piston to reciprocate in the cylinder, the mechanical energy transmits the double-acting free piston to drive the next stage piston to reciprocate in the cylinder step by step, the mechanical energy output piston reciprocates in the cylinder under the drive of the mechanical energy transmitting double-acting free piston, and the mechanical energy is output through the mechanical energy output device.

In order to realize the control of a system comprising a plurality of mutually-influenced free pistons, the invention innovatively introduces a mechanical energy input device into a group of pistons, so that the motion of the pistons becomes a dynamic system which is periodically excited by mechanical energy input and responds in a steady state.

The multi-stage Stirling engine comprises a plurality of free pistons which are mutually influenced, the movement of each piston is controlled to be in a stable operation state, and the required piston movement mode is realized through parameter calculation, selection and design on the basis of mastering the movement rule of the piston of the multi-stage Stirling engine, so that the multi-stage Stirling engine can adapt to the change of input conditions and adjust the output power as required.

The steady state operation parameter regulating and controlling method of the Stirling engine comprises the following steps:

(1) selecting the amplitude of the pistons and the phase angle between the pistons according to requirements, wherein the phase angle between the pistons is not more than 75 degrees;

(2) selecting the average length of the back pressure cavity of the mechanical energy input piston and the mechanical energy output piston, wherein the average length is suitable for enabling the volume of the back pressure cavity to be 3-8 times of the volume of an adjacent Stirling unit, and the smaller the ratio is, the larger the mass of the mechanical energy input piston and the mechanical energy output piston is required to be;

(3) selecting parameters of a radiator, a heat regenerator and a heat absorber, and calculating the volumes of the radiator, the heat regenerator and the heat absorber corresponding to the unit piston area, wherein the selection and calculation method can refer to the selection and calculation method of a common Stirling engine, and consider the lower unit cost factor of the Stirling engine;

(4) calculating and determining the average pressure of each Stirling unit, the area of each piston and the mass of each piston by using a forced vibration equation set;

(5) the operating parameters of the multi-stage stirling engine of the present invention are adjusted.

Further, the calculation method of the step (4) is as follows;

a. preliminarily selecting the number of stages of the multi-stage Stirling engine, the average pressure of each closed space and the area of each piston according to the mode that the area of the piston of the expansion cavity of the engine unit is larger than that of the piston of the compression cavity;

b. under the condition that the area of the mechanical energy output piston is not changed, the areas of other pistons are adjusted to enable the resultant force, which is calculated by utilizing equivalent linear rigidity and damping and acts on the double-acting piston when each mechanical energy transmission double-acting piston operates to a balance position, to be 0;

c. calculating the driving force of the mechanical energy input device and the damping of the mechanical energy output device according to the condition that the resultant force acting on the piston is 0 calculated by utilizing equivalent linear rigidity and damping when the piston runs to a balance position;

d. calculating the mass of each piston according to the resultant force of the acting forces calculated by using the equivalent linear stiffness when each piston runs to the maximum displacement and the acceleration of the piston;

e. for a multi-stage Stirling engine which is vertically arranged, the average pressure of each Stirling working unit and the back pressure cavity is adjusted according to the mass of each piston;

f. repeating the calculation from b to e until an ideal calculation result is obtained;

g. calculating mechanical energy input power and mechanical energy output power;

h. calculating power loss caused by the efficiency of the mechanical energy input device, and judging whether the proportion of the power loss caused by the efficiency of the mechanical energy input device to the total output power meets the requirement or not, wherein the mechanical energy output power is required to reach more than 10 times of the mechanical energy input power in order to control the power loss caused by the efficiency of the mechanical energy input device within 5% of the total output power under the general condition;

i. if the ratio of the power loss caused by the efficiency of the mechanical energy input device to the total output power does not meet the requirement, the number of stages of the multi-stage Stirling engine is increased, and the calculation is repeated.

Further, the step (5) of adjusting the operating parameters of the multi-stage stirling engine of the present invention 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 a back pressure cavity of the mechanical energy input piston and the volume of a back pressure cavity of the mechanical energy output piston at the same time;

D. when the ratio of the absolute temperatures of the heat source and the cold source is increased, the input power of mechanical energy needs to be reduced to maintain the output power unchanged;

E. when the ratio of the absolute temperatures of the heat source and the cold source is reduced, the mechanical energy input power needs to be reduced in order to maintain the input power unchanged.

Under the condition of small compression ratio, the pressure of each closed space of the multi-stage Stirling engine is approximately in a linear relation with the change of the displacement of the piston; acting to replace the mechanical losses and the effect of the mechanical energy output device of each stirling unit with equivalent damping on each piston; the driving force of the mechanical energy input means is expressed as a periodic excitation. And establishing the forced vibration equation of each piston to form a system of forced vibration equations. The forced vibration equation set is expressed by piston unit area mass, pressure and unit piston area damping.

Forced vibration equation set of stirling machine:

m₁x₁”+c₁x₁’+(k₁₀+k₁₂)x₁-k₂₁x₂＝qsin(ωt)

m₂x₂”+c₂x₂’-k₁₂x₁+(k₂₁+k₂₃)x₂-k₃₂x₃＝0

……

m_ix_i”+c_ix_i’-k_(i-1)ix_(i-1)+(k_i(i-1)+k_i(i+1))x_i-k_(i+1)ix_(i+1)＝0

……

m_nx_n”+c_nx_n’-k_(n-1)nx_(n-1)+(k_n(n-1)+k_n(n+1))x_n＝0

wherein m is₁、m₂、…、m_i、…、m_nThe unit area mass of the piston (2) for inputting mechanical energy, each mechanical energy transmission double-acting free piston and the mechanical energy output piston (7);

omega is the circular frequency of the driving force of the mechanical energy input device;

q is the maximum value of the acting force of the mechanical energy input device acting on the unit mechanical energy input piston;

t is time;

x₁、x₂、…、x_i、…、x_nthe displacement of the double-acting free piston for mechanical energy input piston (2), each mechanical energy transmission and the mechanical energy output piston (7) is a function of time t;

x₁’、x₂’、…、x_i’、…、x_nthe speed of a mechanical energy input piston (2), each mechanical energy transmission double-acting free piston and a mechanical energy output piston (7) is calculated;

x₁”、x₂”、…、x_i”、…、x_nthe acceleration of a mechanical energy input piston (2), each mechanical energy transmission double-acting free piston and a mechanical energy output piston (7) is obtained;

c₁、c₂、…、c_i、…、c_nequivalent unit piston area damping for a mechanical energy input piston (2), each mechanical energy transfer double-acting free piston and a mechanical energy output piston (7);

k₁₀、k₁₂is x₁The pressure change of the closed spaces at the upper side and the lower side of the piston caused by unit displacement, k₂₁、k₂₃、k₃₂、k₃₄… … and so on.

Converting the forced vibration equation set of the Stirling engine to obtain an equivalent equation set, wherein the conversion process is as follows:

setting:

where 1 represents an area having a value of 1, the same applies hereinafter

y₁＝x₁

m_y1＝m₁×1

c_y1＝c₁×1

k₁＝k₁₀×1y₂＝x₂(k₂₁/k₁₂)

m_y2＝m₂(k₁₂/k₂₁)×1

c_y2＝c₂(k₁₂/k₂₁)×1

k₂＝k₁₂×1

y₃＝x₃(k₂₁/k₁₂)(k₃₂/k₂₃)

m_y3＝m₃(k₁₂/k₂₁)(k₂₃/k₃₂)×1

c_y3＝c₃(k₁₂/k₂₁)(k₂₃/k₃₂)×1

k₃＝k₂₃(k₁₂/k₂₁)×1

……

y_i＝x_i(k₂₁/k₁₂)(k₃₂/k₂₃)…(k_i(i-1)/k_(i-1)i)

m_yi＝m_i(k₁₂/k₂₁)(k₂₃/k₃₂)…(k_(i-1)i/k_i(i-1))×1

c_yi＝c_i(k₁₂/k₂₁)(k₂₃/k₃₂)…(k_(i-1)i/k_i(i-1))×1

k_i＝k_(i-1)i(k₁₂/k₂₁)(k₂₃/k₃₂)…(k_(i-2)(i-1)/k_(i-1)(i-2))×1

……

Substituting into a forced vibration equation set of the Stirling engine to obtain an equation set of an equivalent:

m_y1y₁”+c_y1y₁’+(k₁+k₂)y₁-k₂y₂＝fsin(ωt)

m_y2y₂”+c_y2y₂’-k₂y₁+(k₂+k₃)y₂-k₃y₃＝0

……

m_yiy_i”+c_yiy_i’-k_iy_(i-1)+(k_i+k_(i+1))y_i-k_(i+1)y_(i+1)＝0

……

m_yny_n”+c_yny_n’-k_ny_(n-1)+(k_n+k_(n+1))y_n＝0

the structural form of the equivalent equation set is the same as that of the forced vibration equation set of the conventional multi-degree-of-freedom system, so that the equivalent multi-degree-of-freedom system consisting of the mass points and the common springs can be constructed, and the forced vibration equation set of the equivalent multi-degree-of-freedom system is the same as that of the equivalent equation set. The characteristics of an equivalent equation set can be known that the equivalent multi-degree-of-freedom system is similar to the mechanical system of the Stirling engine in structure, the mass of each node is equal to the mass of a unit piston area multiplied by the corresponding conversion coefficient, the damping acting on each node is equal to the damping of the unit piston area multiplied by the corresponding conversion coefficient, and the rigidity of each spring is related to the parameters of the Stirling unit. The equivalent multi-degree-of-freedom system of the multi-stage Stirling engine is a chain system formed by mass points connected in sequence through springs.

The motion law of the equivalent multi-degree-of-freedom system under the action of periodic excitation can be expressed as the solution of an equivalent equation set, the solution of a Stirling engine forced vibration equation set can be obtained through the solution of the equivalent equation set, and the solution of the Stirling engine forced vibration equation set expresses the motion law of each piston of the multi-stage Stirling engine. Therefore, the motion law that the multistage Stirling engine piston has similar mechanical wave propagation can be deduced according to the motion law of an equivalent multi-degree-of-freedom system. The motion rule of the piston can meet the working requirement of the Stirling engine.

In order to realize that the piston operates according to the required mode, a mathematical relation between the mass of the piston per unit area, the pressure change caused by the displacement of the piston per unit area and the damping per unit area of the piston needs to be determined. The mathematical relationship may be obtained by expressing the desired piston operating mode as a steady state solution of the equation and substituting the steady state solution into the forced vibration equation. According to the working requirement and the operation rule of the Stirling engine, the expected amplitude of each piston and the phase angle between the pistons are selected, the selected operation mode is expressed as the steady state solution of the forced vibration equation set of the Stirling engine, and the steady state solution is substituted into the forced vibration equation set of the multi-stage Stirling engine, so that the mathematical relational expression among unit piston mass, unit piston displacement caused pressure change and unit piston area damping can be obtained. The specific process is as follows:

setting a steady state solution of a Stirling engine forced vibration equation set:

x₁＝X₁sin(ωt-θ)

x₂＝X₂sin(ωt-θ-θ₁)

x₃＝X₃sin(ωt-θ-θ₁-θ₂)

X₁、X₂、X₃1/2 for amplitude of each piston

Theta is a phase angle between the mechanical energy input piston and the driving force of the mechanical energy input device

θ₁、θ₂Is the phase angle between pistons

The steady state solution is substituted into a forced vibration equation set of the Stirling engine to obtain a mathematical relational expression between unit piston mass, pressure change caused by unit piston displacement and unit piston area damping. The mathematical relationship can be summarized as follows: the following conditions are required to be satisfied between the unit piston mass, the unit piston displacement caused pressure change and the unit piston area damping calculated according to the given period, the phase angle and the piston amplitude:

(1) when any piston runs to a balance position, the resultant force acting on the piston is 0 by utilizing equivalent linear rigidity and damping calculation;

(2) when any piston is operated to the maximum displacement, the resultant force on that piston, calculated using the equivalent linear stiffness, is equal to the product of the piston mass and the acceleration, calculated for a given period and piston amplitude.

The equivalent linear stiffness can be calculated according to the pressure change of the Stirling unit caused by the small displacement of the piston, the calculation method is similar to that of a conventional Stirling engine, and the calculation method is not described in detail herein; the equivalent linear damping can be calculated by weighting the mechanical losses of the stirling units to the corresponding pistons, taking into account the effect of the mechanical energy output means, and can be achieved by conventional calculation methods, which are not described in detail here.

The multistage Stirling engine meeting the conditions has the following operation rule under the condition of a small compression ratio:

1. operating according to said given cycle, the movement of the piston is transmitted in a mechanical wave-like manner from the mechanical energy input piston to the mechanical energy output piston, the mechanical energy being amplified when passing through the stirling engine unit;

2. the mechanical energy output piston does not cause reflection of mechanical waves when running according to the given period, and the motion of the piston meets the propagation rule of similar mechanical waves;

3. under the condition that the Stirling units adopt the same parameters such as piston area ratio, compression ratio, phase difference, piston amplitude and the like, for a Stirling working unit with negligible mechanical loss, the area ratio of an expansion piston to a compression piston is equal to the effective absolute temperature ratio in an expansion cavity and a compression cavity, and the piston area ratio is reduced along with the increase of the mechanical loss.

The forced vibration equation set of the multi-stage Stirling engine, which meets the relational expression, has unique steady-state solution, and the steady-state solution of the forced vibration equation set of the Stirling engine in the prior art is established by the same method and is not unique, so that the multi-stage Stirling engine is more stable and controllable in operation compared with the prior art.

Further, the calculation and parameter adjustment method of the multi-stage Stirling heat pump is determined by the same method as the calculation principle.

The multistage stirling engine of the invention has obvious technical advantages, which are mainly shown in the following aspects:

1. the multi-stage Stirling stage can enable the mechanical energy output power to reach more than 10 times of the mechanical energy input power by setting enough stages, realizes several mechanical energy outputs of the multi-stage Stirling engine unit, and has obvious application value compared with the existing Stirling engine. The mechanical energy input piston reciprocates in the cylinder under the drive of the mechanical energy input device, the motion of the piston is transmitted to the mechanical energy output piston in a mode similar to mechanical waves, and the mechanical energy is output through the mechanical energy output device. When the Stirling engine is used, mechanical energy is amplified step by step when being transmitted through the Stirling unit, so that the mechanical energy output power can reach 10 times or even higher than the mechanical energy input power by setting enough steps even if the temperature difference between the cold source and the heat source is low.

2. The multi-stage Stirling engine can realize the effect that the double-acting free piston is transmitted by mechanical energy to eliminate components such as a piston rod and the like through the parameter optimization of each working unit, so that the structure is simpler and more compact. The parameters of each Stirling working unit are set, so that the mechanical energy transfer double-acting free piston inputs mechanical energy from the connected one-stage Stirling working unit, mechanical loss of reciprocating motion of the piston and working gas is overcome, all the mechanical energy is output to the connected next-stage Stirling working unit in a complete operation period, the mechanical energy transfer double-acting free piston can reciprocate only under the action of pressure change of the working gas of the Stirling working units on two sides, and the purpose of eliminating devices such as a piston rod is achieved. In one group of pistons, only the mechanical energy input piston and the mechanical energy output piston which are arranged at two ends can be provided with piston rods which are connected with the mechanical energy input device and the mechanical energy output device.

3. The multi-stage stirling stage of the present invention is adapted to employ a large diameter piston. According to the multi-stage Stirling engine, all the pistons, the radiator, the heat regenerator and the heat absorber can be arranged on the same straight line, each Stirling working unit is arranged between the two pistons, auxiliary connecting members such as elbows and the like are not included, the proportion of invalid volume cannot be increased due to the increase of the diameter of the pistons, the piston stroke does not need to be increased under the condition that the diameter of the pistons is increased, and the characteristic enables the Stirling engine to be suitable for adopting large-diameter pistons.

4. The multistage Stirling machine does not need to be provided with a spring for bearing the dead weight of the piston and controlling the balance position of the piston, and the structure of the equipment is simplified. The working units of the multi-stage Stirling engine are not in circulating connection, and the fact that the Stirling units at all stages adopt the same average pressure is not required, so that the effects of controlling the balance positions of the pistons and bearing the dead weight of the pistons by using the pressure difference of the working gas can be achieved by adjusting the gas amount of each closed space according to the positions of the pistons. The above features eliminate the need for a spring for the piston to bear its own weight and control the equilibrium position of the stirling machine of the present invention.

5. The multistage Stirling engine has good adjustability and anti-interference capability. Through simulation calculation, the input power of the mechanical energy input device is adjusted to increase the output power of the engine from 10% of the design power to 95% of the design power within 3-4 cycles. The Stirling engine with good anti-interference capability can be manufactured by the method, the input parameters are adjusted in a reasonable range through simulation calculation, the Stirling engine can be stably converted into a new stable operation state within 3-4 periods, and the operation state does not change abnormally under the new working condition.

6. The multi-stage Stirling engine can be widely applied to the fields of waste heat power generation, renewable energy power generation and the like, and is suitable for improving the energy utilization efficiency by utilizing a cogeneration mode. The multi-stage Stirling engine does not require that all stages of Stirling units adopt the same temperature, and can enable a heat source or cold source medium to pass through a plurality of heaters or coolers in a series connection mode, so that the purpose of improving the energy utilization efficiency is achieved; multiple heat sources or cold sources can be used in a group of pistons, so that the purpose of one machine with multiple purposes or providing waste heat with multiple temperatures is achieved. The simple structure of the multistage Stirling engine can obviously reduce the processing and manufacturing cost of equipment, and the equipment cost of unit power can be reduced by greatly enlarging the diameter of the piston.

Through measurement and calculation, the Stirling engine for waste heat recovery manufactured by the method can achieve 2-3 years of recovery investment under the condition that the temperature of a heat source reaches 300 ℃ and the single-machine power reaches 300kW scale.

The multi-stage Stirling engine manufactured by the invention can be used for waste heat power generation, for example, the internal combustion engine is generally used for internal combustion engine exhaust waste heat power generation, methane power generation, landfill gas power generation and the like, the internal combustion engine exhaust temperature is higher, the Stirling engine is increased to generate power by using the internal combustion engine exhaust waste heat, and the generated energy can be increased by 10-15% under the condition of meeting the requirements of heat preservation of a methane tank and the like.

The multi-stage Stirling engine manufactured by the method can be used for garbage power generation and renewable fuel power generation, for example, the multi-stage Stirling engine is used for various projects which are not suitable for using a turbonator because of small scale, small-scale garbage power generation, agriculture and forestry biomass power generation and other devices are built, the garbage and the renewable fuel are disposed and utilized nearby, and the cost for collecting, storing and transporting the garbage and the renewable fuel is greatly reduced.

The multi-stage Stirling engine manufactured by the method can be used for building a distributed solar combined heat and power generation device, provides waste heat such as hot water and the like while generating power, and greatly improves the benefit of solar photo-thermal utilization. The device can be used as a security power supply after being provided with a heat storage system, and continuously supplies power to key facilities in a factory or a park under the condition of external power supply failure.

The multi-stage Stirling engine manufactured by the method can be used for building a small cogeneration device, generating electricity and simultaneously providing waste heat such as hot water and the like. For example, a small heating boiler is modified to a cogeneration unit.

The multi-stage Stirling engine manufactured by the method can be used for micro-grid power supply, and the energy storage cost is greatly reduced by utilizing the characteristics of large power regulation range and high regulation speed of the multi-stage Stirling engine and combining the obvious advantages of stored heat relative to stored electric power.

Drawings

FIG. 1 is a schematic view of a Stirling engine according to the prior art

FIG. 2 is a schematic diagram of a two-stage Stirling engine according to the present invention

FIG. 3 is a schematic view of a multi-stage Stirling engine according to the present invention

The system comprises a mechanical energy input device, a mechanical energy input piston, a first heat radiator, a first heat regenerator, a second heat radiator, a first heat absorber, a second heat radiator, a second heat regenerator, a second heat absorber, a 6-mechanical energy transfer double-acting free piston, a mechanical energy output piston and a mechanical energy output device, wherein the mechanical energy input device is 1, the mechanical energy input piston is 2, the first heat radiator is 3, the first heat regenerator is 4, the first heat absorber is 5, the second heat absorber is; 101-first cylinder, 102-second cylinder, 103-last 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 and 007-seventh-stage stirling working unit.

Detailed Description