Three-stage variable lead screw expander rotor and design method thereof

Abstract

A three-section variable lead double-screw expander rotor and a design method thereof, the three-section variable lead double-screw expander rotor comprising a male rotor and a female rotor meshing with each other, the male rotor and the female rotor both having three sections of a low-pressure section, an intermediate section and a high-pressure section arranged in sequence along an axial direction, each of the low-pressure section, the intermediate section and the high-pressure section being of an equal lead, the lead of the intermediate section being smaller than that of the high-pressure section, and the lead of the high-pressure section being smaller than that of the low-pressure section, the low-pressure section being close to a low-pressure port side of the expander, and the high-pressure section being close to a high-pressure port side of the expander, under a given constraint condition, the high-pressure port communication area before the high-pressure port is closed is made as large as possible by adjusting parameters.The three-section variable lead double-screw expander rotor effectively increases the high-pressure port communication area before the high-pressure port is closed, can make the double-screw expander fully inhale during the entire inhaling process, reduces the throttling loss of the expander inhaling process, especially the pre-expansion loss in the later stage of the inhaling process, and greatly improves the recovery work of the expander.

Description

Technical Field

[0001] This invention belongs to the field of twin-screw machinery, specifically relating to a three-segment variable lead twin-screw expander rotor and its design method. Background Technology

[0002] Twin-screw expanders have significant advantages in waste heat and pressure recovery applications due to their high reliability and two-phase expansion capabilities, such as Rankine cycle power generation, organic Rankine cycle, and fuel cell exhaust gas waste pressure recovery. However, the application of screw expanders is still not widespread, mainly due to their relatively low efficiency.

[0003] Research has found that the large throttling losses at the intake orifice and the large pre-expansion throttling losses during the intake process are one of the main reasons for the low efficiency and low recovery power of twin-screw expanders, and there is currently no mature solution to this problem. Summary of the Invention

[0004] The purpose of this invention is to provide a three-stage variable lead twin-screw expander rotor and its design method, which can effectively solve the problems of large intake pressure loss and low recovery power of existing twin-screw expanders.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A three-segment variable lead twin-screw expander rotor includes a male rotor and a female rotor that mesh with each other. Both the male and female rotors have three rotor segments arranged sequentially along the axial direction: a low-pressure segment, an intermediate segment, and a high-pressure segment. Each rotor segment in the low-pressure segment, intermediate segment, and high-pressure segment has the same lead, and the lead of the intermediate segment is smaller than that of the high-pressure segment, and the lead of the high-pressure segment is smaller than that of the low-pressure segment. The low-pressure segment is closer to the low-pressure orifice side of the expander, and the high-pressure segment is closer to the high-pressure orifice side of the expander. Under given constraints, parameters are adjusted to maximize the high-pressure orifice connection area before the high-pressure orifice is closed.

[0007] As a preferred embodiment, the male and female rotors have a length of L and the number of teeth are n1 and n2, respectively, and the torsion angle of the male rotor is τ. w The internal volume ratio of the twin-screw expander is Vi.

[0008] As a preferred embodiment, the lead T3 of the high-voltage section of the male rotor is equal to L / τ. w ×360, the torsion angle τ3 of the high-voltage section of the male rotor is greater than or equal to 120 / n1 degrees.

[0009] As a preferred embodiment, the lead T2 of the middle section of the male rotor is less than L / τ. w ×360, the torsion angle τ2 of the middle section of the male rotor is greater than or equal to 120 / n1 degrees.

[0010] As a preferred approach, the high-pressure orifice connection area before closure is maximized by setting the lead T2 and the torsion angle τ2.

[0011] As a preferred embodiment, the lead T1 of the low-pressure section of the male rotor is greater than L / τ. w ×360, the torsion angle τ1 of the low-pressure section of the male rotor is equal to τ w -τ2-τ3, the length of the low-pressure section of the male rotor is less than L / V i .

[0012] As a preferred embodiment, at any position along the same axial direction, the ratio of the male rotor lead to the female rotor lead is equal to n1:n2.

[0013] A design method for a rotor of a three-segment variable lead twin-screw expander includes the following steps:

[0014] The outline structure of the male rotor and the female rotor is determined. The male rotor and the female rotor mesh with each other, and both the male rotor and the female rotor have three rotor segments arranged sequentially along the axial direction: a low-pressure segment, an intermediate segment, and a high-pressure segment. Each rotor segment in the low-pressure segment, the intermediate segment, and the high-pressure segment has the same lead. The lead of the intermediate segment is smaller than the lead of the high-pressure segment, and the lead of the high-pressure segment is smaller than the lead of the low-pressure segment. The low-pressure segment is closer to the low-pressure orifice side of the expander, and the high-pressure segment is closer to the high-pressure orifice side of the expander.

[0015] Based on the constraints, determine the length L3 and torsion angle τ3 of the high-voltage section of the male rotor;

[0016] Based on the constraints, determine the length L2 and torsion angle τ2 of the middle section of the male rotor;

[0017] The length L1 and torsion angle τ1 of the low-pressure section of the male rotor are determined based on the length L3 and torsion angle τ3 of the high-pressure section, and the length L2 and torsion angle τ2 of the middle section of the male rotor; where L1 = L - L2 - L3, τ1 = τ w -τ2-τ3, where L is the total length of the male rotor, τ w This is the total torsion angle of the male rotor;

[0018] Based on the determined variable lead structure of the male rotor, the corresponding strain lead structure of the female rotor is determined, and the parameters are adjusted to maximize the high-pressure orifice connection area before the high-pressure orifice is closed.

[0019] As a preferred embodiment, in the step of determining the length L3 and torsion angle τ3 of the high-voltage section of the male rotor according to the constraints, the constraints are as follows:

[0020] The lead of the high-voltage section of the anode rotor is T3 = L3 / τ3 × 360, and T3 is also equal to L / τ. w×360, the torsion angle τ3 of the high-voltage section of the male rotor is greater than or equal to 120 / n1 degrees;

[0021] In determining the length L2 and torsion angle τ2 of the middle section of the male rotor based on the constraints, the constraints are as follows:

[0022] The lead of the middle section of the male rotor is T2 = L2 / τ2 × 360, where T2 is less than L / τ. w ×360, the torsion angle τ2 of the middle section of the male rotor is greater than or equal to 120 / n1 degrees;

[0023] By setting the lead T2 and torsion angle τ2, the high-pressure orifice connection area before closure is maximized. The internal volume ratio of the twin-screw expander is Vi, and the length L1 of the low-pressure section of the male rotor is less than L / V. i .

[0024] As a preferred embodiment, in the step of determining the strain lead structure of the female rotor based on the determined variable lead structure of the male rotor, the variable lead structure of the female rotor is determined according to the principle that the ratio of the lead of the male rotor to the lead of the female rotor is equal to n1:n2 at any position in the same axial direction.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] This invention addresses the use of a three-stage variable-lead male and female rotor in a twin-screw expander. The lead of the middle stage is set to be smaller than that of the high-pressure stage, and the lead of the high-pressure stage is set to be smaller than that of the low-pressure stage. This positions the low-pressure stage closer to the low-pressure orifice side of the expander, and the high-pressure stage closer to the high-pressure orifice side. Under given constraints, by adjusting parameters, the high-pressure orifice connection area before closure can be easily maximized. This invention utilizes variable-lead rotor technology to increase the high-pressure orifice area and reduce the flow resistance at the high-pressure orifice, thereby improving the isentropic efficiency of the screw and overcoming the large intake throttling loss inherent in screw expanders. The three-stage variable-lead twin-screw expander rotor of this invention effectively increases the high-pressure orifice connection area before closure, allowing the twin-screw expander to fully intake air throughout the intake process, reducing throttling losses during intake, especially pre-expansion losses in the later stages of intake, and significantly improving the expander's recovery power. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0028] Figure 1(a) is a schematic diagram of the three-segment variable lead curve of the rotor of the three-segment variable lead twin-screw expander according to an embodiment of the present invention;

[0029] Figure 1(b) is a three-dimensional structural diagram of the rotor of the three-segment variable lead twin-screw expander according to an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the high-pressure orifice connection area of ​​a three-stage variable lead and fixed lead twin-screw expander as the inter-tooth volume changes;

[0031] Figure 3 Schematic diagram of the change in intracavity pressure with inter-tooth volume in a three-stage variable lead and constant lead twin-screw expander. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, those skilled in the art can obtain other embodiments without creative effort.

[0033] Please refer to Figures 1(a) and 1(b). The rotor of the three-segment variable lead twin-screw expander of this embodiment includes a male rotor and a female rotor that mesh with each other. Both the male and female rotors have three segments arranged sequentially along the axial direction: a low-pressure segment, a middle segment, and a high-pressure segment. Each segment in the low-pressure, middle, and high-pressure segments has an equal lead. The lead T2 of the middle segment of the male rotor is less than the lead T3 of the high-pressure segment, and the lead T3 of the high-pressure segment is less than the lead T1 of the low-pressure segment. The low-pressure segment of the male rotor is closer to the low-pressure orifice of the expander, and the high-pressure segment is closer to the high-pressure orifice of the expander. The length of the male and female rotors is L, and the number of teeth are n1 and n2, respectively. The torsion angle of the male rotor is τ. w The internal volume ratio of the twin-screw expander is Vi. Under given constraints, the goal is to maximize the high-pressure orifice opening area before it is closed by adjusting the parameters.

[0034] In one possible implementation, the lead T3 of the high-voltage section of the male rotor is equal to L / τ. w ×360, the torsion angle τ3 of the high-voltage section of the male rotor is greater than or equal to 120 / n1 degrees.

[0035] In one possible implementation, the lead T2 of the middle section of the male rotor is less than L / τ. w ×360, the torsion angle τ2 of the middle section of the male rotor is greater than or equal to 120 / n1 degrees. By setting the lead T2 and the torsion angle τ2, the high-pressure orifice connection area before the high-pressure orifice is closed is maximized.

[0036] In one possible implementation, the lead T1 of the low-pressure section of the male rotor is greater than L / τ. w ×360, the torsion angle τ1 of the low-pressure section of the male rotor is equal to τ w -τ2-τ3, the length of the low-voltage section of the male rotor is less than L / V i .

[0037] In one possible implementation, at any position along the same axial direction, the ratio of the male rotor lead to the female rotor lead is equal to n1:n2.

[0038] The design method for a three-segment variable lead twin-screw expander rotor according to an embodiment of the present invention includes the following steps:

[0039] S1. Determine the outline structure of the male rotor and the female rotor. The male rotor and the female rotor mesh with each other, and both the male rotor and the female rotor have three rotor segments arranged sequentially along the axial direction: a low-pressure segment, a middle segment, and a high-pressure segment. Each rotor segment in the low-pressure segment, the middle segment, and the high-pressure segment has the same lead. The lead of the middle segment is smaller than the lead of the high-pressure segment, and the lead of the high-pressure segment is smaller than the lead of the low-pressure segment. The low-pressure segment is closer to the low-pressure orifice of the expander, and the high-pressure segment is closer to the high-pressure orifice of the expander.

[0040] S2. Based on the constraints, determine the length L3 and torsion angle τ3 of the high-voltage section of the male rotor;

[0041] S3. Based on the constraints, determine the length L2 and torsion angle τ2 of the middle section of the male rotor;

[0042] S4. Determine the length L1 and torsion angle τ1 of the low-pressure section of the male rotor based on the length L3 and torsion angle τ3 of the high-pressure section, and the length L2 and torsion angle τ2 of the middle section of the male rotor; where L1 = L - L2 - L3, τ1 = τ w -τ2-τ3, where L is the total length of the male rotor, τ w This is the total torsion angle of the male rotor;

[0043] S5. Based on the determined variable lead structure of the male rotor, determine the strain lead structure of the female rotor, and adjust the parameters to maximize the high-pressure port connection area before the high-pressure port is closed.

[0044] In one possible implementation, in step S2, which involves determining the length L3 and torsion angle τ3 of the high-voltage section of the male rotor based on constraints, the constraints are: the lead T3 of the high-voltage section of the male rotor = L3 / τ3 × 360°, and T3 is also equal to L / τ3. w ×360, the torsion angle τ3 of the high-voltage section of the male rotor is greater than or equal to 120 / n1 degrees.

[0045] In one possible implementation, in step S3, which involves determining the length L2 and torsion angle τ2 of the male rotor's intermediate section based on constraints, the constraints are: the lead of the male rotor's intermediate section T2 = L2 / τ2 × 360°, and T2 is less than L / τ2. w ×360, the torsion angle τ2 of the middle section of the male rotor is greater than or equal to 120 / n1 degrees.

[0046] Furthermore, by setting the lead T2 and torsion angle τ2, the high-pressure orifice connection area before closure is maximized, the internal volume ratio of the twin-screw expander is Vi, and the length L1 of the low-pressure section of the male rotor is less than L / V. i .

[0047] In one possible implementation, in step S5, which involves determining the strain lead structure of the female rotor based on the determined variable lead structure of the male rotor, the variable lead structure of the female rotor is determined according to the principle that the ratio of the lead of the male rotor to the lead of the female rotor is equal to n1:n2 at any position in the same axial direction.

[0048] See Figure 2 The figure shows the variation of the high-pressure orifice connection area with the relative inter-tooth volume of a twin-screw expander with an internal volume ratio of 2 and rotors having constant lead and three-stage variable lead.

[0049] from Figure 2 As can be seen from the data, in the initial stage of air intake, the high-pressure orifice connection area of ​​the three-stage variable lead twin-screw expander proposed in this invention is slightly smaller than that of the fixed lead twin-screw expander. However, in the middle and later stages of air intake, the high-pressure orifice connection area of ​​the three-stage variable lead twin-screw expander is significantly larger than that of the fixed lead twin-screw expander. Therefore, this confirms that the scheme proposed in this invention can achieve sufficient air intake of the expander.

[0050] See Figure 3 The figure shows the pV diagram of a twin-screw expander with an internal volume ratio of 2, working fluid of air, intake pressure of 400 kPa, exhaust pressure of 100 kPa, and rotors with constant lead and three-stage variable lead.

[0051] from Figure 3 As can be seen from the above, since the three-stage variable lead twin-screw expander proposed in this invention can achieve full air intake, the gas pressure inside the cavity of the three-stage variable lead twin-screw expander is greater than that of the fixed lead twin-screw expander during the entire air intake process, and the recoverable expansion work is increased by 7%, which proves the effectiveness of the structure of this invention.

[0052] This invention effectively increases the high-pressure orifice connection area before the high-pressure orifice is closed by using a three-stage variable lead rotor, which allows the twin-screw expander to fully absorb air throughout the entire intake process, reducing the throttling loss during the expander's intake process, especially the pre-expansion loss in the later stage of the intake process, and greatly improving the expander's recovery power.

[0053] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A rotor for a three-segment variable lead twin-screw expander, characterized in that, It includes a male rotor and a female rotor that mesh with each other. Both the male rotor and the female rotor have three rotor segments arranged sequentially along the axial direction: a low-pressure segment, an intermediate segment, and a high-pressure segment. Each rotor segment in the low-pressure segment, intermediate segment, and high-pressure segment has the same lead. The lead of the intermediate segment is smaller than that of the high-pressure segment, and the lead of the high-pressure segment is smaller than that of the low-pressure segment. The low-pressure segment is closer to the low-pressure orifice side of the expander, and the high-pressure segment is closer to the high-pressure orifice side of the expander. Under given constraints, the parameters are adjusted to maximize the high-pressure orifice connection area before the high-pressure orifice is closed.

2. The rotor of the three-segment variable lead twin-screw expander according to claim 1, characterized in that, The lengths of the male rotor and the female rotor are: L The number of teeth are respectively n 1. n 2. The total torsion angle of the male rotor is τ w The internal volume ratio of the twin-screw expander is V i.

3. The rotor of the three-segment variable lead twin-screw expander according to claim 2, characterized in that, The lead of the high-voltage section of the male rotor T 3 equals L / τ w ×360, the torsion angle of the high-voltage section of the male rotor. τ 3 greater than or equal to 120 / n 1 degree.

4. The rotor of the three-segment variable lead twin-screw expander according to claim 3, characterized in that, The lead of the middle section of the male rotor T 2 less than L / τ w ×360, the torsion angle of the middle section of the male rotor τ 2 is greater than or equal to 120 / n 1 degree.

5. The rotor of the three-segment variable lead twin-screw expander according to claim 4, characterized in that, By guiding T 2 and twist angle τ Setting 2 maximizes the high-pressure orifice connection area before it is closed.

6. The rotor of the three-segment variable lead twin-screw expander according to claim 4, characterized in that, The lead of the low-pressure section of the male rotor T 1 greater than L / τ w ×360, the torsion angle of the low-pressure section of the male rotor τ 1 equals τ w - τ 2- τ 3. The length of the low-pressure section of the male rotor is less than... L / V i .

7. The rotor of the three-segment variable lead twin-screw expander according to claim 2, characterized in that, At any position along the same axial direction, the ratio of the male rotor lead to the female rotor lead is equal to... n 1: n 2.

8. A design method for a rotor of a three-segment variable lead twin-screw expander, characterized in that, Includes the following steps: The outline structure of the male rotor and the female rotor is determined. The male rotor and the female rotor mesh with each other, and both the male rotor and the female rotor have three rotor segments arranged sequentially along the axial direction: a low-pressure segment, an intermediate segment, and a high-pressure segment. Each rotor segment in the low-pressure segment, the intermediate segment, and the high-pressure segment has the same lead. The lead of the intermediate segment is smaller than the lead of the high-pressure segment, and the lead of the high-pressure segment is smaller than the lead of the low-pressure segment. The low-pressure segment is closer to the low-pressure orifice side of the expander, and the high-pressure segment is closer to the high-pressure orifice side of the expander. Determine the length of the high-voltage section of the male rotor based on the constraints. L 3 and torsion angle τ 3; Determine the length of the middle section of the male rotor based on the constraints. L 2 and twist angle τ 2; Based on the length of the high-voltage section of the male rotor L 3 and torsion angle τ 3, and the length of the middle section of the male rotor. L 2 and twist angle τ 2. Determine the length of the low-pressure section of the male rotor. L 1 and torsion angle τ 1; among which, L 1= L - L 2- L 3, τ 1= τ w - τ 2- τ 3. In the formula, L The total length of the male rotor, τ w This is the total torsion angle of the male rotor; Based on the determined variable lead structure of the male rotor, the corresponding strain lead structure of the female rotor is determined, and the parameters are adjusted to maximize the high-pressure orifice connection area before the high-pressure orifice is closed.

9. The design method for a three-segment variable lead twin-screw expander rotor according to claim 8, characterized in that, The length of the high-voltage section of the male rotor is determined according to the constraints. L 3 and torsion angle τ In step 3, the constraints are: The lead of the high-voltage section of the male rotor T 3= L 3 / τ 3×360, T 3 also equals L / τ w ×360, the torsion angle of the high-voltage section of the male rotor. τ 3 greater than or equal to 120 / n 1 degree, n 1 represents the number of teeth on the male rotor; The length of the middle section of the male rotor is determined according to the constraints. L 2 and twist angle τ In step 2, the constraints are: The lead of the middle section of the male rotor T 2= L 2 / τ 2×360, T 2 less than L / τ w ×360, the torsion angle of the middle section of the male rotor τ 2 is greater than or equal to 120 / n 1 degree; Through the guide T 2 and twist angle τ The setting of 2 maximizes the high-pressure orifice connection area before closure, resulting in a twin-screw expander internal volume ratio of [value missing]. V i, the length of the low-pressure section of the male rotor L 1 less than L / V i .

10. The design method for a three-segment variable lead twin-screw expander rotor according to claim 8, characterized in that, In the step of determining the corresponding strain lead structure of the female rotor based on the determined variable lead structure of the male rotor, the ratio of the male rotor lead to the female rotor lead is equal to the ratio of the male rotor lead to the female rotor lead at any position along the same axial direction. n 1: n The principle of 2 determines the variable lead structure of the female rotor. n 1. n 2 represents the number of teeth on the male rotor and the female rotor, respectively.

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