A strength verification method for a steam turbine filter body

Abstract

A method for verifying the strength of a steam turbine filter body, belonging to the technical field of steam turbines. The present invention aims to solve the problem that the filter body in the steam turbine valve has insufficient strength and is damaged, resulting in the need for frequent replacement of the filter body. First, assume that the filter body is unobstructed, calculate the maximum stress on the filter body under unobstructed conditions according to the pressure P in the external pressure chamber of the filter, and compare it with the interval from the constant strength to the creep strength. Then, assume that the filter body is blocked, calculate the maximum stress on the filter body under blocked conditions according to the pressure P in the external pressure chamber of the filter, and compare it with 50% of the yield strength. When both comparison results are less than, it is determined that the strength of the filter body is qualified. The present invention obtains a reliable conclusion through intelligent algorithm analysis, avoiding frequent replacement of the filter body due to insufficient strength of the filter body.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbines, and particularly relates to a method for strength verification of a steam turbine filter body. Background Art

[0002] A filter body is provided inside the main steam valve or regulating valve of a steam turbine to filter impurities in the steam.

[0003] At present, there is no clear calculation method for the filter body inside the steam turbine valve, but the filter body damage phenomenon will occur on site. Therefore, it is very necessary to conduct strength verification on the filter body inside the steam turbine valve according to the actual situation, and obtain a reliable conclusion through intelligent algorithm analysis to avoid frequently replacing the filter body due to insufficient strength of the filter body. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for strength verification of a steam turbine filter body to solve the problem that there is no clear calculation method for the filter body inside the steam turbine valve, and the filter body needs to be frequently replaced when the filter body damage phenomenon occurs. The technical solution adopted by the present invention is as follows:

[0005] A method for strength verification of a steam turbine filter body is implemented relying on a steam turbine valve, including a valve body. A valve cavity is provided inside the valve body. The lower end of the valve body is communicated with the valve cavity through a steam inlet. The right end of the valve body is communicated with the valve cavity through a steam outlet. The left end of the valve body is communicated with the valve cavity through a cut-off control port. An inner valve cover is provided inside the diameter of the cut-off control port. A valve seat is arranged on the diameter of the steam outlet. The filter body is tubular. The left end of the filter body is connected to the cut-off control port, and the right end of the filter body is connected to the steam outlet. A plurality of filter holes are provided on the filter body. The filter holes include a tapered hole section and a straight hole section connected from the outside to the inside. The tapered hole section is a 90° tapered hole converging from the outside to the inside. A filter outer pressure cavity is formed between the outer periphery of the filter body and the inner periphery of the valve cavity. The right end of the valve rod passes through the inner valve cover and extends into the inner cavity of the filter body and is connected to a valve flap. The valve rod is slidably arranged left and right to open and close the valve seat by the valve flap. When the valve is opened, the steam inlet is sequentially communicated with the steam outlet through the filter outer pressure cavity, a plurality of filter holes, and the inner cavity of the filter body;

[0006] The filter body is formed by rolling a hole plate provided with a plurality of filter holes. The hole plate is a rectangular hole plate, and the long side of the hole plate forms the circumferential direction of the rolled filter body;

[0007] The hole plate is provided with a plurality of filter holes in an equilateral triangle array. Three adjacent filter holes forming an equilateral triangle on the hole plate are defined as a minimum triangular unit, and one side of the minimum triangular unit is arranged along the long side direction of the hole plate;

[0008] It includes the following steps:

[0009] Step 1: Measure the pressure P in the external pressure chamber of the filter screen through a pressure sensor, with the unit of MPa;

[0010] Step 2: Define the distance L between the filtering holes at the two vertices facing away from each other of the two adjacent triangular units, with the unit of mm. The shortest distance between the major diameters of the tapered hole sections of the two vertex filtering holes is h 1 , with the unit of mm. The shortest distance between the straight hole sections of the two vertex filtering holes is h 0 , with the unit of mm;

[0011] h 1 is determined by the following formula:

[0012] h 1 = L - d 1

[0013] In the formula:

[0014] d 1 is the major diameter of the large end of the tapered hole section, with the unit of mm;

[0015] h 0 is determined by the following formula:

[0016] h 0 = L - d 0

[0017] In the formula:

[0018] d 0 is the diameter of the straight hole section, with the unit of mm;

[0019] Step 3: Assume that the filter screen body is unobstructed. Calculate the maximum stress on the filter screen body under unobstructed conditions based on the pressure P in the external pressure chamber of the filter screen, and compare it with the interval from its constant strength to its creep strength;

[0020] Step 4: Assume that the filter screen body is blocked. Calculate the maximum stress on the filter screen body under blocked conditions based on the pressure P in the external pressure chamber of the filter screen, and compare it with 50% of its yield strength;

[0021] Step 5: When the comparison results in both Step 3 and Step 4 are less than, it is determined that the strength of the filter screen body is qualified.

[0022] Furthermore, the specific steps of Step 3 are as follows:

[0023] Step 31: Calculate the internal and external pressure difference ΔP of the filter screen body under unobstructed conditions, with the unit of MPa. ΔP is determined by the following formula:

[0024] ΔP = 0.03P

[0025] Step 32: Calculate the maximum stress σ 1max , with the unit of MPa, σ1max It is determined by the following formula:

[0026]

[0027] Where:

[0028] D 1 is the outer diameter of the filter screen body, in mm;

[0029] T is the wall thickness of the filter screen body, in mm;

[0030] Y is the stress factor;

[0031] Step 33: Calculate the maximum stress σ 0max at the inner diameter of the filter screen body, in MPa, σ 0max is determined by the following formula:

[0032]

[0033] Where:

[0034] D 0 is the inner diameter of the filter screen body, in mm;

[0035] T a is the thickness of the straight hole section, in mm;

[0036] Step 34: Calculate the maximum stress σ 2max of the filter screen body under unobstructed conditions, in MPa, σ 2max is determined by the following formula:

[0037]

[0038] Step 35: Query the ten - thousand - hour constant strength and the ten - thousand - hour creep rupture strength of the filter screen body according to the material of the filter screen body and the steam inlet temperature in the valve body

[0039] Then the creep strength of the filter screen body is 2max Compare the maximum stress σ of the filter screen body under unobstructed conditions with the minimum value in the range from the ten - thousand - hour constant strength to the ten - thousand - hour creep rupture strength

[0040] Furthermore, the specific steps of Step 4 are as follows:

[0041] Step 41: Calculate the internal and external pressure difference ΔP 1 of the filter screen body under blocked conditions, in MPa, ΔP 1 is determined by the following formula:

[0042] ΔP 1 = 0.1P * 1.05

[0043] Step 42: Calculate the maximum stress σ on the outer diameter of the filter screen 3max , in MPa, σ 3max is determined by the following formula:

[0044]

[0045] Step 43: Calculate the maximum stress σ on the inner diameter of the filter screen 4max , in MPa, σ 4max is determined by the following formula:

[0046]

[0047] Step 44: Calculate the maximum stress σ on the filter screen body when it is unobstructed 5max , in MPa, σ 5max is determined by the following formula:

[0048]

[0049] Step 45: Query the yield strength σ of the filter screen body according to the material of the filter screen body and the steam inlet temperature in the valve body 0.2 :

[0050] Step 46: Compare the maximum stress σ on the filter screen body when it is blocked 5max with 50% of its yield strength.

[0051] Furthermore, the order of Step 3 and Step 4 can be reversed.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] The pressure sensor of the present invention measures the actual pressure in the valve, and calculates the maximum stress on the filter screen body when it is unobstructed, compares it with the interval from the constant strength to the creep strength of the filter screen body when it is unobstructed, and calculates the maximum stress on the filter screen body when it is blocked, compares it with the yield strength of the filter screen body when it is blocked. If both comparison results are less than, it can be determined that the strength of the filter screen body is qualified. The present invention analyzes and obtains a reliable conclusion through an intelligent algorithm, avoiding frequent replacement of the filter screen body due to insufficient strength of the filter screen body. Description of the Drawings

[0054] Figure 1 is a schematic structural diagram of a steam turbine valve;

[0055] Figure 2 is a cross-sectional view of the filter screen body;

[0056] Figure 3 is the development drawing of the orifice plate;

[0057] Figure 4 is the arrangement drawing of the filter holes;

[0058] Figure 5 is the schematic diagram of the filter holes.

[0059] In the figure: 1 - valve body, 11 - steam inlet, 12 - steam outlet, 13 - external pressure chamber of the filter screen, 2 - inner valve cover, 3 - filter screen body, 31 - filter hole, 311 - tapered hole section, 312 - straight hole section, 4 - valve disc, 5 - valve seat. Specific embodiments

[0060] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described below through specific embodiments shown in the drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0061] The connections mentioned in the present invention are divided into fixed connections and detachable connections. The fixed connection is an inseparable connection including but not limited to conventional fixed connection methods such as flanging connection, rivet connection, bonding connection and welding connection. The detachable connection includes but not limited to conventional disassembly methods such as bolt connection, snap connection, pin connection and hinge connection. When the specific connection method is not clearly defined, it is defaulted that at least one connection method can be found among the existing connection methods to achieve this function, and those skilled in the art can select according to their needs. For example: welding connection is selected for the fixed connection, and bolt connection is selected for the detachable connection.

[0062] The present invention will be further described in detail below with reference to the drawings. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0063] Embodiment: As Figures 1-5As shown in the figure, a strength verification method for a steam turbine filter body is realized relying on a steam turbine valve. The valve can be the main steam valve or the regulating valve of the steam turbine, including a valve body 1. There is a valve cavity inside the valve body 1. The lower end of the valve body 1 is communicated with the valve cavity through a steam inlet 11. The right end of the valve body 1 is communicated with the valve cavity through a steam outlet 12. The left end of the valve body 1 is communicated with the valve cavity through a cut-off control port. An inner valve cover 2 is arranged in the diameter of the cut-off control port. A valve seat 5 is arranged on the diameter of the steam outlet 12. The filter body 3 is tubular. The left end of the filter body 3 is connected to the cut-off control port, and the right end of the filter body 3 is connected to the steam outlet 12. A number of filter holes 31 are arranged on the filter body 3. The filter holes 31 include a tapered hole section 311 and a straight hole section 312 connected from outside to inside. The tapered hole section 311 is a 90° tapered hole converging from outside to inside. A filter outer pressure cavity 13 is formed between the outer circumference of the filter body 3 and the inner circumference of the valve cavity. The right end of the valve rod passes through the inner valve cover 2 and extends into the inner cavity of the filter body 3 and is connected to the valve flap 4. The valve rod is arranged to slide left and right to open and close the valve seat 5. When the valve is opened, the steam inlet 11 is communicated with the steam outlet 12 through the filter outer pressure cavity 13, a number of filter holes 31 and the inner cavity of the filter body 3 in sequence;

[0064] The filter body 3 is formed by rolling a hole plate provided with a number of filter holes 31. The hole plate is a rectangular hole plate, and the long side of the hole plate forms the circumferential direction of the rolled filter body 3;

[0065] A number of filter holes 31 are arranged on the hole plate in an equilateral triangle array. Define three adjacent filter holes 31 forming an equilateral triangle on the hole plate as a minimum triangle unit, and one side of the minimum triangle unit is arranged along the long side direction of the hole plate;

[0066] It includes the following steps:

[0067] Step 1: Measure the pressure P in the filter outer pressure cavity 13 through a pressure sensor, with the unit of MPa. In this embodiment, the measured P is 11.4 MPa;

[0068] Step 2: Define the distance between the two vertex filter holes 31 of two adjacent triangular units with a common side as L, with the unit of mm. In this embodiment, L is taken as 114.3 mm. The shortest distance between the large diameters of the tapered hole sections 311 of the two vertex filter holes 31 is h 1 , with the unit of mm. The shortest distance between the straight hole sections 312 of the two vertex filter holes 31 is h 0 , with the unit of mm;

[0069] h 1 It is determined by the following formula:

[0070] h 1 =L - d 1

[0071] In the formula:

[0072] d 1 is the major diameter of the tapered hole section 311, with the unit of mm. In this embodiment, d 1 is taken as 61.98 mm, and h 1 is calculated to be 52.32 mm;

[0073] h 0 is determined by the following formula:

[0074] h 0 = L - d 0

[0075] In the formula:

[0076] d 0 is the diameter of the straight hole section 312, with the unit of mm. In this embodiment, d 0 is taken as 41.15 mm, and h 0 is calculated to be 73.15 mm;

[0077] Step 3: Assume that the filter screen body 3 is unobstructed, calculate the maximum stress on the filter screen body 3 under the unobstructed condition according to the pressure P in the external pressure chamber 13 of the filter screen, and compare it with the interval from the invariant strength to the creep strength;

[0078] The specific steps of the said Step 3 are as follows:

[0079] Step 31: Calculate the internal and external pressure difference ΔP of the filter screen body 3 under the unobstructed condition, with the unit of MPa. ΔP is determined by the following formula:

[0080] ΔP = 0.03P

[0081] Step 32: Calculate the maximum stress σ 1max , with the unit of MPa. σ 1max is determined by the following formula:

[0082]

[0083] In the formula:

[0084] D 1 is the outer diameter of the filter screen body 3, with the unit of mm. In this embodiment, it is taken as 504.95;

[0085] T is the wall thickness of the filter screen body 3, with the unit of mm. In this embodiment, it is calculated to be 27.05 mm;

[0086] Y is the stress factor, taken as 2.25;

[0087] In this embodiment, σ 1max is calculated to be 14.99 MPa;

[0088] The wall thickness T of the filter screen body 3 is determined by the following formula:

[0089] T = (D 1 - D 0 ) / 2

[0090] Step 33: Calculate the maximum stress σ 0max received at the inner diameter of the filter screen body 3, with the unit of MPa, and σ 0max is determined by the following formula:

[0091]

[0092] In the formula:

[0093] D 0 is the inner diameter of the filter screen body 3, with the unit of mm, and in this embodiment, it is taken as 450.85 mm;

[0094] T a is the thickness of the straight hole section 312, with the unit of mm, and in this embodiment, it is calculated as 16.77 mm;

[0095] In this embodiment, σ 0max is calculated to be 15.45 MPa;

[0096] Step 34: Calculate the maximum stress σ 2max received by the filter screen body 3 under unobstructed conditions, with the unit of MPa, and σ 2max is determined by the following formula:

[0097]

[0098] In this embodiment, σ 2max is calculated to be 15.22 MPa;

[0099] Step 35: Query the ten - thousand - hour constant strength and the ten - thousand - hour creep - rupture strength of the filter screen body 3 according to the material of the filter screen body 3 and the steam inlet temperature in the valve body 1

[0100] In this embodiment, the material of the filter screen body 3 is 1Cr13 and the steam inlet temperature is 549.7 °C, then

[0101] Step 36: Compare the maximum stress σ 2max received by the filter screen body 3 under unobstructed conditions with the minimum value of the range from the ten - thousand - hour constant strength to the ten - thousand - hour creep - rupture strength of the filter screen body 3;

[0102] Step 4: Assume that the filter screen body 3 is blocked, calculate the maximum stress on the filter screen body 3 under the blocked condition according to the pressure P in the external pressure chamber 13 of the filter screen, and compare it with 50% of its yield strength;

[0103] The specific steps of the said Step 4 are as follows:

[0104] Step 41: Calculate the pressure difference ΔP between the inside and outside of the filter screen body 3 under the blocked condition 1 , in MPa, ΔP 1 is determined by the following formula:

[0105] ΔP 1 = 0.1P * 1.05

[0106] In this embodiment, calculating ΔP 1 results in 1.197 MPa;

[0107] Step 42: Calculate the maximum stress σ on the outer diameter of the filter screen body 3 3max , in MPa, σ 3max is determined by the following formula:

[0108]

[0109] In this embodiment, calculating σ 3max results in 52.48 MPa;

[0110] Step 43: Calculate the maximum stress σ on the inner diameter of the filter screen body 3 4max , in MPa, σ 4max is determined by the following formula:

[0111]

[0112] In this embodiment, calculating σ 4max results in 54.07 MPa;

[0113] Step 44: Calculate the maximum stress σ on the filter screen body 3 under the unblocked condition 5max , in MPa, σ 5max is determined by the following formula:

[0114]

[0115] In this embodiment, calculating σ 5max results in 53.27 MPa;

[0116] Step 45: Query the yield strength σ of the filter screen body 3 according to the material of the filter screen body 3 and the steam inlet temperature in the valve body 1 0.2 :

[0117] In this embodiment, the material of the filter screen body 3 is 1Cr13, and the steam inlet temperature is 549.7 °C, then σ0.2 = 419 MPa;

[0118] Step 46: Compare the maximum stress σ 5max experienced by the filter screen body 3 under blocked conditions with 50% of its yield strength;

[0119] Step Five: When the comparison results of Step Three and Step Four are both less than, determine that the strength of the filter screen body 3 is qualified;

[0120] That is, when and then determine that the strength of the filter screen body 3 is qualified, otherwise determine that the strength of the filter screen body 3 is unqualified;

[0121] The order of the above-mentioned Step Three and Step Four can be swapped.

[0122] The pressure sensor of the present invention measures the actual pressure inside the valve, calculates the maximum stress experienced by the filter screen body under unblocked conditions, compares it with the interval from the constant strength to the creep strength of the filter screen body 3 under unblocked conditions, calculates the maximum stress experienced by the filter screen body under blocked conditions, compares it with the yield strength of the filter screen body under blocked conditions, and if both comparison results are less than, it can be determined that the strength of the filter screen body 3 is qualified. The present invention obtains a reliable conclusion through intelligent algorithm analysis, avoiding frequent replacement of the filter screen body due to insufficient strength of the filter screen body 3.

[0123] The above embodiments are only illustrative descriptions of the present invention and do not limit its protection scope. Those skilled in the art can also make partial changes to it, as long as they do not exceed the spirit of the present invention, they are within the protection scope of the present invention.

Claims

1. A strength verification method for a steam turbine filter body, which is realized relying on a steam turbine valve, includes a valve body (1). There is a valve cavity inside the valve body (1). The lower end of the valve body (1) is communicated with the valve cavity through a steam inlet (11). The right end of the valve body (1) is communicated with the valve cavity through a steam outlet (12). The left end of the valve body (1) is communicated with the valve cavity through a cut-off control port. An inner valve cover (2) is arranged inside the diameter of the cut-off control port. A valve seat (5) is arranged on the diameter of the steam outlet (12). The filter body (3) is tubular. The left end of the filter body (3) is connected to the cut-off control port, and the right end of the filter body (3) is connected to the steam outlet (12). A number of filter holes (31) are arranged on the filter body (3). The filter holes (31) include a tapered hole section (311) and a straight hole section (312) connected from outside to inside. The tapered hole section (311) is a 90° tapered hole converging from outside to inside. A filter outer pressure cavity (13) is formed between the outer periphery of the filter body (3) and the inner periphery of the valve cavity. The right end of the valve rod passes through the inner valve cover (2) and extends into the inner cavity of the filter body (3), and is connected to a valve disc (4). The valve rod is arranged to slide left and right to open and close the valve seat (5). When the valve is opened, the steam inlet (11) is communicated with the steam outlet (12) through the filter outer pressure cavity (13), a number of filter holes (31) and the inner cavity of the filter body (3) in sequence; The filter body (3) is formed by rolling a perforated plate provided with a number of filter holes (31). The perforated plate is a rectangular perforated plate, and the long side of the perforated plate forms the circumferential direction of the rolled filter body (3); The perforated plate is provided with a number of filter holes (31) in an equilateral triangle array. Define three adjacent filter holes (31) forming an equilateral triangle on the perforated plate as a minimum triangular unit, and one side of the minimum triangular unit is arranged along the long side direction of the perforated plate; It is characterized in that, including the following steps: Step 1: Measure the pressure P in the filter outer pressure cavity (13) through a pressure sensor, and the unit is MPa; Step 2: Define the distance between two vertex filter holes (31) on the opposite sides of the two adjacent triangular units as L, with the unit of mm. The shortest distance between the major diameters of the tapered hole sections (311) of the two vertex filter holes (31) is h 1 , with the unit of mm. The shortest distance between the straight hole sections (312) of the two vertex filter holes (31) is h 0 , with the unit of mm; h 1 Determined by the following formula: h 1 = L - d 1 In the formula: d 1 is the major end diameter of the tapered hole section (311), in mm; h 0 determined by the following formula: h 0 = L - d 0 In the formula: d 0 is the diameter of the straight hole section (312), in mm; Step 3: Assume that the filter body (3) is unobstructed, calculate the maximum stress suffered by the filter body (3) under the unobstructed condition according to the pressure P in the filter outer pressure cavity (13), and compare it with the interval from the invariant strength to the creep strength; Step 4: Assume that the filter body (3) is blocked, calculate the maximum stress suffered by the filter body (3) under the blocked condition according to the pressure P in the filter outer pressure cavity (13), and compare it with 50% of its yield strength; Step 5: When the comparison results of Step 3 and Step 4 are both less than, it is determined that the strength of the filter body (3) is qualified.

2. The strength verification method for a steam turbine filter body according to claim 1, it is characterized in that, the specific steps of Step 3 are: Step 31: Calculate the internal and external pressure difference ΔP of the filter body (3) under the unobstructed condition, and the unit is MPa. ΔP is determined by the following formula: ΔP = 0.03P Step 32: Calculate the maximum stress σ on the outer diameter of the filter body (3) 1max , in MPa, σ 1max is determined by the following formula: In the formula: D 1 is the outer diameter of the filter mesh body (3), in mm; T is the wall thickness of the filter body (3), and the unit is mm; Y is the stress factor; Step 33: Calculate the maximum stress σ 0max received at the inner diameter of the filter body (3), in MPa, where σ 0max is determined by the following formula: In the formula: D 0 is the inner diameter of the filter mesh body (3), with the unit of mm; T a is the thickness of the straight hole section (312), in mm; Step 34: Calculate the maximum stress σ 2max received by the filter body (3) when it is unobstructed, in MPa, where σ 2max is determined by the following formula: Step 35: Query the 100,000-hour constant strength and the 100,000-hour creep rupture strength of the filter screen body (3) according to the material of the filter screen body (3) and the inlet steam temperature in the valve body (1). and the 100,000-hour creep rupture strength Then the creep strength of the filter screen body (3) is Step 36: Compare the maximum stress σ 2max that the filter screen body (3) is subjected to under unobstructed conditions with the minimum value in the range from the ten - thousand - hour constant strength to the ten - thousand - hour creep strength of the filter screen body (3).

3. The strength verification method for a steam turbine filter body according to claim 2, it is characterized in that, the specific steps of Step 4 are: Step 41: Calculate the pressure difference ΔP between the inside and outside of the filter body (3) in the case of blockage 1 , with the unit of MPa, ΔP 1 is determined by the following formula: ΔP 1 = 0.1P * 1.05 Step 42: Calculate the maximum stress σ on the outer diameter of the filter body (3) 3max , in MPa, σ 3max is determined by the following formula: Step 43: Calculate the maximum stress σ on the inner diameter of the filter body (3) 4max , with the unit of MPa, σ 4max is determined by the following formula: Step 44: Calculate the maximum stress σ suffered by the filter body (3) under unobstructed conditions 5max , with the unit of MPa, σ 5max is determined by the following formula: Step 45: Query the yield strength σ of the filter screen body (3) based on the material of the filter screen body (3) and the inlet steam temperature in the valve body (1) 0.2 :[[]]END]] Step 46: Compare the maximum stress σ 5max experienced by the filter body (3) in the case of blockage with 50% of its yield strength.

4. A method for verifying the strength of a steam turbine filter body according to claim 3, characterized in that, the order of said step three and said step four can be swapped.

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