A design method of a ship maneuvering steam bypass discharge device under anti-skid parameter conditions

Abstract

The application provides a design method of a ship maneuvering steam bypass discharge device under a high parameter, compact, integrated and wide-range efficient anti-sliding parameter condition, which comprehensively considers the structural characteristics of the existing ship steam bypass system steam discharge device, and the characteristic requirements of the new ship device for realizing the power multiplication of the unit and the maneuvering operation bypass regulation under the condition that the cabin capacity is basically unchanged, and summarizes the compact structure design method of the steam bypass discharge device, the variable working condition parameter calculation and analysis method, thereby guiding the design and variable working condition analysis of the new ship small-size, high-parameter, continuous and variable load steam bypass discharge device.

Description

Technical Field

[0001] This invention belongs to the field of marine steam power system design, specifically relating to a design method for a ship's motorized steam bypass emission device under antislip parameter conditions. Background Technology

[0002] Steam bypass systems are crucial equipment in once-through boiler power plants, large thermal power plants, and especially in steam power systems such as nuclear power and marine plants. When a steam turbine unit starts up, shuts down, sheds load, or changes load, a large amount of high-temperature, high-pressure steam must bypass the turbine and be discharged into the condenser, either temporarily or continuously. From the perspectives of unit operation economy, safety and reliability, and environmental protection, it is necessary to install a reasonable steam bypass system in the thermal system to effectively de-heat and depressurize the high-temperature, high-pressure steam, thus preventing high-speed, high-temperature steam flow from damaging the condenser throat, cooling pipes, and the low-pressure cylinder of the turbine.

[0003] Steam bypass venting devices are typically located on the condenser, employing a multi-stage steam criticality and small-hole water spray depressurization and cooling principle. These devices are bulky, and the small-hole water spray vaporization is difficult to achieve fully and effectively. Furthermore, they are only operational during safe venting conditions in emergency shutdowns of the unit. New marine systems require doubling the unit's power output while maintaining a relatively constant cabin volume. Therefore, the system and related equipment need to be designed with high parameters for compactness, integration, and wide-range efficiency. In response to these requirements and the current technological status, the following technical problems need to be addressed.

[0004] The advanced integrated design of the ship's steam propulsion system, which shares a condenser and a sea-access cold source center, reduces the space required for the bypass discharge device. Given the operational characteristics of the ship's integrated pressurized water reactor, the steam bypass discharge device must participate in low-power steam load regulation and will operate continuously, under variable loads for extended periods. Therefore, precise control of the steam bypass discharge device under varying operating conditions is necessary to ensure the long-term safe and reliable operation of the system. Typically, steam bypass discharge devices are designed based on maximum operating steam parameters, which cannot meet the requirements for the refined design and analysis of mobile steam bypass discharge devices under reverse slip parameter conditions.

[0005] Chinese patent application publication number CN 203626902 U discloses a bypass discharge device for a vacuum system. Its characteristic is that several exhaust holes are opened at the bottom of the steam inlet pipe, connecting the steam inlet pipe and the inner cavity. Several arc-shaped expansion plates, arranged sequentially from the inside out, surround the outside of the steam inlet pipe. The opening directions of these expansion plates are arranged in opposite directions to form a pressure-reducing channel that facilitates the back-and-forth flow and outward diffusion of high-temperature, high-pressure steam. This device can expand and reduce the pressure of steam from 0.5–0.7 MPaG to 0.03 MPaA. However, the pressure reduction ratio is relatively small, making it unsuitable for the compact design of high-parameter steam discharge devices.

[0006] Chinese patent application publication number CN 204165420 U discloses a built-in large-capacity bypass discharge pipe for a 1,000 MW nuclear power plant condenser. This design involves opening a primary pressure-reducing hole on the outer wall of the inner cylinder of the discharge pipe to expand the steam entering the bypass pipe, and then opening a secondary pressure-reducing hole on the inner wall of the outer cylinder to further reduce the steam pressure. Finally, the steam enters the steam-side space of the condenser, enabling the condenser to receive bypass steam and ensuring the long-term stable operation of the bypass system and condenser of the 1,000 MW nuclear power unit. However, this bypass discharge pipe is composed of multiple connected discharge pipe units, occupying a large space, and only reduces the pressure of the exhaust steam without desuperheating it. Summary of the Invention

[0007] The purpose of this invention is to develop a design method for a ship's motorized steam bypass emission device under antislip parameter conditions that is high-parameter, compact, integrated, and highly efficient, taking into account the limited space and maneuvering characteristics of new ship equipment.

[0008] A design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions includes the following steps:

[0009] S1, Design boundary conditions; The steam parameters of the bypass system under the maximum emission condition are used as design inputs, mainly including bypass emission steam parameters, desuperheating water parameters and cold source terminal back pressure;

[0010] S2, determine the number of bypass discharge boxes and the structural form of orifice plates at each stage;

[0011] S3, determine the number of decompression stages and the decompression ratio of each stage;

[0012] S4, calculate the steam parameters and the number of orifice openings for each stage; given the single orifice diameter for each stage, calculate the steam parameters for each stage based on the pressure reduction ratio and isenthalpic expansion theory for each stage, and calculate the number of orifice openings based on the flow calculation formula (1) or (2) derived from the energy conservation and ideal gas characteristics, to ensure sufficient number of openings and expansion space so that the steam can continue to expand to the design value after leaving the throttling orifice.

[0013] For superheated steam

[0014] For dry saturated steam

[0015] Where G is the flow rate through the throttle orifice, kg / s; β is the valve throttle coefficient; is the flow coefficient; A is the orifice area, m 2 p0 is the steam pressure at the orifice inlet, Pa; ν0 is the steam specific volume at the orifice inlet, m³. 3 / kg;

[0016] S5, calculate the safety diffusion distance at each level;

[0017] S6, calculate the longitudinal and transverse pitch of the orifice plates at each stage;

[0018] S7, calculate the steam flow rate in each expansion space;

[0019] S8, calculate the desuperheating water flow rate and the number of openings;

[0020] S9 completes the structural design of the steam bypass discharge device and the calculation of steam parameters at each stage, and performs verification and analysis of the variable operating condition parameters of the steam bypass discharge device.

[0021] Furthermore, in S3, the number of pressure reduction stages is determined based on the steam pressure and cold source terminal back pressure under the maximum emission condition, and the pressure reduction ratio of each stage is allocated to ensure supercritical expansion of steam at each stage.

[0022] Furthermore, the supercritical expansion of steam in S5 results in a high flow velocity. In order to avoid the impact and erosion of the components by the steam flow, the distance required for safe diffusion of the steam flow is calculated by formula (3).

[0023] L = 1.8L s d0 (3)

[0024] Among them, L s d is the supersonic length coefficient, in mm; d0 is the orifice diameter, in mm.

[0025] Furthermore, in S6, in order to prevent the vapor flow from overlapping within the safe diffusion distance, the adjacent throttling orifices need to maintain a certain pitch in the longitudinal and transverse directions, calculated according to formula (4);

[0026]

[0027] Where, ν s For the specific volume of steam at the outlet of the throttle orifice, m 3 / kg.

[0028] Furthermore, in S7, the flow rate of steam after expansion at each stage is limited by the flow area, and the steam flow rate is not greater than 120m / s.

[0029] Furthermore, in S8, the desuperheating water flow rate is calculated according to the heat balance formula (5) to ensure that the steam at this stage is in a saturated state. At the same time, the steam flow rate of a single throttling orifice is calculated according to the fluid dynamics theory formula (6), thereby determining the number of nozzle orifices under the total flow rate.

[0030] (G s +G L h0=G s h s +G L h L (5)

[0031] Among them, Gs The steam flow rate entering the bypass box is kg / s; G L The desuperheating water flow rate is kg / s; h0 is the saturated steam enthalpy, kJ / kg.

[0032]

[0033] Where Δp is the pressure difference through the throttling orifice, in MPa; υ L To reduce the specific volume of the heated water, m 3 / kg.

[0034] Furthermore, the steps for calculating and analyzing the variable operating condition parameters of the steam bypass discharge device in S9 are as follows:

[0035] S9.1, Design input for various operating conditions; mainly includes bypass steam discharge flow rate G under different operating conditions. s Enthalpy value H 01 Cold source terminal back pressure P z Desuperheating water can provide a minimum pressure P lm ;

[0036] S9.2, the initial setting of the steam pressure P1 before the final stage, and the bypass discharge device generally sprays water to cool down to the saturation state below P1 in the secondary and final stages.

[0037] S9.3, G0 is calculated according to formula (2), which is the steam flow rate discharged to the cold source terminal after pressure reduction and cooling by the bypass discharge device;

[0038] S9.4, calculate the exhaust steam flow rate G based on heat balance. 01 Calculate the bypass emission steam G s Steam flow rate G after water spray cooling reaches saturation 01 =G s +G L ;

[0039] S9.5, determine whether the current iteration is complete; if |G 01 If -G0| / G0≤1%, proceed to the next calculation; otherwise, proceed according to G. 01 Calculate the new steam pressure P1' before the final stage, set P1 = P1', and continue iterative calculation until the error requirement is met;

[0040] S9.6 Calculate the relevant parameters before and after the last stage. The steam after the water spray before the last stage is saturated steam. According to the isenthalpic expansion theory, the steam pressure, temperature, enthalpy value, flow rate and temperature of the steam after the water spray before the last stage are finally obtained.

[0041] S9.7, Desuperheating water flow control optimization and safety and reliability analysis of cold source terminal: Based on the steam pressure before the last stage and the required desuperheating water flow, calculate the desuperheating water pressure and optimize the desuperheating water flow control design; Based on the steam temperature and flow before and after the last stage, calculate and analyze the temperature field, flow field and stress field of the cold source terminal under various operating conditions.

[0042] S9.8 calculates parameters at each level and optimizes valve selection step by step. Finally, it calculates the steam pressure P0 of the steam bypass discharge device under various operating conditions and flow rates, optimizing the valve characteristic curves and selection for the bypass steam system.

[0043] S9.9, completes the calculation and analysis of the variable operating parameters of each stage of the bypass emission device.

[0044] The beneficial effects of this invention are as follows:

[0045] (1) The compact structure design method of the steam bypass discharge device is based on the maximum operating steam parameters. The pressure is reduced by supercritical expansion through small hole throttling and the temperature is reduced by spraying water through mechanical atomizing nozzles.

[0046] (2) Calculation and analysis method of variable operating condition parameters of steam bypass discharge device: Based on the actual physical process of device operation and theoretical model, the variable operating condition parameters of steam bypass discharge device are calculated and analyzed, and the steam inlet parameters, desuperheating water flow rate and discharge steam parameters under different operating conditions are obtained, providing clear boundary conditions for the selection of bypass steam valves, design of desuperheating water control system and safety analysis of exhaust steam receiving device of ship bypass discharge system. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating the structural design of the present invention;

[0048] Figure 2 This is a structural diagram of the present invention;

[0049] Figure 3 This is a flowchart of the variable operating condition calculation for the present invention. Detailed Implementation

[0050] The present invention will now be further described with reference to the accompanying drawings.

[0051] The steam bypass emission device features a compact structural design, combined with Figure 1 The structural design flowchart uses steam parameters under the maximum bypass system safe discharge condition to design and calculate steam parameters for each stage of the structure, ensuring sufficient number of openings and expansion space so that the steam can supercritically expand to the design value after leaving the throttling orifice. This achieves pressure reduction and cooling of high-parameter superheated steam with a smaller number of stages and a compact structure, and safely discharges it into the cold source terminal.

[0052] S1, Design boundary conditions. The steam parameters of the bypass system under maximum emission conditions are used as design inputs, mainly including bypass emission steam parameters, desuperheating water parameters, and back pressure of the cold source terminal;

[0053] S2, determine the number of bypass discharge boxes and the structural form of each orifice plate. Based on the actual layout space, maximum operating conditions, and steam flow rates under various operating conditions, determine the number of bypass discharge boxes and the structural form of each stage to ensure conformal spatial layout and precise control during variable operating conditions;

[0054] S3, determine the number of pressure reduction stages and the pressure reduction ratio of each stage. Based on the steam pressure and cold source terminal back pressure under maximum emission conditions, determine the number of pressure reduction stages and allocate the pressure reduction ratio of each stage to ensure supercritical steam expansion at each stage;

[0055] S4, calculate the steam parameters and the number of orifice openings for each stage; given the single orifice diameter for each stage, calculate the steam parameters for each stage based on the pressure reduction ratio and isenthalpic expansion theory for each stage, and calculate the number of orifice openings based on the flow calculation formula (1) or (2) derived from the energy conservation and ideal gas characteristics, to ensure sufficient number of openings and expansion space so that the steam can continue to expand to the design value after leaving the throttling orifice.

[0056] For superheated steam

[0057] For dry saturated steam

[0058] Where G is the flow rate through the throttle orifice, kg / s; β is the valve throttle coefficient; is the flow coefficient; A is the orifice area, m 2 p0 is the steam pressure at the orifice inlet, Pa; ν0 is the steam specific volume at the orifice inlet, m³. 3 / kg;

[0059] S5, calculate the safe diffusion distance at each stage; the supercritical expansion of steam leads to a high flow velocity. In order to avoid the impact and erosion of the steam flow on the components, the distance required for safe diffusion of the steam flow is calculated by formula (3);

[0060] L = 1.8L s d0 (3)

[0061] Among them, L s d is the supersonic length coefficient, mm; d0 is the orifice diameter, mm;

[0062] S6, calculate the longitudinal and transverse pitch of the orifice plates at each level; in order to ensure that the steam flow does not overlap within the safe diffusion distance, the longitudinal and transverse pitches of adjacent orifices need to be maintained at a certain level, calculated according to formula (4);

[0063]

[0064] Where, ν s For the specific volume of steam at the outlet of the throttle orifice, m 3 / kg;

[0065] S7, calculate the steam velocity in each expansion space; limit the steam velocity after expansion by the flow area, the steam velocity should not exceed 120m / s;

[0066] S8, calculate the desuperheating water flow rate and the number of openings; calculate the desuperheating water flow rate according to the heat balance formula (5) to ensure that the steam of this stage is saturated, and calculate the steam flow rate of a single throttling orifice according to the fluid dynamics theory formula (6) to determine the number of nozzle holes under the total flow rate.

[0067] (G s +G L h0=G s h s +G L h L (5)

[0068] Among them, G s The steam flow rate entering the bypass box is kg / s; G L The desuperheating water flow rate is kg / s; h0 is the saturated steam enthalpy, kJ / kg.

[0069]

[0070] Where Δp is the pressure difference through the throttling orifice, in MPa; υ L To reduce the specific volume of the heated water, m 3 / kg.

[0071] Complete the structural design of the steam bypass discharge device and the calculation of steam parameters for each stage;

[0072] Combined with appendix Figure 2 The structural diagram of the bypass discharge device is shown below. The structure is briefly described. The bypass high-pressure high-temperature steam enters the bypass discharge device through the steam inlet pipe 1. After being depressurized by the first-stage orifice pipe 2 and undergoing supercritical expansion, it is sprayed and atomized by the desuperheating water pipe 3. It is fully mixed and cooled to saturation in the space of the second-stage cylinder 4. After being depressurized by the second-stage depressurization cone 5 and becoming superheated steam, it is discharged after expansion in the steam outlet cylinder 6.

[0073] Combination Figure 3The variable operating condition calculation flowchart calculates the steam parameters and desuperheating water volume at each stage under the design structural conditions, including unit start-up and shutdown, and low-power load regulation. This optimizes the selection of bypass steam valves, the precise design of desuperheating water flow control, and the safety and reliability analysis of the exhaust steam receiving device. Since the back pressure of the bypass cold source terminal is usually known under different operating conditions, the variable operating condition calculation of the exhaust device generally iterates backward from the last stage steam parameters.

[0074] S9, Calculation and analysis of variable operating condition parameters for steam bypass discharge device:

[0075] S9.1, Design input for various operating conditions; mainly includes bypass steam discharge flow rate G under different operating conditions. s Enthalpy value H 01 Cold source terminal back pressure P z Desuperheating water can provide a minimum pressure P lm ;

[0076] S9.2, the initial setting of the steam pressure P1 before the final stage, and the bypass discharge device generally sprays water to cool down to the saturation state below P1 in the secondary and final stages.

[0077] S9.3, G0 is calculated according to formula (2), which is the steam flow rate discharged to the cold source terminal after pressure reduction and cooling by the bypass discharge device;

[0078] S9.4, calculate the exhaust steam flow rate G based on heat balance. 01 Calculate the bypass emission steam G s Steam flow rate G after water spray cooling reaches saturation 01 =G s +G L ;

[0079] S9.5, determine whether the current iteration is complete; if |G 01 If -G0| / G0≤1%, proceed to the next calculation; otherwise, proceed according to G. 01 Calculate the new steam pressure P1' before the final stage, set P1 = P1', and continue iterative calculation until the error requirement is met;

[0080] S9.6 Calculate the relevant parameters before and after the last stage. The steam after the water spray before the last stage is saturated steam. According to the isenthalpic expansion theory, the steam pressure, temperature, enthalpy value, flow rate and temperature of the steam after the water spray before the last stage are finally obtained.

[0081] S9.7, Desuperheating water flow control optimization and safety and reliability analysis of cold source terminal: Based on the steam pressure before the last stage and the required desuperheating water flow, calculate the desuperheating water pressure and optimize the desuperheating water flow control design; Based on the steam temperature and flow before and after the last stage, calculate and analyze the temperature field, flow field and stress field of the cold source terminal under various operating conditions.

[0082] S9.8 calculates parameters at each level and optimizes valve selection step by step. Finally, it calculates the steam pressure P0 of the steam bypass discharge device under various operating conditions and flow rates, optimizing the valve characteristic curves and selection for the bypass steam system.

[0083] S9.9, completes the calculation and analysis of the variable operating parameters of each stage of the bypass emission device.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions, characterized in that, Includes the following steps: S1, Design boundary conditions; The steam parameters of the bypass system under the maximum emission condition are used as design inputs, including bypass emission steam parameters, desuperheating water parameters, and back pressure of the cold source terminal. S2, determine the number of bypass discharge boxes and the structural form of orifice plates at each stage; S3, determine the number of decompression stages and the decompression ratio of each stage; S4, calculate the steam parameters and the number of orifice openings for each stage; given the single orifice diameter for each stage, calculate the steam parameters for each stage based on the pressure reduction ratio and isenthalpic expansion theory for each stage, and calculate the number of orifice openings based on the flow calculation formula (1) or (2) derived from the energy conservation and ideal gas characteristics, to ensure sufficient number of openings and expansion space so that the steam can continue to expand to the design value after leaving the throttling orifice; For superheated steam (1) For dry saturated steam (2) in, The flow rate through the orifice is expressed in kg / s. For valve Pengtai gate coefficient; For flow coefficient; The area of ​​the throttling orifice is m. 2 , ; The inlet steam pressure of the throttling orifice is in Pa; For the specific volume of steam at the inlet of the throttling orifice, m 3 / kg; S5, calculate the safety diffusion distance at each level; S6, calculate the longitudinal and transverse pitch of the orifice plates at each stage; S7, calculate the steam flow rate in each expansion space; S8, calculate the desuperheating water flow rate and the number of openings; S9, complete the structural design of the steam bypass discharge device and the calculation of steam parameters at each stage, and perform calculation and analysis of the variable operating condition parameters of the steam bypass discharge device; The steps for calculating and analyzing the variable operating parameters of the steam bypass discharge device are as follows: S9.1, Design input for various operating conditions; including bypass steam discharge flow rate G under different operating conditions. s Enthalpy value H 01 Cold source terminal back pressure P z Desuperheating water can provide a minimum pressure P lm ; S9.2, the initial setting of the steam pressure P1 before the final stage, and the bypass discharge device generally sprays water to cool down to the saturation state below P1 in the secondary and final stages. S9.3, G0 is calculated according to formula (2), which is the steam flow rate discharged to the cold source terminal after pressure reduction and cooling by the bypass discharge device; S9.4, calculate the exhaust steam flow rate G based on heat balance. 01 Calculate the bypass emission steam G s Steam flow rate G after water spray cooling reaches saturation 01 =G s +G L ; S9.5, determine whether the current iteration is complete, if |G 01 If G0| / G0≤1%, proceed to the next calculation; otherwise, proceed according to G. 01 Calculate the new pre-stage steam pressure P1 ’ Let P1 = P1 ’ Continue iterative calculations until the error requirement is met; S9.6 Calculate the relevant parameters before and after the last stage. The steam after the water spray before the last stage is saturated steam. According to the isenthalpic expansion theory, the steam pressure, temperature, enthalpy value, flow rate and temperature of the steam after the water spray before the last stage are finally obtained. S9.7, Desuperheating water flow control optimization and safety and reliability analysis of cold source terminal: Based on the steam pressure before the last stage and the required desuperheating water flow, calculate the desuperheating water pressure and optimize the desuperheating water flow control design; Based on the steam temperature and flow before and after the last stage, calculate and analyze the temperature field, flow field and stress field of the cold source terminal under various operating conditions. S9.8 calculates parameters at each level and optimizes valve selection step by step; finally, it calculates the steam pressure P0 of the steam bypass discharge device under various operating conditions and flow rates, and optimizes the valve characteristic curves and selection of the bypass steam system. S9.9, completes the calculation and analysis of the variable operating parameters of each stage of the bypass emission device.

2. The design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions according to claim 1, characterized in that, In S3, the number of pressure reduction stages is determined based on the steam pressure and back pressure of the cold source terminal under the maximum emission condition, and the pressure reduction ratio of each stage is allocated to ensure supercritical expansion of steam at each stage.

3. The design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions according to claim 1, characterized in that, In S5, the supercritical expansion of steam leads to a high flow velocity. In order to avoid the impact and erosion of the components by the steam flow, the distance required for safe diffusion of the steam flow is calculated by formula (3). L=1.8L s d0(3) Among them, L s d is the supersonic length coefficient, in mm; d0 is the orifice diameter, in mm.

4. The design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions according to claim 1, characterized in that, In S6, to ensure that the steam flow does not overlap within the safe diffusion distance, the adjacent throttling orifices need to maintain a certain pitch in the longitudinal and transverse directions, calculated according to formula (4); （4） in, For the specific volume of steam at the outlet of the throttle orifice, m 3 / kg.

5. The design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions according to claim 1, characterized in that, In S7, the flow rate of steam after expansion at each stage is limited by the flow area, and the steam flow rate is not greater than 120m / s.

6. The design method for a ship's motorized steam bypass emission device under anti-slip parameter conditions according to claim 1, characterized in that, In the S8, the desuperheating water flow rate is calculated according to the heat balance formula (5) to ensure that the steam of this stage is in a saturated state. At the same time, the steam flow rate of a single throttling orifice is calculated according to the fluid dynamics theory formula (6) to determine the number of nozzle orifices under the total flow rate. (G s +G L )h0=G s h s +G L h L (5) Among them, G s The steam flow rate entering the bypass box is kg / s; G L The desuperheating water flow rate is kg / s; h0 is the saturated steam enthalpy, kJ / kg. （6） in, The pressure difference through the throttling orifice, in MPa; To reduce the specific volume of the heated water, m 3 / kg.

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