A Simulation Method for the Characteristics of Condenser Return Water Butterfly Valve

Abstract

The present invention discloses a condenser return water butterfly valve characteristic simulation calculation method. The method, according to a circulating water system diagram of a power station expansion unit, connects a circulating water pump module, a motor module, a condenser module and a return water butterfly valve module in series and parallel to form a circulating water pipeline. Based on the characteristic equation group of the circulating water pump, the condenser and the return water butterfly valve, and taking into account the pipeline elevation difference, the circulating water main pipe pressure, the pressure before / after the valve of each return water butterfly valve, the total flow of the circulating water main pipe, the water inlet flow of each condenser and the motor power under different relative openings of the return water butterfly valve are solved to guide the operation of the power station circulating water system.

Description

Technical Field

[0001] The invention relates to a condenser return water butterfly valve characteristic simulation calculation method, belonging to the technical field of thermal power generation. Background Art

[0002] For power plant units using open circulating water systems, although most are equipped with a vacuum pump at the condenser outlet water chamber to prevent the siphoning effect, the vast majority still rely on a throttling return water butterfly valve to establish a slight positive pressure in the condenser outlet water chamber to ensure safe operation of the circulating water system. To understand the throttling characteristics of the return water butterfly valve and guide its operation, this paper proposes a method for simulating and calculating the characteristics of a condenser return water butterfly valve. Summary of the Invention

[0003] The purpose of the present invention is to understand the throttling characteristics of the return water butterfly valve and guide its operation. The present invention proposes a condenser return water butterfly valve characteristic simulation calculation method.

[0004] The technical solution implemented by the present invention is as follows: a condenser return water butterfly valve characteristic simulation calculation method, characterized in that the method is based on the power station expanded unit system circulating water system diagram, and the circulating water pump module, motor module, condenser module and return water butterfly valve module are connected in series and in parallel to form a circulating water pipeline; based on the characteristic equation group of the circulating water pump, condenser and return water butterfly valve, and considering the pipeline elevation difference, the circulating water main pipe pressure, the pressure before / after the valve of each return water butterfly valve, the total flow of the circulating water main pipe, the water inlet flow of each condenser and the motor power under different relative openings of the return water butterfly valve are solved to guide the operation of the power station circulating water system.

[0005] Furthermore, the method specifically includes the following steps: according to the circulating water system diagram of the power station expansion unit, a plurality of circulating water pump modules, motor modules, condenser modules and return water butterfly valve modules are connected in series and in parallel to form a circulating water pipeline, wherein the plurality of circulating water pump modules are connected in parallel, the outlets of the circulating water pump modules are combined and connected in series to the inlet of the circulating water inlet main pipe; the outlets of the circulating water main pipe are divided and connected in series to the inlets of the condenser modules; the outlets of the condenser modules are connected in series to the inlet of the corresponding return water butterfly valve module; the outlets of all the return water butterfly valve modules are combined and connected in series to the inlet of the circulating water return main pipe;

[0006] Establish characteristic equations for the circulating water pump module, condenser module, and return water butterfly valve module. Integrate the manufacturer's flow-head / efficiency characteristic curve at rated speed into the circulating water pump module. Calculate flow, head, efficiency, and motor power under constant or variable speed operating conditions based on the centrifugal pump proportionality law.

[0007] The water side resistance of the condenser module is calculated as follows:

[0008] ΔPW =ΔP a +ΔP b +ΔP c +ΔP d ,

[0009] ΔP a =LΔP L R t ,

[0010] ΔP L =28.72(V W ) 1.75 / (d i ) 1.25 ,

[0011] Where:

[0012] ΔP W ——Total water resistance of cooling water passing through condenser, kPa;

[0013] ΔP a ——Frictional water resistance in the condenser tube, kPa;

[0014] ΔP b ——Water resistance at the end of the condenser tube, kPa;

[0015] ΔP c ——Condenser water chamber inlet water resistance, kPa;

[0016] ΔP d ——water resistance at the outlet of condenser water chamber, kPa;

[0017] ΔP b , ΔP c , ΔP d Calculated based on the water velocity in the condenser tube and the characteristic curve equation provided by the American Heat Exchange Institute HEIStandard SteamSurface Condensers;

[0018] The return butterfly valve module uses the following formula to calculate flow and resistance:

[0019] when When it is a non-blocking flow, the calculation formula is:

[0020]

[0021] when When it is a blocking flow, the calculation formula is:

[0022]

[0023] Where:

[0024] QmL ——Mass flow rate flowing through the return water butterfly valve, t / h;

[0025] K v ——Flow coefficient of backwater butterfly valve, m 3 / h;

[0026] Δp——pressure difference before and after the return water butterfly valve, MPa;

[0027] p1——pressure before valve, MPa;

[0028] p2——pressure after valve, MPa;

[0029] ρ L ——Density of the liquid, kg / m 3 .

[0030] F L ——Pressure recovery coefficient, value is 0.9;

[0031]

[0032] Where:

[0033] F F ——critical pressure ratio coefficient of liquid;

[0034] p v ——Liquid saturated steam pressure at the inlet temperature of the return butterfly valve, pressure before the valve, MPa;

[0035] p c ---Liquid critical pressure, MPa; the critical pressure of water is 22.064 MPa.

[0036] The relative opening L of the return water butterfly valve provided by the manufacturer and the flow coefficient K v The characteristic curve is built into each return butterfly valve module;

[0037] Since the circulating water pump, condenser, and return water butterfly valve are located at different altitudes, they directly affect the resistance characteristics of the circulating water pipeline. To simplify the calculation, the altitude difference between the circulating water pump suction port and the return water butterfly valve outlet is regarded as the elevation difference between the upstream and downstream interfaces of the circulating water pipeline.

[0038] Each return butterfly valve is set with different relative openings, according to the relative opening L of the return butterfly valve and the flow coefficient K v Characteristic curve, get the corresponding flow coefficient K vAssuming a certain total flow of a circulating water main pipe, the above characteristic equations are combined, and the pressures behind each return water butterfly valve are made equal to each other and equal to the converted value of atmospheric pressure after considering the elevation difference of the circulating water pipe, and the appropriate total flow of the circulating water main pipe and the circulating water main pipe pressure, the pressure before / after each return water butterfly valve, the water inlet flow of each condenser, the motor power, etc. are solved iteratively.

[0039] The beneficial effect of the present invention is that it simplifies and constructs an expanded unit-based circulating water system in a series and parallel manner, and by combining the characteristic equations of the circulating water pump, condenser and return water butterfly valve, taking into account the pipeline elevation difference, accurately solves the influence of the condenser return water butterfly valve on the total flow of the circulating water main pipe, the circulating water main pipe pressure, the pressure before / after the valve of each return water butterfly valve, the water inlet flow of each condenser, the motor power and other characteristic parameters, which helps to guide the safe and economical operation of the power station circulating water system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of a circulating water system for an expanded unit according to an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of flow characteristics of a backwater butterfly valve according to an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of the relative opening-flow characteristics of the return water butterfly valve in Example #1 of the present invention;

[0043] Figure 4 Schematic diagram of the relative opening-power consumption characteristics of the return water butterfly valve in Example #1 of the present invention; DETAILED DESCRIPTION

[0044] The specific implementation of the present invention is shown in the figure. Figure 1 , Attachment Figure 2 and attached Figure 3 , clearly and completely describe the technical solutions in the embodiments of the present invention.

[0045] This embodiment is a circulating water system for an expanded unit of a certain 4*300MW unit. The condenser adopts open circulation cooling, and each unit is equipped with 2 circulating water pumps, for a total of 8 pumps in the whole plant.

[0046] An embodiment of the present invention provides a condenser return water butterfly valve characteristic simulation calculation method, characterized in that the method, based on the power station expanded unit system circulating water system diagram, connects the circulating water pump module, the motor module, the condenser module and the return water butterfly valve module in series and parallel to form a circulating water pipeline; based on the characteristic equation group of the circulating water pump, the condenser and the return water butterfly valve, solves the characteristic parameters such as the circulating water main pipe pressure, the pressure before / after the valve of each return water butterfly valve, the total flow of the circulating water main pipe, the water inlet flow of each condenser and the motor power under different relative openings of the return water butterfly valve to guide the operation of the power station circulating water system.

[0047] The following steps are involved:

[0048] As attached Figure 1 As shown in the figure, based on the circulating water system diagram for the power plant expansion unit, several circulating water pump modules, motor modules, condenser modules, and return water butterfly valve modules are connected in series and parallel to form a circulating water pipeline. Specifically, the circulating water pump modules are connected in parallel, with the outlets of each circulating water pump module combined and connected in series to the inlet of the circulating water inlet main pipe; the outlet of the circulating water main pipe is divided and connected in series to the inlet of each condenser module; the outlet of each condenser module is connected in series to the inlet of the corresponding return water butterfly valve module; and the outlets of all return water butterfly valve modules are combined and connected in series to the inlet of the circulating water return main pipe.

[0049] The characteristic equation groups of the circulating water pump module, condenser module and return water butterfly valve module are established respectively according to the following method.

[0050] The flow-head / efficiency characteristic curve at rated speed provided by the manufacturer is built into the circulating water pump module; and based on the proportional law of centrifugal pumps, the flow, head, efficiency and motor power are calculated under constant speed or variable speed conditions.

[0051] The water side resistance of the condenser module is calculated as follows:

[0052] ΔP W =ΔP a +ΔP b +ΔP c +ΔP d ,

[0053] ΔP a =LΔP L R t ,

[0054] ΔP L =28.72(V W ) 1.75 / (d i ) 1.25 ,

[0055] Where:

[0056] ΔP W ——Total water resistance of cooling water passing through condenser, kPa;

[0057] ΔP a ——Frictional water resistance in the condenser tube, kPa;

[0058] ΔP b ——Water resistance at the end of the condenser tube, kPa;

[0059] ΔP c ——Condenser water chamber inlet water resistance, kPa;

[0060] ΔP d ——water resistance at the outlet of condenser water chamber, kPa;

[0061] ΔP b , ΔP c , ΔP d It is obtained based on the water velocity in the condenser tube and the characteristic curve equation provided by the American Heat Exchange Institute HEIStandard SteamSurface Condensers.

[0062] The return butterfly valve module uses the following formula to calculate flow and resistance:

[0063] when For non-blocking flow, the calculation formula is:

[0064]

[0065] when When it is a blocking flow, the calculation formula is:

[0066]

[0067] Where:

[0068] Q mL ——Mass flow rate flowing through the return water butterfly valve, t / h;

[0069] K v ——Flow coefficient of backwater butterfly valve, m 3 / h;

[0070] Δp——pressure difference before and after the return water butterfly valve, MPa;

[0071] p1——pressure before valve, MPa;

[0072] p2 is the pressure after the valve, MPa;

[0073] ρ L ——Density of the liquid, kg / m 3 .

[0074] P L ——Pressure recovery coefficient, value is 0.9;

[0075]

[0076] Where:

[0077] F F ——critical pressure ratio coefficient of liquid;

[0078] p v ——Liquid saturated steam pressure at the inlet temperature of the return butterfly valve, pressure before the valve, MPa;

[0079] p c ———Liquid critical pressure, MPa; the critical pressure of water is 22.064 MPa.

[0080] The relative opening L of the return water butterfly valve provided by the manufacturer and the flow coefficient K v The characteristic curve is built into each return butterfly valve module, see Figure 2 ;

[0081] Since the circulating water pump, condenser, and return water butterfly valve are located at different altitudes, they directly affect the resistance characteristics of the circulating water pipeline. To simplify the calculation, the altitude difference between the circulating water pump suction port and the return water butterfly valve outlet is regarded as the elevation difference between the upstream and downstream interfaces of the circulating water pipeline.

[0082] Each return butterfly valve is set with different relative openings, according to the relative opening L of the return butterfly valve and the flow coefficient K v Characteristic curve, get the corresponding flow coefficient K v Assuming a certain total flow of a circulating water main pipe, the above characteristic equations are combined, and the pressures behind each return water butterfly valve are made equal to each other and equal to the converted value of atmospheric pressure after considering the elevation difference of the circulating water pipe, and the appropriate characteristic parameters such as the total flow of the circulating water main pipe and the circulating water main pipe pressure, the pressure before / after the return water butterfly valve, the water inlet flow of each condenser, and the motor power are solved iteratively. Figure 3-Figure 4The study presents the changing trends of the total circulating water main flow, the inlet flow of each condenser, and the total power consumption of the circulating water pump at different relative openings of the #1 return water butterfly valve. As the #1 return water butterfly valve opening decreases from 100% to 30%, the inlet flow of the #1 condenser gradually decreases, while the inlet flows of the #2 / #3 / #4 condensers gradually increase. Because the decrease in the inlet flow of the #1 condenser is greater than the increase in the inlet flows of the #2 / #3 / #4 condensers, the total flow of the circulating water main shows a downward trend. Both the total power consumption of the circulating water pump and the total flow of the circulating water main gradually decrease; however, the decrease in the total flow of the circulating water main is greater than the decrease in the total power consumption of the circulating water pump. This indicates that throttling the return water butterfly valve is an energy-inefficient adjustment method and should be carefully considered during operation.

[0083] The above detailed description of the condenser return water butterfly valve characteristic simulation calculation method provided by the present invention. This embodiment uses a specific example to illustrate the principles and implementation methods of the present invention. The above examples are intended only to facilitate understanding of the present invention's method and core concepts. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications fall within the scope of protection of the claims.

Claims

1. A condenser return water butterfly valve characteristics simulation calculation method, characterized in that: The method, based on a circulating water system diagram of a power station expansion unit, connects a circulating water pump module, a motor module, a condenser module, and a return water butterfly valve module in series and parallel to form a circulating water pipeline; based on a characteristic equation group of the circulating water pump, the condenser, and the return water butterfly valve, solves the circulating water main pipe pressure, the pressure before and after each return water butterfly valve, the total flow of the circulating water main pipe, the water inlet flow of each condenser, and the motor power under different relative openings of the return water butterfly valve to guide the operation of the power station circulating water system, wherein the method specifically includes the following steps: Step 1: According to the circulating water system diagram of the power station expansion unit, several circulating water pump modules, motor modules, condenser modules, and return water butterfly valve modules are connected in series and in parallel to form a circulating water pipeline. Among them, several circulating water pump modules are connected in parallel, and the outlets of each circulating water pump module are combined and connected in series to the inlet of the circulating water inlet main pipe; the outlet of the circulating water main pipe is divided and connected in series to the inlet of each condenser module; the outlet of each condenser module is connected in series to the inlet of the corresponding return water butterfly valve module; the outlets of all return water butterfly valve modules are combined and connected in series to the inlet of the circulating water return main pipe; Step 2: Establish the characteristic equation groups of the circulating water pump module, condenser module and return water butterfly valve module respectively: Step 2.1: Embed the manufacturer's flow-head / efficiency characteristic curve at rated speed into the circulating water pump module. Calculate the flow, head, efficiency, and motor power under constant or variable speed conditions based on the centrifugal pump proportionality law. Step 2.2: Calculate the water side resistance of the condenser module: ， ， ， Where: ——Total water resistance of cooling water passing through condenser, kPa; ——Frictional water resistance in the condenser tube, kPa; ——Water resistance at the end of the condenser tube, kPa; ——Condenser water chamber inlet water resistance, kPa; ——water resistance at the outlet of condenser water chamber, kPa; It is obtained based on the water velocity in the condenser tube and the characteristic curve equation provided by the HEI Standard Steam Surface Condensers of the American Heat Exchange Institute; Step 2.3: Calculate the flow rate and resistance of the return butterfly valve module: when When it is a non-blocking flow, the calculation formula is: ， when When it is a blocking flow, the calculation formula is: ， Where: ——Mass flow rate flowing through the return water butterfly valve, t / h; ——Flow coefficient of backwater butterfly valve, m 3 / h; ——The pressure difference before and after the return water butterfly valve, MPa; ——Pressure before valve, MPa; ——Valve outlet pressure, MPa; ——Density of the liquid, kg / m 3 ; ——Pressure recovery coefficient, value is 0.9; ， Where: ——critical pressure ratio coefficient of liquid; ——Liquid saturated steam pressure at the inlet temperature of the return butterfly valve, pressure before the valve, MPa; ---Liquid critical pressure, MPa; the critical pressure of water is 22.064 MPa; Step 3: Adjust the relative opening of the return water butterfly valve provided by the manufacturer and flow coefficient The characteristic curve is built into each return butterfly valve module; Step 4: Since the circulating water pump, condenser, and return water butterfly valve are located at different altitudes, which directly affect the resistance characteristics of the circulating water pipeline, to simplify the calculation, the altitude difference between the circulating water pump suction port and the return water butterfly valve outlet is regarded as the elevation difference between the upstream and downstream interfaces of the circulating water pipeline; Step 5: Set different relative openings for each return butterfly valve and obtain the corresponding flow coefficient according to step 3 Assuming a certain total flow rate of a circulating water main pipe, the characteristic equations listed in step 2 are combined, and the pressures behind each return water butterfly valve are made equal to each other and equal to the atmospheric pressure conversion value after considering the elevation difference of the circulating water pipe in step 4, and the appropriate total flow rate of the circulating water main pipe and the circulating water main pipe pressure, the pressure before / after each return water butterfly valve, the water inlet flow rate of each condenser, and the motor power are iteratively solved.

Images