CN109779898B - Method for setting necessary cavitation allowance of water supply pump of floating nuclear power station - Google Patents
Method for setting necessary cavitation allowance of water supply pump of floating nuclear power station Download PDFInfo
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Abstract
The invention discloses a method for setting the necessary cavitation allowance of a water supply pump of a floating nuclear power station, wherein the water supply pump is communicated with a deoxidizing water tank through a pipeline, the pipeline is formed by connecting a plurality of pipeline sections, two adjacent pipeline sections are not on the same straight line, the connecting part of the two adjacent pipeline sections and the connecting part of the pipeline sections with the water supply pump and the deoxidizing water tank are nodes, and the length, width and height directions of a ship body are respectively defined as X, Y, Z axes; the method comprises the following steps: measuring the relative coordinates of each node relative to the swing center of the ship body for multiple times; calculating the additional pressure drop experienced by the pipeline rotating around the X, Y, Z axis and translating along the X, Y, Z axis respectively at each measurement; calculating the sum of the friction pressure drop of the pipeline and the form resistance pressure drop of a local resistance part on the pipeline; calculating and obtaining the minimum value of the effective cavitation allowance at the water feed pump suction inlet; from the minimum value, a necessary cavitation margin at the suction inlet of the feed water pump is calculated. The method can calculate the necessary cavitation allowance meeting the operation requirement of the water feed pump.
Description
Technical Field
The invention relates to the technical field of a water supply system of a steam power plant, in particular to a method for setting the necessary cavitation allowance of a water supply pump of a floating nuclear power plant.
Background
The change of the motion state of the ship body under the ocean condition can affect the flow characteristic of fluid in the power system, and further affect the operation characteristic of the power system. The main water feed pump group is used as key equipment of a secondary loop system of the floating nuclear power station, whether cavitation of the main water feed pump can be effectively prevented is the key for prolonging the service life of the main water feed pump group. Under the influence of ocean conditions, the water supply system of the floating nuclear power plant can generate additional acceleration and additional force, the effective height of the additional force is changed, the inlet pressure of the water supply pump is possibly lower than the saturation pressure at the corresponding temperature, cavitation is generated, and the thermal hydraulic characteristics and the normal working state of the whole nuclear power plant are further influenced.
At present, when domestic and foreign scholars analyze ocean conditions, the simple equivalence of the ocean conditions is mostly simple harmonic oscillation motion, and the flow characteristics of fluid under the actual ocean conditions are extremely complex: the ship body can make 6-degree-of-freedom oscillation and shaking around the initial balance position, the three directions of translation are X, Y, Z and the three directions of rotation are X, Y, Z, and the translation acceleration, the rotation angle and the period are changed continuously along with the change of the parameters of the stormy waves and the flow. Because the marine environment is not accurately simulated, the problems of overlarge swing angle value and undersize period value mostly exist in practical engineering application, the effective cavitation allowance of the water feeding pump is greatly reduced, the necessary cavitation allowance of the water feeding pump provided by a manufacturer cannot meet the requirement, the effective cavitation allowance of the water feeding pump can be improved only by increasing the height difference between the deoxygenation water tank and the water feeding pump, and the difficulty is increased for the problem of ship body space arrangement.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for setting the necessary cavitation allowance of a water supply pump of a floating nuclear power station, which can calculate the necessary cavitation allowance meeting the operation requirement of the water supply pump.
In order to achieve the above purposes, the technical scheme adopted by the invention is as follows: a method for setting the necessary cavitation allowance of a water supply pump of a floating nuclear power station is characterized in that the water supply pump is communicated with a deoxidizing water tank through a pipeline, the pipeline is formed by sequentially connecting a plurality of pipeline sections, two adjacent pipeline sections are not on the same straight line, the joint of the two adjacent pipeline sections and the joint of the pipeline sections with the water supply pump and the deoxidizing water tank are nodes, and the length, width and height directions of a ship body are defined as X, Y, Z axes respectively;
the method comprises the following steps:
under the condition of simulating the marine environment, measuring the relative coordinates of each node relative to the ship body swing center for multiple times;
calculating the additional pressure drop experienced by the line rotating about the X, Y, Z axis for each measurement;
calculating the additional pressure drop experienced by the pipeline in translation along the X, Y, Z axis respectively at each measurement;
calculating the sum of the friction pressure drop of the pipeline and the form resistance pressure drop of all local resistance pieces on the pipeline;
calculating and obtaining the minimum value of the effective cavitation allowance at the water feed pump suction inlet;
based on the minimum value, a necessary cavitation margin at the suction inlet of the feed water pump is calculated.
Further, the total number of the nodes is recorded as n, and the nodes are numbered from the deoxygenation water tank to the water feeding pump;
the method for measuring the relative coordinates of each node relative to the swing center of the ship body specifically comprises the following steps:
obtaining coordinates (x) of each node1t,y1t,z1t)、(x2t,y2t,z2t)、…、(xnt,ynt,znt) And hull roll center coordinates (x)ct,yct,zct)；
The relative coordinate of each node relative to the swing center of the ship body is (x)1t-xct,y1t-yct,z1t-zct)、(x2t-xct,y2t-yct,z2t-zct)、…、(xnt-xct,ynt-yct,znt-zct) And t is the serial number of the measurement times.
Further, the air conditioner is provided with a fan,
calculating the additional pressure drop P to which said line is subjected in rotation about the x-axis according to equation (1)rxt：
Calculating the additional pressure drop P to which said line is subjected in rotation about the y-axis according to equation (2)ryt：
Calculating the additional pressure drop P experienced by the pipeline rotating around the z-axis according to equation (3)rzt：
Wherein, b is a node serial number; prxt、PrytAnd PrztThe unit of (A) is Pa; omegaxt、ωyt、ωztRespectively the swing angular velocity of the pipeline rotating around the X, Y, Z shaft at the t-th measurement with the unit of rad/s, βxt、βyt、βztRespectively, the swing angular acceleration of the pipeline rotating around an X, Y, Z shaft during the t-th measurement, and the unit is rad/s2(ii) a Rho is the density of water in the pipeline, kg/m3。
Further, the air conditioner is provided with a fan,
calculating the additional pressure drop P suffered by the pipeline in the translation along the x-axis according to the formula (4)mxt：
Pmxt＝axtρ·(xnt-x1t) (4)；
Calculating the additional pressure drop P suffered by the pipeline along the y-axis translation according to the formula (5)myt：
Pmyt＝aytρ·(ynt-y1t) (5)；
Calculating the additional pressure drop P experienced by the pipeline in translation along the z-axis according to equation (6)mzt：
Pmzt＝aztρ·(znt-z1t) (6)；
Wherein, Pmxt、PmytAnd PmztThe unit of (A) is Pa; a isxt、ayt、aztThe t-th measurement is the translational acceleration of the pipeline along the X, Y, Z shaft translation, and the unit is m/s2。
Further, the frictional pressure drop Δ p of the piping is calculated according to the equations (7) to (10)f：
N is the total number of nodes, the nodes are numbered in the direction from the deoxygenation water tank to the water feeding pump, and the numbering direction of the pipeline sections is the same as that of the nodes; Δ pf,iIs the friction pressure drop, Pa, of the ith pipeline segment; lambda [ alpha ]iThe on-way resistance loss coefficient of the ith pipeline section is dimensionless; l isiIs the length of the ith pipeline segment, m; rho is the density of water in the pipeline, kg/m3；diIs the inner diameter, m, of the ith tube segment; g is the water supply mass flow of the water supply pump, kg/s; reiThe Reynolds number of the ith pipeline section, and η the dynamic viscosity of water, kg/(m · s).
Further, the total number of all local resistance pieces on the pipeline is recorded as k, and all the local resistance pieces are numbered from the deoxygenation water tank to the water feeding pump;
calculating the sum delta p of the form resistance pressure drop of all the local resistance parts on the pipeline according to the formulas (11) to (12)ζ：
Wherein, Δ Pζ,jIs the shape resistance pressure drop, Pa, of the jth local resistance piece; zetajThe form drag coefficient of the jth local drag piece is dimensionless; djThe inner diameter m of the pipeline section where the jth local resistance piece is located; rho is the density of water in the pipeline, kg/m3(ii) a G is the feed water mass flow of the feed water pump, kg/s.
Further, the step of calculating and obtaining the minimum value of the effective cavitation allowance at the water feed pumping inlet comprises the following steps:
calculate each measurement according to equation (13)Effective cavitation allowance NPSH at water supply pump suction inleta：
Wherein HgM is the height difference between the deoxygenation water tank and the water feeding pump; prxt、PrytAnd PrztThe additional pressure drop experienced by the pipeline rotating around X, Y, Z axes respectively is Pa; pmxt、PmytAnd PmztThe additional pressure drop of the pipeline respectively translated along X, Y, Z axes is Pa; Δ pfIs the friction pressure drop, Pa, of the pipeline; Δ pζThe sum of the form resistance pressure drop of all local resistance parts on the pipeline is Pa; p0Is atmospheric pressure, Pa; rho is the density of water in the pipeline, kg/m3；
Selecting the minimum value NPSH with the smallest value as the effective cavitation allowance from all the obtained effective cavitation allowancesa,min。
Further, the step of calculating and obtaining the minimum value of the effective cavitation allowance at the water feed pumping inlet comprises the following steps:
calculating (P) at each measurementrxt+Pryt+Przt+Pmxt+Pmyt+Pmzt) And selecting the minimum MIN (P) therefromrxt+Pryt+Przt+Pmxt+Pmyt+Pmzt)；
Then, the minimum value NPSH of the effective cavitation margin is calculated according to the formula (14)a,min：
Wherein HgM is the height difference between the deoxygenation water tank and the water feeding pump; prxt、PrytAnd PrztThe additional pressure drop experienced by the pipeline rotating around X, Y, Z axes respectively is Pa; pmxt、PmytAnd PmztThe pipelines are respectively arranged along X,Y, Z the additional pressure drop suffered by the axial translation is Pa; Δ pfIs the friction pressure drop, Pa, of the pipeline; Δ pζThe sum of the form resistance pressure drop of all local resistance parts on the pipeline is Pa; p0Is atmospheric pressure, Pa; rho is the density of water in the pipeline, kg/m3。
Further, a necessary cavitation margin NPSH at a suction port of the feed water pump is calculated according to the formula (15)r：
Wherein, NPSHa,minIs the minimum value of the effective cavitation allowance at the water feed pump suction inlet; a is a tolerance coefficient of the water supply pump and is dimensionless.
Compared with the prior art, the invention has the advantages that:
(1) the method for setting the necessary cavitation allowance of the water supply pump of the floating nuclear power station is simple and easy to use, and can calculate the necessary cavitation allowance meeting the operation requirement of the water supply pump of the nuclear power station under the ocean condition.
(2) The invention can avoid increasing the effective cavitation allowance of the water feeding pump by increasing the height difference between the deoxygenation water tank and the water feeding pump, and reduce the difficulty of the space arrangement of the ship body; in addition, in the case that the feed-water pump requires cavitation margin determination, the method can also verify whether the spatial arrangement of the feed-water pump meets the environmental condition requirements.
Drawings
Fig. 1 is a layout diagram of a pipeline between an oxygen-removing water tank and a feed water pump according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Referring to fig. 1, the embodiment of the invention provides a method for setting the necessary cavitation allowance of a water supply pump of a floating nuclear power station, the method is simple and easy to use, and the necessary cavitation allowance meeting the operation requirement of the water supply pump of the nuclear power station under the ocean condition can be calculated.
The method can calculate the additional pressure drop borne by the pipeline in translation and rotation in three directions, and can numerically judge the stress of the pipeline in the three directions, so that the effective cavitation allowance can be adjusted by adjusting the distance between the node and the ship body swing center in the three directions, and if the stress in the X direction is larger, the distance between the node and the ship body swing center in the X direction can be reduced, therefore, the method can avoid increasing the effective cavitation allowance of the water feeding pump by increasing the height difference between the deoxygenation water tank and the water feeding pump, and reduce the difficulty of the space arrangement of the ship body; in addition, in the case that the feed-water pump requires cavitation margin determination, the method can also verify whether the spatial arrangement of the feed-water pump meets the environmental condition requirements.
The water-feeding pump of the floating nuclear power station is communicated with the deoxidizing water tank through a pipeline, the pipeline is formed by sequentially connecting a plurality of pipeline sections, two adjacent pipeline sections are not on the same straight line, the joint of the two adjacent pipeline sections, the joint of the pipeline section and the water-feeding pump and the joint of the pipeline section and the deoxidizing water tank are called as nodes, and the length, width and height directions of the ship body are respectively defined as X, Y, Z axes;
the setting method comprises the following steps:
s1: under the condition of simulating the marine environment, measuring the relative coordinates of each node relative to the ship body swing center for multiple times; the center of hull roll is the intersection of the roll, pitch and yaw axes of the hull. Under the action of random wind waves, the motion of the ship body is random, so that the swinging center of the ship body is also not fixed. In actual calculation, the center of gravity of the ship body is approximated to the center of rolling of the ship body.
The method specifically comprises the following steps:
s10: counting the total number of the nodes as n, and numbering the nodes from the deoxygenation water tank to the water feeding pump; referring to fig. 1, in the present embodiment, a node n is 7, the total number of the pipeline segments is 6, and 7 nodes are respectively numbered A, B, C, D, E, F, G in the direction from the oxygen removal water tank to the feed water pump;
s11: the marine environment condition is simulated, and the embodiment selects the marine environment condition which simulates one hundred years, and under the marine environment condition, each node and the ship body are measured and obtained for multiple times in the test timeThe coordinate of each node obtained in the t-th measurement is recorded as (x)1t,y1t,z1t)、(x2t,y2t,z2t)、…、(xnt,ynt,znt) And the coordinate of the swinging center of the ship body is (x)ct,yct,zct)；
S12: respectively calculating coordinate difference between each node and the ship body swing center obtained in each measurement, namely the relative coordinate of the node relative to the ship body swing center, wherein the relative coordinate of each node relative to the ship body swing center in the tth measurement is (x)1t-xct,yt1-yct,zt1-zct)、(x2t-xct,y2t-yct,z2t-zct)、…、(xnt-xct,ynt-yct,znt-zct) And t is the serial number of the measurement times.
S2: calculating the additional pressure drop experienced by the pipeline rotating around the X, Y, Z shaft respectively at each measurement;
the method specifically comprises the following steps:
s20: calculating the additional pressure drop P suffered by the pipeline rotating around the X axis in the t measurement according to the formula (1)rxt：
S21: calculating the additional pressure drop P suffered by the pipeline rotating around the y axis in the t measurement according to the formula (2)ryt：
S22: calculating the additional pressure drop P suffered by the pipeline rotating around the z axis in the t measurement according to the formula (3)rzt：
Wherein the content of the first and second substances,b is a node serial number; prxt、PrytAnd PrztThe unit of (A) is Pa; omegaxt、ωyt、ωztRespectively the swing angular velocity of the pipeline rotating around the X, Y, Z shaft at the t-th measurement, the unit is rad/s, βxt、βyt、βztRespectively, the swing angular acceleration of the pipeline rotating around the X, Y, Z shaft at the t-th measurement, the unit is rad/s2(ii) a Rho is the density of water in the pipeline, kg/m3。
S3: calculating the additional pressure drop of the pipeline respectively translated along the X, Y, Z axis in each measurement;
the method specifically comprises the following steps:
s30: calculating the additional pressure drop P suffered by the pipeline in translation along the x axis in the t measurement according to the formula (4)mxt：
Pmxt＝axtρ·(xnt-x1t) (4)；
S31: calculating the additional pressure drop P of the pipeline in translation along the y axis in the t measurement according to the formula (5)myt：
Pmyt＝aytρ·(ynt-y1t) (5)；
S32: calculating the additional pressure drop P of the pipeline in translation along the z axis in the t measurement according to the formula (6)mzt：
Pmzt＝aztρ·(znt-z1t) (6)；
Wherein, Pmxt、PmytAnd PmztThe unit of (A) is Pa; a isxt、ayt、aztRespectively, the translational acceleration of the pipeline along the X, Y, Z shaft translation during the t-th measurement is in m/s2。
S4: calculating the sum of the friction pressure drop of the pipeline and the form resistance pressure drop of all local resistance pieces on the pipeline;
the method specifically comprises the following steps:
s40: calculating the friction of the pipeline according to the formulas (7) to (10)Wiping pressure drop Δ pf：
N is the total number of nodes, the nodes are numbered in the direction from the deoxygenation water tank to the water feeding pump, and the numbering direction of the pipeline sections is the same as that of the nodes; Δ pf,iIs the friction pressure drop, Pa, of the ith pipeline segment; lambda [ alpha ]iThe on-way resistance loss coefficient of the ith pipeline section is dimensionless; l isiIs the length of the ith pipeline segment, m; rho is the density of water in the pipeline, kg/m3；diIs the inner diameter, m, of the ith tube segment; g is the water supply mass flow of the water supply pump, kg/s; reiThe Reynolds number of the ith pipeline section, and η the dynamic viscosity of water, kg/(m · s).
S41: the accessories such as valves, pore plates and the like on the pipeline which can generate resistance to water flow in the pipeline are collectively called local resistance pieces, the total number of all the local resistance pieces on the pipeline is recorded as k, and all the local resistance pieces are numbered from the deoxygenation water tank to the water supply pump;
calculating the sum delta p of the form resistance pressure drop of all local resistance parts on the pipeline according to the formulas (11) to (12)ζ：
Wherein, Δ Pζ,jIs the shape resistance pressure drop, Pa, of the jth local resistance piece; zetajThe form drag coefficient of the jth local drag piece is dimensionless; djThe inner diameter m of the pipeline section where the jth local resistance piece is located; rho is the density of water in the pipeline, kg/m3(ii) a G is the water supply mass flow of the water supply pump, kg/s; .
S5: calculating and obtaining the minimum value of the effective cavitation allowance at the water feed pump suction inlet;
specifically, two ways are included:
the first method is as follows: calculating the effective cavitation allowance at each measurement, and then selecting the minimum value from all the effective cavitation allowances as the minimum value of the effective cavitation allowances, namely:
the effective cavitation margin NPSH at the suction inlet of the feed water pump at each measurement is calculated according to equation (13)a：
Wherein HgM is the height difference between the deoxygenation water tank and the water feeding pump; prxt、PrytAnd PrztThe additional pressure drop suffered by the pipeline rotating around X, Y, Z axes respectively is Pa; pmxt、PmytAnd PmztThe additional pressure drop is respectively applied to the pipelines along the X, Y, Z axis translation, and the unit is Pa; Δ pfIs the friction pressure drop, Pa, of the pipeline; Δ pζThe sum of the form resistance pressure drop of all local resistance parts on the pipeline is Pa; p0Is atmospheric pressure, Pa; rho is the density of water in the pipeline, kg/m3；
Selecting the minimum value NPSH with the smallest value as the effective cavitation allowance from all the obtained effective cavitation allowancesa,min。
The second method comprises the following steps: calculating (P) at each measurementrxt+Pryt+Przt+Pmxt+Pmyt+Pmzt) Selecting the minimum MIN (P)rxt+Pryt+Przt+Pmxt+Pmyt+Pmzt) Then, againCalculating according to the formula (14):
s6: from the minimum value, a necessary cavitation margin at the suction inlet of the feed water pump is calculated.
Specifically, the necessary cavitation margin NPSH at the suction inlet of the feed water pump is calculated according to the formula (15)r：
Wherein, NPSHa,minThe minimum value of the effective cavitation allowance at the water feed pump suction inlet is m; a is a tolerance coefficient of the water supply pump, is dimensionless, can be determined according to actual needs, and for 2-level test precision, A is 6%; for the test accuracy of level 1, a is 3%.
In summary, the traditional analysis methods for ocean conditions simplify the ocean conditions into independent fluctuation and swing, and analyze and study the influences generated by the fluctuation and swing respectively, namely, the influence is only considered from one coordinate direction, and comprehensive stress is neglected; the sway approximation is equivalent to simple harmonic motion, and the influence of actual ocean conditions is difficult to comprehensively consider. The flow characteristics of the fluid under the actual ocean conditions are extremely complex, and the fluid has translation in three directions and rotation in three directions. For the water feed pump operating characteristic under the real simulation marine environment condition, the additional force of 6 degrees of freedom that this patent received to water feed pump inlet pipeline fluid has carried out the deduction, can provide computational model support for floating nuclear power station water feed pump operating stability analysis under the marine condition.
The present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements are also considered to be within the scope of the present invention. Those not described in detail in this specification are within the skill of the art.
Claims (9)
1. A method for setting the necessary cavitation allowance of a water supply pump of a floating nuclear power station is characterized in that the water supply pump is communicated with a deoxidizing water tank through a pipeline, the pipeline is formed by sequentially connecting a plurality of pipeline sections, two adjacent pipeline sections are not on the same straight line, the connecting positions of the two adjacent pipeline sections and the connecting positions of the pipeline sections with the water supply pump and the deoxidizing water tank are nodes, and the length, width and height directions of a ship body are defined as X, Y, Z axes respectively;
the method comprises the following steps:
under the condition of simulating the marine environment, measuring the relative coordinates of each node relative to the ship body swing center for multiple times;
calculating the additional pressure drop experienced by the line rotating about the X, Y, Z axis for each measurement;
calculating the additional pressure drop experienced by the pipeline in translation along the X, Y, Z axis respectively at each measurement;
calculating the sum of the friction pressure drop of the pipeline and the form resistance pressure drop of all local resistance pieces on the pipeline;
calculating and obtaining the minimum value of the effective cavitation allowance at the water feed pump suction inlet;
based on the minimum value, a necessary cavitation margin at the suction inlet of the feed water pump is calculated.
2. The method for setting the necessary cavitation allowance of the water-feeding pump of the floating nuclear power station as claimed in claim 1, wherein the total number of nodes is recorded as n, and the nodes are numbered from the deoxygenation water tank to the direction of the water-feeding pump;
the method for measuring the relative coordinates of each node relative to the swing center of the ship body specifically comprises the following steps:
obtaining coordinates (x) of each node1t,y1t,z1t)、(x2t,y2t,z2t)、…、(xnt,ynt,znt) And hull roll center coordinates (x)ct,yct,zct)；
The relative coordinate of each node relative to the swing center of the ship body is (x)1t-xct,y1t-yct,z1t-zct)、(x2t-xct,y2t-yct,z2t-zct)、…、(xnt-xct,ynt-yct,znt-zct) And t is the serial number of the measurement times.
3. The method for setting the necessary cavitation margin of the floating nuclear power plant feed pump according to claim 2,
calculating the additional pressure drop P to which said line is subjected in rotation about the x-axis according to equation (1)rxt：
Calculating the additional pressure drop P to which said line is subjected in rotation about the y-axis according to equation (2)ryt：
Calculating the additional pressure drop P experienced by the pipeline rotating around the z-axis according to equation (3)rzt：
Wherein, b is a node serial number; prxt、PrytAnd PrztThe unit of (A) is Pa; omegaxt、ωyt、ωztRespectively the swing angular velocity of the pipeline rotating around the X, Y, Z shaft at the t-th measurement with the unit of rad/s, βxt、βyt、βztRespectively, the swing angular acceleration of the pipeline rotating around an X, Y, Z shaft during the t-th measurement, and the unit is rad/s2(ii) a Rho is the density of water in the pipeline, kg/m3。
4. The method for setting the necessary cavitation allowance of the floating nuclear power plant feed pump according to claim 2, characterized in that:
calculating the additional pressure drop P suffered by the pipeline in the translation along the x-axis according to the formula (4)mxt：
Pmxt＝axtρ·(xnt-x1t) (4)；
Calculating the additional pressure drop P suffered by the pipeline along the y-axis translation according to the formula (5)myt：
Pmyt＝aytρ·(ynt-y1t) (5)；
Calculating the additional pressure drop P experienced by the pipeline in translation along the z-axis according to equation (6)mzt：
Pmzt＝aztρ·(znt-z1t) (6)；
Wherein, Pmxt、PmytAnd PmztThe unit of (A) is Pa; a isxt、ayt、aztThe t-th measurement is the translational acceleration of the pipeline along the X, Y, Z shaft translation, and the unit is m/s2。
5. The method for setting the necessary cavitation margin of the floating nuclear power plant feed pump according to claim 1, wherein the friction pressure drop Δ p of the pipeline is calculated according to equations (7) to (10)f：
N is the total number of nodes, the nodes are numbered in the direction from the deoxygenation water tank to the water feeding pump, and the numbering direction of the pipeline sections is the same as that of the nodes; Δ pf,iIs the friction pressure drop, Pa, of the ith pipeline segment; lambda [ alpha ]iThe on-way resistance loss coefficient of the ith pipeline section is dimensionless; l isiIs the length of the ith pipeline segment, m; rho is the density of water in the pipeline, kg/m3；diIs the inner diameter, m, of the ith tube segment; g is the water supply mass flow of the water supply pump, kg/s; reiThe Reynolds number of the ith pipeline section, and η the dynamic viscosity of water, kg/(m · s).
6. The method for setting the necessary cavitation allowance of the water supply pump of the floating nuclear power station as claimed in claim 1, wherein the total number of all local resistance pieces on the pipeline is recorded as k, and all the local resistance pieces are numbered from the oxygen removal water tank to the direction of the water supply pump;
calculating the sum delta p of the form resistance pressure drop of all the local resistance parts on the pipeline according to the formulas (11) to (12)ζ：
Wherein, Δ Pζ,jIs the shape resistance pressure drop, Pa, of the jth local resistance piece; zetajThe form drag coefficient of the jth local drag piece is dimensionless; djThe inner diameter m of the pipeline section where the jth local resistance piece is located; rho is the density of water in the pipeline, kg/m3(ii) a G is the feed water mass flow of the feed water pump, kg/s.
7. The method for setting the necessary cavitation margin of the feedwater pump of the floating nuclear power plant as claimed in claim 1, wherein calculating and obtaining the minimum value of the effective cavitation margin at the pumping inlet of the feedwater pump comprises the steps of:
calculating the effective cavitation allowance NPSH at the water supply pump suction inlet in each measurement according to the formula (13)a：
Wherein HgM is the height difference between the deoxygenation water tank and the water feeding pump; prxt、PrytAnd PrztThe additional pressure drop experienced by the pipeline rotating around X, Y, Z axes respectively is Pa; pmxt、PmytAnd PmztThe additional pressure drop of the pipeline respectively translated along X, Y, Z axes is Pa; Δ pfIs the friction pressure drop, Pa, of the pipeline; Δ pζThe sum of the form resistance pressure drop of all local resistance parts on the pipeline is Pa; p0Is atmospheric pressure, Pa; rho is the density of water in the pipeline, kg/m3；
Selecting the minimum value NPSH with the smallest value as the effective cavitation allowance from all the obtained effective cavitation allowancesa,min。
8. The method for setting the necessary cavitation margin of the feedwater pump of the floating nuclear power plant as claimed in claim 1, wherein calculating and obtaining the minimum value of the effective cavitation margin at the pumping inlet of the feedwater pump comprises the steps of:
calculating (P) at each measurementrxt+Pryt+Przt+Pmxt+Pmyt+Pmzt) And selecting the minimum MIN (P) therefromrxt+Pryt+Przt+Pmxt+Pmyt+Pmzt)；
Then, the minimum value NPSH of the effective cavitation margin is calculated according to the formula (14)a,min：
Wherein HgM is the height difference between the deoxygenation water tank and the water feeding pump; prxt、PrytAnd PrztThe additional pressure drop experienced by the pipeline rotating around X, Y, Z axes respectively is Pa; pmxt、PmytAnd PmztThe additional pressure drop of the pipeline respectively translated along X, Y, Z axes is Pa; Δ pfIs the friction pressure drop, Pa, of the pipeline; Δ pζThe sum of the form resistance pressure drop of all local resistance parts on the pipeline is Pa; p0Is atmospheric pressure, Pa; rho is the density of water in the pipeline, kg/m3。
9. The method for setting the required cavitation margin of the feedwater pump of the floating nuclear power plant as claimed in claim 1, wherein the required cavitation margin NPSH at the suction inlet of the feedwater pump is calculated according to the formula (15)r：
Wherein, NPSHa,minIs the minimum value of the effective cavitation allowance at the water feed pump suction inlet; a is a tolerance coefficient of the water supply pump and is dimensionless.
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| CN104633458B (en) * | 2015-02-14 | 2017-08-29 | 西安热工研究院有限公司 | A kind of thermal power station's water pump real-time online Cavitation detection early warning system and method |
| CN105224810A (en) * | 2015-10-15 | 2016-01-06 | 中国大唐集团科学技术研究院有限公司华东分公司 | A kind of method of quick judgement pump cavitation |
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