CN113297809A - Simulation estimation method for gap leakage amount of impeller opening ring of centrifugal pump - Google Patents
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Abstract
The invention provides a simulation estimation method of the leakage amount of an impeller opening ring gap of a centrifugal pump, which comprises the steps of drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, separating and marking a contact surface, calculating and obtaining the pressure distribution on the contact surface of a part in contact with the impeller opening ring gap, calculating and obtaining the simulated value of the leakage flow of the impeller opening ring gap and the average pressure difference between an inlet surface and an outlet surface, calculating the resistance coefficient of the impeller opening ring gap, calculating the estimated value of the leakage flow of the impeller opening ring gap and the like.
Description
Technical Field
The invention relates to the field of centrifugal pumps, in particular to a simulation estimation method for the gap leakage amount of an impeller opening ring of a centrifugal pump.
Background
The centrifugal pump is widely applied to various fields of national economy and resident life, a large amount of energy is consumed in the operation process, so that energy conservation and consumption reduction are one of the most important subjects in the technical field of the centrifugal pump, and the design of a high-efficiency hydraulic model is one of the most key ways for improving the efficiency of the centrifugal pump. Currently, a computational fluid dynamics simulation method is commonly used to assist the optimization design of a centrifugal pump hydraulic model. The operation efficiency of the centrifugal pump is the product of hydraulic efficiency, volumetric efficiency and mechanical efficiency, wherein the hydraulic efficiency can be accurately predicted through computational fluid mechanics simulation analysis of a full fluid area in the centrifugal pump; the mechanical efficiency mainly depends on the transmission efficiency between a main shaft of the centrifugal pump and a motor and the mechanical friction loss between each part of the centrifugal pump, and the relation between the value of the mechanical efficiency and a hydraulic model of the centrifugal pump is very small; volumetric efficiency is closely related to the magnitude of leakage flow between the centrifugal pump impeller and the orifice ring.
In the design stage of the centrifugal pump, according to a hydraulic model design scheme, the leakage flow between the centrifugal pump impeller and the opening ring under different flow working conditions is predicted, and then a corresponding volumetric efficiency value is obtained, so that the method is of great importance for the efficiency optimization of the centrifugal pump. In the currently known technical solutions, the leakage flow rate of the gap between the centrifugal pump impeller and the mouth ring (impeller mouth ring gap) is predicted mainly by an empirical formula or a computational fluid dynamics simulation mode. However, the prediction accuracy of the empirical formula is limited, and the design of the centrifugal pump and the structural style of the orifice ring parts does not necessarily conform to the applicable range of the empirical formula. The computational fluid mechanics simulation mode needs to draw a three-dimensional assembly body including a water body suction chamber, a pumping chamber, an impeller area and an impeller opening ring gap in the centrifugal pump, divide grids and perform numerical calculation. Because the impeller opening ring gap is small in size, the small grid size needs to be set in the part of the area during grid division; in order to ensure the numerical calculation accuracy by smooth transition and overall coordination of grids, the sizes of other main flow areas near the impeller opening ring gap need to be set to be smaller, so that the grid division difficulty is brought, the number of grids in the whole calculation area is huge, the calculation amount is obviously increased, and the requirement of quick optimization design of a centrifugal pump hydraulic model is not met.
Therefore, how to estimate the leakage amount of the centrifugal pump impeller opening ring clearance relatively quickly on the premise of ensuring certain calculation accuracy is a technical problem to be solved urgently.
Disclosure of Invention
In order to solve the technical problems, the invention provides a simulation estimation method of the centrifugal pump impeller opening ring gap leakage amount, which is scientific and reasonable, small in calculated amount, high in accuracy and convenient to apply.
The technical scheme for solving the problems is as follows:
a simulation estimation method for the gap leakage of the impeller opening ring of a centrifugal pump is used for estimating the leakage flow of the gap between the impeller and the opening ring of the centrifugal pump under specific delivery flow by combining computer simulation analysis, and comprises the following steps:
step (1), drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, and separating and marking contact surfaces of parts in contact with the impeller opening ring gap:
drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, including a water suction chamber, a water pumping chamber, an impeller area and an impeller opening ring gap, and separating and marking contact surfaces between parts and the impeller opening ring gap aiming at the parts in contact with the impeller opening ring gap;
and (2) under the condition of neglecting the impeller opening ring gap, calculating and obtaining the pressure distribution on the contact surface of the part in contact with the impeller opening ring gap by using computational fluid dynamics software:
removing parts of the impeller opening ring gap, dividing grids, performing simulation calculation of a full-flow area in the centrifugal pump by using a computational fluid dynamics software tool, and obtaining a pressure distribution data matrix on a contact surface of the parts which are in contact with the impeller opening ring gap under a specific delivery flow rate according to the three-dimensional assembly drawing drawn in the step (1);
and (3) aiming at a certain impeller opening ring gap with leakage quantity needing to be estimated, selecting the corresponding pressure distribution data matrix obtained in the step (2) as the inlet and outlet boundary condition information, and calculating by using computational fluid dynamics software to obtain a leakage flow simulation value Q of the pressure distribution data matrixnAnd the average pressure difference Δ P between the inlet and outlet faces:
determining a certain impeller opening ring gap needing leakage estimation, extracting a corresponding part three-dimensional graph from the assembly obtained in the step (1), dividing a grid, and extracting a part contacting with the impeller opening ring gap from the data matrix obtained in the step (2)The pressure distribution data matrix on the contact surface is used as the inlet and outlet boundary condition information of the impeller opening ring gap, and the leakage flow simulation value Q is obtained by using computational fluid dynamics software to calculatenAnd subtracting the average pressure value of the inlet surface from the average pressure value of the outlet surface to obtain an average pressure difference value delta P between the inlet surface and the outlet surface;
step (4), aiming at the leakage flow simulation value Q of a certain impeller opening ring gap with the leakage amount needing to be estimated, obtained in the step (3)nAnd the average pressure difference delta P between the inlet and outlet surfaces, and calculating the resistance coefficient zeta of the impeller opening ring gapn：
In the formula (1), g is the gravity acceleration and the unit is m/s2(ii) a Delta P is the average pressure difference between the inlet and outlet surfaces of the impeller opening ring gap expressed by the height of a water column, and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2；QnIs a simulated value of the leakage flow of the impeller opening ring gap, and the unit is m3/s；
Step (5), aiming at the average pressure difference value delta P between the inlet and outlet surfaces of the certain impeller opening ring clearance with the leakage quantity needing to be estimated, obtained in step (3), and the resistance coefficient zeta of the impeller opening ring clearance, obtained in step (4)nAnd calculating the leakage flow estimated value Q of the impeller opening ring gap:
in the formula (2), ζ1For suddenly decreasing local resistance coefficient value, zeta, between impeller opening ring gap and fluid area near its inlet1The value is between 0.8 and 1.2; zeta2Is the sudden expansion of the local resistance coefficient value, zeta, between the impeller eye gap and the fluid field in the vicinity of its outlet2The value is between 0.2 and 0.5; zetanCalculating the resistance coefficient of the impeller opening ring gap obtained in the step (4);g is the acceleration of gravity in m/s2(ii) a Delta P is the average pressure difference value between the inlet and outlet surfaces of the impeller opening ring gap expressed by the height of the water column obtained in the step (3), and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2。
The simulation estimation method for the centrifugal pump impeller opening ring clearance leakage amount specifically comprises the following substeps in the step (2):
substep (2.1), removing impeller opening ring gap parts aiming at the three-dimensional assembly drawing drawn in the step (1), and then reassembling to obtain a three-dimensional assembly drawing of the water body in the centrifugal pump, including a water suction chamber, a water pumping chamber and an impeller region;
substep (2.2), aiming at the three-dimensional assembly drawing of the water body in the centrifugal pump obtained in substep (2.1), dividing grids, setting boundary conditions, and performing simulation calculation of the full flow area in the centrifugal pump under specific delivery flow by using a computational fluid dynamics software tool;
and (2.3) sequentially extracting pressure distribution data on a contact surface in contact with the impeller opening ring gap to form a plurality of data matrixes, wherein each contact surface in contact with the impeller opening ring gap corresponds to one pressure distribution data matrix.
The simulation estimation method for the centrifugal pump impeller opening ring clearance leakage amount specifically comprises the following substeps in the step (3):
substep (3.1) determining a certain impeller opening ring gap of which the leakage amount needs to be estimated, and extracting a part three-dimensional diagram corresponding to the impeller opening ring gap from the assembly obtained in the step (1);
substep (3.2) of meshing the three-dimensional drawing of the part obtained in substep (3.1);
substep (3.3) of comparing pressure distribution data matrixes on two contact surfaces in contact with the impeller opening ring gap from the data matrix obtained in step (2) aiming at the impeller opening ring gap determined in substep (3.1), taking the contact surface corresponding to the data matrix with a higher average pressure value as a first contact surface, and taking the contact surface corresponding to the data matrix with a lower average pressure value as a second contact surface;
substep (3.4) regarding the impeller opening ring gap determined in substep (3.1), taking a surface of the opening ring gap, which is in contact with the first contact surface, as an inlet surface, taking a surface of the opening ring gap, which is in contact with the second contact surface, as an outlet surface, setting the inlet surface and the outlet surface as boundary conditions of a pressure inlet and a pressure outlet respectively, and adding pressure distribution data matrixes corresponding to the first contact surface and the second contact surface as information of the boundary conditions of the pressure inlet and the pressure outlet respectively;
substep (3.5) obtaining simulated impeller-mouth-ring-gap-leakage-flow value Q by calculation of computational fluid dynamics softwarenAnd the average pressure difference Δ P between the inlet and outlet faces is obtained by subtracting the average pressure value at the inlet face from the average pressure value at the outlet face.
In the simulation estimation method for the leakage amount of the impeller opening ring gap of the centrifugal pump, in the setting of the boundary condition in the substep (2.2), the contact surface in contact with the impeller opening ring gap is set as a wall surface condition.
In the simulation estimation method for the leakage amount of the impeller opening ring gap of the centrifugal pump, the three-dimensional drawing of the part corresponding to the impeller opening ring gap is extracted in the substep (3.1), and the position three-dimensional coordinate information of the part is consistent with the position three-dimensional coordinate information of the original assembly body of the part in the step (1).
The invention has the beneficial effects that:
1. aiming at the defects of complex meshing and large calculation amount of the current method of directly using a computational fluid dynamics tool to predict the leakage amount of the impeller opening ring gap of the centrifugal pump, the invention estimates the leakage amount of the impeller opening ring gap of the centrifugal pump through two main stages: in the first stage, the existence of the impeller opening ring gap of the centrifugal pump is ignored, the full flow field of the water body in the centrifugal pump under a specific flow rate is calculated, and the pressure distribution information on the relevant contact surface in contact with the impeller opening ring gap is obtained, so that the grid division difficulty and the calculated amount are greatly reduced; and in the second stage, the resistance coefficient of the impeller opening ring gap is calculated according to the pressure distribution information on the relevant contact surface, and the local resistance coefficient near the inlet and the outlet where the impeller opening ring gap and the main flow region are transited is supplemented, so that the leakage flow value of the impeller opening ring gap is calculated, the estimation precision is better ensured, and the pertinence is strong.
2. The method is simple and convenient to operate, has wide adaptability, and is very suitable for the estimation requirement of the impeller opening ring clearance leakage amount under different flow working conditions in the design stage of the centrifugal pump.
Drawings
FIG. 1 is a flow chart of the present invention.
Fig. 2 is a front view of an assembly of a water body inside a centrifugal pump shown in full section in an embodiment of the present invention, in which 1 is a suction chamber, 2 is an impeller region, 3 is a pumping chamber, 11 is a centrifugal pump inlet surface on the suction chamber, and 31 is a centrifugal pump outlet surface on the pumping chamber.
Fig. 3 is a left side view of the assembly of the internal water body of the centrifugal pump shown in full section in the embodiment of the invention, wherein 1 is a water suction chamber, 2 is an impeller area, 3 is a water pressing chamber, 4 is an impeller opening ring gap on the left side, and 5 is an impeller opening ring gap on the right side.
Fig. 4 is a partially enlarged view of the left impeller eye gap and its vicinity indicated by a dashed line frame in fig. 3, in fig. 4, 1 is a suction chamber, 2 is an impeller region, 3 is a pumping chamber, and 4 is the left impeller eye gap.
Fig. 5 is a structural diagram of the left impeller eye gap, 4 in fig. 5 is the left impeller eye gap, 41 is an inlet face of the left impeller eye gap, and 42 is an outlet face of the left impeller eye gap.
The invention is further described below with reference to the figures and examples.
As shown in fig. 1, a simulation estimation method for the leakage amount of the centrifugal pump impeller opening ring gap is used for estimating the leakage flow amount of the gap between the centrifugal pump impeller and the opening ring under a specific delivery flow rate by combining computer simulation analysis, and is characterized by comprising the following steps:
step (1), drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, and separating and marking contact surfaces of parts in contact with the impeller opening ring gap:
drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, including a water suction chamber, a water pumping chamber, an impeller area and an impeller opening ring gap, and aiming at parts in contact with the impeller opening ring gap, separating and marking contact surfaces between the parts and the impeller opening ring gap.
And (2) under the condition of neglecting the impeller opening ring gap, calculating and obtaining the pressure distribution on the contact surface of the part in contact with the impeller opening ring gap by using computational fluid dynamics software:
and (2) removing the parts of the impeller opening ring gap, dividing grids, performing simulation calculation of the full-flow area in the centrifugal pump by using a computational fluid dynamics software tool, and obtaining a pressure distribution data matrix on the contact surface of the parts in contact with the impeller opening ring gap under a specific delivery flow rate according to the three-dimensional assembly drawing drawn in the step (1).
The step (2) is specifically divided into the following substeps:
substep (2.1), removing impeller opening ring gap parts aiming at the three-dimensional assembly drawing drawn in the step (1), and then reassembling to obtain a three-dimensional assembly drawing of the water body in the centrifugal pump, including a water suction chamber, a water pumping chamber and an impeller region;
substep (2.2), aiming at the three-dimensional assembly drawing of the water body in the centrifugal pump obtained in substep (2.1), dividing grids, setting boundary conditions, and performing simulation calculation of the full flow area in the centrifugal pump under specific delivery flow by using a computational fluid dynamics software tool;
in the setting boundary condition in the substep (2.2), a contact surface contacting with the impeller eye gap is set as a wall surface condition;
and (2.3) sequentially extracting pressure distribution data on a contact surface in contact with the impeller opening ring gap to form a plurality of data matrixes, wherein each contact surface in contact with the impeller opening ring gap corresponds to one pressure distribution data matrix.
And (3) aiming at a certain impeller opening ring gap with leakage quantity needing to be estimated, selecting the corresponding pressure distribution data matrix obtained in the step (2) as the inlet and outlet boundary condition information, and calculating by using computational fluid dynamics software to obtain a leakage flow simulation value Q of the pressure distribution data matrixnAnd the average pressure difference Δ P between the inlet and outlet faces:
determining needEstimating a certain impeller opening ring gap of leakage amount, extracting a corresponding part three-dimensional graph from the assembly body obtained in the step (1), dividing a grid, extracting a pressure distribution data matrix on a contact surface in contact with the impeller opening ring gap from the data matrix obtained in the step (2) to serve as inlet and outlet boundary condition information of the impeller opening ring gap, and calculating by using computational fluid dynamics software to obtain a leakage flow simulation value QnAnd the average pressure difference Δ P between the inlet and outlet faces is obtained by subtracting the average pressure value at the inlet face from the average pressure value at the outlet face.
The step (3) is specifically divided into the following substeps:
substep (3.1) determining a certain impeller opening ring gap of which the leakage amount needs to be estimated, and extracting a part three-dimensional diagram corresponding to the impeller opening ring gap from the assembly obtained in the step (1);
substep (3.2) of meshing the three-dimensional drawing of the part obtained in substep (3.1);
extracting a part three-dimensional graph corresponding to the impeller opening ring gap in the substep (3.1), wherein the position three-dimensional coordinate information of the part three-dimensional graph is consistent with the position three-dimensional coordinate information of the original assembly body of the part in the substep (1);
substep (3.3) of comparing pressure distribution data matrixes on two contact surfaces in contact with the impeller opening ring gap from the data matrix obtained in step (2) aiming at the impeller opening ring gap determined in substep (3.1), taking the contact surface corresponding to the data matrix with a higher average pressure value as a first contact surface, and taking the contact surface corresponding to the data matrix with a lower average pressure value as a second contact surface;
substep (3.4) regarding the impeller opening ring gap determined in substep (3.1), taking a surface of the opening ring gap, which is in contact with the first contact surface, as an inlet surface, taking a surface of the opening ring gap, which is in contact with the second contact surface, as an outlet surface, setting the inlet surface and the outlet surface as boundary conditions of a pressure inlet and a pressure outlet respectively, and adding pressure distribution data matrixes corresponding to the first contact surface and the second contact surface as information of the boundary conditions of the pressure inlet and the pressure outlet respectively;
substeps of(3.5) obtaining a simulated value Q of the leakage flow of the impeller opening ring gap by using computational fluid dynamics softwarenAnd the average pressure difference Δ P between the inlet and outlet faces is obtained by subtracting the average pressure value at the inlet face from the average pressure value at the outlet face.
Step (4), aiming at the leakage flow simulation value Q of a certain impeller opening ring gap with the leakage amount needing to be estimated, obtained in the step (3)nAnd the average pressure difference delta P between the inlet and outlet surfaces, and calculating the resistance coefficient zeta of the impeller opening ring gapn：
In the formula (1), g is the gravity acceleration and the unit is m/s2(ii) a Delta P is the average pressure difference between the inlet and outlet surfaces of the impeller opening ring gap expressed by the height of a water column, and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2；QnIs a simulated value of the leakage flow of the impeller opening ring gap, and the unit is m3/s；
Step (5), aiming at the average pressure difference value delta P between the inlet and outlet surfaces of the certain impeller opening ring clearance with the leakage quantity needing to be estimated, obtained in step (3), and the resistance coefficient zeta of the impeller opening ring clearance, obtained in step (4)nAnd calculating the leakage flow estimated value Q of the impeller opening ring gap:
in the formula (2), ζ1For suddenly decreasing local resistance coefficient value, zeta, between impeller opening ring gap and fluid area near its inlet1The value is between 0.8 and 1.2; zeta2Is the sudden expansion of the local resistance coefficient value, zeta, between the impeller eye gap and the fluid field in the vicinity of its outlet2The value is between 0.2 and 0.5; zetanCalculating the resistance coefficient of the impeller opening ring gap obtained in the step (4); g is the acceleration of gravity in m/s2(ii) a Δ P is obtained in step (3) orThe water column height represents the average pressure difference between the inlet and outlet surfaces of the impeller opening ring gap, and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2。
Examples
Rated flow of a certain centrifugal pump is 620m3The rated lift is 26m, the rated rotating speed is 1480r/min, the whole section of the assembly front view of the water body in the centrifugal pump is shown in figure 2, in the figure, 1 is a water suction chamber, 2 is an impeller area, 3 is a water pressing chamber, 11 is an inlet surface of the centrifugal pump on the water suction chamber, and 31 is an outlet surface of the centrifugal pump on the water pressing chamber; the left view of the assembly of the water body inside the centrifugal pump shown in full section is shown in figure 3, wherein 1 is a water suction chamber, 2 is an impeller area, 3 is a water pressing chamber, 4 is an impeller opening ring gap on the left side, and 5 is an impeller opening ring gap on the right side; for convenience of observation, the left impeller mouth ring gap marked by a dotted frame in fig. 3 and the area near the left impeller mouth ring gap are partially enlarged, as shown in fig. 4, 1 is a water suction chamber, 2 is an impeller area, 3 is a water pressing chamber, and 4 is the left impeller mouth ring gap; fig. 5 is a structural diagram of the left impeller eye gap, 4 in fig. 5 is the left impeller eye gap, 41 is the inlet face of the left impeller eye gap, and 42 is the outlet face of the right impeller eye gap.
For the centrifugal pump of the embodiment, the leakage amount estimation of the left impeller mouth ring clearance (4) under the rated flow working condition is roughly divided into the following steps:
And 2, calculating and obtaining the pressure distribution on the contact surface of the part in contact with the left impeller mouth ring gap (4):
removing parts of the left impeller opening ring gap (4) and the right impeller opening ring gap (5), reassembling and obtaining the water-sucking chamber (1), the water-pressing chamber (3) and the water-sucking chamberThe three-dimensional assembly drawing of the water body in the centrifugal pump in the impeller area (2) is divided into grids, boundary conditions are set, and 620m is carried out by using a computational fluid dynamics software tool Fluent3Simulation calculation of the full-flow area inside the centrifugal pump under the flow/h, wherein the set boundary conditions are as follows: the inlet is a speed boundary condition, the speed value is obtained by dividing the volume flow by the area of a centrifugal pump inlet surface (11) on the water suction chamber, and the speed is 3.50 m/s; the outlet is a pressure boundary condition, and the static pressure of an outlet face (31) of a centrifugal pump on the pumping chamber is set to be 0 Pa; setting an impeller region (2) to rotate at an angular speed of 1480r/min, wherein the rotating direction is anticlockwise; the interface conditions of the water suction chamber (1) and the impeller region (2) and the interface conditions of the water pumping chamber (3) and the impeller region (2) are respectively, and speed and pressure information among different regions is transmitted on the interface; the other surfaces including the contact surfaces of the water suction chamber (1) and the water pressing chamber (3) which are respectively contacted with the gap of the original impeller port are all wall surface conditions.
After the calculation is completed, the pressure distribution data on two contact surfaces of the water suction chamber (1) and the water pressure chamber (3) which are respectively contacted with the original left impeller opening ring gap (4) are respectively extracted to form 2 data matrixes, and in the embodiment, the comparison shows that the average pressure value on the contact surface of the water suction chamber (1) contacted with the original left impeller opening ring gap (4) is lower, and the average pressure value on the contact surface of the water pressure chamber (3) contacted with the original left impeller opening ring gap (4) is higher.
extracting a part three-dimensional graph of the impeller opening ring gap (4) on the left from the assembly body obtained in the step (1), wherein the position three-dimensional coordinate information of the part is consistent with the position three-dimensional coordinate information of the original assembly body of the part in the step (1); dividing grids; comparing the data matrix obtained in the step 2, and taking the contact surface of the pumping chamber (3) in contact with the original left impeller eye ring gap (4) as a first contact surface, and taking the contact surface of the water suction chamber (1) in contact with the original left impeller eye ring gap (4) as a second contact surface; the surface of the left impeller opening ring gap (4) contacting with the first contact surface is used as an inlet surfaceThe surface, which is in contact with the second contact surface, of the impeller opening ring gap is used as an outlet surface, an inlet surface (41) and an outlet surface (42) of the impeller opening ring gap (4) on the left side are respectively set as boundary conditions of a pressure inlet and a pressure outlet, and pressure distribution data matrixes corresponding to the first contact surface and the second contact surface are respectively added as information of the boundary conditions of the pressure inlet and the pressure outlet; calculating Fluent calculation by using computational fluid mechanics software, and obtaining a leakage flow simulation value Q of a left impeller opening ring gap (4) by a post-processing tool according to the calculation resultnIs 4.5 multiplied by 10-3m3And the average pressure difference Δ P between the inlet and outlet faces is obtained by subtracting the average pressure value at the inlet face from the average pressure value at the outlet face, which is expressed as the height of the water column as 4 m.
in the embodiment, the fluid in the centrifugal pump flows into the left impeller opening ring gap (4) from the pumping chamber (3) and flows out into the water suction chamber (1), the cross section in the impeller opening ring gap, which is vertical to the flowing direction of the leakage fluid, is a circular ring, and the area of the circular ring is 1.26 multiplied by 10-3m2So that the resistance coefficient value zeta of the left impeller opening ring gap (4) is calculatednComprises the following steps:
in the formula (1), g is the gravity acceleration and the unit is m/s2(ii) a Delta P is the average pressure difference between the inlet and outlet surfaces of the impeller opening ring gap expressed by the height of a water column, and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2；QnIs a simulated value of the leakage flow of the impeller opening ring gap, and the unit is m3/s；
And 5, calculating a leakage flow estimated value Q of the left impeller opening ring gap (4):
in this embodiment, the left impeller orifice ring gap (4) and the fluid region near the inlet are taken according to the specific centrifugal pump type and the structural characteristics of the orifice ringSuddenly reduced local drag coefficient ζ between11.0, the sudden expansion of the local resistance coefficient value ζ between the impeller eye gap (4) on the left and the fluid region in the vicinity of its outlet2Is 0.5, so the estimated leakage flow rate Q of the left impeller eye gap (4) is calculated as:
after the calculation of the step 5, the influence of local resistance loss near the inlet and the outlet of the impeller opening ring gap is considered, and the leakage flow of the left impeller opening ring gap (4) is determined by the simulated value Q of the step 3n＝4.5×10-3m3The estimated value Q is corrected to 4.03 × 10/s-3m3And/s is more consistent with the real situation.
In the present embodiment, the leakage flow rate of the impeller eye gap (4) on the left side is estimated, and similarly, the leakage flow rate of the impeller eye gap (5) on the right side may be estimated by the same method. In the embodiment, water body parts of the water suction chamber and the water pressing chamber are respectively contacted with the gap of the impeller opening ring, and the cross section in the gap of the impeller opening ring, which is vertical to the flowing direction of the leakage fluid, is a circular ring; in practical application, according to different design schemes, parts of the impeller region and the water body of the pumping chamber may be in contact with the impeller opening ring gap, and a cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap may have other shapes, even the cross section may change along with the flow direction, in which case the shape of the cross section may be calculated specifically, or a plurality of cross sections may be selected in sequence during the flow of the leakage fluid, and the average area of the cross sections may be taken as the value of the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap.
It should be pointed out that, the invention uses the computer simulation result to calculate the resistance coefficient value of the impeller mouth ring clearance, the resistance coefficient value is the result after integrating the on-way resistance loss and the local resistance loss in the impeller mouth ring clearance, so the applicability is wide, and the invention can also be used for calculating the resistance coefficient value of various irregular impeller mouth ring clearances such as labyrinth type and zigzag type.
The simulation estimation method for the centrifugal pump impeller opening ring gap leakage amount provided by the embodiment aims at the defects of complex meshing and large calculation amount of the current method of directly using a computational fluid dynamics tool to predict the centrifugal pump impeller opening ring gap leakage amount, and estimates the centrifugal pump impeller opening ring gap leakage amount through two main stages: in the first stage, the existence of the impeller opening ring gap of the centrifugal pump is ignored, the full flow field of the water body in the centrifugal pump under a specific flow rate is calculated, and the pressure distribution information on the relevant contact surface in contact with the impeller opening ring gap is obtained, so that the grid division difficulty and the calculated amount are greatly reduced; and in the second stage, the resistance coefficient of the impeller opening ring gap is calculated according to the pressure distribution information on the relevant contact surface, and the local resistance coefficient near the inlet and the outlet where the impeller opening ring gap and the main flow region are transited is supplemented, so that the leakage flow value of the impeller opening ring gap is calculated, the estimation precision is better ensured, and the pertinence is strong. The method is simple and convenient to operate, has wide adaptability, and is very suitable for the estimation requirement of the impeller opening ring clearance leakage amount under different flow working conditions in the design stage of the centrifugal pump.
Claims (5)
1. A simulation estimation method for the leakage amount of the gap between the impeller and the opening ring of the centrifugal pump is used for estimating the leakage amount of the gap between the impeller and the opening ring of the centrifugal pump under specific delivery flow by combining computer simulation analysis, and is characterized by comprising the following steps:
step (1), drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, and separating and marking contact surfaces of parts in contact with the impeller opening ring gap:
drawing a three-dimensional assembly drawing of a water body in the centrifugal pump, including a water suction chamber, a water pumping chamber, an impeller area and an impeller opening ring gap, and separating and marking contact surfaces between parts and the impeller opening ring gap aiming at the parts in contact with the impeller opening ring gap;
and (2) under the condition of neglecting the impeller opening ring gap, calculating and obtaining the pressure distribution on the contact surface of the part in contact with the impeller opening ring gap by using computational fluid dynamics software:
removing parts of the impeller opening ring gap, dividing grids, performing simulation calculation of a full-flow area in the centrifugal pump by using a computational fluid dynamics software tool, and obtaining a pressure distribution data matrix on a contact surface of the parts which are in contact with the impeller opening ring gap under a specific delivery flow rate according to the three-dimensional assembly drawing drawn in the step (1);
and (3) aiming at a certain impeller opening ring gap with leakage quantity needing to be estimated, selecting the corresponding pressure distribution data matrix obtained in the step (2) as the inlet and outlet boundary condition information, and calculating by using computational fluid dynamics software to obtain a leakage flow simulation value Q of the pressure distribution data matrixnAnd the average pressure difference Δ P between the inlet and outlet faces:
determining a certain impeller opening ring gap needing leakage amount estimation, extracting a corresponding part three-dimensional graph from the assembly body obtained in the step (1), dividing a grid, extracting a pressure distribution data matrix on a contact surface in contact with the impeller opening ring gap from the data matrix obtained in the step (2) to serve as inlet and outlet boundary condition information of the impeller opening ring gap, and calculating by using computational fluid dynamics software to obtain a leakage flow simulation value QnAnd subtracting the average pressure value of the inlet surface from the average pressure value of the outlet surface to obtain an average pressure difference value delta P between the inlet surface and the outlet surface;
step (4), aiming at the leakage flow simulation value Q of a certain impeller opening ring gap with the leakage amount needing to be estimated, obtained in the step (3)nAnd the average pressure difference delta P between the inlet and outlet surfaces, and calculating the resistance coefficient zeta of the impeller opening ring gapn：
In the formula (1), g is the gravity acceleration and the unit is m/s2(ii) a Delta P is the average pressure difference between the inlet and outlet surfaces of the impeller opening ring gap expressed by the height of a water column, and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2；QnIs a simulated value of the leakage flow of the impeller opening ring gap, and the unit is m3/s；
Step (5), aiming at the average pressure difference value delta P between the inlet and outlet surfaces of the certain impeller opening ring clearance with the leakage quantity needing to be estimated, obtained in step (3), and the resistance coefficient zeta of the impeller opening ring clearance, obtained in step (4)nAnd calculating the leakage flow estimated value Q of the impeller opening ring gap:
in the formula (2), ζ1For suddenly decreasing local resistance coefficient value, zeta, between impeller opening ring gap and fluid area near its inlet1The value is between 0.8 and 1.2; zeta2Is the sudden expansion of the local resistance coefficient value, zeta, between the impeller eye gap and the fluid field in the vicinity of its outlet2The value is between 0.2 and 0.5; zetanCalculating the resistance coefficient of the impeller opening ring gap obtained in the step (4); g is the acceleration of gravity in m/s2(ii) a Delta P is the average pressure difference value between the inlet and outlet surfaces of the impeller opening ring gap expressed by the height of the water column obtained in the step (3), and the unit is m; s is the area of the cross section perpendicular to the flow direction of the leakage fluid in the impeller opening ring gap and is expressed in m2。
2. The method for simulating and estimating the clearance leakage of the impeller eye ring of the centrifugal pump according to claim 1, wherein the step (2) is specifically divided into the following substeps:
substep (2.1), removing impeller opening ring gap parts aiming at the three-dimensional assembly drawing drawn in the step (1), and then reassembling to obtain a three-dimensional assembly drawing of the water body in the centrifugal pump, including a water suction chamber, a water pumping chamber and an impeller region;
substep (2.2), aiming at the three-dimensional assembly drawing of the water body in the centrifugal pump obtained in substep (2.1), dividing grids, setting boundary conditions, and performing simulation calculation of the full flow area in the centrifugal pump under specific delivery flow by using a computational fluid dynamics software tool;
and (2.3) sequentially extracting pressure distribution data on a contact surface in contact with the impeller opening ring gap to form a plurality of data matrixes, wherein each contact surface in contact with the impeller opening ring gap corresponds to one pressure distribution data matrix.
3. The method for simulating and estimating the clearance leakage of the impeller eye ring of the centrifugal pump according to claim 1, wherein the step (3) is specifically divided into the following substeps:
substep (3.1) determining a certain impeller opening ring gap of which the leakage amount needs to be estimated, and extracting a part three-dimensional diagram corresponding to the impeller opening ring gap from the assembly obtained in the step (1);
substep (3.2) of meshing the three-dimensional drawing of the part obtained in substep (3.1);
substep (3.3) of comparing pressure distribution data matrixes on two contact surfaces in contact with the impeller opening ring gap from the data matrix obtained in step (2) aiming at the impeller opening ring gap determined in substep (3.1), taking the contact surface corresponding to the data matrix with a higher average pressure value as a first contact surface, and taking the contact surface corresponding to the data matrix with a lower average pressure value as a second contact surface;
substep (3.4) regarding the impeller opening ring gap determined in substep (3.1), taking a surface of the opening ring gap, which is in contact with the first contact surface, as an inlet surface, taking a surface of the opening ring gap, which is in contact with the second contact surface, as an outlet surface, setting the inlet surface and the outlet surface as boundary conditions of a pressure inlet and a pressure outlet respectively, and adding pressure distribution data matrixes corresponding to the first contact surface and the second contact surface as information of the boundary conditions of the pressure inlet and the pressure outlet respectively;
substep (3.5) obtaining simulated impeller-mouth-ring-gap-leakage-flow value Q by calculation of computational fluid dynamics softwarenAnd the average pressure difference Δ P between the inlet and outlet faces is obtained by subtracting the average pressure value at the inlet face from the average pressure value at the outlet face.
4. A simulation method for estimating a leakage amount of a centrifugal pump impeller eye gap as set forth in claim 2, wherein in the setting of the boundary conditions as set forth in the substep (2.2), a contact surface with the impeller eye gap is set as a wall surface condition.
5. A simulation estimation method for the leakage of the centrifugal pump impeller eye ring gap as recited in claim 3, characterized in that said sub-step (3.1) extracts a three-dimensional drawing of the part corresponding to the impeller eye ring gap, and the three-dimensional coordinate information of the position of the part is consistent with the three-dimensional coordinate information of the position of the original assembly body of the part in the step (1).
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