CN107693868B - Design method of heart pump impeller and impeller - Google Patents
Design method of heart pump impeller and impeller Download PDFInfo
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- CN107693868B CN107693868B CN201710733191.6A CN201710733191A CN107693868B CN 107693868 B CN107693868 B CN 107693868B CN 201710733191 A CN201710733191 A CN 201710733191A CN 107693868 B CN107693868 B CN 107693868B
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M60/00—Blood pumps; Devices for mechanical circulatory actuation; Balloon pumps for circulatory assistance
- A61M60/20—Type thereof
- A61M60/205—Non-positive displacement blood pumps
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/20—Hydro energy
Abstract
The application provides a design method of a heart pump impeller and the impeller, and relates to the field of medical equipment. Firstly, calculating parameters of various impellers and pumps, and then drawing a preliminary axial surface flow channel according to the calculated size, so as to determine the shape of the axial surface flow channel; then, selecting and calculating the inlet edge blade setting angle, dividing the axial flow line into points and drawing a streamline square grid, thereby determining a blade thickening diagram and a blade wood pattern diagram, and finally carrying out impeller flushing hole optimization based on the heart pump impeller hydraulic optimization of the hemolysis shear rate index to obtain the centrifugal impeller meeting the hemolysis physiological index. The impeller is designed by the design method of the heart pump impeller and comprises a impeller base and blades, wherein the impeller base is provided with a balance hole along the axial direction. The application solves the technical problem that the design of the existing heart pump impeller needs to manufacture a prototype.
Description
Technical Field
The application relates to the technical field of medical equipment, in particular to a design method of a heart pump impeller and the impeller.
Background
The heart pump is a device for assisting in treating patients suffering from severe heart failure, and can partially or completely replace the blood pumping function of the heart, and the blood flowing direction in the impeller can be divided into axial flow, centrifugal flow, oblique flow and the like.
Most of the existing heart pump impeller designs consider the hydraulic performance of heart pump blood, and the physiological compatibility of the heart pump is ensured by combining impeller base materials, surface coatings and the like and by modification optimization after model experiment verification.
Based on the above, the application provides a design method of a heart pump impeller and the impeller to solve the technical problems.
Disclosure of Invention
The application aims to provide a design method of a heart pump impeller, which aims to solve the technical problem that a prototype is required to be manufactured in the existing heart pump impeller design.
The application also aims to provide an impeller which is used for solving the technical problem that the existing impeller is easy to form thrombus.
Based on the first object, the application provides a method for designing a heart pump impeller, which comprises the following steps:
step one, determining the shape of a blade by calculating the specific rotation speed of a pump;
step two, calculating the efficiency of the pump;
step three, calculating the shaft power and the prime motor power of the pump;
determining the inlet diameter, the outlet diameter, the inlet speed and the outlet speed of the pump;
step five, determining the diameter of an impeller inlet, the diameter of a blade inlet and a blade outlet, the width of an impeller outlet and the diameter of the impeller outlet;
step six, drawing a preliminary axial surface flow channel according to the sizes calculated in the step two to the step four, and further determining the shape of the axial surface flow channel;
step seven, selecting and calculating an inlet edge blade placing angle;
step eight, dividing points on the axial flow line and drawing a flow line square grid;
step nine, determining a blade thickening diagram and a blade wood pattern diagram;
step ten, hydraulic optimization of a heart pump impeller based on a hemolysis shear rate index;
and step eleven, based on the optimization effect of the step ten, the impeller is used for flushing the hole for optimization.
Optionally, in the first step, the specific rotation speed calculation formula of the pump isWherein Q is flow, H is lift, and n is rotation speed.
Optionally, in the second step, the pump is calculated first
Hydraulic efficiency
Volumetric efficiency
Mechanical efficiencyFinally calculate
Total efficiency η=η h η m η v 。
Optionally, in the third step, the shaft power calculation formula of the pump is as follows
The power calculation formula of the prime motor is p g ＝K g p/η t Wherein K is g As a safety factor eta t Is prime mover efficiency.
Optionally, in step four, the pump inlet diameter isPump outlet diameter D d ＝D s Inlet speed of pump>Pump outlet speed V d ＝V s Wherein V is s Is the inlet flow rate of the pump.
Optionally, in step six, according to the dimensions calculated in step two to step four, drawing a preliminary axial surface flow channel, then carrying out water cross section flow channel inspection on the axial surface flow channel, and determining the shape of the axial surface flow channel according to the result of the water cross section flow channel inspection.
Optionally, in step ten, firstly, modeling a full-runner hydraulic model, then, dividing grids, then, verifying grid independence, and finally, analyzing a calculation result to determine an improvement scheme and performing preliminary optimization.
Optionally, UG is used for modeling, and ICEM under ANSYS software is used for meshing.
Optionally, in step eleven, hydraulic model modeling and grid division are performed first, and then result analysis is performed.
Based on the second object, the application provides an impeller which is designed by the heart pump impeller design method, and comprises a impeller base and blades, wherein a balance hole is formed in the impeller base along the axial direction.
The application provides a design optimization method of a centrifugal heart pump impeller and an optimized impeller form with a flushing hole, and combines the flow shear force index of blood hemolysis, in the design optimization of an impeller hydraulic model, the physiological compatibility index of the heart pump is ensured by adopting CFD (computational fluid dynamics) means, through the accurate capture and evaluation of the flow wall surface shear force in the heart pump, a prototype is not required to be manufactured, the optimization design of the impeller hydraulic molded line is realized, and the technologies such as materials, coatings and the like are combined on the basis.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a cross-sectional change curve of water;
FIG. 2 is an axial flow channel shape;
FIG. 3 is an axial flow path division diagram;
FIG. 4 is an impeller inlet side and impeller inlet velocity triangle;
FIG. 5 is an axial streamline split;
FIG. 6 is a flow line square grid;
FIG. 7 is a blade thickening;
FIG. 8 is a blade wood pattern diagram;
FIG. 9 is a diagram of a full flow channel three-dimensional hydraulic model of a pump;
FIG. 10 is a diagram of a model of an impeller
FIG. 11 is a graph showing head, efficiency, maximum shear stress versus mesh number;
FIG. 12 is a graph of impeller speed vectors;
FIG. 13 is a three-dimensional flow diagram of an impeller;
FIG. 14 is a graph showing the percentage of pump internal stress;
FIG. 15 is a shear stress distribution of a blade surface;
FIG. 16 is an optimized heart pump impeller;
FIG. 17 is a graph showing the percentage of pump shear stress after optimization;
FIG. 18 is a block diagram of the impeller after opening;
FIG. 19 is a block diagram of an impeller with various openings;
FIG. 20 is a geometric model of the pump after tapping;
FIG. 21 is a flow chart of back clearance of an impeller;
FIG. 22 is an internal flow diagram of the impeller of section A of FIG. 18;
FIG. 23 is a graph of wall shear stress at the back shroud gap of the impeller;
fig. 24 is a schematic view of the impeller embodiment.
Icon: 1-wheel base; 2-leaf blades; 3-balance hole.
Detailed Description
The following description of the embodiments of the present application will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the application are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
Method embodiment of cardiac Pump impeller design
In this embodiment, a method for designing a heart pump impeller is provided, including the following steps:
step one, determining the shape of a blade by calculating the specific rotation speed of a pump;
step two, calculating the efficiency of the pump;
step three, calculating the shaft power and the prime motor power of the pump;
determining the inlet diameter, the outlet diameter, the inlet speed and the outlet speed of the pump;
step five, determining the diameter of an impeller inlet, the diameter of a blade inlet and a blade outlet, the width of an impeller outlet and the diameter of the impeller outlet;
step six, drawing a preliminary axial surface flow channel according to the sizes calculated in the step two to the step four, and further determining the shape of the axial surface flow channel;
step seven, selecting and calculating an inlet edge blade placing angle;
step eight, dividing points on the axial flow line and drawing a flow line square grid;
step nine, determining a blade thickening diagram and a blade wood pattern diagram;
step ten, hydraulic optimization of a heart pump impeller based on a hemolysis shear rate index;
and step eleven, based on the optimization effect of the step ten, the impeller is used for flushing the hole for optimization.
The application provides a standardized and optimized design flow of a centrifugal heart pump impeller meeting the hemolysis physiological index, which can design the centrifugal impeller meeting the hemolysis physiological index without making a prototype for inspection.
A specific example is provided below to provide a clearer understanding of the design.
Example two
The patent provides a design optimization method of a centrifugal heart pump impeller and an optimized impeller form with a flushing hole finally, and combines the flow shear force index of blood hemolysis, and the optimization of the impeller hydraulic model design is realized by accurately capturing and evaluating the flow wall surface shear force in the heart pump through CFD (computational fluid dynamics) means, so that the optimized design of the impeller hydraulic molded line is realized, and the technology such as materials, coatings and the like are combined on the basis, so that the physiological compatibility index of the heart pump is ensured. The concrete explanation is as follows:
1. initial hydraulic design
1) Specific rotation speed selection
Left ventricular pump design parameters are known:
flow rate: q=5l/min=0.3 m/h, head: h=2.5 mH 2 O, rotational speed: n=5000 r/min.
Calculating the specific rotation speed of the pump:
the heart pump designed by the determination belongs to the category of centrifugal low-specific-speed pumps, and the shape of the vane is a cylindrical vane.
2) Calculating pump efficiency
a) Hydraulic efficiency
b) Volumetric efficiency
c) Mechanical efficiency
d) Overall efficiency
η＝η h η m η v ＝0.7835×0.9657×0.9210＝0.6969
3) Shaft power and prime mover selection
Shaft power of pump:
the pump is driven by magnetic force and is provided with eta t Security factor k=1 g Taking 1.2.
Prime mover power:
p g ＝K g p/η t ＝1.2×2.93＝3.52(W)
let-down pump inlet flow velocity v s =1.1 m/s, the pump inlet diameter
Pump outlet diameter D d ＝D s Pump inlet speed:
pump out speed
V d ＝V s ＝1.06m/s
5) Calculation and determination of pump principal geometric parameters
a) Impeller inlet diameter D j
Taking coefficient K 0 =3.6, then impeller inlet equivalent diameter
Impeller inlet diameter:
the specific rotation speed of the pump is low, and the coefficient k is taken 1 =0.9, then diameter at blade inlet D 1 ＝k 1 D j ＝9mm。
b) Impeller outlet width b 2 Calculation of (2)
c) Impeller outlet diameter D 2 Is a preliminary calculation of (2)
6) Drawing of impeller axial surface flow channel and blade
According to the calculated geometric dimensions, a preliminary axial surface runner is drawn by proper straight lines and circular arcs, then the axial surface runner is checked, the water cross section change curve of the runner monotonically rises (figure 1), and is smoother, and the requirements on efficiency and cavitation are basically met, so that the axial surface runner shape can be preliminarily determined (figure 2).
When the flow of the shaft is split, only one middle streamline is needed because the specific rotation speed of the designed pump is small. The middle dividing line is drawn first, the flow passing area of the tangential inscribed circle measured by the two dividing lines is calculated to be equal, and therefore the position of the middle dividing line is determined, and the axial flow passage is divided into the graph 3.
7) Selection and calculation of inlet side blade setting angle
As shown in FIG. 4, the blade inlet angle is generally greater than the flow angle, i.e., β 1 >β′ 1 . Forming a positive attack angle delta beta at the inlet of the impeller: Δβ=β 1 -β′ 1 。
Is arranged at the inlet of the impeller and is a normal inlet, v u1a ＝0。
The peripheral speed at the inlet of the blade is:
the axial surface speed at the inlet of the blade is as follows:
wherein:
where D is the diameter, λ is the flow angle, δ is the blade thickness, subscript 1 indicates the inlet, a is the point a in FIG. 4 (a)
Let the thickness of the blade at the inlet be 0.5mm lambda 1 =90°. Taking delta beta 1i =3°. The inlet side blade setting angle was calculated using table 1.
TABLE 1 blade inlet edge setting angle calculation table
Taking: beta 1a ＝25°,β 1b ＝28°,β 1c ＝35°。
8) Axial surface streamline dividing point and streamline drawing square grid
For processing, two-dimensional blades are adopted, so that the blade profile is designed according to one streamline. The following is designed according to the intermediate flow line as in fig. 5.
After dividing each streamline in the axial flow channel, the corresponding streamline can be drawn in the square grid. Firstly, the blade placing angle at the inlet of each streamline is met, and then the position of the intersection point of the blade inlet edge and each streamline on the grid network is determined according to the streamline point diagram. The wrap angle of the blade is adjusted so that the lengths from the intersection point of the extension lines of the inlet angle and the outlet angle of the middle streamline to the starting point of the inlet and outlet edges are approximately equal. As shown in fig. 6, the blade wrap angle is 106 °.
9) Blade thickening and blade wood pattern drawing
Because the blade is a two-dimensional cylindrical blade designed according to the back cover plate, the thickness of the blade is only required to be thickened between the two plates (as shown in figure 7), in order to reduce the extrusion coefficient, the thickness treatment of the blade inlet is reduced, and the minimum thickness of the blade of the final impeller is 0.5mm, and the maximum thickness is 1mm. Finally, a blade wood pattern is obtained (as shown in fig. 8).
2. Cardiac pump impeller hydraulic optimization based on hemolysis shear rate index
1) Full flow channel hydraulic model modeling
The three-dimensional full flow channel modeling of the flow channel of the pump is performed by using the two-dimensional hydraulic model diagram designed in the previous section, namely fig. 7 and 8, wherein the clearance fluid field of the back cover plate is ignored first in order to provide calculation efficiency. And drawing a three-dimensional drainage basin diagram of the heart pump flow channel by adopting the UG graph, wherein the drawing area comprises an inlet section, an impeller, a volute and an outlet section. The inlet pipe inlet diameter is 10mm and its length is about 10 times the impeller inlet diameter. The impeller is convenient to process, processing cost is saved, processing precision is improved, and a semi-open impeller is adopted, so that the clearance of the blade tip of the impeller is 0.2mm on the premise that the processing precision and the assembly precision of the impeller can be achieved. As in fig. 9, 10.
2) Grid division
Grid division is performed using the ICEM under ANSYS software. In order to save time and improve calculation accuracy, the water inlet pipe, the water outlet pipe and the water pumping chamber adopt hexahedral grids, the impeller adopts tetrahedral grids, and areas such as blade tip gaps, water pumping chamber partition tongues and the like are encrypted to simulate flow characteristics at the details, and the number and the quality of grids of each drainage basin are shown in table 2.
TABLE 2 grid quantity and quality for each drainage basin
3) Grid independence verification
Because the quantity and the size of the grids have larger influence on the simulation result, the accuracy of the calculation result can be improved to a great extent by the proper quantity of the grids, but the waste of computer resources is caused by the overlarge quantity of the grids. Therefore, the independence verification of grids needs to be carried out through different grid numbers, 6 different grid numbers are adopted in the calculation to carry out three-dimensional steady calculation under the same flow working condition, and the obtained pump lift, efficiency and shear stress curves are shown in fig. 11.
As can be seen from fig. 11, the lift and efficiency are changed from 1.83m and 53% to 1.89m and 54.9% respectively, and the change amounts are small as the number of grids is from 200 ten thousand to 400 ten thousand. This is because the external characteristics of the pump are not high in the number of grids, and 200 ten thousand grids have reached the calculation requirement, so that the external characteristics are almost unchanged by adding grids. However, the maximum shear stress change is larger under different grid numbers, and when the grid number is 350 ten thousand, the grid is continuously increased, the maximum shear stress change is not large, and the stability is started to be about 870 Pa. And comprehensively considering the calculation precision and the calculation cost, and finally adopting grids with the total number of 350 ten thousand to calculate.
4) Boundary conditions and turbulence model
In performing numerical simulations, the physical parameters of the fluid are set as parameters of the blood: the density is 1050kg/m, the viscosity coefficient is 0.005Pa s, the rotating speed is 5000r/min, and the flow working condition is 5L/min. Adopting boundary conditions of a speed inlet and a pressure outlet, and setting the outlet pressure to 20000Pa; the hydraulic model area of the impeller is set as a Multiple Reference Frame model; the coupling of pressure and speed adopts a SIMPLEC algorithm; the convection item and the pressure gradient item both adopt a second-order windward differential format; the full flow path area of the pump was simulated using an SST k- ω turbulence model.
5) Analysis of the results of the calculation
a) Hydraulic performance of pump
The total pressure difference between the inlet and the outlet of the centrifugal pump is regarded as the pump lift, and the pump efficiency eta is calculated according to the following formula.
Wherein g represents gravitational acceleration, hm]Expressed as lift, qm 3 /h]Represent flow, M t Is torque, n [ rpm ]]Is the rotational speed.
The pump head h=1.90 m, η=52.4%.
b) Impeller streamline distribution
As can be seen from the velocity flow diagram of the impeller in fig. 12, the overall flow inside the impeller tends well, and the relative velocity of the blood reaches a maximum at the outlet. However, a local low-speed area appears on the suction surface of the outlet side of the blade and the pressure surface of the inlet side, and partial flow separation phenomenon also appears on the pressure surface of the inlet side. If the residence time of blood in this area is too long, thrombus formation may occur, and the shear stress is too long, which may cause rupture of red blood cells and hemolysis.
As can be seen from the three-dimensional flow diagram (fig. 13) of the impeller, due to the existence of the blade tip clearance of the impeller, a pressure difference exists between the pressure surface and the suction surface of the blade, fluid between the blades can flow from the pressure surface to the suction surface through the blade tip clearance, a series flow phenomenon occurs, and the fluid flow near the suction surface is disturbed, so that energy loss occurs. The larger the clearance is, the more the damage can be caused, so the blade tip clearance is reduced as much as possible under the condition of allowing the assembly precision, and the blade tip clearance can be kept at 0.2mm in the project study.
c) Shear force magnitude
The maximum shear stress of the pump is 1513Pa, and the damage to blood is large. However, from the analysis of the shear stress of the wall surface of the whole pump in FIG. 14, the shear stress value of 82% of the wall surface area is less than 250Pa, and the ratio of the area more than 1000Pa is almost 0, but the effect of the shear stress value of 82% of the wall surface area is still not negligible because the shear stress of 1000Pa or more can cause instantaneous rupture of erythrocytes although the ratio is small. As can be seen from the analysis of the wall shear stress shown in fig. 15, the places with larger shear stress are mainly concentrated near the inlet edge of the blade, near the outlet edge of the pressure surface of the blade and at the gap at the front end of the blade, which is probably caused by the fact that when blood just enters the impeller, the blood collides against the inlet edge and has large gradient of velocity change, and the places near the outlet are dynamic and static river basin junction surfaces, so that the velocity gradient change is also larger, and the shear stress is larger. The excessive shear stress at the blade gap is also due to the excessive velocity gradient, because the blade rotates at a high speed of 5000rpm, while the other side of the gap is a static wall surface, where the velocity of the upper end surface of the blade has a greater influence on the fluid velocity at the gap, and the shear stress is relatively greater.
d) Improved scheme
From the above analysis of the internal flow velocity and streamline of the flow-through part of the heart pump designed primarily, the wall shear stress distribution is known to require the optimization of the inlet and outlet of the impeller blades.
6) Preliminary optimization of pumps
a) Hydraulic model modeling and meshing
The three-dimensional shape of the optimized blade is shown in fig. 16.
b) Optimizing calculation result analysis
The maximum shear stress of the optimized centrifugal heart pump is 851Pa, which is far smaller than 1513Pa before optimization, the shear stress condition is obviously improved, and an extremely high shear stress area above 1000Pa is eliminated. The overall distribution of shear stress is not much different from that before optimization, but the shear stress at the blade inlet and outlet is significantly reduced. As can be seen from the shear stress distribution diagram shown in FIG. 17, the percentage of low shear stress (less than 250 Pa) in the heart pump is not significantly changed, and is still about 82%. The proportion of the medium stress region (250-500 Pa) is slightly increased by about 3%, while the proportion of the high stress region (higher than 500 Pa) is decreased by about equal to the percentage increase of the medium stress region. The above data demonstrate that the above optimization is evident in the improvement of local extremely high shear stress in the heart pump and the maximum shear stress in the left ventricular pump is greatly reduced. However, the region with medium shear stress does not reduce the shear stress due to the optimization measures, or the reduction is small, and the improvement of local high shear stress is obvious.
3. Optimization of impeller flushing holes
In the research of the project, the impeller of the blood pump is small in size, axial thrust is generated when the impeller rotates, and the impeller can possibly axially float, so that the size change and the performance of a gap at the front end of the impeller are unstable, and holes are needed to be added on the impeller to balance the axial force. In addition, the impeller has the function of washing the blood retained in the clearance of the rear cover plate, thereby avoiding thrombus. The structure after the impeller was perforated is as shown in fig. 18:
1) Modeling and meshing
In order to clarify the mechanism of impeller opening to clearance flow between the back cover plate and the pump shell, the internal flow characteristics and the hydraulic performance of the impeller are compared with the three different opening numbers, and under the condition that the geometric parameters of the impeller are unchanged, 2 (fig. 19 (a)) and 4 (fig. 19 (b)) holes are respectively arranged in a symmetrical mode, wherein the aperture is 2mm.
The geometric model of the pump after tapping is shown in figure 20.
The computational domain of the hydraulic model is mainly divided into 5 parts: the inlet pipe, the impeller, the hole, the pumping chamber and the gap between the impeller back cover plate and the pump shell.
The grid adopts a combination of tetrahedron and hexahedral grid, wherein the impeller basin adopts a tetrahedron grid, and the other basins all adopt hexahedral grid. The clearance and the flushing hole at the back of the impeller are taken as key calculation simulation research objects, grid refinement treatment is carried out on the area of the impeller, and the total grid number of the whole flow passage area is 580 ten thousand.
2) Results and analysis
Comparative analysis of hydraulic performance of three impellers at 5L/min flow operating point is shown in Table 3.
Table 3 hydraulic performance of impeller
As can be seen from the table, the pump head is reduced, the efficiency is reduced, and the axial force is reduced when the impeller is perforated, as compared with the hydraulic performance of the non-perforated impeller. From the simulation result, the pump lift meets the design requirement when the impeller is provided with 2 or 4 holes, and the efficiency of the 4-hole impeller is only 1.5% lower than that of the 2-hole impeller, which means that the number of holes has little influence on the hydraulic efficiency. But the axial thrust of the 4-hole impeller is reduced to 1/2 of that of the non-hole impeller, which greatly increases the safety of bearing operation. From the hydraulic performance analysis, it was found that 4 holes were suitable for processing the impeller.
The velocity field of the inner section B of the clearance flow channel between the impeller back cover plate and the pump shell is shown in figure 21, and the velocity field (a), (B) and (c) are flow field diagrams with 2 holes, 4 holes and no holes respectively, and the result shows that when the impeller is provided with holes, blood flows back to the impeller inlet from the back clearance of the impeller through the holes, the radial velocity of the blood in the back clearance of the impeller is accelerated by the flow, so that the blood can quickly flow out of the back clearance of the impeller without excessive stay at the back clearance of the impeller, and thrombus is avoided. The impeller pump model impeller without balance holes has smooth flow at the clearance of the back cover plate, but has low speed and slower blood flow speed, and can form thrombus. The radial speed of the 4-hole impeller is greater than that of the 2-hole impeller, so that blood can flow out of the pump more quickly.
The velocity field of the impeller inner section a is shown in fig. 22. (a), (b) and (c) are relative velocity flow diagrams with 2, 4 and no holes, respectively. The flow of the impeller with holes has larger velocity gradient near the holes, and compared with the velocity gradient of the flow field in the impeller without holes, the flow rate passing through the holes can cause the velocity of the flow field near the holes to be increased, the velocity of the suction surface of the blade is increased, and the velocity change of the flow field near 4 holes is more obvious than the velocity change of 2 holes.
From the analysis of the wall shear stress diagram of the impeller back shroud gap of fig. 23, the shear stress was locally increased around the holes, and the stress variation values with 2 holes and 4 holes were the same. In addition, the shear stress at the outer edge of the impeller, whether perforated or not, is not significantly changed.
3) Conclusion(s)
a) The velocity of the fluid flow at the back shroud gap of the perforated impeller is faster than that of a non-perforated impeller, but at the same time the hydraulic efficiency of the pump is reduced. The change of the number of the holes has little influence on the hydraulic efficiency of the impeller, but can obviously reduce the axial thrust, which has great significance for reducing the axial play of the rotor.
b) After the impeller is perforated, the flow speed of the fluid in the clearance flow channel between the impeller rear cover plate and the pump shell is increased, so that the fluid at the clearance can smoothly pass through the clearance behind the impeller, and the possibility of thrombus formation is greatly reduced.
c) The wall shear stress near the hole increases near the small hole area, but the shear stress at the outer edge of the impeller does not change much for smaller areas.
By making holes in the impeller, the likelihood of hemolysis and thrombus formation in the heart pump can be reduced. Therefore, the designed impeller of the blood pump should be perforated.
Impeller embodiment
As shown in fig. 24, this embodiment provides an impeller designed by the heart pump impeller design method described above, including a wheel base 1 and blades 2, on which wheel base 1 a balance hole 3 is axially provided.
The impeller designed according to the method meets the hemolysis physiological index and is not easy to generate thrombus.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.
Claims (5)
1. The design method of the heart pump impeller is characterized by comprising the following steps of:
step one, determining the shape of a blade by calculating the specific rotation speed of a pump;
step two, calculating the efficiency of the pump;
step three, calculating the shaft power and the prime motor power of the pump;
determining the inlet diameter, the outlet diameter, the inlet speed and the outlet speed of the pump;
step five, determining the diameter of an impeller inlet, the diameter of a blade inlet and a blade outlet, the width of an impeller outlet and the diameter of the impeller outlet;
step six, drawing a preliminary axial surface flow channel according to the sizes calculated in the step two to the step four, and further determining the shape of the axial surface flow channel;
step seven, selecting and calculating an inlet edge blade placing angle;
step eight, dividing points on the axial flow line and drawing a flow line square grid;
step nine, determining a blade thickening diagram and a blade wood pattern diagram;
step ten, hydraulic optimization of a heart pump impeller based on a hemolysis shear rate index;
step eleven, based on the optimization effect of step ten, the impeller is used for flushing the hole, wherein:
in the first step, the calculation formula of the specific rotation speed of the pump is as followsWherein Q is flow, H is lift, and n is rotation speed;
in the second step, the pump is calculated first
Hydraulic efficiency
Volumetric efficiency
Mechanical efficiencyFinal calculation of the total efficiency η=η h η m η v ；
In the third step, the shaft power calculation formula of the pump is as follows
The power calculation formula of the prime motor is p g ＝K g p/η t Wherein K is g As a safety factor eta t Is prime mover efficiency;
in step four, the inlet diameter of the pump isPump outlet diameter D d ＝D s Inlet speed of pump>Pump outlet speed V d ＝V s Wherein V is s Inlet flow rate for the pump;
and step six, drawing a preliminary axial surface flow channel according to the sizes calculated in the step two to the step four, then checking the axial surface flow channel through a water section flow channel, and determining the shape of the axial surface flow channel according to the result of checking the axial surface flow channel through the water section flow channel.
2. The method for designing a heart pump impeller according to claim 1, wherein in step ten, the full flow channel hydraulic model modeling is performed first, then grid division is performed, then grid independence verification is performed, and finally calculation result analysis is performed to determine the improvement scheme and preliminary optimization is performed.
3. The cardiac pump impeller design method of claim 2, wherein modeling is performed using UG and meshing is performed using ICEM under ANSYS software.
4. The method of designing a heart pump impeller according to claim 1, wherein in step eleven, hydraulic model modeling and meshing are performed first, and then result analysis is performed.
5. An impeller, characterized in that the impeller is designed by the method for designing a heart pump impeller according to any one of claims 1 to 4, and comprises a wheel base and blades, wherein a balance hole is formed in the wheel base along the axial direction.
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| CN111556763B (en) | 2017-11-13 | 2023-09-01 | 施菲姆德控股有限责任公司 | Intravascular fluid movement device and system |
| EP4085965A1 (en) | 2018-02-01 | 2022-11-09 | Shifamed Holdings, LLC | Intravascular blood pumps and methods of use and manufacture |
| CN108939182B (en) * | 2018-09-14 | 2023-10-13 | 长治市久安人工心脏科技开发有限公司 | Magnetic unloading control and detection system for artificial heart axial flow pump |
| IT201800009502A1 (en) * | 2018-10-16 | 2020-04-16 | Eurosets Srl | CENTRIFUGAL PUMP WITH MAGNETIC LEVITATION |
| IT201800009506A1 (en) * | 2018-10-16 | 2020-04-16 | Eurosets Srl | CENTRIFUGAL PUMP WITH MAGNETIC LEVITATION |
| US11964145B2 (en) | 2019-07-12 | 2024-04-23 | Shifamed Holdings, Llc | Intravascular blood pumps and methods of manufacture and use |
| US11654275B2 (en) | 2019-07-22 | 2023-05-23 | Shifamed Holdings, Llc | Intravascular blood pumps with struts and methods of use and manufacture |
| US11724089B2 (en) | 2019-09-25 | 2023-08-15 | Shifamed Holdings, Llc | Intravascular blood pump systems and methods of use and control thereof |
| CN113082506B (en) * | 2021-05-12 | 2023-04-28 | 苏州大学 | Blood pump applied to artificial heart |
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