Centrifugal blood pump with ultralow specific speed

Abstract

The centrifugal blood pump comprises a volute part and an impeller, the impeller is located in the volute part, the impeller comprises a plurality of blades distributed in the circumferential direction, the ends, close to the circle center of a base circle of the volute part, of the blades are the front ends, the other ends of the blades are the rear ends, and the rear ends of the blades are all located on the same outer normal circle; on the projection surface of the impeller projected in the axial direction, the arc lengths of the rear ends of all the blades in the circumferential direction account for 28%-54% of the perimeter of the outer normal circle; moreover, the projection area of all the blades projected in the axial direction is a first area, the area of the outer normal circle is a second area, and the first area accounts for 26%-47% of the second area. The centrifugal blood pump can achieve the working condition of ultralow specific speed.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a centrifugal blood pump with an ultra-low specific speed. Background Art

[0002] Conventional pumps typically have a specific speed of 30 or higher, with specific speeds between 20 and 30 considered low. There's a correlation between specific speed and pump type and basic shape. When designing a pump, the specific speed can be calculated based on the required speed, head pressure, and flow rate. This specific speed can then be used to find the corresponding pump type and basic shape. However, centrifugal blood pumps in the medical field may require ultra-low specific speeds, which are not achievable with existing pump designs. Summary of the Invention

[0003] The purpose of the present application is to provide a centrifugal blood pump with an ultra-low specific speed, which can achieve an ultra-low specific speed.

[0004] The present application provides a centrifugal blood pump with an ultra-low specific speed, comprising a volute portion and an impeller, wherein the impeller is located within the volute portion and comprises a plurality of blades distributed along the circumferential direction, wherein one end of the blade close to the center of the base circle of the volute portion is a front end, and the other end is a rear end, and the rear ends of the blades are all located on the same outer normal circle;

[0005] On the projection surface of the impeller along the axial direction, the arc length of the rear ends of all the blades along the circumferential direction accounts for 28% to 54% of the circumference of the outer normal circle; and the projection area of all the blades along the axial direction is a first area, the area of the outer normal circle is a second area, and the first area accounts for 26% to 47% of the second area.

[0006] Optionally, the specific speed of the centrifugal blood pump is not higher than 20.

[0007] Optionally, the blades include a first blade and a second blade, the length of the first blade is greater than the length of the second blade, and the first blade and the second blade are arranged alternately along the circumferential direction; the front ends of all the first blades are located on the same first inner normal circle, and the front ends of all the second blades are located on the same second inner normal circle; on the projection surface of the impeller along the axial direction, the arc length of the overlapping part of all the first blades and the second inner normal circle accounts for 22% to 34% of the circumference of the second inner normal circle.

[0008] Optionally, a first circle is defined, the radius of which is 1 mm larger than the radius of the first inner normal circle, and on the projection surface of the impeller along the axial direction, the arc length of the overlapping part of all the first blades and the first circle accounts for 39% to 46% of the circumference of the first circle.

[0009] Optionally, a second circle is defined, the radius of which is 1 mm larger than the radius of the second inner normal circle; on the projection surface of the impeller along the axial direction, the arc length of the overlapping parts of all the first blades and all the second blades and the second circle accounts for 36% to 53% of the circumference of the second circle.

[0010] Optionally, the volute portion is provided with a liquid inlet, and the blade has an upper side axially close to the liquid inlet and a lower side away from the liquid inlet; from bottom to top, the width of the blade along the circumferential direction is gradually reduced.

[0011] Optionally, the circumferential width of the upper side gradually changes from amm to bmm in the direction from the front end to the rear end, wherein the numerical range of a is 0.9 to 1.1, and the numerical range of b is 6 to 8; the width of the lower side gradually changes from cmm to dmm in the direction from the front end to the rear end, wherein the numerical range of c is 1.5 to 2, and the numerical range of d is 7 to 9.

[0012] Optionally, the impeller includes a circular chassis, and a plurality of blades are arranged circumferentially on the chassis, and the blades include a blade front section, a blade middle section, and a blade rear section that are connected in sequence from the inside to the outside, and the blade middle section is connected to the side of the chassis close to the liquid inlet, and the blade front section and the blade rear section are away from the side of the liquid inlet, and have an axial spacing with the side of the chassis close to the liquid inlet.

[0013] Optionally, the front end surface of at least one of the blades is a slope surface, the slope surface forms an angle with the transverse direction, the angle is an acute angle, and the transverse direction is perpendicular to the axial direction.

[0014] Optionally, the outlet angle, wrap angle, and inlet angle of the blade satisfy at least one of the following:

[0015] The outlet angle is 65° to 70°;

[0016] The wrap angle of the blade is 90° to 120°;

[0017] The inlet angle is 20° to 25°.

[0018] In this application, the ratio of the edge arc length of the rear end of all blades to the circumference of the outer normal circle is limited to 28% to 54%, and the ratio of the area of all blades to the outer normal circle is limited to 26% to 47%. The blades are relatively "wide and fat", in which case the blade displacement coefficient can be reduced. If the blades are relatively "slender", the above ratio will be less than the specified range, the impeller outlet displacement coefficient will be too large, the flow-pressure head curve (i.e., HQ curve) will decline too slowly, and the "hump" cannot be effectively removed. If the blades are too "wide and fat", the ratio will exceed the above specified range. At this time, as the flow rate increases, the HQ curve will show a steep drop, and it will not provide sufficient hydraulic performance at the design operating point. Therefore, after the above size restrictions are implemented, the pumping capacity of the blades can be increased even under low flow conditions to meet the hydraulic performance of high pressure head. Therefore, the centrifugal blood pump can meet the requirements of ultra-low specific speed. In specific applications, it can be used as a centrifugal blood pump for infants. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a centrifugal blood pump in an embodiment of the present application;

[0020] Figure 2 for Figure 1 Structural schematic diagram of a centrifugal blood pump;

[0021] Figure 3 For blood Figure 1 Schematic diagram of the flow path in a spiral flow channel;

[0022] Figure 4 for Figure 1 A schematic diagram of a plurality of blades 21;

[0023] Figure 5 Schematic diagram of the flow path of the centrifugal blood pump in the embodiment of the present application;

[0024] Figure 6 for Figure 4 The main view of the middle A part;

[0025] Figure 7 Schematic diagram of the flow-head curve of the centrifugal blood pump in the embodiment of the present application;

[0026] Figure 8 This is a schematic diagram of the flow-head curve of a traditional centrifugal pump in the low specific speed and small flow area;

[0027] Figure 9 A flow-head curve diagram of a centrifugal blood pump in an embodiment of the present application;

[0028] Figure 10 for Figure 1 A magnified view of the position of a single leaf;

[0029] Figure 11 for Figure 1 Schematic diagram of the structure of the middle impeller;

[0030] Figure 12 for Figure 11 Magnified view of area B.

[0031] Figure 13 These are two structural forms of the spiral flow channel 1a of the ultra-low specific speed centrifugal blood pump in the embodiment of the present application;

[0032] Figure 14 for Figure 13 Enlarged view of part A in the middle;

[0033] Figure 15 The statistical curve of domestic pumps and the Stepanov curve are shown.

[0034] Figure 1-15 The description of the accompanying drawings is as follows:

[0035] 100-pump head;

[0036] 1-Pump casing; 11-Voltage; 12-Diffuser; 121-First side; 122-Second side; 12a-Diffuser outlet; 13-Baffle; 14-Secondary flow channel; 15-Inlet; 16-Outlet; 1a-Spiral flow channel; 1a1-Upstream section; 1a2-Downstream section; 1b-Liquid inlet;

[0037] 2-Impeller;

[0038] 21-blade; 21a-blade front section; 21b-blade middle section; 21c-blade rear section; 21d-front notch; 21e-rear notch; 211-first blade; 212-second blade; 213-first side surface; 214-second side surface; 215-first side portion; 216-second side portion; 217-front end; 2171-front end corner; 218-rear end; 2181-rear end corner;

[0039] 22-Chassis. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0041] Please refer to Figures 1 to 4 , Figure 1 This is a schematic diagram of the structure of the centrifugal blood pump in the embodiment of the present application, illustrating the impeller 2 in the pump, from a top view; Figure 2 for Figure 1 Structural schematic diagram of a centrifugal blood pump; Figure 3 For blood Figure 1Schematic diagram of the blood flow path in the spiral flow channel 1a, with arrows indicating the direction of blood flow; Figure 4 for Figure 1 Schematic diagram of multiple blades 21.

[0042] This embodiment provides a centrifugal blood pump, which includes a pump head 100 and a motor. The motor is not shown in the figure. The pump head 100 includes a pump housing 1 and an impeller 2 located in the pump housing 1. Figure 2 As shown, the pump housing 1 includes a volute portion 11 and a secondary flow channel portion 14 distributed along the axial direction. The volute portion 11 and the secondary flow channel portion 14 can be connected separately or as an integrated structure. The volute portion 11 is provided with an inlet portion 15 and an outlet portion 16. The inlet portion 15 and the outlet portion 16 can be a tubular structure with a lumen for blood flow. Figure 2 As shown, the inlet portion 15 is arranged at one axial end of the volute portion 11, which can be defined as being arranged at the top of the volute portion 11, the secondary flow channel portion 14 is located at the bottom of the volute portion 11, and the outlet portion 16 is arranged on the side of the volute portion 11, and the impeller 2 is located in the inner cavity of the volute portion 11.

[0043] like Figure 1 As shown, a spiral flow channel 1a is formed between the impeller 2 and the inner wall of the volute 11, which surrounds the impeller 2. That is, the flow channel is spiral, and the inner wall of the volute 11 is gradually opened around the impeller 2, thereby forming the spiral flow channel 1a. The cross-sectional area of the spiral flow channel 1a increases from the inlet to the outlet. When the impeller 2 rotates, the blood is pumped to the spiral flow channel 1a. Figure 1 From this perspective, the impeller 2 rotates clockwise. A motor (not shown) in the centrifugal blood pump can drive the impeller 2 in the volute 11 to rotate. In this embodiment, the axial direction is defined as the direction in which the rotation axis of the impeller 2 extends. The circumferential and transverse directions are also defined with reference to the axial direction. The circumferential direction is the direction around the rotation axis, and the transverse direction is the direction perpendicular to the axial direction. Figure 1 What is shown is actually a transverse section of the volute 11. The centrifugal blood pump has a corresponding base circle X. The position where the rotation axis of the impeller 2 intersects the transverse section is the center O of the base circle X. A through hole is provided at the top of the volute 11 as a liquid inlet 1b (shown in FIG. Figure 3 ), the inlet portion 15 is connected to the liquid inlet 1b, and the center position of the liquid inlet 1b corresponds to the center O of the base circle X, that is, when the liquid inlet 1b is projected along the axial direction, the center of the projection of the liquid inlet 1b and the center O of the base circle X will coincide.

[0044] Blood enters the middle portion of the volute 11 from the liquid inlet 1b via the inlet 15. As the impeller 2 rotates and generates work, a portion of the blood enters the spiral flow passage 1a of the volute 11, while the remaining portion flows downward into the secondary flow passage 14 of the pump housing 1. The blood entering the secondary flow passage 14 is recirculated back to the impeller 2. The blood entering the volute 11 is decelerated and pressurized after passing through the spiral flow passage 1a of the volute 11, ultimately flowing out of the outlet 16. The operating principle of a centrifugal blood pump is conventional, and can be understood by referring to, for example, CN115040775A, and will not be further discussed in this embodiment. In addition, the centrifugal blood pump in this embodiment is specifically open, that is, the two side surfaces of the impeller 2 along the axial direction are basically not covered by a cover, and the top and bottom of the volute portion 11 are not covers covering the impeller 2, and there is a certain distance between them and the two side surfaces of the impeller 2 in the axial direction. In this way, the impeller 2 can rotate relatively freely in the volute portion 11, reducing mechanical losses and damage to the blood. For example, in this embodiment, the impeller 2 can be magnetically suspended or hydraulically suspended, suspended in the volute portion 11. Of course, the impeller 2 can also be supported in the volute portion 11 by bearings, and this embodiment does not limit this.

[0045] In detail, such as Figure 1 and Figure 4 As shown, the impeller 2 in this embodiment includes a plurality of blades 21 distributed along the circumferential direction. In fact, the plurality of blades 21 are also arranged around the center O of the base circle X. The end of the blade 21 close to the center O of the base circle X is defined as the front end 217, and the other end away from the center O is defined as the rear end 218 of the blade 21. The fluid contacts the blade 21 from the front end 217 and is discharged from the rear end 218, that is, the front end 217 of the blade 21 is the inlet side, and the rear end 218 of the blade 21 is the outlet side. The rear ends 218 of the plurality of blades 21 are arranged along a concentric circle concentric with the base circle X, and the concentric circle is defined as the outer normal circle X1. Figure 1 、 4 In the embodiment, the rear ends 218 of the plurality of blades 21 extend roughly along an arc shape, and the arc edge of the rear ends 218 coincides with a portion of the outer normal circle X1. The outer normal circle X1 and the base circle X do not coincide with each other, and there is a small gap between them in the radial direction. The diameter of the base circle X is obtained by multiplying a certain coefficient on the basis of the diameter of the outer normal circle X1. Specifically, in this embodiment, the distance between the outer normal circle X1 and the base circle X, that is, the distance between the rear ends 218 and the base circle X in the lateral direction, can be set to approximately 1 mm.

[0046] It should be noted that the multiple blades 21 in this embodiment have two specifications, namely the first blade 211 and the second blade 212, wherein the length of the first blade 211 from the front end to the rear end is greater than the length of the second blade 212, that is, the first blade 211 is a long blade and the second blade 212 is a short blade. The first blade 211 and the second blade 212 are arranged alternately along the circumferential direction, and the front end 217 of the first blade 211 is closer to the center O of the base circle X. The center O of the base circle X is coaxial with the liquid inlet 1b of the pump housing 1. Such an arrangement is more conducive to the distribution of the multiple blades 21, so that the front ends 217 of some long blades can be closer to the center O to better pump blood. The rear ends 218 of the first blade 211 and the second blade 212 are flush in the circumferential direction, that is, the rear ends 218 of the two specifications of blades 21 are distributed on the outer normal circle X1. The relationship between the first blade 211 and the second blade 212 can be understood as follows: the second blade 212 is formed by cutting off a portion of the front end 217 of the first blade 211. Of course, after cutting off, the front end 217 of the second blade 212 must be kept smooth. In this way, when there are a large number of blades 21, the front end 217 of the longer blade can be closer to the center O, and the front ends of the multiple blades 21 can be prevented from interfering with each other.

[0047] like Figure 4 As shown, this embodiment further defines a first inner normal circle X5 and a second inner normal circle X3, wherein the front ends 217 of the plurality of first blades 211 are tangent to the first inner normal circle X5, and the front ends 217 of the plurality of second blades 212 are tangent to the second inner normal circle X3. Furthermore, the following conditions are satisfied:

[0048] On the axially projected surface of the impeller 2, the arc length of the arcuate edge of the rear end 218 of all first blades 211 and second blades 212 accounts for a ratio of 28% to 54% of the circumference of the outer normal circle X1. This limits the circumferential size ratio of the rear end 218 of the first blades 211 and second blades 212, which can be defined as a first size ratio range. Furthermore, the total axially projected area of the multiple blades 21 in this embodiment is defined as a first area, and the circular area of the outer normal circle X1 within which the rear end 218 of the multiple blades 21 lie is defined as a second area. Following these limitations, the ratio of the first area to the second area in this embodiment is approximately 26% to 47%, which can be defined as a second size ratio. This configuration not only limits the ratio of the arc length of the rear end 218 of the blades 21 to the circumference of the outer normal circle X1, but also limits the area ratio of the blades 21, thereby defining the shape of the blades 21.

[0049] So set up, from Figure 1 It can be seen from the figure that the projected area of the outer normal circle X1 occupied by the multiple blades 21 in this embodiment is relatively large. Compared with the blades of a conventional centrifugal pump in the prior art, the blades 21 in this embodiment are structurally "wider and fatter".

[0050] When designing a pump, specific speed is a key technical indicator. Currently, there is a corresponding relationship between specific speed and pump type and basic shape. When the specific speed of the required pump is known, the type and basic shape of the pump can be determined based on the existing corresponding relationship. At the same time, the correlation coefficient can be determined. The design parameter size of the pump can be calculated based on the correlation coefficient and the known formula. Specific speed n s The algorithm is:

[0051]

[0052] Where n is the motor speed in rpm; Q is the flow rate in m 3 / s; H is the pressure head, in meters. Simply set the speed, flow rate, and pressure head requirements to calculate the specific speed. Based on the correspondence between the specific speed and the pump type and basic shape, the pump type and basic shape can be determined, and the approximate design parameters of the pump that meets the requirements can be calculated.

[0053] It should be noted that the centrifugal blood pump in this embodiment is a device used to assist patients in pumping blood. Its application is not widespread and differs significantly from conventional power pumps used for pumping oil, water, and other applications, with parameter requirements not entirely consistent. For example, the specific speed of conventional pumps is generally above 30, i.e., the specific speed of pumps in the prior art is usually above 30. A specific speed between 20 and 30 is considered low. However, centrifugal blood pumps may require ultra-low specific speeds. For example, when used for children, centrifugal blood pumps require low flow rates and high pressure heads. The motor speed is primarily determined by the selected model, and the speed range varies little. Therefore, the calculated specific speed will be no higher than 20, which is considered ultra-low. For example, based on one of the operating conditions of an infant blood pump, the centrifugal blood pump is designed with a speed n = 2800 rpm, a flow rate Q = 0.6 Lpm, and a pressure head H = 250 mmHg. According to the above specific speed algorithm formula, after converting the units and substituting them into the calculation, the calculated specific speed is only 12.91. That is, the specific speed of the centrifugal blood pump designed in the embodiment of the present application is lower than 20, which is an ultra-low specific speed. Thus, the existing correspondence table between specific speeds and pump types and basic shapes does not cover this ultra-low specific speed. In other words, the existing pump design scheme cannot meet the design requirements of a centrifugal blood pump with an ultra-low specific speed.

[0054] In this embodiment, when designing the centrifugal blood pump, taking into account the characteristic requirements of ultra-low specific speed, the structure of the blade 21 is specifically studied and designed, and the size of the blade 21 of the centrifugal blood pump is specifically changed. As mentioned above, the ratio between the circumferential size of the rear end of the blade 21 and the circumference of the outer normal circle X1 at the corresponding position is limited, and the ratio between the projected area of the blade 21 and the area of the outer normal circle X1 is limited. As a result, the blade 21 is relatively wide and fat, and the ratio of the first area to the second area reaches 26% to 47%. The shape of the blade 21 is quite different from the existing impeller design.

[0055] The structural parameters of the centrifugal blood pump mainly include the diameter D of the liquid inlet 1b j , the diameter D2 of the outlet side of the blade 21 (ie the diameter of the outer normal circle X1), the thickness b2 of the outlet side of the blade 21 and the diameter D3 of the base circle X. Figure 5 、 6 understand, Figure 5 Schematic diagram of the flow channel of the centrifugal blood pump in the embodiment of the present application, that is, only the cavity portion of the flow channel is illustrated, and the portion that can be filled with fluid is indicated by a solid line, or it can also be called a water body diagram; Figure 6 for Figure 5 The main view of part A in the middle, or it can also be called the axial view or meridian view of part A.

[0056] The structural parameters of the pump can be calculated according to the existing formula, as shown in Table 1 below, where n is the speed, n s is the specific speed, Q is the flow rate, and the coefficients k0 and k D2 、k D3 、k b2 , but as mentioned before, the coefficients k0, k D2 、k D3 、k b2 It is determined by the specific speed, but there is no corresponding coefficient for ultra-low specific speeds. In this case, when calculating, the flow rate Q in the formula can be increased. For example, substituting 1 to 1.2 Lpm will give 1.67Q to 2Q.

[0057] Table 1

[0058]

[0059]

[0060] As mentioned above, if the ratio of the edge arc length of the rear end 218 of all blades 21 to the circumference of the outer normal circle X1 is limited to 28% to 54%, and the ratio of the area of all blades 21 to the outer normal circle X1 is limited to 26% to 47%, then the blades 21 are relatively "wide and fat", and in this case, the displacement coefficient of the blades 21 can be reduced. If the blades are set to be relatively "slender", the above ratio will be less than the specified range, and the outlet displacement coefficient of the impeller 2 will be too large, and the flow-pressure head curve (i.e., HQ curve) will drop too slowly, and the "hump" cannot be effectively removed; if the blades are set to be too "wide and fat", the ratio will exceed the above specified range. At this time, as the flow rate increases, the HQ curve will drop sharply again, and it will be impossible to provide sufficient hydraulic performance at the design operating point. Therefore, after the above-mentioned size limitation is made, the pumping capacity of the blade 21 can also be increased under the condition of small flow rate to meet the hydraulic performance of high-pressure head. Therefore, the centrifugal blood pump can meet the requirements of ultra-low specific speed. Specifically, when used, it can be used as a centrifugal blood pump for infants. Of course, for centrifugal blood pumps used by adults, if there is a characteristic that requires ultra-low specific speed, the centrifugal blood pump in the embodiment of the present application can also be used, and it is not necessarily limited to use by infants.

[0061] Please refer to Figure 7 , Figure 7 Schematic diagram of the flow-pressure curve of the centrifugal blood pump in the embodiment of the present application. The horizontal axis of the flow-pressure curve is the flow rate in Lpm, and the vertical axis is the pressure in mmHg.

[0062] Model 1 represents the HQ curve obtained when the centrifugal blood pump blade size is less than the lower limit of the two aforementioned size ratios; Model 2 represents the HQ curve obtained when the centrifugal blood pump blade size is at the lower limit of the two aforementioned size ratios; Model 3 represents the HQ curve obtained when the centrifugal blood pump blade size is at the upper limit of the two aforementioned size ratios; and Model 4 represents the HQ curve obtained when the blade size is greater than the upper limit of the two aforementioned size ratios. It can be seen that when the size ratio is too small, the HQ curve decreases too slowly, resulting in a "hump"; while when the size ratio is too large, the HQ curve decreases too rapidly, failing to meet hydraulic performance requirements.

[0063] Furthermore, this embodiment of the present application limits the ratio of the arc length of the portion of the first blade 211 that overlaps the second inner normal circle X3 to a ratio of 22% to 34% of the circumference of the second inner normal circle X3, which can be defined as a third dimensional ratio range. This limits the circumference ratios at the front end 217 and rear end 218 of the first blade 211, respectively. Furthermore, while the dimensional ratios along the circumference of the front end 217 of the first blade 211 are limited, as previously mentioned, the dimensional variation trend of the second blade 212 from the rear end 218 to the front end 217 is essentially the same as that of the first blade 211 within the same length range, except that the second blade 211 is shorter. Therefore, the dimensional ratios along the circumference of the front ends 217 of the first and second blades 211, 212, can also be limited. That is, after defining the first dimensional ratio and the second dimensional ratio of the area ratio, defining the third dimensional ratio of the circumference ratio of the front end 217 further defines the shape of the blade 21, ensuring that the blade 21 is configured in a wide-to-wide manner, so that the blade 21 can better meet the requirements of an ultra-low specific speed centrifugal blood pump.

[0064] Look again Figure 4 , a first circle X4 is further defined. The radius of the first circle X4 is 1 mm larger than the radius of the first inner normal circle X5. On the axial projection surface of the impeller 2, the arc length of the overlapping portion of all first blades 211 and the first circle X4 accounts for 39% to 46% of the circumference of the first circle X4, which can be defined as a fourth size ratio range. Figure 4 As shown, the first inner normal circle X5 is tangent to the front ends 217 of the plurality of first blades 212. When X5 is moved 1 mm away from the center of the circle, the first circle X4 and the first blade 211 overlap. Defining the proportional relationship between this overlapping portion and the circumference of the first circle X4 further defines the dimensional variation trend of the front ends of the first blades 211. The front ends 217 of the first blades 211 are closer to the liquid inlet 1b, and dimensional variations of the front ends 217 have a more significant impact on the hydraulic properties of the fluid. Defining the fourth dimensional ratio range for the front ends 217 ensures that the shape and dimensions of the first blades 211 better meet the hydraulic performance requirements.

[0065] In addition, a second circle X2 is defined, and the radius of the second circle X2 is 1 mm larger than the radius of the second inner normal circle X3. On the axial projection surface of the impeller 2, the arc length of the overlapping portion of all first blades 211 and all second blades 212 with the second circle X2 accounts for 36% to 53% of the circumference of the second circle X2, which can be defined as the fifth size ratio range. Figure 4As shown, the second inner normal circle X3 is tangent to the front ends 217 of the plurality of second blades 212. When X3 is displaced 1 mm away from the center of the circle, the second circle X2 overlaps with both the first and second blades 211, 212. Defining the ratio of this overlapping portion to the circumference of the second circle X2 further defines the dimensional variation trends of the first and second blades 211, 212. Defining the fifth dimensional ratio range effectively defines the dimensions of the front ends 217 of the shorter second blades 212, ensuring a shape and size that better balances hydraulic performance and eliminates the "hump" effect.

[0066] like Figure 8 、 Figure 9 As shown, Figure 8 This is a schematic diagram of the flow-head curve of a traditional centrifugal pump in the low specific speed and small flow area; Figure 9 Schematic diagram of a flow-head curve of a centrifugal blood pump in an embodiment of the present application.

[0067] The low-specific-speed centrifugal pump is prone to a "hump" phenomenon in the small flow area, that is, the flow-pressure head curve (HQ curve) will show a trend of first rising and then falling. When the pressure head is higher than the dead-point pressure head, each pressure head will correspond to 2 flow rates. Figure 8 A dotted line is drawn horizontally at a pressure head value H, and there are two intersections with the curve. The coordinates of the two intersections are (Q1, H) and (Q2, H). That is, to achieve a pressure head value, two corresponding flow parameters will appear, making it difficult to determine whether to control according to Q1 or Q2. This will lead to unstable operation of the centrifugal pump. As mentioned above, in the HQ curve obtained by the ultra-low specific speed centrifugal blood pump in this embodiment, the "hump" is eliminated, and one pressure head value corresponds to only one flow value, such as Figure 9 As shown, this is beneficial to improving the stability of the operation of the centrifugal blood pump.

[0068] like Figure 10 、 Figure 11 As shown, Figure 10 for Figure 1 An enlarged view of the position of a single blade 21; Figure 11 for Figure 1 Schematic diagram of the structure of the middle impeller 2.

[0069] In this embodiment, the circumferential width of the blade 21 gradually increases from front to back. Here, the circumferential width of the front end 217 of the blade 21 is defined as its chamfer diameter, and the width of the rear end 218 of the blade 21 is defined as the arc length of its rear edge. In this embodiment, after the aforementioned dimensional ratios of the blade 21 are restricted, the width of the rear end 218 of the blade 21 can be further restricted to a multiple of the width of the front end 21, for example, 4 times or more. That is, compared with conventional blades in the prior art, the circumferential width difference between the front end 217 and the rear end 218 of the blade 21 in this embodiment is larger. By setting the blade 21 to be narrower at the front and wider at the rear, the circumferential spacing between adjacent blades 21 on the outlet side will be narrower, and the cross-sectional area of the flow path between adjacent blades 21 will also be smaller, which further helps to increase the slope of the HQ curve to eliminate the hump.

[0070] Furthermore, as mentioned above, the pump housing 1 in this embodiment is provided with a liquid inlet 1b at the top of the volute portion 11, and the liquid inlet 1b is connected to the inlet portion 15. In this embodiment, it is defined that, in the axial direction, the blade 21 has an upper side 213 close to the liquid inlet 1b and a lower side 214 away from the liquid inlet 1b, as shown in FIG. Figure 11 As shown, the upper side 213 and the lower side 214 are distributed along the axial direction.

[0071] For example, the circumferential width of the upper side 213 can gradually change from front to back from amm to bmm, where a has a numerical range of 0.9 to 1.1 and b has a numerical range of 6 to 8, both numerical ranges being inclusive. The circumferential width of the lower side 214 can gradually change from front to back from cmm to dmm, where c has a numerical range of 1.5 to 2 and d has a numerical range of 7 to 9. For example, the width of the upper side 213 gradually changes from 1mm to 6mm in the front-to-back direction, and the width of the lower side 214 gradually changes from 2mm to 9mm in the front-to-back direction. Regarding the width ratio of the front end 217 to the rear end 218 of the blade 21, the ratio of the upper side 213 can be approximately 8 times, and the ratio of the lower side 214 can be approximately 5 times.

[0072] In addition, in this embodiment, the upper side 213 and the lower side 214 have different widths along the circumferential direction at the same position in the front-to-back direction. The direction of the axial blade 21 toward the liquid inlet 1b is defined as upward, that is, the direction from the lower side 214 to the upper side 213 is from bottom to top. Then, from bottom to top, the width of the blade 21 along the circumferential direction is gradually reduced. At this time, both side portions of the blade 21 distributed along the circumferential direction (the first side portion 215 and the second side portion 216) form slopes. Figure 10As shown, at any position between the front end 217 and the rear end 218 of the blade 21, the width W1 of the upper side 213 is smaller than the width W2 of the lower side 214. That is, at any position between the front end 217 and the rear end 218, the width of the blade 21 gradually decreases from bottom to top. In this way, the cross-section of the blade 21 along the circumferential direction will be a trapezoidal shape with a larger bottom and a smaller top. It can be seen that the blade 21 in this embodiment is gradually narrowed from bottom to top and also from back to front.

[0073] In this embodiment, the blades 21 are arranged to taper from bottom to top to better accommodate the magnetic levitation design. That is, the impeller 2 in this embodiment can be magnetically suspended. During operation, the impeller 2 is suspended within the volute 11. The interaction between the motor's magnets and the magnets within the pump housing 1 enables the impeller 2 to rotate in a magnetically suspended state. Magnetic levitation impellers are conventional technology, and the principles of their magnetic levitation operation can be understood with reference to conventional technology (e.g., CN115040775A), which will not be discussed in detail in this embodiment. When the impeller 2 is magnetically suspended, the blades 21 are arranged to taper from bottom to top to increase the flow rate within the tip clearance flow channel. The side of the pump housing 1 where the liquid inlet 1b is provided is the top of the volute 11. The tip clearance flow channel is the gap between the blades 21 and the top of the volute 11. This creates greater downward pressure, thereby offsetting the upward axial force generated during the rotation of the impeller 2, thereby increasing the stability of the impeller 2 in the magnetic levitation system. Furthermore, in addition to increasing stability, the blades 21 can also be easily formed into a draft angle when manufactured using a mold because the blades 21 are configured to taper from bottom to top, thereby facilitating processing. Of course, the blades 21 can also have a rectangular cross-section along the circumferential direction, that is, a design with a uniform width from bottom to top.

[0074] Please continue to refer to Figure 11 , and combined with Figure 12 understand, Figure 12 for Figure 11 Magnified view of area B.

[0075] The impeller 2 in this embodiment includes a circular base plate 22, and a plurality of blades 21 are arranged on the base plate 22 along the circumferential direction. Figure 11 As shown, the blade 21 can be processed separately and installed on the chassis 22, or it can be an integrated structure with the chassis 22. Figure 12 As shown, the blade 21 includes a blade front section 21a, a blade middle section 21b, and a blade rear section 21c which are connected in sequence from front to back. The blade middle section 21b is also connected to a root 23. The root 23 and the blade middle section 21b can be an integrated structure. Figure 11The dividing line between the middle section 21b and the root 23 of the blade is indicated by a dotted line for ease of understanding. The root 23 is connected to the side surface of the chassis 22 near the liquid inlet 1b, that is, the blade 21 is arranged on the upper side surface of the chassis 22. At this time, due to the existence of the root 23, there is an axial distance between the front section 21a and the rear section 21c of the blade and the upper side surface of the chassis 22 near the liquid inlet 1b, so that a gap can be formed. Figure 12 The front notch 21d and the rear notch 21e are shown. Such arrangement can prevent the lower side of the blade 21 from colliding with the volute portion 11, thereby achieving stable suspension of the impeller.

[0076] As mentioned above, the width of the upper side 213 is set to increase from amm to bmm, and the width of the lower side 214 is set to increase from cmm to dmm. When the root 23 is set, the blade 21 can be set to be relatively thin in the axial direction, and the values of c and d can take relatively small values within their respective ranges.

[0077] like Figure 12 As shown, the front end 217 of the first blade 211 is designed to be inclined, and the front surface of the front end 217 of the first blade 211 is a slope, which has an angle with the horizontal direction. The angle α is an acute angle, which can be 40° to 50°, for example, set to 45°. As mentioned above, the blade 21 is set to be tapered from bottom to top, and a slope is formed at the front end 217 and the first side portion 215 and the second side portion 216. Here, the slope of the front surface of the front end 217 of the first blade is set to an acute angle, so that the front end 217 of the first blade 211 is set to be relatively flat and long, and the center position surrounded by multiple front ends 217 coincides with the axial projection of the liquid inlet 1b. Blood can reach this center position from the liquid inlet 1b. The front end 217 of the first blade 211 with a slope of about 45° can extend more toward the center position, so that the blood is affected by the blade 21 earlier. At the same time, it can increase the length of the blade 21 at the center position, reduce the diffusion of the flow channel, and reduce the relative speed of the blood at the liquid inlet 1b, thereby reducing the impact loss of blood on the inlet side of the blade 21. Of course, excessive extension of the front surface of the front end 217 may cause blockage of blood on the inlet side of the blade. In this embodiment, the acute angle of 40° to 50° can achieve the purpose of moderate extension. The angles of the slopes of the first side portion 215 and the second side portion 216 may also be set within this angle range.

[0078] Look again Figure 10The specification parameters of the blade 21 include the outlet angle β2 and the wrap angle θ, wherein the connection position between the rear end 218 of the blade 21 and its longer first side portion 215 is the rear end corner 2181, and the rear end corner 2181 of the blade 21 has an extension line L1 along the length direction of the blade 21. The tangent line corresponding to the outer normal circle X1 at the rear end corner 2181 is L2, and the angle between the extension line L1 and the tangent line L2 is the outlet angle β2 of the blade 21. The blade 21 in this embodiment is not arranged in a straight line, but has a certain curvature from front to back, forming a longer first side portion 215 and a shorter second side portion 216. At this time, the connection position between the front end 217 of the blade 21 and its longer first side portion 215 is the front end corner 2171. The front end corner 2171 and the center O of the base circle X are connected to obtain a first line L3, and the rear end corner 2181 and the center O of the base circle X are connected to obtain a second line L4. The angle between the first line L3 and the second line L4 is the wrap angle θ of the blade 21.

[0079] In this embodiment, the outlet angle β2 of the blade 21 can be set to 65°~70°, and the wrap angle θ of the blade 21 can be set to 90°~120°. Both the outlet angle β2 and the wrap angle θ of the blade 21 can be taken as maximum as possible to meet the hydraulic performance, but the wrap angle θ of the blade 21 should not be too large. A larger outlet angle β2 and a smaller wrap angle θ can reduce the velocity gradient on the outlet side of the impeller 2, thereby helping to reduce the shear stress on the wall of the blade 21 to reduce damage to the blood. Therefore, in order to take into account both hydraulic performance and blood compatibility, in this embodiment, the outlet angle β2 of the blade 21 is set to 65°~70°, and the wrap angle θ of the blade 21 can be set to 90°~120°. It has been verified through experiments that this angle range can better meet the hydraulic performance while taking into account blood compatibility.

[0080] The blade 21 also includes an inlet angle β1. This angle is defined by the angle between the tangent line of a circle drawn with the first connecting line L3 at the front corner 2171 and the tangent line of the blade 21 at the front corner 2171. The inlet angle β1 can be set to 20° to 25°. Experiments have shown that this angle range satisfies both hydraulic performance and hemocompatibility.

[0081] like Figure 12 As shown, the blade 21 is chamfered at the edge, that is, the position where the two side parts and the upper side 213 and the lower side 214 meet, the front end 217, the rear end 218 and the two side parts and the upper side 213 and the lower side 214 meet, are all chamfered to make the edge of the blade 21 smoother, avoid damaging the blood, and facilitate the achievement of hemolytic performance.

[0082] Look again Figure 3The volute 11 in this embodiment includes a diffusion section 12 provided on the side. After the blood flows along the spiral flow channel 1a in the volute 11, it will enter the diffusion section 12. The diffusion section 12 is located on the side of the volute 11. The diffusion section 12 is connected to the outlet 16. The volute 11 also includes a partition tongue 13. A partition tongue 13 is formed between the diffusion section 12 and the spiral flow channel 1a. When the blood flows along the spiral flow channel 1a to the diffusion section 12, a part of the fluid flows along the diffusion section 12 to the outlet 16, and the other part will enter the spiral flow channel 1a again, that is, the blood is divided into two paths by the partition tongue 13. The starting position of the diffusion section 12 is located at the position where the diffusion section 12 is tangent to the base circle X, that is, Figure 3 The position of the throat PM is shown in FIG. , and the throat PM is the starting position of the diffuser section 12 , and is also the starting position and the ending position of the spiral flow channel 1 a .

[0083] It is worth noting that in this embodiment, the spiral flow channel 1a is divided into two parts, specifically into two parts with roughly equal paths, namely the upstream section 1a1 and the downstream section 1a2. Figure 3 In the figure, the spiral flow channel 1a is divided into two parts by the extension line of the throat PM, and the lengths of the upstream section 1a1 and the downstream section 1a2 are respectively about one-half of the length of the spiral flow channel 1a. Among them, the rate of change of the flow channel cross-sectional area of the upstream section 1a1 of the spiral flow channel 1a is greater than the rate of change of the flow channel cross-sectional area of the downstream section 1a2. The flow channel cross-sectional area of the spiral flow channel of a general centrifugal pump changes linearly, and the rate of change of the flow channel cross-sectional area remains constant, while the flow channel cross-sectional area of the spiral flow channel 1a in this embodiment changes nonlinearly. The blood entering the spiral flow channel 1a includes both the blood discharged at this position on the outlet side of the impeller 2 and a part of the blood separated from the partition tongue 13 by the diffusion section 12. The separated blood and the blood thrown into the spiral flow channel 1a by the impeller 2 interact with each other, resulting in a turbulent flow field in the upstream section of the spiral flow channel 1a, such as a high-speed area. For the ultra-low specific speed centrifugal blood pump provided in this embodiment, the pump head operates under small flow conditions, and the flow rate output to the outside is smaller, so the blood circulating in the spiral flow channel 1a will increase, so the flow field in the upstream section 1a1 of the spiral flow channel 1a of the ultra-low specific speed centrifugal blood pump is more likely to be disturbed.

[0084] At this time, in this embodiment, the rate of change of the flow channel cross-sectional area of the upstream section 1a1 is set to be relatively large, and the flow channel cross-sectional area of the upstream section 1a1 increases relatively quickly. In this way, the cross-sectional area of the upstream section 1a1 (i.e., the front section) of the spiral flow channel 1a increases rapidly to ensure that the upstream section 1a1 has sufficient volume to collect blood. The larger cross-sectional area allows the two incoming flows of the upstream section 1a1 to have sufficient area for convergence, thereby effectively alleviating flow field turbulence, facilitating more stable blood pumping along the spiral flow channel 1a, and reducing the high-speed area of the upstream section 1a1. This setting is conducive to realizing low-flow applications, such as in ultra-low specific speed centrifugal blood pumps, which are suitable for infants and children or other adult patients requiring ultra-low specific speeds.

[0085] Of course, the upstream section 1a1 and the downstream section 1a2 do not necessarily have to be half of the spiral flow channel 1a. For example, the upstream section 1a1 can be one-third of the spiral flow channel 1a, and the downstream section 1a2 can be two-thirds of the spiral flow channel 1a, etc. Alternatively, the upstream section 1a1 can be one-quarter of the spiral flow channel 1a, and the downstream section 1a2 can be three-quarters of the spiral flow channel 1a, etc. This division can be specifically set according to the specific size of the spiral flow channel 1a and the flow state. In this embodiment, the upstream section 1a1 and the downstream section 1a2 each occupy approximately one-half of the length of the spiral flow channel 1a, which has a better effect on improving the flow state. It can be seen that the above-mentioned flow field turbulence is mainly caused by the confluence of blood separated by the partition tongue 13 and blood thrown out by the impeller 2. Therefore, the upstream section 1a1 only needs to include the spiral flow channel 1a near the position of the partition tongue 13.

[0086] Please refer to Figure 13 、 14 , Figure 13 These are two structural forms of the spiral flow channel 1a of the ultra-low specific speed centrifugal blood pump in the embodiment of the present application; Figure 14 for Figure 13 Enlarged view of area A in the middle.

[0087] In the figure, one structure of the spiral flow channel 1a starts from the M position and winds clockwise to the PM position of the throat. The other structure of the spiral flow channel 1a starts from the MS position and winds clockwise to the PM position of the throat. Since the spiral flow channel 1a and the cavity of the diffuser 12 are connected as one, Figure 14 It is divided by dotted lines K1 and K2 for easy understanding. When the spiral flow channel 1a starts at the M position, the cross-sectional area of the spiral flow channel 1a at the starting position is zero. S is located between P and M. When the spiral flow channel 1a starts at the MS position, the cross-sectional area of the spiral flow channel 1a at the starting position is greater than zero. It can be understood that the spiral flow channel 1a is a closed-loop flow channel, and the starting position and end position of the spiral flow channel 1a are both at the throat PM. The cross-sectional area of the end position of the spiral flow channel 1a is the cross-sectional area of the entire throat PM, and the cross-sectional area at the starting position is zero or the cross-sectional area of the MS segment.

[0088] The initial cross-sectional area of the spiral flow channel 1a being greater than zero can effectively increase the cross-sectional area of the upstream section of the spiral flow channel 1a, thereby further improving the turbulence problem in the upstream section of the spiral flow channel 1a. Figure 13 In the embodiment, the influence of the initial cross-sectional area being greater than zero is only reflected in the upstream section of the spiral flow channel 1a. However, if necessary, the influence of the initial cross-sectional area being greater than zero can be extended to the entire spiral flow channel 1a.

[0089] Of course, the cross-sectional area of the spiral flow channel 1a at the starting position cannot be too large. The cross-sectional area of the spiral flow channel at the starting position is not greater than F max , F max Calculated according to the following formula:

[0090]

[0091]

[0092] Wherein, v0 is the average flow velocity of the volute at the throat PM position, and the unit is m / s.

[0093] k3 is the speed coefficient. The value of the speed coefficient can be referred to Figure 15 understand, Figure 15 The statistical curve of domestic pumps and Stepanov curve are shown, with the horizontal axis n s For the specific speed, the Stepanov curve and the domestic pump curve have similar speed coefficient values at low specific speeds, so both can be used to determine k3. If the specific speed is high, k3 can be obtained using the Stepanov curve to ensure that the cross-section of the volute part 11 is large enough.

[0094] In addition, in the above formula, g is the acceleration due to gravity, and the unit is m / s 2 ; H is the pressure head, the unit is m; F max The maximum cross-sectional area allowed at the starting position of the spiral channel 1a, in m 2 ;Q s is the recirculation flow rate of the spiral flow channel 1a of the volute 11, unit: m 3 / s.

[0095] The area F calculated by the above formula max , is the theoretical flow area required for the blood to enter the spiral flow channel 1a for recirculation. If the area of the spiral flow channel 1a at the starting position is larger than F max , it may lead to an excessively large flow area of the volute 11, which is not conducive to forming a smooth flow field. Therefore, the area of the spiral flow channel 1a at the starting position is limited to no more than F max .

[0096] As mentioned above, the centrifugal blood pump in this embodiment has an ultra-low specific speed. For this application scenario, the inventors of this application found through flow field analysis that the flow separation of blood in the diffusion section 12 is relatively serious. Figure 3 As shown, at the position of the partition tongue 13, a portion of the blood will flow back to the spiral flow channel 1a. Based on this, when the flow rate is small, there will not be enough fluid passing through the diffuser section 12, resulting in uneven velocity distribution in the diffuser section 12. In this embodiment, in order to solve this problem, the diffuser section 12 is also set as an asymmetric diffuser section 12. The diffuser section 12 includes a first side 121 away from the partition tongue 13 and a second side 122 close to the partition tongue 13. In fact, the second side 122 also constitutes a part of the wall of the partition tongue 13. The first side 121 of the diffuser section 12 can be set to be roughly parallel to the tangent of the throat PM at the base circle X, and the second side 122 of the diffuser section 12 has an angle with the tangent parallel to the position of the throat PM, as shown in FIG. Figure 3 The figure shows a reference line L5 parallel to the tangent line at the throat PM. An angle γ is formed between the second side 122 and the reference line L5. This means that the second side 122 is tilted relative to the first side 111, resulting in a transverse cross-section of the diffuser 12 that is approximately triangular. Thus, while ensuring the size of the diffuser outlet 12a, the second side 122 is tilted as much as possible toward the baffle 13. This better aligns with the direction of fluid flow, ensuring uniform fluid distribution within the diffuser 12, avoiding a lack of fluid on the upper side of the diffuser 12, and achieving a more uniform flow field within the diffuser 12.

[0097] In addition, the length L of the diffuser section 12 can be set to not exceed the radius of the base circle X. The length L of the diffuser section 12 is the distance from the throat PM to the diffuser section outlet 12a. The inventors have discovered that the length L of the diffuser section 12 also affects the flow pattern at the septum 13. The length of the diffuser section of current centrifugal pumps is set to be relatively long, usually larger than the radius of the base circle X, so as to relatively smoothly draw out a relatively large flow of fluid. However, for centrifugal blood pumps with small flow rates, high pressure heads, and ultra-low specific speeds, a longer diffuser section 12 is not conducive to blood flow, and the blood will be significantly separated at the septum 13. Therefore, in this embodiment, the length L of the diffuser section 12 is set to be smaller than the radius of the base circle X. The radius of the base circle X is positively correlated with the length of the spiral flow channel 1a, and the length of the spiral flow channel 1a is related to the flow velocity and flow rate of the blood flowing into the diffuser section 12. Taking the radius of the base circle X as a reference, setting the length L of the diffuser section 12 to be smaller than the radius of the base circle X can better meet the pumping requirements of small flows. Experimental verification shows that setting the length L of the diffusion section 12 to be smaller than the radius of the base circle X increases the corresponding diffusion angle, which can better match the flow direction of the blood at the outlet and enable the blood to pass through the diffusion section 12 better, thereby improving the flow field near the partition tongue 13, and significantly reducing the high-pressure and low-pressure areas near the partition tongue 13.

[0098] Look again Figure 3, connect the center O of the base circle X and the end of the tongue 13 to obtain a third line ON, the third line ON and the line between the center O and the throat PM have an angle, the angle is the placement angle of the tongue 13 The inventors of this application have found that in the case of low flow, if the angle If the angle is too large, the distance between M and N will increase, the stagnant fluid will increase, and the flow separation of the fluid will be more serious. The blood flowing back to the spiral channel 1a will increase. However, if the angle is too large, the distance between M and N will increase, and the stagnant fluid will increase. Too small is not conducive to the processing of the rounded corners of the tongue 13. After comprehensive consideration of hydraulic performance and processing convenience, in this embodiment, the placement angle of the tongue 13 is set to Set it to 5°~15°, which improves flow separation and facilitates processing.

[0099] In this embodiment, the multiple blades 21 are described using an example of an alternating arrangement of long and short blades. It is understood that the multiple blades 21 may also be of equal length, for example, all being second blades 212. With the alternating arrangement of long and short blades, the first blade 211, which is the longer blade, is positioned closer to the liquid inlet 1b without interfering with the second blade 212, thereby improving hydraulic performance.

[0100] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core ideas of this application. It should be noted that for those skilled in the art, without departing from the principles of this application, various improvements and modifications can be made to this application, and such improvements and modifications also fall within the scope of protection of the claims of this application.

Claims

1. A centrifugal blood pump with ultra-low specific speed, characterized in that: The impeller comprises a volute portion and an impeller, wherein the impeller is located in the volute portion and comprises a plurality of blades distributed along the circumferential direction, wherein one end of the blade close to the center of the base circle of the volute portion is a front end and the other end is a rear end, and the rear ends of the blades are all located on the same outer normal circle; On the projection surface of the impeller along the axial direction, the arc length of the rear ends of all the blades along the circumferential direction accounts for 28% to 54% of the circumference of the outer normal circle; and the projection area of all the blades along the axial direction is a first area, the area of the outer normal circle is a second area, and the first area accounts for 26% to 47% of the second area.

2. The ultra-low specific speed centrifugal blood pump according to claim 1, characterized in that: The specific speed of the centrifugal blood pump is not higher than 20.

3. The ultra-low specific speed centrifugal blood pump according to claim 1, characterized in that: The blades include a first blade and a second blade, the length of the first blade is greater than that of the second blade, and the first blade and the second blade are arranged alternately along the circumferential direction; the front ends of all the first blades are located on the same first inner normal circle, and the front ends of all the second blades are located on the same second inner normal circle; on the projection surface of the impeller along the axial direction, the arc length of the overlapping part of all the first blades and the second inner normal circle accounts for 22% to 34% of the circumference of the second inner normal circle.

4. The ultra-low specific speed centrifugal blood pump according to claim 3, characterized in that: A first circle is defined, the radius of which is 1 mm larger than the radius of the first inner normal circle. On the projection surface of the impeller along the axial direction, the arc length of the overlapping portion of all the first blades and the first circle accounts for 39% to 46% of the circumference of the first circle.

5. The ultra-low specific speed centrifugal blood pump according to claim 4, characterized in that: A second circle is defined, the radius of which is 1 mm larger than the radius of the second inner normal circle; on the projection surface of the impeller along the axial direction, the arc length of the overlapping parts of all the first blades and all the second blades with the second circle accounts for 36% to 53% of the circumference of the second circle.

6. The ultra-low specific speed centrifugal blood pump according to any one of claims 1 to 5, characterized in that: The volute portion is provided with a liquid inlet, and the blade has an upper side axially close to the liquid inlet and a lower side away from the liquid inlet; from bottom to top, the width of the blade along the circumferential direction is gradually reduced.

7. The ultra-low specific speed centrifugal blood pump according to claim 6, characterized in that: The circumferential width of the upper side gradually changes from amm to bmm in the direction from the front end to the rear end, wherein the numerical range of a is 0.9 to 1.1, and the numerical range of b is 6 to 8; the width of the lower side gradually changes from cmm to dmm in the direction from the front end to the rear end, wherein the numerical range of c is 1.5 to 2, and the numerical range of d is 7 to 9.

8. The ultra-low specific speed centrifugal blood pump according to any one of claims 1 to 5, characterized in that: The impeller includes a circular chassis, and a plurality of blades are arranged circumferentially on the chassis. The blades include a blade front section, a blade middle section, and a blade rear section that are connected sequentially from the inside to the outside. The blade middle section is connected to a side of the chassis close to the liquid inlet. The blade front section and the blade rear section are away from the side of the liquid inlet, and are axially spaced from the side of the chassis close to the liquid inlet.

9. The ultra-low specific speed centrifugal blood pump according to any one of claims 1 to 5, characterized in that: The front end surface of at least one of the blades is a slope surface, the slope surface forms an angle with a transverse direction, the angle is an acute angle, and the transverse direction is perpendicular to the axial direction.

10. The ultra-low specific speed centrifugal blood pump according to any one of claims 1 to 5, characterized in that: The outlet angle, wrap angle, and inlet angle of the blades satisfy at least one of the following: The outlet angle is 65° to 70°; The wrap angle of the blade is 90° to 120°; The inlet angle is 20° to 25°.

Images