C-shaped circumferential bending stator of pump-jet propeller capable of reducing noise and improving efficiency and design method of C-shaped circumferential bending stator

Abstract

The invention discloses a noise reduction and efficiency improvement pump jet propeller C-shaped circumferential bending stator and a design method, and the method comprises the steps: building a hull-rudder-pump jet propeller calculation model, changing the phase angles theta of the stator at different radiuses, and preliminarily determining the lateral slope distance distribution parameter ai of the C-shaped circumferential bending stator; after a pump-jet propeller provided with a straight stator and a C-shaped circumferential bending stator is arranged in an underwater vehicle, self-propulsion test simulation is carried out, and the thrust and torque of each component of the propellers when the two different propellers are at self-propulsion points are monitored; adjusting a slant distance distribution parameter ai of a bent stator side to obtain different distribution forms of circumferential phase angles of the stator; adjusting geometric attack angles alpha of sections at different radiuses of the stator blade, and selecting the most suitable distribution form of the geometric attack angles alpha as an optimization result; and determining the most suitable chordwise distribution form of the blade section as an optimization result. According to the invention, the bearing force, hydrodynamic noise and structural vibration noise of the submarine propeller are reduced only through the lateral inclination change of the stator blades.

Description

Technical Field

[0001] The present invention belongs to the field of underwater vehicle propulsion, and more specifically, relates to a C-shaped circumferentially curved stator of a pump-jet propulsion system for reducing noise and increasing efficiency and a design method thereof. Background Art

[0002] Pump-jet propulsion is an underwater propulsion device composed of a duct, a rotor, and a stator. It has the advantages of delaying the occurrence of cavitation, reducing the radiation noise of underwater navigation bodies, and improving propulsion efficiency. It has been widely used in various underwater navigation bodies, ranging from nuclear submarines to unmanned UUVs. Pump-jet propulsion is generally installed at the tail of the navigation body, and a stern rudder and other appendages are usually arranged in front of it. When the navigation body is sailing underwater, the fluid flows through the stern rudder and other appendages, forming a complex non-uniform wake field at the stern of the hull. The uneven distribution of the stern flow field on the rotor disk of the pump-jet propulsion will cause periodic changes in the rotor surface pressure, thereby generating low-frequency line spectrum noise, while the turbulent pulsation of the flow field at the stern of the hull will cause irregular pulsation of the rotor surface pressure, thereby generating low-frequency broadband noise. In addition to the radiation noise, when the rotor works in the non-uniform flow field at the stern of the hull, the unsteady bearing force it generates will act on the hull through the bearing, causing the vibration of the hull structure to generate vibration noise. Whether it is low-frequency line spectrum noise, low-frequency broadband noise or hull structure vibration noise caused by rotor bearing force, they are all closely related to the unevenness of the flow field at the rotor disk surface. Therefore, improving the flow field at the rotor disk surface by optimizing the stator structure is a direct and effective way to reduce submarine noise.

[0003] As one of the important components of the pump-jet propulsor, the stator blades in the front-stator pump-jet propulsor generally have an asymmetric profile and form a certain geometric angle of attack with the axis, which can provide pre-selected flow and improve the uniformity of the flow field. However, it is generally a structure without side tilt, and the effect of improving the inflow by only adjusting the blade profile shape and the geometric angle of attack is very limited. On the rotor inlet surface, the phase angles corresponding to the peak values ​​of the accompanying flow at each radius are basically consistent, resulting in a large bearing force when the rotor blades rotate. Although the bearing force of the rotor can be reduced by increasing the side tilt of the rotor blades, due to strength limitations, the side tilt angle of the rotor cannot be too large, resulting in a large bearing force when the rotor rotates.

[0004] Considering that the basic reason for the vibration and noise reduction of the large skew propeller is that there is a large phase difference in the space of the profiles at each radius of the large skew propeller, and the phase angle corresponding to the wake peak of the submarine wake at each radius is basically consistent, when the propeller is working, there is a large difference between the spatial phase distribution of the profiles at each radius and the spatial phase distribution of the wake peak at each radius. This difference in phase distribution can be called the orthogonality (or mismatch) between the two. This orthogonality will cause a certain time difference in the corresponding moment when each radius profile enters the wake peak area, that is, there is asynchrony in the time when each blade profile enters the wake peak area. Since there is asynchrony in the time when each radius profile of the large skew propeller enters the wake peak area, the load of each radius profile cannot reach the maximum value or the minimum value at the same time, so that the maximum value of the overall load of the blade during the rotation process can be reduced, and the minimum value of the overall load of the blade can be increased, so that the amplitude of the load fluctuation of the propeller blade during the rotation process is small. The larger the propeller skew value, the greater the phase positive intersection between each radius profile and the wake peak at each radius, and the time asynchronism of each radius profile entering the wake peak area will also increase, and the fluctuation amplitude of the entire blade load over time will be smaller. However, excessive rotor skew will cause the stiffness of the rotor blades to decrease. When the rotor is running, the rotor blade tip will vibrate, which will increase the noise of the pump-jet propulsion. Therefore, without increasing the rotor skew, the phase distribution of the wake peak at each radius of the rotor disk can be directly adjusted by changing the rotor inflow, so as to increase the orthogonality with the propeller profile phase distribution, thereby reducing the exciting force of the pump-jet propulsion and reducing the propeller noise.

[0005] The most effective and simplest way to change the inflow of the rotor in a pump-jet propulsor is to change the geometric shape of the front stator of the pump-jet propulsor, set a larger geometric angle of attack and camber at the root of the stator blade, and set a smaller geometric angle of attack and camber at the tip of the blade, so as to expand the difference in the phase of the peak value of the wake flow at each radius of the rotor disk, thereby increasing the orthogonality with the phase distribution of the propeller profile. In order to increase the orthogonality of the spatial phase distribution of the peak value of the wake flow at each radius of the rotor disk and the spatial phase distribution of each radial section of the rotor, it is usually achieved by increasing the geometric angle of attack and camber of the small radius section of the stator, but a larger angle of attack and camber will lead to a larger resistance and torque of the stator itself, which will then lead to a lower overall efficiency of the pump-jet propulsor and a larger torque imbalance of the propeller. The circumferentially curved stator in the present invention adjusts the side inclination angle of the blade section at each radius to achieve the purpose of increasing the orthogonality of the spatial phase distribution of the wake peak at each radius of the rotor disk surface and the spatial phase distribution of each radius section of the rotor under the premise of a smaller stator attack angle and camber distribution. This can not only greatly reduce the exciting force and low-frequency line spectrum noise of the pump-jet propulsor rotor.

[0006] In addition, when the effect of the rotor is not considered, after the fluid passes through the stator blades in the duct of the pump-jet propulsor, a certain degree of pre-swirl will be generated in the opposite direction of the rotor's rotation, so that there is a certain circumferential velocity component in the flow field at each radius in the stator wake. Since the blades are in a rotating state when the rotor is working, the rotor will cause the wake to produce axial induced velocity and circumferential induced velocity. The kinetic energy formed by the axial induced velocity and circumferential induced velocity in the wake is lost energy. The reverse pre-swirl flow in the rotor inlet flow offsets the circumferential velocity component of the induced velocity to a certain extent, reducing the circumferential velocity component in the rotor wake, which is beneficial to reducing the kinetic energy loss caused by the circumferential velocity in the rotor wake and improving the propulsion efficiency of the pump-jet propulsor. Summary of the invention

[0007] In response to the above defects or improvement needs of the prior art, the present invention provides a C-shaped circumferentially curved stator and design method for a pump-jet propulsion system with reduced noise and increased efficiency. The circumferentially curved stator in the present invention can make the reverse pre-rotation effect more prominent. Under the premise that the stator torque remains unchanged, the geometric angle of attack and the curvature of the stator are smaller than those of conventional stators, and the resistance of the stator is reduced, thereby further improving the propulsion efficiency of the pump-jet propulsion system.

[0008] To achieve the above object, according to a first aspect of the present invention, a design method for a C-shaped circumferentially curved stator of a pump-jet propulsor with noise reduction and efficiency improvement is provided, comprising:

[0009] S100: Establish a hull-rudder-pump-jet propulsion calculation model to determine the rotation speed of the pump-jet propulsion rotor when the vehicle reaches the self-navigation point. Then, based on the distribution of the phase angle θ° of the rotor at different radius sections, on the basis of the conventional straight stator, by changing the phase angle θ of the stator at different radii, preliminarily determine the side slant distance distribution parameter a of the pump-jet propulsion "C" circumferential curved stator opposite to the rotor tilt direction. i ;

[0010] S200: Pump-jet propulsors with straight stators and C-shaped circumferentially curved stators were placed in underwater vehicles for self-propulsion test simulations. The thrust and torque of each component of the two propulsion units were monitored at the self-propulsion point. The propulsion efficiency η0 and unsteady force amplitude of the two propulsion units were obtained by data processing. In order to analyze the influence of "C" shaped circumferentially curved stator on the propulsion efficiency and unsteady force of pump-jet propulsor;

[0011] S300: Based on the circumferentially curved stator of step S200, the distribution characteristics of the flow field between the stator trailing edge in the duct and the rotor disk surface in the preliminary scheme are analyzed to adjust the side slant distance distribution parameter a of the "C"-shaped circumferentially curved stator. i, increase the positive intersection of the peak circumferential phase distribution characteristics of the flow field between the stator and the rotor at each radius and the profile phase distribution characteristics of the rotor blade at each radius, analyze the influence of different linear distributions of the stator circumferential phase angle on the propulsion efficiency and unsteady force of the pump-jet propulsor, and obtain different distribution forms of the stator circumferential phase angle θ;

[0012] S400: Based on the optimization result of step S300, the geometric angle of attack α of the cross section at different radii of the stator blade and the chord-wise distribution of the stator blade cross section are optimized in sequence, thereby completing the design of the C-shaped circumferentially curved stator of the pump-jet propulsor.

[0013] As a further preferred embodiment, in the flow field behind the trailing edge of the circumferentially curved stator, the phases of high wake areas at different radii are inconsistent;

[0014] From the inner radius to the outer radius of the circumferentially curved stator, the variation trend of the phase angle in the high wake region is opposite to the variation trend of the rotor side skew angle.

[0015] As a further preferred embodiment, the skew value of each radial section of the circumferentially curved stator is distributed in a power function form with the radius, that is:

[0016]

[0017] In the formula, They respectively represent the dimensionless quantities of the stator section inclination value, the section radius, and the stator hub radius after being dimensionally non-dimensionalized by the propeller blade tip radius.

[0018] As a further preference, the circumferential phase angle of the circumferentially curved stator gradually increases in absolute value in the clockwise direction from the blade root to the blade tip as the radius increases, and gradually decreases with the counterclockwise direction being positive, and reaches a negative peak value at the stator blade tip section.

[0019] As further preferred, step S400 includes:

[0020] (401) Based on the optimization result of step S300, the geometric angle of attack α of the cross section at different radii of the stator blade is adjusted to obtain the influence of the distribution form of the radial geometric angle of attack α on the propulsion efficiency and unsteady force of the pump-jet propulsor, and the increase in the propulsion efficiency of the pump-jet propulsor and the reduction in the amplitude of the unsteady force are comprehensively considered to select the most suitable distribution form of the geometric angle of attack α as the optimization result;

[0021] (402) Based on the optimization result of step (401), the chord-wise distribution form of the stator blade profile is changed to obtain the influence of the chord-wise distribution form of the blade profile on the propulsion efficiency and unsteady force of the pump-jet propulsion system. The increase in the propulsion efficiency of the pump-jet propulsion system and the reduction in the amplitude of the unsteady force are comprehensively considered, and the most suitable chord-wise distribution form of the blade profile is selected as the optimization result.

[0022] As a further preferred embodiment, the propulsion efficiency η of the pump-jet propulsion system is:

[0023]

[0024] Where n is the propeller speed, Q is the rotor torque, R0 is the towing resistance without pump-jet propulsion, F is the pump-jet-hull force after the pump-jet propulsion is installed, and V is S is a given incoming flow velocity.

[0025] According to another aspect of the present invention, there is also provided a C-shaped circumferentially curved stator for a pump-jet propulsion system for reducing noise and increasing efficiency, which is implemented by a design method for a C-shaped circumferentially curved stator for a pump-jet propulsion system using any embodiment or a combination of multiple embodiments as described above.

[0026] As a further preference, the stator has a skew form opposite to the skew direction of the rotor, and from the stator blade root to the blade tip, as the radius increases, the circumferential phase angle gradually increases in absolute value in the clockwise direction, with the counterclockwise direction being positive, and the circumferential phase angle gradually decreases, and reaches a negative peak value at the stator blade tip section.

[0027] As a further preferred embodiment, the skew value of each radial section of the circumferentially curved stator is distributed in a power function form with the radius, that is:

[0028]

[0029] In the formula, They respectively represent the dimensionless quantities of the stator section inclination value, the section radius, and the stator hub radius after being dimensionally non-dimensionalized by the propeller blade tip radius.

[0030] According to another aspect of the present invention, there is also provided a pump-jet propulsion system with reduced noise and increased efficiency, comprising a circumferentially curved stator implemented by a design method for a C-shaped circumferentially curved stator of a pump-jet propulsion system according to any embodiment or a combination of multiple embodiments as described above, and a rotor matching the stator.

[0031] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0032] 1. The present invention uses a "C"-shaped circumferentially curved stator so that the phases of high wake areas at different radii in the flow field behind the stator trailing edge are inconsistent, and the change trend of the phase angle of the high wake area from the inner radius to the outer radius is opposite to the change trend of the rotor side skew angle. The distribution form of the peak phase angle of the wake at each radius is highly orthogonal to the distribution form of the rotor side skew angle, thereby achieving the purpose of reducing the bearing force, hydrodynamic noise and structural vibration noise of the submarine propeller only by changing the side skew of the stator blades.

[0033] 2. The design optimization method of the present application changes the spatial distribution of the flow field at the rotor disk surface, which is equivalent to increasing the side tilt angle of the propeller, so that the phase angle of the high wake area at each radius in the rotor disk surface inlet flow behind the stator trailing edge is favorably changed, thereby reducing the rotor structure vibration noise and flow noise; at the same time, calculation analysis also shows that when the circumferentially curved stator reaches the same reverse torque as the rotor torque value, the stator resistance is smaller than the straight stator resistance. Therefore, the circumferentially curved stator can provide pre-swirl flow for the rotor with less resistance, thereby improving the propulsion efficiency of the pump-jet propulsion and realizing efficient propulsion of the vehicle.

[0034] 3. According to the design method of the present invention, the non-uniform incoming flow forms a pre-rotation state opposite to the rotation direction of the rotor through the stator, and the phases of the high wake zones at different radii are inconsistent. From the inner radius to the outer radius, the change trend of the phase angle of the high wake zone is opposite to the change trend of the phase (side tilt angle) of each radial section of the rotor. The orthogonality of the distribution characteristics of the circumferential phase angle of the peak wake of the stator wake field with the radius and the distribution characteristics of the phase angle of the rotor blade section with the radius is increased, the time difference of the corresponding moments when each radial section of the rotor enters the wake peak area is increased, and the time asynchronism of each blade section entering the wake peak area is increased.

[0035] 4. In the method of the present invention, the phase distribution difference of the curves of the load of each radius section changing with time or with the rotation angle of the rotor is greater, the time difference corresponding to the peak value of the curve of the load of each radius section changing with time is greater, and after the loads of each radius section are superimposed to form the overall load of a single blade, the fluctuation of the load of the entire blade changing with time will be smoother and the fluctuation amplitude will be smaller, thereby making the amplitude of the load fluctuation of the pump-jet propulsion rotor during rotation smaller, that is, making the bearing force during the rotation of the rotor smaller. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the conventional straight stator geometry;

[0037] Figure 2 A geometrical schematic diagram of a pump-jet propeller equipped with a C-shaped circumferentially curved stator for reducing noise and increasing efficiency according to an embodiment of the present invention;

[0038] Figure 3 A geometrical schematic diagram of a C-shaped circumferentially bent stator according to an embodiment of the present invention;

[0039] Figure 4 The geometric comparison diagram of two stators: a C-shaped circumferentially curved stator and a conventional straight stator;

[0040] Figure 5 Phase angle distribution diagram of rotor and two stators

[0041] Figure 6 The axial velocity distribution cloud diagram of the rotor inlet surface;

[0042] Figure 7 It is the circumferential velocity distribution cloud diagram of the rotor inlet surface;

[0043] Figure 8 Comparison of rotor axial force of pump-jet propulsors with different stators;

[0044] Fig. 9 Comparison of rotor lateral forces of pump-jet propulsors with different stators;

[0045] Fig.10 Comparison of vertical force on rotor of pump-jet propulsors with different stators;

[0046] Fig.11 Comparison of rotor axial torque of pump-jet propulsors with different stators;

[0047] Fig.12 Comparison of rotor lateral torque of pump-jet propulsors with different stators;

[0048] Fig.13 Comparison of vertical torque of rotor of pump-jet thruster with different stators;

[0049] Fig.14 The amplitude diagram of the unsteady forces in different directions of the rotor of different stator pump-jet thrusters at different blade frequencies;

[0050] Fig.15 The amplitude diagram of the unsteady torque of the rotor of different stators of pump-jet thrusters in different blade frequencies;

[0051] Fig.16 The present invention is a design flow chart of a method for designing a C-shaped circumferentially curved stator for a pump-jet propulsor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0053] like Figure 1As shown, an embodiment of the present invention provides a C-shaped circumferentially curved stator for a pump-jet propulsor with noise reduction and efficiency improvement. The circumferentially curved stator is based on a conventional straight stator of a pump-jet propulsor and, according to the characteristics of the rotor rotation direction and the rotor skew distribution with the radius, appropriately changes the stator profile line shape and skew angle to cause pre-rotation of the fluid passing through the stator, while increasing the phase difference of the circumferential phase angle of the peak wake flow at different radii in the stator wake, thereby increasing the orthogonality of the distribution characteristics of the circumferential phase angle of the peak wake flow at the rotor disk surface with the radius and the distribution characteristics of the rotor blade profile phase angle with the radius. That is, the non-uniform incoming flow forms a pre-rotation state opposite to the rotation direction of the rotor through the stator, and the phases of the high wake zones at different radii are inconsistent. From the inner radius to the outer radius, the change trend of the phase angle of the high wake zone is opposite to the change trend of the phase (side tilt angle) of each radial section of the rotor. The orthogonality of the distribution characteristics of the circumferential phase angle of the wake peak of the stator wake field with the radius and the distribution characteristics of the phase angle of the rotor blade section with the radius is increased, so that the time difference of the corresponding moments when each radial section of the rotor enters the peak wake area is increased, and the time asynchronism of each blade section entering the peak wake area is increased. The phase distribution of the change curves of the load of each radial section with time (or with the rotor rotation angle) is more different, and the time difference corresponding to the peak of the load change curve of each radial section with time is larger. After the loads of each radial section are superimposed to form the overall load of a single blade, the fluctuation of the entire blade load with time will be smoother and the fluctuation amplitude will be smaller, so that the amplitude of the load fluctuation of the pump-jet propulsor rotor during rotation is smaller, that is, the bearing force of the rotor during rotation is smaller. The circumferentially curved stator makes the phase distribution of the load variation curves of each section of the rotor blade greater than that of the time. The radiated noise sound pressure curves caused by the load fluctuations of each section will also show a large phase difference, and the hydrodynamic line spectrum noise sound pressure level of the entire rotor will also decrease accordingly. The reduction of the rotor's bearing force will also reduce the structural vibration noise caused by the bearing force. Therefore, the circumferentially curved stator can achieve the purpose of reducing the bearing force, line spectrum radiation noise and structural vibration noise of the submarine propulsion system and improving the propulsion efficiency of the pump-jet propulsion system simply by changing the skew distribution of the stator blades.

[0054] Taking the right-hand skew rotor as an example, looking from the stern to the bow, the angular position at 12 o'clock is 0°, and the counterclockwise direction is the positive direction of the phase angle, that is, the angular position corresponding to 3 o'clock is -90°, and the corresponding angular position at 9 o'clock is 90°. The circumferential phase angle of the rotor blade at the root section is generally small. As the radius increases, the circumferential phase angle generally increases in the clockwise direction first. At a certain radius in the middle, the circumferential phase angle reaches a negative maximum value (the circumferential phase angle is minimum). Then, as the radius increases, the circumferential phase angle gradually increases in the counterclockwise direction. At the blade tip section, the circumferential phase angle reaches a positive maximum value (the circumferential phase angle is maximum). Since the absolute value of the maximum circumferential phase angle is generally significantly greater than the absolute value of the minimum circumferential phase angle, the circumferential phase angle of the rotor blade generally presents a counterclockwise characteristic. During the rotation of the rotor, the skew distribution characteristics of the rotor sections at each radius make the rotor sections at each radius always have different circumferential phase angles. From the section with the smallest skew to the blade tip, as the section radius increases, the circumferential phase angle becomes smaller. Considering that the unsteady load on the rotor blades is mainly concentrated above the middle radius, and the load below the middle radius is relatively small, it is only necessary to control the stator wake to show that the circumferential phase angle of the peak value of the wake at each radius increases with the increase of the radius.

[0055] In view of the skew distribution characteristics of the right-handed skew rotor, the stator described in the present application has a skew form opposite to the skew direction of the rotor. From the stator blade root to the blade tip, as the radius increases, the circumferential phase angle gradually increases in absolute value in the clockwise direction, and the circumferential phase angle gradually decreases with the counterclockwise direction as positive. At the stator blade tip section, the circumferential phase angle reaches a negative peak. Since the circumferential phase angle of the stator wake peak at each radius is directly related to the circumferential phase angle of the stator section, the distribution form of the circumferential phase angle of each radius section of the stator determines the distribution form of the circumferential phase angle of the stator wake peak at each radius. Since the circumferential phase angle of each radius section of the stator decreases with the increase of the radius and drops to a negative peak at the blade tip, the circumferential phase angle of the stator wake peak also decreases with the increase of the radius. Contrary to the trend of the phase angle of each rotor section with the radius, the phase distribution of each radius section of the rotor always shows a large orthogonality with the phase distribution of the stator wake peak. When the blade root section enters the wake peak area of ​​the stator wake field, other sections still have a large phase difference with the wake peak area at the corresponding radius, that is, the radius of other sections is in the area with relatively low wake values. During the rotation of the rotor blades, the load fluctuation amplitude of each radius section of the rotor becomes smaller over time, thereby reducing the rotor exciting force, hydrodynamic noise and structural vibration noise.

[0056] The stator described in the present application is in a circumferentially curved form, and taking stator No. 1 at the 12 o'clock direction as an example, the side slope value (i.e., side slope distance, not side slope angle) of each radial section of the circumferentially curved stator is distributed in a power function form with the radius, i.e. In the formula They represent the dimensionless quantities of the stator section skew value, section radius, and stator hub radius after being dimensionlessized by the propeller blade tip radius. The highest power n can be an integer greater than 1, and n is generally taken as 2. In addition, a0 is generally taken as 0, that is, the skew value at the stator blade root is 0.

[0057] The present application also provides a design method for a C-shaped circumferentially curved stator of a pump-jet propulsor with noise reduction and efficiency improvement, comprising the following steps:

[0058] (1) A hull-rudder-pump-jet propulsion calculation model was established. The rotation speed of the pump-jet propulsion rotor was determined based on the CFD method when the vehicle reached the self-propulsion point. Based on the phase angle θ of the rotor at different radii, the side slant distance distribution parameter a of the circumferential curved stator of the pump-jet propulsion propulsion in the opposite direction of the rotor tilt was preliminarily determined by changing the phase angle θ based on the original straight stator. i ;

[0059] (2) Based on the CFD method, the pump-jet propulsors with straight stators and circumferentially curved stators were placed in underwater vehicles and subjected to self-propulsion test simulations. The thrust and torque of each component of the two propulsion units were monitored at the self-propulsion point. The propulsion efficiency η0 and the unsteady force amplitude of the two propulsion units were obtained by data processing. Thus, the influence of the circumferentially bent stator on the propulsion efficiency and unsteady force of the pump-jet propulsor is analyzed;

[0060] (3) Based on the circumferentially curved stator in step (2), by analyzing the distribution characteristics of the flow field between the stator trailing edge in the duct and the rotor disk surface in the preliminary scheme, the slant distance distribution parameter a toward the curved stator side is adjusted. i , thereby increasing the positive intersection of the peak circumferential phase distribution characteristics of the flow field between the stator and the rotor at each radius and the cross-sectional phase distribution characteristics of the rotor blade at each radius, analyzing the influence of different linear distributions of the stator circumferential phase angle on the propulsion efficiency and unsteady force of the pump-jet propulsor, and obtaining different distribution forms of the stator circumferential phase angle (if It is only necessary to determine the influence of a1 and a2) on the propulsion efficiency and unsteady force of the pump-jet propulsion system, and select the most suitable stator skew distribution form as the optimization result by considering the increment of the propulsion efficiency of the pump-jet propulsion system and the reduction of the amplitude of the unsteady force.

[0061] (4) Based on the optimization result of step (3), the geometric angle of attack α (the angle between the chord line of the blade section and the axis) of the cross section at different radii of the stator blade is adjusted to obtain the influence of the distribution form of the radial geometric angle of attack α on the propulsion efficiency and unsteady force of the pump-jet propulsor. The increase in the propulsion efficiency of the pump-jet propulsor and the reduction in the amplitude of the unsteady force are comprehensively considered, and the most suitable distribution form of the geometric angle of attack α is selected as the optimization result;

[0062] (5) Based on the optimization result of step (4), the chord-wise distribution of the stator blade profile is changed to obtain the influence of the chord-wise distribution of the blade profile on the propulsion efficiency and unsteady force of the pump-jet propulsor. The increase in the propulsion efficiency of the pump-jet propulsor and the reduction in the amplitude of the unsteady force are comprehensively considered, and the most suitable chord-wise distribution of the blade profile is selected as the optimization result.

[0063] like Figure 1 As shown, the stator has 17 blades and the rotor has 7 blades. The calculation coordinate system adopts the Cartesian coordinate system, follows the right-hand rule, takes the center of the pump-jet propulsor rotor disk as the coordinate origin, the positive direction of the x-axis points from the bow to the stern, the positive direction of the y-axis points to the starboard side of the hull, and the z-axis is vertically upward.

[0064] After the incoming flow passes through the stern rudder, an uneven incoming flow is formed. The incoming flow flows into the duct and reaches the rotor through the stator blades. Although the uneven incoming flow is improved to a certain extent under the action of the stator, it will still cause the rotor to produce large structural vibration noise and flow noise. In addition, since the angle of attack formed by the incoming flow and the rotor disk is too small, the circumferential velocity component of the flow field at the rotor disk accounts for a small proportion, resulting in a large circumferential induced velocity in the propeller wake and a loss of some circumferential energy.

[0065] In order to solve the above problems, the present application proposes a circumferentially curved stator for pump-jet propulsion with noise reduction and efficiency improvement. Figure 2 As shown in the figure, based on the characteristics of the rotor rotation direction and the rotor skew distribution with the radius, the stator profile and circumferential phase angle are appropriately changed to obtain the circumferentially bent stator (as shown in the figure). Figure 3 As shown in the figure), the two stator geometries are compared. Figure 4 As shown, the circumferential phase angle distribution of the two stators in the rotor domain is as follows Figure 5 This design makes the uneven incoming flow form a pre-swirl state opposite to the rotor rotation direction after passing through the stator. The spatial distribution of the pre-swirl flow makes the phase angle of the high wake area of ​​each radial section of the blade in the stator wake field change favorably, which is beneficial to reduce the bearing force formed by the rotor operation, thereby reducing the structural vibration noise of the rotor. At the same time, due to the change of the phase angle, the flow noise caused by the blade pressure pulsation will also be reduced, thereby improving the submarine's stealth performance.

[0066] In addition, when the pre-swirling flow reaches the rotor disk, the proportion of the circumferential velocity component of the fluid increases and can be better absorbed and utilized by the rotor. The circumferential energy loss in the incoming flow is reduced, the rotor can provide greater thrust, the speed required for the vehicle to propel itself is reduced, and the propulsion efficiency of the thruster is improved, achieving the purpose of increasing efficiency.

[0067] In order to analyze the propulsion performance of pump-jet propulsion with different stators, it is necessary to conduct a self-propulsion test of the vehicle model. This application uses the CFD unsteady calculation method to perform numerical calculations on underwater unmanned vehicles. A hull-rudder-pump-jet propulsion coupling model is established. At a given incoming flow velocity V S The self-propulsion test simulation of the underwater unmanned vehicle is carried out under the working conditions of the speed n, and the combined force F of the hull-pump-jet propulsion and the rotor torque Q are obtained. In addition, before calculating the propulsion efficiency, it is also necessary to obtain the towing resistance R0 of the underwater unmanned vehicle without the pump-jet propulsion. Finally, the obtained data are summarized as shown in Table 1.

[0068] Table 1 Comparison of underwater hydrodynamic parameters in self-propelled state

[0069]

[0070] The towing resistance without pump-jet propulsion is denoted as R0, and the pump-jet-hull force after the pump-jet propulsion is installed is denoted as F. The propulsion efficiency η can be calculated using formula (1).

[0071]

[0072] Where n is the propeller speed and Q is the rotor torque.

[0073] Table 2 Propulsion efficiency comparison

[0074] Stator type η Conventional straight stator 0.7125 Circumferentially bent stator 0.7317

[0075] It can be concluded from Table 1 and Table 2 that the pump-jet propeller with a circumferentially curved stator has a greater pump-jet-hull force and rotor torque than the pump-jet propeller with a conventional straight stator under the same speed and rotation speed conditions. At this time, the efficiency η increases by 2.70%. When the thrust and resistance are balanced, when the underwater unmanned vehicle reaches the self-propulsion point at the same speed, the speed n required by the circumferentially curved stator solution is less than the speed n required by the conventional straight stator solution. Compared with the conventional straight stator solution, the propulsion efficiency of the circumferentially curved stator solution will be further increased.

[0076] Figure 6 and Figure 7 is the velocity distribution cloud diagram of the stator wake flow field, given by Figure 6 and Figure 7It can be seen that under the action of the circumferentially curved stator, the peak phase of the stator wake with the circumferentially curved stator is opposite to the change trend of the phase angle of each rotor section with the radius, and the phase distribution of each rotor radius section always shows a large orthogonality with the phase distribution of the stator wake peak. When the rotor blade root section enters the peak wake area of ​​the stator wake field, other sections still have a large phase difference with the peak wake area at the corresponding radius, that is, the radius of other sections is in the area with relatively low wake values. During the rotation of the rotor blades, the fluctuation amplitude of the load of each rotor radius section becomes smaller over time, thereby reducing the rotor excitation force, hydrodynamic noise and structural vibration noise.

[0077] The unsteady forces in all directions of the pump-jet propulsor rotor under the self-propulsion state of different stator schemes are monitored separately. In the simulation, the rotor rotates 1° per unit time step. After the calculation is stable, the data results within one rotation cycle of the rotor are taken for comparison, such as Figures 8 to 13 shown.

[0078] After Fourier transforming the above calculation results, the frequency domain curve within a rotation period is obtained. The amplitude results of the first three solution frequencies are as follows: Figure 14 to Figure 15 As shown, it can be seen that the amplitudes of the unsteady force and unsteady torque of the rotor in one rotation cycle both reach the maximum value at the first-order blade frequency. The specific amplitude comparisons of the first-order blade frequency are shown in Tables 3 and 4 below.

[0079] Table 3 Comparison of the unsteady bearing force amplitude of pump-jet propulsor rotor with different stators

[0080] unsteady force frequency Conventional straight stator Circumferentially bent stator Rate of change Axial force First-order leaf frequency 1.1446 0.9044 20.99％ Lateral force First-order leaf frequency 1.6770 0.8152 51.39％ vertical force First-order leaf frequency 2.0165 1.5763 21.83％

[0081] Table 4 Comparison of unsteady torque amplitude of pump-jet propulsor rotor with different stators

[0082] Unsteady torque frequency Conventional straight stator Circumferentially bent stator Rate of change Axial torque First-order leaf frequency 0.0399 0.0309 22.71％ Lateral torque First-order leaf frequency 0.1271 0.0633 50.24％ Vertical torque First-order leaf frequency 0.1553 0.1173 24.45％

[0083] By comparing the unsteady force and unsteady torque amplitudes of the pump-jet propulsor rotors with two stator schemes, it is found that the unsteady bearing force amplitude and unsteady torque amplitude of the pump-jet propulsor rotor with circumferentially curved stators are significantly reduced compared with the conventional straight stator scheme. This shows that the circumferentially curved stator can significantly reduce the bearing force formed by the operation of the pump-jet propulsor rotor, effectively alleviate the structural vibration noise generated by the rotor during operation, and improve the acoustic stealth of the submarine.

[0084] In summary, the circumferentially curved stator changes the spatial distribution of the rotor inflow, causing a favorable change in the phase angle of the high wake zone at each radial section of the rotor disk, thereby improving the rotor inflow quality, significantly reducing the exciting force of the pump-jet propulsion rotor, and reducing the structural vibration noise and hydrodynamic noise of the pump-jet propulsion, which is of great significance to improving the acoustic stealth combat capability of modern submarines. In addition, the curved large lateral skew stator further improves the pre-swirl effect of the inflow, offsets the circumferential velocity component of the induced velocity to a certain extent, and reduces the circumferential velocity component in the rotor wake, which is beneficial to reducing the kinetic energy loss caused by the circumferential velocity in the rotor wake, improving the propulsion efficiency of the pump-jet propulsion, and providing a new way to improve the propulsion performance of submarines.

[0085] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for a C-shaped circumferentially curved stator of a pump-jet propulsor with noise reduction and efficiency improvement, characterized in that: include: S100: Establish a hull-rudder-pump-jet propulsion calculation model to determine the rotation speed of the pump-jet propulsion rotor when the vehicle reaches the self-navigation point. Then, based on the distribution of the phase angle θ° of the rotor at different radius sections, and on the basis of the conventional straight stator, by changing the phase angle θ of the stator at different radii, preliminarily determine the side slant distance distribution parameter a of the pump-jet propulsion "C" circumferential curved stator opposite to the rotor tilt direction. i ; S200: Pump-jet propulsors with straight stators and "C"-shaped circumferentially curved stators were placed in underwater vehicles for self-propulsion test simulations. The thrust and torque of each component of the two propulsion units were monitored at the self-propulsion point. The propulsion efficiency η0 and unsteady force amplitude of the two propulsion units were obtained by data processing. In order to analyze the influence of "C" shaped circumferentially curved stator on the propulsion efficiency and unsteady force of pump-jet propulsor; S300: Based on the circumferentially curved stator in step S200, the distribution characteristics of the flow field between the stator trailing edge in the duct and the rotor disk surface in the preliminary scheme are analyzed to adjust the side slant distance distribution parameter a of the "C" shaped circumferentially curved stator. i , increase the positive intersection of the peak circumferential phase distribution characteristics of the flow field between the stator and the rotor at each radius and the profile phase distribution characteristics of the rotor blade at each radius, analyze the influence of different linear distributions of the stator circumferential phase angle on the propulsion efficiency and unsteady force of the pump-jet propulsor, and obtain different distribution forms of the stator circumferential phase angle θ; S400: Based on the optimization result of step S300, the geometric angle of attack α of the cross section at different radii of the stator blade and the chord-wise distribution of the stator blade cross section are optimized in sequence, thereby completing the design of the C-shaped circumferentially curved stator of the pump-jet propulsor.

2. The design method of a C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement according to claim 1 is characterized in that: In the flow field behind the trailing edge of the circumferentially curved stator, the phases of high wake areas at different radii are inconsistent; From the inner radius to the outer radius of the circumferentially curved stator, the variation trend of the phase angle in the high wake region is opposite to the variation trend of the rotor side skew angle.

3. The design method of a C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement according to claim 1 is characterized in that: The skew value of each radial section of the circumferentially curved stator is distributed in a power function form with the radius, that is: In the formula They respectively represent the dimensionless quantities of the stator section inclination value, the section radius, and the stator hub radius after being dimensionally non-dimensionalized by the propeller blade tip radius.

4. The design method of a C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement according to claim 1 is characterized in that: The circumferential phase angle of the circumferentially curved stator increases from the blade root to the blade tip as the radius increases, and gradually decreases in absolute value in the clockwise direction with the counterclockwise direction being positive. The circumferential phase angle reaches a negative peak value at the stator blade tip section.

5. The design method of a C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement according to claim 1 is characterized in that: Step S400 includes: (401) Based on the optimization result of step S300, the geometric angle of attack α of the cross section at different radii of the stator blade is adjusted to obtain the influence of the distribution form of the radial geometric angle of attack α on the propulsion efficiency and unsteady force of the pump-jet propulsor, and the increase in the propulsion efficiency of the pump-jet propulsor and the reduction in the amplitude of the unsteady force are comprehensively considered to select the most suitable distribution form of the geometric angle of attack α as the optimization result; (402) Based on the optimization result of step (401), the chord-wise distribution form of the stator blade profile is changed to obtain the influence of the chord-wise distribution form of the blade profile on the propulsion efficiency and unsteady force of the pump-jet propulsion system. The increase in the propulsion efficiency of the pump-jet propulsion system and the reduction in the amplitude of the unsteady force are comprehensively considered, and the most suitable chord-wise distribution form of the blade profile is selected as the optimization result.

6. A design method for a C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement according to any one of claims 1 to 5, characterized in that: The propulsion efficiency η of the pump-jet propulsion system is: Where n is the propeller speed, Q is the rotor torque, R0 is the towing resistance without pump-jet propulsion, F is the pump-jet-hull force after the pump-jet propulsion is installed, and V is S is a given incoming flow velocity.

7. A C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement, characterized in that: The method for designing a C-shaped circumferentially curved stator for a pump-jet propulsion system with noise reduction and efficiency enhancement as described in any one of claims 1 to 6 is used for implementation.

8. The C-shaped circumferentially curved stator of a pump-jet propulsion system for noise reduction and efficiency enhancement according to claim 8, characterized in that: The stator has a skew form opposite to the skew direction of the rotor. From the stator blade root to the blade tip, as the radius increases, the circumferential phase angle gradually increases in absolute value in the clockwise direction, with the counterclockwise direction being positive, and the circumferential phase angle gradually decreases. At the stator blade tip section, the circumferential phase angle reaches a negative peak value.

9. The C-shaped circumferentially curved stator of a pump-jet propulsion system for noise reduction and efficiency enhancement according to claim 8, characterized in that: The skew value of each radial section of the circumferentially curved stator is distributed in a power function form with the radius, that is: In the formula They respectively represent the dimensionless quantities of the stator section inclination value, the section radius, and the stator hub radius after being dimensionally non-dimensionalized by the propeller blade tip radius.

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