Pump-jet propeller with balanced type laterally-inclined stator blades and design method of pump-jet propeller

Abstract

The invention discloses a pump-jet thruster with balanced type laterally-inclined stator blades and a design method of the pump-jet thruster, and belongs to the field of underwater vehicle thrusters, and the pump-jet thruster comprises a stator, a rotor and a guide pipe; the stator is located in front of the rotor, stator blades are integrally distributed in a balanced side-inclined mode, the overall side-inclined direction of the stator blades is opposite to the side-inclined direction of the rotor, the side-inclined value of the roots of the stator blades is 0, the side-inclined value is gradually increased towards the negative direction along with increasing of the radius, and after a certain radius position reaches the maximum value of the negative direction, the side-inclined value is gradually increased towards the negative direction along with increasing of the radius. The skew value is gradually increased in the positive direction to the tip of the stator blade, and the skew value reaches the maximum value in the positive direction. The invention further specifically discloses a design method of the pump-jet propeller with the balanced type side-oblique stator blades, and according to the influence of side-oblique distribution of the stators on the hydrodynamic performance and noise performance of the pump-jet propeller, a balanced type side-oblique stator blade optimization scheme and a rotor and guide pipe optimization scheme matched with the balanced type side-oblique stator blade optimization scheme are determined.

Description

Technical Field

[0001] This invention belongs to the field of underwater vehicle propulsion technology, and particularly relates to a pump-jet propulsion system with balanced skewed stator blades and its design method. Background Technology

[0002] Pump-jet propulsion is an underwater propulsion device composed of a duct, rotor, and stator. It offers advantages such as delaying cavitation, reducing radiated noise from underwater vehicles, and improving propulsion efficiency, and is now widely used in various types of underwater vehicles. Pump-jet propulsion is generally installed at the stern of the vehicle, usually preceded by a rudder and other appendages. When the underwater vehicle is in motion, the fluid flowing past the rudder and other appendages creates a complex, non-uniform wake field at the stern. The circumferential non-uniformity of the flow field at the stern causes periodic changes in rotor surface pressure, generating low-frequency line spectrum noise. Meanwhile, turbulent pulsations in the stern cause irregular pulsations in rotor surface pressure, generating low-frequency broadband noise. In addition to radiated noise, the unsteady bearing forces generated by the rotor operating in the non-uniform flow field at the stern act on the hull through the bearings, causing vibration noise due to structural vibration. 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 non-uniformity of the flow field at the rotor disk. Therefore, optimizing the stator structure shape to improve the flow field at the rotor disk is a direct and effective way to reduce submarine noise.

[0003] As a crucial component of pump-jet propulsion, the stator, especially in front-stator pump-jet propulsion, typically features stator blades with asymmetrical cross-sections and a certain geometric angle of attack with the axis of attack. This helps to homogenize the incoming flow and improve the flow field. While adjusting the blade profile and geometric angle of attack is generally used to improve the inflow, the effect is limited. On the rotor disk, the phase angles of the wake peak regions at each radius tend to be consistent, leading to significant bearing forces during rotor blade rotation. Although increasing the rotor blade skew can reduce these bearing forces, excessive skew can cause structural strength issues with the rotor blades and increase flutter during rotor rotation, thereby increasing the noise of the pump-jet propulsion system. Summary of the Invention

[0004] In view of this, the present invention provides a pump-jet propulsion device with balanced skewed stator blades and its design method to solve the above problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A pump-jet propulsion device with balanced skewed stator blades includes a stator, a rotor, and a guide tube. The stator is located in front of the rotor. The blades of the stator are generally arranged in a balanced skewed distribution. The skew value is about 0 at the root of the stator blades. As the radius r increases, the skew value first gradually increases in the negative direction. After reaching the maximum value in the negative direction at a certain radius position, the skew value gradually increases in the positive direction as the radius r increases. At the tip of the stator blades, the skew value reaches the maximum value in the positive direction.

[0007] The lateral inclination value of each radius section of the stator blade refers to the circumferential distance between the midpoint of the chord length of each radius section of the stator blade and the stator reference line on the cylindrical surface at the corresponding radius; the stator reference line is a straight line passing through the midpoint of the chord length of the stator blade root section and intersecting perpendicularly with the central axis of the stator hub; the circumferential distance on the cylindrical surface refers to the circumferential arc length caused by the change in circumferential angular position on the same cylindrical surface.

[0008] Furthermore, the overall skew direction of the stator blades is opposite to that of the overall skew direction of the rotor; for right-hand rotors, the phase angle difference between the rotor blade tip section and the root section is positive in the counterclockwise direction, and the phase angle difference between the stator blade tip section and the root section is positive in the clockwise direction; for left-hand rotors, the phase angle difference between the rotor blade tip section and the root section is positive in the clockwise direction, and the phase angle difference between the stator blade tip section and the root section is positive in the counterclockwise direction.

[0009] Furthermore, the dimensionless skew values ​​of each radius profile of the stator blades satisfy a polynomial function distribution law.

[0010]

[0011] r is the radius of each section of the stator blade, a0 is a dimensionless constant, and r h Ri is the radius of the cross-section at the root of the stator blade, and r1 is the radius of a certain cross-section in the lower middle part of the stator blade. χ, r, r respectively h r1 is the radius of the stator blade tip section r p Dimensionless quantity after dimensionless transformation.

[0012] Furthermore, the dimensionless constant a0 takes values ​​ranging from 0.5. <a0<2.0。

[0013] Furthermore, dimensionless constants The range of values ​​is

[0014]

[0015] A design method for a pump-jet propulsion system with balanced skewed stator blades includes the following steps:

[0016] S100. First, determine the preliminary scheme of the conventional non-skewed stator pump-jet propeller, including the basic parameters and three-dimensional geometric shapes of the duct, the conventional non-skewed stator, and the rotor.

[0017] S200. Construct a CFD calculation model of the hull-rudder-pump-jet propeller, and obtain the correlation data of the hydrodynamic performance and noise performance of the pump-jet propeller through numerical calculation. The correlation data includes stator torque, stator resistance, rotor torque, rotor thrust, duct thrust, the amplitude of rotor unsteady force, as well as the surface pressure distribution, propulsion efficiency, propulsion power, torque imbalance, and hydrodynamic low-frequency line spectrum noise of the entire pump-jet propeller.

[0018] S300. Combine the rotation direction and skew direction of the pump-jet propeller rotor to determine the overall skew direction of the balanced skewed stator blades, so that the overall skew direction of the stator blades is opposite to the overall skew direction of the rotor, and make the skew value distribution function of each radius section of the stator blades be

[0019]

[0020] Keep the various parameters and shapes of the pump-jet propeller duct and rotor unchanged. On the basis of the conventional non-skewed stator, keep the other parameters of each radius section of the stator blades unchanged, and only change the skew value distribution function of each radius section of the stator blades the dimensionless constant a0 and where the value range of the dimensionless constant a0 is 0.5 < a0 < 2.0, and the dimensionless constant the value range of is

[0021] S400. According to the dimensionless constant coefficients a0 and corresponding to the various skew value distribution schemes of the balanced skewed stator blades in S300, use the method of S200 to perform CFD numerical calculation on the hydrodynamic performance of the pump-jet propeller behind the boat. According to the principle of the highest propulsion efficiency and the smallest amplitude of unsteady force of the pump-jet propeller, output the skew value distribution function of the balanced skewed stator blades the dimensionless constant a0 and and the optimized scheme of the skew value of the balanced skewed stator blade section distributed with the radius determined thereby.

[0022] Based on the balanced skewed stator blade optimization scheme obtained in S400, S500 keeps the skew value χ(r) of each radius section of the stator blade constant, and adjusts the geometric angle of attack α, camber f, and chord length C of each radius section of the stator blade respectively; by performing CFD numerical calculations on the integrated model of the hull-rudder-pump-jet propulsion system, the correlation data of various hydrodynamic performances of the pump-jet propulsion system under different radial distribution schemes of the geometric angle of attack α, camber f, and chord length C of the stator blade are obtained. Taking into account the performance indicators such as power matching, propulsion efficiency, and torque imbalance of the pump-jet propulsion system, the optimal results of the balanced skewed stator blade geometric angle of attack α, camber f, and chord length C with radius distribution are output.

[0023] Based on the balanced skew stator optimization scheme obtained from S500, S600 adjusts the pitch, camber, chord length, skew, inclination, thickness, and duct angle of attack, length, and shape of each radial section of the rotor blades. CFD numerical calculations are performed on the hydrodynamic performance of the aft pump-jet propulsion system to obtain the correlation data of various hydrodynamic performances of the pump-jet propulsion system, as well as the overall thrust and rotor surface pressure distribution of the pump-jet propulsion system. Based on the power balance between the propulsion system and the main engine at the design point, the torque balance of the propulsion system, the propulsion efficiency, the amplitude of the unsteady force of the rotor, and the rotor surface pressure distribution, appropriate parameters of pitch, camber, chord length, skew, inclination, thickness, and duct angle of attack, length, and shape of each radial section of the rotor blades are selected as the optimal rotor and duct optimization scheme for the pump-jet propulsion system that matches the balanced skew stator optimization scheme.

[0024] Furthermore, it also includes: based on the optimization of the pump-jet propulsion rotor and duct obtained in S600, and according to the optimization requirements of the hydrodynamic performance and noise performance of the pump-jet propulsion, iterative optimization design steps from S300 to S600 are carried out.

[0025] Furthermore, S500 includes any one or more optimization steps from S501 to S503:

[0026] Based on the optimized scheme of the skew distribution of the balanced skew stator blades obtained in S500, S501 changes the geometric angle of attack α of each radius section of the stator blades, analyzes the influence of the geometric angle of attack α of each radius section of the stator blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the most suitable geometric angle of attack α of the balanced skew stator blades with radius distribution;

[0027] Based on the optimized scheme of the skew distribution of the balanced skew stator blades obtained in S500, S502 changes the camber f of each radius section of the stator blades, analyzes the influence of the camber f of each radius section of the stator blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the camber f of the balanced skew stator blades with the radius distribution.

[0028] Based on the optimized scheme of the skew distribution of the balanced skewed stator blades obtained in S500, S503 changes the chord length C of each radius section of the stator blades, analyzes the influence of the chord length C of each radius section of the stator blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the chord length C of the balanced skewed stator blades with the radius distribution.

[0029] Furthermore, S600 includes any one or more optimization steps from S601 to S607:

[0030] Based on the balanced skew stator optimization scheme obtained from S600, S601 changes the pitch of each radius section of the rotor blades, analyzes the influence of the pitch of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade pitch distribution with radius.

[0031] Based on the balanced skew stator optimization scheme obtained from S600, S602 changes the camber of each radius section of the rotor blades, analyzes the influence of the camber of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade camber distribution with radius.

[0032] Based on the balanced skew stator optimization scheme obtained from S600, S603 changes the chord length of each radius section of the rotor blades, analyzes the influence of the chord length of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade chord length distribution with radius.

[0033] Based on the balanced skew stator optimization scheme obtained from S600, S604 changes the skewness of each radius profile of the rotor blades, analyzes the influence of the skewness of each radius profile of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade profile skewness with radius distribution.

[0034] Based on the balanced skew stator optimization scheme obtained from S600, S605 changes the longitudinal inclination of each radius section of the rotor blades, analyzes the influence of the longitudinal inclination of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the longitudinal inclination of the rotor blade section with the radius distribution.

[0035] Based on the balanced skew stator optimization scheme obtained from S600, S606 changes the thickness of each radius section of the rotor blades, analyzes the influence of the thickness of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade section thickness with the radius distribution.

[0036] Based on the balanced skew stator optimization scheme obtained from S600, 607 changes parameters such as duct angle of attack, length, and shape, analyzes the influence of duct angle of attack, length, and shape on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude, and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal optimization results for the duct angle of attack, length, and shape parameters.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. This invention utilizes a balanced, skewed stator in the pump-jet propulsion system, with its skew direction opposite to that of the rotor. After the non-uniform incoming flow is rectified by the stator blades, the phase of the wake peak region at different radii is inconsistent. From the inner radius to the outer radius, the phase angle variation trend of the wake peak region is opposite to the phase variation trend of the rotor's radii. This increases the orthogonality between the circumferential phase angle distribution characteristics of the stator wake peak region and the rotor blade sectional phase angle distribution characteristics, increasing the time difference between the corresponding moments when the rotor's radii enter the wake peak region. This increases the temporal asynchrony of the rotor blades' entry into the wake peak region, thereby reducing the amplitude of load fluctuations during rotor rotation, and consequently reducing the bearing force during rotor rotation. The decrease in rotor bearing force leads to a corresponding reduction in the vibration and noise of the stern structure caused by the bearing force. Therefore, this invention, through the balanced, skewed distribution of the stator blades alone, can achieve the effect of reducing the bearing force of underwater propulsion systems and the resulting structural vibration and noise.

[0039] 2. This invention makes the phase distribution of the load change curves of each radius section of the pump-jet propulsion rotor blades more different, and the radiated noise sound pressure change curves caused by load fluctuations of each section will also show a large phase difference. The hydrodynamic line spectrum noise sound pressure level of the entire rotor will also decrease accordingly. Therefore, this invention can reduce the hydrodynamic line spectrum radiated noise of underwater vehicle propulsion simply by using the balanced side-skewed distribution of stator blades.

[0040] 3. Compared with conventional pump-jet propellers without side-skewed straight stators, the balanced side-skewed stator blade pump-jet propeller of the present invention has a more significant reverse pre-swirl effect on the rotor inlet flow without increasing stator resistance. Under the premise of constant stator torque, the stator's geometric angle of attack and camber are smaller than those of conventional stators, and the stator resistance is reduced, thereby further improving the propulsion efficiency of the pump-jet propeller. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0042] Figure 1 It is a 3D diagram of a pump-jet propulsion system equipped with a conventional straight stator;

[0043] Figure 2 This is a side view of a pump-jet propulsion unit equipped with a conventional straight stator.

[0044] Figure 3 It is a three-dimensional geometric diagram of a pump-jet propulsion unit with a balanced inclined stator installed;

[0045] Figure 4 This is a geometric comparison diagram of balanced skewed stator blades and conventional straight stator blades;

[0046] Figure 5 This is a schematic diagram showing the skew direction of the balanced skewed stator and rotor;

[0047] Figure 6 This is a schematic diagram showing the variation of the skew value of a balanced skew stator with radius;

[0048] Figure 7 This is a schematic diagram showing the correspondence between the stator blade reference line and the side slope values ​​of each radius profile.

[0049] Figure 8 It is a cloud map showing the axial velocity distribution of the cross section at the midpoint between the rotor and stator;

[0050] Figure 9This is a comparison of the axial forces of rotors in different stator pump-jet propulsion units;

[0051] Figure 10 It is a comparison of the lateral forces on the rotors of different stator pump-jet propulsion units;

[0052] Figure 11 It is a comparison of the vertical forces on the rotors of different stator pump-jet propulsion units;

[0053] Figure 12 This is a comparison of the axial torque of the rotors of different stator pump-jet propulsion units;

[0054] Figure 13 This is a comparison of the lateral torque of the rotors of different stator pump-jet propulsion units;

[0055] Figure 14 This is a comparison of the vertical torque of the rotors of different stator pump-jet propulsion units.

[0056] In the figure:

[0057] 1-Guide tube, 1.1-Inner wall surface of guide tube, 2-Rotor, 3-Conventional straight stator, 4-Balanced skewed stator, 4.1-Reference line of balanced skewed stator blade, 5-Stator reference line, 6-Stator hub, 7-Central axis of stator hub. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment uses a front-stator pump-jet propulsion system on an underwater vehicle as the basis for verification. The pump-jet propulsion system's external structure is as follows: Figure 1 , Figure 2 As shown, it includes a duct 1, a 7-bladed rotor 2, and a 13-bladed conventional straight stator 3.

[0061] exist Figure 1 , Figure 2 Based on the pump-jet propulsion device shown, and taking into account the structural shape scheme and design method of this application, the structural shape of the conventional non-skewed straight stator is modified according to the characteristics of rotor rotation direction and rotor skew distribution with radius, resulting in a pump-jet propulsion device with balanced skewed stator blades, as shown. Figure 3 , Figure 4As shown, the skew value at the root side of the stator blade is approximately 0. As the radius r increases, the skew value first gradually increases in the negative direction. After reaching the maximum value in the negative direction at a certain radius position, as the radius r increases, the skew value gradually increases in the positive direction. At the tip of the stator blade, the skew value reaches the maximum value in the positive direction.

[0062] Specifically, for the pump-jet propeller with a balanced skew stator, the axial position of the stator is before the rotor of the pump-jet propeller, and the skew direction of the stator is opposite to that of the rotor of the pump-jet propeller. As Figure 5 shown, for a right-handed rotor, the phase angle difference between the tip section and the root section of the rotor blade is positive in the counterclockwise direction, and the phase angle difference between the tip section and the root section of the stator blade is positive in the clockwise direction; for a left-handed rotor, the phase angle difference between the tip section and the root section of the rotor blade is positive in the clockwise direction, and the phase angle difference between the tip section and the root section of the stator blade is positive in the counterclockwise direction.

[0063] Specifically, the dimensionless skew values of each radius section of the balanced skew stator blade satisfy the distribution law of a polynomial function

[0064]

[0065] where r is the radius of each section of the stator blade, a0 is a dimensionless constant, r h is the root radius of the stator blade, r1 is the radius of a certain section in the middle and lower part of the stator blade, χ, r, r h [[]]and h [[]]r1 are dimensionless quantities after being dimensionlessized by the tip radius r p p of the stator blade.

[0066] For the further determination of its optimization parameters, as Figure 6 and Figure 7 shown, in the distribution function of the skew values of each section of the balanced skew stator blade, the value range of the dimensionless constant a0 is 0.5 < a0 < 2.0, and the value range of the dimensionless constant is

[0067] Example 2

[0068] A design method for a pump-jet propeller with a balanced skew stator blade includes the following steps:

[0069] S100, first determine the preliminary scheme of a conventional non-skew stator pump-jet propeller, including the basic parameters and specific three-dimensional geometric shapes of the duct, the conventional non-skew stator, and the rotor.

[0070] ​S200. Construct a CFD calculation model of the hull-rudder-pump-jet propulsor, and obtain the correlation data of the hydrodynamic performance and noise performance of the pump-jet propulsor through numerical calculation. The correlation data includes, but is not limited to, stator torque, stator resistance, rotor torque, rotor thrust, duct thrust, rotor unsteady force amplitude, and the surface pressure distribution, propulsion efficiency, propulsion power, torque imbalance, and hydrodynamic low-frequency line spectrum noise of the whole pump-jet propulsor, etc.

[0071] S300. Combine the rotation direction and skew direction of the pump-jet propulsor rotor to determine the overall skew direction of the balanced skewed stator blades, make the overall skew direction of the stator blades opposite to the overall skew direction of the rotor, and make the skew value distribution function of each radius section of the stator blades be

[0072]

[0073] Keep various parameters and shapes of the pump-jet propulsor duct and rotor unchanged. On the basis of the conventional non-skewed stator, keep other parameters of each radius section of the stator unchanged, and only change the skew value distribution function of each radius section of the stator the dimensionless constant a0 in where the value range of the dimensionless constant a0 is 0.5 < q0 < 2.0, and the dimensionless constant the value range of

[0074] S400. Use the method of S200 to perform CFD numerical calculation on the hydrodynamic performance of the pump-jet propulsor behind the hull. According to the principle of the highest propulsion efficiency and the minimum unsteady force amplitude of the pump-jet propulsor, output the skew value distribution function of the balanced skewed stator blades the dimensionless constant a0 in and and the optimized scheme of the skew value of the balanced skewed stator blade section varying with the radius determined thereby.

[0075] Based on the S500 and S400S optimized scheme for the skew distribution of balanced skewed stator blades, the skew value χ(r) of each radial section of the stator blades is kept constant, while the geometric angle of attack α, camber f, and chord length C of each radial section of the stator blades are adjusted. CFD numerical calculations are performed on the integrated hull-rudder-pump-jet propulsion model to obtain the propulsion efficiency, rotor torque, rotor power, and torque imbalance of the pump-jet propulsion system under different radial distribution schemes for the stator blades' geometric angle of attack α, camber f, and chord length C. Considering the power matching, propulsion efficiency, and torque imbalance of the pump-jet propulsion system, suitable angle of attack α, camber f, and chord length C at each radius of the balanced skewed stator blades are selected as the optimized scheme for the balanced skewed stator blades.

[0076] Based on the balanced skewed stator blade optimization scheme obtained from S500, the S600 method adjusts the pitch, camber, chord length, skewness, inclination, thickness, and duct angle of attack, length, and shape of each radial section of the rotor blades. CFD numerical calculations are performed on the hydrodynamic performance of the aft pump-jet propulsion system to obtain the correlation data of various hydrodynamic performances of the pump-jet propulsion system, as well as the overall thrust and rotor surface pressure distribution of the pump-jet propulsion system. Based on the power balance between the propulsion system and the main engine at the design point, the torque balance of the propulsion system, the propulsion efficiency, the amplitude of the unsteady force of the rotor, and the rotor surface pressure distribution, appropriate parameters for the pitch, camber, chord length, skewness, inclination, thickness, and duct angle of attack, length, and shape of each radial section of the rotor are selected as the optimal rotor and duct optimization scheme for the pump-jet propulsion system that matches the balanced skewed stator blade optimization scheme.

[0077] After obtaining the balanced skew stator and its matching pump-jet propulsion rotor and duct based on the above technical solutions and design methods, in order to analyze the propulsion performance of the balanced skew stator on the pump-jet propulsion and study its vibration reduction effect, a hull-rudder-pump-jet propulsion calculation model was established. Based on the CFD method, the hydrodynamic performance of the original conventional straight stator pump-jet propulsion and the balanced skew stator pump-jet propulsion was numerically calculated.

[0078] At the same speed V S Under the given rotational speed n, the resultant force F of the hull-pump-jet propulsion system and the rotor torque Q are calculated. In addition, before calculating the propulsion efficiency, the bare hull resistance R0 of the hull needs to be obtained. Finally, the obtained data are summarized as shown in Table 1.

[0079] Table 1 Comparison of underwater hydrodynamic parameters in self-propelled state

[0080] Hydrodynamic parameters conventional stator Balanced skew stator <![CDATA[Towing resistance R0 / N]]> 399.12 399.12 Pump-jet combined force F / N -12.63 21.99 Rotational speed n / rpm 1600 1600 Rotor torque Q / (N·m) 19.98 21.07

[0081] The propulsion efficiency η of the pump-jet propulsion system can be calculated using formula (1). The comparison results of the propulsion efficiency of the conventional straight stator pump-jet propulsion system and the balanced skew stator pump-jet propulsion system are shown in Table 2.

[0082]

[0083] Table 2 Comparison of Propulsion Efficiency

[0084] stator form η conventional stator 0.7125 Balanced skew stator 0.7364

[0085] Tables 1 and 2 show that, under the same speed and rotational speed, the balanced skewed stator pump-jet propulsion system increases the propulsion efficiency η by 3.35% compared to a conventional straight-stator pump-jet propulsion system. The main reason is that, without increasing stator drag, the balanced skewed stator has a more significant reverse pre-swirl effect on the rotor inlet flow, which helps reduce kinetic energy loss caused by circumferential velocity in the rotor wake and improves the propulsion efficiency of the pump-jet propulsion system.

[0086] Figure 8 Pump-jet propulsion systems with different stators operate at an incoming flow velocity of V. S The figure shows the axial velocity distribution cloud map of the flow field at the midpoint of the stator and rotor cross-section. As can be seen from the figure, compared to a conventional straight-stator pump-jet propulsion system, the balanced skewed stator alters the phase of the wake peak region at different radii. From the inner radius to the outer radius, the trend of the phase angle change in the wake peak region is opposite to the trend of the phase change in the rotor's radii profile, increasing the orthogonality between the circumferential phase angle distribution characteristics of the stator wake peak region with respect to radius and the rotor blade profile phase angle distribution characteristics with respect to radius.

[0087] Because the balanced skewed stator increases the orthogonality between the circumferential phase angle distribution characteristics of the stator wake peak region and the rotor blade profile phase angle distribution characteristics, the time difference between the corresponding moments when each radial profile of the rotor blade enters the wake peak region increases. This increases the temporal asynchrony of the entry of each radial profile of the rotor blade into the wake peak region. The phase distribution differences of the load variation curves of each radial profile with time (or with rotor rotation angle) are greater, and the time differences corresponding to the peak values ​​of the load variation curves of each radial profile with time are larger. After the loads of each radial profile 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. This results in a smaller amplitude of load fluctuation during the rotation of the pump-jet propeller rotor, which means a smaller bearing force during rotor rotation. The balanced skewed stator makes the phase distribution differences of the load variation curves of each rotor blade profile with time greater, and the radiated noise sound pressure curves caused by the load fluctuations of each profile will also show a larger phase difference with time. The overall hydrodynamic line spectrum noise sound pressure level of the rotor will also decrease accordingly.

[0088] Further analysis of the unsteady forces / torques of the pump-jet propulsion rotors with different stator designs was conducted. Time-domain data of the unsteady forces / torques of the rotors within one rotation cycle were compared to obtain comparative results for the unsteady forces / torques of the rotors of pump-jet propulsion units with different stator designs. Figures 9-14 As shown in Table 3 and Table 4, Fourier analysis was performed on the above time-domain calculation results to obtain the amplitude values ​​of the unsteady rotor force / torque at each blade frequency.

[0089] from Figures 9-14 It can be seen that, compared with the conventional straight stator installation scheme, the amplitude of rotor unsteady force / torque pulsation is significantly reduced after the pump-jet propulsion unit is installed with a balanced skew stator. The specific reduction is shown in Tables 3 and 4. The amplitude of the first-order blade frequency of the unsteady force is reduced by a maximum of 46.33%, and the amplitude of the first-order blade frequency of the unsteady torque is reduced by a maximum of 52.02%.

[0090] Table 3 Comparison of unsteady bearing force amplitudes of pump-jet propeller rotors with different stators

[0091] Unsteady force first-order blade frequency amplitude conventional stator Balanced skew stator rate of change Axial force / N 1.1446 0.9776 15.08％ lateral force / N 1.6770 0.8046 46.33％ Vertical force / N 2.0165 1.5544 21.14％

[0092] Table 4 Comparison of Unsteady Torque Amplitude of Pump-Jet Propeller Rotors with Different Stators

[0093] Unsteady torque first-order blade frequency amplitude conventional stator Balanced skew stator rate of change Axial torque / Nm 0.0399 0.0339 14.59％ Lateral torque / Nm 0.1271 0.0682 52.02％ Vertical torque / Nm 0.1553 0.1178 23.88％

[0094] In summary, the balanced skewed stator of this invention can alter the spatial distribution of the rotor inlet flow, resulting in a favorable change in the phase angle of the wake peak region at each radius section of the rotor disk. This improves the rotor inlet flow quality, significantly reduces the excitation force of the pump-jet propulsion rotor, and decreases the hydrodynamic noise of the pump-jet propulsion and the vibration noise of the hull structure caused by the excitation force. This is of great significance for improving the acoustic stealth of underwater vehicles. On the other hand, the balanced skewed stator can further improve the pre-swirl effect of the rotor inlet flow. Without increasing stator resistance, it helps to reduce the kinetic energy loss caused by the circumferential velocity in the rotor wake and improve the propulsion efficiency of the pump-jet propulsion.

Claims

1. A pump-jet propulsion system with balanced skewed stator blades, characterized in that, It includes a stator, a rotor, and a guide tube. The stator is located in front of the rotor. The blades of the stator are generally arranged in a balanced lateral distribution. The lateral value is 0 at the root of the stator blades. As the radius r increases, the lateral value first gradually increases in the negative direction. After reaching the maximum value in the negative direction at a certain radius position, the lateral value gradually increases in the positive direction as the radius r increases. At the tip of the stator blades, the lateral value reaches the maximum value in the positive direction. The lateral inclination value of each radius section of the stator blade refers to the circumferential distance between the midpoint of the chord length of each radius section of the stator blade and the stator reference line on the cylindrical surface at the corresponding radius; the stator reference line is a straight line passing through the midpoint of the chord length of the stator blade root section and intersecting perpendicularly with the central axis of the stator hub; the circumferential distance on the cylindrical surface refers to the circumferential arc length caused by the change in circumferential angular position on the same cylindrical surface.

2. A pump-jet propulsion device with balanced skewed stator blades according to claim 1, wherein the stator is located in front of the rotor, characterized in that, The overall skew direction of the stator blades is opposite to that of the overall skew direction of the rotor. For right-hand rotors, the phase angle difference between the rotor blade tip section and the root section is positive in the counterclockwise direction, and the phase angle difference between the stator blade tip section and the root section is positive in the clockwise direction. For left-hand rotors, the phase angle difference between the rotor blade tip section and the root section is positive in the clockwise direction, and the phase angle difference between the stator blade tip section and the root section is positive in the counterclockwise direction.

3. A pump-jet propulsion device with balanced skewed stator blades according to claim 1, characterized in that... The dimensionless sideslip values ​​of each radius profile of the stator blades satisfy a polynomial function distribution law. r is the radius of each section of the stator blade, a0 is a dimensionless constant, and r h Ri is the radius of the cross-section at the root of the stator blade, and r1 is the radius of a certain cross-section in the lower middle part of the stator blade. χ, r, r respectively h r1 is the radius of the stator blade tip section r p Dimensionless quantity after dimensionless transformation.

4. A pump-jet propulsion device with balanced skewed stator blades according to claim 3, characterized in that, The dimensionless constant a0 takes values ​​ranging from 0.

5. <a0<2.0。 5. A pump-jet propulsion device with balanced skewed stator blades according to claim 3, characterized in that, dimensionless constant The range of values ​​is 6. A design method for a pump-jet propulsion system with balanced skewed stator blades, characterized in that, Includes the following steps: S100, firstly determine the preliminary design of the conventional non-skewed stator pump-jet propulsion system, including the basic parameters and three-dimensional geometry of the duct, conventional non-skewed stator and rotor; S200, construct a CFD calculation model of the hull-rudder-pump-jet propulsion system, and obtain the correlation data of hydrodynamic performance and noise performance of the pump-jet propulsion system through numerical calculation. The correlation data includes stator torque, stator resistance, rotor torque, rotor thrust, duct thrust, rotor unsteady force amplitude, as well as the overall surface pressure distribution, propulsion efficiency, propulsion power, torque imbalance and hydrodynamic low-frequency line spectrum noise of the pump-jet propulsion system. S300, combining the rotation direction and lateral tilt direction of the pump-jet propulsion rotor, determines the overall lateral tilt direction of the balanced lateral tilt stator blades, ensuring that the overall lateral tilt direction of the stator blades is opposite to that of the rotor, and that the lateral tilt value distribution function of each radius section of the stator blades is... The various parameters and shapes of the pump-jet propulsor duct and rotor remain unchanged. Based on the conventional non-skewed stator, other parameters of each radius section of the stator blades remain unchanged, and only the distribution function of the skew value of each radius section of the stator blades is changed. The dimensionless constant a0 in where the value range of the dimensionless constant a0 is 0.5 < a0 < 2.0, and the dimensionless constant has a value range of S400, based on the dimensionless constant coefficient a0 corresponding to various skew value distribution schemes of the balanced skew stator blades in S300, and The hydrodynamic performance of the aft pump-jet propulsion system was numerically calculated using the S200 method. Based on the principle of maximizing propulsion efficiency and minimizing unsteady force amplitude in pump-jet propulsion systems, the distribution function of the skew value of the balanced skewed stator blades was output. The dimensionless constants a0 and And the optimized scheme for the distribution of the skew value of the balanced skew stator blade profile with radius determined therefrom; Based on the balanced skewed stator blade optimization scheme obtained in S400, S500 keeps the skew value χ(r) of each radius section of the stator blade constant, and adjusts the geometric angle of attack α, camber f, and chord length C of each radius section of the stator blade respectively; by performing CFD numerical calculations on the integrated model of hull-rudder-pump-jet propulsion, the correlation data of various hydrodynamic performances of the pump-jet propulsion under different radial distribution schemes of the geometric angle of attack α, camber f, and chord length C of the stator blade are obtained; taking into account the power matching, propulsion efficiency, and torque imbalance of the pump-jet propulsion, the optimal results of the balanced skewed stator blade geometric angle of attack α, camber f, and chord length C with radius distribution are output. Based on the balanced skew stator optimization scheme obtained from S500, S600 adjusts the pitch, camber, chord length, skew, inclination, thickness, and duct angle of attack, length, and shape of each radial section of the rotor blades. CFD numerical calculations are performed on the hydrodynamic performance of the aft pump-jet propulsion system to obtain the correlation data of various hydrodynamic performances of the pump-jet propulsion system, as well as the overall thrust and rotor surface pressure distribution of the pump-jet propulsion system. Based on the power balance between the propulsion system and the main engine at the design point, the torque balance of the propulsion system, the propulsion efficiency, the amplitude of the unsteady force of the rotor, and the rotor surface pressure distribution, appropriate parameters of pitch, camber, chord length, skew, inclination, thickness, and duct angle of attack, length, and shape of each radial section of the rotor blades are selected as the optimal rotor and duct optimization scheme for the pump-jet propulsion system that matches the balanced skew stator optimization scheme.

7. The design method of a pump-jet propulsion device with balanced skewed stator blades according to claim 6, characterized in that, Also includes: Based on the optimization of the pump-jet propulsion rotor and duct obtained in S600, iterative optimization design steps from S300 to S600 are carried out according to the optimization requirements of the hydrodynamic performance and noise performance of the pump-jet propulsion.

8. The design method of a pump-jet propulsion device with balanced skewed stator blades according to claim 6, characterized in that, S500 includes any one or more optimization steps from S501 to S503: Based on the optimized scheme of the skew distribution of the balanced skew stator blades obtained in S500, S501 changes the geometric angle of attack α of each radius section of the stator blades, analyzes the influence of the geometric angle of attack α of each radius section of the stator blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the most suitable geometric angle of attack α of the balanced skew stator blades with radius distribution; Based on the optimized scheme of the skew distribution of the balanced skew stator blades obtained in S500, S502 changes the camber f of each radius section of the stator blades, analyzes the influence of the camber f of each radius section of the stator blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the camber f of the balanced skew stator blades with the radius distribution. Based on the optimized scheme of the skew distribution of the balanced skewed stator blades obtained in S500, S503 changes the chord length C of each radius section of the stator blades, analyzes the influence of the chord length C of each radius section of the stator blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the chord length C of the balanced skewed stator blades with the radius distribution.

9. The design method of a pump-jet propulsion device with balanced skewed stator blades according to claim 7, characterized in that, S600 includes any one or more optimization steps from S601 to S607: Based on the balanced skew stator optimization scheme obtained from S600, S601 changes the pitch of each radius section of the rotor blades, analyzes the influence of the pitch of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade pitch distribution with radius. Based on the balanced skew stator optimization scheme obtained from S600, S602 changes the camber of each radius section of the rotor blades, analyzes the influence of the camber of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade camber distribution with radius. Based on the balanced skew stator optimization scheme obtained from S600, S603 changes the chord length of each radius section of the rotor blades, analyzes the influence of the chord length of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade chord length distribution with radius. Based on the balanced skew stator optimization scheme obtained from S600, S604 changes the skewness of each radius profile of the rotor blades, analyzes the influence of the skewness of each radius profile of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade profile skewness with radius distribution. Based on the balanced skew stator optimization scheme obtained from S600, S605 changes the longitudinal inclination of each radius section of the rotor blades, analyzes the influence of the longitudinal inclination of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the longitudinal inclination of the rotor blade section with the radius distribution. Based on the balanced skew stator optimization scheme obtained from S600, S606 changes the thickness of each radius section of the rotor blades, analyzes the influence of the thickness of each radius section of the rotor blades on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal result of the rotor blade section thickness with the radius distribution. Based on the balanced skew stator optimization scheme obtained from S600, 607 changes the duct angle of attack, length, and alignment parameters, analyzes the influence of the duct angle of attack, length, and alignment parameters on the power balance, torque balance, propulsion efficiency, rotor unsteady force amplitude, and rotor surface pressure distribution of the pump-jet propulsion unit, and outputs the optimal optimization results for the duct angle of attack, length, and alignment parameters.

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