Design method for large-skew contra-rotating propeller propelling system of high-speed underwater vehicle

Abstract

A design method for a large-skew contra-rotating propeller propulsion system of a high-speed underwater vehicle comprehensively considers the wake flow distribution characteristics of the tail of the underwater vehicle, and comprises the steps of selecting circular rector distribution matched with the wake flow distribution form, optimizing disc surface ratio and chord length distribution, designing reasonable skew and trim distribution, selecting proper profile thickness and camber distribution and the like. The invention aims to improve the propulsive efficiency, reduce the yawing moment and meet the design requirements on the premise of avoiding cavitation. Particularly, in the design process, the design scheme is iteratively optimized by combining CFD calculation and a potential flow theory method, it is ensured that the final scheme is optimal in the aspects of propulsive efficiency and cavitation performance, and the requirements of the high-speed aircraft are met.

Description

Technical Field

[0001] The invention relates to a design method for a high-speed submersible large-side oblique counter-rotating propeller propulsion system, belonging to the technical field of submersible navigation control. Background Art

[0002] As the most commonly used form of propeller, the working principle of the propeller is based on the rotational motion of the blades. By sucking in fluid and accelerating it to discharge backward, the momentum difference is used to generate a reaction force, namely thrust, thereby pushing the vehicle forward. However, the rotational motion of the blades also causes the fluid to obtain a circumferential velocity when it is discharged (that is, the fluid discharge direction is along the spiral direction, not purely axial), so the propeller also obtains a circumferential fluid force. This circumferential velocity does not do effective work for propulsion, so it is called wake energy loss, which is one of the reasons for the reduced efficiency of the propeller. At the same time, the circumferential force of the fluid also has the effect of rotating the carrier along its longitudinal axis, and yaw is prone to occur due to roll when a single propeller is used.

[0003] In order to improve propulsion efficiency and reduce yaw torque, high-speed navigation bodies generally use contra-rotating propeller propulsion systems. The contra-rotating propellers can effectively balance the torque, reduce yaw, and improve the overall propulsion efficiency through the relative rotation of the front and rear sets of blades.

[0004] As an advanced form of counter-rotating propeller, the large-side skew counter-rotating propeller has attracted much attention due to its unique design features. Its large side skew angle design allows each radius section of the blade to gradually enter the high wake area, thereby effectively reducing vibration and noise, and improving cavitation performance. These advantages have made large-side skew counter-rotating propellers increasingly widely used in underwater high-speed vehicles. However, the current research on the theoretical design method of large-side skew counter-rotating propellers is still insufficient, especially how to avoid cavitation while improving propulsion efficiency, which requires a reasonable design of its large-side skew counter-rotating propeller. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, improve propulsion efficiency, and reduce wake energy loss and yaw moment.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A design method for a high-speed submersible large-side oblique counter-rotating propeller propulsion system, comprising:

[0008] S1: According to the wake distribution characteristics of the double-tail configuration at the rear of the submersible, a circulation distribution form matching the wake distribution is selected; the maximum value of the circulation distribution is biased towards the inner radius, and it decreases linearly from the radius where the maximum value is located to the blade tip to zero, and the circulation distribution of the front and rear propellers is designed according to the wake size and peak position of their respective radial positions;

[0009] S2: Determine the disk ratio and chord length distribution. The disk ratio should meet the basic requirements of cavitation initiation on the blade surface, and adjust the chord length distribution near the blade tip according to the CFD calculation results of the pressure distribution. The chord length distribution is calculated using a polynomial to ensure that the cavitation initiation requirements are met with a certain margin.

[0010] S3: Design the skew distribution and pitch distribution, comprehensively consider the wake size and blade strength, select the maximum skew angle, select single-sided skew or balanced skew, and design the cross skew distribution according to the phase line of the axial wake blade frequency component; at the same time, design the pitch distribution, and superimpose nonlinear pitch near the blade tip (0.025R-0.05R) to control the blade tip flow when necessary. The pitch amount generally does not exceed 0.05D;

[0011] S4: Select the profile thickness distribution, such as NACA 66mod. or quasi-elliptical distribution, to suit specific flow field conditions;

[0012] S5: Select the profile camber distribution, such as NACA a=0.8 camber line, or apply the three-dimensional lifting surface method to design the camber line shape of each radius profile to match the three-dimensional flow characteristics;

[0013] S6: Use the potential flow theory method to carry out preliminary design, and then perform the self-propulsion simulation performance prediction calculation of the submersible. According to the calculation results, determine whether the efficiency and cavitation requirements are met, and fine-tune the scheme. Repeat the above steps until the design requirements are met.

[0014] Preferably, the circulation distribution form in step S1 is designed based on an effective wake distribution of a real scale, and the effective wake distribution is obtained by empirically predicting a nominal wake distribution of a model scale calculated by CFD.

[0015] Preferably, the polynomial used in the calculation of the chord length distribution in step S2 is:

[0016]

[0017] in, r / R is the blade section position ratio, r is the blade section radius, R is the propeller radius, α, β, γ are unknown coefficients, k is a constant, 0<k<1. By adjusting the k value, the blade tip width can be adjusted, which can be combined with the adjustment of the blade profile pitch and camber to meet the requirements of cavitation initiation.

[0018] Preferably, the intersection form and intersection amount of the lateral inclination distribution in step S3 and the phase line of the axial wake blade frequency component are determined based on the experience of the designer.

[0019] Preferably, the nonlinear pitch in step S4 is superimposed near the blade tip to adjust the flow characteristics of the blade tip, improve the propulsion efficiency and weaken the tip vortex strength.

[0020] Preferably, in step S6, the self-propelled simulation performance prediction calculation includes the following aspects:

[0021] 1) The RANS method is used for the numerical simulation of self-propulsion performance, and the grid division and calculation are carried out in the simulation software;

[0022] 2) The self-propulsion calculation is performed at the model scale. During the design process, the propeller design or speed should be adjusted so that the model-scale self-propulsion calculation results meet the conditions of real-scale thrust-drag balance;

[0023] 3) The scale effect of the effective wake fraction is corrected by the scale effect of the nominal wake:

[0024]

[0025] where w em is the model-scale effective wake fraction, which is obtained by analyzing the model-scale self-propulsion simulation results; w es is the real-scale effective wake fraction, which is used for subsequent real-scale self-propulsion performance prediction; w nm and w ns are the model scale and real scale nominal wake fractions, respectively, which are obtained by numerical simulation results of model scale and real scale drag.

[0026] Preferably, in step S6, the self-propulsion simulation performance prediction calculation pays special attention to the simulation results of thrust, torque and blade surface pressure distribution to accurately evaluate whether the efficiency and cavitation requirements meet the design requirements.

[0027] Preferably, the system can significantly improve the propulsion efficiency of the twin-tail configuration submersible, while effectively reducing the yaw moment and meeting the design requirements while avoiding cavitation.

[0028] A high-speed submersible large-side oblique counter-rotating propeller propulsion system adopts the above-mentioned design method to determine the structural shape of each component, so that the propulsion efficiency is improved.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The method of the present invention improves propulsion efficiency, reduces wake energy loss and yaw moment, avoids cavitation, and ensures the quietness and detection distance of the submersible.

[0031] (2) The method of the present invention improves design efficiency and reduces the number of calculation groups.

[0032] (3) The method of the present invention increases the compatibility of the three design objectives of thrust, torque and propeller surface pressure distribution, so that the optimization direction can be independently controlled.

[0033] (4) The present invention uses a three-dimensional lifting surface method to finely design the arch curve shape of each radius section to match the three-dimensional flow characteristics, thereby achieving higher design accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a flow chart of the steps of the method of the present invention. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] A design method for a high-speed submersible large-skew counter-rotating propeller propulsion system comprehensively considers the wake distribution characteristics of the tail of the submersible, and aims to improve propulsion efficiency, reduce yaw moment, and meet design requirements under the premise of avoiding cavitation by selecting a circulation distribution that matches the wake distribution form, optimizing the disk ratio and chord length distribution, designing a reasonable skew and pitch distribution, and selecting a suitable section thickness and camber distribution. In particular, during the design process, the design scheme is iteratively optimized by combining CFD calculations and potential flow theory methods to ensure that the final scheme is optimal in both propulsion efficiency and cavitation performance to meet the needs of high-speed vehicles.

[0037] A design method for a high-speed submersible large-side oblique counter-rotating propeller propulsion system, such as Figure 1 As shown, including:

[0038] S1: Circulation distribution design

[0039] 1) Data collection: First, the nominal wake distribution data of the double-tail configuration at the rear of the submersible is obtained through CFD (computational fluid dynamics) simulation. These data include the wake velocity vector field and its peak position. Based on the above CFD calculation results, combined with the empirical prediction method, the actual scale effective wake distribution is obtained.

[0040] 2) Design circulation distribution: Design the circulation distribution form according to the effective wake distribution of the actual scale, ensure that the maximum circulation is biased towards the inner radius, and decreases linearly from the radius where the maximum value is to the blade tip to zero. The circulation distribution of the front and rear propellers needs to be finely adjusted according to the wake size and peak position of their respective radial positions to achieve the best matching effect.

[0041] S2: Determination of disk ratio and chord length distribution

[0042] 1) Determine the disk ratio: Preliminarily set the disk ratio based on the basic requirements for cavitation initiation on the blade surface.

[0043] 2) Adjust the chord length distribution: Use CFD to calculate the pressure distribution on the blade surface, and adjust the chord length distribution near the blade tip based on the result. The chord length distribution is calculated using the following polynomial:

[0044]

[0045] in, r / R is the blade section position ratio, r is the blade section radius, R is the propeller radius, c(r) is the distribution function of the chord length and the blade section position ratio, α, β, γ are unknown coefficients, k is a constant, 0<k<1, and the blade tip width can be adjusted by adjusting the k value. It is combined with the adjustment of the blade profile pitch and camber and is determined through iterative optimization to meet the requirements of cavitation initiation while leaving a certain margin.

[0046] S3: Side and pitch distribution design

[0047] 1) Skew distribution design: Consider the wake size and blade strength comprehensively and select the maximum skew angle. Select single-sided skew or balanced skew according to design requirements. Use the phase line of the axial wake blade frequency component to design the skew distribution form and amount that intersects with it. This process can be fine-tuned based on the designer's experience.

[0048] 2) Pitch distribution design: Design the pitch distribution to ensure the rationality of the overall streamline. Near the blade tip (0.025R-0.05R), nonlinear pitch is superimposed according to the flow characteristics to control the blade tip flow, and the pitch is controlled within 0.05D. This design aims to improve propulsion efficiency and reduce the strength of the tip vortex.

[0049] S4: Profile Thickness Distribution Design

[0050] According to the flow field conditions, select the appropriate section thickness distribution, such as NACA 66mod. or quasi-elliptical distribution. These distribution forms can effectively adapt to different fluid dynamic environments and improve the overall performance of the blade.

[0051] S5: Sectional camber distribution design

[0052] 1) Foundation selection: Preliminary selection of the arch curve such as NACA a=0.8 as the section arch foundation.

[0053] 2) Three-dimensional optimization: Applying the three-dimensional lifting surface method, the arch curve shape of each radius section is finely designed to match the three-dimensional flow characteristics and further improve the lift efficiency and propulsion performance of the blade.

[0054] S6: Design and Verification

[0055] 1) Preliminary design: The potential flow theory method is used for preliminary design to generate the preliminary geometric shape of the blade.

[0056] 2) CFD calculation: Integrate the preliminarily designed blade model into the overall model of the submersible to perform self-propulsion simulation performance prediction calculations. Pay special attention to the simulation results of thrust, torque, and blade surface pressure distribution to evaluate whether the efficiency and cavitation requirements meet the design requirements.

[0057] The self-propelled simulation performance prediction calculation includes the following aspects:

[0058] ① The RANS method is used for the numerical simulation of self-propulsion performance, and the grid division and calculation are carried out in the simulation software;

[0059] ② The self-propulsion calculation is carried out at the model scale. During the design process, the propeller design or speed should be adjusted so that the model-scale self-propulsion calculation results meet the conditions of real-scale thrust-drag balance;

[0060] ③ The scale effect of the effective wake fraction is corrected by the scale effect of the nominal wake:

[0061]

[0062] where w em is the model-scale effective wake fraction, which is obtained by analyzing the model-scale self-propulsion simulation results; w es is the real-scale effective wake fraction, which is used for subsequent real-scale self-propulsion performance prediction; w nm and w ns are the model scale and real scale nominal wake fractions, respectively, which are obtained by numerical simulation results of model scale and real scale drag.

[0063] 3) Fine-tuning of the scheme: According to the CFD calculation results, fine-tune the design scheme, including circulation distribution, chord length distribution, skew and pitch distribution, etc. Repeat the above steps until all design indicators meet the requirements.

[0064] A high-speed submersible large-side oblique counter-rotating propeller propulsion system adopts the above-mentioned design method to determine the structural shape of each component, so that the propulsion efficiency is improved.

[0065] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0066] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A design method for a high-speed submersible large-side oblique counter-rotating propeller propulsion system, characterized in that: include: S1: According to the wake distribution characteristics of the double-tail configuration at the rear of the submersible, the circulation distribution form matching the wake distribution is selected; S2: Determine the disk ratio and chord length distribution; S3: According to the wake size and blade strength, select the maximum side tilt angle, select single-sided side tilt or balanced side tilt, and determine the side tilt distribution intersecting with the phase line of the axial wake blade frequency component; determine the pitch distribution; S4: Select the profile thickness distribution; S5: Select the profile camber distribution; S6: Use the potential flow theory method to carry out preliminary design, and then predict the self-propulsion simulation performance of the submersible based on the RANS method. According to the calculation results, judge whether the efficiency and cavitation requirements are met. If not, return to S1 and repeat the above steps by adjusting the circulation distribution, chord length distribution, skew distribution and pitch distribution until the requirements are met.

2. The design method of the large side oblique counter-rotating propeller propulsion system of a high-speed submersible according to claim 1 is characterized in that: In S1, the maximum value of the circulation distribution is biased towards the inner radius, and decreases linearly from the radius where the maximum value is located to the blade tip to zero. The circulation distribution of the front and rear propellers is determined according to the wake size and peak position of their respective radial positions.

3. The design method of the large side oblique counter-rotating propeller propulsion system of a high-speed submersible according to claim 1 is characterized in that: In S1, the circulation distribution form is determined based on the effective wake distribution at the real scale, which is predicted from the nominal wake distribution at the model scale calculated by CFD.

4. The design method of the large side oblique counter-rotating propeller propulsion system of a high-speed submersible according to claim 1 is characterized in that: In S2, the disk ratio should meet the requirements of cavitation initiation on the blade surface, and the chord length distribution near the blade tip should be adjusted according to the CFD calculation results of the pressure distribution. The chord length distribution is calculated using a polynomial to ensure that the cavitation initiation requirements are met and a margin is left.

5. The method for designing a propulsion system for a high-speed submersible with large side oblique counter-rotating propellers according to claim 4 is characterized in that: The polynomial used in the calculation of chord length distribution in S2 is: Among them, r = r / R, r / R is the blade section position ratio, r is the blade section radius, R is the propeller radius, α, β, γ are unknown coefficients, k is a constant, 0<k<1, and by adjusting the k value, the blade tip width is adjusted, which is combined with the adjustment of the blade profile pitch and camber to meet the requirements of cavitation initiation.

6. The method for designing a propulsion system for a high-speed submersible with large side oblique counter-rotating propellers according to claim 1, characterized in that: In S3, when determining the pitch distribution, a nonlinear pitch is superimposed near the blade tip to control the blade tip flow.

7. The method for designing a high-speed submersible large-side oblique counter-rotating propeller propulsion system according to claim 1, characterized in that: Self-propelled simulation performance prediction calculation, including: The numerical simulation of self-propulsion performance adopts the RANS method, and the grid division and calculation are carried out in the simulation software; The self-propulsion calculation is performed at the model scale, and the propeller design or speed is adjusted so that the model scale self-propulsion calculation results meet the conditions of real scale thrust-drag balance; The scale effect of the effective wake fraction is corrected by the scale effect of the nominal wake: where w em is the effective wake fraction of the model scale; w es is the real-scale effective wake fraction; w nm and w ns are the nominal wake fractions at model scale and real scale, respectively.

8. The method for designing a propulsion system for a high-speed submersible with large side oblique counter-rotating propellers according to claim 1, characterized in that: In S4, the profile thickness distribution selects NACA 66mod. or quasi-elliptical distribution.

9. The method for designing a propulsion system for a high-speed submersible with large side oblique counter-rotating propellers according to claim 1, characterized in that: In S5, the camber distribution of the section selects the NACA a=0.8 camber line or applies the three-dimensional lifting surface method to determine the camber line shape of each radius section.

10. A high-speed submersible large side oblique counter-rotating propeller propulsion system, characterized in that: The design method described in claim 1 is used to determine the structural shape of each component, so that the propulsion efficiency is improved.

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