A design method for a fully azimuth-rotating adjustable pitch ducted propeller

Abstract

This invention relates to the field of marine propulsion device manufacturing, specifically a design method for a fully azimuth-controlled adjustable-pitch ducted propeller. This method extracts the basic parameters of the ship's main engine and existing rudder propeller, and establishes an integrated arrangement scheme to replace the fixed-pitch propeller with an adjustable-pitch propeller while maintaining the original power parameters unchanged. Based on the theoretical diagram of the fixed-pitch ducted propeller, a hydrodynamic calculation program is executed, introducing correction factors for increased shell diameter ratio and slightly reduced disk area ratio, and forcibly lowering the theoretical thrust coefficient by 5%, to obtain the corrected target open-water characteristic curve. The overall rotational characteristics of the fully azimuth-controlled rudder propeller are utilized to provide thrust for reversing and steering, strictly limiting the pitch adjustment authority to adaptability requirements for low-speed navigation and providing maximum drag under multiple operating conditions. A single-crank slider mechanism is configured inside the propeller hub as the core rotor component, and a three-dimensional spatial layout is completed. An electro-hydraulic integrated servo control system, dominated by a PLC and incorporating a dual-pump parallel architecture and a built-in hydraulic lock, is established. This significantly reduces the frequency and physical amplitude of the propeller blade rotation angle.

Description

Technical Field

[0001] This invention relates to the field of ship propulsion device manufacturing technology, specifically to a design method for a fully azimuth-rotating adjustable pitch ducted propeller. Background Technology

[0002] In the field of marine propulsion, azimuth propellers and controllable pitch propellers are two core types of propulsion actuators. Azimuth propellers integrate propulsion and steering functions, and due to their excellent maneuverability and high cargo space utilization, they are widely used in special-purpose vessels such as tugboats and offshore platforms. Controllable pitch propellers, on the other hand, adapt to the thrust requirements of ships under different speeds and drafts by changing the blade pitch angle, thus fully utilizing the main engine power.

[0003] Most existing small and medium-sized vessels employ fixed-pitch propellers with azimuth thrusters and azimuth rudder propellers. This fixed-pitch design is optimized based on a specific single operating point and exhibits good hydrodynamic efficiency at the design speed. To achieve more complex maneuvering commands, some vessels have directly introduced conventional azimuth controllable-pitch propeller systems. Conventional controllable-pitch propellers rely entirely on significant pitch changes to achieve reversing, emergency stops, and various maneuvering and turning functions, with their blade angles frequently switching between +180 degrees and -180 degrees.

[0004] The aforementioned technical solutions have revealed significant application defects in actual operation. Fixed-pitch ducted propellers experience a sharp decline in efficiency after deviating from their design operating point, making it impossible to simultaneously meet multiple operational requirements such as maximum free speed, high bollard drag, and low-speed towing. Conventional controllable-pitch propellers, due to their excessive pitch variation and extremely high adjustment frequency, subject the internal rotor mechanism to severe alternating loads, resulting in a bulky system structure, cumbersome control logic, and severely compromised mechanical lifespan and operational reliability of the entire system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a design method for a fully azimuth-rotating adjustable pitch ducted propeller, which solves the problem of existing propulsion systems struggling to balance adaptability to multiple operating conditions and structural reliability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a design method for a fully azimuth-rotating adjustable-pitch ducted propeller, comprising the following steps: Extract the main engine parameters and existing basic parameters of the target ship's rudder propeller. Under the constraint of keeping the original power and propulsion parameters unchanged, establish an overall integrated layout scheme for replacing the fixed-pitch propeller with a controllable-pitch propeller for the azimuth thruster. Based on the preset theoretical map of fixed-pitch ducted propeller, the propeller hydrodynamic calculation program is executed to predict the changes in open-water performance caused by structural changes, and then obtain the open-water characteristic curve of the target ducted controllable pitch propeller. Construct a three-dimensional digital model of the pitch control mechanism, including the propeller hub assembly, oil inlet assembly, and feedback assembly, and complete the interference verification and spatial layout of the internal mechanical transmission components. An electro-hydraulic integrated control architecture dominated by a programmable logic controller is established, and hydraulic servo adjustment and state feedback control are implemented for the action nodes of the adjusting mechanism.

[0007] Preferably, the execution of the propeller hydrodynamic calculation program includes specific correction steps, as follows: The 19A+Ka4-70 fixed-pitch duct propeller pattern was selected as the basic performance evaluation platform. Introducing correction factors for the increase in shell diameter ratio and slight decrease in disk area ratio caused by the increase in the rotor hub of the controllable pitch propeller; The theoretical thrust coefficient was forcibly reduced by 5%, and the corrected open-water characteristic curve of the ducted control pitch propeller was generated according to the standard prediction formula.

[0008] Preferably, when establishing the overall integrated layout scheme, motion constraint rules are set for the action range of the blade rotation angle: The azimuth propeller provides the vector thrust required for reversing, emergency stopping, and various maneuvers by utilizing its own overall rotational characteristics. The pitch adjustment authority of the adjustable propeller is limited to the multi-condition adaptation requirements of low-speed navigation, providing maximum drag, and maintaining the highest free speed; By eliminating the reciprocating motion of the blades within the range of positive 180 degrees to negative 180 degrees, the frequency and amplitude of the blade rotation mechanism are reduced from the logic control level.

[0009] Preferably, when constructing the three-dimensional digital model of the adjusting mechanism, the assembly association of each fluid and mechanical transmission component is as follows: The propeller hub assembly includes a combination of propeller blades, propeller hub, servo cylinder and crank-slider mechanism, and the entire assembly is hydraulically keyless connected to the front end face of the propeller shaft. The oil inlet assembly consists of an oil distributor, a pressure oil pipe, and a rotary joint. The oil distributor is fastened to the rear end face of the propeller shaft via a flange structure, and the rotary joint is directly connected to the upper end of the rudder sleeve to ensure the continuity of the hydraulic oil circuit.

[0010] Preferably, a single crank-slider mechanism is configured inside the propeller hub assembly as the blade mechanism for performing pitch-changing action, and the specific operation is as follows: Each individual blade is fitted with a single horizontal crank arm structure at its root; The horizontal crank arm is driven by the reciprocating linear displacement generated by the servo cylinder, thereby generating a rotational torque that overcomes hydrodynamic resistance and changes the angle of the blade space towards the water.

[0011] Preferably, the specific operation for establishing the electro-hydraulic integrated control architecture is as follows: The real-time displacement data of the servo cylinder is collected and transmitted back to the control center. The duty cycle electrical signal output by the PLC controller is used to implement millisecond-level switching control of the hydraulic valve group in the oil inlet assembly. Matching the boundary parameters of the independently developed hydraulic sealing structure, the pitch adaptive following matching calculation is completed under the condition of drastic alternation of thrust load.

[0012] This invention provides a design method for a fully azimuth-rotating adjustable-pitch ducted propeller. It has the following beneficial effects: 1. This invention replaces the fixed-pitch propeller with a controllable-pitch propeller and integrates it with the azimuth duct system, strictly limiting the pitch adjustment authority to meet the requirements of multiple operating conditions such as low-speed navigation and providing maximum drag. It utilizes the overall rotation of the rudder propeller to achieve reversing and turning, significantly reducing the frequency and amplitude of the propeller blade angle, reducing the mechanical wear load on the propeller blade angle mechanism and its control system, and thus significantly improving the operational reliability of the entire propulsion system and the energy efficiency of the main engine.

[0013] 2. This invention utilizes a specific fixed-pitch ducted propeller theoretical graph to perform hydrodynamic calculations and specifically introduces correction factors for the increase in shell diameter ratio and slight decrease in disk area ratio caused by the increase in the hub size of the controllable pitch propeller. The thrust coefficient is forcibly reduced by 5% to generate a corrected open-water characteristic curve. This accurately quantifies the hydrodynamic loss attenuation during the fixed-pitch conversion process, laying a solid data foundation for the subsequent division of pitch boundary range and optimal matching of main engine power.

[0014] 3. This invention uses a single crank-slider mechanism as the core blade actuator, assembling a single horizontal crank arm at the root of each independent blade and driving it to move back and forth by a servo cylinder. This effectively avoids the defects of the linkage mechanism, which has many parts and requires an extra-long blade hub space. At the same time, it overcomes the disadvantage of the pin groove mechanism having too small a lever arm, which causes excessive blade resistance. Under the premise of ensuring the accuracy of the rotation angle control, it achieves a minimalist and compact layout in the narrow space inside the blade hub.

[0015] 4. This invention employs an electro-hydraulic integrated control system with a dual-pump architecture and a built-in hydraulic lock. The dual pumps address the differentiated flow requirements for long-term stable pitch and short-term adjustable pitch. The hydraulic lock, composed of a hydraulically controlled check valve, is directly embedded inside the power cylinder, preventing high-frequency malfunctions of the solenoid valve triggered by external rotary seal leakage. By shortening the leakage transmission link, the pitch locking stability of the ship during long-term navigation is greatly enhanced. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the single crank slider blade mechanism of the present invention; Figure 2This is a schematic diagram of the internal structure of the oil distributor of the present invention; Figure 3 This is a schematic diagram of the combined sealing structure of the present invention. Detailed Implementation

[0017] 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. Example

[0018] like Figure 1-3 As shown, this embodiment of the invention provides a design method for a fully azimuth-rotating adjustable-pitch ducted propeller, comprising the following steps: S1. Extract target ship operating environment parameters The project engineering team used the existing operating data of the 800kW tugboat as a benchmark, retrieving the rated power of the main engine, the baseline physical dimensions of the azimuth propeller, and the draft parameters. During the system planning phase, which controlled the modification costs and project timeline, a strict constraint was established to maintain the main external interface parameters of the main engine and propeller unchanged. The core demand for changing the fixed-pitch propeller to an adjustable propeller stemmed from the drastic fluctuations in the tugboat's propulsion efficiency under various typical operating conditions, including free speed, large bollard towing force, and towing. In conventional operations, a fixed-pitch propeller only achieves optimal hydrodynamic efficiency within a very narrow speed range. With the introduction of adjustable propeller technology, the design logic deeply decoupled the system control commands: the main body of the azimuth system is dedicated to handling the vessel's reversing, emergency stops, and large-angle maneuvering vectoring actions; the adjustable propeller system focuses solely on fine-tuning the pitch angle to address the demands for thrust compensation at low speeds and efficient utilization of the main engine power across the entire range. This task decoupling avoids the need for conventional controllable pitch propellers to frequently perform large-span rotations between ±180 degrees, paving the way for significant weight reduction and simplification of the mechanism.

[0019] S2. Propeller hydrodynamic calculations and performance recalibration For the redesign of the hydrodynamic characteristics of the modified model, the system directly adopted the No.19A duct with Ka4-70 propeller open-water test data, a technology with extremely high maturity in the industry, as a reference platform. Introducing controllable pitch inevitably leads to an increase in the mechanical hardware inside the propeller hub, causing a substantial expansion of the hub volume. This physical deformation manifests hydrodynamically as a significant increase in the shell diameter ratio and a slight contraction in the disk area ratio. After integrating the basic theoretical equations of the propeller with the actual ship design experience database, it was determined that the three-dimensional flow field around the propeller blades would undergo slight degradation. The calculation model explicitly stipulates a 5% forced descent correction for the theoretical thrust coefficient. After this rigorous descent correction step, an open-water characteristic curve of the ducted controllable pitch propeller, highly consistent with actual water conditions, was output. Based on this corrected characteristic curve, the safe physical boundary limits for dynamic pitch adjustment were further defined to ensure that the propulsion device does not experience severe cavitation erosion under full-power limit load. Simultaneously, the optimal coupling matching matrix between main engine speed, pitch adjustment amount, and speed was determined.

[0020] Combination Figure 1 As shown, the 3D digital development of the pitch adjustment mechanism is at the core of the mechanical hardware design. Multiple technical routes exist for the internal transmission chain that performs the pitch-changing action. Traditional linkage mechanisms, while having a low coefficient of motion friction, occupy an extremely long axial space within the impeller hub due to numerous hinge nodes; pin-groove mechanisms, although compact in external form, have an extremely short crank arm under the same size constraints, forcing the hydraulic system to output an exceptionally large driving torque. After detailed 3D interference calculations and mechanical simulation evaluation, this design scheme ultimately selected a single-crank slider mechanism as the impeller carrier. Based on... Figure 1 The structural layout shown features a single horizontal crank arm component mounted individually at the root of each independent blade within the rotor hub assembly. A linear push-pull displacement applied axially by a central servo cylinder directly drives the slider of this horizontal crank arm, thereby generating rotational torque to overcome strong hydrodynamic resistance. Although this configuration generates a small additional unbalanced force during blade rotation, it successfully achieves a significant reduction in the number of transmission components and a substantial improvement in angular response accuracy.

[0021] like Figure 2 and Figure 3 As shown, the hardware configuration for the oil inlet assembly includes an oil distributor unit that has undergone rigorous high-pressure fatigue durability testing. This distributor is securely fastened to the rear end face of the propeller shaft via a high-strength flange structure, while its rotary joint directly connects to the upper end of the steering gear sleeve to ensure smooth fluid flow. To completely prevent the escape of high-pressure hydraulic oil at the dynamic-static interface, Figure 2The internal design showcases a dedicated sliding piston rod combination seal ring. Verification tests demonstrated that after 180 hours of continuous operation at a fixed rotational speed under an ultimate working pressure of 24 MPa, no leakage was observed at the interface, perfectly meeting the stringent requirements of absolutely reliable sealing boundaries in harsh subsea conditions.

[0022] The electro-hydraulic integrated architecture at the control and drive levels has also undergone a systematic and profound reconstruction. Controlled-pitch propellers exhibit a highly regular operational pattern of "long-term stable pitch, short-term pitch adjustment" throughout their actual service life. If a single-pump hydraulic station maintains high-pressure, full-flow circulation output for an extended period, it will inevitably lead to severe oil temperature rise and significantly shorten the lifespan of pipeline components. The engineering solution here employs a high- and low-pressure dual-pump parallel fluid supply system. Based on the load sensor and controller instructions, the current operating condition is determined, and the switching frequency of the main and auxiliary pump groups is adjusted as needed to significantly optimize energy dissipation. The continuous maintenance of stable pitch performance highly depends on the absolute rigidity of the hydraulic circuit lock. Considering the numerous rotary joints, long pipelines, and other oil-transporting media between the control solenoid valve and the underwater power cylinder, any microscopic fluid leakage will force the solenoid valve to frequently activate for pressure replenishment. This design method directly embeds and embeds a hydraulic lock, precisely composed of two hydraulically controlled check valves, deep within the power cylinder body, physically isolating it from the backflow interference of external, lengthy pipeline leaks into the pressure chamber. The system also features a grid-connected, fault-tolerant integration of the pitch control hydraulic circuit with the propeller's own lubrication oil source, and selects proportional flow control valves and servo solenoid valve assemblies with high tolerance to oil cleanliness and particulate matter. Relying on the millisecond-level duty cycle modulation signal output by the controller's microprocessor, it achieves smooth, stepless pitch servo adjustment, successfully achieving precise attitude control under complex sea conditions.

[0023] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A design method for a fully azimuth-rotating adjustable-pitch ducted propeller, characterized in that, Includes the following steps: Extract the main engine parameters and basic parameters of the existing rudder propeller of the target ship. Under the constraint of keeping the original power and propulsion parameters unchanged, establish an overall integrated layout scheme for replacing the fixed-pitch propeller with the controllable-pitch propeller. Based on the preset theoretical map of fixed-pitch ducted propeller, the propeller hydrodynamic calculation program is executed to predict the changes in open-water performance caused by structural changes, and then obtain the open-water characteristic curve of the target ducted controllable pitch propeller. Construct a three-dimensional digital model of the pitch control mechanism, including the propeller hub assembly, oil inlet assembly, and feedback assembly, and complete the interference verification and spatial layout of the internal mechanical transmission components. An electro-hydraulic integrated control architecture dominated by a programmable logic controller is established, and hydraulic servo adjustment and state feedback control are implemented for the action nodes of the adjusting mechanism.

2. The design method of a fully azimuth-rotating adjustable-pitch ducted propeller according to claim 1, characterized in that, The execution of the propeller hydrodynamic calculation program includes specific correction steps, as follows: The 19A+Ka4-70 fixed-pitch duct propeller pattern was selected as the basic performance evaluation platform. Introducing correction factors for the increase in shell diameter ratio and slight decrease in disk area ratio caused by the increase in the rotor hub of the controllable pitch propeller; The theoretical thrust coefficient was forcibly reduced by 5%, and the corrected open-water characteristic curve of the ducted control pitch propeller was generated according to the standard prediction formula.

3. The design method of a fully azimuth-rotating adjustable-pitch ducted propeller according to claim 1, characterized in that, When establishing the overall integrated layout scheme, motion constraint rules were set for the action range of the blade rotation angle: The azimuth propeller provides the vector thrust required for reversing, emergency stopping, and various maneuvers by utilizing its own overall rotational characteristics. The pitch adjustment authority of the adjustable propeller is limited to the multi-condition adaptation requirements of low-speed navigation, providing maximum drag, and maintaining the highest free speed; By eliminating the reciprocating motion of the blades within the range of positive 180 degrees to negative 180 degrees, the frequency and amplitude of the blade rotation mechanism are reduced from the logic control level.

4. The design method of a fully azimuth-rotating adjustable-pitch ducted propeller according to claim 1, characterized in that, When constructing the three-dimensional digital model of the aforementioned adjustment mechanism, the assembly relationships of each fluid and mechanical transmission component are as follows: The propeller hub assembly includes a combination of propeller blades, propeller hub, servo cylinder and crank-slider mechanism, and the entire assembly is hydraulically keyless connected to the front end face of the propeller shaft. The oil inlet assembly consists of an oil distributor, a pressure oil pipe, and a rotary joint. The oil distributor is fastened to the rear end face of the propeller shaft via a flange structure, and the rotary joint is directly connected to the upper end of the rudder sleeve to ensure the continuity of the hydraulic oil circuit.

5. The design method of a fully azimuth-rotating adjustable-pitch duct propeller according to claim 4, characterized in that, A single crank-slider mechanism is configured inside the propeller hub assembly as the blade mechanism for performing pitch-changing action, and the specific operation is as follows: Each individual blade is fitted with a single horizontal crank arm structure at its root; The horizontal crank arm is driven by the reciprocating linear displacement generated by the servo cylinder, thereby generating a rotational torque that overcomes hydrodynamic resistance and changes the angle of the blade space towards the water.

6. The design method of a fully azimuth-rotating adjustable-pitch ducted propeller according to claim 1, characterized in that, The specific steps for establishing the electro-hydraulic integrated control architecture are as follows: The real-time displacement data of the servo cylinder is collected and transmitted back to the control center. The duty cycle electrical signal output by the PLC controller is used to implement millisecond-level switching control of the hydraulic valve group in the oil inlet assembly. Matching the boundary parameters of the independently developed hydraulic sealing structure, the pitch adaptive following matching calculation is completed under the condition of drastic alternation of thrust load.

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