阅读说明：本技术 一种喷水推进器的激励载荷加载方法 (Excitation load loading method of water jet propeller ) 是由 赵超 徐志亭 夏益美 李聪 马云飞 于 2019-10-29 设计创作，主要内容包括：本发明实施例公开了一种喷水推进器的激励载荷加载方法,包括步骤：基于水动力学原理构建喷水推进系统模型；通过水动力计算软件控制所述喷水推进系统模型运行,并于所述喷水推进器的流道稳定时采集流道壁上各监控点上的脉动压力值；通过傅里叶变换将脉动压力值的时域数据转换为频域数据,对频域数据进行分析,得出各监控点上叶轮叶频对应的激励脉动压力幅值和脉冲压力相位角；建立船体尾部结构的动力学分析模型；将脉动压力幅值和脉冲压力相位角加载于动力学分析模型的流道上,实现了喷水推进器激励力的频域加载,解决了采用喷水推进形式船舶的激励载荷获取及加载问题,从而对船体的振动响应状况有一定的把控。(The embodiment of the invention discloses an excitation load loading method of a water jet propeller, which comprises the following steps: constructing a water jet propulsion system model based on a hydrodynamic principle; controlling the running of the water jet propulsion system model through hydrodynamic calculation software, and acquiring the pulsating pressure value of each monitoring point on the wall of the flow channel when the flow channel of the water jet propeller is stable; converting time domain data of the pulsating pressure value into frequency domain data through Fourier transform, and analyzing the frequency domain data to obtain an excitation pulsating pressure amplitude and a pulse pressure phase angle corresponding to impeller blade frequency on each monitoring point; establishing a dynamic analysis model of a ship tail structure; the pulsating pressure amplitude and the pulsating pressure phase angle are loaded on a flow channel of a dynamics analysis model, so that the frequency domain loading of the exciting force of the water-jet propeller is realized, the problems of acquiring and loading the exciting load of a ship adopting a water-jet propulsion mode are solved, and the vibration response condition of a ship body is controlled to a certain extent.)

1. An excitation load loading method of a water jet propeller is characterized by comprising the following steps:

s100, constructing a water jet propulsion system model based on a hydrodynamic principle;

s200, controlling the running of the water jet propulsion system model through hydrodynamic calculation software, and collecting a pulsating pressure value on each monitoring point on the wall of a flow channel when the flow channel of the water jet propulsion system is stable;

s300, converting time domain data of the pulsating pressure value into frequency domain data through Fourier transform, and analyzing the frequency domain data to obtain an excitation pulsating pressure amplitude and a pulsating pressure phase angle corresponding to impeller blade frequency on each monitoring point;

s400, establishing a dynamic analysis model of the ship tail structure based on finite element analysis software;

s500, loading the pulsating pressure amplitude and the pulsating pressure phase angle on a flow channel of the dynamic analysis model.

2. The excitation load loading method of a waterjet propeller as recited in claim 1, wherein the waterjet propulsion system model comprises a tail hull model, a waterjet propeller runner wall model, and an impeller model.

3. The method as claimed in claim 1, wherein the criterion of stability of the flow channel is that the velocity of water flow in the wall of the flow channel keeps constant.

4. The excitation load loading method of a water jet propeller as recited in claim 1, wherein the dynamic analysis model has an internal flow passage shape structure that is identical to those of the water jet propeller and the stern hull, and the dynamic analysis model is a finite element model.

5. The method of claim 1, wherein in step S200, the time for acquiring the pulsation pressure value is greater than or equal to one period of rotation of the impeller.

6. The method for loading the excitation load of the water jet propeller according to claim 1, wherein the monitoring points comprise a first pressure monitoring group, a second pressure monitoring group and a third pressure monitoring group, and the first pressure monitoring group, the second pressure monitoring group and the third pressure monitoring group are all provided with a plurality of pressure monitoring points;

the first pressure monitoring group is arranged on the water inlet section of the flow channel, the second pressure monitoring group is arranged on the impeller section, and the third pressure monitoring group is arranged on the water outlet section of the flow channel.

7. The method for loading the excitation load of the water jet propeller as recited in claim 6, wherein the method for loading the pulsating pressure amplitude and the pulsating pressure phase angle comprises:

s501, sequentially numbering the pressure monitoring points on each section;

s502, in any section, taking the phase of each odd-numbered point as the pulsating pressure phase angle of each cross section on the section, and taking the even-numbered point as the boundary of the pulsating pressure action surface;

s503, drawing a cross section excitation loading graph according to the step S502, dividing each cross section into a plurality of areas, and obtaining an excitation force value and a pulsating pressure phase angle according to the maximum value and the phase value of the pressure value of each area.

8. The excitation load loading method of the water jet propeller as claimed in claim 7, wherein the pulsating pressure amplitude and the pulsating pressure phase angle are loaded in a length direction of the hull.

Technical Field

The invention relates to the field of ship structure dynamics analysis and evaluation, in particular to an excitation load loading method of a water jet propeller.

Background

In recent years, water jet propulsion devices have been widely used in the field of high-speed and high-performance ships. Compared with the traditional propeller propulsion, the water jet propulsion has the advantages of strong cavitation resistance, low vibration noise, strong variable working condition adaptation capability, higher propulsion efficiency, excellent manipulation performance and the like.

In China, the water jet propulsion device is generally used for small-sized monoships, planing boats, catamarans, trimarans and other high-speed ships, and the ships have the characteristics of small tonnage, small ship size and the like, and the length-width ratio of the ships is generally small. Such ships are sensitive to vibration under the action of an excitation source, and the vibration performance of the ships is very concerned by ship designers. The existing empirical formulas for hull vibration estimation are based on the assumption of slender bodies (large aspect ratio) and are clearly not applicable on this type of ship. Therefore, at the beginning of design, the vibration response of the ship body needs to be evaluated, and the vibration performance of the ship body needs to be known so as to guide the design.

The ship water jet propulsion device is one of main excitation sources of ship body vibration, and is different from the traditional screw propeller, the pulsating pressure generated by the screw propeller directly acts on the outer surface of the ship body, and the pulsating pressure generated by the screw propeller of the water jet propulsion device acts in the flow channel. However, in practice, because the flow field in the flow channel is very complex, the pulsating pressure generated by the propeller is not completely symmetrical, and a certain pulsating excitation is still generated, so that the influence of the pulsating pressure on the vibration of the hull of the small ship cannot be ignored.

At present, the pulsating pressure of the propeller is loaded according to a time domain or a frequency domain, and then the ship structure is subjected to vibration response analysis by using a frequency response analysis technology based on the calculation result of the excitation load. At the beginning of design, under the condition that the data is not complete, how to obtain the pulsating pressure value of the water jet propeller and how to load the excitation in the flow channel is not reported in China.

Disclosure of Invention

The invention aims to provide an excitation load loading method of a water jet propeller, and the excitation load loading method solves the technical problems.

The technical problem solved by the invention can be realized by adopting the following technical scheme:

an excitation load loading method of a water jet propeller comprises the following steps:

s100, constructing a water jet propulsion system model based on a hydrodynamic principle;

s200, controlling the running of the water jet propulsion system model through hydrodynamic calculation software, and collecting a pulsating pressure value on each monitoring point on the wall of a flow channel when the flow channel of the water jet propulsion system is stable;

s300, converting time domain data of the pulsating pressure value into frequency domain data through Fourier transform, and analyzing the frequency domain data to obtain an excitation pulsating pressure amplitude and a pulsating pressure phase angle corresponding to impeller blade frequency on each monitoring point;

s400, establishing a dynamic analysis model of the ship tail structure based on finite element analysis software;

s500, loading the pulsating pressure amplitude and the pulsating pressure phase angle on a flow channel of the dynamic analysis model.

Preferably, the water jet propulsion system model comprises a tail hull model, a water jet propeller runner wall model and an impeller model.

Preferably, the criterion for determining the stability of the flow channel is that the water flow velocity in the flow channel wall keeps constant motion.

Preferably, the internal flow passage shape structure of the kinetic analysis model is consistent with the internal flow passage shape structure of the water jet propeller and the tail hull, and the kinetic analysis model is a finite element model.

Preferably, in step S200, the time for acquiring the pulsation pressure value is an integral multiple of the rotation period of the impeller, and the time for acquiring the pulsation pressure value is greater than or equal to one rotation period of the impeller.

Preferably, the monitoring points comprise a first pressure monitoring group, a second pressure monitoring group and a third pressure monitoring group, and the first pressure monitoring group, the second pressure monitoring group and the third pressure monitoring group are all provided with a plurality of pressure monitoring points;

the first pressure monitoring group is arranged on the water inlet section of the flow channel, the second pressure monitoring group is arranged on the impeller section, and the third pressure monitoring group is arranged on the water outlet section of the flow channel.

Preferably, the loading method of the pulsating pressure amplitude and the pulsating pressure phase angle comprises the following steps:

s501, sequentially numbering the pressure monitoring points on each section;

s502, in any section, taking the phase of each odd-numbered point as the pulsating pressure phase angle of each cross section on the section, and taking the even-numbered point as the boundary of the pulsating pressure action surface;

s503, drawing a cross section excitation loading graph according to the step S502, dividing each cross section into a plurality of areas, and obtaining an excitation force value and a pulsating pressure phase angle according to the maximum value and the phase value of the pressure value of each area.

Preferably, the pulsating pressure amplitude and the pulsating pressure phase angle are loaded along the length direction of the ship body.

Has the advantages that: the invention sets a plurality of monitoring points on the impeller section, the water inlet and the water outlet of the flow passage, obtains the time domain distribution of pulsating pressure of each point through hydrodynamic software analysis, realizes the conversion from the time domain of an excitation load to a frequency domain result by utilizing Fourier transform, loads the result in the flow passage near the impeller by adopting a frequency domain loading method, and takes the result as an input value of vibration response analysis, obtains the pulsating pressure value of blade frequency excitation of the water jet propeller based on Computational Fluid Dynamics (CFD), realizes the frequency domain loading of the excitation force of the water jet propeller, solves the problem that the excitation load of a ship adopting a water jet propulsion mode is difficult to obtain and load, and has certain control on the vibration response condition of a ship body.

Drawings

FIG. 1 is a flow chart of the steps of the excitation load loading method of the waterjet of the present invention;

FIG. 2 is a schematic structural view of a model of the waterjet propulsion system of the present invention;

FIG. 3 is a schematic view of the position of each cross-sectional monitor point according to the present invention;

FIG. 4 is a schematic three-dimensional numbering view of a hydrodynamic model of the present invention;

FIG. 5 is a cross-sectional excitation loading diagram of the present invention;

FIG. 6 is a schematic diagram of the loading of the excitation of the present invention on a kinetic analysis model.

In the figure: 101-tail hull model; 102-water jet propeller runner wall model; 103-impeller model; 104-a water inlet; 105-water outlet.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

As shown in fig. 1, the present invention provides an excitation load loading method of a water jet propeller, comprising the steps of:

s100, constructing a water jet propulsion system model based on a hydrodynamic principle;

s200, controlling the running of the water jet propulsion system model through hydrodynamic calculation software, and collecting the pulsating pressure value on each monitoring point on the wall of the flow channel when the flow channel of the water jet propulsion system is stable;

s300, converting time domain data of the pulsating pressure value into frequency domain data through Fourier transform, and analyzing the frequency domain data to obtain an excitation pulsating pressure amplitude and a pulsating pressure phase angle corresponding to impeller blade frequency on each monitoring point;

s400, establishing a dynamic analysis model of the ship tail structure based on finite element analysis software;

s500, loading the pulsating pressure amplitude and the pulsating pressure phase angle on a flow channel of the dynamics analysis model.

The innovation points of the invention are as follows:

the invention sets a plurality of monitoring points on the impeller section, the water inlet and the water outlet of the flow channel, obtains the time domain distribution of pulsating pressure of each point through hydrodynamic software analysis, realizes the conversion from an excitation load time domain to a frequency domain result by utilizing Fourier transform, loads the result in the flow channel near the impeller by adopting a frequency domain loading method as an input value of vibration response analysis, obtains the pulsating pressure value of the blade frequency excitation of the water jet propeller based on Computational Fluid Dynamics (CFD), realizes the frequency domain loading of the excitation force of the water jet propeller, solves the problem that the excitation load of a ship adopting a water jet propulsion mode is difficult to obtain and load, and has certain control on the vibration response condition of a ship body.

As shown in fig. 2 and 3, as a preferred embodiment of the present invention, the model of the water jet propulsion system includes a trailing hull model 101, a water jet propeller runner wall model 102, and an impeller model 103, a runner of the trailing hull model 101 communicates with a runner of the water jet propeller runner wall model 102, and the impeller model 103 is provided in the runner. The pressure distribution in the region near the impeller, i.e., region 1 of fig. 2, is of great concern. Specifically, in the area of interest, three sections, a section face.1 at the water inlet 104, a section face.2 at the impeller, and a section face.3 at the water outlet 105, are selected, and 8 monitoring points are uniformly selected on each section, as shown in fig. 3.

As a preferred embodiment of the present invention, a typical working condition of the water jet propulsion device is analyzed based on hydrodynamic calculation software, and after controlling the operation of the water jet propulsion system model for a certain time step, the pulsating pressure value of each monitoring point on the wall of the flow channel can be measured and collected when the flow channel is stable, and the judgment standard of the stability of the flow channel is that the water flow velocity in the wall of the flow channel keeps moving at a constant velocity. The measured pulsating pressure value is more reliable when the flow channel is stable, and the collected pulsating pressure value is more suitable for the pulsating pressure value of the water jet propulsion system model in the running state.

As a preferred embodiment of the present invention, the internal flow channel shape structure of the kinetic analysis model is consistent with the internal flow channel shape structures of the waterjet propeller and the tail hull, so that the kinetic analysis model can truly reflect the structure of the jet pump flow channel. The kinetic analysis model is a finite element model, which facilitates the calculation and analysis of data by the finite element analysis software (msc.

As shown in fig. 4, as a preferred embodiment of the present invention, in step S200, the time for acquiring the pulsating pressure value is greater than or equal to one cycle of the impeller rotation, so as to ensure that the required data is acquired in at least one complete cycle. After a certain time step length and after the flow field is stable, the pulsating pressure value of each monitoring point on the wall of the flow channel is collected, at least one cycle of rotation of the impeller is carried out, and the time domain distribution of the pulsating pressure at 24 points of the three sections is obtained.

As a preferred embodiment of the present invention, the monitoring points include a first pressure monitoring group, a second pressure monitoring group and a third pressure monitoring group, and the first pressure monitoring group, the second pressure monitoring group and the third pressure monitoring group are all provided with a plurality of pressure monitoring points;

the first pressure monitoring group is arranged on the section of the water inlet of the flow passage, the second pressure monitoring group is arranged on the section of the impeller, and the third pressure monitoring group is arranged on the section of the water outlet of the flow passage. Specifically, 8 pressure monitoring points are uniformly arranged on each section, and the total number of the three sections is 24.

And converting the time domain results of the pulsating pressure of the 24 monitoring points obtained by the measurement and collection into frequency domain data results through Fourier transformation. And obtaining the amplitude of the excitation pulsating pressure and the pulsating phase angle under the blade frequency correspondence of each point of impeller through data analysis. Wherein the amplitude of the pulsating pressure takes a maximum value within the range of +/-30% of the blade frequency.

As shown in fig. 5, as a preferred embodiment of the present invention, a method for loading a pulsating pressure amplitude and a pulsating pressure phase angle includes:

s501, sequentially numbering pressure monitoring points on each section;

s502, in any section, taking the phase of each odd-numbered point as the pulsating pressure phase angle of each cross section on the section, and taking the even-numbered point as the boundary of the pulsating pressure action surface;

s503, drawing a cross section excitation loading graph according to the step S502, dividing each cross section into a plurality of areas as shown in FIG. 6, and obtaining an excitation force value and a pulsating pressure phase angle according to the maximum value and the phase value of the pressure value of each area.

Specifically, during loading, for each section, the sections are numbered in the order of 8 integers from 1 to 8. The phase positions of 1, 3, 5 and 7 points are used as pulsating pressure phase angles of all cross sections, and the phase positions of 2, 4, 6 and 8 points are used as boundaries of pulsating pressure action surfaces.

Dividing each cross section into four areas, wherein the loaded exciting force in the area 1 is the maximum pressure at three points 1, 2 and 8, and the pulsating pressure phase angle is the phase value at 1 point;

similarly, the excitation force loaded in the area 2 is the maximum value of the pressure at the three points of 2, 3 and 4, and the phase angle is the phase value of 3 points;

the excitation force loaded in the area 3 is the maximum pressure value at three points 4, 5 and 6, and the phase angle is the phase value at 5 points;

the excitation force loaded in the area 4 is the maximum value of the pressure at the three points of 6, 7 and 8, and the phase angle is the phase value of 8 points.

As shown in fig. 6, as a preferred embodiment of the present invention, during the loading process, the pulsating pressure amplitude and the pulsating pressure phase angle are loaded along the length direction of the hull. Since the water jet propeller is generally installed at the stern and the sailing direction of the ship coincides with the length direction of the ship, the loading direction is along the length direction of the ship.

Specifically, according to the cross-section loading diagram, loading is performed in the region Z1, namely, between face.3 and face.2, in a loading manner of the face.3 cross section;

loading in the region Z2, namely loading between FACE.2 and FACE.1 according to the loading mode of the FACE.2 section;

loading in the region Z3 is carried out in the manner of loading of the face.1 cross section, i.e. between face.1 and the distance extending one impeller diameter (D) towards the bow.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.