CN111237293B - Design method of pressure pulsation attenuator integrated in constant-voltage variable pump - Google Patents

Design method of pressure pulsation attenuator integrated in constant-voltage variable pump Download PDF

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CN111237293B
CN111237293B CN202010035901.XA CN202010035901A CN111237293B CN 111237293 B CN111237293 B CN 111237293B CN 202010035901 A CN202010035901 A CN 202010035901A CN 111237293 B CN111237293 B CN 111237293B
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pulsation
pressure
attenuator
flow
volume
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CN111237293A (en
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王岩
申同圣
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Beihang University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B11/00—Equalisation of pulses, e.g. by use of air vessels; Counteracting cavitation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15D—FLUID DYNAMICS, i.e. METHODS OR MEANS FOR INFLUENCING THE FLOW OF GASES OR LIQUIDS
    • F15D1/00—Influencing flow of fluids

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Abstract

The invention discloses a design method of a pressure pulsation attenuator integrated in a constant-voltage variable pump, which comprises the following steps: step 1: a design objective is determined. Determining the working condition characteristics of the design object in the hydraulic system; step 2: the pressure pulsation attenuator is matched with the constant-pressure variable pump, and specifically comprises flow matching, pulsation amplitude matching and pulsation frequency matching; and step 3: determining the volume of a cavity of the pressure pulsation attenuator; and 4, step 4: determining the geometric shape of a cavity of the pulsation attenuator; and 5: matching working conditions to optimize the volume; step 6: and (5) intensity checking and experimental verification. The method can directly attenuate pulsation at a pulsation source without influencing other pipeline systems, has better attenuation effect and compact structure, and can reduce the volume of the whole hydraulic system. In the whole design process of the pressure pulsation attenuator, the method of theoretical calculation, one-dimensional and three-dimensional simulation and experimental verification is comprehensively used for mutual verification, so that the design quality and precision can be improved, and the designed pressure pulsation attenuator model is more feasible.

Description

Design method of pressure pulsation attenuator integrated in constant-voltage variable pump
Technical Field
The invention relates to a design method of a pressure pulsation attenuator, in particular to a design method of a pressure pulsation attenuator integrated in a constant-voltage variable pump, and belongs to the field of pressure pulsation control of a hydraulic system.
Background
The hydraulic system is widely applied in the aerospace field and mainly comprises a hydraulic energy device, a control device and an execution device, wherein a hydraulic pump is used as the hydraulic energy device and is mostly a positive displacement pump, the working principle of the hydraulic system determines flow pulsation with periodic change, the flow pulsation can generate pressure pulsation after encountering system liquid resistance, and the hydraulic system is damaged; second, the periodic pressure pulsations also cause fatigue damage to the pipeline or support structure; thirdly, the pressure pulsation can generate vibration noise, which is harmful to human health. With the development of the airborne hydraulic system towards high pressure and high power, the problem of coupling vibration of the pressure pulsation of the hydraulic energy system and the pipeline system is more prominent, and the development process of the airborne hydraulic system is seriously hindered, so that the inhibition of the pressure pulsation has important significance for improving the reliability of the airborne hydraulic system.
The pressure pulsation suppression method has various suppression methods, such as active suppression and passive suppression, pulse source suppression, load end suppression and the like, wherein the pressure pulsation attenuator has the advantages of good attenuation effect, short development period, convenience in maintenance and the like, and is widely used. The pressure pulsation attenuator has a plurality of structures, and the pressure pulsation attenuators with different structures can be suitable for hydraulic systems under different working conditions; the pressure pulsation attenuator is mostly connected with the export of hydraulic pump through the pipeline and is come the pressure pulsation in the attenuation pipeline, if integrate pressure pulsation attenuator on the hydraulic pump, not only can make whole hydraulic system structure compacter, can also restrain pressure pulsation from the pulsation source, the pulsation attenuation effect is better, and the machine carries the hydraulic pump and is mostly constant voltage variable pump. Therefore, how to design the pressure pulsation attenuator integrated in the constant-voltage variable pump is of great significance to the high-voltage and light-weight development of the airborne hydraulic system, and is the direction of deep research.
Disclosure of Invention
The invention aims to provide a design method of a pressure pulsation attenuator integrated in a constant-pressure variable pump, which aims to solve the technical problem of providing a matching rule and a design method of the pressure pulsation attenuator and the constant-pressure variable pump.
The invention discloses a design method of a pressure pulsation attenuator integrated in a constant-pressure variable pump, and relates to the determination of a design target, the matching of the pressure pulsation attenuator and the constant-pressure variable pump, the design of the volume and the shape of the pressure pulsation attenuator, experimental verification and the like.
When the pressure of a load end of the constant-pressure variable pump is lower than the pressure regulation lower limit, a swash plate of the plunger pump always keeps the maximum inclination angle, and the displacement of the pump is constant and maximum at the moment; the output pressure of the pump is continuously increased along with the continuous rise of the load pressure, the system gradually reaches a stable working condition, the adjusting mechanism pushes the swash plate to reduce the inclination angle of the swash plate, so that the displacement of the pump is reduced, the load pressure is kept in a certain range at the moment, the upper limit is determined by a threshold value set by the overflow valve, the lower limit is determined by the adjusting structure, and the inclination angle of the swash plate is continuously adjusted to adjust the flow and finally control the pressure in a certain range. As the system load is continuously increased, the flow pulsation and the pressure pulsation are simultaneously increased; when the system reaches a stable working condition, the flow pulsation and the pressure pulsation reach the maximum; then the load pressure is kept relatively stable, the flow is continuously reduced, and the flow pulsation and the pressure pulsation are simultaneously reduced.
The invention relates to a design method of a pressure pulsation attenuator integrated in a constant-voltage variable pump, which comprises the following steps:
step 1: a design objective is determined. Determining the working condition characteristics of the design object in the hydraulic system, specifically comprising: the structure size, rated displacement and the like of the constant-pressure variable pump; viscosity-temperature characteristics, density, etc. of the oil liquid; finally, the design target of the pressure pulsation attenuator is determined, including the pressure pulsation target amplitude pstAnd the maximum acceptable voltage drop value deltapmax。
Step 2: the pressure pulsation attenuator is matched with the constant-pressure variable pump. The method specifically comprises flow matching, pulsation amplitude matching and pulsation frequency matching.
a. Flow matching: and designing the pipe diameter values of the inlet and the outlet of the pressure pulsation attenuator according to the flow-pipe diameter requirement of the hydraulic system.
b. And (3) matching the pulse amplitude: the pulsation amplitude comprises a pressure pulsation amplitude and a flow pulsation amplitude, and the change trends of the pressure pulsation amplitude and the flow pulsation amplitude are consistent, so that only one of the pressure pulsation amplitude and the flow pulsation amplitude needs to be made; particularly, the maximum pressure pulsation amplitude of the constant-pressure variable pump is matched.
c. Pulse frequency matching: the pulsation frequency of the constant-pressure variable pump hydraulic system is mainly determined by the rotating speed, pressure and flow characteristic curves at different rotating speeds are placed in the same coordinate system for comparison, a 'dangerous point' at each rotating speed is found, and the pulsation amplitude of each dangerous point is matched.
And step 3: determining the volume of the cavity of the pressure pulsation attenuator. The volume of the cavity is calculated, firstly, the flow pulsation characteristic of the outlet of the pump needs to be determined, AMESim software can be used for one-dimensional modeling simulation, and after the characteristic curve of the flow pulsation is determined, the initial volume design range of the pulsation attenuator is further calculated, and the specific process is as follows.
The conservation of mass equation can be rewritten as
Figure BDA0002365984910000021
In the formula VstThe volume of the pulsation attenuator cavity is initially designed, delta V is the difference of the flow volumes of the inlet and the outlet of the pulsation attenuator in delta t time, E is the volume elastic modulus of oil, and p isstFor a target amplitude of pressure pulsation, qinFor the inlet flow of the pulsation attenuator, qoutIs the outlet flow of the pulsation attenuator. Maintaining the pressure pulsation value at the design target p if necessarystIt is necessary to make the pulsation attenuator absorb the pulsation flow rate per pulsation period by using the compressibility of the oil. The key point is to obtain the volume difference value delta V of the inlet and outlet flows of the pulsation attenuator, so the pulsation period is supposed to be delta T, and if the pump pulsation curve obtained by simulation is q1(t), q can be considered to bein(t)＝q1(t) is the pulsation attenuator inlet flow, while the pulsation attenuator outlet flow is considered to be qout(t)＝q1(t+t1) Wherein t is1The time from the inlet to the outlet of the pulsation attenuator is the time t1Cannot be accurately solved, but the volume of the pulsation attenuator can be estimated by using the formula (2), and V can be determined by only determining the value range of the delta VstThe value range of (a).
Figure BDA0002365984910000031
In the formula qiFor the volume flow exchanged with the control body of the ith。
As a result of analysis, it is found that, in the period of time Δ T/2, i.e., half a pulse cycle, Δ V satisfies the following condition
Figure BDA0002365984910000032
Figure BDA0002365984910000033
In the formula
Figure BDA0002365984910000034
To pass through a pulsation curve q1(t) the average flow rate obtained.
The initial volume of the cavity can be obtained by the formulas (1), (3) and (4) in a value range
Figure BDA0002365984910000035
Initial volume V of the chamberstAfter the range is determined, a CFD (Computational Fluid Dynamics) method is used for carrying out a grouping simulation test, other geometric dimensions are kept unchanged under a rated working condition, the relationship between the volumes of different cavities and the pulsation attenuation effect is compared, and the larger the volume is, the better the attenuation effect is.
And 4, step 4: the pulsation attenuator cavity geometry is determined. After the initial volume of the cavity is obtained, a grouping test is carried out by a CFD method, and the pulse attenuation amplitude and the pressure drop value of different cavity geometries, inlet and outlet positions and sizes are compared to determine the optimal geometry.
And 5: and matching working conditions to optimize the volume. And (3) judging whether the pressure pulsation attenuator can meet the requirements under the whole working condition according to the matching rule of the pressure pulsation attenuator and the constant-pressure variable pump obtained in the step (2), repeatedly adjusting the volume of the accommodating cavity according to the attenuation effect under the condition that the geometric shape is unchanged, and enabling the volume of the accommodating cavity of the design model to be as small as possible on the premise of ensuring the matching of the working conditions.
The method of the invention further comprises the following steps: step 6: and (5) intensity checking and experimental verification. And checking the structural strength of the attenuator through an ANSYS simulation platform, and judging whether the design meets the strength requirement under the maximum pressure. And the experiment is carried out through an experiment table to verify whether the attenuation effect meets the design requirement. If the effect is not good, the simulation method needs to be optimized, and the steps 3 to 5 are repeated again until all the requirements can be met.
The invention has the advantages and effects that:
the invention provides a matching rule of the pressure pulsation attenuator and the constant-pressure variable pump, integrates the pulsation attenuator on the constant-pressure variable pump, can directly attenuate pulsation at a pulsation source without influencing other pipeline systems, has better attenuation effect and compact structure, and can reduce the volume of the whole hydraulic system.
According to the invention, a plurality of influence factors of the pressure pulsation attenuator are considered, specifically including the volume and the shape of the cavity, the position and the size of an inlet and outlet pipeline and the like, and the analysis of a plurality of factors is integrated, so that the designed pressure pulsation attenuator has a better attenuation effect, has smaller volume and mass under the condition of the same attenuation effect, and is beneficial to the light weight development of an airborne hydraulic system.
In the whole design process of the pressure pulsation attenuator, the method of theoretical calculation, one-dimensional and three-dimensional simulation and experimental verification is comprehensively used, and the three methods are verified mutually, so that the design quality and precision can be improved, and the designed pressure pulsation attenuator model is more feasible.
Drawings
FIG. 1 is a flow chart of the design of the method of the present invention.
Fig. 2a, b and c are characteristic diagrams of the flow rate-pressure and pulsation-pressure of the constant-pressure variable pump.
Fig. 3 is a flow-pressure characteristic diagram of the constant pressure variable pump at different rotation speeds.
The various symbols in the figures are illustrated as follows:
qsis the maximum output flow of the pump; p is a radical ofsThe maximum average pressure which can be output by the pump when the inclination angle of the swash plate is kept to be maximum; p is a radical ofmaxThe maximum average pressure that the pump can output;the point a is the working condition that the inclination angle of the pump swash plate is maximum and the average pressure of a load end is 0; point b is the maximum inclination angle of the pump swash plate, and the average pressure at the load end is psThe working condition of (1); point c is the adjustment of the pump through the inclined angle of the swash plate and the overflow valve, and the average pressure of the load end is pmaxThe working condition of (1); n is1、n2、n3、n 44 different rotation speeds; 1. 2, 3 and 4 are respectively the 'dangerous points' with the maximum pulsation amplitude under 4 different rotating speeds.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings and specific embodiments.
The airborne constant-pressure variable pump is mainly an axial plunger pump, mainly comprises a cylinder body, an oil distribution disc, plungers, a swash plate and other main parts, wherein a plurality of plungers are arranged in the cylinder body, the plungers are axially arranged, one end of each plunger is connected with the swash plate through a sliding shoe, when the cylinder body rotates, the plungers can reciprocate in the cylinder body to complete oil absorption and oil pressing, and the inclination angle of the swash plate determines the displacement.
As shown in fig. 2a, a-b, the average pressure at the load end is increased until ps，psThe maximum average pressure which can be output by a constant-pressure variable pump (hereinafter referred to as a pump) when the inclination angle of the swash plate is kept to be maximum; b-c, the system gradually reaches a stable working condition, the required flow is continuously reduced, in order to keep the load pressure unchanged, the inclination angle of the swash plate is continuously reduced at the moment, so that the output flow of the pump is also reduced, the average output pressure is continuously increased, and the maximum pressure is p under the action of the overflow valvemax，pmaxIs the maximum average pressure that the pump can deliver. The constant-pressure variable pump has the function of adjusting the average pressure, the flow of the pump is adjusted by feeding back the pressure to adjust the inclination angle of the swash plate, so that the output pressure of the pump is adjusted, and meanwhile, the overflow valve is used to ensure that the average pressure fluctuates between b and c under the stable working condition of the system. As shown in fig. 2b and c, from the working condition a to the working condition b, as the load pressure of the system is continuously increased, the flow pulsation and the pressure pulsation amplitude are simultaneously increased; from the working conditions b to c, the load pressure is kept relatively stable, and the flow pulsation and the pressure pulsation amplitude are reduced simultaneously due to the fact that the flow is continuously reduced, so that the maximum values of the flow pulsation and the pressure pulsation amplitude are both in the working condition at the point b.
The invention discloses a design method of a pressure pulsation attenuator integrated in a constant-voltage variable pump, which comprises the following specific steps as shown in figure 1:
step 1: a design objective is determined. Determining the working condition characteristics of the design object in the hydraulic system, specifically comprising: the structure size, rated discharge capacity, rated pressure, rated rotating speed and the like of the pump; physical parameters such as viscosity-temperature characteristic, density, elastic modulus and the like of the oil liquid; and a design target of the pressure pulsation attenuator, including a pressure pulsation target amplitude pstAnd the maximum acceptable voltage drop value deltapmax。
Step 2: the pressure pulsation attenuator is matched with the constant-pressure variable pump. The method specifically comprises three items of flow matching, pulsation amplitude matching and pulsation frequency matching.
a. And (4) matching the flow. According to the pulsation attenuation mechanism, the factors influencing the average output flow mainly include the impedance, the factors influencing the impedance mainly include the flow cross-sectional area, the flow area in the cavity of most pulsation attenuators is generally larger than that of connecting pipelines on two sides, so that the average flow of the system is not influenced under most conditions in the cavity, and the flow of the system is influenced when the diameters of the inlet and outlet pipelines of the pressure pulsation attenuators are too small, so that the pipe diameters of the inlet and outlet of the pressure pulsation attenuators can be designed according to the flow-pipe diameter requirements of a hydraulic system during flow matching.
b. The pulse amplitudes are matched. When the pressure and the flow of the constant-pressure variable pump are changed, the load and the impedance of the system are basically unchanged, so the change trends of the output pressure pulsation amplitude and the output flow pulsation amplitude are consistent, and only one of the two changes needs to be done. Since the main evaluation indexes of the pulsation attenuator are performed according to the pressure pulsation amplitude, the pressure pulsation attenuator is matched with the pulsation amplitude of the constant-pressure variable pump according to the maximum pressure pulsation amplitude of the constant-pressure variable pump (specifically, as in the following steps 3-5).
c. The pulse frequencies are matched. The pulsation frequency of the constant-pressure variable pump hydraulic system is mainly determined by the rotating speed, the characteristics of the average pressure are basically unchanged along with the increase of the rotating speed, and the average flow rate is gradually increased. As shown in fig. 3, will be differentSpeed n1、n2、n3、n4The pressure and flow characteristic curve graphs are put in the same coordinate system for comparison, so that the dangerous points, namely 1, 2, 3 and 4 in the figure, at each rotating speed are found, the pulse amplitude of each point is matched, and the matching work of the whole pulse frequency can be completed.
And step 3: determining the volume of the cavity of the pressure pulsation attenuator. Calculating the initial volume of the cavity, firstly determining the flow pulsation characteristic of the outlet of the pump, and then calculating the initial volume design range of the pulsation attenuator after determining the characteristic curve of the flow pulsation by using AMESim software one-dimensional modeling simulation.
The conservation of mass equation can be rewritten as
Figure BDA0002365984910000051
In the formula VstThe volume of the pulsation attenuator cavity is initially designed, delta V is the difference of the flow volumes of the inlet and the outlet of the pulsation attenuator in delta t time, E is the volume elastic modulus of oil, and p isstFor a target amplitude of pressure pulsation, qinFor the inlet flow of the pulsation attenuator, qoutIs the outlet flow of the pulsation attenuator. Maintaining the pressure pulsation value at the design target p if necessarystIt is necessary to make the pulsation attenuator absorb the pulsation flow rate per pulsation period by using the compressibility of the oil. The key point is to obtain the volume difference value delta V of the inlet and outlet flows of the pulsation attenuator, so the pulsation period is supposed to be delta T, and if the pump pulsation curve obtained by simulation is q1(t), q can be considered to bein(t)＝q1(t) is the pulsation attenuator inlet flow, while the pulsation attenuator outlet flow is considered to be qout(t)＝q1(t+t1) Wherein t is1The time from the inlet to the outlet of the pulsation attenuator is the time t1Cannot be accurately solved, but the volume of the pulsation attenuator can be estimated by using the formula (2), and V can be determined by only determining the value range of the delta VstThe value range of (a).
Figure BDA0002365984910000061
In the formula qiThe volume flow exchanged with the control body is the ith.
As a result of analysis, it is found that, in the period of time Δ T/2, i.e., half a pulse cycle, Δ V satisfies the following condition
Figure BDA0002365984910000062
Figure BDA0002365984910000063
In the formula
Figure BDA0002365984910000064
To pass through a pulsation curve q1(t) the average flow rate obtained.
The initial volume of the cavity can be obtained by the formulas (1), (3) and (4) in a value range
Figure BDA0002365984910000065
Initial volume V of the chamberstAfter the range is determined, a CFD method is used for carrying out a grouping simulation test, other geometric dimensions are kept unchanged under a rated working condition, the relationship between the volumes of different cavities and the pulsation attenuation effect is compared, the larger the volume is, the better the attenuation effect is, but the higher the cost is, and the specific numerical value can be further determined by comprehensively considering the attenuation effect and the economical efficiency.
And 4, step 4: the pulsation attenuator cavity geometry is determined. After the initial volume of the cavity is obtained, other structural dimensions of the pulsation attenuator are determined by a CFD method, and the other structural dimensions mainly comprise the geometric shape of the cavity, the positions and the dimensions of inlet and outlet pipelines and the like. And similarly, respectively carrying out grouping tests on different geometric parameters, and comparing the pulsation attenuation amplitude and the pressure drop value under different geometric sizes under a rated working condition to determine the geometric shape with the best effect.
And 5: and matching working conditions to optimize the volume. And (3) according to the matching rule of the pressure pulsation attenuator and the constant-pressure variable pump provided in the step (2), carrying out all-condition matching on the pulsation attenuator by a CFD (computational fluid dynamics) method, judging whether the pulsation attenuator can meet the requirements under all conditions, properly reducing the volume when the attenuation effect is good, and properly increasing the volume when the effect is not good. Under the condition that the geometric shape is not changed, the volume of the accommodating cavity is repeatedly adjusted, and the volume of the accommodating cavity of the design model is enabled to be as small as possible on the premise that the working condition matching is guaranteed.
Step 6: and (5) intensity checking and experimental verification. And checking the structural strength of the attenuator through an ANSYS simulation platform, and judging whether the design meets the strength requirement under the maximum pressure. And the experiment is carried out through an experiment table to verify whether the attenuation effect and the pressure loss meet the design requirements or not. If the effect is not good and the design requirements cannot be met, the simulation method needs to be optimized, and the steps 3 to 5 are repeated again until all the requirements can be met.
Example (b):
the design target is as follows: the rated discharge capacity of a certain pump is 30L/min, the rated pressure is 28MPa, and the rated rotating speed is 6000 r/min; certain hydraulic oil density is 900kg/m3Bulk modulus of elasticity 0.8X 109Pa, dynamic viscosity at 40 ℃ of 0.032 Pa.s; the target amplitude of the pressure pulsation is +/-1.4 MPa, and the acceptable maximum pressure drop value is 0.1 MPa.
The pressure pulsation attenuator is matched with a constant-pressure variable pump, the flow is matched, the flow-pipe diameter requirement of a hydraulic system can be known, the minimum pipe diameter corresponding to a high-pressure hydraulic system with the flow of 30L/min is 8.9mm, and 9.5mm is taken; the pulse amplitude is matched, and the maximum pressure pulse amplitude is matched according to a pressure-pulse characteristic diagram of the pump; and (3) matching the pulsation frequency, and respectively matching the pulsation amplitude of the dangerous points at each rotating speed.
Determining the volume of the cavity of the pulsation attenuator, and performing one-dimensional simulation on the pump according to AMESim to obtain a pump pulsation curve q1(t) ± 30 ± 3.1sin (11304t), mean flow
Figure BDA0002365984910000071
According toThe volume value of the cavity can be calculated to be about 120-240 mL by the formula (5). And comparing the relationship between the volumes of different cavities and the pulsation attenuation effect, and taking 130mL of initial volume of the cavity by comprehensively considering the attenuation effect and the economical efficiency.
Determining the geometric shape of the cavity of the pulsation attenuator, and performing grouping simulation on the geometric shape of the cavity, the positions of inlet and outlet pipelines and other parameters by a CFD (computational fluid dynamics) method according to experience to obtain that the cavity is spherical, the inlet and outlet are inserted pipes, the 90-degree clock pulsation attenuation effect is good, and the maximum pressure drop also meets the requirement.
The volume is optimized under the matching working condition, the geometric shape of the cavity is optimized, the attenuation efficiency of the unit volume is improved, the volume can be correspondingly reduced, the full-working-condition matching is carried out on the pulsation attenuator by a CFD method, and the design requirement can be met when the final volume is 95 mL.
And intensity checking and experiment verification are carried out, and whether the intensity, the attenuation effect and the pressure loss of the pulsation attenuator meet the design requirements or not is actually verified.

Claims (3)

1. A design method of a pressure pulsation attenuator integrated in a constant-pressure variable pump is characterized in that: the method comprises the following steps:
step 1: determining a design target; determining the working condition characteristics of the design object in the hydraulic system, specifically comprising: the structure size and rated displacement of the constant-pressure variable pump; viscosity-temperature characteristics and density of oil liquid; finally, the design target of the pressure pulsation attenuator is determined, including the pressure pulsation target amplitude pstAnd the maximum acceptable voltage drop value deltapmax；
Step 2: the pressure pulsation attenuator is matched with the constant-pressure variable pump; the method specifically comprises flow matching, pulsation amplitude matching and pulsation frequency matching;
a. flow matching: designing the pipe diameter values of the inlet and the outlet of the pressure pulsation attenuator according to the flow-pipe diameter requirement of a hydraulic system;
b. and (3) matching the pulse amplitude: the pulsation amplitude comprises a pressure pulsation amplitude and a flow pulsation amplitude, and the change trends of the pressure pulsation amplitude and the flow pulsation amplitude are consistent, so that only one of the pressure pulsation amplitude and the flow pulsation amplitude needs to be made; specifically, the maximum pressure pulsation amplitude of a constant-pressure variable pump is matched;
c. pulse frequency matching: the pulsation frequency of a hydraulic system of the constant-pressure variable pump is mainly determined by the rotating speed, pressure and flow characteristic curves at different rotating speeds are placed in the same coordinate system for comparison, a 'dangerous point' at each rotating speed is found, and the pulsation amplitude of each dangerous point is matched;
and step 3: determining the volume of a cavity of the pressure pulsation attenuator;
and 4, step 4: determining the geometric shape of a cavity of the pulsation attenuator; after the volume of the cavity is obtained, a CFD method is used for carrying out a grouping test, and the pulse attenuation amplitude and the pressure drop value of different cavity geometries, inlet and outlet positions and sizes are compared to determine the optimal geometry;
and 5: matching working conditions to optimize the volume; and (3) judging whether the pressure pulsation attenuator can meet the requirements under the whole working condition according to the matching rule of the pressure pulsation attenuator and the constant-pressure variable pump obtained in the step (2), repeatedly adjusting the volume of the accommodating cavity according to the attenuation effect under the condition that the geometric shape is unchanged, and enabling the volume of the accommodating cavity of the design model to be as small as possible on the premise of ensuring the matching of the working conditions.
2. A method of designing a pressure pulsation attenuator integrated with a constant pressure variable pump according to claim 1, wherein: the specific process of the step 3 is as follows: firstly, determining the flow pulsation characteristic of an outlet of a pump, determining a characteristic curve of flow pulsation by using AMESim software one-dimensional modeling simulation, and then calculating the initial volume design range of a pulsation attenuator, wherein the specific process is as follows;
the conservation of mass equation can be rewritten as
Figure FDA0002365984900000011
In the formula VstThe volume of the pulsation attenuator cavity is initially designed, delta V is the difference of the flow volumes of the inlet and the outlet of the pulsation attenuator in delta t time, E is the volume elastic modulus of oil, and p isstFor a target amplitude of pressure pulsation, qinFor the inlet flow of the pulsation attenuator, qoutIs the outlet flow of the pulsation attenuator; maintaining the pressure pulsation value at the design target p if necessarystWithin the range, the pulsation attenuator needs to absorb the pulsation flow of each pulsation period by utilizing the compressibility of oil; the key point is to obtain the volume difference value delta V of the inlet and outlet flows of the pulsation attenuator, so the pulsation period is supposed to be delta T, and if the pump pulsation curve obtained by simulation is q1(t), q can be considered to bein(t)＝q1(t) is the pulsation attenuator inlet flow, while the pulsation attenuator outlet flow is considered to be qout(t)＝q1(t+t1) Wherein t is1The time from the inlet to the outlet of the pulsation attenuator is the time t1Cannot be accurately solved, but the volume of the pulsation attenuator can be estimated by using the formula (2), and V can be determined by only determining the value range of the delta VstThe value range of (a);
Figure FDA0002365984900000021
in the formula qiThe volume flow exchanged with the control body is the ith volume flow;
as a result of analysis, it is found that, in the period of time Δ T/2, i.e., half a pulse cycle, Δ V satisfies the following condition
Figure FDA0002365984900000022
Figure FDA0002365984900000023
In the formula
Figure FDA0002365984900000025
To pass through a pulsation curve q1(t) the average flow rate obtained;
the initial volume of the cavity can be obtained by the formulas (1), (3) and (4) in a value range
Figure FDA0002365984900000024
Initial volume V of the chamberstAfter the range is determined, a CFD method is used for carrying out a grouping simulation test, other geometric dimensions are kept unchanged under a rated working condition, the relationship between the volumes of different cavities and the pulsation attenuation effect is compared, and the larger the volume is, the better the attenuation effect is.
3. A method of designing a pressure pulsation attenuator integrated with a constant pressure variable pump according to claim 1, wherein: the method further comprises the step 6: intensity checking and experimental verification: checking the structural strength of the attenuator through an ANSYS simulation platform, and judging whether the design meets the strength requirement under the maximum pressure; and carrying out experimental verification through an experimental table to verify whether the attenuation effect meets the design requirement; if the effect is not good, the simulation method needs to be optimized, and the steps 3 to 5 are repeated again until all the requirements can be met.
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