CN115493800B - Synchronous parallel acquisition system for steady-state pressure and pulsating pressure data and application method - Google Patents
Synchronous parallel acquisition system for steady-state pressure and pulsating pressure data and application method Download PDFInfo
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Abstract
The invention discloses a synchronous parallel acquisition system and an application method for steady-state pressure and pulsating pressure data, which relate to the field of wind tunnel tests.A separate and same-type AD (analog-digital) digitizer is used by each acquisition unit in each acquisition terminal in a steady-state pressure measurement subsystem and a pulsating pressure measurement subsystem, phase locking is carried out by a phase-locked loop, and a time stamp counter is integrated in a processor of the AD digitizer; the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem provide synchronous clocks through an external synchronous control module; and the acquisition terminals of the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem are communicated with the central processing unit through the matched synchronous triggers. The invention provides a synchronous parallel acquisition system and an application method for steady-state pressure and pulsating pressure data, which realize synchronous parallel acquisition of the steady-state pressure data and the pulsating pressure data in a wind tunnel test so as to ensure the accuracy and time domain correlation of subsequent data processing.
Description
Technical Field
The invention relates to the field of wind tunnel tests. More specifically, the invention relates to a system for synchronously and parallelly acquiring steady-state pressure (data) and pulsating pressure (dynamic) data in a wind tunnel test and an application method thereof.
Background
The types of data required to be collected in the wind tunnel test comprise a plurality of types, and the model surface pressure and the internal cavity pulsating pressure are two very important data.
The measurement of the pressure distribution on the surface of the model is an important means for knowing the flow characteristics of the surrounding model, determining the positions of the maximum pressure point, the minimum pressure point, the separation point and the shock wave position, and determining the positions of the normal force, the pressure difference resistance and the pressure center point of the model, so that the aerodynamic characteristics of the aircraft are researched, the aerodynamic load of the aircraft is obtained, and load data are provided for the structural strength calculation of the aircraft. The conventional test method for the current pressure distribution is to open a plurality of pressure measurement spaces on the surface of a model, wherein the pressure at the pressure measurement holes is different from dozens of pressure measurement spaces to hundreds of pressure measurement spaces, the pressure at the pressure measurement holes is connected to an electronic pressure scanning valve through a ventilation conduit, and the pressure distribution data of the surface of the model is obtained through a pressure sensor and an analog-to-digital (A/D) conversion module of the electronic pressure scanning valve, as shown in figure 1, the electronic pressure scanning valve used for measuring the pressure data of the surface of the model is a data acquisition mode which simultaneously acquires dozens of pressure points to hundreds of pressure points and has a low sampling rate, and the limit sampling rate is generally within 1 KHz.
The pressure that changes rapidly and randomly over time is called the pulsating pressure. In the wind tunnel test, many complex flow phenomena, such as vortex, separation flow, turbulent flow and the like belong to unsteady flow, quite strong pulsating pressure is generated, and unsteady characteristics of the complex flow phenomena can be revealed through measurement of the pulsating pressure. It cannot be accurately described by mathematical expressions, has no instantaneous rules, and can be processed and analyzed only according to the statistical rules. The strong pulsating pressure can excite the structure of the aircraft to vibrate or cause a severe noise environment in the aircraft, and in addition, the surface thermal conductivity of the hypersonic aircraft can be influenced, so that the difficulty is brought to the heat-proof design of the high-speed aircraft. As shown in fig. 2, the method of the pulse pressure test is to mount a pulse pressure sensor on the model, the sensor converts the sensed pulse pressure signal into an electrical signal, and the electrical signal is filtered and amplified, and recorded, stored and processed by a data acquisition system. The dynamic data acquisition system used for pulse pressure data acquisition is an acquisition mode which aims at a small number of sensors, generally does not exceed dozens of sensors, but has a high sampling rate, and the sampling rate can reach 1MHz.
In the current wind tunnel test, the measurement of the surface pressure of the model and the measurement of the pulsating pressure are realized by utilizing respective special equipment, namely an electronic pressure scanning valve and a dynamic data acquisition system, to independently complete data acquisition. The acquisition mode has the following four problems:
the electronic pressure scanning valve system for measuring the surface pressure of the model is provided with a plurality of acquisition terminals, each acquisition terminal is provided with a dozen to dozens of acquisition units, and pressure measurement can be simultaneously carried out on nearly a thousand pressure measurement points. All pressure acquisition units on one terminal share one AD (analog-digital) instrument, and when pressure data are acquired, only a serial mode is adopted, and parallel acquisition of multiple paths of pressure data cannot be realized;
secondly, as shown in fig. 3, because tens of pressure acquisition units of the electronic pressure scanning valve share one AD digitizer, the data acquisition mode can only adopt a polling mode, that is, all the pressure acquisition units of the acquisition terminal record pressure data one by one according to the sequence, the data between two adjacent acquisition units has a delay Δ t in time, the more the pressure acquisition units of the terminal are, the greater the delay of the pressure recording time between the first acquisition unit and the last acquisition unit is (n-1) × Δ t, and n is the number of the acquisition units on the terminal. Meanwhile, in order to reduce the random variation error of the pressure data, a plurality of pressure values of the same acquisition unit are averaged to be used as the finally acquired pressure value, and the delay of the pressure recording time between the first acquisition unit and the last acquisition unit is (nk-1) × Δ t. In addition, in order to ensure the real-time performance of data reading and processing, the sampling rate of the electronic pressure measurement is set to be small, and is generally about 100 Hz. At the moment, the data recording time between the pressure acquisition units has an error of a second level, and because the measured pressure in the wind tunnel test is a fluctuation value, the finally acquired pressure data is not a pressure value at the same moment, and a larger error is caused by the delay of the acquisition time.
Thirdly, as shown in fig. 4, the collection trigger signals among the pressure measurement terminals have a network transmission mode and also have a cable transmission mode. Because the delay of the transmission time and the different phases of the clock signals between different acquisition terminals exist, a random acquisition time delay exists between different terminals, and errors are brought to final data.
Fourthly, as shown in fig. 5, because the model surface pressure data acquisition device and the pulsating pressure data acquisition device are independent from each other, the respective acquired data lack a corresponding relationship in time, and the final data analysis only can use the model surface pressure data as a whole reference, and cannot perform time domain correlation analysis on the model surface pressure change and the pulsating pressure change within one wind tunnel test time, and the time domain correlation analysis between the two is a key for extracting the interactive coupling characteristics of the two.
Disclosure of Invention
An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
In order to achieve the purposes and other advantages of the invention, the invention provides a synchronous parallel acquisition system of steady-state pressure and pulse pressure data, which comprises a steady-state pressure measurement subsystem and a pulse pressure measurement subsystem which respectively acquire steady-state pressure and pulse pressure, and is characterized in that at least one acquisition terminal is respectively arranged in the steady-state pressure measurement subsystem and the pulse pressure measurement subsystem, each acquisition unit in each acquisition terminal uses an independent and same-type AD (analog-to-digital) digital instrument and carries out phase locking through a phase-locked loop, and a processor of the AD digital instrument is integrated with a timestamp counter;
the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem provide a phase-locked synchronous clock for each acquisition terminal through matched external synchronous control modules;
and the acquisition terminals of the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem are communicated with the central processing unit through the matched synchronous triggers.
An application method of a synchronous parallel acquisition system for steady-state pressure data and pulsating pressure data applied to a wind tunnel test comprises the following steps:
s10, the synchronous control module provides a phase-locked common clock for each acquisition terminal of the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem so as to ensure that each acquisition unit AD digital instrument is in the same state to be triggered;
s11, the central processing unit sends a trigger instruction to each acquisition terminal through the synchronous trigger, each acquisition terminal sets an acquisition starting point for the AD digitizer of each acquisition unit after receiving the trigger instruction, pressure signal acquisition is started, and the clock frequency of each AD digitizer is locked through a phase-locked loop in the acquisition process;
pressure signals acquired by the AD digital instruments are recorded with the sampling period number of each AD digital instrument before the current synchronous trigger event occurs through a timestamp counter, and trigger time errors among different acquisition terminals are identified and corrected, so that synchronous acquisition of signals in each subsystem is realized;
and S12, the acquisition terminals of the subsystems transmit the acquired pressure signals back to the central processing unit through the concentrator, and the two data are aligned at the same time mark by comparing the time marks of the steady-state pressure data and the pulsating pressure data among the subsystems.
Preferably, the method further comprises the following steps:
s13, the central processing unit carries out flow field structure change and background noise removal on data measured by the steady-state pressure measurement subsystem, and carries out pretreatment on pulsating pressure data measured by the pulsating pressure measurement subsystem;
wherein the preprocessing is configured to analyze and process in three aspects of amplitude domain, time domain and frequency domain.
Preferably, in the amplitude domain processing, the root mean square value P is determined by the pulsating pressure rms Sound pressure level SPL, coefficient of pulsating pressure C prms Describing the total intensity of the pulsating pressure in the measured frequency range, and describing the probability of the instantaneous value of the pulsating pressure falling in a certain specified pressure range through a probability density function PDF;
wherein, the P rms The corresponding formula one is:
in formula one, P (T) represents a pressure signal that varies randomly with time, and T represents a measurement time;
the formula two corresponding to the SPL is as follows:
in formula two, P ref Is a reference pressure;
said C is prms The corresponding formula three is:
in the third formula, q represents the incoming flow velocity pressure;
the formula four corresponding to the PDF is as follows:
in equation four, Δ p represents a pressure increase; t is p Representing the total time during which the instantaneous value of the pulsating pressure falls within the range p to p + deltap during the measurement time T.
Preferably, in the time domain processing, the autocorrelation function R (b) is obtained by
) Or r: (
) Waveform describing a pulsating pressure signal and its time delay
The degree of similarity of the waveforms in time by the cross-correlation function R (
,
) Or r: (
,
) Describing the similarity degree between the pulse pressure signals of two different measuring points;
wherein, R is (A), (B) and (C)
) The corresponding formula five is:
in the formula five, the first and second groups,
represents a time delay;
r: (a)
) The corresponding formula six is:
in the formula six, R (0) represents the value of the autocorrelation function at a time delay of 0;
r is (A), (B) and (C)
,
) The corresponding formula seven is:
in formula seven, p x (t) represents the pulsating pressure signal at point x,
indicating the distance from the point x
At another measuring point of the station is delayed in time
A time-dependent pulsating pressure signal;
r: (a)
,
) The corresponding equation eight is:
in the formula eight, R x (0) And
respectively represent measuring points x and x +
Delay in time of autocorrelation function of the pulsating pressure signal
Value at = 0.
Preferably, in the frequency domain processing, the distribution of the pulsating pressure energy with frequency is described by a power spectral density function G (f);
wherein, the formula nine corresponding to G (f) is:
in equation nine, f represents frequency and Δ f represents a frequency interval.
The invention at least comprises the following beneficial effects: the system can realize synchronous acquisition of steady-state pressure data and pulsating pressure data of different acquisition systems in a wind tunnel test so as to ensure the accuracy and time domain correlation of subsequent data processing.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a schematic diagram of a prior art model surface pressure data acquisition approach;
FIG. 2 is a diagram illustrating a method for acquiring pulsating pressure data according to the prior art;
FIG. 3 is a schematic diagram of the error of the electronic pressure measurement data acquisition delay in the prior art
FIG. 4 is a schematic diagram of the triggering time difference between different acquisition terminals for pressure measurement in the prior art
FIG. 5 is a schematic diagram showing the lack of time-domain correlation between the surface pressure of a model and the collected data of the pulsating pressure in the prior art;
FIG. 6 is a schematic diagram of synchronous data acquisition and preprocessing steps of a steady-state flow field and pulsating pressure in the preprocessing process of the present invention;
FIG. 7 is a block diagram of the system of the present invention;
FIG. 8 is a block diagram of the components of one of the subsystems of the present invention;
FIG. 9 is a schematic diagram of the present invention for synchronously collecting data of different frequencies;
the system comprises a steady-state pressure measurement subsystem-1, a pulsating pressure measurement subsystem-2, an acquisition terminal-10, an acquisition unit-11, an AD (analog-to-digital) instrument-12, a phase-locked loop-13, an external synchronous control module-3 and a central processing unit-4.
Detailed Description
The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
As shown in fig. 7-8, a system for synchronously acquiring steady-state pressure and pulse pressure data comprises a steady-state pressure measurement subsystem 1 and a pulse pressure measurement subsystem 2 which are used for respectively acquiring steady-state pressure on the surface of a model and pulse pressure at a special part, wherein at least one acquisition terminal 10 is respectively arranged in the steady-state pressure measurement subsystem and the pulse pressure measurement subsystem, each acquisition unit 11 in each acquisition terminal uses an independent and same-type AD digital instrument 12 and is phase-locked by a phase-locked loop 13, and a time stamp counter is integrated in a processor of the AD digital instrument;
the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem provide a phase-locked synchronous clock for each acquisition terminal through the matched external synchronous control module 3;
the steady state pressure measurement subsystem, each acquisition terminal of the pulsating pressure measurement subsystem communicate with central processing unit 4 through the synchronous trigger cooperating, the effect of the synchronous trigger, in the multisystem, provide the triggering signal and insert the time stamp mark through the external synchronous control module, realize the phase synchronization of each acquisition terminal among the systems, and to the independent single system inside, each measurement unit in each acquisition terminal all adopts independent, the A/D digital instrument of the same type, realize the phase synchronization among each measurement terminal and measurement unit through synchronous clock and synchronous bus, namely the realization mode that the system of the invention collects synchronously is:
firstly, an independent AD (analog-to-digital) digital instrument with the same type is used by each acquisition unit in each acquisition terminal in a model surface pressure measurement system and a special part pulsating pressure measurement system, and phase locking is carried out through a phase-locked loop, so that the clock frequencies of all the AD digital instruments of the acquisition units are completely consistent, and the phases do not deviate along with time;
secondly, providing a phase-locked synchronous clock for each acquisition terminal of the model surface pressure measurement system and the special part pulsating pressure measurement system through an external synchronous control module to ensure that the AD digital instrument of each acquisition unit in each acquisition terminal of the two systems is in the same state to be triggered;
thirdly, providing a synchronous trigger for each acquisition terminal of the two systems through an external synchronous control module to determine the starting point of the data recorded by the AD digitizer of each acquisition unit in each acquisition terminal;
and fourthly, introducing a time stamp counter into each AD digital instrument, wherein the time stamp counter records the sampling period number of the AD digital instrument in each acquisition unit before the synchronous trigger event occurs, and is used for identifying and correcting the trigger time error among different acquisition units.
And fifthly, comparing the time marks of the model surface pressure data and the pulse pressure data, and aligning the two data at the same time mark. As shown in fig. 9, by adopting the scheme of the present invention, synchronous data acquisition of different frequencies can be effectively realized, and measurement errors are reduced, so that the measurement structure meets the actual test requirements.
In a specific implementation of the steady-state pressure measurement subsystem, each acquisition unit is configured to include:
the pressure sensors are matched with the positions of the points to be measured on the gas path connecting assembly;
the signal conditioning circuit is in communication connection with each pressure sensor to construct a corresponding measuring channel;
the pressure measurement assembly is in communication connection with each first signal conditioning circuit so as to realize synchronous acquisition of each pressure sensor, and the modular design is adopted, so that the interface is expandable and the overall technical index of the system is not influenced;
each acquisition terminal is configured to include:
the pressure measurement machine box (not shown) is used for integrating pressure measurement components, a first controller with an operating system is arranged in the pressure measurement machine box, the pressure measurement components are inserted into the pressure measurement machine box to complete modular integration of pressure measurement, the machine box is a 4U standard rack machine box and is provided with a core controller slot, at most 8 acquisition board cards can be inserted, the first machine box plug-in card adopts a quick-insertion structure, a panel is provided with a locking screw, the board cards can be reinforced to be installed after being screwed, the core controller is a core component of a steady-state pressure measurement system and is equivalent to a CPU and a mainboard of acquisition equipment, and functions of data acquisition management, acquisition instruction sending, data transmission and the like can be completed. The operating system of the core controller is an RT real-time operating system. When the real-time operating system interacts with external data, the real-time operating system can process the data at a high enough speed, the processing result can control the production process or make a quick response to the processing system within a specified time, all available resources are scheduled to complete real-time tasks, and all real-time tasks are controlled to run in a coordinated and consistent mode. Compared with a time-sharing operating system, the system has the advantages of timely response and high reliability. For the data acquisition processing server, the synchronous acquisition component is like a black box, a preset program in the core controller automatically calls and operates a synchronous acquisition function, an acquisition instruction sent by the server is received by adopting a driving program, and acquired data are sent to the data acquisition processing server;
the portable pressure controller mainly outputs a standard pressure to provide a standard pressure source so as to conveniently finish the calibration and troubleshooting work of the pressure measurement module. In the scheme, the parameter indexes of the pressure measurement components need to meet the requirements of a table 1, and the parameter indexes of the pulsating pressure measurement subsystem need to meet the requirements of a table 2, so that the capability of phase synchronization and high-precision acquisition between measurement points and between the pressure measurement components and pulsating pressure data acquisition is achieved;
TABLE 1
TABLE 2
Each pressure measurement assembly is configured to include:
the first FPGA is used for processing and outputting the signals input by the signal conditioning circuit;
the first phase-locked loop PLL is in communication connection with the first FPGA, the first clock management module and the CPU;
the external communication interface, the synchronous clock signal and the synchronous trigger signal are in communication connection with the first clock management module and the CPU through a control bus;
the central processing unit (also referred to as a control unit) is configured to include:
the rack is provided with a front panel with a signal interface;
a second FPGA30 disposed inside the chassis;
the second phase-locked loop PLL is in communication connection with the second FPGA, the second clock management module and the synchronous signal generator;
the control unit is in communication connection with the pressure measurement assemblies and the dynamic data acquisition assemblies through a shunt, the overall structural design of the control unit adopts a 1U rack type structure, a signal interface is configured on a front panel and can be accessed to input and output signals, a synchronization module is in communication with an upper computer through a USB port, hardware equipment in the system adopts an embedded type structure based on FPGA, and the hardware structure based on FPGA and AD has high real-time performance meeting test conditions, so that the acquisition and storage of signals can be realized, and the advantages of strong synchronism, low power consumption, high reliability and the like are achieved; the control unit is used as an external trigger source and synchronously accessed to a plurality of acquisition terminals through a splitter to realize the layout of synchronous triggering of a plurality of devices;
each measuring unit of the scheme adopts a modular design, and the modules have independent functions and are not coupled. The modularized design is easy to expand the system capacity and improve the maintenance efficiency.
The FGPA realizes the operations of data acquisition, data processing, data transmission and the like in the FPGA through a standard PCIe interface. The method is divided into the following steps according to functions: the data exchange system comprises an interface unit, a processing unit, an output unit and the like, wherein a data flow driving mode is adopted among the units, and after the data processing of the unit is completed, the data are packaged and sent to the next level, so that the data exchange is realized inside the framework.
The FPGA design elements comprise interface design, clock design, reset design, function design and the like. The interface design criteria are: excessive logic is not added, and the influence on the interface time sequence after the added logic is jammed is avoided; clocks include logic clocks, interface clocks, memory clocks, and the like. The logic clock depends on the key path of the logic, and the product performance is improved. When the FPGA realizes the synchronous signal time sequence, the synchronous adoption of the interface is realized by adopting a fixed and accurate interface clock. The memory clock realizes the data synchronous cache, and the data loss or instability caused by the refresh frequency is avoided during the design; the internal reset of the FPGA comprises hard reset, logic reset, soft reset and the like. The hard reset is introduced into the external pin and is fed in when the power is on, so that the whole FPGA logic configuration reaches a stable state after being completed. The logic reset is generated by the internal logic of the FPGA and is used for setting the preparation state of signals such as synchronous control and the like. The soft reset is used in the debugging stage, and the soft reset is inserted into the point to be tested, the fault locating point and the like, so that the problem of segmentation can be quickly located, and the debugging speed is accelerated. The function design comprises the functions of signal acquisition, signal conditioning, synchronous control, data transmission and the like through the FPGA. The principle of functional design is stable and efficient, and the required circuit realization function and the constraint conditions for realizing the circuit, such as speed, power consumption, circuit type and the like, are comprehensively considered.
And the further pulsation pressure measurement subsystem is used for measuring dynamically changed data, and the acquisition terminal and the corresponding acquisition unit of the further pulsation pressure measurement subsystem are similar to those of the steady-state pressure measurement subsystem except for the difference of the types of the sensors.
The pressure which changes randomly along with time is called pulsating pressure, many complex flow phenomena such as vortex, separation flow, turbulent flow and the like belong to unsteady flow, quite strong pulsating pressure is generated, and unsteady characteristics of the complex flow phenomena can be revealed through pulsating pressure measurement. It cannot be accurately described by mathematical expressions, has no instantaneous rules, and is only processed and analyzed according to the statistical rules. As shown in FIG. 6, the invention performs the pre-processing of the pulsating pressure data from three aspects of amplitude domain, time domain and frequency domain. The processed data provides basis for extracting the characteristics of the pulsating pressure change brought by the state change of the model and the state change of the flow field, and particularly provides data support for the correlation characteristic analysis of the static pressure change and the pulsating pressure change in the time domain.
1. In the amplitude domain processing method, the root mean square value P is obtained through the pulsating pressure in the amplitude domain processing rms Sound pressure level SPL, coefficient of pulsating pressure C prms Describing the total intensity of the pulsating pressure in the measured frequency range, and describing the probability of the instantaneous value of the pulsating pressure falling in a certain specified pressure range through a probability density function PDF;
wherein, the P rms The corresponding formula one is:
in formula one, P (T) represents a pressure signal that varies randomly with time, and T represents a measurement time;
the formula two corresponding to the SPL is as follows:
in formula two, P ref Is a reference pressure;
said C is prms The corresponding formula three is:
in the third formula, q represents the incoming flow velocity pressure;
the formula four corresponding to the PDF is as follows:
in equation four, Δ p represents a pressure increase; t is p Representing the total time during which the instantaneous value of the pulsating pressure falls within the range p to p + deltap during the measurement time T.
2. The time domain processing method comprises the following main statistical functions of the time domain:
(1) An autocorrelation function R: (
) Describing the waveform and time delay of a pulsating pressure signal
The degree of similarity of the time waveforms, sometimes by the autocorrelation coefficient r (m:)
) And (4) showing.
In the formula:
represents the time delay, and R (0) represents the value of the autocorrelation function at a time delay of 0.
(2) A cross-correlation function R: (
, 
)
In the formula:
a pulsating pressure signal representing the measuring point x;
indicating the distance from the point x
At another measuring point of the station is delayed in time
The pulsating pressure signal of time.
The cross-correlation coefficient describes the similarity degree between pulse pressure signals of two different measuring points or is called the correlation degree, and sometimes the cross-correlation coefficient r (R: (R))
, 
) Represents:
R x (0) And
respectively represent measuring points x and x +
Delay in time of autocorrelation function of the pulsating pressure signal
Value at = 0.
3. In the frequency domain processing method, the main statistical function of the frequency domain is mainly to analyze the pulsating pressure signal in the frequency domain, which is generally called spectral analysis, and the analysis result is spectral lines and curves of various physical quantities with the abscissa as the frequency.
The power spectral density function G (f), describes the distribution of the pulsating pressure energy with frequency.
In the formula: f denotes frequency, and Δ f denotes a frequency interval.
The above scheme is merely illustrative of a preferred example, and is not limiting. When the invention is implemented, appropriate replacement and/or modification can be carried out according to the requirements of users.
The number of apparatuses and the scale of the process described herein are intended to simplify the description of the present invention. Applications, modifications and variations of the present invention will be apparent to those skilled in the art.
While embodiments of the invention have been disclosed above, it is not intended to be limited to the uses set forth in the specification and examples. It can be applied to all kinds of fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. Therefore, the invention is not to be limited to the specific details and illustrations shown and described herein, without departing from the general concept as defined by the claims and their equivalents.
Claims (3)
1. A synchronous parallel acquisition system of steady-state pressure and pulsating pressure data comprises a steady-state pressure measurement subsystem and a pulsating pressure measurement subsystem which are used for respectively acquiring steady-state pressure and pulsating pressure, and is characterized in that the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem are respectively provided with at least one acquisition terminal, each acquisition unit in each acquisition terminal uses an independent and same-type AD (analog-to-digital) digitizer and is phase-locked by a phase-locked loop, and a processor of the AD digitizer is integrated with a timestamp counter;
the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem provide a phase-locked synchronous clock for each acquisition terminal through matched external synchronous control modules;
and the acquisition terminals of the steady-state pressure measurement subsystem and the pulsation pressure measurement subsystem are communicated with the central processing unit through the matched synchronous triggers.
2. A method for using the synchronous and parallel acquisition system of the steady-state pressure and the pulsating pressure data as claimed in claim 1, which comprises:
s10, the external synchronous control module provides a phase-locked common clock for each acquisition terminal of the steady-state pressure measurement subsystem and the pulsating pressure measurement subsystem so as to ensure that each acquisition unit AD digital instrument is in the same state to be triggered;
s11, the central processing unit sends a trigger instruction to each acquisition terminal through the synchronous trigger, each acquisition terminal sets an acquisition starting point for the AD digitizer of each acquisition unit after receiving the trigger instruction, pressure signal acquisition is started, and the clock frequency of each AD digitizer is locked through a phase-locked loop in the acquisition process;
the pressure signals acquired by each AD digital instrument record the sampling period number of each AD digital instrument before the current synchronous trigger event occurs through a timestamp counter, and trigger time errors among different acquisition terminals are identified and corrected, so that synchronous acquisition of signals in each subsystem is realized;
and S12, the acquisition terminals of the subsystems transmit the acquired pressure signals back to the central processing unit through the concentrator, and the two data are aligned at the same time mark position by comparing the time marks of the steady-state pressure data and the pulsating pressure data among the subsystems.
3. The method for applying the synchronous and parallel acquisition system of the steady-state pressure and the pulse pressure data as claimed in claim 2, further comprising:
s13, the central processing unit carries out flow field structure change and background noise removal on data measured by the steady-state pressure measurement subsystem, and carries out pretreatment on pulsating pressure data measured by the pulsating pressure measurement subsystem;
wherein the preprocessing is configured to analyze and process in three aspects of amplitude domain, time domain and frequency domain;
in amplitude domain processing, the root mean square value P is obtained by the pulsating pressure rms Sound pressure level SPL, coefficient of pulsating pressure C prms Describing the total intensity of the pulsating pressure in the measured frequency range, and describing the probability of the instantaneous value of the pulsating pressure falling in a certain specified pressure range through a probability density function PDF;
wherein, the P rms The corresponding formula one is:
in formula one, P (T) represents a pressure signal that varies randomly with time, and T represents a measurement time;
the formula two corresponding to the SPL is as follows:
in formula two, P ref Is a reference pressure;
said C is prms The corresponding formula three is:
in the formula III, q represents the incoming flow velocity pressure;
the formula four corresponding to the PDF is as follows:
in equation four, Δ p represents a pressure increase; t is p Represents the total time during which the instantaneous value of the pulsating pressure falls within the range of p to p + Δ p during the measurement time T;
in the time domain processing, the similarity degree of the waveform of a pulse pressure signal and the waveform of the pulse pressure signal at the time delay tau is described through an autocorrelation function R (tau) or R (tau), and the similarity degree between pulse pressure signals at two different measuring points is described through a cross-correlation function R (epsilon, tau) or R (epsilon, tau);
wherein, the formula five corresponding to the R (tau) is:
；
in formula five, τ represents a time delay;
the formula six corresponding to r (τ) is:
in formula six, R (0) represents the value of the autocorrelation function at a time delay of 0;
the formula seven corresponding to the R (epsilon, tau) is as follows:
in formula seven, p x (t) represents the pulsating pressure signal at point x,
representing the pulsating pressure signal at a time delay tau of another measuring point which is at a distance epsilon from the measuring point x;
the formula eight corresponding to r (epsilon, tau) is:
in the formula eight, R x (0) And
values of autocorrelation functions of the pulsating pressure signals at the measuring points x and x + τ, respectively, at a time delay τ = 0;
in the frequency domain processing, the distribution of the pulse pressure energy along with the frequency is described by a power spectral density function G (f);
wherein, the formula nine corresponding to G (f) is:
in equation nine, f represents frequency and Δ f represents a frequency interval.
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