CN102360024A

CN102360024A - Paper pulp flow velocity and flow measuring method

Info

Publication number: CN102360024A
Application number: CN 201110245185
Authority: CN
Inventors: 周强; 任鹏; 王莹; 袁文婷; 徐立鑫
Original assignee: Shaanxi University of Science and Technology
Current assignee: Shaanxi University of Science and Technology
Priority date: 2011-08-24
Filing date: 2011-08-24
Publication date: 2012-02-22

Abstract

The invention relates to a method for measuring pulp flow velocity and flow rate. In the method, two concentration sensors connected in series on pipelines are used to calculate the pulp flow velocity while measuring the pulp concentration. Due to the fluctuation and continuity of the pulp concentration signal, the current pulp flow velocity and flow rate can be accurately calculated through the cross-correlation analysis of the concentration signals output by the two concentration sensors. The method of the invention has the advantage of high measurement accuracy.

Description

A method for measuring pulp flow velocity and flow

技术领域 technical field

本发明涉及轻化工和测量技术领域，尤其涉及一种纸浆流速及流量的测量方法。The invention relates to the field of light chemical industry and measurement technology, in particular to a method for measuring pulp flow velocity and flow.

背景技术 Background technique

在造纸工业中，纸浆的速度流量是测量最多的物理量，纸浆流速的测量对于造纸生产线上的打浆、洗浆、计量、炒纸等几乎所有环节都有重要意义，目前，电磁流量计、数字图像技术(DIT)、超声波脉冲多普勒法(PUD)、核磁共振(NMR)法等多种方法被用于纸浆流速的测量。不过，生产中使用最多的电磁流量计测量精度较低仅能达到1％，超声波脉冲多普勒法(PUD)仅适于低浓度(0.5％)的测量，而数字图像技术(DIT)不适于在线使用，而核磁共振(NMR)法的价格过于昂贵。因此，以上方法都不适合为造纸生产线提供标准纸浆流速。In the paper industry, the velocity and flow of pulp is the most measured physical quantity. The measurement of pulp flow is of great significance to almost all links in the paper production line, such as beating, washing, metering, and frying. At present, electromagnetic flowmeters, digital image Various methods such as DIT, ultrasonic pulsed Doppler (PUD), nuclear magnetic resonance (NMR) are used to measure pulp flow velocity. However, the most widely used electromagnetic flowmeter in production has a low measurement accuracy of only 1%. Ultrasonic pulse Doppler method (PUD) is only suitable for low concentration (0.5%) measurement, while digital image technology (DIT) is not suitable for available online, and nuclear magnetic resonance (NMR) methods are prohibitively expensive. Therefore, none of the above methods is suitable for providing standard pulp flow rates for paper production lines.

在造纸生产中，纸浆浓度被测量数量仅次于纸浆流速，这两个参数往往被同时测量，而且纸浆浓度的测量技术相当成熟，因此在原来1台浓度传感器的基础上，再添加1台浓度可用于纸浆流速的高精度测量。In papermaking production, the number of measured pulp concentration is second only to pulp flow rate. These two parameters are often measured at the same time, and the measurement technology of pulp concentration is quite mature. Therefore, on the basis of the original concentration sensor, add another concentration sensor. It can be used for high-precision measurement of pulp flow rate.

发明内容 Contents of the invention

本发明的目的在于提供一种能精确测量出纸浆实时流速及流量的纸浆流速及流量的测量方法。The purpose of the present invention is to provide a method for measuring pulp flow velocity and flow that can accurately measure the real-time flow velocity and flow of pulp.

为达到上述目的，本发明提供一种纸浆流速及流量的测量方法，所述的测量方法按照以下步骤进行：In order to achieve the above object, the present invention provides a kind of measuring method of pulp velocity and flow rate, and described measuring method is carried out according to the following steps:

步骤1)：通过设置在纸浆管道上的相邻的第一浓度传感器和第二浓度传感器分别获得离散的采样浓度信号C_A(n)和C_B(n)；其中n代表时间t的离散量(n＝1，2，…N)，C_A(n)代表第一浓度计在n时刻测量到的浓度值，C_B(n)代表第二浓度计在n时刻测量到得浓度值；Step 1): Obtain discrete sampling concentration signals _CA (n) and C _B (n) respectively by adjacent first concentration sensors and second concentration sensors arranged on the pulp pipeline; where n represents the discrete quantity of time t (n=1, 2, ... N), _CA (n) represents the concentration value measured by the first concentration meter at n moments, and C _B (n) represents the concentration values measured by the second concentration meter at n moments;

步骤2)：根据公式(1)和(2)分别计算采样浓度信号C_A(n)和C_B(n)的离散傅立叶变换C_A(k)、C_B(k)：Step 2): Calculate the discrete Fourier transforms _CA (k) and C _B (k) of the sampled concentration signals CA (n) and C _B (n) respectively according to formulas (1) and ( ₂ ):

C_A(k)＝FFT[C_A(n)] (1)；C _A (k) = FFT [C _A (n)] (1);

C_B(k)＝FFT[C_B(n)] (2)；C _B (k) = FFT[C _B (n)] (2);

其中k是离散频率，代表频谱自变量的离散量；Among them, k is the discrete frequency, which represents the discrete quantity of the independent variable of the spectrum;

步骤3)：根据公式(3)，由步骤2)获得的C_A(k)、C_B(k)计算采用浓度信号的功率谱S_AB(k)：Step 3): According to the formula (3), the power spectrum S _AB (k) of the concentration signal is calculated from _CA (k) and C _B (k) obtained in step 2):

${S S}_{AB AB} ((k k)) = = \frac{{C C}_{A A} ((k k)) {\overset{&OverBar; &OverBar;}{C C}}_{B B} ((k k))}{N N} - - - - - - ((33));;$

步骤4)：根据公式(4)，通过功率谱S_AB(k)的离散傅立叶逆变换计算C_A(n)、C_B(n)的相关函数R_AB(τ)：Step 4): Calculate the correlation function R AB (τ) of C _A (n) and C _B (n) through the inverse discrete Fourier transform of the power spectrum S _AB (k) according to _formula (4):

R_AB(τ)＝IFFT|S_AB(k)| (4)；R _AB (τ) = IFFT | S _AB (k) | (4);

步骤5)：根据公式(5)求出R_AB(τ)的最大值R_ABmax(τ)及其对应的渡越时间τ，Step 5): Calculate the maximum value R _ABmax (τ) of R _AB (τ) and its corresponding transit time τ according to formula (5),

R_ABmax(τ)＝max[R_AB(τ)] (5)；R _ABmax (τ) = max[R _AB (τ)] (5);

其中渡越时间τ即管道中纸浆由浓度计A流到浓度计B所用的时间；The transit time τ is the time it takes for the pulp in the pipeline to flow from the concentration meter A to the concentration meter B;

步骤6)：将τ代入公式(6)，可获得纸浆实时流速v；将τ代入公式(2)可获得纸浆实时流量F：Step 6): Substituting τ into formula (6) can obtain the real-time pulp flow velocity v; substituting τ into formula (2) can obtain the real-time pulp flow F:

$v v = = \frac{L L}{τ τ} - - - - - - ((66));;$

$F f = = \frac{LS LS}{τ τ} - - - - - - ((77));;$

其中L为相邻的两个浓度传感器之间的管道长度；S是管道的横截面积。Among them, L is the pipeline length between two adjacent concentration sensors; S is the cross-sectional area of the pipeline.

优选的，所述相邻的两个浓度传感器的前后应至少有1米的直管道。Preferably, there should be at least 1 meter of straight pipes before and after the two adjacent concentration sensors.

优选的，所述相邻的两个浓度传感器之间的管道长度L满足：1m＜L＜2.5m。Preferably, the pipeline length L between two adjacent concentration sensors satisfies: 1m<L<2.5m.

本发明所述的纸浆流速及流量的测量方法，利用两台串联在管道上的浓度传感器在测量纸浆浓度的同时计算纸浆流速。由于纸浆浓度信号具有波动性和波动的持续性，通过对两台浓度传感器输出的浓度信号进行互相关分析，能够精确地计算出当前纸浆流速。该方法通过对纸浆浓度信号的互相关分析获得纸浆流经固定距离所需时间，进而获得纸浆的实时流速。本发明所述的方法具有测量精度极高(测量精度可达0.2％)的优点，不仅可以用于工业现场中，还能够作为一种标准流量计用于标定其它传感器。The method for measuring pulp flow velocity and flow rate of the present invention uses two concentration sensors connected in series on the pipeline to calculate the pulp flow velocity while measuring the pulp concentration. Because the pulp concentration signal has fluctuation and continuity of fluctuation, the current pulp flow rate can be accurately calculated by performing cross-correlation analysis on the concentration signals output by two concentration sensors. The method obtains the time required for the pulp to flow through a fixed distance through the cross-correlation analysis of the pulp concentration signal, and then obtains the real-time flow velocity of the pulp. The method of the invention has the advantage of extremely high measurement accuracy (the measurement accuracy can reach 0.2%), and can not only be used in industrial fields, but also be used as a standard flowmeter for calibrating other sensors.

附图说明 Description of drawings

图1是符合本发明的纸浆流速及流量的测量方法的原理图；Fig. 1 is the schematic diagram of the measuring method of pulp flow velocity and flow rate consistent with the present invention;

图2是纸浆流速及流量的测量方法的纸浆浓度的分析图；其中图(a)是图1中的浓度传感器1输出的浓度信号C_A的波形图；图(b)是图1中的浓度传感器2输出的浓度信号C_B的波形图；图(c)是对浓度信号C_A和C_B的分析结果示意图。Fig. 2 is the analytical diagram of the pulp concentration of the measuring method of pulp flow velocity and flow; Wherein figure (a) is the waveform diagram of the concentration signal _CA of concentration sensor 1 output among Fig. 1; Fig. (b) is the concentration among Fig. 1 Waveform diagram of the concentration signal C _B output by the sensor 2; Figure (c) is a schematic diagram of the analysis results of the concentration signals _CA and C _B.

具体实施方式 Detailed ways

请参照图1，整个测量系统包括安装在纸浆管道上距离为L的第一浓度传感器1、第二浓度传感器2、以及与第一浓度传感器1和第二浓度传感器2连接的二次仪表3。由于本发明所述的方法对微处理器的运算能力要求很高，所以二次仪表3是以DSP为核心的。第一浓度传感器1和第二浓度传感器2的前后应至少有1米的直管道。第一浓度传感器1和第二浓度传感器2之间的管道长度L满足：1m≤L≤2.5m。Please refer to FIG. 1 , the entire measurement system includes a first concentration sensor 1 installed at a distance L on a pulp pipeline, a second concentration sensor 2 , and a secondary instrument 3 connected to the first concentration sensor 1 and the second concentration sensor 2 . Since the method of the present invention requires very high computing power of the microprocessor, the secondary instrument 3 is based on DSP. There should be at least 1 meter of straight pipes before and after the first concentration sensor 1 and the second concentration sensor 2. The pipeline length L between the first concentration sensor 1 and the second concentration sensor 2 satisfies: 1m≤L≤2.5m.

符合本发明的纸浆流速及流量的测量方法，按照以下步骤进行：Conform to the measuring method of pulp velocity of the present invention and flow, carry out according to the following steps:

第一步：将第一浓度传感器和第二浓度传感器距离一定距离设置在纸浆管道上，通过该第一浓度传感器和第二浓度传感器分别获得离散的采样浓度信号C_A(n)和C_B(n)。其中n代表时间t的离散量(n＝1，2，…N)，C_A(n)代表第一浓度传感器在n时刻测量的浓度值，C_B(n)代表第二浓度传感器在n时刻测量的浓度值。The first step: the first concentration sensor and the second concentration sensor are arranged on the pulp pipeline at a certain distance, and the discrete sampling concentration signals C _A (n) and C _B ( n). Where n represents the discrete quantity of time t (n=1, 2, ... N), C _A (n) represents the concentration value measured by the first concentration sensor at time n, and C _B (n) represents the concentration value measured by the second concentration sensor at time n The measured concentration value.

第二步：根据公式(1)和(2)分别计算采样浓度信号C_A(n)和C_B(n)的离散傅立叶变换C_A(k)、C_B(k)：Step 2: Calculate the discrete Fourier transforms C _A (k) and C _B (k) of the sampled concentration signals C _A (n) and C _B (n) respectively according to formulas (1) and (2):

C_A(k)＝FFT[C_A(n)] (1)；C _A (k) = FFT [C _A (n)] (1);

C_B(k)＝FFT[C_B(n)] (2)；C _B (k) = FFT[C _B (n)] (2);

其中k是离散频率，代表频谱自变量的离散量。Among them, k is the discrete frequency, which represents the discrete quantity of the independent variable of the spectrum.

第三步：根据公式(3)，由步骤2)获得的C_A(k)、C_B(k)计算采用浓度信号的功率谱S_AB(k)：The third step: according to formula (3), calculate the power spectrum S _AB (k) using the concentration signal from _CA (k) and C _B (k) obtained in step 2):

${S S}_{AB AB} ((k k)) = = \frac{{C C}_{A A} ((k k)) {\overset{&OverBar; &OverBar;}{C C}}_{B B} ((k k))}{N N} - - - - - - ((33)) . .$

第四步：根据公式(4)，通过功率谱S_AB(k)的离散傅立叶逆变换计算C_A(n)、C_B(n)的相关函数R_AB(τ)：Step 4: Calculate the correlation function R AB ₍ τ) of C _A (n) and C _B (n) through the inverse discrete Fourier transform of the power spectrum S _AB (k) according to formula (4):

R_AB(τ)＝IFFT|S_AB(k)| (4)。R _AB (τ) = IFFT | S _AB (k) | (4).

第五步：根据公式(5)求出R_AB(τ)的最大值R_ABmax(τ)及其对应的渡越时间τ，Step 5: Calculate the maximum value R _ABmax (τ) of R _AB (τ) and its corresponding transit time τ according to the formula (5),

R_ABmax(τ)＝max[R_AB(τ)] (5)；R _ABmax (τ) = max[R _AB (τ)] (5);

其中渡越时间τ即管道中纸浆由浓度计A流到浓度计B所用的时间。The transit time τ is the time it takes for the pulp in the pipeline to flow from the concentration meter A to the concentration meter B.

第六步：将τ代入公式(6)，可获得纸浆实时流速v；将τ代入公式(7)可获得纸浆实时流量F：Step 6: Substituting τ into formula (6) can obtain the real-time pulp flow velocity v; substituting τ into formula (7) can obtain the real-time pulp flow F:

$v v = = \frac{L L}{τ τ} - - - - - - ((66));;$

$F f = = \frac{LS LS}{τ τ} - - - - - - ((77));;$

本发明的理论依据是：The theoretical basis of the present invention is:

①浓度传感器输出的纸浆浓度信号c(t)包含平均浓度信号d(t)、系统噪声s(t)和量测噪声v(t)两部分，即可表示为公式(8)：① The pulp concentration signal c(t) output by the concentration sensor includes two parts: the average concentration signal d(t), the system noise s(t) and the measurement noise v(t), which can be expressed as formula (8):

c(t)＝d(t)+s(t)+v(t) (8)；c(t)＝d(t)+s(t)+v(t) (8);

由于s(t)的存在使得纸浆浓度信号具有波动性。Due to the existence of s(t), the pulp consistency signal has volatility.

②纸浆浓度的波动规律，可以在纸浆管道中长时间的存在，由图2可见，图2(b)是第二浓度传感器2输出的浓度信号C_B的波形图；图2(a)是第一浓度传感器1输出的浓度信号C_A的波形图。将图2(b)和图2(a)进行比较可知第二浓度传感器2输出的浓度信号C_B与第一传感器输出的浓度信号C_A具有相同的波动形状，只是滞后了时间τ，而τ正是纸浆流经两个浓度传感器所用的时间，即渡越时间。τ可以通过相关分析获得。由图2(c)可见C_A和C_B的互相关函数R_AB(τ)的峰值对应的时刻τ恰好是纸浆的渡越时间。将渡越时间代入公式(6)和(7)中：2. The fluctuation law of the pulp concentration can exist in the pulp pipeline for a long time, as can be seen from Fig. 2, Fig. 2 (b) is the waveform diagram of the concentration signal C _B output by the second concentration sensor 2; Fig. 2 (a) is the first A waveform diagram of the concentration signal _CA output by the concentration sensor 1 . Comparing Fig. 2(b) with Fig. 2(a), we can see that the concentration signal C _B output by the second concentration sensor 2 has the same fluctuation shape as the concentration signal _CA output by the first sensor, but it is delayed by time τ, and τ It is the time it takes for the pulp to flow through the two consistency sensors, the transit time. τ can be obtained by correlation analysis. It can be seen from Fig. 2(c) that the time τ corresponding to the peak value of the cross-correlation function R _AB (τ) of _CA and C _B is exactly the transit time of pulp. Substituting transit times into equations (6) and (7):

$v v = = \frac{L L}{τ τ} - - - - - - ((66));;$

$F f = = \frac{LS LS}{τ τ} - - - - - - ((77));;$

即可计算出纸浆的流速v和流量F，其中S是管道的横截面积。The flow velocity v and flow F of the pulp can be calculated, where S is the cross-sectional area of the pipeline.

下面是使用本专利的方法测量生产线上的纸浆流速的一个具体实施例，在本实施例中，第一浓度传感器和第二浓度传感器均为XDBN-1000浓度传感器，浓度测量精度为0.5％。该两浓度传感器之间的距离为1.5米。该纸浆管道内的真实纸浆流速为0.8167m/s。根据本专利方法测的渡越时间τ＝1.8337m，计算出纸浆流速为0.8181m/s，测量误差为0.17％。而根据现有技术的测试方法，使用电磁流量计测得的流量为25.4466L/s，换算成流速是0.8104m/s，测量误差为0.65％。从对比可知，使用本专利的方法的测试精度远远高于使用电磁流量计测得的数据。The following is a specific embodiment of using the method of this patent to measure the pulp flow rate on the production line. In this embodiment, both the first concentration sensor and the second concentration sensor are XDBN-1000 concentration sensors, and the concentration measurement accuracy is 0.5%. The distance between the two concentration sensors is 1.5 meters. The real pulp flow velocity in this pulp pipeline is 0.8167m/s. According to the transit time τ=1.8337m measured by the patented method, the pulp flow velocity is calculated to be 0.8181m/s, and the measurement error is 0.17%. However, according to the testing method of the prior art, the flow rate measured by the electromagnetic flowmeter is 25.4466 L/s, which is converted into a flow rate of 0.8104 m/s, and the measurement error is 0.65%. It can be seen from the comparison that the test accuracy of the method of this patent is much higher than the data measured by the electromagnetic flowmeter.

Claims

1. a measuring method of pulp flow velocity and flow rate, is characterized in that: described measuring method is carried out according to the following steps:

Step 1): The first concentration sensor and the second concentration sensor are arranged on the pulp pipeline at a certain distance, and the discrete sampling concentration signals C _A (n) and C _B ( n); where n represents the discrete quantity of time t (n=1, 2, ... N), C _A (n) represents the concentration value measured by the first concentration sensor at time n, and C _B (n) represents the second concentration sensor The concentration value measured at time n;

Step 2): The secondary instrument receives the sampling concentration signals C _A (n) and C B (n) obtained in step 1), and calculates the sampling concentration signals C A (n) and _C _B (n) according to formulas (1) and (2) respectively Discrete Fourier transform C _A (k), C _B (k) of C _B (n):

C _A (k) = FFT [C _A (n)] (1);

C _B (k) = FFT[C _B (n)] (2);

Among them, k is the discrete frequency, which represents the discrete quantity of the independent variable of the spectrum;

Step 3): According to the formula (3), the power spectrum S _AB (k) of the concentration signal is calculated from _CA (k) and C _B (k) obtained in step 2):

{S S}_{AB AB} ((k k)) = = \frac{{C C}_{A A} ((k k)) {\overset{&OverBar; &OverBar;}{C C}}_{B B} ((k k))}{N N} - - - - - - ((33));;

Step 4): Calculate the correlation function R AB (τ) of C _A (n) and C _B (n) through the inverse discrete Fourier transform of the power spectrum S _AB (k) according to _formula (4):

R _AB (τ) = IFFT | S _AB (k) | (4);

Step 5): Calculate the maximum value R _ABmax (τ) of R _AB (τ) and its corresponding transit time τ according to formula (5),

R _ABmax (τ) = max[R _AB (τ)] (5);

The transit time τ is the time it takes for the pulp in the pipeline to flow from the concentration meter A to the concentration meter B;

Step 6): Substituting τ into formula (6) can obtain the real-time pulp flow velocity v; substituting τ into formula (2) can obtain the real-time pulp flow F:

v v = = \frac{L L}{τ τ} - - - - - - ((66));;

F f = = \frac{LS LS}{τ τ} - - - - - - ((77));;

Among them, L is the pipeline length between two adjacent concentration sensors; S is the cross-sectional area of the pipeline.

2. The method for measuring pulp velocity and flow according to claim 1, characterized in that: there should be at least 1 meter of straight pipes before and after the first concentration sensor and the second concentration sensor.

3. The method for measuring pulp flow velocity and flow rate according to claim 1, characterized in that: the length L of the pipeline between the first concentration sensor and the second concentration sensor satisfies: 1m≤L≤2.5m.