Coal-fired unit condensate flow measurement system

Abstract

The application discloses a coal-fired unit condensate flow measuring system and relates to the technical field of coal-fired units. The system comprises a coal-fired unit condensate pipeline, an ultrasonic flowmeter and an orifice plate flowmeter arranged on the coal-fired unit condensate pipeline, and the ultrasonic flowmeter is arranged upstream of the orifice plate flowmeter. The final measurement value is obtained by weighted summation of the measurement values of the ultrasonic flowmeter and the orifice plate flowmeter. The ultrasonic flowmeter and the orifice plate flowmeter are used as two independent and complete flow measuring devices, which are arranged in series along the fluid flow direction on the same pipeline. The two devices independently operate in the physical space and complementarily function, so that the wide-load full-working-condition high-precision measurement coverage is realized.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power unit technology, and in particular to a condensate flow measurement system for coal-fired power units. Background Technology

[0002] As the installed capacity of new energy power generation such as wind power and photovoltaics continues to rise, the inherent randomness and intermittency of their output are forcing a sharp increase in the demand for flexible adjustment resources from the power grid. Traditional coal-fired power generating units are transforming from the main power source to a basic guarantee and flexible adjustment power source, with long-term low-load operation and frequent deep peak shaving becoming the norm. Currently, the flow monitoring of the condensate system of the unit generally relies on the differential pressure signal generated by the orifice plate flowmeter for calculation. However, the differential pressure value output by the orifice plate flowmeter, which is based on the throttling principle, has a square root relationship with the flow rate, resulting in an extremely narrow dynamic range of the signal over a wide load operating range. When the unit is deeply shaving to a low-load condition, the weak differential pressure signal is easily submerged in the zero drift of the transmitter and the disturbance of the pressure tapping pipeline, posing a fundamental challenge to the accurate measurement of condensate flow under all operating conditions. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a condensate flow measurement system for coal-fired power units, solving the technical problem of how to achieve accurate measurement of condensate flow under all operating conditions.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0005] This invention provides a condensate flow measurement system for a coal-fired power unit, including a condensate pipeline of the coal-fired power unit and an ultrasonic flow meter and an orifice plate flow meter installed on the condensate pipeline of the coal-fired power unit, wherein the ultrasonic flow meter is installed upstream of the orifice plate flow meter; the final measurement value is obtained by weighted summation of the measurement values ​​of the ultrasonic flow meter and the orifice plate flow meter.

[0006] Optionally, the orifice plate flow meter is made of stainless steel and undergoes calibration to ensure that its measurement accuracy under the design flow conditions is ≤0.3%.

[0007] Optionally, the ultrasonic flow meter is a pipe-section type multi-channel ultrasonic flow meter made of stainless steel, and is calibrated to ensure that its measurement accuracy under the design flow conditions is ≤0.5%.

[0008] Optionally, the distance between the ultrasonic flow meter and the orifice plate flow meter is ≥10*DN, where DN is the inner diameter of the condensate pipe of the coal-fired unit.

[0009] Optionally, the condensate pipes of the coal-fired unit are made of stainless steel.

[0010] Optionally, a stainless steel rectifier is provided downstream of the orifice plate flow meter, and the distance between the rectifier and the orifice plate flow meter is ≥16*DN, where DN is the inner diameter of the condensate pipe of the coal-fired unit.

[0011] Optionally, both the ultrasonic flow meter and the orifice plate flow meter are installed on the condensate pipeline of the coal-fired unit via flanges.

[0012] Optionally, the weighted summation to obtain the final measurement value F is:

[0013] L(t) = W ultrasonic (t-1)×L ultrasonic (t) + W orifice (t-1) × L orifice (t)

[0014] In the formula, W ultrasonic W orifice The weights of the ultrasonic flow meter and the orifice plate flow meter, respectively, L ultrasonic L orifice , respectively, are the measured values ​​from the ultrasonic flow meter and the orifice plate flow meter, where t is time;

[0015] If L(t-1) < L1, then W ultrasonic (t-1)=1, W orifice (t-1) = 0;

[0016] If L(t-1) > L2, then W ultrasonic (t-1)=0, W orifice (t-1) = 1;

[0017] If L1≤L(t-1)≤L2, then when L(t-1) changes from L1 to L2, W ultrasonic (t-1) shows a negative correlation in the interval (0,1), W orifice (t-1) shows a positive correlation in the interval (0,1);

[0018] Among them, W ultrasonic (t-1) + W orifice (t-1) = 1, and L1 and L2 are the first flow threshold and the second flow threshold.

[0019] Optionally, the weighted summation to obtain the final measurement value F is:

[0020] L(t) = W ultrasonic (t)×L ultrasonic (t) + W orifice (t) × L orifice (t)

[0021] In the formula, W ultrasonicW orifice The weights of the ultrasonic flow meter and the orifice plate flow meter, respectively, L ultrasonic L orifice , respectively, are the measured values ​​from the ultrasonic flow meter and the orifice plate flow meter, where t is time;

[0022] If P(t) < P1, then W ultrasonic (t) = 1, W orifice (t) = 0;

[0023] If P(t) > P2, then W ultrasonic (t) = 0, W orifice (t) = 1;

[0024] If P1 ≤ P(t) ≤ P2, then when P(t) changes from P1 to P2, W ultrasonic (t) shows a negative correlation in the interval (0,1), W orifice (t) shows a positive correlation in the interval (0,1);

[0025] Among them, W ultrasonic (t-1) + W orifice (t-1)=1, P1 and P2 are the first load threshold and the second load threshold, and P is the unit load of the coal-fired unit.

[0026] Optionally, the negative correlation change or the positive correlation change is a linear change or a non-linear smooth change.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0028] This invention provides a condensate flow measurement system for coal-fired power units, which integrates a multi-channel ultrasonic flow meter and an orifice plate flow meter as two independent and complete flow measurement devices, arranged in series along the fluid flow direction on the same pipeline. The two operate independently in physical space but complement each other functionally, achieving high-precision measurement coverage across a wide range of loads and operating conditions. Furthermore, weighted summation significantly improves flow field adaptability and anti-interference capabilities. The two independent flow meters can compare their measurements, providing online cross-verification and self-diagnosis capabilities. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the condensate flow measurement system for a coal-fired power unit provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the sigmoid function curve provided in an embodiment of the present invention;

[0031] The diagram is marked as follows:

[0032] 1. Condensate pipeline of coal-fired power unit; 2. Ultrasonic flow meter; 3. Orifice plate flow meter; 4. Rectifier. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0034] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment of the invention provides a condensate flow measurement system for a coal-fired power unit, including a condensate pipeline 1 of the coal-fired power unit and an ultrasonic flow meter 2 and an orifice plate flow meter 3 installed on the condensate pipeline 1 of the coal-fired power unit. The ultrasonic flow meter 2 is installed upstream of the orifice plate flow meter 3. The final measurement value is obtained by weighted summation of the measurement values ​​of the ultrasonic flow meter 2 and the orifice plate flow meter 3.

[0038] Orifice plate flowmeter 3: In medium-to-high load (high Reynolds number) regions, its measurement is accurate and stable, and it has been widely accepted and applied as an industry standard. Its advantageous measurement area can be covered without changing the original design and operating habits.

[0039] Ultrasonic flow meter 2: Its core advantages lie in its high accuracy at low flow rates and its extremely wide range ratio. It can perfectly compensate for the measurement shortcomings of orifice plates in low-load areas.

[0040] This embodiment provides dual measurement channels by connecting the orifice plate flow meter 3 and the ultrasonic flow meter 2 in series, thus creating hardware redundancy in the measurement system. If either one fails, the other can still provide valid flow data, greatly improving the reliability and safety of the measurement system.

[0041] In measurement areas where both the orifice plate flowmeter 3 and the ultrasonic flowmeter 2 are functioning normally (such as medium load areas), their measured values ​​can be compared in real time. This continuous cross-validation can be used for:

[0042] Fault diagnosis: When there is a large, unexplained deviation between the readings of the two devices, the system can automatically alarm, indicating that the orifice plate flow meter 2 and / or ultrasonic flow meter 3 may be faulty.

[0043] Performance degradation monitoring: It can monitor the characteristic drift of the orifice plate due to wear or scaling, or the signal attenuation of the ultrasonic transducer.

[0044] Online correction: The more accurate ultrasonic flow meter 2 can be used as an "online standard" to perform long-term, dynamic correction of the instrument coefficient of the orifice plate flow meter 3 to compensate for its performance drift.

[0045] Currently, condensate pipes in coal-fired power units are generally made of No. 20 steel, which has a relatively high inner wall roughness. During operation, this can easily cause fluid disturbance near the wall surface and disrupt the fully developed velocity distribution, directly interfering with the accurate measurement of the flow meter. This embodiment uses a stainless steel condensate pipe 1 for the coal-fired power unit. With its smoother inner wall and excellent corrosion resistance, it can significantly reduce the disturbance of the pipe wall to the flow field, keeping the velocity profile stable and symmetrical throughout the entire operating range, thereby effectively improving the measurement accuracy of condensate flow rate under wide load conditions.

[0046] For the same reason, both the orifice plate flow meter 3 and the ultrasonic flow meter 2 are made of stainless steel. To ensure the accuracy of subsequent measurements, both the orifice plate flow meter 3 and the ultrasonic flow meter are calibrated after installation to ensure that their measurement accuracy under the design flow conditions is ≤0.3% and ≤0.5%, respectively. The ultrasonic flow meter 2 is further designed as a pipe-section multi-channel (at least 4 channels) ultrasonic flow meter with an accuracy class better than 0.5, thereby achieving the highest accuracy and resistance to flow field distortion.

[0047] To avoid the orifice plate on the orifice plate flowmeter 3 affecting the detection of the ultrasonic flowmeter 2, the ultrasonic flowmeter 2 is positioned upstream of the orifice plate flowmeter 3 with a spacing ≥10*DN, where DN is the inner diameter of the condensate pipe 1 of the coal-fired unit. The ultrasonic flowmeter 2 can avoid the vortices and distorted flow field generated by the orifice plate, and measure the original and stable flow velocity distribution; it is also far from the pressure pulsations, vibrations, and possible gas evolution of the orifice plate, resulting in a more reliable signal.

[0048] According to design requirements, a stainless steel rectifier 4 can also be installed downstream of the orifice plate flowmeter 3. The distance between the rectifier 4 and the orifice plate flowmeter 3 is ≥16*DN. The rectifier 4 is used to stabilize the turbulence after the orifice plate to obtain a stable differential pressure signal. However, installing the rectifier 4 will increase the flow resistance before the orifice plate flowmeter 3. If the straight pipe section of the coal-fired unit condensate pipeline 1 before the orifice plate flowmeter 3 is long enough, the rectifier 4 may not be necessary.

[0049] For the existing coal-fired power unit deaerator inlet condensate pressure (<2MPa) and temperature (<180℃), considering equipment safety and reliability, both ultrasonic flow meter 2 and orifice plate flow meter 3 are installed on the coal-fired power unit condensate pipeline 1 via flanges. The output signals of ultrasonic flow meter 2 and orifice plate flow meter 3 (typically 4-20 mA analog signals or HART / bus digital signals) should be simultaneously connected to the power plant's distributed control system.

[0050] One way to perform weighted summation in a distributed control system is as follows:

[0051] The entire condensate flow range is divided into three main zones: low load zone, high load zone, and transition zone. The thresholds (L1, L2) are determined precisely through field tests based on the specific operating characteristics of the coal-fired unit and the performance curves of the two devices (ultrasonic flow meter 2 and orifice plate flow meter 3).

[0052] (1) Low load area, flow rate < L1:

[0053] In this load range, the orifice plate flow meter 3 has the largest measurement error, while the ultrasonic flow meter 2 is within its optimal measurement range. Therefore, the final output value of the system is directly taken from the measurement value of the ultrasonic flow meter 2.

[0054] The data from orifice plate flowmeter 3 is used solely for background monitoring and rough comparison. Its main function is to determine whether it has experienced a serious malfunction (such as blockage of the pressure-conducting pipe causing the differential pressure to be zero or constant).

[0055] Switching logic: When the flow rate decreases from the transition zone and crosses the threshold L1, the system logic should smoothly transfer the measurement weight completely to the ultrasonic flow meter 2.

[0056] (2) High load area, flow rate > L2:

[0057] In this region, the condensate flow velocity is high and the Reynolds number is sufficient. The orifice plate flowmeter 3 operates under its designed optimal conditions, and its measurement values ​​are accurate, stable, and in line with industry standards. Therefore, the final output value of the system mainly adopts the measurement value of the orifice plate flowmeter 3.

[0058] The data from ultrasonic flow meter 2 is used as a high-precision benchmark to verify in real time whether there are any deviations in the measurement of orifice plate flow meter 3. This is the basis for realizing online correction of the orifice plate instrument coefficient.

[0059] Switching logic: When the flow rate increases from the transition zone and crosses the threshold L2, the system logic smoothly transfers the measurement weight to the orifice plate flow meter 3.

[0060] (3) Transition zone, L1≤flow rate≤L2:

[0061] In this region, both ultrasonic flowmeter 2 and orifice plate flowmeter 3 have a certain degree of reliability. To ensure a smooth and undisturbed final output value when switching from one region to another, a weighted summation method is used.

[0062] The final measured value F is obtained by weighted summation:

[0063] L(t) = W ultrasonic (t-1)×L ultrasonic (t) + W orifice (t-1) × L orifice (t)

[0064] In the formula, W ultrasonic W orifice The weights of ultrasonic flow meter 2 and orifice plate flow meter 3, respectively, L ultrasonic L orifice The values ​​are the measured values ​​of ultrasonic flow meter 2 and orifice plate flow meter 3, respectively, and t is the time.

[0065] If L(t-1) < L1, then W ultrasonic (t-1)=1, W orifice (t-1) = 0;

[0066] If L(t-1) > L2, then W ultrasonic (t-1)=0, W orifice (t-1) = 1;

[0067] If L1≤L(t-1)≤L2, then when L(t-1) changes from L1 to L2, W ultrasonic (t-1) shows a negative correlation in the interval (0,1), W orifice (t-1) shows a positive correlation in the interval (0,1);

[0068] Among them, W ultrasonic(t-1) + W orifice (t-1) = 1, and L1 and L2 are the first flow threshold and the second flow threshold.

[0069] Since the weights of ultrasonic flowmeter 2 and orifice plate flowmeter 3 need to be determined based on the flow rate in the current weighted summation process, and the flow rate at the current moment has not yet been accurately obtained, the flow rate at the previous moment is used to calibrate the weights.

[0070] Meanwhile, this embodiment provides another weighted summation method, using the unit load of the coal-fired power unit to calibrate the weights of the ultrasonic flowmeter 2 and the orifice plate flowmeter 3. Since the unit load at the current moment can be accurately obtained, it is sufficient to use the current unit load to calibrate the weights. Specifically, the weighted summation to obtain the final measured value F is as follows:

[0071] L(t) = W ultrasonic (t)×L ultrasonic (t) + W orifice (t) × L orifice (t)

[0072] In the formula, W ultrasonic W orifice The weights of ultrasonic flow meter 2 and orifice plate flow meter 3, respectively, L ultrasonic L orifice The values ​​are the measured values ​​of ultrasonic flow meter 2 and orifice plate flow meter 3, respectively, and t is the time.

[0073] If P(t) < P1, then W ultrasonic (t) = 1, W orifice (t) = 0;

[0074] If P(t) > P2, then W ultrasonic (t) = 0, W orifice (t) = 1;

[0075] If P1 ≤ P(t) ≤ P2, then when P(t) changes from P1 to P2, W ultrasonic (t) shows a negative correlation in the interval (0,1), W orifice (t) shows a positive correlation in the interval (0,1);

[0076] Among them, W ultrasonic (t-1) + W orifice (t-1)=1, P1 and P2 are the first load threshold and the second load threshold, and P is the unit load of the coal-fired unit.

[0077] To avoid abrupt changes at the switching point, the negative or positive correlation changes in this embodiment are either linear or non-linear smooth changes. Non-linear smooth changes include functions such as the sigmoid function. Figure 2 As shown, it can well meet the usage requirements of this embodiment.

[0078] In addition to the weighted summation method provided above, the following algorithms can also be used in other optional implementations:

[0079] (1) Kalman filter-based fusion: For systems with higher requirements, the Kalman filter algorithm can be used. This algorithm can optimally estimate two (or more) noisy measurements to obtain a more accurate and smoother estimate than any single measurement. This requires establishing a dynamic model of the system, and the algorithm is relatively complex, but it has the best effect.

[0080] (2) Neural network fusion: By collecting a large amount of measurement data and standard flow data of two flow meters under different operating conditions, a neural network model can be trained. This model can intelligently output a fusion result that is closest to the true value based on the two input measurement values.

[0081] The condensate flow measurement system proposed in this invention can be applied not only to coal-fired power units, but also to scenarios requiring high-precision flow monitoring, such as the secondary loop of nuclear power plants.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A condensate flow measurement system for a coal-fired power unit, characterized in that, The system includes a condensate pipeline for a coal-fired power unit and an ultrasonic flow meter and an orifice plate flow meter installed on the condensate pipeline. The ultrasonic flow meter is located upstream of the orifice plate flow meter. The final measurement value is obtained by weighted summation of the measurements from the ultrasonic flow meter and the orifice plate flow meter.

2. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, The orifice plate flow meter is made of stainless steel and undergoes calibration to ensure that its measurement accuracy is ≤0.3% under the design flow conditions.

3. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, The ultrasonic flow meter is a pipe-section type multi-channel ultrasonic flow meter made of stainless steel, and it is calibrated to ensure that its measurement accuracy is ≤0.5% under the design flow conditions.

4. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, The distance between the ultrasonic flow meter and the orifice plate flow meter is ≥10*DN, where DN is the inner diameter of the condensate pipe of the coal-fired unit.

5. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, The condensate pipes of the coal-fired unit are made of stainless steel.

6. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, A stainless steel rectifier is installed downstream of the orifice plate flow meter. The distance between the rectifier and the orifice plate flow meter is ≥16*DN, where DN is the inner diameter of the condensate pipe of the coal-fired unit.

7. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, Both the ultrasonic flow meter and the orifice plate flow meter are installed on the condensate pipeline of the coal-fired unit via flanges.

8. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, The weighted summation yields the final measurement value F as follows: L(t)= W ultrasonic (t-1)×L ultrasonic (t)+ W orifice (t-1)× L orifice (t) In the formula, W ultrasonic W orifice The weights of the ultrasonic flow meter and the orifice plate flow meter, respectively, L ultrasonic L orifice , respectively, are the measured values ​​from the ultrasonic flow meter and the orifice plate flow meter, where t is time; If L(t-1) < L1, then W ultrasonic (t-1) = 1, W orifice (t-1) = 0; If L(t-1) > L2, then W ultrasonic (t-1)=0, W orifice (t-1) = 1; If L1≤L(t-1)≤L2, then when L(t-1) changes from L1 to L2, W ultrasonic (t-1) shows a negative correlation in the interval (0,1), W orifice (t-1) shows a positive correlation in the interval (0,1); Among them, W ultrasonic (t-1) + W orifice (t-1) = 1, and L1 and L2 are the first flow threshold and the second flow threshold.

9. The condensate flow measurement system for coal-fired power units according to claim 1, characterized in that, The weighted summation yields the final measurement value F as follows: L(t)= W ultrasonic (t)×L ultrasonic (t)+ W orifice (t)× L orifice (t) In the formula, W ultrasonic W orifice The weights of the ultrasonic flow meter and the orifice plate flow meter, respectively, L ultrasonic L orifice , respectively, are the measured values ​​from the ultrasonic flow meter and the orifice plate flow meter, where t is time; If P(t) < P1, then W ultrasonic (t) = 1, W orifice (t) = 0; If P(t) > P2, then W ultrasonic (t) = 0, W orifice (t) = 1; If P1 ≤ P(t) ≤ P2, then when P(t) changes from P1 to P2, W ultrasonic (t) shows a negative correlation in the interval (0,1), W orifice (t) shows a positive correlation in the interval (0,1); Among them, W ultrasonic (t-1) + W orifice (t-1)=1, P1 and P2 are the first load threshold and the second load threshold, and P is the unit load of the coal-fired unit.

10. The condensate flow measurement system for coal-fired power units according to claim 8 or 9, characterized in that, The negative correlation change or the positive correlation change is either a linear change or a non-linear smooth change.

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