Device and method for measuring efficiency of driving steam turbine

Abstract

The invention discloses a measuring device and method for driving steam turbine efficiency, belongs to the field of steam turbines, and aims to solve the problem that the driving steam turbine efficiency is not easy to obtain. The device comprises a calibration unit and a measurement unit. The calibration unit is used for acquiring a dependent variable-torque proportionality coefficient k under the off-line state of the driving steam turbine; the calibration unit applies a static moment by using a chain block with a horizontal single end fixed, and a tension sensor is mounted in front of a stress application point; the measuring unit is vertically and symmetrically provided with two strain gauges on the middle section of the driving turbine output shaft; two sets of acquisition substations and button cells are symmetrically arranged in the middle section of the shaft along a shaft shoulder, the button cells provide working power sources for the acquisition substations in the same set, dependent variables measured by the strain gauges are sent to the acquisition substations in the same set in a wired mode, and the dependent variables of the two acquisition substations are both sent to an acquisition device in a wireless mode. And the collecting device sends the two paths of dependent variable input signals to the PC, the torque is obtained according to the dependent variable and the coefficient k, and then the efficiency of driving the steam turbine is obtained.

Description

Technical Field

[0001] The invention relates to a device and method for measuring the efficiency of a driving steam turbine, belonging to the field of steam turbines. Background Art

[0002] A steam turbine is an energy conversion device that uses the kinetic energy generated by the force of steam or other gaseous fluid on the rotor impeller to complete work. Steam turbine efficiency refers to the efficiency of energy conversion during the operation of the steam turbine. The efficiency of the steam turbine is an important indicator to measure its performance. It is relatively easy to measure the efficiency or heat consumption of steam turbines used in power plants. When the steam turbine is connected to a generator, its output power is relatively easy to obtain. However, compared with driving steam turbines, see Figure 1 As shown, no matter it is a condensing or back-pressure steam turbine, it is usually connected to a reducer and a driven device, and the output power of the driving steam turbine cannot be directly obtained. Instead, the overall efficiency of the system is often obtained, and it is difficult to accurately obtain indicators such as the efficiency and heat consumption of the steam turbine, which is disadvantageous for verifying and optimizing the design. Summary of the invention

[0003] In view of the problem that the efficiency of a driving steam turbine is not easy to obtain, the present invention provides a device and method for measuring the efficiency of a driving steam turbine.

[0004] In one aspect, the present invention provides a device for measuring the efficiency of a driving steam turbine, comprising a calibration unit and a measuring unit; the calibration unit is used to load a known static torque on the shaft end of the driving steam turbine output shaft when the driving steam turbine is offline, and to obtain a strain amount by using the measuring unit, thereby obtaining a strain amount-torque proportionality coefficient k; the measuring unit is used to obtain a strain amount of the driving steam turbine output shaft caused by an external force;

[0005] The calibration unit includes a tension sensor, a fall chain and a traveling crane. The traveling crane fixes the shaft end of the output shaft of the driving steam turbine through the fall chain, and uses the fall chain fixed at a single end horizontally to realize the application of static torque, and the tension sensor is installed in front of the force application point.

[0006] The measuring unit includes strain gauges, collection substations, button batteries, collection devices and PCs; two strain gauges are symmetrically arranged in the upper and lower middle section of the output shaft of the driving steam turbine; two groups of collection substations and button batteries are symmetrically arranged along the shaft shoulder in the middle section of the shaft, and the button batteries provide working power for the collection substations in the same group. The strain measured by the strain gauge is sent to the collection substations in the same group in a wired manner, and the strains of the two collection substations are sent to the collection device in a wireless manner. The collection device sends two channels of strain input signals to the PC, obtains the torque according to the strain and the strain-torque proportional coefficient k, and then obtains the efficiency of the driving steam turbine.

[0007] Preferably, the collection substation and the button battery are of equal weight and are symmetrically distributed on the shoulder.

[0008] Preferably, the strain gauge is of model BHF1K.

[0009] Preferably, Bluetooth transmission is used between the collection substation and the collector.

[0010] Preferably, the strain gauge and the acquisition substation are connected by a Φ0.15mm high-temperature multi-core silver-plated wire.

[0011] Another aspect of the present invention provides a method for measuring the efficiency of a driving steam turbine. The method is implemented based on the device for measuring the efficiency of the driving steam turbine. The method comprises the following steps:

[0012] S1. Calibration steps:

[0013] A known static torque is applied to the output shaft end of the driving steam turbine. The strain caused by the output shaft deformation is sensed by two strain gauges, and the strain-torque proportional coefficient k is obtained:

[0014] Where T is the measured torque, here the known static torque of the load is used as the measured torque, and σ is the strain;

[0015] S2. Under the normal operation of the driving steam turbine, the strain gauge is used to measure the two strain quantities, and the average value is taken as the strain quantity caused by the deformation of the output shaft of the driving steam turbine;

[0016] S3. Obtain the output power P of the driving steam turbine:

[0017] P = Tω = kσω, where ω is the angular velocity of rotation. Here, the torque of the driving steam turbine under normal operating conditions is used as the measured torque T;

[0018] S4. Obtain the driving steam turbine efficiency η:

[0019]

[0020] In the formula, h in is the inlet enthalpy, which is obtained by looking up the table based on the driving turbine inlet pressure and inlet steam temperature;

[0021] h s-out is the outlet isentropic enthalpy value, which is obtained by looking up the table according to the outlet pressure and inlet entropy value of the driving steam turbine, wherein the inlet entropy value is obtained by looking up the table according to the inlet pressure and inlet steam temperature of the driving steam turbine.

[0022] Preferably, the zero point is adjusted before the calibration step begins, so that the strain is 0 when zero static moment is input.

[0023] Beneficial effects of the invention: The invention provides a measurement method for calculating the efficiency of a driving steam turbine, and uses the corresponding relationship between strain, torque and shaft power to obtain the output shaft power of the driving steam turbine and the efficiency of the steam turbine. The method is simple to implement, easy to operate, does not affect the operation of the steam turbine itself, and is suitable for engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a block diagram of the operating principle of the driving steam turbine;

[0025] Figure 2 It is a principle block diagram of a method for measuring the efficiency of a driving steam turbine according to the present invention;

[0026] Figure 3 This is the schematic diagram of static calibration. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0030] Specific implementation method 1: The following is combined Figures 1 to 3 The present embodiment is described. The present embodiment describes a method for measuring the efficiency of a driving steam turbine, comprising a calibration unit and a measuring unit. The calibration unit is used to load a known static torque on the shaft end of the driving steam turbine output shaft when the driving steam turbine is offline, and to obtain the strain amount by using the measuring unit, thereby obtaining the strain amount-torque proportionality coefficient k. The measuring unit is used to obtain the strain amount of the driving steam turbine output shaft caused by external force.

[0031] The calibration unit includes a tension sensor, a fall chain and a traveling crane. The traveling crane fixes the shaft end of the output shaft of the driving steam turbine through the fall chain, and uses the fall chain fixed at a single end horizontally to realize the application of static torque, and the tension sensor is installed in front of the force application point.

[0032] See also Figure 2As shown, the measurement unit includes strain gauges, acquisition substations, button batteries, acquisition collectors and PCs; two strain gauges are symmetrically arranged in the middle section of the output shaft of the driving steam turbine; two groups of acquisition substations and button batteries are symmetrically arranged along the shaft shoulder in the middle section of the shaft, and the button batteries provide working power for the acquisition substations in the same group. The strain measured by the strain gauge is sent to the acquisition substations in the same group by wire, and the strains of the two acquisition substations are sent to the acquisition collectors by wireless. The acquisition collectors send two strain input signals to the PC, and obtain the torque according to the strain and the strain-torque ratio coefficient k, and then obtain the efficiency of the driving steam turbine. The acquisition substations and button batteries are of equal weight and symmetrically distributed on the shaft shoulder.

[0033] Since the direct stress / strain measurement method is used in the measurement, in order to obtain the measurement data that meets the actual needs to the maximum extent, the strain gauge uses the HA type half-bridge with R0=1000Ω, model: BHF1K, with high accuracy (0.03%) and sensitivity (2.15), to improve the measurement sensitivity and take into account the measurement range. A strain gauge is set up on the upper and lower parts of the middle section of the output shaft, and components produced in the same batch are used to further reduce the measurement error caused by factors such as ambient temperature. The operating temperature range of the measuring element is: -30~80℃.

[0034] In order to reduce the influence of uneven stress at the shaft end, the shaft section is very short. When arranging the components on site, they should be arranged at 1 / 2 of the exposed part of the output shaft to obtain higher measurement sensitivity. The temperature of the shaft should not be greater than 45°C when the strain gauge and the detection component are installed, otherwise cooling measures should be taken in advance, which can directly lead to installation failure and the system cannot be used.

[0035] Static calibration is used before measurement. Since the measuring point is too short from the shaft shoulder, it has poor adaptability to the measuring range and brings uncertainty to the calibration. Therefore, a longer calibration time may be required.

[0036] After the above positions are selected, the measuring components will be laid to the selected positions 24 hours in advance according to the process requirements of the "measurement component layout plan". Because the installation position is not conducive to work, the installation of the components will take 2 days. About 24 hours after installation, when the protective layer reaches the strength of use, the calibration work can begin.

[0037] Signal acquisition:

[0038] Bluetooth transmission is used between the collection substation and the collector.

[0039] The Bluetooth acquisition substation adopts BLE micro-power consumption Bluetooth transmission technology, with the core being the nRF52xx series MPU, using the ARMCortex M4 core, supporting the latest 5.0 Bluetooth protocol, and a theoretical transmission distance of 100 meters. In order to reduce errors in the transmission (amplification, processing, interference, etc.) process, a high-stability instrument-grade differential amplifier is added, and then a differential ADC acquisition mode is adopted to eliminate the common-mode interference caused by field leads to the greatest extent, thereby improving the measurement accuracy of the system.

[0040] It is powered by disposable batteries. In order to maximize the system collection and usage time, the MPU adopts a sleep and intermittent wake-up working mode. When it receives a timed wake-up command, it immediately powers the sensor and starts collection. The collection results are then checked for validity and anti-interference processing. The collection substation transmits the processing results to the collector via Bluetooth wireless broadcast.

[0041] In order to prevent accidental signal loss caused by the acquisition substation rotating with the main shaft, "multiple sampling" processing and redundant transmission backup are used for both acquisition and transmission to minimize the impact of "rotation" on the continuity of measurement. Of course, if the speed is too high, there may always be some signal loss, which can be compensated by data analysis.

[0042] The collector is the BLE master station. When it receives the broadcast result from the acquisition substation, it performs necessary validity judgment, performs simple post-processing, and converts it into voltage measurement results. It is sent directly to the USB port of the PC through the high-speed communication port of the MPU to complete the acquisition process. In order to maximize "energy saving", the acquisition substation and the collector do not process the signal too much and reduce the communication time. The data received by the PC needs to be processed by simple range and engineering quantity conversion on the PC side, and the necessary data display and recording are completed for later data analysis and processing.

[0043] Layout of electronic components:

[0044] The strain gauge and the acquisition substation are connected by a Φ0.15mm high-temperature multi-core silver-plated wire. The acquisition substation is arranged in the middle section of the exposed part of the shaft. Since the mass of a single acquisition substation is about 8g, and the total mass of the binder is less than 10g, and the battery and the acquisition substation are arranged radially symmetrically along the shaft shoulder, it is expected that the dynamic balance of the shaft will be less affected. The battery uses a high-capacity disposable lithium battery with a mass of 10g. The two groups of acquisition substations and batteries are evenly distributed along the circumference and are symmetrical in pairs.

[0045] The collector is not placed on the output shaft, but at a certain distance from the output shaft, so it does not affect the dynamic balance of the shaft system. The collector and the PC are connected by a 1.5-meter communication line. The collector itself has a 1.5-meter suction cup antenna.

[0046] Specific implementation method 2: The following is combined Figures 1 to 3 This embodiment is described. The embodiment described in this embodiment is a method for measuring the efficiency of a driving steam turbine. The method is implemented based on the measuring device for the efficiency of the driving steam turbine. The measuring method includes the following steps:

[0047] S1. Calibration steps:

[0048] A known static torque is applied to the output shaft end of the driving steam turbine. The strain caused by the output shaft deformation is sensed by two strain gauges, and the strain-torque proportional coefficient k is obtained:

[0049] Where T is the measured torque, here the known static torque of the load is used as the measured torque, and σ is the strain;

[0050] S2. Under the normal operation of the driving steam turbine, the strain gauge is used to measure the two strain quantities, and the average value is taken as the strain quantity caused by the deformation of the output shaft of the driving steam turbine;

[0051] S3. Obtain the output power P of the driving steam turbine:

[0052] P = Tω = kσω, where ω is the angular velocity of rotation. Here, the torque of the driving steam turbine under normal operating conditions is used as the measured torque T;

[0053] S4. Obtain the driving steam turbine efficiency η:

[0054]

[0055] In the formula, h in is the inlet enthalpy, which is obtained by looking up the table based on the driving turbine inlet pressure and inlet steam temperature;

[0056] h s-out is the outlet isentropic enthalpy value, which is obtained by looking up the table according to the outlet pressure and inlet entropy value of the driving steam turbine, wherein the inlet entropy value is obtained by looking up the table according to the inlet pressure and inlet steam temperature of the driving steam turbine.

[0057] Before the calibration procedure begins, adjust the zero point so that the strain is 0 when zero static moment is input.

[0058] Here is a specific example:

[0059] The fall chain fixes (locks) the shaft end, and the force can be applied by using the horizontal single-end fixed "fall chain", and a tension sensor is installed in front of the force application point.

[0060] Adjust the zero point so that when the input is zero, the strain measured by the strain gauge is 0.

[0061] The force radius is the output shaft radius, and the force size is obtained by the tension sensor.

[0062] The static moment is loaded by using a fall chain. Specifically, the force is measured by a tension sensor as F=2000.00 kg, and the force radius is r=1435 / 2=717.5 mm.

[0063] Then, the loading static moment is T = Fr = 0.7175 × 2000 × 9.8 = 14063 Nm = 14.063 kNm.

[0064] At this time, the strain value obtained by the strain gauge is 7.29Mv (expressed in voltage).

[0065] Then the strain-torque ratio coefficient k = 14.063 kNm / 7.29 = 1.92908 kNm / mv

[0066] Then, change the driving steam turbine to enter normal operation.

[0067] The strain σ is measured in real time, and the measured torque is T = 1.92908σ;

[0068] Then the output shaft power of the driving steam turbine is P = 1.92908σω;

[0069] Finally, according to

[0070]

[0071] Get the driving turbine efficiency.

[0072] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A device for measuring the efficiency of a driving steam turbine, characterized in that: It includes a calibration unit and a measuring unit; the calibration unit is used to load a known static torque on the shaft end of the driving steam turbine output shaft when the driving steam turbine is offline, and use the measuring unit to obtain the strain, and then obtain the strain-torque proportional coefficient k; the measuring unit is used to obtain the strain of the driving steam turbine output shaft caused by external force; The calibration unit includes a tension sensor, a fall chain and a traveling crane. The traveling crane fixes the shaft end of the output shaft of the driving steam turbine through the fall chain, and uses the fall chain fixed at a single end horizontally to realize the application of static torque, and the tension sensor is installed in front of the force application point. The measuring unit includes strain gauges, collection substations, button batteries, collection devices and PCs; two strain gauges are symmetrically arranged in the upper and lower middle section of the output shaft of the driving steam turbine; two groups of collection substations and button batteries are symmetrically arranged along the shaft shoulder in the middle section of the shaft, and the button batteries provide working power for the collection substations in the same group. The strain measured by the strain gauge is sent to the collection substations in the same group in a wired manner, and the strains of the two collection substations are sent to the collection device in a wireless manner. The collection device sends two channels of strain input signals to the PC, obtains the torque according to the strain and the strain-torque proportional coefficient k, and then obtains the efficiency of the driving steam turbine.

2. The device for measuring the efficiency of a driving steam turbine according to claim 1, characterized in that: The collection substation and button battery are of equal weight and are symmetrically distributed on the shaft shoulder.

3. The device for measuring the efficiency of a driving steam turbine according to claim 2, characterized in that: The model of the strain gauge is BHF1K.

4. The device for measuring the efficiency of a driving steam turbine according to claim 1, characterized in that: Bluetooth transmission is used between the collection substation and the collector.

5. The device for measuring the efficiency of a driving steam turbine according to claim 1, characterized in that: The strain gauge and the acquisition substation are connected by a Φ0.15mm high-temperature multi-core silver-plated wire.

6. A method for measuring the efficiency of a driving steam turbine, the method being implemented based on the device for measuring the efficiency of a driving steam turbine according to any one of claims 1 to 5, characterized in that: The measurement method includes the following steps: S1. Calibration steps: A known static torque is applied to the output shaft end of the driving steam turbine. The strain caused by the output shaft deformation is sensed by two strain gauges, and the strain-torque proportional coefficient k is obtained: k= T , where T is the measured torque, here the known static torque of the load is used as the measured torque, and σ is the strain; σ S2. Under the normal operation of the driving steam turbine, the strain gauge is used to measure the two strain quantities, and the average value is taken as the strain quantity caused by the deformation of the output shaft of the driving steam turbine; S3. Obtain the output power P of the driving steam turbine: P = Tω = kσω, where ω is the angular velocity of rotation. Here, the torque of the driving steam turbine under normal operating conditions is used as the measured torque T; S4. Obtain the driving steam turbine efficiency η: In the formula, h in is the inlet enthalpy, which is obtained by looking up the table based on the driving turbine inlet pressure and inlet steam temperature; h s-out is the outlet isentropic enthalpy value, which is obtained by looking up the table according to the outlet pressure and inlet entropy value of the driving steam turbine, wherein the inlet entropy value is obtained by looking up the table according to the inlet pressure and inlet steam temperature of the driving steam turbine.

7. A method for measuring the efficiency of a driving steam turbine according to claim 6, characterized in that: Before the calibration procedure begins, adjust the zero point so that the strain is 0 when zero static moment is input.

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